New AGM batteries not holding charge

[JimNCheryl Domenoe]

I recently installed 6 new LIfeline AGM house batteries.  I also replaced all of the connecting cables between batteries. The Magnum ME-RC was set to the correct setting for Lifeline AGM batteries which is AGM2.  The Smart Combiner was set as follows: Connect voltage %u2013 13.5V; Low voltage disconnect %u2013 12.7V; High voltage disconnect 14.3V.

We are on our first trip in which we have to dry camp.  After the first night on battery power, we got up in the morning to discover that the battery voltage had dropped to 11.5V.  According to the Lifeline manual, this is 100% discharged.  Nothing was used in the coach except the LED lights for short periods of time.  The refrigerator was plugged in separately to a 110V extension cord so it was not drawing any current from the coach.
 
I began checking for the cause and I disconnected all cables and checked each battery with a load tester.  Each of them held a charge under load, although a few were at the bottom level of good/or top of the weak range.  All of the connections were replaced and tightened properly.  I looked for other obvious problems with cables and found nothing unusual.  Other than the things you can't shut off, such as the smoke and propane detectors, nothing was on to use either 12V or 120V power.

I started the generator and fully charged the batteries (13.8V on the CMP) and according to the Magnum Remote, they were at 13.2V when I turned off the generator.  Within a few seconds, it had dropped to 13.0V.  I checked the CMP and it showed no amp draw.  I switched off both the chassis and coach battery switches in the battery bay to eliminate any obvious draw on the batteries.  At one hour I turned on the switches to check the battery state on the Magnum remote and the battery voltage had dropped to 12.6V.  I checked again in two hours and it remained at 12.6V.  For the next hour I left the house battery switch on.  At the end of three house it has dropped to 12.4V.   With my previous flooded Trojan batteries, I would only drop a few tenths of a volt overnight.

I have already checked other posts on this forum along with other sites on the internet to see if there was anything that would shed some light on the issue.  So far, I am at a loss.

Does anyone have any suggested protocol for troubleshooting the problem?  I am pretty frustrated at this point. 

[Bill Lampkin]

Get a small clamp on ammeter for DC like this and see what the load is on the battery cable that goes to the load  (+ or-, doesn't matter.) Your inverter, even if 'off', will draw power from your batteries.

https://www.amazon.com/Uni-T-B4Q094-UT210E-Current-Capacitance/dp/B00O1Q2HOQ/ref=zg_bs_5011680011_6?_encoding=UTF8&psc=1&refRID=XDAKC2RF78CSQZNNTZVX

One thing about lead acid batteries is that the absorption phase of charging takes many hours. First is bulk charging, that gets you to about 80%, then the absorption phase starts and can take many more hours to reach the next stage of charging, 'float'.

Batteries always seem to disappoint. Good luck in your hunt for your parasitic loads.

[JimNCheryl Domenoe]

Thanks for the tip.  I know that batteries are a source of frustration but we can't live without them. I will continue the hunt.

[Gene Obie]

Sounds like maybe they were not fully charged. I would check the charge current before you turn off the generator. Lifeline manual indicates fully charged when rate drops below .5%. If you have more than about RatedCapacity/20  (30A assuming 3 banks of 200Ahr batteries for example) you are still in absorption charge and need to charge longer. Fully charged current should be <3A according to Lifeline manual.

Did you check bulk charge current and time setting on your charger? See section 5.4 of lifeline manual. https://centexbatteries.com/techmanual.pdf

[Bill Lampkin]

One other thing, using voltage to determine battery charge level is a bit problematic, as battery under test should be isolated and under no load (at rest) for a couple of hours before testing. Batteries in our motohomes are never 'at rest' as parasitic loads always exist (inverter, propane/smoke detector, TV amp, LP gas solenoid valve, etc). So a rapid drop in battery voltage, especially when displayed on a coach monitoring system, (which itself is another parasitic load) is expected.

Ain't nothin' easy about batteries!

[Eric Maclean]

Jim
I believe Gene is on the right track if after the batteries where charged and sat disconnected for a period of time the standing voltage dropped to 12.6 ( which is just above a 50% state of charge it would appear that the batteries had not reached a full charge .
The standing voltage can be read after 30 minutes ( disconnected) without a charge or discharge current and on a fully charged battery should read in or around 13.2 volts the reading you get right after the charger is turned off is what is known as a surface charge and will deminish with time as you witnessed.
If after allowing the charger to run its full coarse you don't get to that 13.2 volt standing voltage there are three possible problems either the final charge voltages are set too low or there is a volt drop between the inverter charger and the batteries ( cable problems bad connection or corrosion) allowing the chargers  end of the cables to reach the set voltage without charging the batteries fully or finally the batteries are done.
As your batteries are fairly new I would look for set voltage problems or a volt drop when charging.

The best way to test for the proper voltages is with a digital volt meter compare the voltage at the batteries while charging to the voltage at the chargers output ( and or against the Magnum remote readout.

At 12.6 volts the batteries are very close to there 50% charge point which for our usages is effectively dead as you don't want to utilize the bottom half of the batteries capacity because this will drastically shorten the batteries life expectancy.

Sorry for the long rely hope this helps
Eric

[Bill Lampkin]

State of charge voltage table for AGM batteries: 12.6v is pretty much a full charge. See attached:


https://i2.wp.com/www.compactrv.net/wp-content/uploads/2020/10/battery-soc-percentage3.jpg?w=730&ssl=1

[Gene Obie]

From Lifeline website you should be at 13.0 V if full charged. Also, Lifeline manual states the bulk charge current should be at least .2C for best battery life and capacity. So if you have 3 banks of 225Ahr battery your charger should be capable of 135A. In any case, I think it's important to look at your charge current a few times during the charging cycle to see how it behaves. Once your charger reaches the "Absorption" phase it keeps the voltage constant and the battery just takes whatever current it needs. Until current drops to the "termination" current in the Lifeline spec they are not fully charged.

https://lifelinebatteries.com/knowledge-center/faq/

[Chuck Jackson]

You might want to check with Lifeline on the settings. When I was looking to replace my lead acid batteries with AGMs, other forums had quite a bit of chatter about Lifeline changing their requirements so that the AGM option in the Magnum remote was not the latest recommendation by Lifeline. This was the case for my Crown batteries so I had to use the ‘Custom’ option.

[Eric Maclean]

Jim
Sorry for the confusion I was giving numbers for lead acid batteries.
But from what I can tell even with The batteries you have 12.6 is only an 80% charge meaning that either the batteries had not fully charged because they. Weren't given enough time or the charge profile was not doing the job .
 again there may be a volt drop between batteries and charger volt sensing .if 13 volts standing is a full charge and your Magnum is showing 13.2 at the end of it's charge cycle which would seem right the real question now is
 A) is that the real battery voltage at the battery bank or is that just what the Magnum charger is  sensing at the charger output.
 B)is the Magnum charge profile allowing enough time at this voltage to top charge ( or saturate) the battery bank.
Either way it appears your only getting an 80% charge as is.

Eric

[Eric Maclean]

Chuck
For curiosity sake do you remember what the numbers where for your crown batteries?

[Chuck Jackson]

Chuck
For curiosity sake do you remember what the numbers where for your crown batteries?

Bulk         —> 14.64
Absorption—>14.52 (no control for this)
Float        —> 13.2

[Eric Maclean]

Chuck
By looking at those numbers it would appear they are working with a fairly aggressive bulk charge amperage to maintain the 14.65 v and little to no float charge at 13.2 v to keep from overcharging at the latter stages of the charge cycle I guess the question is at what point ( amperage draw) do they decide to ram down from bulk charge on down to float and does the battery get enough charge before the ram down.
My guess is the Magnum AGM profile is set to ramp down too early and that's why Crown battery suggested for you to modify the charge profile using the custom setup.

Seeing as the changed amperage goes down as the battery gains charge at any given voltage it would appear that the Magnum unit moves away from the bulk charge at or about the point where the charge amperage has dropped to set amperage set as part of the algoriythum

It would be my guess that by raising the bulk charge voltage it helps move this set point a little higher in the charge algoriythum effectively charging the battery to a higher percentage in the  bulk  charge portion of the charge cycle so that less is left to the absorption charge which is likely set at a lower voltage and therefore less effective.

I think at this point a call to the battery manufacture for there recommendation on custom charge profile would be in order.
Eric

[JimNCheryl Domenoe]

Thanks for the insight.  I will call Lifeline for their recommended settings.  In the meantime, my generator has stopped running with a 36 fault code, and the Hurricane won't stay running and keeps flaming out.  Both were serviced within the past 12 months, so I am really getting dejected. Might be time to look for a newer coach.

Jim

[Chuck Jackson]

Fault code 36 is fuel related....how much fuel is in your tank?