On: Is it okay to daisy chain a UPS?

[lmpdev]

What I find insane is the peak current discharge those little 12V 7-9ah backup batteries can push out

Well over 100A for a few seconds

Lithium can’t even do that in a single cell (but in turn is infinitely better for continuous current)

It sort of baffles me intuitively that an extremely simple lead battery can for a short while compete with the grid

[somehnguy → lmpdev]

Lithium polymer pouch cells can easily push out well over 100A, even relatively small cells hit this mark no problem.

[p1mrx → lmpdev]

12V x 100A = 1.2 kW. A typical grid connection for a house is 240V x 200A = 48 kW.

[jpgvm → lmpdev]

Yeah this is why lead acid was hard to replace in cars with lithium chemistries.

The Cold Cranking Amps (pretty much the peak startup current) that they can provide is rather insane. Even my small motorcycle battery provides over 250 CCA.

[elintknower → jpgvm]

Super capacitors / just large capacitors in general might eventually save the day here. The only issue is super capacitors can't generally bake in the heat all day and still work for 3-5 years like lead acid batteries can.

Supercaps is how "fast" charging in most smartphones works as well since they can soak current faster than the battery itself and also mitigate cycling batteries too hard.

[jnsaff2 → lmpdev]

It won't be anywhere near 12V while supplying those 100A.