7XL , run 5s2p or 4s3p pack?

[neweuser]

Very nice! Thanks man. I love my LIPO though. My 5s ran strong until they dumped too. This is a really good thing, it's like nitro cuz you have constant power until they dump, not like Nimh cells that slowly get slower and slower.

[jhautz]

Originally Posted by zeropointbug

http://www.modelelectronicscorp.com/products.html

http://www.a123racing.com/

At A123Racing website you can buy either loose cells, and you can buy the pre-assembled packs of which you can get the Turbo versions; which is a variable voltage circuit (very snazzy!) you can adjust the voltage and the voltage will be stable under load (i think it has no Volt droop).
Or you can build your own pack and attach a balancing cable for the chargers they sell.

I however do not use a balance cable (not near as critical as Li-Po), i use a BK Precision lab power supply to charge my 5s2p pack in 25 minutes. It's great, they stay room temp while charging too.

One of the best things about the A123 M1 cells is that they seem to deliver 100% right until they dump, its very abrupt!

Be careful with that turbo box that A123 sells. A123 doesnt recommend it for brushless setups cuz artificially bumping the voltage increases the amp draw and a high powered brushless can already push the cells without the added load. At least thats what they told me when I called to inquire about it.

[Finnster]

Yeah, thought I'd read that the turbo is only good for ~10A..


As far as the MMax goes, its also a heck of a nice controller, and while I use 5s on it, I'd only recc a max 14-15cell or 4s lipo setup. 5s is really pushing it. For the voltages you are looking to run, the Q125 is perfect.

[zeropointbug]

From what i know, and what they say is that they run at the rated cell 30C discharge. Personally though, i am running a CCCV power supply that charges the batteries perfectly and the most reliably than any charger. However the BK Precision P.S. that i bought was $300, so its not for everyone, however i can charge any battery i want with it...

http://www.bkprecision.com/www/np_pdf.asp?m=1696

Mine is the 1696 version with 0-20V, and 0-10A, completely programmable on the unit or from PC.

Anyhow, i have decided that i will stick with the 5s2p pack setup, it's a good mix of power and runtime and i can charge in 30 minutes. So it's pretty fast and easy charging.

[jhautz]

but a 2300 mah pack at 30 c is only 69A. the voltage turbo box just makes it worse. I wouldnt run a pack @ less than that. and the turbo box will make it worse.

[zeropointbug]

yes, that is true. But you would never run one by itself, you want to run at least two in parallel. Not to mention that it would have horrible runtime too running 2300mah :(

[BrianG]

Yeah, that turbo box is simply a switching power supply (or maybe just a boost switcher). So, just using it reduces battery efficiency by about 5-10% just from the circuit losses.

[MetalMan]

Originally Posted by neweuser

I can't find A123 cells anywhere? Metal, you are going 5s on a 7xl?

They're the same cells found in the Dewalt 36V packs. You can find them on Ebay.