Sealed gel lead acid dead after a year.

Yerf · October 2017

Hey

So I have 24 x 2v 3000 ah sealed lead acid gel batteries. They are a year old and don't hold any charge. One of they recently blew up and I replaced it but they still don't hold charge. How can the whole bank be dead in a year? Any ideas? I seperated each battery and left it for a day and measured each battery. I've attached each batteries voltages. 48v battery bank individually measured https://imgur.com/gallery/X940F

mcgivor · October 2017

Can you let us know exactly what batteries they are, picture? , what charging source was used, voltage /current setpoints and so forth, as much information as possible. Initially without knowing any details, the fact one blew up may indicate over charging, but that's a shot in the dark.

Yerf · October 2017

These are the batteries in the picture. They are open from China. I use a victron 150/70 charge controller to charge them. The charger controller is set to default charging algorithm which is for sealed gel lead acid batteries.

mcgivor · October 2017

There are various default settings set by a rotary switch, which setting did you use? What is the array size and configuration, total watts and input voltage? These are important to determine what went wrong, a make and model, or a link th the battery would be helpful, to establish what batteries they actually are, the picture provided is of little help.

Yerf · October 2017

Hi

The settings are algorithm 2 which are absorption 57,6 V float 55,2 v

The solar array is around 100 V and 300 amps seperated into 5 charge controllers.

Sorry but the batteries were bought from https://just.m.en.alibaba.com

Nothing on there about the specific model.

Photowhit · October 2017

That is a huge battery. What was the load? How far were you drawing them down?

Are you sure it's a gelled battery? Sometimes people get confused with Absorbed Glass Mat (AGM) batteries.

Regular deep rapid discharging is not the best use of gel batteries. They don't do rapid discharges well. They also must be charged at a lower rate than AGM batteries. Usually at 1/16th to 1/20th of their capacity, not a good choice if you are deeply discharging them as solar might not offer enough time to totally recharge them and then require the array to be angled in separate directions to allow a longer charging time.

You have 30,000 watts of array so 30,000/48=625, or more realistic charge rate of 75% of that or 468 amps or 15% of the battery capacity. About 2.5 - 3x the normal charging rate for a 3000 amp hour gelled battery.

Here is some generic information about Gel batteries, hopefully you can get more information from the manufacturer.

https://www.solar-electric.com/learning-center/batteries-and-charging/deep-cycle-battery-faq.html#Gelled Electrolyte

Estragon · October 2017

According to the first image, cell voltages range from ~2.07 to 2.25, which would be equivalent to ~12.4 to 13.5v in a 12v nominal battery.

You said these readings were taken after the bank was separated for a day, which I'm confused about. The readings suggest states of charge ranging from about 70%SOC to around float voltage. Were they being charged after being separated?

Yerf · October 2017

> @Estragon said:
> According to the first image, cell voltages range from ~2.07 to 2.25, which would be equivalent to ~12.4 to 13.5v in a 12v nominal battery.
>
> You said these readings were taken after the bank was separated for a day, which I'm confused about. The readings suggest states of charge ranging from about 70%SOC to around float voltage. Were they being charged after being separated?

No they weren't charged after being seperated. I am suspicious that the high voltage readings mean the batteries have a short circuit.

According to bmv 702 battery monitor the soc never went below 80%

The batteries were oversized due to future expansion in electricity needs. They are definitely deep cycles gel batteries.

Thanks for all your input

Yerf · October 2017

> @Photowhit said:
> That is a huge battery. What was the load? How far were you drawing them down?
>
> Are you sure it's a gelled battery? Sometimes people get confused with Absorbed Glass Mat (AGM) batteries.
>
> Regular deep rapid discharging is not the best use of gel batteries. They don't do rapid discharges well. They also must be charged at a lower rate than AGM batteries. Usually at 1/16th to 1/20th of their capacity, not a good choice if you are deeply discharging them as solar might not offer enough time to totally recharge them and then require the array to be angled in separate directions to allow a longer charging time.
>
> You have 30,000 watts of array so 30,000/48=625, or more realistic charge rate of 75% of that or 468 amps or 15% of the battery capacity. About 2.5 - 3x the normal charging rate for a 3000 amp hour gelled battery.
>
> Here is some generic information about Gel batteries, hopefully you can get more information from the manufacturer.
>
> https://www.solar-electric.com/learning-center/batteries-and-charging/deep-cycle-battery-faq.html#Gelled Electrolyte

The batteries were oversized for our needs. Although we have 3 x 10000 quattro inverters connected the battery soc never went below 80%.

Also never saw the charge current higher than 300 amps. Mostly around 100 amps.

Estragon · October 2017

> @Yerf said:
> > @Estragon said:
> > According to the first image, cell voltages range from ~2.07 to 2.25, which would be equivalent to ~12.4 to 13.5v in a 12v nominal battery.
> >
> > You said these readings were taken after the bank was separated for a day, which I'm confused about. The readings suggest states of charge ranging from about 70%SOC to around float voltage. Were they being charged after being separated?
>
> No they weren't charged after being seperated. I am suspicious that the high voltage readings mean the batteries have a short circuit.
>
> According to bmv 702 battery monitor the soc never went below 80%

I don't think an internal short would cause resting voltage to be high, but others may be able to comment on this.

Do the suspect cells get hot when charging?

The battery monitor can, at best, tell the approximate state of charge for the bank as a whole. It appears there are significant variations in SOC between cells in your bank though. There are lots of variables that can confuse even the best SOC monitors. Mine can get out of whack after a few days of partial charging and discharging.

Yerf · October 2017

> @Estragon said:
> > @Yerf said:
> > > @Estragon said:
> > > According to the first image, cell voltages range from ~2.07 to 2.25, which would be equivalent to ~12.4 to 13.5v in a 12v nominal battery.
> > >
> > > You said these readings were taken after the bank was separated for a day, which I'm confused about. The readings suggest states of charge ranging from about 70%SOC to around float voltage. Were they being charged after being separated?
> >
> > No they weren't charged after being seperated. I am suspicious that the high voltage readings mean the batteries have a short circuit.
> >
> > According to bmv 702 battery monitor the soc never went below 80%
>
> I don't think an internal short would cause resting voltage to be high, but others may be able to comment on this.
>
> Do the suspect cells get hot when charging?
>
> The battery monitor can, at best, tell the approximate state of charge for the bank as a whole. It appears there are significant variations in SOC between cells in your bank though. There are lots of variables that can confuse even the best SOC monitors. Mine can get out of whack after a few days of partial charging and discharging.

Didn't notice any heat.

Sealed gel lead acid dead after a year.

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