nlspace wrote: ↑
Mon Jan 04, 2021 10:39 am
SageBrush wrote: ↑
Sun Jan 03, 2021 3:10 pm
For anyone interested in my battery evaluation games:
All battery readings are from a battery tester doodad I have connected to the battery all the time. I read the voltage and "SoC" from a bluetooth connected app that also logs voltage readings every couple of minutes.
I charged the battery to 'full' on 12/30 -- 12.6 volts
The next day the car was driven ~ 45 minutes
Two days later the battery is at 12.2 volts
-- a 90 watt load (~ 8 A)(low beams) dropped the battery to 11.7 volts
-- fiddling with the headlights for under 5 minutes dropped the estimated SoC by 10%
--- So from a short test the battery capacity is ~ 8*5/6 = 7 Ah. Out of perhaps 35 - 40 Ah when new
Looks like you have an old, weak and worn out aux battery and probably time to be looking for a replacement soon.
My conclusion as well.
I charged the battery to 'full' -- 12.7v and headed to Autozone. Their device reported a drop in voltage to 12.6v with a 250 A load. I asked the woman to test again and the same result came back. So now I am unsure, and decided to buy the bits I needed for a load test. I took Jerry's excellent advice and bought a 12v lightbulb at Walmart (55 watt, H7) for $10 and a $5 H7 connector at Autozone. Flush with anticipated adventure I splurged $4 on a pair of alligator clip wires.
To my pleasant surprise the rig lighted up and I was ready to declare success when smoke started to come out of a wire. I think the wires touched each other and shorted so now I have to buy a new set of alligator wires and try again.
Question though: I attached one wire to the negative terminal of the 12v battery. Should I have connected it to the car as ground instead ?