Battery help.

[Chris230291]

Weld/wire the cells together myself and apply my own heat shrink. No visible markings to indicate what i'm using.

It's starting to look like the majority of the cost is going to be on batteries. Is this the case for most builders?

Whats the cheapest way of getting 36V that will last long enough? I have 4 motors here that each draw 60+ Amps when stalled. They weigh 1.1KG (ish) each so i need to watch my weight because the chassis wont be light either.

[terry]

Lipos are cheap what's wrong with using them, I assume its for a fw at only 60amp stall per motor, its what nearly everyone else uses. 36v is a high voltage is that the voltage of the motors?

[Chris230291]

Well i must admit my math skills suck. I was under the impression that the regular model kind won't cut it?
The motors are 24v but i'd like to run them at 36v if i can afford to in terms of cost and weight.

Would you mind linking me to something you think is suitable so i can get an idea of what will work?

Thanks,
Chris.

[Ellis]

The motors scooter motors, by any chance?

[Chris230291]

Hello Ellis. If i google "scooter motor" the image results look similar, so i guess so. Why, does that matter?

Chris.

[Ellis]

They probably have a sticker/plate on them giving some stats, are you able to see a wattage rating? It'll look something like 150w, or 300w, etc. If not, find the closest google image you can, it should be possible to gauge within a bit what size motors you have.

I ask because chances are very high that just two in the machine will be plenty of power. Even at 24v. Check out this build to get an idea what two, at nominal voltage, will get you: http://www.fightingrobots.co.uk/thre...am-gas-diary-s

[Chris230291]

Ok well they LOOK like the 100W ones but there are no stickers on mine...



That robot looks fairly powerful to be fair. If i don't use all 4 for the drive, i'll use 2 for drive and 2 on the weapon.

It looks like he's using Ni-Mh's?

Chris.

[daveimi]

If it's a first robot stick with nihm packs and a normal charger. It most cases it works out really cheap and they will still give easy discharge rates. You need to know what you're doing with lipo.

edit: I'm not sure how genned up you are but get read up on charge / discharge rates in mAh, generally the higher quality the battery the quicker it will discharge. 12-24v is usually enough for most people, if you need more you could possibly look to a physically bigger motor within the voltage range.

The main reason for people moving to lipo technology is to cope with the rising popularity of brushless motors that require a crazy amount of performance from the battery. As far as I've seen, if you're staying with a conventional brushed motor setup then nihm packs will be fine for you.

[Chris230291]

Yeah i understand Li-pos can be dangerous. That's why i can't understand Li-ion being disallowed. They seem just as safe as Ni-Mh :S

I was worried about discharge rates. I don't want the batteries to bottleneck my motors.

[maddox10]

Yeah i understand Li-pos can be dangerous.

We are building COMBAT ROBOTS, not Barbiemobiles.

That's why i can't understand Li-ion being disallowed. They seem just as safe as Ni-Mh :S

Primary cell batteries ain't in the rules either, just because they are unsuited for our purposes. But I don't believe, if you turn up with a suitable Li-Ion pack, you would be "disallowed" to compete.

I was worried about discharge rates. I don't want the batteries to bottleneck my motors.

If you want discharge rates, you could look at the Hawker Cyclon SLA cells. Those start @2V 2.5Ah , and those little ones have a discharge rate of 500A+ that's 200C