C Ratings for Batteries and other stats......

[PJ-27]

Looking at potentially get some new cells or battery packs, since the ni-cad cells from the drills aren't up to the job!

Just wondered what sort of ratings I should be looking out for, in terms of C, m-ah and other things....

Need 9v (or a close 1.2 multiple) ni-mh type. (Given chargers)

Thanks!

[typhoon_driver]

Re: C Ratings for Batteries and other stats......

what are you planning on running off the batteries?

[PJ-27]

Re: C Ratings for Batteries and other stats......

The drive wheels. Two 12v drill motors via two 15amp ESC's.

[woody]

Re: C Ratings for Batteries and other stats......

I recently posted this link ...you may not have seen it.

http://architeuthis-dux.org/torquecalc.asp

Try something like 6 wheel and 1-1 Gearing using a Harbour Freight as the US equiv of your drill motors.

[PJ-27]

Re: C Ratings for Batteries and other stats......

No I didn't, this looks great I'll give it a try. Little complex as we have about 10 wheels and we drive gears that are attached to them......

1:1 gear ratio? Does any one know what the gearing is on the drill gearbox?

There no mention of C rating, assumed that would be the most important thing that robot builders would need to know.

[psychostorm]

Re: C Ratings for Batteries and other stats......

That would depend on what C is. If it is energy storage that would be calculated from mAH. If it is cells that would be calculated from voltage / 1.5.

[PJ-27]

Re: C Ratings for Batteries and other stats......

C as in the discharge rate, the level of current that can be continually be drawn from the cell.

My understanding of how to calculate it was Ah / current = C

So a 3ah cell with a rating of 2C can supply a constant current of 6A without problems.

I thought current draw would be one of the most important things about a battery in a combat robot (that and whether it will last the bout.....)

[woody]

Re: C Ratings for Batteries and other stats......

The gearbox on the drill based motors is ignored and the output rpm is that of the chuck.

So just input your gear ratio and wheel dia.

You can alter the voltage constant... rpm/volt if you know the original drill output rpm.

The 12V Harbour Freight is currently set @ 41.66 * 12 = 500 rpm

[PJ-27]

Re: C Ratings for Batteries and other stats......

Ok cool, thats handy.

Just out of curiosity does anyone know the gearing ratio?

[woody]

Re: C Ratings for Batteries and other stats......

Take your pick ....http://www.alibaba.com/product-free/243 ... R_BOX.html

[PJ-27]

Re: C Ratings for Batteries and other stats......

Cheers, quite high then. Higher than I imagined.