My aging Northstar group 27

[Sternwake]

Originally Posted by smac999

Why are you draining a single group 27 to 50% and under. Just think if you had boughten 2 of them, kept them at 75% (same daily usage). They'd probably last 3 times longer....

I bought 1 flooded group 31USbattery (130Ah) for house loads and the Northstar 27 for engine starting/emergency capacity at the same time.

The flooded battery also went ~ 450 cycles before one cell's SG could not be brought above 1.255, and the bottom of that cell was heating up, and I removed it from service.

At that point I transferred all loads to the NS AGM-27 while I began modifications for accommodating single t-1275 where the 31 once resided.

The Northstar's voltage in the same usage stayed so much higher than the flooded 31 ever did, upto about 65AH from full, and could still start my engine easily when that depleted, I simply quit modifiying things for a T-1275. Instead I decided to just beat the Snot out of the NS-27, but at least recharge it as best as I could. It probably had about 35 deep cycles on it in 18 months, when full time deep cycling/engine starting duty began.

When the NS can no longer do its job, I will increase capacity, but not by any significant amount, perhaps a group 31, or perhaps I will finish modifications for a taller scrubber battery like the t-1275, or Lifeline gpl-30ht if I'm feeling rich.


I feel the ability to achieve a higher charge rate is important, and I want my 200 watts solar to at least be able to approach and hopefully exceed 10% on June21 at noon. I also want a battery that has no issues regularly handling 40 or 65 amps from my plug in charging sources, or 106 amps from my alternator, which could take the t-1275 out of contention, although my flooded 31 handled these high charge currents and achieved 450 deep cycles.

I am not in the trickle charge low and slow always is best camp. I am in the achieve Vabs ASAP, and hold it as long as is required camp.

It really comes down to cycles per dollar, and While my ability to recharge properly has increased, so has my cycles per dollar ratio, along with my decreasing battery capacity.

I am just not seeing the need for much more capacity than I currently have. I once caried 345AH ( claimed) 3 flooded marine 27's, and cycled those lightly and their performance was dismal, but I was not holding absorption for long enough either.

Lots of capacity definitely falls into the warm and fuzzy category, but warm and fuzzies often are bragging rights and nothing more, in my opinion.

Either way I will be working this battery hard until it becomes problematic, and at that point, whenever it may be, I will decide how much capacity, and what battery to go with.

I figure I will have a small jumper AGM battery well before true failure for emergency jump starting.

[Sternwake]

Did a test on it tonight. I drained it to 57Ah from full, in about 6 hours with loads as high as 11 amps.

At that ~6 hour mark I applied a 200 Watt electric heater to reach 22.4 amp load, voltage fell to 11.5v.
~2 minutes later under a 5.6 amp load had voltage rebounded to 11.7
~2 minutes later under a 1.7amp load had voltage rebounded to 11.92v
~2 minutes later under a 0.3 amp load had voltage rebounded to 12.02v

Battery temperature was 63F.

Apply 25 amp Schumacher 'smart' charger on 25 amp setting
Apply Meanwell powersupply for 40 amps, voltage cranked to 15+ for a total of 65 amps charge current into this 90Ah rated TPPL AGM.

Voltage rose to 14.4v within 30 seconds.
Over the next 5 minutes voltage dropped to as low as 13.9v at this 65 amp charge rate.

At the 24 minute mark at 65 amps, voltage had risen to 14.7v, battery temperature had risen to 70F, and the Schumacher 'smart' charger was backing off the amperage, and voltage then fell back to 14.5v

6 minutes later at 32 minute mark, voltage just touched 14.8v at 52.4 amps and battery had risen to 73.4f

At 40 minutes I UNplugged the Schumacher, and it was at 14.7v and accepting 35.5 amps from Meanwell power supply.

Battery temperature had risen from 63F to 77.2F in 40 minutes In ~58F ambient temperatures.

At 47 minutes, 14.6v accepting 27.6 amps @ 79F( I Am lowering Absorption voltage manually every few minutes to keep it from exceeding 14.6 ish as amps and voltage drop on my wiring lessen)

At 53 minutes 14.6, 22.2 amps and 80.8F

at 63 minutes 14.6 16.2 amps and 82.2f, IPNPR claiming 12Ah from full

At 71 minutes 14.6c 12.2 amps and 83.6f 10Ah from full.

At 77 minutes 14.6v, 10.6 amps and 84F 9Ah from full

At 90 minutes 14.6v, 8.0 amps and 85.3F and 8Ah from full

at 120 Minutes 14.6v, 4.6 amps andn 87.1F and 5Ah from full

Kind of late now, so I will not be Awake to monitor when amps taper to 0.45 or less, so will lower voltage to ~13.8v and goto bed.

I am pleased it accepted 65 amps for 24 minutes.

I am annoyed Schumacher started backing off from its 25 amp output at that point, but at 32 minutes battery touched 14.8v and was still accepting 52.4 amps, So at a constant 65 amps 14.8 would have happened around 27/28 minutes, is my guess.

I'm not really believing the battery monitor's AH from full screen, but will not be awake to read what it says when amps do taper ot 0.45 or less and will not hold Absorption voltage any longer anyway, But will goose it upto 14.X when I am awake and see how many amps it accepts then and report back.

[Sternwake]

Woke up early briefly, saw it was taking 0.1amps at 13.8.

Goosed voltage to 14.7v, and it went upto 0.7a.

After urinating saw it had dropped to 0.1amp@14.7
Battery temp dropped to 68f in that time, about 3.5 hours.

Reduced voltage to 13.6v and went back to bed.

3.5 hours later, same results with voltage goosing to 14.7v.