Interesting read on battery SOC measurement.

[Davydd]

The second alternator does affect fuel mileage as you can see it on the Sprinter MPG scan. As soon as you hit 100% charged the MPG jumps up a little. It is difficult to tell unless you are monitoring for it because the Sprinter computer is steadily building a higher MPG the longer you drive. Since we hit 100% typically in under 20 minutes after a boondock stay at a place like Walmart it is hardly noticeable. But wouldn't a single chassis alternator have the same effect on mileage? Energy is not exactly free. They say plugging into your 12v with a smartphone will lower your mileage.

I don't know if a second alternator would be practical until you get well over the one or two battery setups most Class Bs deliver. With 800ah of li-ion batteries we have, it seems necessary to me especially if you intend to eliminate an Onan generator as we have.

The other thing I haven't seen discussed is, at least on Sprinters, since I know little about Promasters and Chevys, the computer electronics satisfy the chassis first and it is designed not to handle much more than a single auxiliary battery in addition. That was why for years Pleasure-way was adamant about providing only one auxiliary battery. MB always had the ability to add a second alternator but assumed for emergency vehicles, ambulances and such. It is fairly new with RVs. Huge battery banks are fairly new as well.

Most of the second alternator solutions have been that 270a Nations alternator - Avanti, Advanced RV and I think Roadtrek. The wire to the battery on ours is sized to be able to take all the amps the alternator is capable of delivering. Advanced RV provides forced air cooling ducted to the alternator reduce heating for better efficiency. I don't think anyone else has done that. Now a little birdie has told me ARV will be going to a different supposedly better alternator manufacturer and eliminate that air cooling. I'm not sure what they are doing but when my B was developed the cost to do what they are doing now was too high and they have since brought the cost down. The point of this, is there is evidently still more development and information forthcoming.

[booster]

Originally Posted by avanti

It is worth noting that in the case of the Balmar regulator in my 2-alternator system, the regulator has a "sense" input that provides feedback to the regulator. The reg will constantly adjust the alternator such that the sensed voltage is kept to the current target voltage (which, in turn, is determined by the 3-stage charge algorithm and settings). So, if you run the sense wire directly to the + terminal of the battery, the system will automatically adjust for voltage drop on the main charge wire.

Is it possible to break a single wire, either the sense or power up or whatever, to shut off the alternator while running, and also be safe from spikes and such on turning on after a startup? Or do you have break the main output and a control wire?

[GeorgeB]

Originally Posted by booster

The interaction of the charging systems is something we have struggled with and discussed here many times.
...
.

Very clear explanation of very enigmatic interactions. An algorithm based on "fuzzy logic" would work I've seen intelligent energy management system concepts in RVs that plan on integrating values such as number of persons, number of days you plan dry camping, temperature forecast etc. Fun, but when it breaks you are stuck with the light-up-a-campfire text message on your phone!

[gregmchugh]

Originally Posted by avanti

Well, this isn't quite true. Although larger cables can't consume current, smaller cables can cause voltage drops which in turn would limit current. So, a too-small-cable could be a half-assed way to limit current.

There are situations in which a cable can be safe from overheating but still produce excessive voltage drop.

True, but I was commenting on the fact that someone told him that the alternator could get overloaded if too large a cable was used...

[avanti]

Originally Posted by booster

Is it possible to break a single wire, either the sense or power up or whatever, to shut off the alternator while running, and also be safe from spikes and such on turning on after a startup? Or do you have break the main output and a control wire?

Yes. There is a signal called "ignition input" that must have +12 applied to it for the system to power up. If you turn this off, the Balmar stops providing field voltage to the alternator and it simply freewheels. I feed this signal through a relay that provides power from the coach battery. The relay is controlled by the chassis "engine running" signal and also from the chassis master switch. So, the alternator cannot run unless (a) the engine is running; (b) the chassis battery is present; and (c) the master switch is on. Should be pretty failsafe. If you wanted to add a manual switch, it would be easy enough.

[avanti]

Originally Posted by gregmchugh

True, but I was commenting on the fact that someone told him that the alternator could get overloaded if too large a cable was used...

I understand and agree. My only point was that if you have a ill-designed system that is only being "protected" by a too-small wire, making the wire bigger could possibly make matters worse. Splitting hairs...

[booster]

Originally Posted by avanti

Yes. There is a signal called "ignition input" that must have +12 applied to it for the system to power up. If you turn this off, the Balmar stops providing field voltage to the alternator and it simply freewheels. I feed this signal through a relay that provides power from the coach battery. The relay is controlled by the chassis "engine running" signal and also from the chassis master switch. So, the alternator cannot run unless (a) the engine is running; (b) the chassis battery is present; and (c) the master switch is on. Should be pretty failsafe. If you wanted to add a manual switch, it would be easy enough.

If I understand how it works (always questionable). If you break the engine running wire to turn off the alternator, and leave the sense wire connected to the coach batteries, you should be able to just turn on the engine running switch and be good to go with no spike? Soft start, so to speak.

Do they sense batteries on the alternator output, or do the use the sense wire? I think that would determine if the alternator would fire up with the batteries off line.

[booster]

Originally Posted by avanti

Yes. There is a signal called "ignition input" that must have +12 applied to it for the system to power up. If you turn this off, the Balmar stops providing field voltage to the alternator and it simply freewheels. I feed this signal through a relay that provides power from the coach battery. The relay is controlled by the chassis "engine running" signal and also from the chassis master switch. So, the alternator cannot run unless (a) the engine is running; (b) the chassis battery is present; and (c) the master switch is on. Should be pretty failsafe. If you wanted to add a manual switch, it would be easy enough.

If I understand how it works (always questionable). If you break the engine running wire to turn off the alternator, and leave the sense wire connected to the coach batteries, you should be able to just turn on the engine running switch and be good to go with no spike? Soft start, so to speak.

Do they sense batteries on the alternator output, or do the use the sense wire? I think that would determine if the alternator would fire up with the batteries off line.

How are you handling the 4 amp load that Balmar says the unit needs to maintain voltage control. (based on what I was told about another system)

[avanti]

Originally Posted by booster

If I understand how it works (always questionable). If you break the engine running wire to turn off the alternator, and leave the sense wire connected to the coach batteries, you should be able to just turn on the engine running switch and be good to go with no spike? Soft start, so to speak.

Yes, that is my understanding. I spoke to Balmar (good customer support, BTW) during the install, and assuming we were communicating, they confirmed that understanding.

Do they sense batteries on the alternator output, or do the use the sense wire? I think that would determine if the alternator would fire up with the batteries off line.

The sense wire. I have it run all the way back to the coach batteries. You could connect it to the alternator output, but then it wouldn't adjust for the voltage drop of the feed wire.

How are you handling the 4 amp load that Balmar says the unit needs to maintain voltage control. (based on what I was told about another system)

I remember that discussion, but I have not observed the issue. I guess my parasitic loads are sufficient. I don't think it is a big deal anyway. Balmar said that it mostly bothers boaters who depend the fake "tachometer" pulses from the regulator--they see their tach go to zero when the engine is obviously running. (BTW: they said that the underlying cause of that issue was the surface charge on the freshly-charged battery. You just need enough load to bleed it off.)

[avanti]

Originally Posted by GeorgeB

If only the ProMaster second alternator option ( Dodge Promaster Dual Alternator Kit with 280XP High Amp Alternator for 3.6L Gas Engines ) was a proven reliable option I would start convincing my upfitter to try it out even if it's a very expensive mod. I have the feeling the Sprinter install is more sturdy. Am I right?

Do you have any reason to doubt the quality of the Promaster setup? I have no data, but I will say that the Sprinter install was VERY robust and fit like a glove. Nation's appears to be a class act as far as I can see.

[GeorgeB]

Originally Posted by avanti

Do you have any reason to doubt the quality of the Promaster setup? I have no data, but I will say that the Sprinter install was VERY robust and fit like a glove. Nation's appears to be a class act as far as I can see.

No, but I read about some RT issues with the second alternator in other forums. I think it was mostly Sprinter installs.

[booster]

Originally Posted by GeorgeB

No, but I read about some RT issues with the second alternator in other forums. I think it was mostly Sprinter installs.

I think that the issues on the Sprinters that Roadtrek had did not have a lot to do with the Nations parts (I think they still use the DC Power alternator). They did things like not put the power hungry engine generator on a separate belt, and have had thrown belts and early belt failures. Their control system has been problems in all regards.

I don't think I would be in any way afraid of a Nations setup on a separate belt, with it's own controls that are well done.

[GeorgeB]

Originally Posted by booster

I think that the issues on the Sprinters that Roadtrek had did not have a lot to do with the Nations parts ...I don't think I would be in any way afraid of a Nations setup on a separate belt, with it's own controls that are well done.

Thanks! Good to know. Except for the very secretive RT, I didn't find many DIY converters that installed it yet.

Found the RAM alternator output curves in case someone is interested http://www.rambodybuilder.com/2015/d...maltoutcrv.pdf

[booster]

Originally Posted by GeorgeB

Thanks! Good to know. Except for the very secretive RT, I didn't find many DIY converters that installed it yet.

Found the RAM alternator output curves in case someone is interested http://www.rambodybuilder.com/2015/d...maltoutcrv.pdf

Are those the same alternators that they use in the vans? The callout for engines seems to indicate the pickup applications.

[GeorgeB]

Originally Posted by booster

Are those the same alternators that they use in the vans? The callout for engines seems to indicate the pickup applications.

You're right. It is for the Ram Chassis Cab pick-up truck. No info on the ProMaster Alternator specs.

[papab]

Originally Posted by GeorgeB

In the 3 months of use I noticed that if I don't plug it on shore power it sometimes takes forever to reach the 100% value and often never reaches the "charged" blinking light status.

.

Sorry I'm late to the party, I've been traveling

I don't know what kind of batteries you have, but I've observed this too (with my AGM's) when I went a while (a week or 2) without getting a 100% charge. It takes longer and longer to get there, the battery isn't taking in current like a good battery. I talked to lifeline about it and they said they were probably sulphated. There recommendation was to equalize/condition them, and try to charge them up every day.

[booster]

Originally Posted by papab

Sorry I'm late to the party, I've been traveling
I don't know what kind of batteries you have, but I've observed this too (with my AGM's) when I went a while (a week or 2) without getting a 100% charge. It takes longer and longer to get there, the battery isn't taking in current like a good battery. I talked to lifeline about it and they said they were probably sulphated. There recommendation was to equalize/condition them, and try to charge them up every day.

That is interesting as most would say once a week to totally full or so is enough to not walk down capacity. The obvious question that has to come from all this is how you have things set to show the 100% full on recharge, and what kind of charger and controls you have. We have had a lot of discussions about how most charging systems don't get the batteries really full, almost all the time, and that causes walk down just be itself. It also prevents the battery from getting a good recovery from and deep and/or long time discharge. Lifeline wants a pretty hefty charge rate (40% of capacity in charging amps) when you get to 50% discharge to help prevent the problems.

[papab]

I consider it 100% when it meets the lifeline recommendation of 0.5% amps (0.75 amps for 150 aH), at 14.3V (+temp compensation). I have a truecharge 60 amps so I can get .4C. I can get even more if I charge straight from the van system. I get the impression that it is more than just walking down, it is sulphation causing increased resistance and reduced capacity. Conditioning soon enuf can help to convert it back to useful stuff.
I also have a 100W solar array with a PWM controller. If I have sun I can get to 100% almost every day just from that. My 1st trip which probably took some life out was with nothing to charge with but the van system, plenty of alternator capacity, but only 14.1 V. The other trip was to the rainy Pacific NW and solar didn't do much and I didn't drive enuf to get it charged up either. I kept it above 50%, but I think it was close to 2 weeks without a 100% charge. I was ignorant how much this was harming the battery. I'll plug in once a week if I get in that situation again.
I tried to get lifeline to give me a guideline like 90% every day and 100% once a week was good enough, or some fastcharging guidlines (that last 5% takes a long time), but they wouldn't go there.
I have a trimetric batt mon & keep an eye on it.

[booster]

You have all the stuff you need to keep track of things well, that is for sure. The two weeks at low state of charge, as you said, probably was a big contributor to your issue.

One thing that we have found in testing on our new Lifelines is that they weren't actually full at the .5%C amps, it appears. I continued at absorption longer and they actually got to .2% before the amps quit dropping. It did take a long time to get there, at about 12+ hours for a 50% discharge and a 100 amp charger for 440ah. At that point they floated at .1 amp. If I stopped at .5% they floated at .3 amps. A long float also will bring the batteries to the very low float also, it appears. If they float for a few of days after either a .2 or .5% ending, the float goes to essentially zero. I think Lifeline says .5% because they have to cover new and old batteries, and it probably will change over time.

I am not sure what it means in the real world, except the charge times start to get longer than you would have in an overnight recharge stop, unless you got to the 98% full point from the alternator and solar driving there, which is really not too hard to do. I also have no idea if going to this extreme would help life, but it seems like it should. I don't think anyone really knows, as you experience with lifeline showed.

As for the fast charging, I did do a test at the max recommended voltage of 14.6v on ours compared to the 14.3v we normally had been running. The 14.6v is relatively new for Lifeline and is a couple of tenths higher than they used to be. It shortened the absorption time some, not a lot, may an hour or two. Battery temp got about 5-10 degrees warmer. Amps at the end was only about a tenth different. We are seriously considering using the higher voltage when we are traveling, along with a higher float voltage of 13.6v to give a "mini conditioning" type charge when we are plugged in. My guess is that Lifeline has upped the allowable to help counteract the incomplete charge and sulphation issues for folks that have trouble getting full all the time, like the boaters. We will continue with 14.3/13.2v at home where we have time, or if we are somewhere with shore power for an extended time.

[booster]

I should clarify the 40%C for deep recovery. The manual says 20% minimum, but when I talked to Lifeline about it, they said 40% would be even better. We can't even get to 23% on ours, so papab is in better shape that way.