Battery Bank Dilemma

sub3marathonman · August 2014

I have been greatly helped by those on this forum, now several years ago, but I'm hoping to hear some ideas about my current situation.

I have four 12V Rolls 357ah (20 hr rate) batteries in series for a 48 volt system, XW6048 inverter, and 4.7kw PV. I've been using them for just over 5 years, with acceptable performance. I've always felt they lacked the stated capacity even from the start, but never was able to determine if that was true. I'll discharge them in the weekday evenings to about 60% DOD to offset peak rates, and recharge them from grid power overnight. At some point I am hoping to take this system off-grid, if I can add another 9 - 10 kw PV array, but at this point that plan is questionable.

The problem now is that apparentlyl at least one cell of one battery has gone bad. Now, I'm not sure what is happening with the warranty, but I'll assume, at least for now, that Rolls will provide warranty support (5 years of a 10 year prorated warranty), which as I understand it would be 50% of the price of any bad cells at this point.

So, if it is one bad cell, and I end up paying a nominal amount for a new cell or two, or even half price for a new 12V 357ah battery, is it worth it? Or is it throwing good money after marginal cells and I'd be better off getting a new battery bank.

Now, assuming I go for a new battery bank, would it be better to just go back with Rolls batteries, although bigger but I'm not sure how big, or should I try to get an industrial battery such as a Crown? What I don't like about the Crown battery is that it seems they must be kept in the original container, which is more of a square instead of a line as I have the current batteries set up in. I don't know if it is possible to make another enclosure for the Crown batteries though. Another possibility is the HUP battery, although I haven't done a lot of research on them. I've even wondered about lithium or possibly NiFe Edison batteries, but those are probably too complicated for me to take care of, since everything is currently set up for PbA.

Thanks for the help.

Cariboocoot · August 2014

Re: Battery Bank Dilemma

My personal opinion is that you would be better off waiting until the batteries are unusable and then buying a brand that does not have such a recent history of defective product and poor customer service. I wouldn't expect anything from Rolls Surrette except a lot of delaying tactics until they are out of warranty. The 'customer service' people have been getting from them has been inference that the customer is always doing something wrong, even for new batteries that show up with an SG of 1.000. Nothing like paying a premium price for a below-par product.

BTW you should have a larger battery bank anyway.
I'm not sure why you're doing what you're doing or exactly what you are doing. You've got grid, so why are you taking power from the batteries? Time-shifting the TOU power probably isn't gaining you anything but will be exercising the batteries unduly. I would think you'd be keeping them up and selling surplus PV power during the day; that's usually when rates are highest. Why would you go off grid? Surely the utility rates aren't near $1 per kW hour? Or are they once you combine low usage with high base rate structure?

Blackcherry04 · August 2014

Re: Battery Bank Dilemma

Is this the battery you have ?? ( Surrette 12-Cs-11Ps ) Doesn't it have individually replaceable 2 v cells ?? It would be a no brainier to change one cell out with a new one.

Vic · August 2014

Re: Battery Bank Dilemma

sub.. ,

Couple of questions;

What is it that causes you to know that cells are bad -- SG readings? Voltage ? ?

How often do you add water?
How often do you EQ?

SSo, you are discharging these batteries to about 60% Depth Of Discharge? This is about 40% State Of Charge. If this what you are saying, then, this is a bit deep for a daily discharge.

What are your Absorb, and EQ voltages? How do you determine that the batteries are fully charged, and charging can be terminated.

Realize that terminology and methods for Grid-connected systems can vary vs purely off-grid systems.

Thanks, Vic

sub3marathonman · August 2014

Re: Battery Bank Dilemma

Vic wrote: »

sub.. ,

Couple of questions;

SSo, you are discharging these batteries to about 60% Depth Of Discharge? This is about 40% State Of Charge. If this what you are saying, then, this is a bit deep for a daily discharge.

Realize that terminology and methods for Grid-connected systems can vary vs purely off-grid systems.

Thanks, Vic

OK, yes you caught a mistake!! During weekdays I discharge them about 40% to 60% remaining state of charge. I can see where that would make a big difference.

Cariboocoot wrote: »

Time-shifting the TOU power probably isn't gaining you anything but will be exercising the batteries unduly. I would think you'd be keeping them up and selling surplus PV power during the day; that's usually when rates are highest.

I had figured that since I already had the batteries as a backup system, I might as well "use it or lose it" with offsetting the peak usage. I know there are inefficiencies there with recharging and using extra electricity, but I'm not sure how long a floating Rolls battery would last vs. how I've used it.

It is a bit upsetting to hear about the terrible customer service from Rolls/Surrette, and even worse to hear about the terrible battery quality. I know that their decline started right around when I bought these batteries, and unfortunately I didn't consult the experts when choosing the batteries, instead relying on a poorly worded Xantrex User Manual. I now know from the experts that I need 100ah / kw PV as an absolute minimum, so that is another reason for possibly replacing the batteries at this time.

And Blackcherry04 is correct, the 12CS11P has replaceable cells, so it may be possible for me to get one or two, but the question is how much would that end up costing, which must be factored into the calculations to see if it is reasonable or not to do. And I'm starting to worry that it won't be the greatest experience dealing with Rolls. When I first got the batteries I was able to contact one person, and he was very helpful in getting things set up, but he has since left the company.

Vic · August 2014

Re: Battery Bank Dilemma

s u b,

OK, thanks for the clarification ...

Hope that you will have a chance to answer about the Absorb and EQ voltages, the EQ frequency, the way you use to end Absorb, water consumption and how often you take the SG of EACH cell of the battery...

AND, how is it that you know that one or more cells of this battery bank is/are bad??? ?

Thanks, Vic

Blackcherry04 · August 2014

Re: Battery Bank Dilemma

Here is who you should contact, Steve Higgins, he is well versed in Solar. They will ship you the cells, unless your just want to buy some new batteries. You could always sell those batteries. The shipping could be more than the cells, they will ship them to a dealer and you can pick them up. That battery has 1/4 plates I doubt they are all done yet. If it's not shorted, whats the SG level ?

steve@surrette.com

zoneblue · August 2014

Re: Battery Bank Dilemma

The other ratio you ought to be converned with is 100Ah per kW of inverter. Pulling 6kW (12kW peak) out of 390Ah bank is gona hurt a bit.

Your logic on use or lose it has some merit, as you say, calendar life is finite. But the real question is how much do you want to pay for this grid backup? Getting the FLA bank up to 600Ah, will cost you some. AGM is one solution for those that want/need a small bank for hybrid setups. AGMs will take and give a higher current. Youd only need 200Ah.

See http://forum.solar-electric.com/showthread.php?16082-Maximum-Battery-Load-Current

sub3marathonman · August 2014

Re: Battery Bank Dilemma

OK, I'm resending things to Steve there, but I'll try to condense things here.

Battery #1 is a problem. Voltage reads 9.26, there is a spot where the plastic top has apparently slightly melted opposite of the battery posts, but the SG of the cells reads 1.220, 3 @ 1.210, 1.195 and 1.185.

Battery #2 seems to be OK. Voltage reads 12.34, SG is 3@1.225, 2@1.220, and 1.215.

Battery #3 is a problem. Voltage reads 12.06, SG is 3@1.210, 2@1.205, and one cell at 1.000 (wouldn't register on the hydrometer).

Battery #4 seems to be OK. Voltage reads 12.21, SG is 2@1.205, 1.200, 1.195, 2@1.190.

At this point I'm not sure what Surrette will decide to do, but by now after 5 1/2 years it is a prorated warranty situation. And even several cells or even an entire battery at half-price seems to be a real question. How much longer would things last with such a fix? Is another cell ready to go bad in a month or two? Nobody can know.

I've started researching replacing the batteries, but that is probably another topic for another day. But obviously the price will be much, much higher than even just replacing an entire battery for this setup.

Give up and abandon ship now, or try to stay longer attempting to patch a fix for these (marginal/less than optimum at best) batteries? Try to put together three batteries with some life left in them and sell them?

So any help/advice will be greatly appreciated.

vtmaps · August 2014

Re: Battery Bank Dilemma

Your SG are all over the place, and none are fully charged. It makes me wonder if you've been deficit charging for a few years. How long has it been since you've checked, and found the SG of all cells to be fully charged?

--vtMaps

Blackcherry04 · August 2014

Re: Battery Bank Dilemma

There is a whole lot more going on here than one bad cell. When is the last time you checked the SG level ?? When is the last time you did a EQ on them ?? You might be able to recondition them to some acceptable level, they would be a challenge.

Are they at what you think is a Full charge now ??
.

waynefromnscanada · August 2014

Re: Battery Bank Dilemma

vtmaps wrote: »

Your SG are all over the place, and none are fully charged. It makes me wonder if you've been deficit charging for a few years. How long has it been since you've checked, and found the SG of all cells to be fully charged?

--vtMaps

These are also my thoughts. Brings to mind that old saying: "Most batteries don't die, they're murdered". One or even two "bad" cells would be one thing, but the whole battery bank in such a mess? Indeed a very sad state of affairs.

I have a cousin with a solar powered cottage and to prevent disaster, I've had to take over monitoring and maintenance from day one.

Battery Bank Dilemma

Comments

Categories