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JimClark
12-17-2005, 09:58 AM
I was wondering what advantages or disadvantages would there be in a using lipo's in a high amp draw application with 4s1p 4200mah 14.8V batteries versus 2 packs of 4200mah 7.4Volt cells?
thanks in advance
Jim clark

ragbag
12-17-2005, 12:17 PM
MHO?

I think it would be easier to maintain the balance of the packs and help with the cooling.

Seems to me the last couple of packs I have had go bad were the inner cells of the 3s1p versions. Not enough to say it was all the time, but enough to create a question.

They are vintage packs, so the age might be the problem???

.02 worth
BY George

Rugar
12-17-2005, 02:48 PM
I was wondering what advantages or disadvantages would there be in a using lipo's in a high amp draw application with 4s1p 4200mah 14.8V batteries versus 2 packs of 4200mah 7.4Volt cells?
thanks in advance
Jim clark

Advantage for a single 4S pack:
Can use without a series connector.
Can charge as a series pack.
One battery to charge and monitor instead of two.

Advantage for two 2S packs:
Can use a single 2S pack in another application.

Probably lots more but its early and I'm on my first cup of coffee ;).

Jim McPherson
12-18-2005, 07:01 AM
There might be a few other things to think about.
Connecting 2, 2 cell packs means tripling the number of connectors you have to use. All connectors have some loss. This is negligable but still present.
More connectors also gives more to go wrong. Unless you use bullet connectors or Sermos, you'd need to have a wiring harness as well.
Then there is the mounting issue. It's much easier to mount 1 pack then try to secure 2 packs. However this could also be an advantage if you need to be creative on your mounting scheme.

Electrically speaking, probably no noticable difference in performance. Practically speaking, probably easier to use/charge a single pack.

-Jim

crash_alot
12-18-2005, 04:25 PM
In order to charge a 4S pack, a charger with more than 14.8 input volts is necessary. Many lipo cnargers work from "12V" (actually about 13.5V) car batteries or equivalnt supplies. As such, these chargers will not bring a 4S pack to full charge. If your charger's input voltage is greater than 15V things should be fine. I use two 7.4V packs in series and charge each seperately. A little more complicated, but full charge of each pack is assured.

everydayflyer
12-18-2005, 04:38 PM
A little clarification may be in order here. It is not the charger's input but the charger's output which must be greater than then total charged voltage of the battery.
Most LiPoly chargers have a voltage multiplier circuite in them which takes care of this need. There are many $50 LiPoly chargers which will charge 4S LiPoly with just a 12V input (11.5 - 15V is the normal required input range). The Astro Fligt 109 and some other high end(?) chargers will charge 9 or more LIPoly cells in series from this some input voltage range.

Charles