Deciphering charging parameter specs from the manufactures

[booster]

AGM is at end-wet cells first

For me, it probably all started with the Handybob diatribes about batteries and charging, in particular his insistence that all the chargers were set wrong for Trojan wet cells at 14.4v instead of 14.7-14.8v. He got great results with his setup at the higher voltage, worse at the lower, so it made sense. He also said it was what Trojan recommended, which was kind of true. Trojan talks about using the higher voltage for a "daily charge", but lists the lower voltage under their other charging areas, which was very confusing.

I have everything setup on the bench to test the new Lifelines and Magnum charger, so I had everything available, and some time, so I did a couple of tests on our GC2 Trojans, that are still in very good condition. Easy test. Charged them to ending amps (observed until no change) at 14.4v, checked specific gravity on all cells and temp of batteries, changed charge to 14.7v and charged again to ending amps, checked specific gravity and battery temp. Made minor correction to specific gravity for temp which was a few degrees higher at the higher voltage. Conclusion was that the specific gravity was identical and at the extreme high end of the full range for the batteries, so the higher voltage did not fill them any more than they were at the lower voltage. It did, however, make them gas a bunch more and heat up some. So for this test, that was at about 40% discharge there was zero benefit of the higher voltage. Very lightweight test as it covered very little range, but interesting.

Why did Handybob have better results at the higher voltage? Best guess is that he was on solar, so had limited charge time, and the batteries charge faster at higher voltage, so he could get full in the time allotted only with higher voltage. He also was running a PWM solar controller IIRC, so he probably got more watts available to the batteries at the higher voltage.

Why does Trojan give the higher voltage? Best guess is because most of their batteries are in golf carts, they get run way down every day, and have to get full overnight. Not enough time at the lower voltage. Thus the term "daily charge".

What is the right one for an RV? If you have a charger that can read return amps, and the time to do it, I think the lower voltage would probably be best. If your charger is on timers only, and is leaving you repeatedly short, or you are way down and have a shorter time, the higher voltage might be best. I had always assumed that the higher voltage would always be best, but I really think that may have been incorrect. Still not proven conclusively, however.

AGM will be on new post, this is getting too long

[booster]

Now for AGM

As I have been reading all the Lifeline, and some of the other brands, literature and recommendations for the charging parameters, there are some similarities to the wet cell questions.

Lifeline has increased the range of their absorption voltage to 14.6 on the high end from 14.4 on some, but not all, of their literature. Desired used to by 14.3v +/-.1, now just gives 14.2-14.6v. There are notes on some parts of the literature to use the higher voltage (this was in a 14.4v max description) for "heavy duty" applications, whatever that means. It might mean deeper discharge situations, but they address that elsewhere by saying you should have at least .2C charging capacity if you have over 50% discharge with no mention of voltage. From this I would have to guess the "heavy duty" use would be more related to short charging times, similar to the reasoning behind Trojan's voltage increase for "daily charging".

I looked all over to try to find good information on the actual gassing voltage of AGM batteries, and how efficient the recombination of gas is, and that information is really tough to find. Several places mentioned 14.3-14.4v for the gassing voltage. Victron was very specific at 14.34v. Their charging suggestions were also interesting with 14.2-14.6v for normal charging and up to 14.8 for fast charging. They also mention using 13.5v for float, but reducing to 13.2 for non use float (storage). Everyplace that even mentioned the recombination efficiency just said it was never 100%, and you always lose some water.

In the big picture, I guess a lot of this, when put together, does start to head the same way for what to choose (at least in my mind) for settings. I had only one major question and that was if the higher voltage got the batteries more full, or just faster. I did the same test as with the wet cells, but had to go by resting voltage without specific gravity access. I charged to lowest observed return amps at 14.3v, took the battery temp, let it rest 4 hours and checked voltage. Did another charge at 14.6v to lowest return amps and the same rest and check. Both were at the same 13.2v after the rest time, so it appears they were equally full.

I think that brings it back to similar to the wet cell example of using the lower voltage if you have the time and charger control. There is an added benefit with the AGM of staying lower in that gassing is reduced at the lower voltage, and not all the gas is recovered, so that is good. That loss of water might be a factor in life. The higher voltage also generated more heat, and the manufacturers claim significant reduction in life with temperature increases.

For AGM, I would say the same as with wet cells. If you have a very well controlled charger and the time, use the lower voltage, which for use would be 14.3v for the Lifelines. If you aren't getting full on a regular basis use the higher voltages.

Float voltage next post

[booster]

Float voltage selection.

I decided to try to determine if the float voltage, within the range given by Trojan and Lifeline made a difference in anything I could see.

I did the Trojans first after a full ending amp charge cycle. At the high end of the range there was a tiny amount of gassing I could see in the cells that was not there at the low end of the range. Watching the ammeter at the various voltage settings, it got immediately obvious where to set the float. At 13.2v, there was no amperage flowing to batteries, at 13.3v there was, so that current would just go to gassing or heat, which are both bad.

Interestingly, the Lifelines also showed zero current flowing at 13.2v but some at 13.3v, so that would put them also at 13.2v float for the same reasons as the wet cells. It is also the voltage that they rest at after a full charge, which also makes sense.

I think this determination of best float voltage by using the zero current point would be applicable to any battery setup. I am sure that it would not negate the need for periodic boost charging, though.

How we will initially set the new charger up with the Lifelines next post.

[booster]

How we will setup

The old original Lifeline parameters are very good, I think, and that is what we will nearly use.

Absorption 14.3v which is the old recommended midpoint

Float 13.2v which is low end of old recommended (.1 under midpoint)

Return amps set to 2 amps, which is slightly under the .5% max that Lifeline wants. The batteries actually go to 1.7/1.8 amps, but the Magnum won't set to .1 settings.

In normal camping we will use the normal 3 step charge program with the absorption to float transition based only on return amps, as the SOC program looks to be much less accurate.

In storage, I think the best will be to switch the charger to two step charge and then off and monitor mode. In this mode you can set a recharge voltage for the charger to come on and run a charge cycle. If I set it at 12.6v or so, with the very low discharge rate, it will run a charge cycle rarely, but it should be enough to keep the batteries in good shape. My guess it will be better then continuous float charge all winter in storage. I will put the starting wet cell on the little Ctek which does very good job in it and will also keep the van electronics active.

As with most of this stuff, all of this is guess and hope . Any comments, suggestions, or opinions are very welcome so we can all learn some things.

[Boxster1971]

Thanks booster - good info as usual. With all these variables for Lifeline AGMs would I be better off with the Mangum ME-ARC50 remote or would the legacy ME-RC50 do well enough?

[booster]

Originally Posted by Boxster1971

Thanks booster - good info as usual. With all these variables for Lifeline AGMs would I be better off with the Mangum ME-ARC50 remote or would the legacy ME-RC50 do well enough?

I will have to look at the online manual for the RC50 to see what it covers, as it has been a long time since I went through the differences. I wound up with the ARC50 as it was kind of a package deal and that reduced the price difference enough to make it a no brainer.

[markopolo]

Originally Posted by booster

Now for AGM.................................. I charged to lowest observed return amps at 14.3v, took the battery temp, let it rest 4 hours and checked voltage. Did another charge at 14.6v to lowest return amps and the same rest and check. Both were at the same 13.2v after the rest time, so it appears they were equally full..........................

Very informative post.

The results speak for themselves.

I wonder if a 5 minute load to remove the surface charge after the 4 hours would have shown any difference?

The trend toward higher charging voltage is probably be related to time as you noted. It's better to get them full than leaving them partially charged before the next cycle and higher voltages would help do that. By tracking ending amps you take the guesswork out of the process.

Your batteries should last a long time

[booster]

I just took a bit of a look, the manuals are near 100 pages for the RC and over 200 for the ARC, so it is tough to compare everything without having them setup to try the actual controls.

The ARC has lots of stuff we won't use like the clock timing of AC on and quiet times, etc. It also has the stuff to run their solar controller, which isn't even available, so that is wasted. The auto generator start is a much larger section, but I never ever read ours because we won't have a gen.

There are a few things that are in the ARC that I wouldn't want to go without.

* The five setable "favs" or favorite buttons. You can set up things you want to be able to see quickly and regularly, which is a very nice feature. Unfortunately it won't accept action button controls like forcing bulk, etc, but it still very useful I have BMK volt, BMK amp, AH in/out counter. Nice feature.

* The ability to force the unit into float or bulk at any time. It may be there in the RC, but I couldn't find it. Without that feature you really can't run the unit in the normal 3 step program in a lot of cases because it will not do a full bulk start charge if the batteries are above 12.7 volts, and will go straight to float. Surface charge from driving or the solar will often hold up the voltage, so you could not get a full shore charge when you stop and plug in. We will be stopping only occasionally to get a full shore charger charge, so we positively need to be able to get it easily. It will always do a full bulk charge if in CC/CV mode, but then you don't get float and it will quit charging when full and you will run off batteries until you unplug or the voltage drops to the setpoint of 12.7. This is a real biggy for us and would make the ARC necessary for us.

* You get a few more history type things related to how long since this or that and min/max voltages, etc. Not a big deal with us, but could come in handy.

* There is a linking feature to some of their other products and added chargers that we won't use.

Bottom line for us is that it appears we need to have the ARC50 so we can force to float or bulk, and the favorites will be very convenient, beyond that nothing is really necessary for us, on interesting.

I could easily have missed some things, as I went primarily off the menu maps, and there may be some added things in the many pages of text.

[Boxster1971]

Thank booster. For an extra $50 it will probably be worth just buying the ARC remote.

[booster]

Originally Posted by markopolo

Very informative post.

The results speak for themselves.

I wonder if a 5 minute load to remove the surface charge after the 4 hours would have shown any difference?

The trend toward higher charging voltage is probably be related to time as you noted. It's better to get them full than leaving them partially charged before the next cycle and higher voltages would help do that. By tracking ending amps you take the guesswork out of the process.

Your batteries should last a long time

A load takes them down, but not nearly as quickly as the wet cells do. IIRC I had to be 10ah down to get under 13 volts. If no load is put on, they stay over 13 for a month, it appears.

I think by looking for the zero amp input area ( which is probably actually a tiny amount in depending on the self discharge rate), I think you are hanging the batteries right on full with surface charge point, and it seems to just sit there with nothing going on. If you take off the surface charge down to 12.8 volts, it will be pulling current at 13.2v float. I imagine if you set the float to 12.8v it would just sit there also, but I wonder how that would affect the life compared to totally topped? Interesting proposition.

My guess is that Lifeline chose the 14.3 and 13.2 volts very carefully initially to be the best in the lab, and have since been modifying a bit because of the chronic undercharge we seem to see from most chargers in use in RVs and boats. Just my opinion, though.

This is very interesting stuff!