Battery choice...

[xletts]

Hi all, if you see my other post you will see I toasted my last set of batteries and my stock BJ ESC. I have put in an order from this site for a hydra 120. Can anyone recommend a lipo battery and prop combo to match the hydra and the BJ motor? I already have a 14.8v 2200MAH 25C from my other boat, would this be OK?

Thanks for helping out the dumbest of newbies! :)

[Fluid]

Nope. And you are not dumb! By now you should have a better idea from the responses on your other thread - that is simply not enough battery. Something on the order of 3300mAh and 25C would work, that's 82 amps. I use these specs in my UL-1 and they work well; more capacity would not be a bad idea however. You could get two more sets of your current packs and wire them in parallel, but that can become a wiring nightmare if you are not careful.

[xletts]

Thanks Fluid! You guys (and this forum) are awesome... that has given me something to work with so I can order the right battery and hopefully avoid the next tragedy!

Thanks again.

[Ub Hauled]

IMO get at least 25C 4500mAh packs, they will output the power you need, longer runtimes and will not heat up as much.
Fluid is one of the pro's around that help out a lot... with that being said, he also knows how to setup a boat that will use less power with success... you are not at that level yet.
Be safe... when buying your next lipos, don't buy the minimum mAh you'll need.

[xletts]

Great advice...thanks again everybody. Hopefully this will help other newbies with the same dilemma. Sheesh, this RC hobbie is technical! Makes my job look like kids stuff! :) Great fun though!

[xletts]

So just to confirm, I am thinking of this pack for use with hydra 120 and blackjack (stock) motor:

Poly RC PQ-3000XQ-4S Li-Poly Battery
14.8V 3000mAh (4 cells), 30C/60C
Rating: 30C (90.0A) continuous, 60C (180.0A) burst
Dimension: 149mm x 44mm x 27mm
Weight: 340 grams
Termination: Wire & PolyQuest/Hyperion tap

Should be OK?

[Ub Hauled]

it should work but if you can afford larger packs, do so.

[xletts]

And I would need to run two of them in parrellel right?

[Ub Hauled]

If you paralleling them then the 4s 3000mAh should be sufficient, not very flexible though.
Do you have any other boats?

[xletts]

So if I have this right - you can use a total battery capacity that exceeds the max amps of the ESC provided your motor doesn't draw more than the ESC's rated max amps? So for example I could happily use a 4S 30C 5000mAH (assuming I could afford one) with the Hydra 120 even though 30 x 5000 / 1000 = 150 amps. Does that sound right?

Which means, now all I need to do is work out the maximum draw of the stock BJ motor with the prop I am using?

[xletts]

If you paralleling them then the 4s 3000mAh should be sufficient, not very flexible though.
Do you have any other boats?

Yeah I have an "ebay" boat (mean machine knock off) but I'm trying to work on one at a time

[Ub Hauled]

So if I went by your suggestion of a 25C 4500mAh pack, according to the calcs from kookie_guy that would be 25 * 4500 /1000 = 112.5 amps. Will the hydra handle that OK when it is only rated for 120 amps?

This math does not mean this current will run thru the ESC at all times...
usually "outta the hole" is where you see the biggest spikes on current (biggest effort).
The 112.5amps you see is the constant amps drawing that the particular pack will take (or should). if you drawing less then 112 amps then you will be fine. If it's over the 112amps it'll fall under the "burst currents" that the label specifies as well.
Your B Jack will not get close to that with the original prop.

[xletts]

Thanks again! I wish there was someway I could by you guys a beer! [_]}

[xletts]

Thanks again! I wish there was someway I could buy you guys a beer! [_]}

[Ub Hauled]

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