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Old 01-24-2009, 06:48 AM   #1
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Default A123 in my xxx-t

Hi guys, I saw a little stuff about the A123 batteries.

I plan to 3 news pack for my Matt Francis 2 truck and I'de like to have your advice on my battery selection.

I'll run it with Mamba 4600kv system.

I plan to buy : 3cell 5000mah lipo or A123 equivalent pack.

What pinion should I use on a small-medium track?

Is the runtime of a A123 2200mah 2s2p pack is the same as a 3cell 5000mah lipo pack?

I saw this pack, hard case... look great..

Help me please!!!
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Old 01-24-2009, 07:21 AM   #2
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Default a123

Don't know anyone who uses them. 100% of racers use the "regular lipos" Look into the SMC 5000+ mah 40C lipos packs they are the latest greatest. When I first started I tried the a123 thing and sent it back. Fun to mess with on the hobby asepcts but not a performance thing.
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Old 01-24-2009, 04:22 PM   #3
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Quote:
Originally Posted by ManiTouU View Post
Is the runtime of a A123 2200mah 2s2p pack is the same as a 3cell 5000mah lipo pack?
The lipo run time should be dramatically higher in this example. It's over double the amp hours, and nearly double the voltage, so something like 4 times the energy roughly. Note the different voltage would come into play, the 3s lipo would be burning up a lot of energy spinning the wheels I suspect. 3S with a 4600 is wicked powerful.

You mention a track, don't know if you are racing or not, but if so the 3s lipo won't be legal. As far as I know the A123 would be allowed, but I'm not sure. Maybe not, at least at ROAR events, they would need to be on the approved list. Wouldn't expect a problem at a non ROAR club race, A123 cells are lower voltage.
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Old 01-24-2009, 06:38 PM   #4
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I use A123 exclusively in 2 of our oval classes and I also have one of the larger 4600 packs in my son's XXXT.

You will be at a disadvantage on off-road since it's a 6.6v pack. It's closer to a 5-cell pack in speed.

Run time off-road is more than a comparable NiMh but not quite as much as the same capacity LiPo.

I love my A123 packs, but they are a purpose use pack that you have to have a very specific need to see the benefit. You would be better off with a LiPo in this instance.

I'm partial to the Yeah Racing packs, but the new SMC pack is also a great choice.
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Old 01-26-2009, 04:03 PM   #5
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oki guys thx a lot for your comments, I apreciate.

I'll use a 2 cell lipo for my truck.

I think a 20c pack is enough for this little truck? I use a 25c in my 1/8 buggy but I think that a 25c will be useless in this truck?

What are you thinking?

What pignion will be good on that setup for a small-medium tight track?

4600kv 2 cell lipo?
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Old 01-26-2009, 04:57 PM   #6
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I've been working with A123's in RC aircraft and helicopters since they hit the market. I've just started getting into RC cars and of course I'll try them here.

The trick to A123 is gearing UP considerably. A123's have a very flat voltage discharge curve regardless of the loads you place on them. Going up several teeth will give you the best results.

I'm running two cars right now on A123s. My firestorm flux runs 3S a123 (about equal in voltage to 8cell nimh). I clocked the top speed of the Firestorm at 48mph on pavement with a GPS. It's MORE then enough power, I can recharge this pack in 7 minutes and get between 10-15 minutes of runtime.

My wife recently got a Revo and she is running 4s2p and eventually 5s2p A123. She is getting over 20 minutes of runtime and I can recharge the packs in as little as 11 minutes.

I have no clue what A123 racing are selling. Those 2S2P packs look like the smaller size 1100mah cells doubled up. The other size of A123's are are 2300mah but they are slightly too wide to fit most battery trays. I get around this by cutting the battery tray or adding straps and wedging the cells in place.
You can get the 1100 cells out of Black and Decker VPX packs. Each pack contains 2 cells, you can find them on clearance for as little as 10 bucks. The 2300 cells come out of Dewalt lithium packs. You can purchase these on ebay and disassemble them.
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