[RE-wrenches] battery cycle life, US Battery

[Ron Young]

Hi All,
Not sure where the 4 - 5 strings or more drifted into this conversation but the setup is basically in two strings of 16 GC batteries (48v) vs. 8 L-16 batteries in one string that I am recommending. With 7 year warranty for the Surrettes vs 1 year for the US Batt.; half the number of cells to water and check - and this is important as the maintenance on these 4 systems is being done by a third party who is not always reliably taking care of business; half the number of connections; half the footprint ... 

The only reason I can see someone recommending GC batteries in this scenario has to do with the company who set the systems up - Xantrex and their rationale seems to be the easy availability of the GC batteries e.g. in automotive stores etc. vs the more specialized distribution of the L-16's. Xantrex want to sell "arrive and drop" systems that will be sold through mass retailers from what I can see.

The Rolls d.o.d. at 80% shows 800 cycles for the 4000 series batteries vs. 675 on the U.S. Battery chart but the U.S. battery chart doesn't differentiate between GC batteries and L-16's or any other type so I find it a bit suspect.

Ron Young
earthRight Products - Solareagle.com
Alternative Energy Solutions ~ Renewable Energy Products


On 2011-09-16, at 1:06 PM, RM You wrote:

> forwarded from earth2
> 
> 
> Begin forwarded message:
> 
>> From: Ray Walters <ray at solarray.com>
>> Date: September 16, 2011 1:03:43 PM PDT
>> To: RE-wrenches <re-wrenches at lists.re-wrenches.org>
>> Subject: Re: [RE-wrenches] battery cycle life, US Battery
>> Reply-To: RE-wrenches <re-wrenches at lists.re-wrenches.org>
>> 
>> Larry, 
>> 
>> I totally agree, that's a ridiculous # of batteries and strings. If that's really the case, it seems L16s will still need 4 to 5 strings, which is also crazy. I see only one solution to this battery bank, and that is the HUP or other large 2 v cell battery. Comparing golf cart batteries to L16s isn't even on the plate for good design in this case. For me, HUPs become a no brainer, as soon as the required amp hours gets into the 1000 AH or higher range. BTW, don't ever use the 100 hr rate for the Rolls, as they are way too optimistic. The 20 hr rates are much closer to reality. The Rolls S-530 becomes a 400 AH battery at the 20 hr rate, also they list cycles @50% DOD, when everyone else is looking at 80%DOD, be aware.
>> Here's some quicky math, with costs pulled off the internet:
>> 3 strings of S530s (@24v) would get you 1200 AH for $4200. cycle life at 80% DOD about 450 to 500 cycles.
>> HUPs group 25 have 1270 AH and cost $7392, but last 2100 cycles to 80%DOD. 
>> That's about 11.5 cents/ kwh for the life of the battery compared to about 29.2 cents/ kwh for the Rolls S-530s. 
>> This quicky calculation doesn't even include the extra maintenance required for watering the L16 type battery, nor the fact that you will have 4 battery replacements for the same time the HUPs just have one replacement. 
>> Its very fair to say that the HUPs are more cost effective by about a 3 to1 ratio.
>> 
>> Ray
>> 
>> 
>> 
>>  Having 6-8 parallel strings of golf cart batteries is a terrible idea no matter how much better the GC2 may be.
>> 
>> Larry 
>> 
>> 
>> On Sep 16, 2011, at 10:01 AM, Ray Walters wrote:
>> The real point is that the Xantrex guy is correct from a scientific stance. Experimental battery cycle life data shows that some golf cart batteries (T105) do have more rated cycles to 80%DOD than the Trojan L16. (750 vs about 600) A really crappy golf cart battery (some have cycle life below 400 cycles) isn't as good as an L16, yes. You have to base your decision, and your mouth, on test data for the batteries considered. Also, you must always compare at 80% DOD, for an apples to apples comparison. Its usually a clue if a manu doesn't publish their cycle life data. Of course you must temper the golf cart vs L16 decision with good paralleling technique.
>> We use golf cart batteries (never more than 4 strings), jump straight to the HUPs for larger banks, and skip the L16s all together. They just don't make sense when you look at the cost/ amp hr vs their lifespan.
>> The only time I could see using L16s, was if the battery bank requirements were beyond 4 strings of golf cart batteries, and the customer just could not afford the HUPs, or were going to sell the property soon, and wouldn't appreciate their long term value.
>> I've spent a lot of time looking at cycle life data, comparing costs, adding in maintenance and replacement labor, etc..
>> L16s are serious losers on a $/ kwh operating cost comparison, so this is a chance to up sell the customer to HUPs (or equivalent) and make both of you happier in the long run.
>> 
>> Ray Walters
>> 
>> 
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