If I had, say, three fully charged sealed lead acid batteries, connected in parallel, rated at 40 amp hours each, would I have the equivalent of 120 amp hours?
I’m thinking about installing a 100-watt solar panel (along with all of the other required stuff (rectifier, charge controller, etc), and I’m wondering about the storage/usage capacity.
So, what say ye?
cells/batteries in parallel- voltage same as a single cell/battery, capacity (Ah) adds.
cells/batteries in series- voltage adds, capacity (Ah) stays the same.
Thanks. I also found an answer here.
I’ve never even heard of Peukert’s number before.
If all of the batteries are identical and in good condition, then yes, connecting them all in parallel will add the amp-hour ratings together.
It’s generally not a good idea to parallel batteries, though. They won’t necessarily share the load evenly, since even the slightest difference will cause one battery to supply more or less current than the others. If one battery dies (or gets a damaged cell) then the other batteries will constantly try to charge it, so a single failure may take the other two batteries down with it.
eh? what do you think a “battery” is?
I guess I understand the concern, but I could check them with my meter periodically just to make sure. It’s not like they’re going to be moved around a lot or anything. I mean, I have to rely on something, and I have a couple of generators as well.
Maybe I’ll have backups for my backups. 
Most multivolt "battery"s are in SERIES, which is a whole nother kettle of fish compared to cells/batteries in PARALLEL.
This is a standard configuration.
Read up on charge controllers and “equalization” charging.
If you’re going to do this yourself, make sure you read up on how to maximize battery lifespan (don’t deep cycle them unnecessarily, for example).
The DIY environmental wiki Appropedia is a sometimes-great resource for this type of endeavor, though it needs better cleanup and categorization. (Disclaimer: My professor helps administer the site)