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serialk11r · 01-19-2021, 05:46 PM

Alright, it's not budging at 11.3, so these only have 20Ah capacity, unless my current measurement is completely wrong (I doubt it, 54A sounds completely reasonable for ignition + headlights + fans). I'm gonna ask for a partial refund, see if I can swap in some better cells or figure out which ones are bad.

I guess they're technically still more useful than a small lead acid since the internal resistance is lower, but this isn't very encouraging. I did hook it up to a dead Group 24 lead acid battery with jumper cables, and it managed to crank a 3.5L V6 engine without much trouble, so in a way the performance is quite impressive. I recall doing a similar exercise once with a dead 10Ah AGM battery hooked up to my fully charged 30Ah lead acid, and it really struggled to crank a 1.8L 4 cylinder.

EDIT:
Okay I just read this paper and decided I need to reserve judgment until I do another test. Apparently, some cells have a steeper voltage curve, and it's possible that if I run this battery down to 10.0V I can get nearly double the energy out. Still not the advertised 40Ah, but over 30Ah would not be bad for what is effectively a 300 dollar discount.

01-19-2021, 05:46 PM	#6 (permalink)
serialk11r Master EcoModder Join Date: Jan 2012 Location: United States Posts: 1,756 spyder2 - '00 Toyota MR2 Spyder Thanks: 104 Thanked 407 Times in 312 Posts	Alright, it's not budging at 11.3, so these only have 20Ah capacity, unless my current measurement is completely wrong (I doubt it, 54A sounds completely reasonable for ignition + headlights + fans). I'm gonna ask for a partial refund, see if I can swap in some better cells or figure out which ones are bad. I guess they're technically still more useful than a small lead acid since the internal resistance is lower, but this isn't very encouraging. I did hook it up to a dead Group 24 lead acid battery with jumper cables, and it managed to crank a 3.5L V6 engine without much trouble, so in a way the performance is quite impressive. I recall doing a similar exercise once with a dead 10Ah AGM battery hooked up to my fully charged 30Ah lead acid, and it really struggled to crank a 1.8L 4 cylinder. EDIT: Okay I just read this paper and decided I need to reserve judgment until I do another test. Apparently, some cells have a steeper voltage curve, and it's possible that if I run this battery down to 10.0V I can get nearly double the energy out. Still not the advertised 40Ah, but over 30Ah would not be bad for what is effectively a 300 dollar discount. Last edited by serialk11r; 01-19-2021 at 08:59 PM..