Interesting read on battery SOC measurement.

[papab]

Booster, where did you see a 14.6 recommended? I've been bumping it up some days, so this is nice that they've endorsed it.
You don't think there is any damage from leaving at absorb voltage until 0.2%C amps?

[booster]

Originally Posted by papab

Booster, where did you see a 14.6 recommended? I've been bumping it up some days, so this is nice that they've endorsed it.
You don't think there is any damage from leaving at absorb voltage until 0.2%C amps?

The 14.6v has been showing up on the individual cutsheets for the batteries, but not in the general recommendations yet.

I think this is the battery you have

Lifeline Batteries - Marine & RV Deep Cycle Batteries

As to charging to the lower %, I can't say for sure on that one. My best guess is that it is probably less harmful than leaving them that amount uncharged. Best is probably to have enough time to let it complete on float after the .5%, which can be very tough on the road, where the only chance for that would be the solar. Tough to do from a time standpoint. Of course older or different batteries may not get that low. When I was using the Blue Sea charger, they recommended testing whatever batteries you were going to use and set the return amps to a bit above that amount of amps.

It is also of interest that there seems to be a trend of the battery manufacturers, other than Lifeline, to recommend an extra stage at the end of the charge cycle. It boosts the voltage to the 15v range, limits current to a % of capacity usually, and is about an hour IIRC. I think this would indicate that they are trying to address sulphate and undercharge issues by doing a mini conditioning cycle more often. The assumption must be that any damage from gassing would be less than the damage from the other issues. If we start to see any degradation, I will probably give it a try when traveling as we can do it from the remote pretty easily, and at 15v we shouldn't have to disconnect any electronics, although for us that is just to shut off the 12v power relay and pull the solar fuse.

The extra time on ours to go from .5% to .2% is in the 4-6 hour range, so it is not a quick process. That is why we have been testing if the float will do it, and how long it takes if it does.

Our last trip was on the old 260ah of wet cells and we tried to simulate how we would run the new setup and found the best results, when we hadn't been able to plug in for a while, was to leave the engine charging on until we got to about 2 amps to the batteries. By then the solar was contributing that much so the engine alternator could be shut off. We have the luxury of seeing both the total power to the coach and that to just the batteries, from the cockpit, so we can tell when the solar is taking over. On the bigger system of 440ah, it will probably take 2 to 4+ hours of driving to get us to the point of the solar taking over at a 50% discharge and decent sun. Most days that would usually get us to float in about 6 hours from starting so maybe 4+ hours of float. Still a bit marginal but not too bad. We can charge off the alternator up to about 190 amps hot.

I have a few years old Truecharge20 with remote that I was using as a bench charger, but I couldn't adjust voltages or get it to go back into absorption on mostly full batteries. Can the newer ones like you have do those things?

[papab]

It's still switches to float way too soon (6 amps). That's been one of my frustrations. I switch to gel/cold and get 14.4 V, which is enuf when it's warm. I have the temp sensor and I added 2 pots in series so I can fool it to use the cold compensation even if it's warm.
That's interesting that lifeline increased their V recommendations. I'm puzzled why they didn't tell me that when I talked to them & emailed them only a couple of months ago.
I read several studies about charging AGM's at over 15V & having no issues with that, but they were thin plate or spiral AGM's, not thick plate like lifeline, so I'm a little hesitant to charge the lifeline that way.

[booster]

Originally Posted by papab

It's still switches to float way too soon (6 amps). That's been one of my frustrations. I switch to gel/cold and get 14.4 V, which is enuf when it's warm. I have the temp sensor and I added 2 pots in series so I can fool it to use the cold compensation even if it's warm.
That's interesting that lifeline increased their V recommendations. I'm puzzled why they didn't tell me that when I talked to them & emailed them only a couple of months ago.
I read several studies about charging AGM's at over 15V & having no issues with that, but they were thin plate or spiral AGM's, not thick plate like lifeline, so I'm a little hesitant to charge the lifeline that way.

They never told me when I talked to them either, and I found it kind of by accident when I was looking for the max charge rates.

Your charger issues sound way, way, to familiar. We are on our third charger since we got our Roadtrek in 2008. Tripplite that left everything partially charged, Blue Sea to handle mismatched battery banks and let us learn about termination of absorption by amps (but it did it internally so loads hosed it up), and now the Magnum which does pretty much everything we need to do very well.

Here is a link to the Fullriver battery charging instructions.

http://resources.fullriverbattery.co.../batteries.pdf

They show the standard charge profile style, albeit at higher voltage than Lifeline, but they have a second profile for constant current charging that goes all the way up to near 16v. As far as I know these are normal AGM batteries, not TPPL, so that says something, I guess. High voltage also must not hurt Lifeline a bunch as they will let you go to 18v to try to save a totally dead one and 15.5v for conditioning.

[booster]

Papab appears to be exactly right with his observations of the Truecharge 60 dropping into float at 6 amps, and it also appears there is likely nothing he can do about it, without trying to trick it.

Here is the charge curve that is in the Truecharge 60 manual



They show the float transition triggered as "Iout<10% Irating for one minute". They have to be using charger charger output, as you can't program bank size on that charger, and that comes out at 6 amps. This would also explain the section where they want you to have the preferred battery size to meet the charger that is quite specific.

IMO, basing the transition on the charger capacity is like saying how much money you have based on the size of the bank. May not even be as good as a straight timer for absorption. It doesn't say anything about a minimum absorption time, so it may just bump out repeatedly, if you got it back into absorption for another cycle.

I am a big fan of using amps to control charging, but this is a very, very, poor way to do it.

Papab has a 150ah Lifeline, so the .5% would be .75 amps, so if he turns on a load that is over 5.25 amps in the van, he should be able to keep the the charger in absorption until he sees his .75amps, or even lower maybe, on his battery monitor, which is reading only battery current.

[papab]

I agree, it's a crappy design. None of the chargers in this price range have an appropriate trigger for switch to float. In hindsight a timer trigger would be better if you could restart the timer. I've thought about setting up a load to keep the charger in absorb more, but the only thing I have that's close to big enuf is the fridge, but that seems like a bad idea to wear out the compressor.

[booster]

Originally Posted by papab

I agree, it's a crappy design. None of the chargers in this price range have an appropriate trigger for switch to float. In hindsight a timer trigger would be better if you could restart the timer. I've thought about setting up a load to keep the charger in absorb more, but the only thing I have that's close to big enuf is the fridge, but that seems like a bad idea to wear out the compressor.

You are exactly correct, nothing in the price range that will end on battery amps. In fact almost none that will at any price. Magnum is the only one I know of, and you have to get the inverter too, because they don't make just chargers. They have come out with a smaller, lower cost, line, but they are still way more than the Truecharge, I think, as you need the remote and monitor kit to go with it. It gets closer to the same cost if you are comparing with buying a stand alone inverter and a monitor and the charger, as all are in the Magnum.

For a manual amp based system, I think the charger of choice is the Progressive Dynamics with the optional pendant. They have a fixed absorption time of 4 hours and with the pendant can be forced in or out of absorption, so you can run them manually. They are charger only and reasonably priced.

We have learned lately that some of the PD chargers don't allow forcing anymore. I think they are only the ones that have the built in Wizard, but Marko would probably be up on what models work and wouldn't work for manual amps charging.

Every time we see another charger that doesn't work well, it just amazes me, as it is not rocket science to do right.

[booster]

Originally Posted by papab

I agree, it's a crappy design. None of the chargers in this price range have an appropriate trigger for switch to float. In hindsight a timer trigger would be better if you could restart the timer. I've thought about setting up a load to keep the charger in absorb more, but the only thing I have that's close to big enuf is the fridge, but that seems like a bad idea to wear out the compressor.

You could probably find some kind of a 12v appliance that would do what you need. They make all kinds of cooking stuff, heaters, fans, lights, etc of various loads and pretty inexpensive. The trucker websites are very good places to look. You could also get a small inverter and run anything AC that gave the right load. I have seen it done with resistors, but they get really hot, so not really a great solution.

When we still had the Blue Sea in ours, up until this winter, we had the same issues because the charger saw the loads and got confused. I finally figured out what combination of loads and setpoint for amps (which we had on that charger) was a pretty good compromise and we kind of got by. I later added a couple of relays to switch the loads to the 3rd bank output of the charger when on charge, with the batteries on the other two banks, and that worked well. Unfortunately, you wouldn't be able to do that because your banks aren't independent, as far as I know, so the charger just adds the ouputs together in the calculation.

[Oliver]

Per Davydd:

Advanced RV's high idling parked or driving would replenish 300 amps in an hour with the second under hood alternator.

Would there be a benefit to adding a 3rd alternator, especially to replenish high A/C consumption

[booster]

Originally Posted by Oliver

Per Davydd:
Quote:
Advanced RV's high idling parked or driving would replenish 300 amps in an hour with the second under hood alternator.

Would there be a benefit to adding a 3rd alternator, especially to replenish high A/C consumption

I still haven't figured how you replace 300ah from a 270 amp alternator, that actually runs at maybe 240 amps max, in an hour. But that is just me.

I would think another alternator could be used, it there would be a place to put it. They also make bigger than the 270 amp ones, so that would probably be easier. I think the 270 has been the go to setup because that is about the most current a single 4/0 cable can handle.

[Oliver]

Originally Posted by booster

I still haven't figured how you replace 300ah from a 270 amp alternator, that actually runs at maybe 240 amps max, in an hour. But that is just me.

I would think another alternator could be used, it there would be a place to put it. They also make bigger than the 270 amp ones, so that would probably be easier. I think the 270 has been the go to setup because that is about the most current a single 4/0 cable can handle.

booster - AWESOME answer, thanks !!