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diy solar

will a dead battery in series damage the others?

SolarSamSurfer

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Apr 24, 2022
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i have 4x 12v batteries in series to make a 48v battery, one of them is dead. is it safe to use my system until i replace the dead one or do i need to turn it off until i replace it?
 
How could you attempt to keep using the system if there is no voltage getting across the series string of batteries?

What voltage do you measure across the series string? With a dead battery you are likely getting 0V or maybe just a few. You certainly won't be getting anywhere near 48V anymore.
 
How could you attempt to keep using the system if there is no voltage getting across the series string of batteries?

What voltage do you measure across the series string? With a dead battery you are likely getting 0V or maybe just a few. You certainly won't be getting anywhere near 48V anymore.
Define dead? What type of batteries?
they are lead acid 205AH 12V wired with 6AWG ive made the test for the batteries. when the inverter was fully charged in float mode 56V
1-12.5 2-14.85 3-14.60 4-14.47
after disconnecting them and waiting 30 mins
1-11 2-13.2 3-13.5 4-13.4
C.V. 58.4v Float 54v
battery 1 and 2 was bought 11 months and and connected 6 months ago, battery 3 is 2 weeks old and battery 4 is 4 months old.

i have noticed in the afternoon when that batteries are fully charge and if my fridge turns off in the afternoon the growatt doesnt get to lower input from panals because batteries are full and theres a low load now and i see the voltage jumps back up and changes between 56-59 for a few hours.
I might just need to balance them if im lucky but i believe number one isnt holding voltage.

I Have a growatt that has settings to balance lead acid batteries that i have just learnt about, if anyone has recommendations for the settings it be great help. I can program them for equalization Voltage (default 58.4V), Battery equalized time (5min-900min), Battery equalized timeout (5min-900min), Equalization interval (1-90days), Equalization activated immediately "If equalization function is enabled in program 43, this program can be setup. If “On” is selected in this program, it’s to activate battery equalization immediately and LCD main page will shows ”. If “Off” is selected, it will cancel equalization function until next activated equalization time arrives based on program 47setting. At this time, “ ” will not be shown in LCD main page."
 
What voltage do you read for the series as a whole? Put one lead on the first battery and the other on the last battery.
 
What voltage do you read for the series as a whole? Put one lead on the first battery and the other on the last battery.
Right now its dark so they are not in Float any more but its reading 48.1v with the meter same as the growatt display
 
Looks like a bad/shorted cell. AFAIK, the biggest risk to the batteries in continuing to run it is overcharge. If you really need to keep it going, I'd recalculate your settings for one cell less until you get a proper replacement.

OTOH, if it's an equalization issue, putting a 12V charger across the low cell may be a safer option for the string than equalization to bring it up. AFAIK, there's no issue with a 110V charger feeding that battery from your inverter.
 
Looks like a bad/shorted cell. AFAIK, the biggest risk to the batteries in continuing to run it is overcharge. If you really need to keep it going, I'd recalculate your settings for one cell less until you get a proper replacement.

OTOH, if it's an equalization issue, putting a 12V charger across the low cell may be a safer option for the string than equalization to bring it up. AFAIK, there's no issue with a 110V charger feeding that battery from your inverter.
do you have a recommendation for the settings then? i can change the Bulk charge voltage its 58.4v now also float is 54v.

to confirm your saying i can plug charger into my mains and charge the battery that is lower while its still connected in series feeding the inverter?

I have a feeling the battery is not holding voltage because it dropped to 11 as soon i disconnected the system
 
Are these FLA or SLAs? I would attempt an individual charge and test of that suspect battery, out of series. If FLA, did you check electrolyte levels? At this point it could have been a bad connection and the battery wasnt absorbing as much charge as the others. If FLA, equalization might revive if it sulphated. If SLA, sounds like you're SOL, or prorated warranty.

Regardless, individually charging the battery to 14.4V, check resting voltage, and putting under load will tell you whether the battery is holding charge. No you can't do this while it's still powering your inverter. At least not the charge and rest part.
 
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Are these FLA or SLAs? I would attempt an individual charge and test of that suspect battery, out of series. If FLA, did you check electrolyte levels? At this point it could have been a bad connection and the battery wasnt absorbing as much charge as the others. If FLA, equalization might revive if it sulphated. If SLA, sounds like you're SOL, or prorated warranty.
how can i find out if they are FLA or SLA? yes they have enough liquid
 
i had the same problem with another battery 2 weeks ago but changed it and now its happened again 2 weeks i think i have something set up wrong
 
Lol, if you popped a top to check electrolyte levels, then they must be FLA (flooded lead acid). There may be hope. You're gonna have to take that battery out of service to charge, rest, check, and test it. Reread my previous post. I edited it.
 
Lol, if you popped a top to check electrolyte levels, then they must be FLA (flooded lead acid). There may be hope. You're gonna have to take that battery out of service to charge, rest, check, and test it. Reread my previous post. I edited it.
ok thanks i thought it was obvious we are talking about flood lead acid because where in the lead acid forum. guess i learnt there's two types of lead acid batteries. will a car battery charger work or do i need a special solar one?
 
SLA is sealed lead acid (agm, gel).

Do you have a hydrometer?

If these batteries arent the same age, they may not charge at the same rate. You might need a balancer/equalizer, but we'll get to that later. If it's not been getting full charge, it probably sulfated. You'll need to run an equalization (not to be confused with equalizer) cycle on it, but again, we'll get to that later.

Charge, rest, check, test.

Do you have a 12v charger?
 
No i dont, I will have to take it to a local mechanic tomorrow do i need to take all 4 to charge to 14.4 or just the one im having issues with. No i dont have a hydrometer. They arent the same age because ive had 4 break in the 6 months ive had the system. 2 at the first week changed with warrenty, 1 of the replaced ones broke after another 3 months. The one im having issues ive had since the beginning. I have equalization settings on the growatt but they are turned off. Do you think the default settings will be fine?
 
No i dont, I will have to take it to a local mechanic tomorrow do i need to take all 4 to charge to 14.4 or just the one im having issues with. No i dont have a hydrometer. They arent the same age because ive had 4 break in the 6 months ive had the system. 2 at the first week changed with warrenty, 1 of the replaced ones broke after another 3 months. The one im having issues ive had since the beginning. I have equalization settings on the growatt but they are turned off. Do you think the default settings will be fine?
Don't change anything, at this point. You need to understand what you're doing, first.

If you're going to use FLA batteries you need to learn how to care for and maintain them. Otherwise you're going to continue having problems. You do realize this is a DIY forum, right?
 
FLA batteries like to stay charged. FLA batteries don't like to be discharged more than 50%. FLA batteries need to be recharged right away to prevent sulfate build-up, which is damaging to LA batteries.

If FLA have sulfated, they can be processed through an equalization cycle. This is controlled over-charging. It burns off the sulfate to hopefully revive, rejuvenate a sulfated battery.

I do not recommend doing this at 48V with 4 series-connected LA batteries of different ages.

Next step is learning how to run an equalization cycle and acquiring the tools to do it.
 
Yes it appears to be there are now 3x 12 volt and 1x 10 volt batteries. Drop the absorption and float by 2 volts each until the replacement is procured.

Once installed start shopping for a 48 volt LFP replacement battery. Or even better, build one.
 
Yes it appears to be there are now 3x 12 volt and 1x 10 volt batteries. Drop the absorption and float by 2 volts each until the replacement is procured.

Once installed start shopping for a 48 volt LFP replacement battery. Or even better, build one.
He just needs to buy a 48V battery. I sense he isn't interested in DIY.
 
Yes i realize this is a DIY forum thats why im here. I have been monitoring the batteries since the beginning and only had problems after 4 months and im now going through the journey of finding out the problem and solving it!
 
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