How do I lower the voltage of 2 12V batteries to 18V

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How do I lower the voltage of 2 12V batteries to 18V

Postby Captain351 » Fri Mar 30, 2012 1:00 am

OK so I have graduated to larger electrics and I have a couple of 6 cell packs and a new battery charger the problem is that my charger need 18 volts to charge my packs. I have an AC power supply that I can use at home but I have gotten into the habit of doing most of my charging at the field! I tried to connect 2 deep cycle batteries in series but my charger say "over voltage" when connected this way. What is the best way to lower the voltage to 18V?. I have found several DC\DC converters but they either can't handle the amperage or cost a months wages! Any ideas anyone!
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Re: How do I lower the voltage of 2 12V batteries to 18V

Postby adeptrc » Fri Mar 30, 2012 2:39 am

How many amps do you need? You could put a few devices like this in parallel (maybe with some 3A schottky diodes on the outputs for protection) http://www.ebay.ca/itm/LM2596-DC-DC-Ste ... 0954117473

They're only a couple of bucks, shipping included.
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Re: How do I lower the voltage of 2 12V batteries to 18V

Postby Aussie Joe » Fri Mar 30, 2012 3:29 am

You will find that most (smart) chargers will automatly boost the voltage up from 12v when charging packs of more than 12v. 12v input---25.2v output (peak voltage 6cell).

If you could let us know what charger your using, me or someone else could give a definitive answer.

Cheers
Joe
"Photonicinduction" One man and a plug socket = Mayhem. http://www.youtube.com/user/Photonvids?feature=watch
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Re: How do I lower the voltage of 2 12V batteries to 18V

Postby Captain351 » Sun Apr 01, 2012 8:42 pm

My deep cycle battery has a 30 Amp fuse on it that has never blown so know 30 Amps would be enough. The DC/DC converters that you showed me were great but the best I found could only do about 8 amps. 4 of them in parallel would give me what I need but I am concerned that they won't like being used in parallel.

My charger has a voltage max of 18 volts but if you only give it 12 volts it can't reach it's maximum charging rate. I want to charge a 6 cell 4500Mah pack at a 2C which would be 9 amps my charger will only give me 5 amps at 12 volts if I give it 18 volts it will do 12 amps. When I do the math and try to relate it to the actual wattage rating of the charger nothing seems to work what a surprise!

I prefer not to say what charger I have because opinions and assholes happen in about the same frequency and I have no desire to defend my buying decisions!

Thanks for the help but it looks like I may have to engineer and build this myself. Probably won't get it done this summer that's why I wanted something simpler and easier (quicker).

Captain
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