Absorb Time?

[Arctic Donkey]

Are there some general rules about how long it should take to charge a battery bank? My bank was down to 50% (based on a SG reading of 1200) and after 10 hours of generator run time was only up to 1255. My inverter/charger switched from bulk to absorb after ~2 hours but 8 hours in absorb didn't seem to do the job of getting the cells up to 1265. I have checked my hydrometer with some new electrolyte and it appears to be
reading correctly.

Our system currently has no solar or wind, just a diesel generator, batteries and inverter/charger. I set the charger timer at the max setting of 480 minutes and both my bulk and absorb are at 30.0V. Bulk current starts at 145A and after the 10 hour of charging was down to 17A.

10Kw diesel generator
6 x Rolls series 5000 4KS25P batteries (1350Ah @20 hrs)
Xantrex XW4024 inverter/charger

Steve

[Mike90250]

Have you tried the battery mfg for suggested times? I'd be guessing, but you can always measure SG (specific gravity) and when it stops rising, they are charged.

It also depends on how low the batteries started off at too. I've also heard bulk time = absorb time, or run absorb till amps into batteries is <5% of capacity (or was it 10%?) So I'm guessing now. Check with Mfg.

[Arctic Donkey]

I did try emailing Surrette but that went no where so I will try calling them. I finally got my pilot cell up to 1265 but my total charge time today was 12 hours. Perhaps that is what it should be but I had expected less. Here are the numbers from today:

start 10am 1200 24.2V (300 watt load when measured)

1pm 1210 80A 29.6V
2pm 1215 48A 29.9V
3pm 1225 33A 30.0V
4pm 1230 25A 30.0V
5pm 1240 21A 30.1V
6pm 1250 19A 30.1V
7pm 1255 18A 30.1V
8pm 1255 17A 30.1V
9pm 1255 17A 30.1V
10pm 1265 17A 30.1V

[Sunking]

So Steve what is the pilot cell temperature, and did you adjust SPG accordingly?

To speed things up set the voltage up so Bulk = Absorb.

[Arctic Donkey]

All my SG readings were adjusted for temperature, 0003 points for every 10F outside of 80F. The highest temperature I saw was 105F but once the current dropped it was very near to 80 + or - 5 deg.

Bulk and absorb are already both at 30.0V.

Dereck, after the bulk phase was completed I expected my absorb to take an additional ~4 hours. How long would you expect it to take?

[Sunking]

Dereck, after the bulk phase was completed I expected my absorb to take an additional ~4 hours. How long would you expect it to take?

Well if Bulk = Absorb then ZERO time. Once you hit 30 volts it should switch to FLOAT of 27.1 volts

[Arctic Donkey]

But if it goes to float once 30.0V are reached, then it would have done so while my batteries only had a SG of 1225 (3pm in my numbers above). I thought the bank was suppose to have reached 1265 at the end of the absorb cycle?