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.

[zmoz]

"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."

Exactly what I'm thinking. I'm just wondering if the advantage of higher amp hours is outweighed by the fact that it's a starting battery.

On the other hand, I'm thinking the only difference between the two batteries is that one is physically larger, giving it more CCA, and they just decided to call it a starting battery when in reality the construction is the same.

[nothing to lose]

I think you said they both have CCA listed, just one called starting battery also, but both supposed to be deepcycle.

If I only had the choice of the 2 I would either buy 2 of the smaller ones (more money/more amps), or 1 of the bigger ones figuring the percent of drain and rate/speed of charging to be lower than just one of the smaller ones.

I would also read the file mentioned first, which I haven't done yet. I'll download and read it also myself.

[nothing to lose]

Very interesting,

On the last 2 pages showing 3 battery wirings for series and parralel and both I did not see the way I had my 6V trojans wired up nor the way I had my 3 12V deep cycles either. I geuss I will change them to the way shown and see if it make any difffernce.

Basically for the 6V series parralel setup I had + - + -  on a row. I joined the center

- + together to make a 12V bank of each set of 2, then ran all the outer + posts to the front battery and all the outer - posts to the front battery. I connected the load to the front battery also. I theory running all the POS to one point and All the Negs to one point, just happen to be the point was the front battery.

Think that worked well, bad, or no difference? It worked, but don't know how well compared to other ways of wiring them up. If all the batteries were full capacity it would have been about 1,000amphr bank at 12V.

They were all scrap yard batteries though so not full capacity, but worked well.

I also did 3 12V the same way, each pos to the front and same with the negs and connected the load at the front battery. I just did not have a center connection since they were 12V.

The 12V ones and 6V trojans were for 2 different systems, not mixed together.

I am moving it now, Just brought home the 5k inverter from the remote house and a bunch of other stuff today too.

[zmoz]

I contacted Johnson Controls about these batteries. They said the batteries are both the same, except the 115ah has 1 more plate per cell. That means it should last just as long as the 85ah, given the same % of discharge, right?

[BT Humble]

If you're putting together a 12V/600Ah battery bank with these cells, you might want to consider how many plugs you'll need to undo, check, and top up with water every month (I'm assuming these are flooded cells).  Also, most of the sites I've seen which talk about how to build a battery bank recomend that you run no more that 2 strings in parallel.

You'd need 8 of the 75Ah, or 5 of the 115Ah (approximately), which is 18 fewer cells.

My own bank is two strings of 2V 550Ah cells, giving me 1100Ah at 24V.  Topping these up is a non-trivial business, even though I only have to deal with 24 cells the last time I did it I needed 20 litres (5 gallons) of distilled water!

BTH

[nothing to lose]

That is interesting, exactly the same other than one more plate.And that one plate is adding how many extra amps? 85 or 115, so one plate here seems to be adding 30amps.

 May be nice to know things like that if I ever try to build a good battery from junk ones

Yes, if that is the only difference, then of the two I would buy the larger one maybe. As already mentioned in a big battery bank it would be less filling and cable cleaning etc... for fewer larger batteries. Also less cables needed.

I geuss it's somewhat of a coin toss which a person would rather have for a larger bank, for just 1 or 2 batteries figuring the same loads and charge rates as mentioned earlier then I would go for the larger ones.

[nothing to lose]

"Topping these up is a non-trivial business, even though I only have to deal with 24 cells the last time I did it I needed 20 litres (5 gallons) of distilled water!"

I hope your using waste heat to boil water to make your own distilled water

[zmoz]

The battery is also larger...group 27 vs 24, that's where the extra capacity comes from. What I think he means is that the plates are the same thickness and construction in each battery.

BTW - I'm not building a battery bank with these, just one for a portable homemade inverter generator.

[ghurd]

Check the golf places.

They should be able to get a good deal. Accidental RE dealers.

Next is the boat places (ouch!).

But the K-Marts should be moving out the old batteries any minute. Boat season is just starting.

G-

[ghurd]

Also check this

http://www.fieldlines.com/story/2005/4/23/215521/513

[BT Humble]

I hope your using waste heat to boil water to make your own distilled water

No, but I did discover that it was considerably cheaper to find a brand of drinking water in the supermarket that claimed to be "triple distilled, not filtered!" - it was about 1/3 of the price of bottled distilled water for batteries, and I could buy it 10 litres at a time. ;-)

BTH

[DrMemory]

I think you need to return to the original question -- is there a difference?  The answer -- no.  They are all true "deep cycle" batteries.  They only list CCA because all "automotive" batteries sold must list it per Governmint regulations.  Just like the octane on the pump, and the true RMS Watts on a stereo.

DrM

[ghurd]

Most people using batteries will say there IS a very big difference.

Or we would be using the $29 starting batteries.

Which most of us probably tried, regretably.

I admit I tried them...  once.

Just once.

G-