L16's or GC2'S?

Saggys · June 2015

I have 900 watts of PV and a PWM charge controller. This would be for a 12 volt battery bank. The panels are Siemens SP75's with a Imp of 4.4A which under ideal conditions should be able to provide 52.8 amps of charge current. This would be my first New battery bank as I have been running only half of the array into some used scab batteries. I have a hydrometer and perform battery maintenance at work so not a total newb. So 2 L16's in series or 4 GC2's in series parallel? My insulated battery box will support either. I am leaning towards the L16's but GC2's are easier to find.

mike95490 · June 2015

Start with with the GC2. Read up on connecting them on the diagonal here http://www.smartgauge.co.uk/batt_con.html
You are a little bit overpaneled, but better to be over than under in my book.

Photowhit · June 2015

I'd suggest GC2's as well, I had a similar dang near exact system! 8 - 115 watt panels and a Pulse energy (later Trace) PC250. If you did get the panel rated 52.8 amps coming in you would be at 12.5% of a 420 amp hour battery bank, with in the margins of pretty much all flooded lead acid batteries. I ended up expanding to about 1600 watts on 4 GC2 (abit in a 24 volt configuration, you will be maxed out with the 60 amp charge controller in the PC250) and rarely exceeded 15% charge rate.

I've been saving the PC250 digital manual if you need a copy?

softdown · June 2015

GC2s are my vote. Costco and Sams club carry them. Other stores may price match if asked.

Johann · June 2015

Why would you folks recommend the GC2's?
Is it the price or longevity?
How long would they last anyhow?

mike95490 · June 2015

Johann wrote: »

Why would you folks recommend the GC2's?
Is it the price or longevity?
How long would they last anyhow?

Easy to find, price and I guess they should last at least 2 years. In those 2 years, you get a chance to fine tune things, and then you can buy the pricy L16's when the GC2 wear out

vtmaps · June 2015

Johann wrote: »

Why would you folks recommend the GC2's?
Is it the price or longevity?
How long would they last anyhow?

It's the price... more amphours per dollar. They do not last as long as L-16s (assuming proper care of either type).

On the subject of proper care: GC2s are easier to care for because they are less subject to stratification issues.

The BIG downside of GC2s is their lower capacity which means that a GC2 design is more likely to have parallel strings of batteries (which is not an optimum design).

When I designed my system I was torn between 8 GC2 in series (48 volts) and 4 L-16 in series (24 volts). I would not put 8 GC2 (series/parallel) in a 24 volt system.

--vtMaps

706jim · June 2015

I ran 12 GC's in a 24 volt series parallel system since 1996. They pretty much failed last year, but with equalizing them every couple of months and keeping track of acid levels, they worked very well. I only have about 430 watts of panels.
I opted to replace the GC's with 8 L16's. Time will tell how this bank will perform. More panels will be forthcoming but not for another year or so, hence my earlier post regarding required equalization current for this model of battery.

Photowhit · June 2015

One of the reason's I suggested GC2s is that you are at the max of what I would consider 12 volt system range. You are also maxing out the charge controller. The next step, if you decide to expanding your system capabilities, would be to move to a 24 volt system. I actually did this planning on moving to a 24 volt system, but 4 GC2s will allow you to do that without having all the expense at once.

kaipo_boy · June 2015

706jim wrote: »

I ran 12 GC's in a 24 volt series parallel system since 1996. They pretty much failed last year, but with equalizing them every couple of months and keeping track of acid levels, they worked very well. I only have about 430 watts of panels.
I opted to replace the GC's with 8 L16's. Time will tell how this bank will perform. More panels will be forthcoming but not for another year or so, hence my earlier post regarding required equalization current for this model of battery.

That would be 18 years? Impressive run. May I ask what the average DOD was on this bank? I have GC2 (4 of them in series) and am learning how to run them, but a long spate of cloudy weather has me scratching my head. I've increased the absorb time to 6 hours, basically the entire day, but the cloud cover doesn't allow me to hit float by the end of the day. What is the maximum voltage you would put into the GC2 (24v bank) as your absorb voltage? I was running 29.5v, with no temp rise in the battery bank (rock steady at 79F), so today I moved it to 30.0v (small steps tend to get me into less trouble) and am standing by with thermometer sampling the battery bank every 30 minutes to see how they react. Its finally a sunny day, so I am staying near and watching them so if the temp starts rising or if I see a lot of gassing I will be able to terminate early or turn down the absorb voltage. Being only allowed changes to absorb time and absorb voltage, but having the CC in charge of the current and not being able to manipulate that is a little frustrating. Not to mention having to keep an eye on the sky all the time. The bank is 2 weeks old and I have only done 1 EQ (at 31.2v, the SG at the beginning was 1.240 and at the end was 1.285, took about 3 hours).

BB. · June 2015

Our friends in Canada tend to have batteries that are very cold in winter, or reasonably cold average bank temperatures. In general, for every 10C under ~25C, batteries will last 2x longer...

18 years--That is still very remarkable anywhere.

-Bill

706jim · June 2015

I did my best to take good care of those batteries. It might make a difference to other users that the 19 year run includes 19 winters where the bank was not used from November until April. Solar charging would be occurring about 3 of those six months when the panels were not snow covered. Up here in Canada, those (charged) batteries would be subjected to temperatures of -20F to +20F for three or four months. As for DOD, I would typically need from 40 to as much as 80 Ah going into my 24 volt system to bring the batteries to float. Therefore, DOD would range from perhaps 5% to 15% or so, based on a rated 660Ah.bank. I use a Trace C40 pwm controller and the voltage settings were default; 28.0 volts bulk, 27.0 volts float and 30.0 volts equalize. I would run the equalize regime probably 3 times in the six month season. On Trojan's recommendation, I'm setting bulk voltage a little higher at 28.6 and float at 26.4 for my replacement L16's. FWIW, the GC battery brand was Dunlop, purchased at a Sam's club in July 1996 for $44 apiece. The price has since increased, plus there are different levels of quality to choose from now. The best value for your dollar has always been Sam's, although a dozen GC's have a lot of connections to maintain.
When one considers the size, the low cost and the manageable weight of GC batteries, they are hard to beat.

Saggys · June 2015

Thanks guys, GC2's it is. Thanks for the manual offer but I have one.

softdown · June 2015

I think 5 years ia a more average life expectancy.

Brlux · June 2015

I recently went through your same dilemma on a fairly similar sized system. I could get a lot more capacity for my money withe Trojan T105s as apposed to L16. I know people claim L16 will last longer but form the speck sheets they both claimed the same number of cycles for the same depth of discharge. With 2 strings of T105s I had a higher capacity so a lower depth of discharge for the same usage. The 4 T105s were substantially cheaper than the 2 L16s for what i could find locally.

westyd1982 · June 2015

softdown wrote: »

I think 5 years ia a more average life expectancy.

I have a set of GC2's. They are 6 years old and are at the end of their life. I have been very happy with them and will be replacing them this summer with another set of GC2's from Costco. The question I'm debating is do I go with six again or just four? I had one battery go bad two years ago, so I disconnected that one string and have been running on four batteries. It has worked fine until a few week ago. Now the batteries seems to have a lot less capacity and discharge quickly. Time for a new set.

BB. · June 2015

If four batteries lasted 4-5 years, would you still be happy?

Fewer batteries, deeper cycling in the first few years could have helped the rest last longer. But--If you never deeply cycled them, or only used them weekend/seasonally, then you might not have cycled "to death" but simply they aged out instead.

Sort of difficult to tell... How much/how deeply did you cycle them?

-Bill

Mountain Don · June 2015

Johann wrote: »

How long would they last anyhow?

Depends. Ours are beginning their 7th year of service. Series parallel 24 volt system. Not optimal in theory but I can't argue with the service we have had. Mind you the location is cold to cool most of the year... more cool than hot on average.

L16's or GC2'S?

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