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Old 23rd September 2003, 10:18 PM   #1
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Default charging 3x 12V batteries in series.

I have a 36v battery supply using 12V 5Ah SLA batteries in series.

What is the BEST way of charging these batteries? Easiest way?

I don't want to end up with 1 battery with 15v and others with 11v etc...

can I connect say 3x 130 ohm resistors across each battery and use a 40v voltage regulated supply?

would the 130 ohm resistors even out charging current after the current has dropped below 100mA?

Thanks!!
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Old 23rd September 2003, 11:02 PM   #2
cowanrg is offline cowanrg  United States
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i am finishing my battery supply for my pre-amp. it runs off of 60v supply.

what i did was take 5 12v batteries and wired them into 5 relays in a series, and in parallel. the the relays get power, the batteries are wired in paralell, to charge. then the relay is off, they are wired in a series to give 60v to the pre-amp (or whatever).

its pretty easy to do if you can get the relays cheap, and you dont have to really do a circuit for it. its the minimalist way i think. the batteries pretty much charge at the same rate they normally would. i have a 70va transformer running the charger, which is a pretty beefy one. it works well. pics coming soon.
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Old 24th September 2003, 03:37 AM   #3
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Default schematic???

Oh... this sounds interesting, do you have a schematic??

problem is, isn't the relays in the signal path?

any other ideas??

TXS!!!
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Old 24th September 2003, 04:04 AM   #4
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What I learned is that if they are discharged in series, they can be charged in series. After all a 12 volt battery is a series string of several cells. However if the series battery string has multiple "taps" where on part is discharged differently than ther parts, it's best to charge them in parallel or you risk overcharging part of the string.


Here's a thread in sci.electronics.design:

http://groups.google.com/groups?hl=e...3DN%26tab%3Dwg


Sheldon
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Old 24th September 2003, 04:17 AM   #5
Duo is offline Duo  Canada
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here's a thought.

There are six cells in a car battery of 12V. They are all wired in series.

Logic would state that you could have 12 cells or more couldn't you?
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Old 24th September 2003, 04:33 AM   #6
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my thoughts guys....its fine to charge batteries in series but what happens is that if one battery goes bad it affects the others....I`ve ran into this problem in Industrial applications

The best way but alittle more initally expensive is to charge them in parallel and current limit each battery off one supply so they dont draw more than another....you can also meter this way if a single battery is trying to over charge and also you can fuse each battery in the charging output to save the charger in battery failure

hope this helps


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Old 24th September 2003, 04:37 AM   #7
cowanrg is offline cowanrg  United States
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Default Re: schematic???

i dont have a schematic, but i will have pictures soon.

yes, the relays are in the signal (power?) path. however, the only components to the PSU (in the path), will be batteries and relays. they are solid state relays. i might go mechanical, dunno yet.

it is much better than having a transformer or caps in the signal path though.

Quote:
Originally posted by RichJones
Oh... this sounds interesting, do you have a schematic??

problem is, isn't the relays in the signal path?

any other ideas??

TXS!!!
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Old 24th September 2003, 11:10 AM   #8
advance is offline advance  Switzerland
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Quote:
What I learned is that if they are discharged in series, they can be charged in series...
Correct, If you use the same type and age! On these conditions I never had problems charging batteries in serie, which
I am using for several years in my preamplifiers and power amplifiers!

Details for the Battery Supply/Charging Unit I am using:

- Schematic Diagram (PDF, 11 KB) : http://home.tiscalinet.ch/cooltune/P...CLP-BSU1aS.pdf
- Printed Circuit Board (PDF, 128 KB) http://home.tiscalinet.ch/cooltune/P...LP-BSU-1aP.pdf
- Bill of Materials for 4 x 12V, 2 x 12V & 1x 6V PCB (PDF, 9 KB) http://home.tiscalinet.ch/cooltune/P...CLP-BSU1aM.pdf

Hope this helps...

advance
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