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Batteries & Chargers Discuss Li-P, Li-Ion, NiMh, Nicad battery technology and the chargers that juice 'em up!

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Old 01-20-2011, 03:35 AM   #1
Razmo
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Default High Rate Field Charging Suggestions...

Hey Guys,

I'd like to be able to charge large lipo packs at the field that allow for high rate C charge, rather quickly.

Now, this can be accomplished at home rather easily using a high watt power supply. My question, does anyone know (for example) whether I can accomplish a powering my charger at a consistent 1000 watts using a 12v (or two wired in series) car type battery(s)?

I came across a 12v deep cycle battery at Batteries Plus rated at 80amp hours, however am curious whether this equates to a constient 960 watts? (12v x 80a = 960w)..

Thanks,
Raz
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Old 01-20-2011, 05:13 AM   #2
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Originally Posted by Razmo View Post
Hey Guys,

I'd like to be able to charge large lipo packs at the field that allow for high rate C charge, rather quickly.

Now, this can be accomplished at home rather easily using a high watt power supply. My question, does anyone know (for example) whether I can accomplish a powering my charger at a consistent 1000 watts using a 12v (or two wired in series) car type battery(s)?

I came across a 12v deep cycle battery at Batteries Plus rated at 80amp hours, however am curious whether this equates to a constient 960 watts? (12v x 80a = 960w)..

Thanks,
Raz
What charger are you using to get a 1000 watts? From what I'm aware, only the Cellpro powerlab 8 has a 1000 watt charger. Their high power Cellpro 8 requires two 12 volt Deep cycle batteries in series for 24 volts to get that 1000 watts.

I've been using a 120 Ampere Hour deep cycle marine battery for several years, and have worn out several of them, charging my 6S2P A123 battery packs.

Also found that some of those deep cycle batteries might not last to long. Don't buy those "Deep Cycle Engine Starting" batteries. Mine lasted about 3/4 of a year, when it lost 75% of its 120 Ampere Hour capacity.

Right now, I'm using two deep cycle marine batteries in parallel, (no engine starting rating). (Some of those engine starting deep cycle batteries from as an example wallyworld are nothing but standard automotive batteries with carrying handles)

Take a look at my thread on this:
http://www.wattflyer.com/forums/showthread.php?t=48469

Also take a look at this on electrifying models of the 70 glow engine size:
http://www.wattflyer.com/forums/showthread.php?t=45222

Note that if you are pulling 1000 watts out of a 24 volt battery, that's 1000 watts/24 volts or 41.6 Amps. And, if that's a 12 volt battery, that's 83 Amps. Not many deep cycle batteries can handle that high of a continuous current.

Guess the bottom line is, buy a high quality 120 Ampere deep cycle battery, or two if you are planning to run 1000 watts. They will need to be connected together with fairly heavy guage wire, like auto jumper cables. I bought a pair of copper jumper cables, and fitted them with the large size Anderson Power Pole connectors as quick connect and disconnects.
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Old 01-25-2011, 02:37 AM   #3
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Sorry for getting back to you so late, thanks for this information. Very helpful.

The Charger is the Voltz 101K. I actually just ordered one today.

It sounds as if I'll be able to draw continuous amperage from a battery (or batteries) needed to sustain 1000watts. I'll take a look at the threads you've attached for more information. Do the deep cycle batteries you use offer a continuous amperage spec? Otherwise, I'm not sure I understand how to calculate sustained watts. Can you suggest a 12v and/or 24v deep cycle battery?

Also, would a 120amp hour battery supply approximately 120,000 milli amp hours?

Thanks,
Raz
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Old 01-25-2011, 03:51 AM   #4
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Originally Posted by Razmo View Post
Sorry for getting back to you so late, thanks for this information. Very helpful.

The Charger is the Voltz 101K. I actually just ordered one today.

It sounds as if I'll be able to draw continuous amperage from a battery (or batteries) needed to sustain 1000watts. I'll take a look at the threads you've attached for more information. Do the deep cycle batteries you use offer a continuous amperage spec? Otherwise, I'm not sure I understand how to calculate sustained watts. Can you suggest a 12v and/or 24v deep cycle battery?

Also, would a 120amp hour battery supply approximately 120,000 milli amp hours?

Thanks,
Raz
Most lead acid batteries are rated for a 20 hour discharge cycle, so based on that, you can only pull 120/20 or 6 amps out of one to get the rated 120 ampere hours. As a wild guess, if you discharge the battery in 3 hours, you might get 80% capacity or so. That would be 120/3 or 40 amperes.

You are correct, 120 ampere hours is the same as 120 times 1000 milliamperes per ampere, or 120,000 milliampere hours.
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Old 01-25-2011, 10:45 PM   #5
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Hmmm, it sounds like maybe a generator may be the better choice?
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Old 01-26-2011, 12:50 AM   #6
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Originally Posted by Razmo View Post
Hmmm, it sounds like maybe a generator may be the better choice?
Interesting:
Back in the 1980's I did rewind an automotive generator, and working with a microcontroller circuit, made it into a constant current charger for 38 series Nicad cells. The system was set up with a five ampere charge rate, and when the nicad cell's voltage dipped by about 2%, it killed the engine. The maximum charge rate was limited by the 3 horsepower Briggs engine. Much higher than five amps, or 38 cells, the engine stalled.

Would not take much to make a Lipo charger out of it, but I'd have to rewind another alternator for higher current outputs. A pair of 120 Ampere Hour deep cycle lead acid batteries is a lot simpler, and a lot quieter!
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