Battery chargers, inverters, engine generators-parameters

[booster]

We are starting to get some information and data from our just (mostly) completed, charging/power/inverter upgrades. There was a lot of discussion previously as to the different chargers, charging parameters, engine generators, inverters, etc and hopefully now we will be able to get a better idea of what proves out, and what doesn't. This all started because of our Roadtrek's inverter/charger that would not get the batteries fully charged. The nuts and bolts of the changes are in another discussion, this is more function related.

What we have now and are trying to learn how to use.

Blue Sea 7522, 40amp, 3 bank, charger that allows lots of customization by bank, including absorption times, minimum amps for absorption, and general parameters like absorption and float voltages, temp correction, etc. This charger is capable of getting to the recommended higher voltages that Trojan wants for their wet cells.

Blue Sea ACR charge relays that are able to isolate the battery banks when on the charger, and combine the banks when on the engine generator.

1500 watt Samlex pure sine wave inverter.

Xantrex standalone transfer switch for inverter circuits switching to shore power or inverter.

200 watts of solar with a Morningstar MPPT controller that is programmable for some parameters and capable of the higher voltages for Trojan.

160 amp capable wiring from the van engine to the batteries and inverter. 145 amp stock alternator that may need to be bigger as we will need about 100 amps at idle.

One thing jumped out plainly right away when I did the first, temporarily wired, charging test on two battery banks (260 and 115AH). I programmed in the suggested 14.8 absorption voltage, 1% of AH capacity minimum amperage for absorption, and fairly long min and max absorption times. It should have run through bulk and then stayed in absorption until it got down to the min amps or max time. What happened was that it never got near the min amps, and was over double what was expected on both banks. The batteries were very warm to the touch and gassing enough to dampen the battery tops. This would not be acceptable in everyday use, IMO. It was pretty discouraging. I turned everything off and let it sit overnight. The batteries checked full in the morning, so I started the charger again to see what would happen. It went right to absorption after a very short bulk, and in about 15 minutes was very near min amps. The only thing that was different was the temp of the batteries, which had cooled off. I did not have the temp probe hooked up for the first test, as the room was very near the 77*F that they call normal, which I think is the problem. I looked up the temp correction specs, which are much larger than I expected at .168 volt for every 10*F. The batteries had to be at 105*F or more, so that is 30* high. The voltage would have been reduced by .168 X 3 or about .5 volt if the correction had been in. At that temp the charger should have been giving it 14.3 volts not 14.8, so that would explain the gassing, and heat, I think.

Bottom line from this, to me, would be that you should not increase the voltage to the Trojan suggested 14.8 volts unless you have very good temp correction in place. You get a kind of thermal runaway that makes itself worse and worse as it charges without the temp correction. To put it all in perspective, it only takes about 25*F temp difference, to have the .4 volt difference in voltage desired between what most chargers run at (14.4v) and what Trojan recommends (14.8 volts) both rated at 77*F. You can pretty easily almost double the 25* variation in a single day of camping, so no matter where you start with the voltage, you are bound to be over or under voltage most of the time. Handybob made a big deal of temp correction in his articles, but only talked about the need to increase voltage in the cold. While that is important to get the batteries full, the reduction when it is hot appears to be very important in water use, mess, and probably battery life.

I have run another, brief, test starting at 14.6 volts and with the temp correction working from a battery sensor. It charged slightly slower, but still got the batteries totally full, and with much less gassing. The batteries only heated up 5*F. The minimum amps came in very close to the 1% of AH, but to the higher side. Trojan states 1-3% which is probably because it changes a lot with charging voltage. I think the only way to know how to set it is to run the charger until the amps quit dropping and go with that.

The charger does as I was told by Blue Sea, in that is always goes through a charge cycle when plugged in, regardless of if the batteries are full or not, or if they show high voltage from surface charge, or the solar. The Tripplite would not do this and often blew right into float, when the batteries were not near full. You plug in, it goes through bulk very quickly if the batteries are near full, and then runs until the min amps is reached and min absorption time met. It then goes into prefloat or float, depending on the situation with the other banks. It is still unclear how solar output amps will react with the charger. It will run the min absorption time for sure, but if the solar is putting out well, it may see minimum amps early. This is the reason I added a solar off switch to the system, so we could shut off the solar when on shore power easily, if necessary.

One concern I had was what would happen if the charger was in float, and then you turned on a load in the van that was bigger than the minimum for absorption setting. Based on what I have seen so far, it goes into what it calls bulk charge, but only if there is some time left in the max absorption time for that bank. It doesn't, however, seem to go to bulk voltage, staying at the float voltage the whole time. It does add time to absorption timer, however. I am sure I will have to get a hold of one of the engineers at Blue Sea to find out exactly how the timers work, as the tech I talked to didn't really have a full understanding of it, and a lot of it makes little sense so far. The good is that it doesn't go back into high voltage on top of full batteries just because a load comes on, or at least that is what it looks like now.

The ACRs did what they were claimed to do. They isolated the two coach banks and the starter battery into 3 separate banks when on the charger, with each charging to its programmed parameters. To simulate what would happen when running of the van alternator, I hooked up a small charger that runs at 14.4 volts on the starter battery. The OEM separator closed as it normally would, and the ACRs combined all 3 banks together so they would all get charged when driving.

I ran the 1500 watt inverter off of just the coach batteries (375AH of wet cell deep cycle) and tried the Dometic microwave. It started fine and boiled water in cup in less than 4 minutes. It did drop the voltage to 11.5 volts and pulled 106 amps on the Trimetric meter. I will be very interested to see how the voltage holds when the engine is running and helping the batteries. If the voltage gets into the 13.5 volt range, the amps should go a closer to 90 amps. That test will determine if we need a bit more alternator or not, as we would like to be able to run the van and have minimal draw from the batteries. The standalone transfer switch worked fine for switching the inverter circuits to shore power and back again.

We still have a lot of finish work before we can go off camping and get better real world information. I am sure we will have a bunch of data to collect from different settings of the charger and the solar to look at and try to decide what the best combination is.

IMO, the most important thing I have seen so far is the importance of the temp correction. Without it, all the other settings are close to irrelevant. Second is finding a charger that always goes through a full charge cycle when plugged in, and ends based on minimum time and minimum amps.

As we sit right now, we have totally full batteries. The only times in the past we had them totally full were after equalizing, so we have already made very large progress since it was done as a normal charging.

All and all, I think it going to turn out less complicated than I feared to determine the right settings that don't need constant attention.

[markopolo]

I've read how important battery temperature monitoring is for accurate battery charging but your test results really demonstrate that it is critical when you get into chargers that have higher than typical output voltages.

It will be interesting to see how your Blue Sea unit handles the input into the system from solar. I've wondered if, on some setups, the solar input tricks the primary charger to switch from bulk or absorption mode prematurely.

I think it is good that it doesn't go into bulk voltage if a load is applied during absorption mode. I suspect that is an issue with some inverter / chargers where a short duration high amp load like a pump can trick them into going to bulk mode when it is not needed.

I'm interested to know how well your alternator handles microwave oven amp draw (what voltage does it drop to). I have a new alternator to install this Spring and am hoping for less voltage drop too. I think your setup allows you to combine all on-board batteries for the task if wanted.

It does look as though your new setup won't need much attention from you at all. I get a real sense of satisfaction from a well designed high tech system that just works as expected with little or no operator input required.

[booster]

The temp correction thing kind of explains how the chargers all seem to have wound up at 14.4 volts for absorption and 13.5 for float, when the "ideal" charging parameters are 14.8v and 13.2v. The critical part is that the "ideal" parameters are also at "ideal" temperature of 77 degrees F. At 14.4v baseline, with no temp correction, you would have about 30 degrees F of temp increase before you were badly high on voltage (30 degrees is about .5 volt of desired correction) so you would have the equivalent of 14.9 volts if the battery was at 107 degrees F. On the low end you could see 50 degrees of variation from the ideal 77 degrees which would give you about .8 volts of correction if you had it. So at 27 degrees, you would have the equivalent of 12.7 volts float voltage, which is barely enough to break even on a full battery. When I first started reading up on the charge voltages, getting full batteries, etc, I couldn't figure out how the manufacturers of chargers could be so uninformed on charging profiles, but it now looks to me like they did a reasonable job of it because they are dealing with no temperature correction. Having no temp correction probably also makes it almost impossible to have a charger that looks at ending absorption amps, even if you can program it in. With the huge variations of charge voltage from "ideal" at any given temperature (1.3 volts of variation at 80 degree range), your ending amps would be all over the map depending on the temperature. I would think that similar issues would be seen with the absorption times, also, as having higher or lower charge voltage will change the amount of amps going in and change recharge time. From what I have seen so far, I don't think anybody can really make a genuine "smart" charger without the temp correction, ending amps, and variable absorption times. There are just too many uncontrollable things going on to be able to do a decent job of charging the batteries. It would also help explain the huge variance in how well folks' battery life varies. Folks in hot climates are going to shorten their battery life from too high voltages, and those in cold climates are going to shorten the life do to low charge voltage. I do think the hot folks will do better, though, as long as they keep up with watering. AGMs would be more of an issue in the heat, I think.

My gut feel is that the solar voltage will not be a huge issue with the Blue Sea, but the amperage will be, because it will see minimum charge amps too soon. I would not be surprised that for the best battery filling when plugged in, we would need to turn off the solar, but we still need to determine that. The solar turns off now easily with one of the toggle switches on the panel, right above the selector switch.

I am getting all the front wiring tied back so I can put the aircleaner and fuse box cover back on and run the van to see how the alternator helps the voltage. Need to finish the taxes, so it will be a day or two I did talk to the guys that make the monster Chevy alternators, to find out what speed their alternators are rated at, and which regulator they use. They don't list any of that on their website. They use the normal 14.8 volt regulator, that is what we have and will run at about 14.4v going down the road, so that is OK. They rate their alternators at 800rpm and 3 to 1 ratio for a 2400 alternator speed. We idle at about 575 rpm and look to have about 3.5 ratio (very hard to calculate because you don't know the pitch diameter of the pulleys-wish I could get at it to count teeth on both pulleys), so we would be slower than the 2400 rpm by about 20%, which would severely drop the idle output, per them. I put a piece of reflective tape on the alternator pulley, so I can check the actual rpm of it once I get running again.

[booster]

I have been trying to collect as much data as possible, and while the tests are running, trying to clean up the loose ends on install end of it.

I know Marco is very interested in the microwave with the motor running tests, and today I got things back together far enough to run the van and get some information. From the previous tests, I know the microwave runs off the 1500 watt inverter and batteries OK, dropping voltage to 11.5v and pulling about 108 amps. That is about 1250 watts of power to the microwave, and from what I have seen that should stay pretty constant through the inverter, so if I can get higher voltage, it will pull less amps. I also have a piece of reflective tape on the alternator so I can get the actual alternator speed.

Idle speed on the van is about 545-550rpm, which is mighty low. The alternator is only spinning at 1800rpm at idle, and all the high output ones I have looked at are rated at 2400rpm.

I had both coach banks of batteries full and connected, engine of the van running, inverter on. Microwave started very well, inverter made a little less noise than when on batteries alone when the microwave was turned on. Voltage at the inverter and batteries was about 13.2 volts, a definite improvement. The amperage out of the batteries was at about 20 amps, but bounced a bit. So the microwave is not totally running off the engine, but mostly is, as the 1250 watts would be about 95 amps at 13.2 volts.. The batteries were also full up on this test, or they couldn't have contributed at that high a voltage. I think that if they would lower, it would run at a voltage about the same as if it had just a 20 amp load running, which drops us about .2-.3 volts.

Our alternator, which allegedly had an OEM setpoint voltage regulator put back in late last fall, was only running at about 14.0 volts, so I need to find out what is up with that as it should be about 14.4 volts. If it turns out it is the wrong one, it will probably be a good excuse to get a bigger alternator. It is also very livable this way.

[markopolo]

13.2v at idle with the microwave oven running is really good You now have a second, much quieter, generator in in the van.

Was that at 545-550 engine rpm? As you've noted, most of the high amp alternators out there won't output high amps at low rpms. Your results makes me think the stock GM alternators are a pretty good choice.

1800 rpm at the alternator shaft is lower than mine (I think). I don't have tools to measure it but my calculations indicate my van should have 2340 alternator shaft rpm at 624 engine idle rpm. ( 7.5" crankshaft pulley / 2" alternator pulley = 3.75 ratio x 624 rpm = 2340 alternator shaft rpm)

Your results are much better than my testing: 12.9 volts microwave running, engine running, combined engine and house battery banks (4 batteries). 12.3 volts microwave running, engine running, engine batteries only (2 batteries). Fingers crossed that my to-be-installed new alternator gets close to or meets your results. I might have to upgrade some wiring.

[eric1514]

Excuse my ignorance here, but I would think dropping battery voltage to 11.5 would be fatal. I guess not.

[booster]

Originally Posted by eric1514

Excuse my ignorance here, but I would think dropping battery voltage to 11.5 would be fatal. I guess not.

I too would think it would be fatal, if the batteries were actually discharged to 11.5 volts, but in this case it is just the very high current levels make is so the batteries can't deliver the power fast enough to maintain voltage to the inverter, so it drops. Shortly after stopping the current drain, the batteries are back at their normal voltage, but down a little bit do to the amp-hours used out of them. The voltage drop is one of the big reasons we are testing how well the van engine alternator does in helping the batteries run the microwave.

[booster]

The replacement charger got here late yesterday afternoon. Only took 20 minutes to swap out, so happy about that. I had planned on getting the van off the stands today and outside to see how the solar meshed with the rest of the changes, but it is snowing like crazy here. We have about 3+ on the ground and more coming. Northern Minnesota may get 10-16 inches, they are saying. ugggg.

The batteries were nearly full anyway, so I have been running some cycles to see what the actual ending amps should be for each of the batteries. Currently, I am leaning toward running the charger at 14.6 volts absorption, 13.2 float. If we can get the GC2 batteries full in an overnight cycle that way, we would be OK with that, as if we are plugged in it is always overnight. It also cuts the two 12 volt batteries a bit of slack, as they get seem to prefer the lower voltage and remain cooler, and it will keep the voltage from going much over 15.0 when it is cold out.

The ending amps is quite dependent on the absorption voltage, which I guess makes a lot of sense. The battery charger says use 1%, but test to see what it actually comes out,Trojan says 1-3%. So far, at 14.6 volts, it appears that the GC2 batteries will be at about .8%, the SCS200 Trojan 12v will be at about 2.5% and the Costco marine starting battery at about 2%, which also includes some to run the separator. The SCS200 is nearly 5 years old, so that may be part of it, but I think it is also a slightly different style (closer to marine starting) than the GC2 batteries. It gets to nearly 1300 specific gravity, compared to just under 1280 for the GC2s, so something has to be different.

I am hoping the 14.6 volts works well, so I can have the solar set at 14.8v. That way the solar won't be tricked into going into float in the morning before we leave a site if plugged in. If it did get tricked into float, my understanding is that it would stay in float until the voltage dropped under something like 12.6 volts, so it would stay in float all day, when we might need a bit of charge, or at 14.8 a mini equalize.

The big learning point for me so far has been how difficult it would be for a one size fits all battery charger to adequately use an ending amp parameter. Even if you could program battery bank size, you would not be accurate enough for it to work very well, and you would have to have temperature correction besides, to even have a chance, as current changes so much with battery temp. That is too bad, because it looks like the ending amps is going to turn out to be the most consistent, and accurate, method of always getting the batteries full.

[booster]

The new charger is working fine, so I ran another discharge/charge cycle at 14.6 volts, after running a bunch of short cycles on the full batteries to determine the actual ending amps at 14.6 volts. There is absolutely no question that the ending amps is very dependent on the absorption voltage, so all the rules of thumb that are given, including by Trojan, are at best guidelines. Trojan says 1-3%, but even at 14.6 votls we are at about .07% on the GC2 batteries. The SCS200 12 volt battery ending is closer to 2%. The SCS200 also pulls higher beginning and ending amps, but less in between (for it's size) than the GC2 batteries do. It also finishes much quicker, so it sits in "prefloat" (14.2 volts) quite a while when already full. I intentionally stopped the absorption charge to the SCS200 a bit early, and got it to prefloat before it was totally full (1270 specific gravity range), and the 3+ hours of 14.2 volts in prefloat finished it off well, and made for less gassing all the way around with it. All that was required to do it was to increase the ending amps by 1.5 amps. It also puts more of the charger capacity to the still charging GC2 batteries. It looks like a good way to run it so far. At 14.6, and a shallow discharge all the batteries got completely full, but I still need to test it going deeper discharge, which is a much longer test to run.

I got the van off the stands and outside today. It was filthy from woodworking sawdust in the shop over the winter, so I just hosed it off (too cold and windy to wash, I am wussie), including the solar panels. It is a very cloudy day, but it was able to do 6.4 amps and 13.4 volts (11 am), tested with load and very little going into the batteries. With it this cloudy, we will take that, as it is over double what the running amps of the frig are. We should be able to break even on the frig easily over a day as it only uses between 17 and about 40 AH per day, and that is the only load we can't really control much. With only the batteries online, it held 14.6 volts, so it would be able to top them fully, it appeared, even if cloudy. Al the wiring changes really don't seem to have changed anything in how the solar works.

Not terribly unexpected, but is obvious that the "smarter" all these things are, the less likely they are to play well together. I ran a quick test with the charger getting plugged in while the solar was running, on relatively full batteries, and as expected, the amps from the solar reduced the amps from the charger, making it hit ending amps much sooner than it normally would have, and before the batteries might be full. This would mess up the accuracy of the ending amps which is the primary test of full batteries. I still need to test what the solar will do when we come off of a night of being on shore power with charger running in the morning. The solar is set .2 volts higher on absorption than the charger, so we are hoping it won't go into float, because if it does go into float, the battery voltage has to drop below something like 12.7 for it to start a new charge cycle, I think. Similar might happen off the van alternator. Once we find out what the solar does, we hope to be able to get it to do what we want, which includes giving the batteries a shot of 14.8 volts to keep them fresh and out of the need for an equalization. I do have shut off switch for the solar, so I am hoping that would make it initialize fresh when turned on after being off a while. We will see.

The ending amp conflict with the charger and solar is no big deal. If we are in a spot where we absolutely need the batteries to be full, and are charging off shore power during the day, we can just switch off the solar before the charger gets to ending amps. That is very simple, and if you forget, there is nearly no downside, and no hazard to anything.

The goal on the solar is to run the frig during the day, and recover enough into the batteries to cover the night running of the frig. Anything beyond that is gravy for us, and we should have quite a bit of gravy if it is sunny. It will do a better job of filling the batteries if it is at 14.8 volts than if it has been tricked into float at 13.2 volts, so we need to figure that out yet. The solar is pretty low output at 12ish amps at 14.8 volts, and it only does that during the peak of the day, so it isn't really all that capable of grossly overcharging, boiling, or overheating the batteries. That would make it so we could theoretically up the float voltage to a range that would better keep the batteries topped off than the 13.2 would, maybe 14.1 volts or so, without much risk of problems.

From all I have seen so far, there really couldn't be an off the shelf setup that could do this stuff without being very programmable, and it would have to control everything, not just one part of it. In reality, there really should be some form of programmable controller that would look at the battery voltages, solar outputs, alternator output, usage, etc to make decisions on how the charger, solar, alternator should be connected and set. When the e-trek first came out, they touted their very sophisticated charging system control, and I thought that's what they had, but from what we hear now, that is probably not the case. The technology may well exist in the high end yacht and boating industry, though. They use shore power, generator, wind, solar, engine alternators, all at various times. They also have multiple battery banks, electric bow thrusters, and who knows what else to deal with. I seriously doubt that the folks that can afford that kind of system and boat want to have to worry or set anything.

The high output alternator should be here in 2-3 weeks (hopefully more on time than the charger was ) which should make it so we would not use anything out of the batteries if we run the microwave off the inverter, with the van running. Supposedly a drop in.

[markopolo]

I've suspected that some solar installs could trick the charger into quitting charging too early. As you say it would be very challenging to make everything place nice together. An automatic solution would be using something similar to an automatic transfer switch that shuts off the solar panel output when it senses that you are plugged into grid power.

It's great that you got the replacement charger in without much effort. You made it easily removable and that foresight paid dividends already

[booster]

Originally Posted by markopolo

I've suspected that some solar installs could trick the charger into quitting charging too early. An automatic solution would be using something similar to an automatic transfer switch that shuts off the solar panel output when it senses that you are plugged into grid power.

I think your suspicions are proving out to be correct, and I would bet that most solar systems are messing with other things. Folks like Handybob, who are nearly completely solar wouldn't see the issue as much as someone who has solar and uses shore power semi-regularly. Of the limited number of chargers I have personally seen, I would say the Tripplite and Xantrex would not go into absorption mode and go right to, and stay in, float. The Ctek would run a complete cycle as it always goes into all the steps, based on timers, it appears, but they are tiny and not suited for what we need. The Blue Sea would run a full cycle through absorption, but would not stay in aborption as long as it should because the solar would mess up the ending amps and take it to float. I am glad that I added an on/off switch to the solar so I can turn it off when we go on shore power, and as you say, it could be automated pretty easily with a relay that turned off the solar when on shore power or generator (110 volt coil relay). By the same issue, if the shore charger is on when the sun comes up, it seems to be able to put the solar into float for the whole day, so it is a two way issue.

I haven't really understood, and still don't, the charge profile that it appears that Progressive Dynamics uses. I think it is always 4 hours at 14.4 volts, and then to 13.9 volts, and then after more time to 13.2 volts or so. The 14.4 volts would be a combined bulk and absorption, I think, but PD says that takes the battery to something like 90% and then the 13.9 volts finishes it off. This is very different from all the other profiles, and what folks like Trojan recommend (even recommending a very high ending voltage). One thing that the profile they do would work well for is the above mentioned solar applications. From what it looks like, the charger would run the same profile no matter if the solar was holding up voltage and generating amps, or not. In this case, the very simple could very well outperform the quite complex chargers. You could duplicate that type of profile with the Blue Sea by zeroing the ending amps and running on the absorption min and max timers, but that would defeat many of the benefits of charge control from ending amps.

I think we may start to see solar setups, and/or chargers, that take crosstalk into effect in the future, as I think there are going to be many disappointed folks who put solar on and don't get the results they expected.

[booster]

I think I have a pretty close to final settings figured out. Just did a draw down of 203AH of the 375AH of batteries. SG check showed the the 260AH GC2 batteries at 56%, the 115AH SCS200 at 45%, which is consistent with what I had seen in the past. The 12v SCS gives up and receives AH more readily than the big 6 volt GC2 batteries do. Setup charge at 14.6 absorption/13.2 float.

Because the SCS battery takes charge more easily, I decided to try to get it into the .5 volt reduced prefloat earlier than it would normally be if charged by itself. By increasing the ending amps setting, it would be switched into prefloat before the end of a total fillup absorption cycle. I used 4.0 amps instead of the approx 2.1 that would be the real ending amps. On the GC2 batteries, I used the correct 1.6 ending amps, and put a long 12 hour maximum absorption time.

Plugged it in and let it run. Bulk ran about 3 hours, and all banks go into absorption together. The SCS battery was into prefloat in about 5 hours, so it was through bulk and absorption and seeing 14.1 volts. The GC2 batteries stayed in absorption another 6.7 hours beyond what the SCS did.

I checked the SG of the batteries to see where they were after the charge cycle. The SCS was at 1285+, so the 6.7 hours at the reduced voltage was still able to complete the full charge, and the reduced voltage let it run cooler with much less gassing. Pretty much what I was hoping for. The GC2 batteries checked at 1265/1275, which is typically where they had run in the past, but is a bit low. It was then I remembered I had planned on equalizing the GC2s after the last test, but that was when the first charger failed, so it didn't get done. Better late than ever, I did a 1 hour equalize, which brought it up a bit and evened it out a bit also. Did another 2 hour equalize and they came to 1283 SG and even with 5 points. This is right where they should run, and they have never been that high since we got them. The Blue Sea charger has a better equalize than Xantrex, or the Tripplite we used to have, as you can set the voltage and the current, plus it is temperature compensated. I used 2% of capacity for the current and got moderate gassing, and only 3* C temp rise. Unfortunately, what I didn't learn is if the test cycle would have brought them to the 1283, if they had started there, but it did bring them to where they were when they started before the discharge, so I am thinking it probably would.

At this point, I think I am done until we get a bunch of real time camping and use on the system and see how the batteries do. There is no doubt that the batteries are getting at least 10-15% more into them than when charged with the Tripplite we had.

I have been trying to get information from Morningstar about how the solar controller reacts to different events, like being turned on and off, sunrise, alternator voltage, etc, but I call, wind up leaving a message, and get an e-mail back that answers things I didn't ask and ignores what I did ask. Pretty frustrating, and if I answer the e-mail and reask the questions, I get no response. I will keep trying.

As I look at the entire system, I am really glad that I put the solar on an easy on/off toggle switch. I put it in just in case I needed to shut it off for storage or any of the not playing well questions, but with the intent of leaving it on nearly all the time. Looking at it now, I am starting to think that under a lot of conditions, off may be the best. Whenever the charger is running, off is best because of the ending amp confusion from the charger seeing the solar amps, and there is no need for its output. Parked inside, off is best because it is using some power, but generating none. Same is true at night if you are boondocking and fanatically trying to minimize power use. When driving, I think it could go either way. If the batteries are low when you start out, the alternator from the van will be doing almost all the charging, so the solar could be on or off. If it is off, you are not using up absorption timer time that might be more useful later, but I think that is a minor consideration, and if the solar starts a new timer cycle when turned on, it is a mute point. If the batteries are full, or nearly full, when you start out, having the solar on gives you the opportunity for it to put 14.8 volts on the batteries to do the most complete top off available, so on would be good then, if the batteries haven't been topped lately. Our total ending amps is under 5 amps, so the solar will easily hold voltage and current on full batteries to top them off. When you stop to hike, sightsee, whatever, of course the solar would be on. The good thing is that the solar can't mess up the charger going into a full charge cycle, as it will always run a minimum absorption time and go to ending amps. This is a big one, as many chargers will go right to float. The solar can only affect when the charger goes to float, so it could only leave you a few % short of a full charge, in the worst case. If you are charging overnight, which is typical for us, there would be no solar to mess up the ending amps as it would be dark out.

The system should be pretty automatic, except if we are trying to absolutely maximize battery life and recharging to maximum refill. Under those conditions, one thing we would be doing manually, I think, would be to run off one bank of batteries at a time to prevent the uneven discharge rates between them. We have selector switch so that is very easy. The other would be to turn the solar off on occasion, again very easy as it is on a toggle switch.

It does look like the changes are going to be able to do all the things we hoped, so we are very pleased at this point. The last part, which isn't charging related, is to get the 250 amp alternator in,when it gets here in a couple of weeks, to reduce or eliminate the drain on the batteries if we run the microwave off the inverter and van engine.

[Davydd]

You guys (Marko and Booster) make my head swim with your technical talk. Maybe it is because I don't put pencil to paper and try to figure this stuff out. I know there has been a lot of criticism of Roadtrek's E-trek claims with the batteries and solar stuff. I'm assuming, Booster, you will be gaining a lot of practical knowledge once you hit the road with your customization. I anxiously await that.

Here is where I am. I have two D31 house wet cell batteries. I just got back from a 5 week trip after an over the winter plug-in at home. Not once did I run my propane generator. My batteries seem to hold its charge well. I checked my cells yesterday and had to add about 3 cups of distilled water to top them off. I am assuming the Progressive Dynamics smart charging converter is doing its job on the four year old batteries as I leave the B plugged in to shore power over the winter.

Now I am thinking I would like a B I could boondock without a generator or propane. That would require multiple batteries and solar. Also, I would camp when and where I don't need air conditioning. I've got a pretty good 9 year track record with that intuition and I have even boondocked successfully up to 5 straight days with my current B. It won't be a Roadtrek E-trek as the layouts just don't meet my criteria. Has anyone looked at Advanced RV's electrical systems design? I will be going to their open house next week and would like an independent opinion.

[markopolo]

Booster - That's great. It does look as though you have optimized the setup already. It's nice that you can mix battery banks and still provide specific and ideal maintenance for them. It's a really good setup. And, the solar input on /off solution is easily workable. Some sort of relay or transfer switch could turn off the solar input automatically when it senses power coming from the Blue Sea unit I would think as long as it doesn't waste power itself. Manually controlling it is simpler.

Davydd - The more I learn the more I realize how much I don't know. I learn something new every time Booster posts I think. My expectation is that you will find high quality brand name components in Advanced RV's setup. I can't imagine Mike doing anything less. I'd like to know more about what they are using.

[booster]

Davydd, It is no question that we "technoloonies" spend a lot more time and effort on these things the we probably should, but it is a better hobby than drinking in the bar, I would think.

Your system, from what I have managed to find out about things, either by luck or design is pretty well balanced. Progressive Dynamics appears to go into full charge mode everytime you plug in, and I think they all run for 4 hours total (bulk and absorption) then drop to something like 13.9 for a while, and then to 13.2v for float. If the charger is the right size for the batteries, and you drawdown is pretty consistent and right for the size of the charger, the batteries will fare well. Many of the "smarter" chargers, like the Tripplite and Xantrex, can get fooled into not charging under some conditions, and mess up your batteries. The PD charger would error to the overcharge side in many cases, but you have we cells so the penalties for overcharge, especially in only 4 hours, are not major. It would be interesting to see what the specific gravity of you batteries is when coming off the charger, as that would give the best indication of their condition and capacity.

The system you mention desiring is very close to what we have. We do have the generator still in place, but it will be used only for air conditioning once the big alternator gets here. We do still have propane, but it is only used for the outdoor gas grill and stove. We have 200 watts of solar and 375AH of battery.

Your past history will certainly help you determine how long, and how to, be off grid more often and for longer periods. The one major change you will incur would be that you would be into a compressor frig if you go without propane. That will cost you 20-60 amp hours per day, depending on the frig and the weather. In normally sunny weather and out of the shade 200 watts of solar will more than cover the frig, with some left over. A 300-400 watt system would be wonderful and make you pretty much independent of of shore power, assuming you figure out a way to get heat if you need it, like with the diesel heating systems.

I agree with Marco that Advanced RV is probably going to be able to give you what you want, with top notch components and service. It will cost you, but that is the way it goes for good stuff. Solar, maybe 4 batteries, engine generator, big inverter, compressor frig, diesel heat, perhaps extra ceiling vents do to no AC, in an Advanced rig would be very nice. I think we all would be jealous.

I can tell that we are very much looking forward to seeing how well our system works in the real world. There always seems to be something that you miss, but we are very hopeful that we will be nearly free of shore power needs.

[booster]

Marko-we are still considering the auto off on the solar, and will know for sure if it would benefit much when we get a bit more information from our early runs later on. The one issue on doing it off the charger is similar to what I was running into, in trying to design my own controls, before I found the Blue Sea charger. Controlling things off the shore power requires 110 volt relays, which are much more difficult to deal with than the low voltage stuff. Boxes, covers, protected connections, etc. There does seem to be a good way to do it, if the Blue Sea has enough output on the ACR control (they say it will run 2 ACRs which is what I now have) to run a 12 volt relay or another ACR. It then would disconnect the solar whenever the charger came on, at the same time it isolated the battery banks. The next time I talk to Blue Sea, I am going to ask them about it, in case we decide to do it. I also need to ask them what they recommend for multiple bank temp sensors on the batteries. They only have one input on the charger. I may wind up with two sensors and a switch box or plug/unplug (I think it is RJ11) to be able to check the separate banks, or charge or equalize just one bank.

[Davydd]

Advanced RV's heating and water heating standard is diesel and they have gone solely to a compressor fridge as standard. That alone has omitted a lot of propane consideration. I currently have a BBQ propane connection on my GWVan but have only used it a couple of times and I do carry the hose. Most of the time we use the small disposable tanks but my wife chose to cook outside with her electric skillet this last trip and we never did fire up the Coleman stove because it was so windy. I used my Dutch oven and charcoal and made pizza twice. I figured out in a campground without a fire pit or grill putting charcoal in one of those aluminum turkey basting pans you can buy for under $2 in a supermarket works fine. Of course I have been known to scrape away a little gravel and charcoaling right on the ground.

I don't know if I would want to go 100% without propane. I'm wondering if a standard BBQ 20 lb. canister could be mounted outside underneath where you can pull it out and exchange it at almost every service station. I would not want it on the back end.

[avanti]

As I see it, propane is all about air conditioning. If you think you can do without cooling, then lose the propane. If you need A/C while dry camping, a propane genset is still the only way to go. Road Trek and Advanced are making heroic efforts to change this equation, but IMO neither has fully succeeded yet.

In our new Legend, the only propane consumers will be the stove and the genset. We looked carefully at eliminating it (including considering the diesel genset alternative). Ultimately, we concluded that keeping the tank has very few disadvantages. First of all, it doesn't cost that much (well, the genset does, but not the propane tank). On our old Interstate, the propane system was completely trouble-free. And a tank of propane can happily sit there forever until it is needed. I am having them add a solenoid valve with a convenient indoor on/off switch, so the system will be dormant except when it is needed.

[obgraham]

Speaking here strictly from hearsay, it seems to me the effort to move to a single energy source is still a work in progress.

Roadtrek has done it with the RS-ETrek. However, I wanted the bigger storage of the Roadtrek CS. They offer an E-Pack on that, and some were built using the Webasto diesel-fired heat/hot water unit. However, factory tells me they have returned to the Alde propane-fired heat/hot water system. Chatting with folks, the Webasto has not been trouble free. Looks like I'll get the Alde.

I'd just like a system that works well, that I can live with in no-hookup places, stay warm, have a decent size reefer and run my techno-toys. Looks like propane is not dead yet.

[booster]

Originally Posted by avanti

As I see it, propane is all about air conditioning. If you think you can do without cooling, then lose the propane. If you need A/C while dry camping, a propane genset is still the only way to go. Road Trek and Advanced are making heroic efforts to change this equation, but IMO neither has fully succeeded yet.

In our new Legend, the only propane consumers will be the stove and the genset. We looked carefully at eliminating it (including considering the diesel genset alternative). Ultimately, we concluded that keeping the tank has very few disadvantages. First of all, it doesn't cost that much (well, the genset does, but not the propane tank). On our old Interstate, the propane system was completely trouble-free. And a tank of propane can happily sit there forever until it is needed. I am having them add a solenoid valve with a convenient indoor on/off switch, so the system will be dormant except when it is needed.

Those getting the diesels do have an advantage in getting rid of the propane with the diesel heat. Those of us with gas are stuck with the noisy Suburban furnace for heat. We would keep the tank anyway, though, as we use our gas grill and/or stove outside nearly every day, many times more than once a day. The little bottles are a PITA, very ungreen.