Deep cycle battery question

[William_H]

I have a system of security lights around the house turning on every evening for about 6 hrs charged by solar panels. The lights draw about 3 amps so about 18AHper night. Batteries have always been a bit of a problem. I bought a deep cycle battery in January. No name on the battery just Sealed Lead Acid AGM . It was sold as 130 AH. (presumably from China) It was cheap at around 100squid) What did strike me when it arrived is that it is very heavy like 25kg or so it seems. Anyway for a few months it seemed to work seamlessly. To the point where I took it for granted.
Then autumn arrived and some cloudy days. A few days back I woke to find lights quite dim. A check of voltage showed 8.8volts under load. I realised that with some cloudy days charging was probably a bit inadequate. I have fitted a VSR into the load (like this Relay Module 12V Battery Low Voltage Cut off Automatic Under voltage Switch A35 | eBay) set at around 11volts. I seemed to switch off the lights after about 2 hrs. I am sure I pumped about 30AH in from solar during the day. The voltage on charge got up around 16v. Not regulated about of desperation. I ahve crtankled up the regulated voltage and battery seems to come up to about 16v on charge relatively quickly. One might think it is fully charged but it seems to ahve a small capacity for charge.
Charging comes from 2x 160w 40v ex domestic panels located so at least one is in sun all day (a big tree in the way) It feeds a buck converter to give a regulated charge voltage. I also have a 80w 20v panel that I have used more recently unregulated to push in about 3 amps regardless of charge level.

Have I simply stuffed it through not enough charge and too much discharge over possibly some cycles? Is there any way to recover capacity ? Was it just a dud or am I the stupid one to not care for it well enough. Waht is this "equalising charge' spoken of ? No i don't have smart auto mans charger. Any comment please ol'will

 

[temptress]

Do you have any Solar charge controllers is the system? What at they?

I think you have fried the battery by pushing too much charge at too high a voltage into it AND cycling it too deeply.

Do you know the amps being put in at your 16v? 16volts is way too much for a conventional battery.

you shuld get a cheapish mppt controller , tjey can be fo8nd from form 40 quid, that will mange the charging for you.

 

[PaulRainbow]

I'd be suspicious that the battery was actually deep cycle. A "normal" battery of that ah would weigh around 25kg, a deep cycle one would be about 30kg. That said, it' s not what the problem is, the problem is, you have severely over charged the battery.

The 80w panel, on it's own, unregulated is enough to kill the battery. You say the 2x160w panels are connected to a buck converter, i assume that's just set to a particular voltage, that the battery is held at, all day, every day, regardless of state of charge, that's a battery killer too.

The under voltage relay is also set far too low, 11v is totally flat. For low voltage protection in your case, i'd set it to 12.2v.

If the lights are the only loads, i would buy a cheap leisure battery and connect the 2x160w panels to it via a cheap solar controller. No value in spending the extra on a MPPT controller here as those two panels are way more than would be needed.

Equalisation is used to de-sulphate the plates, it should be used with care on sealed batteries though.

 

[lw395]

I have a system of security lights around the house turning on every evening for about 6 hrs charged by solar panels. The lights draw about 3 amps so about 18AHper night. Batteries have always been a bit of a problem. I bought a deep cycle battery in January. No name on the battery just Sealed Lead Acid AGM . It was sold as 130 AH. (presumably from China) It was cheap at around 100squid) What did strike me when it arrived is that it is very heavy like 25kg or so it seems. Anyway for a few months it seemed to work seamlessly. To the point where I took it for granted.
Then autumn arrived and some cloudy days. A few days back I woke to find lights quite dim. A check of voltage showed 8.8volts under load. I realised that with some cloudy days charging was probably a bit inadequate. I have fitted a VSR into the load (like this Relay Module 12V Battery Low Voltage Cut off Automatic Under voltage Switch A35 | eBay) set at around 11volts. I seemed to switch off the lights after about 2 hrs. I am sure I pumped about 30AH in from solar during the day. The voltage on charge got up around 16v. Not regulated about of desperation. I ahve crtankled up the regulated voltage and battery seems to come up to about 16v on charge relatively quickly. One might think it is fully charged but it seems to ahve a small capacity for charge.
Charging comes from 2x 160w 40v ex domestic panels located so at least one is in sun all day (a big tree in the way) It feeds a buck converter to give a regulated charge voltage. I also have a 80w 20v panel that I have used more recently unregulated to push in about 3 amps regardless of charge level.

Have I simply stuffed it through not enough charge and too much discharge over possibly some cycles? Is there any way to recover capacity ? Was it just a dud or am I the stupid one to not care for it well enough. Waht is this "equalising charge' spoken of ? No i don't have smart auto mans charger. Any comment please ol'will

In my view, you may, or may not have killed the battery.
Best thing would be to check electrolyte levels, fully charge it and check electrolyte levels again.
To be sure it's fully charged, you need to charge it at something like 14.4V for something like 10 hours if you don't have anything more sophisticated. It may lose water during this.
IF you don't start from a baseline of fully charged, any other test is generally a waste of time.

 

[PaulRainbow]

In my view, you may, or may not have killed the battery.

Huh ?

Are there any other choices than may or may not ?

Best thing would be to check electrolyte levels, fully charge it and check electrolyte levels again.

Could you give step by step instructions how to do this with a sealed AGM battery please ?

To be sure it's fully charged, you need to charge it at something like 14.4V for something like 10 hours if you don't have anything more sophisticated. It may lose water during this.

What water ?

IF you don't start from a baseline of fully charged, any other test is generally a waste of time.

If you don't start from a baseline of reading the original post, any other teXt is generally a waste of time

 

[Skylark]

Best thing would be to check electrolyte levels,.....

But OP says it’s an AGM ?

....... Sealed Lead Acid AGM .

oooOOOooo

What is this "equalising charge' spoken of ?

This is a deliberate, but controlled, overcharge to remove sulphate crystals that build up on the plates over time. Generally not required on an AGM battery (one of its advantages)

 

[PaulRainbow]

oooOOOooo

What's that mean ?

 

[Skylark]

What's that mean ?

It’s meant to divide to subjects ?

 

[PaulRainbow]

It’s meant to divide to subjects ?

Well i never........

 

[William_H]

Thanks every one. Yes I think I have damaged it by over discharge. I monitor charge current even at 18volts in the moment current is only around the 5 amp mark. I would imagine it is the current in at high voltage that does the damage. No it has never high a high charge current. Indeed it seems it won't ake a high charge current. Yes intially the buck converter was set to 14v a bit like a car alternator regulator so current did taper off during the day. It seems to have a useful capacity now of about 12 AH way less than the claimed 130AH. The 2 lots of 160w panels are a bit misleading as I said I only seem to get about 70w total into the battery plus now after problems the 80w panel puts in about 3 amps. No regulator.
So I still don't know if I killed the battery or it was just a dud. It cam from too far away to send it back. I will just live and learn. m ol'will

 

[neilf39]

You killed it. You need a solar charge controller. Trying to push amps in by cranking up the voltage despite the charge level will boil the battery. If they are sealed you probably blew out the safety cap and the cells are almost dry. With the solar capacity you had on it the battery was probably back to 90% full charge after a couple of hours, the rest of the time it was being cooked. As a battery gets closer to full charge the less amps it can take so charging slows down. Getting a battery fully charged takes while. Hence put a proper regulator on it.

 

[Refueler]

In my view, you may, or may not have killed the battery.
Best thing would be to check electrolyte levels, fully charge it and check electrolyte levels again.
To be sure it's fully charged, you need to charge it at something like 14.4V for something like 10 hours if you don't have anything more sophisticated. It may lose water during this.
IF you don't start from a baseline of fully charged, any other test is generally a waste of time.

Its an SLA AGM battery ..... not so easy to check electrolyte level !!

 

[PaulRainbow]

Thanks every one. Yes I think I have damaged it by over discharge. I monitor charge current even at 18volts in the moment current is only around the 5 amp mark. I would imagine it is the current in at high voltage that does the damage. No it has never high a high charge current. Indeed it seems it won't ake a high charge current. Yes intially the buck converter was set to 14v a bit like a car alternator regulator so current did taper off during the day. It seems to have a useful capacity now of about 12 AH way less than the claimed 130AH. The 2 lots of 160w panels are a bit misleading as I said I only seem to get about 70w total into the battery plus now after problems the 80w panel puts in about 3 amps. No regulator.
So I still don't know if I killed the battery or it was just a dud. It cam from too far away to send it back. I will just live and learn. m ol'will

The reason for the apparently low solar output is that there is nowhere for the power to go. I have 260w of solar, connected to a Victron controller, i might look at the solar monitor ans see that i'm only getting a few watts from the panels, although the Sun is bright. But if i turn something on, or the fridge cuts in, the output goes up to match the loads, plus a little.

A 110ah leisure or even a decent car battery and a solar controller will sort you out.