Backup standby SLA batteries

G’day guys,
I have 12 x Enersys Supersafe 12V 170ah batteries 12T170FS manufactured in 2018. They are a standby/backup battery. How do these fair in a battery bank for solar? My intention is to double up on these to reduce the DOD. Have these batteries been successful in an off grid system?

Thanks guys.

Al.

Not how none of that performance data or the model data sheet say nothing of cycle life.

Emphasis is high charge and discharge rates and "thin plate" manufacturing process.

Deep cycle batteries with good cycle lives tend to have thicker plates and NOT handle high charge/discharge rates.

Auto batteries have thin plates for high current discharges and rapid recharge after starting.

Deep cycle batteries have thick plates for longer life.

I place UPS (standby/back) batteries somewhere in between but closer to auto.

At 4 years old, they're already potentially compromised. If you already have them, and they are "free," there's no harm in trying them, but you should limit discharge depth as you plan. Discharging no lower than 70-80% might get some decent life out of them. If you're considering buying more, I wouldn't unless they're crazy cheap.

AlanH said:

I have 12 x Enersys Supersafe 12V 170ah batteries 12T170FS manufactured in 2018. They are a standby/backup battery. How do these fair in a battery bank for solar? My intention is to double up on these to reduce the DOD. Have these batteries been successful in an off grid system?

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I found one quick reference for these:

Enersys will also have other more detailed documentation on them if you dig a bit more.

They are high quality batteries but as with any battery it comes down to what state it is in when you get it and what you hope to do with it.

My home backup system uses very similar batteries. Mine are the Enersys Supersafe SBS 190F. You can read about my system here:

The have units actually useable for hybrid battery applications:

Have a ferret around the Enersys site to see what data you can find on your model.

I load tested mine and they were good, and I'd say the data centre which sold them barely used them and just had a policy of changing them out after a certain amount of time. But without any data on how they have been used and treated it's always a bit of a lottery. Hence why they can be pretty cheap to pick up.

I have eight batteries in two banks of four for a 48 V system. While they are 190 Ah units, that's their nominal 10 hour rating. The 20 hour rating for mine are 212 Ah, so a nominally 20 kWh bank.

Now I don't cycle mine much, regular cycling is using less than 5% of capacity a day and they are charged every day with solar PV. Their primary task is for home backup when the grid supply goes down. But they also act as ballast for the loads I do have running from the off-grid PV system (pool pump and office peripherals). IOW mine are pretty much kept in that 95-100% state of charge range, with occasional dips down to ~80% for a typical grid outage backup scenario.

I work on the basis that I can comfortably draw 8-10 kWh out of the bank if needed, which provides us with 16+ hours of outage coverage. In general by then solar PV would be able to start recharging the batteries, or if PV output was not sufficient then I can just fire up the generator.

I will be expanding the functionality of my system to handle household loads on a more regular basis however the storage capacity for that job will be LiFePO4 batteries - they are far more suited to regular deep cycling. I'm hoping to cover about 5-7 kWh/day with those.

This doc has more info on expected cycle life:



Problem is not knowing conditions of use when you get them second hand.

Typical AGM deep cycle life is about 1200 @ 50% DoD. Those are about 800... when new.

If cycled daily, that's a little over two years... on new batteries.

sunshine_eggo said:

Typical AGM deep cycle life is about 1200 @ 50% DoD. Those are about 800... when new.

If cycled daily, that's a little over two years... on new batteries.

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Yeah, it depends on the model.

There are others such as the SBS Eon models which are designed for combination of standby and cyclic application. They have this cycle life specification:

Since I'm pretty much operating mine well inside the 10% DOD range, I've little concern about cycle life.

wattmatters said:

Since I'm pretty much operating mine well inside the 10% DOD range, I've little concern about cycle life.

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I will be buying another 12. Typically the intention is to reduce the DOD. At $120 each, i think this is a pretty decent deal for a battery that has probably had little cycle life.

I have the 190 orange/red battery in my camper. Two years since I bought it second hand. No issues so far.

AlanH said:

I will be buying another 12.

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If nothing else it'll be a good workout. You'll have over a tonne of battery.

wattmatters said:

If nothing else it'll be a good workout. You'll have over a tonne of battery.

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If nothing else? It will be fine.

AlanH said:

If nothing else? It will be fine.

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If it wasn't obvious, it was a joke.

wattmatters said:

If it wasn't obvious, it was a joke.

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All good mate. Ill be going down to Melbourne to buy another 12 in the next couple of days. Keeping the DOD as low as possible should get me my moneys worth. I have 18 x 250w solar panels to pick up as well.

Cheers.