Is My AGM Battery Kaput?

manyman297
manyman297 Member Posts: 1,433
edited May 2024 in Battery/Electrical & Solar
The last couple of trips last year I had issues with it seeming to discharge faster than usual but I chalked it up to cloudy skies.  

We're on a short trip right now. First day/night was fine. Battery discharged to about 75% by the next morning. Solar got it back up to 93%...ended last night at around 77%. This is pretty normal for us. 

Early this morning we get a "low battery" warning on the Alde. Sure enough the voltage on the battery was 10.5v. 

What I also noticed is the percentage displayed was still 70%. I remember playing with some setting in the smart shunt last year but what would cause such a discrepancy between voltage and percentage. By voltage my battery was at 0% practically but it showed 70%.

One last note..right now it's magically back up to 100% and 13.1v. The low battery warning came on 4 hours ago at 5am. 

While my stomach tells me I need new batteries how can I be sure these batteries are truly done? 
2021 400 BD
2020 Tacoma TRD Off-Road 
· Share on FacebookShare on Twitter Share on Google+

Comments

  • manyman297
    manyman297 Member Posts: 1,433
    You can see there was a massive drop in voltage at 3:30am. When I check the amp and power graphs there’s no spike in usage. So the batteries just lost voltage for some reason?


    2021 400 BD
    2020 Tacoma TRD Off-Road 
    · Share on FacebookShare on Twitter Share on Google+
  • Grumpy_G
    Grumpy_G Member Posts: 722
    The battery is likely done for. AGM batteries have the nasty habit of rapidly deteriorating at the end of their life span. I had that happen with vehicles where I drove it one day, the next day it wouldn't crank.
    You can test the battery by putting a large load on it when it is supposedly fully charged and measure the voltage at the battery. E.g. use the inverter with a 100W incandescent light. The inverter either turns off immediately or within a short time.
    · Share on FacebookShare on Twitter Share on Google+
  • manyman297
    manyman297 Member Posts: 1,433
    Yeah, I'm thinking something is wrong with the cells. Everything was fine until early this morning. I'll test the batteries. I guess moving to lithium isn't the end of the world. 
    2021 400 BD
    2020 Tacoma TRD Off-Road 
    · Share on FacebookShare on Twitter Share on Google+
  • marleecamps
    marleecamps Member Posts: 179
    I also have a 2021 400BD and noticed my batteries struggling to keep up last fall during an extended trip with several days off grid.  Swapped out the 2 AGM batteries for a single 200 ah lithium battery this spring.  Freed up nearly 100 pounds of weight in the process. 
    --Marlee
    2021 Tab400 Boondock; TV 2025 Jeep Grand Cherokee Limited; Minnesota
    · Share on FacebookShare on Twitter Share on Google+
  • ColoradoSun
    ColoradoSun Member Posts: 135
    We also have a 2021 T@B 400 BD with the original AGM batteries. So far I haven't noticed any battery degradation and we just completed a three night camp off grid. I know the good times can't last forever so I'm interested in what happens next.
    2021 T@B 400 BD, 2020 Toyota Tacoma Double Cab
    SW Colorado
    · Share on FacebookShare on Twitter Share on Google+
  • manyman297
    manyman297 Member Posts: 1,433
    Yeah, I’m looking into the LiTime 230Ah battery.  I can’t justify the battle born ones as we may not keep our trailer past next year. But I think having any lithium in the trailer is a good selling point and it would double our capacity for $600 or so bucks.
    2021 400 BD
    2020 Tacoma TRD Off-Road 
    · Share on FacebookShare on Twitter Share on Google+
  • TomCanada
    TomCanada Member Posts: 294
    Just had the dreaded AGM.issue hit while on a trip.  Battery would quickly drop from 12.5V to around 10.5V when around 85% SoC and under 2-3A load.  Sounds like we need to replace. Does the controller in our unit adequately support lithium?  The Victron solar charger and BMV should be ok themselves. 
    · Share on FacebookShare on Twitter Share on Google+
  • pthomas745
    pthomas745 Administrator, Moderator Posts: 4,542
    What does your battery show under "no loads" and not charging?  How old are these batteries? This is a photo of my older lead acid battery.  On the left, the fan is running at a very slow speed.  Note the voltage is 12.01, which puts it at about 50 percent capacity.  On the right, with the battery switch off, the "rested" reading after only 10 minutes shows 12.46, or about 70 percent capacity.  A 2 or 3 amp load would have the voltage numbers even lower.  Voltage under load is not useful for battery capacity.
    Depending on the year: the converter in the trailer can, at least, bring a lithium battery to 'around" 85 percent of charge.  The solar controller can be configured for lithium charging.


    2017 Outback
    Towed by 2014 Touareg TDi
    · Share on FacebookShare on Twitter Share on Google+
  • morey000
    morey000 Member Posts: 162
    manyman297 said:
    Yeah, I’m looking into the LiTime 230Ah battery.  I can’t justify the battle born ones as we may not keep our trailer past next year. But I think having any lithium in the trailer is a good selling point and it would double our capacity for $600 or so bucks.
    A lead acid/AGM battery, you can only use half of it, and most don't meet their spec AHr.  Lithium you can use it all.  The LiTime batteries are good quality.  Don't hesitate.  
    Silver on Silver, 320S '19 Outback
    · Share on FacebookShare on Twitter Share on Google+

Categories