Homebrewed Electricity > Storage
Deep cycle VS Deep Cycle/starting batteries
zmoz:
I am looking for a deep cycle battery to add to a generator I'm building. Costco seems to have the best prices around here for them, $43 for an 85AH group 24 deep cycle, or $59 for a 115AH group 27 deep cycle/starting battery. Both are made by Johnson Controls.
I know that generally, deep cycle batteries are better than the combo batteries, but they don't have a 115AH battery that isn't a combo. Do you think there is really a difference between those two batteries, other than the physical size? The group 24 is still rated at 700CCA, the 27 is rated at 750.
Basically, what I'm asking is which will last longer given the same number of amp hours used per cycle? Both would be charged at about 20 amps by my generator...
scottsAI:
Take a look at:
http://www.fieldlines.com/comments/2005/4/1/51529/09358/2#2
Might be helpful. I did.
Any battery with 700CCA, type rating is not a true deep cycle battery.
I didn't find Costco to have the best prices for batteries.
The cost per whr to be a very good way to compare batteries.
Have fun.
picmacmillan:
here is a battery file in my photo upload section..very in depth from tazman.com http://www.otherpower.com/images/scimages/1135/battery_chapter.pdf this has all kinds of material and you can make your own decision after reading it on what you should or should not do with your batteries...good luck..pickster
zmoz:
There's no Sams club or Walmart around here. About the only other choice for deep cycle batteries is K-mart, who wants $70 for a 115AH that's already been sitting on the shelf for a year. I think pretty much every department store deep cycle battery has a CCA rating on it...
nothing to lose:
This may be a good time to contact the manufacturer and see how good their service and support is :)
The first battery is 85amphr/ $43 = about $1.98 per amp
Second is 115/$59 = about $1.95 per amp
So really price wise I myself would call them the same price (figuring amps), and depending the power needs and the number of amps I was planing to buy I might go for the slightly more expensive deepcycle #1. Based on 100amps your only talking $0.30 difference in price. So for about a 600amps bank I would buy more of the smaller ones instead of the larger ones, only $1.80 difference buy the amps, course then you need more cables, but I expect the life to be longer and also cheaper to replace 1 if it dies for some reason. Less self discharge etc..
When buying new batteries I just don't like anything that says starting on it really. Used batteries I take anything that holds a charge :)
"Basically, what I'm asking is which will last longer given the same number of amp hours used per cycle? Both would be charged at about 20 amps by my generator..."
Considering this, I might say the larger may last longer. If you use the same number of amps and charge at the same rate, then the percentage is far more against you on the lower amps than the higher amps. If your only planning one battery, but it averages out agian if adding many batteries for high amps.
In other words say a 50amp drain would drop the 84 amp battery to only 42% charge.
but a 50amp drain leaves a 115 amp battery still with 57.5% charge.
The deader you run a battery and the more often will probably shorten it's life, and that's about a 15.5% difference in how dead your draining them.
Then also figure charge rates, 20 amps is C4.2 on the 84amps and C5.75 on the 115amp, so the longer/slower the charge rate considering the amps of the battery proabably the longer it will last also. There is a difference of C1.55, so I think the larger would last longer. If I figured that correct, if not then the numbers are wrong but still the same facts basically.
Now if adding several batteries for a small bank like 600amps, then I think it all averages out the same again basically, as you have more smaller or less larger ones, and the total amps are all the same. So again I would go with the smaller deepcycles I think.
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