Performing test now. Started when Northstar AGM-27M was 43 A/H from full according to my battery monitor.
NS proclaims 50% is a rested 12.1v. I was reading 12.12v under a 6.2 amp load when I began test. This is as much a test of the NS AGM battery as much as the cheapowatt, i want to see how fast the amps taper.
I did not remove the lid before test so no internal temp readings except through fan hole and was able to find 133f. My easy to move fan is needed for the human in the vehicle.
Am taking voltage readings every 10 minutes or so, at the terminals, GTpower and IPN pro remote battery monitor. recording amps, amp hours returned on gtpower and amp/hrs into battery as there is a 3 to 6 amps load running.
Once again anything over 36.2 amps caused the buzzing crackling.
It is not the fan. Stethoscope made is sound loudest closest to AC input a few inches deep but this is no certainty.
When searching for source, amps went up to 39.44 at one point as measured by gt power and 0.74 less on GTpower
Max temp on the side of the case right over the mosfet closest to voltage pot was 124f. The mosfet location next to that was always at least .5F less. The rear mosfet case locations were 14 to 16F less and also 1 degree difference each and every time.
Every time I checked, for the first hour, I turned the voltage pot higher and pushed the amps back upto 36.2, the buzzing limit, as it had tapered down an amp or two every 5 minutes.
At 51 minutes the voltage pot was maxed out and remained there until the 61 minute mark when battery voltage exceeded 14.7. gtpower was reading 25 amps at this point with 3 to 6 of those powering loads.
I really should have recorded amps into battery by battery monitor. dang.
From here on out I lowered the trim pot every few minutes to keep battery voltage from exceeding 14.7v
At the 61 minute mark it was reading 16 A/h from full when battery voltage had reached 14.8v. Terminal voltage was 15.27, gtpower voltage was 15.07
Right now, 1 hours and 35 minutes in:
14.7v at battery, 14.89v gtpower, 14.98v at cheapowatt terminals
Gt power reads 13.83 amps, battery monitor reads +10 amps(into battery) and 7 AH from full. Hottest case temp is 87F.
Gt power saying 53.22 amp hours total
Kinda should have removed all loads from cheapowatt but then I cannot easily read battery voltage or AH from full, and danged if i am turning everything else off.
Obviously fatter cable would reduce the rubber band factor, the difference between cheapowatt terminal voltage and battery voltage. My desire to keep it from buzzing and as close to the 36.2 amps buzzing threshold makes this a very manual charger.
I'm not afraid to feed this NorthStar AGM a 33%+ charge rate. Me thinks this battery is under rated capacity wise. They claim 90 A/h.
I wonder how much longer it would take if i just set it to 14.7v initially at the terminals, unloaded, pretended I did not hear the buzzing when I plugged in the powerpole to the battery, and just let it go without any further trim pot tweaking.
But I wanted to feed this battery 36.2 amps as long as I could until 14.7 was reached at the battery.
The trim pot is still pretty tight considering how much I have moved it since Tuesday.
Now, 2 hours and 5 minutes after test began, battery taking 4.1 amps at 14.7V and battery monitor claims 4 A/H from full. Amps into battery tapering fast now.
Cheapowatt case hottest part is 80f making 7.29 amps. Ambient 73.5f
AC voltage was reading 115.2 when CW was making 36 amps
AC voltage now 118.2 now making 9 amps( fridge kicked on.
Okay 2 hours 14 minutes after test began:
Battery accepting 3.1 amps at 14.7v. Claiming 4 A/H from full.
gt power reading 14.78v, 6.22 amps, 60.734Ah Amp Peak 39.78 amps, 873.23Wh, CW terminals 14.84v,
Tired. Gonna back it off to 13.6v and just let it go.
Maybee make a graph in future, but wish i measured amps into battery, not total amps made by cheapowatt.
tell you what, I am a tired 'automatic' charger. not easy to keep those amps maxed out, or then the voltage from rising over 14.7 after that point. actually it is not that much work. Taking reading and writing them down is.
The guy who makes a charger that can do true selectable CC then CV at battery terminals, should be a rich man, but who would pay that much for his charger?
