My AGM battery is never getting charged with more than 12Amps in my RV solar setup.

[flajsdl]

A sudden drop to 10.8ish v is almost always a sign of a dead cell. The other 5 cells may still be working perfectly fine, and 10.8v is enough for non-sensitive loads, like lights. I have a few old batteries with bad cells I'm keeping for outdoor lights (with a buck converter to 3.5v LEDs). I wouldn't use an expensive charge controller on them as they may damage it(?), but they can still be useful for some things. It sounds like you got a few good years out of it despite not having enough solar to charge it properly. If you had hooked it to an AC charger, just once a month, it probably would have greatly prolonged it's life.

What the heck is a LB?

LB is leisure battery.

I got 2 years and 4 months of full-time use out of it.

I think this is how I messed up.. During summer while parked partially in the shade, using my water cooker a few times in the evening, then in the morning while not paying attention to the BM1 and MT50 displays anymore. I got lazy. There was full sun all day long anyway and the display never showed values lower than 12.8v, 12.7v at the end of the night so what gives?

Yet, suddenly (to me) the Victron shut off all power and the display read 10.6v. This happened a few times. I suspect that if I hadn't used the watercooker without paying attention to the battery SoC, it would still be okay (aside from the systematic undercharging). But that's in hindsight.

 

[flajsdl]

If you had hooked it to an AC charger, just once a month, it probably would have greatly prolonged it's life.

Just going to a campsite and hooking it up to electric point is sufficient? Or use a dedicated charger that can charge it with say 25 amps?

The vendor of the battery told me that when the battery is quite empty the Victron adjusts its current or something and a dedicated charger is needed to fully charge the battery. I don't know what to make of this as I'd never heard it before. Does make sense in a way though that a dedicated charger is better at fully charging a battery than just hooking the Victron Multiplus up to shore power.

 

[RandyP]

Here's some specific info on Lifeline AGM deep cycle batteries. Very detailed CONDITIONING info is given in section 5.5 .
I suspect that all good AGM deep cycle batteries have similarly detailed info from the manufacturer.
Many people may not know that conditioning an AGM battery that is repeatedly discharged and not returned to 100 SOC at each charge cycle is required to maintain the batteries design life.

https://lifelinebatteries.com/wp-content/uploads/2015/12/6-0101F-Lifeline-Technical-Manual-Final-5-06-19.pdf

 

[Ped]

Might be a solution for me. I need something that pumps almost 100Ah back into the LB within a day at most, preferably in less time.

In hindsight it seems like getting an AGM battery was a bad choice anyway since I'm a fulltime RVer and solely charge my LB with solar. Meaning I never charge it with EHU. Also my RV alternator is 3 decades old and doesn't put in much amps either.

Of course the vendor didn't tell me this and I recently read that AGM's need a proper charge via electric hookup at least every two weeks or so to combat systematic undercharging as they cannot be charged fully with solar alone.

Yeah but boost charging to saturation voltage will get them there with solar the rest of the way in my tests. Still might take 4hrs give or take though.

Idk if youre aware but you will fry an alternator if you hook it up to a lifepo4 supposedly. Although I put one in my motorcycle 6 years ago and never had a problem.

 

[Ped]

Here's some specific info on Lifeline AGM deep cycle batteries. Very detailed CONDITIONING info is given in section 5.5 .
I suspect that all good AGM deep cycle batteries have similarly detailed info from the manufacturer.
Many people may not know that conditioning an AGM battery that is repeatedly discharged and not returned to 100 SOC at each charge cycle is required to maintain the batteries designed life.

https://lifelinebatteries.com/wp-content/uploads/2015/12/6-0101F-Lifeline-Technical-Manual-Final-5-06-19.pdf

There was an arguement in another thread about just that yesterday. I posted same manual as you. I think difference is AGM is as needed NOT monthly.

 

[RandyP]

There was an arguement in another thread about just that yesterday. I posted same manual as you. I think difference is AGM is as needed NOT monthly.

hard to argue with the battery makers technical manual directions.

 

[RandyP]

A LiFePO4 battery can be charged at bulk charge rate to 100% SOC. Therefore charges in less time than an agm with the same solar cell power and controller rating (the solar controler does need to be setup for LiFePO4 battery charging regiment).
A LiFePO4 battery does not need to be charged to 100% SOC ever, if you choose to use it that way. Runningthe battery at 80%SOC to 20% SOC is better for the battery than charging to 100% SOC each charge cycle. And you can store a LiFePO4 battery at 50% SOC for the winter, isolated from load.
You will find that your stress caused by only partial charging AGM's will disappear after you use a LiFePO4 battery for a short time.

 

[gnubie]

hard to argue with the battery makers technical manual directions.

Sure is. Always follow manufacturer's directions for best performance. If they say don't do something, don't do it. If they don't explicitly tell you to do something, perhaps don't do it. If on the other hand they tell you to do something, do it.

For example, a chap on the forum has recently mentioned he has bought a bank of batteries arranged as 8 x 4s. The max charge voltage for them is 14.4 and this is their recommended 2 stage charge voltage. Imagine what the consequences of putting 15v or higher into them would be.

 

[RandyP]

15v charge on a 12v LiFePO4 battery will destroy the battery. Do not ever 'equalize' charge a LiFePO4 battery.

 

[RandyP]

...............
For example, a chap on the forum has recently mentioned he has bought a bank of batteries arranged as 8 x 4s. ........

Would that be 4P/4S cell config ?

 

[gnubie]

He had them arranged as 8 parallel strings of 4 in series for 48V. They are LA but have low charge / float voltages by the manufacturer's specs.

 

[SolarRat]

Just going to a campsite and hooking it up to electric point is sufficient? Or use a dedicated charger that can charge it with say 25 amps?

The vendor of the battery told me that when the battery is quite empty the Victron adjusts its current or something and a dedicated charger is needed to fully charge the battery. I don't know what to make of this as I'd never heard it before. Does make sense in a way though that a dedicated charger is better at fully charging a battery than just hooking the Victron Multiplus up to shore power.

Even a 5 amp charger will completely charge that battery, IF given enough uninterrupted time (more hours than the sun can provide). The Victron should put out 16 amps right? That's on the small side but should be fine for the 250ah battery. If 50% discharged it should easily reach full charge within 12 hours uninterrupted.

 

[RandyP]

The solar charger might put out 16A in bulk charge mode, but when it goes to absorb charge mode the ampacity will start dropping off until the battery is fully charged. AGM's require this charging protocol. It can take many, many hours to charge an AGM battery from 50% charge to 100% SOC. Longer than the sun is in the sky on a daily basis. And what happens if the battery is left at less than 100% SOC at the end of the day, it sits there and sulfate crystals start forming on the plates. So if it takes two solar days to reach 100% SOC, here is one night that it forms crystals on the plates.

 

[SolarRat]

Lots of talk here about "needing" X amount of amps to fully charge a battery is nonsense. I've used 1 amp battery tenders to fully trickle charge 105ah batteries many times (it takes a couple days) . My 3 bank 15 amp (5,5,5) marine charger charges my three 105ah 12v trolling motor batteries at only 5 amps bulk each, tapering down to zero during the roughly 5 hour absorption stage. I deplete it to 50% on the water, plug it in when I get home at night and by noon the next day it's in float mode and ready for another trip. Mine are FLAs...and from what I hear AGM's charge more efficiently...I wouldn't know first hand as I don't think they are worth the extra cost, even if they were the same price.

 

[Ped]

Lots of talk here about "needing" X amount of amps to fully charge a battery is nonsense. I've used 1 amp battery tenders to fully trickle charge 105ah batteries many times (it takes a couple days) . My 3 bank 15 amp (5,5,5) marine charger charges my three 105ah 12v trolling motor batteries at only 5 amps bulk each, tapering down to zero during the roughly 5 hour absorption stage. I deplete it to 50% on the water, plug it in when I get home at night and by noon the next day it's in float mode and ready for another trip. Mine are FLAs...and from what I hear AGM's charge more efficiently...I wouldn't know first hand as I don't think they are worth the extra cost, even if they were the same price.

What 16hrs to fill. See what it takes to get them charged within the hours of sunlight in late december while pulling a constant 5 amps average.

(Dod/100) =.5 x (105ah/5a) + 5hrs absorption = 15.5hrs...aligns pretty good with your actual results

Now take 210ah bank at 50% diacharged pulling 5 amps with 400w of solar

.5 x (210/20 - 5a load) + 3hrs absorption = 10hrs.

At no point in a year even under perfect sun can your panels output for 10hrs (at any significant rate). Let alone cloudy winter days when the sun sets at 5pm.

So minimum charge current isnt "nonsense"

 

[SolarRat]

What 16hrs to fill. See what it takes to get them charged within the hours of sunlight in late december while pulling a constant 5 amps average.

We are talking about AC chargers now, try and keep up .

 

[Ped]

We are talking about AC chargers now, try and keep up .

Well, you argued in the other thread against this reality first of all. And this is a solar forum. And everyone knows you can charge at any rate with unlimited time.

 

[SolarRat]

Well, you argued in the other thread against this reality first of all. And this is a solar forum. And everyone knows you can charge at any rate with unlimited time.

Ped, I believe I was the very first poster on this website to post the realities and downsides of charging lead acid with solar. Long before you came here and started applying those realities where it doesn't always belong. And when proven wrong you go back and edit your old posts to make it look like you were right. What are you trying to prove, that LA batteries are useless? Every damn post....sheesh, give it a rest.

 

[Ped]

Ped, I believe I was the very first poster on this website to post the realities and downsides of charging lead acid with solar. Long before you came here and started applying those realities where it doesn't always belong. And when proven wrong you go back and edit your old posts to make it look like you were right. What are you trying to prove, that LA batteries are useless? Every damn post....sheesh, give it a rest.

Sorry but you often post clearly wrong things and have yet to ever admit so such as minimum current is "nonsense."
And I edit mispelled words or grammatical errors. So youre attempt at trying to save face is another wrong. If youd leave your little ego behind youd probably learn something.

 

[gnubie]

Keep it civil please.