[RE-wrenches] 24 volt Battery Bank comparison

Tue May 31 17:21:44 PDT 2011

Just another thought- If redundancy is an issue with string sizing, having a 12v inverter handy is sometimes a viable backup option with a 24v bank with 2 or more parallel strings. 

Jason Szumlanski
Fafco Solar

On May 31, 2011, at 7:55 PM, "Jason Szumlanski" <Jason at fafcosolar.com> wrote:

> If the choice is one or three, I choose one. If the choice is one or two, I choose two for the same redundancy benefit echoed by others. However, it sometimes depends how remote the system is. 
> 
> If you are a few miles down the road from a stocking battery distributor, one string is great. If you are a boat ride or a 10 hour 4x4 crawl at 2 mph away, redundancy may be critical. It all depends on the situation. I would even consider three strings if the location has serious access problems and the customer can only "survive" with 33% capacity loss for a period of time.
> 
> While I have my favorite brands, sometimes you have to go with a brand that fits the right capacity and string arrangement. Fortunately Rolls has lots of options, so you should find a suitable alternative. I start with my desired V, aH, and parallel strings, then let the manufacturer or distributor do the work and recommend options. Not that I don't do my research, but sometimes they come up with a better option than you initially think of.  
> 
> Jason Szumlanski
> Fafco Solar
> 
> On May 31, 2011, at 6:25 PM, "Brian Mehalic" <brian at solarenergy.org> wrote:
> 
>> Hi Wayne-
>> While I think a lot of folks will agree that a single string is better for the long term health of the batteries as it results in more even charging, I still like the idea of at least two strings.  That way if a single battery fails, that string can be removed and the end-user can at least get by on half of the pack until a replacement can be installed.
>> Brian
>> 
>> On Tue, May 31, 2011 at 10:19 PM, James Surrette <james at surrette.com> wrote:
>> Hi Wayne,
>> 
>> I look forward to the input from the wrenches.
>> 
>> My recommendation, regardless of the brand, would be for one string.
>> 
>> Regards,
>> 
>> Jamie
>> 
>> >>> Wayne Irwin <wayne at pureenergysolar.com> 5/31/2011 6:49 PM >>>
>> Hello Esteemed Battery Gurus,
>> 
>> Which of the following do you believe is the better 24 V battery bank?
>> 
>> A) 13 - Rolls 2-YS-31 2430 AH @ 20 HR (one string)
>> 
>> or
>> 
>> B) 9 -  Rolls 8-CS-25P 820 AH @ 20 HR (3 strings of 3)
>> 
>> Thank you in advance for your input!
>> 
>> 
>> Wayne Irwin, EE
>> Director of Engineering
>> Pure Energy Solar International Inc. 
>> State Licensed Solar Contractor
>> License # CVC56695 
>> Wayne at PureEnergySolar.com
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