Parallel charging a series LiPo pack? - Page 4 - RC Groups
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Sep 01, 2004, 12:45 PM
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Larry3215's Avatar
Quote:
Originally Posted by Dan Baldwin
My li poly charger has a drop out of about 1.5 volts, so a 5 volt power supply wouldn't work. I could design one based on a 5 volt supply, but it would be more complicated, and, like Quacker, I can't do it very quickly.

Dan
Darn. Lots of 5V and 12V options at low cost. The 6.5V one I found is $9.00. Still less than parts, but not as low as I would like.

How much trouble to drop down or use the 12V input?
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Sep 01, 2004, 12:52 PM
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Dan Baldwin's Avatar
Actually I gave it some thought, and I came up with a design that is still simple, but has virtually 0 drop out. I won't post that one until I get a chance to at least breadboard it. I'll need a few days.

Dan
Sep 01, 2004, 12:55 PM
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Larry3215's Avatar
Very good!

Larry
Sep 01, 2004, 01:25 PM
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Pardus


Check this thread.
https://www.rcgroups.com/forums/showthread.php?t=269638
Sep 01, 2004, 01:26 PM
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Larry3215's Avatar
Quote:
Originally Posted by Quacker
kit,

Doing isolated chargers from a single 12V supply is not so easy and yes, the heat dumped by the regulator would be plenty.

My intent was to make something that could be built up for 3S packs. If you do the math, it's not all that bad compared to a commercial, non-isolated lipo charger that will do 3 amps. There are cheap 12VDC to 115AC inverters you can get so you can use them in the field if you like.

I could have designed seperate chargers with high frequency down-converters for 12V use, but that gets a good bit more technical and not that much cheaper. It would be smaller though.
I had missed this comment before:
"I could have designed seperate chargers with high frequency down-converters for 12V use, but that gets a good bit more technical and not that much cheaper. It would be smaller though"

This sounds interesting as an option. Where could I look for info on these down converters?

Larry
Sep 01, 2004, 03:52 PM
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Dan Baldwin's Avatar
I posted the 2 cell simple charger in the DIY Electronics forum.

Dan

https://www.rcgroups.com/forums/show...95#post2581595
Sep 01, 2004, 04:01 PM
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There are some surplus adjustable 5v (down to 4.2 V) switching power supplies out there cheap, all U have to do is add an adjustable current circuit to it.
Sep 01, 2004, 04:20 PM
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Dan Baldwin's Avatar
The balancer has been posted as well
https://www.rcgroups.com/forums/show...94#post2581694

Dan
Sep 01, 2004, 04:25 PM
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Dan Baldwin's Avatar
Larry;
I was wrong when I said that I would be able to get to near 0 drop out with a simple circuit. Op amps would be involved, so it would be similar in complexity to Quacker's design. I can get drop out down to about .7 volts fairly easily though, and that should work fine for a 5 volt power supply. I'll play with it within a few days. The circuit I posted would work fine charging a single cell from 12 volts (resistor values would have to be changed), the only problem would be that much more heat would be generated, so it would take a larger heat sink, probably with a fan.

Dan


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