Mixed Batteries

[Bayesoft]

My step-father works at a marine service garage.  He tells me that they throw out about 40 deep-cycle marine batteries a year because they won't hold a charge.  I told him that I would give him $5.00 for each of these batteries.  He agreed to the deal.

I'm thinking that they probably just need to be de-sulphated.  He has no clue about de-sulphating.  They just throw them out and replace them with new ones.  (Think high end clients with yachts and money to burn)

The problem is that I'm sure the amps won't be the same for all of these batteries.  Should I hold out for certain batteries with the same amps?  (or) Can I mix the batteries with different amps in my battery bank?  If I can mix them, how do I figure out the total amps and how should they be wired together?  With this potential supply, I have decided to go with a 24 or 48volt system.

eg; Lowest amps to highest, or vice versa.

[AbyssUnderground]

Always match up batteries of the same capacity. If you don't, you will be discharging the smaller ones more than the larger ones, which over time will damage then and cause the other batteries not to get a proper charge.

[Bayesoft]

Thanks...

[wdyasq]

(Think high end clients with yachts and money to burn)

THINK - 300 miles from the nearest port - storm she be a-comin' - boat no crankie because you were too effing cheap to $250 worth of batteries but spent $700 on fuel, $ on food, you family is on board and you can't do anything but watch the storm roll in!

Ron

[TomW]

Gee, Ron, tell us what you really think....

T

[wdyasq]

I think I forgot to put 'BUY' in front of the batteries and remark I don't like the coast guard saving folks that stupid.

Thanks for asking,

Ron

[vawtman]

Ron I think you would make a great battery salesman for us scavangers.Maybe also a coast guard job has a battery inspector.Buy a wallyworld tester and tell them the batteries must be replaced before setting out to sea.

 Adventure would be profitable planning.Hmmm

[electrondady1]

perhaps baysoft,  (being lower on the food chain like myself)  can use the desulfated batteries for something less than life or death  situations.

would it not be possible to set the discharge level to suit the lessor batteries and still have a viable battery bank in spite of having mixed capacities?

i'm guessing that it might be necesarry to monitor or control the charging of this melange in order to avoid over charging

[nothing to lose]

Yes you can mix batteries.

It's not a good thing to do for allot of reasons. But most advice about not mixing batteries is don't do it when buying brand new batteries at big bucks! The same reasons still apply with old used ones, but for the cost who cares.

Things like use batteries of same age, same size, etc.. is great when buying those new ones to get the max life and least problems when spending the most money!

At $5 a battery who really cares? As long as it works good, and if eventually you kill a battery a bit early because it was the biggest one or the smallest one in a mismatch bank then what are you out of, $5 so who cares? Not worth worring over enough to run out and buy a matched set of 10 brand new ones for $1000 when you can have 20  good ones for $100.

Use some sense though when mismatching batteries. Try to keep them all about the same amphrs close as you can. Don't mix a 115amphr and a 17amphr and expect much.

Match the types also, don't mix normal deepcycle Lead Acid with gellcells or AGM.

Try to match the age and sizes and conditions, a 2 year old battery may last longer and work better if NOT mixed with a 10year old. But if the 2yr old has been abused and holds the same usable capacity as the well treated 10yr old then might as well mix.

As long as you try to match them up close as you can it does not really hurt anything to mismatch scrap batteries, they just may not last as long as if they were all matched perfectly. Charge and discharge may not be equal when mismatched, check a bit more often. Larger batteries may need water less often then smaller ones. Larger may not fully charge at times, occasionly check and top them off to a full charge.

Mismatching is not the best thing to do, but I figure it this way, I buy a $5 battery and use it long as I can then sell it for scrap at $5 and I am out of nothing and gained however much life it gave me. I do try to make them last a good long life, but I don't try to the point of doing without or buying a matched set of new ones!

[cabinfevor]

I've got a question about mixing batteries as well. While I agree that mixing different sizes and batteries of different ages is not a good idea because the load on the batteries will discharge them at different rates. I think the larger the load and the smaller the bank would be more noticable than larger banks with lighter loads.

My question pertains to charging multiple banks from either a inverter/charger or a solar array. I've got two pretty good size battery banks. The first one is made up of 10 MK 8A4D 12 volt AGM batteries (200AH each) wired series parrallel for a 1000 ah 24 volt bank. The second bank is a bit smaller, it's made up of 16 6 volt golf cart batteris that I bought from Sams. They are 190 ah each wired series parrallel for a 24 volt 760 ah bank. Both banks are wired to a selector switch that I can run either or both. There for I can charge either or both from the inverter. The load side of the selector switch feeds a 250 amp CB that feeds the inverter. On the line side of the CB I have my solar charger connected. The solar array is 350 watts and I am using a xantrex C40 cont4oller. Small array in comaparison to the size of the battery banks.

This wiring arragment allows me to use the solar charger on which ever battery bank is selected. Aventually I would like to add a second charge controller and more panels so that I could charge either bank regardless of if it was being used.

I just recently installed the solar charger and panels to keep the batteried topped off while I'm away, as this place is an off grid get away for me so I'm not always there to keep the bateries topped off. I had been runing a genny to keep them charged. While I'm not there I curretnly have the 250 amp CB turned off but the smaller of the banks, the wet acid golf cart batteries is still on at the selector switch so the solar array will keep them topped off. I'd like to try it with both banks selected so the array keeps a charge going to both banks. I don't think that it would cause any harm. I'm figuring he samller bank will top off first and partialy discharge while the larger bank pulls from it at night but that in the long term both banks should reach float voltage. Any comments from the experts?