House Batteries - low voltage alarm on inverter...

[WhereisFranklin]

Ok electrical gurus...
I'm having low voltage issues with my battery bank.
4 x 100amp AGM in series/ parallel to deliver 24v
About 4-5 years old
3 . Never discharged under 50% and more likely 60% most times
4.Problem free until this trip...HOWEVER, I did leave them unattended after 2018 trip for about 4-5 months. They finished the trip fully charged. The battery monitor showed good levels of charge but I think it had a glitch from lack of cycling and wasn't reading correctly.
Inverter has indicated low voltage alarm twice. Once on this trip (today) and once on a short trip a couple of months ago. After the short trip I bought battery charge up and reset battery meter.
Yesterday, batteries went to FLOAT (first time since realising problem a while back) but this morning had low voltage alarm. Battery % at around 65% capacity.
The induction cooker we run from the inverter normally draws about 30 amps on the appropriate setting. It was pulling 53 at the lower voltage!
I'm struggling to understand how batteries at 65% can show low voltage and why I wouldn't be able to use more of the remaining capacity without having low voltage issues.

Thanks for any feedback. Neil

 

[dwh]

Battery % at around 65% capacity.

That sounds like a false assumption to me...

If you didn't do a full-charge then full drain @20hr rate load test, you have no idea what the capacity is...so 65% of <unknown> equals what? Unknown.

You reset the battery meter. What is it? Amp counter? So you would have had to tell it the bank size. What did you tell it? 200ah?

After 4.5 years, and feeding induction cooking and then sitting around sulphating for a few months...there is no way that bank has a 200ah capacity.

I'm struggling to understand how batteries at 65% can show low voltage and why I wouldn't be able to use more of the remaining capacity without having low voltage issues.

Most likely they aren't at 65%. With the meter reset, do a full drain with a small load to 10.5v, then a full recharge. It's not a proper capacity test, but at least the amp counter should give you a ballpark on how many ah it took to recharge the bank. There's your new capacity baseline.

 

[john61ct]

4-5 years is a good run, replace the batteries.

And get a better handle on their SoC, next set may last longer.

What batteries?

Can't trust most charge source indicators, most go to Float way too early.

How do you judge 50% vs 60% to stop drawing?

 

[WhereisFranklin]

Ok. Enerdrive e-lite battery monitor. All negative feeds through shunt. Monitor covers voltage, amps,amp hrs and gives %. Initial calibration via float indicator on Morningstar MPPT solar controller.

At float, I manually synchronised the meter effectively telling it that the battery capacity was at 100%.

The 50% limit is represented by a tapering bar graph from left to right and also by readjng the % display. This is set at half of the bank capacity, which in my case is 100 amps being a 200 amp pack at 24v.

Further investigation required re actual amps remaining. Thanks for suggestions..

 

[67cj5]

Ok electrical gurus...
I'm having low voltage issues with my battery bank.
4 x 100amp AGM in series/ parallel to deliver 24v
About 4-5 years old
3 . Never discharged under 50% and more likely 60% most times
4.Problem free until this trip...HOWEVER, I did leave them unattended after 2018 trip for about 4-5 months. They finished the trip fully charged. The battery monitor showed good levels of charge but I think it had a glitch from lack of cycling and wasn't reading correctly.
Inverter has indicated low voltage alarm twice. Once on this trip (today) and once on a short trip a couple of months ago. After the short trip I bought battery charge up and reset battery meter.
Yesterday, batteries went to FLOAT (first time since realising problem a while back) but this morning had low voltage alarm. Battery % at around 65% capacity.
The induction cooker we run from the inverter normally draws about 30 amps on the appropriate setting. It was pulling 53 at the lower voltage!
I'm struggling to understand how batteries at 65% can show low voltage and why I wouldn't be able to use more of the remaining capacity without having low voltage issues.

Thanks for any feedback. Neil

Sounds like you need to get a decent Charger and fully charger each battery then run the repair mode, I had to do that with one of mine because I used a powerful workshop type charger and when it got close to being fully charged it started to put over 15.5 to 16v in to the battery, Trouble is when it does that it went from an 800cca/1000mca down to a 370cca, Luckily a new Charger got it back up to 730+cca and rising.

Don't ever let an inverter take the battery down low enough to make the Alarm go off because the Alarm does not strictly come on at 10.5v and quite often they come on at around 9.8v and below, I did that about 3 or 4 times to a 65A/H battery and it was ruined within 3 weeks of me getting it,

Those cut off Alarms are stupid things because they need to cut out above 12v because at 12v a battery is considered flat when it reaches 12v. you need to fit a higher voltage shut off or this could end up costing you big bucks in the long run,

I bought 3 new Charger and for once in my life all of my batteries are in peak condition.

Hope that helps.

 

[john61ct]

Ok. Enerdrive e-lite battery monitor. All negative feeds through shunt. Monitor covers voltage, amps,amp hrs and gives %. Initial calibration via float indicator on Morningstar MPPT solar controller.

At float, I manually synchronised the meter effectively telling it that the battery capacity was at 100%.

Wrong way around.

You only know that bank is at 100% Full, by holding Absorb V until amps current tapers to .005C, or whatever the bank mfg specs.

So half an amp per 100Ah capacity.

Charge sources need to have AHT extended until they're getting it right automatically most days, by default will be going to Float way prematurely.

Do the 100% reset on the coulomb counter as often as possible, and yes manually.

 

[jonyjoe101]

With solar you never get 100 percent on lead acid, they always go to float too early. I leave my charge controller float setting at the highest setting. But the bad thing is voltage drop. You need to measure voltage at battery terminals and match that with what your controller shows. I had a .5 volt difference for years, I had to raise the bulk on the controller by .5 volts to compensate. I was basically float charging the batteries for years because of the voltage drop.

To me it sounds like your batteries where chronically undercharge for years and it finally caught up to them. Mine was like that , it lasted years at small loads but once I started adding large loads they proved not to be able to handle it. I was surprise because I thought I took good care of them.