London Expo, antweights??

[Remote-Controlled Dave]

I ran a standard 9v square NiMH rechargable (think it was duracel) in Apocalypse Then Redux at my first reading robot club. It worked fine and it's even possible to get them into weight limit.

[peterwaller]

Simon I think you will find that the PP3 batteries are only about 150mA hour. The duracell ones are better but you would probably be better with a normal NiMh or Lithium Polymer. Especially as you are running at 9v which means you are increasing the current consumption.

[Simon Windisch]

OK Peter,

So the problem is to have a robot that can run 100% of the time: on LiPos that would mean having four LiPos and three battery chargers? There must be another solution.

In the meantime, I am building a box which will be table mounted, and have a joystick and a flip switch on it to control a robot without the peril of giving a stranger your precious remote control. The box will be connected to a "real" skysport hidden under the table.

[BeligerAnt]

Peter's right, the NiMH PP3s are low capacity and also low current. Alkaline PP3s would give plenty of capacity and current, but then there are the cost and environmental considerations.

NiMH calls can be recharged faster than Li-ion, some cells can be recharged at 4C rate giving a 15 minute charge time. For this to be successful, you really do need a good charger since overcharging at that rate can be catastrophic (the last thing you want at a public event!).
AFAIK there are no Li-ion cells that can be properly charged in less than 1 hour, the chemistry simply does not allow it. A real full charge takes about 4 hours, regardless of what any charger might say!

A pack of 4 AAAs or even AAs would provide plenty of capacity. As long as all robots in the fight carry the same excess weight, it really doesn't matter what the weight is. If you really want to stick to class rules, go for superants which can easily accomodate a pack of AAAs.

[Simon Windisch]

OK, so 4 AAAs will give me 6V, for a cost of approx ?2, and one 9V battery also costs ?2, so why are AAAs more environmentally friendly than a 9V battery, or have I misunderstood?

Simon

[Simon Windisch]

Just to clarify, because I think I'm being misunderstood, I'm not talking about batteries for combat, I'm talking about a replacement of the peerless LiPo for demonstration events, like London Expo, Ickenham, or last year's Aylesbury.

The problem with these exhibition shows, where we want to show off the robots fighting, and so inspire others, is that we spend over half of the time charging, and I'm trying to find a solution. I hope that's clearer now.

Simon

P.S. there's a 6V 300 mAh 2/3AAA battery back for ?6.57 plus postage at https://www.ultimatemodelsonline.co.uk/ ... rodid=3337

[olivers]

You can get semi-cheap hi-cap Lithiums if you look around:

http://www.indoorflyer.co.uk/index.asp? ... T&catid=23

For displays you want to aim for 150g but if you stray over due to batteries it's not much of an issue in my book.

[Marco Roberts]

Just a slight warning

Recently I needed some liths so I ordered em off indoor flyer. They arrived late, about two weeks. When I checked the receipt it was printed off three days before teh delivery date so the guy obveously sent it late.
I also needed two but he only sent one saying that was teh last one and he would refund me the mony.
Checked my next bank statement and he still hadnt. Sent him and email and he said he was going to get on to it.
I am now waiting to go back home and check my next bank statement.

as I said, just a lil warning.

[petec]

Simon, I think for what you are trying to achieve, AAAs or AAs are the ideal solution - environmental arguments are pretty much null given the number you are likely to get through compared to the number manufactured and the effect of disposing of any batteries.

From past experience though there is one consideration. I've done this myself in the past - I used 900mAh AA packs and the longevity was good, but the motors really struggled carrying the extra weight around. They got serious hot and on Pants I bust some gears in Combat. Worth thinking carefully about it.

I've used Indoor Flyer quite a bit and never had any problems, but he can sometimes take his time - like me I think he holds a 'real' job.

[BeligerAnt]

...so why are AAAs more environmentally friendly than a 9V battery, or have I misunderstood?

Yes, you misunderstood
The point was that rechargable batteries are less environmentally damaging than disposable alkaline ones, but as Pete says, at the volumes you are likely to use it's not a big issue.
You still can't beat alkaline for energy density (mAh per gram).