12v DC in series question

Rexmaster

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Jul 13, 2014
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Hello,

I have 2 12v DC batteries connected in series to power my 24v application. I now need to add wiring that uses just 12v for something else. This is easy enough to do. But, my question is, what will happen as the 1 12v battery I connected to drains faster than the second battery that make up the series? Will the stronger battery try to charge the weaker? Or will my 24v application now be limited by the juice left in the lower single 12v battery?

Appreciate your time!

Rex
 

yellow

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the "12 V" battey will be drained faster
(by the 12 V use and by 24 V use also),
as a result the 24 V application will last shorter, with the 2nd battery not being discharged down

no "charging" the "weaker" battery, as this would only happen when connected in parallel
 

WalkIntoTheLight

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You also run the risk of damaging the "weaker" 12v battery if you drain it too much. It could even become reverse-charged and ruined.
 

Conte

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You would also have to charge them separately.

How much current are you pulling off the 12v application ?

This reminds me of a diesel engine retrofit.
 

tpcf

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Jan 15, 2013
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Consider getting a DC/DC converter to safeguard the batteries' health, You can find cheap ones on ebay if the load is a couple of Amps
 

AnAppleSnail

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/!\ Don't get clever and try to run your load off 'both' 12v batteries while they are hooked to 24V in series! A quick check of the circuit diagram will save you, but if you're the act/check/plan type instead of the plan/check/act sort, you'll save some trouble reading this.
 

Hashime

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I highly suggest running in parallel and tossing a boost driver in there.

This is current dependent of course.

If you are under 100W you can find drivers off the shelf. You can also find battery protection circuits.

That being said SLAs are pretty forgiving as long as you don't pull them too far out of operating range.
 
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