36V Battery for $400? Which ones best?

[dimitrib90]

Im looking for a 36V battery that is capable of peak 90 amps for my RC motor. I have $400 to spend on this 36V preferably 20ah battery. I was thinking LiMn but I dont really know if thats the best way to go. Any ideas?

 

[pwbset]

$440 (plus possible mad live.com/ebay rebate savings taking it down as low as $308 would net you 8 Bosch "36v" fatpacks. If you don't mind harvesting the raw cells you could get a nice 10s 37v nominal pack @ around 17.6ah which is like 5.1C for 90a... easily within these cells tolerances. You could even pick up a cheapo Lipo 37v (42v max) charger to pump it up with.

http://is.gd/c62A

 

[dimitrib90]

$440 (plus possible mad live.com/ebay rebate savings taking it down as low as $308 would net you 8 Bosch "36v" fatpacks. If you don't mind harvesting the raw cells you could get a nice 10s 37v nominal pack @ around 17.6ah which is like 5.1C for 90a... easily within these cells tolerances. You could even pick up a cheapo Lipo 37v (42v max) charger to pump it up with.

http://is.gd/c62A

I was definitely thinking about doing this when the rebate was 25% but now it is only 8%. But I think Im still going to go with 4 Bosch packs and then buy a couple more when I get more money for Christmas.

 

[oofnik]

You know you're asking for like $.55/Wh. That's pretty damn hard to do. Especially if you want >3C discharge rate.

Closest I could find were these guys. An 12s18p pack of these would cost $388. But that's 216 18650 cells you'd have to solder.

I thought you were going with the Headway cells? Or what about that Saphion source of yours?

 

[dimitrib90]

Since $.55 p/wh is not practical, Im thinking about going with a 36V 10ah lithium manganese. I should easily be able to do that with the Bosch fat packs.

 

[oofnik]

Check the link I sent you before you do that.

 

[vanilla ice]

What are those 40grams each, so like 4.45 pounds per 50..

19 pounds for a 216 pack.

 

[pwbset]

Closest I could find were these guys.

Then you have to worry about a BMS which = more $ and more complexity. With the Bosch konions you can just wire'um up and ride and they will happily do way more than 3C. That makes them pretty darn attractive. With a good live.com discount you're in the $0.55/wh range.

I thought some forum member here got a bunch of those Voltphreaks cells and was disappointed with their output or something... can't find the thread right now, but will edit if I do.

 

[oofnik]

Yeah, he tested the high capacity cells which aren't rated for >3C discharge. The ones I linked to are high power.

A 12-channel BMS isn't quite that difficult to come by - and though Konions don't need balancing, LiFePO4 lasts much longer. So, one must decide which is more important in their application. Both cells have their pluses and minuses.

 

[dimitrib90]

The problem that Im having is making something that will charge quickly enough for my new rc setup so that I can travel to school, charge the battery pack, and travel back.

The other problem is money. LiMn is so far the cheapest way to get LiFePo4 and I dont even need a BMS!! Headway cells would be great if I had a BMS that I know would work perfectly with them.

I think Im going to wait about 3 or 4 months for the new lithium battery packs coming out. That way Ill have enough money to get the best.

 

[dimitrib90]

Li-MN for so high discharge rate is not very safe.

WoW, 90A constant current, 30AH high rate LiFePo4 can hold it, constant 3C.

I dont need 90A continous :lol: What Im looking for is something that will give my rc motor a little juice when I go up a really steep hill for a couple of seconds. I will probably be running somewhere around 40 to 50 amps continuous.

 

[etard]

I was looking on ebay and I saw some Bosch 36 volts going for $59 for the Fatpack which is 2 ah I believe. If you buy 4 and get 2 chargers that should come in around $300. I'm thinking of doing it myself.

 

[dimitrib90]

I was looking on ebay and I saw some Bosch 36 volts going for $59 for the Fatpack which is 2 ah I believe. If you buy 4 and get 2 chargers that should come in around $300. I'm thinking of doing it myself.

I was thinking the exact same thing. Im was quoted $50 per pack if I buy 10 packs. Ill take 5 packs and you take 5. I was going to use this charger.

http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=4211

I might go with a Bosch charger because it charges so quickly.

Why did you want 2 chargers?

 

[etard]

Dimitri,
So we save a total of $25 each? Minus cost of shipping to whomever does the footwork, sounds pretty good. Are these being fazed out by Bosch, or are they keeping the 36 volt line? I wonder if the price will keep going down. I wanted two chargers so that I could parallel the chargers to get charged in about an hour. I think John in CR did that successfully. But yeah, 5 batteries should be enough for my needs. Can anybody verify the 2ah rating, it seems I read somewhere that it was closer to 1.8?

 

[pwbset]

Can anybody verify the 2ah rating, it seems I read somewhere that it was closer to 1.8?

The VT cell is rated for 1.1ah and the Bosch fatpacks are 2p so 2.2ah max in theory. I got a couple used VTs and before I fried my CBA I saw just shy of 1ah under heavy load (at like ~8C... was ~30w discharge if I remember right) from a single used cell so I think you'd see a practical 2ah a pack for sure. 1.8ah seems a little low unless there is some circuitry cutting out at a higher LVC or because the Bosch chargers only seem to charge to 40.5v instead of 42v, which is the most likely case. It's likely the 18650VT cell is only rated to 4.1v/cell like it's bigger 26650VT brother, but charging it to 4.2v/cell shouldn't kill it too much over time I would think.

Do let us know what you learn over time. I'm really thinking about these packs as they are so bloody cheap, but like the higher capacity (1.6ah) Makita V cells better so far.

 

[dimitrib90]

Dimitri,
So we save a total of $25 each? Minus cost of shipping to whomever does the footwork, sounds pretty good. Are these being fazed out by Bosch, or are they keeping the 36 volt line? I wonder if the price will keep going down. I wanted two chargers so that I could parallel the chargers to get charged in about an hour. I think John in CR did that successfully. But yeah, 5 batteries should be enough for my needs. Can anybody verify the 2ah rating, it seems I read somewhere that it was closer to 1.8?

I was quoted $50 per pack or $100 for two packs. This is already including shipping so yes minus the cost of shipping.

 

[dimitrib90]

Can anybody verify the 2ah rating, it seems I read somewhere that it was closer to 1.8?

The VT cell is rated for 1.1ah and the Bosch fatpacks are 2p so 2.2ah max in theory. I got a couple used VTs and before I fried my CBA I saw just shy of 1ah under heavy load (at like ~8C... was ~30w discharge if I remember right) from a single used cell so I think you'd see a practical 2ah a pack for sure. 1.8ah seems a little low unless there is some circuitry cutting out at a higher LVC or because the Bosch chargers only seem to charge to 40.5v instead of 42v, which is the most likely case. It's likely the 18650VT cell is only rated to 4.1v/cell like it's bigger 26650VT brother, but charging it to 4.2v/cell shouldn't kill it too much over time I would think.

Do let us know what you learn over time. I'm really thinking about these packs as they are so bloody cheap, but like the higher capacity (1.6ah) Makita V cells better so far.

I like the Makita cells too but not for the price. The Makita packs are well over a dollar a watt unless you buy from Doc.