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[packy46]

Hello
Need help !!
Have 2x Graupner 720 BB torque mtrs, I know I need brushed ESC's maybe 20/30 amp.(Sandy helped me on that,Thanks Sandy )Noticed some ESC's  will list LiPo, NiCd, NiMH, I have 2x 12v - 7.5 Ah. SLA batteries,then go on to say, for use with
2 to 4 cell's.
Thanks,
Tim

[Ian Robins]

Hi

The stalled current is 13.5 amp. so I would use a action or mtroniks speed control of about 20amps to be safe.
The esc you mention seems to be for lipos.

The viper 20 from Mtronks is rated for 12v input                http://www.mtroniks.net/details1.asp/ProductID/182/sid/2/Viper-marine20.htm
The action Condor 20 is also rated at 12v input                  http://www.action-electronics.co.uk/speed.php

There may be others but these two are recomended the most at my club
You pays your money and takes your choise.

Hope this helps

ro88o0

[packy46]

Thanks ro88o0:
On my way to check out the links....
P.S. Thanks for the quick reply it does help...
Thanks
Tim

[FullLeatherJacket]

Nah - you don't need 20A speed controllers for those pussycats.
 
I've tested one for Stavros on a 12v x 7AH SLA and can confirm that the Condor P80 doesn't like 8-pole motors - but the standard P93 is just  the job. Fuse the things at 10A and you'll be fine.
 
Can't speak about The Other Sort; I'm acquainted with the Viper 15 but I've never handled a 20A one - never needed to.

(Thanks for the plug, Robbo........there's a Czech in the post.)

FLJ

[Stavros]

Could not agree more with FLJ you just don't need 20amp ESC  Go with what Mr Action says they are pussycats



Stavros FLJ will pop up to see Ian tomorrow evening

[packy46]

Thanks All:
Didn't think my math was that bad,I knew the stall speed when I was buying them,some one told me to go as "BIG" as
I wanted,can't hurt approach.
Thanks for the good information....
Tim

[FullLeatherJacket]

My crude test gave a no-load current of 0.6A and a "very heavy load" current of 2.5A. My very heavy load consists of a rag held between finger and thumb and applied to the rotating shaft at full chat. When either a) the rag starts to smoke; b) my eyes start to water; or c) both, then it's a VHL. It's not very scientific but it's good enough. You'd have a job reproducing that sort of load with a prop unless you were running it in treacle on a cold day. Nuts to the theorists - it works in practice.

As for the stall current, the MOSFETs are rated for a sudden inrush of a-lot-more-amps-than-that for a second - just long enough for a nice cheapo blade fuse to meet its maker.

FLJ

[wombat]

Stall current on the 720BB is 13.5A at 12V - so you won't draw more current than that on 12V.

You shouldn't need to go above 15A to 20A for the ESC. Fuse the motor at 10A and you should be laughing

Wom

[stallspeed]

Lipo ESCS should have a voltage cutout to prevent over discharge of a Lipo battery.In my mind that would just be a problem on a boat.

I don't actually think Sandy made a suggestion for a motor if you review http://www.modelboatmayhem.co.uk/forum/index.php?topic=13549.0

S&Y

[packy46]

Thanks for helping all...
One day the Water Gods will repay you......
Thanks
Tim

[andygh]

I've tested one for Stavros on a 12v x 7AH SLA and can confirm that the Condor P80 doesn't like 8-pole motors - but the standard P93 is just  the job. Fuse the things at 10A and you'll be fine.

P80S? Or am I missing summat?

[FullLeatherJacket]

P80 Standard version = Not OK (Unless you like blowing up MOSFETs)

P80S Special version = OK = £38 (20A continuous current; Autoset neutral; linear or soft-start; 2v - 12v)

P93 = OK = £32 (10A continuous current; Fixed neutral; 6v - 24v; Adjustable 25%/50%/100% peak output)

Do the maths, dude! I do try  to be honest..........honest!

FLJ

[andygh]

Fair do's, I just bought the P80S for mine as I thought the ESC rating was meant to be higher than the stall current of the motor to be ultra safe.

I don't suppose my 720BB will ever completely stall (unless it gets set in concrete) and I'm sure a 10A fuse would save the day anyhow but you've got me all worried that I've bought the wrong ESC now 

[Proteus]

.

I don't suppose my 720BB will ever completely stall (unless it gets set in concrete) and I'm sure a 10A fuse would save the day anyhow but you've got me all worried that I've bought the wrong ESC now 

or a plastic bag around the prop

Proteus

[andygh]

It'd have to be a strong one but yes indeed 

[red181]

It happened to me Graupner 700 bb turbo, 12v, direct drive at the time, went over a slightly submerged plastic bag (small sandwich type) boat came to an immediate standstill as it wrapped around the prop like a piece of rope,(It is a fast scale electric) 60amp ripmax seasprint esc cut out, even though the "stated" stall current of the motor was lower. Luckliy this particular esc had a cut out to protect it.

Dont get a esc that is marginally over your motor capacity, firstly the motor manufacturers dont know your running set up, if the drive line is slightly off, or you are not water cooling etc etc you could be running a setup that is already amp hungry. SDecondly, if you move up to bigger packs, another boat, different motor  etc you have a esc that will cope with the changes.

Electronise are one of the best on the market, UK supplied, great back up service, and the big thing, they are repairable