Money and No Brains

Re: Money and No Brains

stephendv and I are on similar pages, altho on some of the fine details, I do wax and wane.

Some do note that FLA batts should be cycled to 90% SOC as a minimum per charge cycle (ie, cycling to 80% would be better). The way I read Surrette's info (and from some conversations with Surrette tech), believe that they are saying that their Solar batts should really by cycled to abut 50% SOC per cycle, "Surrete batteries are meant to be worked" or similar.

The PV array on the oldest system here represents about 4% of 20 Hr capacity. Agree that on larger batt banks, really, 100 hr capacity is probably more meaningful, as the 100 hr rate on this bank is 19 amps, which represents a fairly large load over 100 hrs. Although, this might make some feel that at 10% minimum recharge capability, one would need 190 amp charger.

This bank with this anemic PV array seems to be doing fine after 7 years in service ... knock, knock. One must be careful to not discharge the bank too deeply, or at least monitor the bank carefully, and be ready to use generator power to recharge when needed.

It might be difficult for the OP's 3Kw genset to get to EQ in a mature Forklift bank of the size noted, or at least it might be a slow grind. Doing an an EQ at the end of Absorb is easier, as one does not need to recharge back to the Absorbtion setpoint.

Personally, believe that the OP's large bank should do fine if attention is paid to monitoring SGs regularly, EQing when needed, and monitoring water levels.

Even Hup has moderated its previous dictum of mandatory 10% of capacity from PV input. In the past year, they have begun stating that a minimum of 10% recharge capability form the sum of all charge sources (or similar).

Busy households with teens, and the person responsibility for managing the Power System absent, DO need much more PV recharge capability, and perhaps AGS on a capable genset. Things can get out of hand when that person is not always present to monitor and correct undercharging etc. OH and stephendv, there may be a typo in your calcs of power needed to recharge from 50% DOD, or mabe it is just my tired eyes/brain. Just opinions, Good Luck, Vic

Re: Money and No Brains

I believe that straitification is a non-issue, at least in some tall Surrettes here. An Absorption charge at any reasonable voltage seems to do the trick in a few minutes. It is difficult to actually measure. Added some water the main bank here the other day. Was only about 10 Fl oz per cell. The batteries were in Float. Did a 20 minute Absorb at 59 volts, and seemed that all of the added water was mixed, and SGs were normal.

This is not an exhaustive test. Each cell is about 22.5"H X 7" X 10". So a tall cell. I could unserstand some stratification is the battery only was recharged once per week of so.

Thanks Wayne for posting Surrette Bulletin 614. This Bulletin changed three times IIRC. The first rendition that I saw recommended not recharging the battery bank until it reached 50% SOC (or every 30 days at a minimum), and then charging at 10% of 20 hour capacity, IIRC. Was told that this was a contraversial document within Surrette Engineeding. Some of the context was that batteries that were habitually lightly cycled and charged at low rates, would have charge acceptance issues after some time. This regime would save fuel, improve capacity over time, and increase charge acceptance, especially on systems with anemic PV input (which was the norm in years past).

Believe that the reconstructed Surrette site is a bit more useful than it had been, although, some of these bulletins were useful, if one could find the correct one.

FWIW, the batteries in use here have more than 40% difference in rated capacity between 100hr and 20 hr rates ... And so on, Vic

Re: Money and No Brains

Agree with BB Bill about raising the Absorption V setting for Winter season -- this will allow more chaging to occur in the short Solar days.

You have NOTHING to loose by EQing the snot out of the batteries. With the huge variations in SG, you need to get the average SOC of the bank UP. Just monitor the electrolyte temps. With such a wide variation in SGs, the temperature differential twix individual cells may well be greater than for a bank with a tighter SG range. If you have a glass thermometer that can be be immersed into each cell to monitor temps, this chould help.

Forklift batteries are very tough. And, you might want to review charging/EQing strategies with the folks that sold this bank to you. But, time is wasting, allowing low SG cells to remain low for an extended time is not good, IMHO. Good Luck, Vic