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So I have bagged a hybrid inverter from ebay, looking for battery now to add to my DIY solar system(s). Now it's a growatt sph3600 which may be picky with non growatt lithium, but will work fine with lead acid.

But I can't quite get the aH kWh and battery size thing straight in my head!

So I can see 120aH leisure batteries for £60 or best offer on ebay, local to work easy to get.

I was thinking 4 of these = 480aH @12v and works out to about 5kWh, so far as my online calculator theory lasts.

That's well cheap compared to lithium.

Or am I completely wrong??

drjim wrote: ↑Wed Jan 29, 2025 8:27 pm So I have bagged a hybrid inverter from ebay, looking for battery now to add to my DIY solar system(s). Now it's a growatt sph3600 which may be picky with non growatt lithium, but will work fine with lead acid.

But I can't quite get the aH kWh and battery size thing straight in my head!

So I can see 120aH leisure batteries for £60 or best offer on ebay, local to work easy to get.

I was thinking 4 of these = 480aH @12v and works out to about 5kWh, so far as my online calculator theory lasts.

That's well cheap compared to lithium.

Or am I completely wrong??

I wouldn’t bother with Lead. Too short lived and inefficient. There is also no official definition of “starter”, “leisure”, “marine”, etc. those so-called “leisure” batteries are very likely to be “starter” batteries that are designed to be kept above 80% at all times. Therefore you only get to use 20% of the nameplate capacity if you want them to last more than a week. Even if they are genuine “leisure” batteries you only get to use 40% of the capacity if you want them to last.

Buy some LF280k cells from Colin, tell the inverter they’re Lead, set a sensible max charging voltage and min cutoff voltage, and you’re good to go.

If you're familiar with lead acid limitations and you really want to go lead acid, go for a forklift battery. Like stinsy I don't rate 'leisure' batteries at all: you probably get as good or better cycle life out of a good quality starter battery as you would from a no name leisure battery.

The performance of those batteries at 3.6kw would be poor compared with Lithium, and if you're planning on cycling daily you will waste a lot of potential charging time slowly filling them to 100% and equalising.

Even with forklift cells, unless you have a lot of spare free charging energy to offset round trip losses, (or you get them very cheap) it would be hard to make a case for going lead acid over Lithium at today's lithium prices.