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The other problem alistair is that at 36v they will be pulling nearly 40amps at stall. Thats alot of current and will need a Big speedo to deal with it.
They will also get very hot. Realistically to run golds you will need to use 3amp sanyo cells. These are quite heavy and would weigh 2.85kg.
Another problem with 36vs is a supernova (or replacement) will not charge those batteries.
So perhaps sticking with 24v is a better idea.
Regards
Ian
40 amps at stall is not that much compared to many of the alternative motors available or even a 12v gold which stalls at more than that. If geared correctly I doubt you would have any trouble with a 25 or 30 amp continous rated speedo.
Ian is right in most bots drive trains they will hot, very hot is pushed to hard.
As for needing sanyo C cells to run them this is rubbish, Thuggernought runs 2Ah sub C sanyos on a pair of golds at 24V and we have had no trouble with them and will easily run 2 fights without charging and they are only ever warm after a bout never hot.
The charger issue is a problem but can be over come with 2 18v packs or even 3 12v packs.
The golds in thuggernought are not worked to hard and we are thinking about 30/36v the main problems we have are - new batteries (want matching packs and need a different shape), More weight (We are a bit under but n ot enough) and the fact the electronise speedos are rated to only 24v and I personaly would not like to run them over 30v.
I agree Sam, Ive tested the golds in a bot and on the bench and you definately can run the 24v at 36v. I used the H5 speedcontroller @ 36v on mine. Ive also driven BlacknBlues spinning bar on a 12v gold @ 24v and whilst the motor was very hot the subC NIMH cells were only warm. The only disadvantage of the golds is weight and cost
The other problem alistair is that at 36v they will be pulling nearly 40amps at stall. Thats alot of current and will need a Big speedo to deal with it.
40 amps is piddly. Weve run our 12v winch motors (2.25kg each) in our featherweight Torque 2 Me and they will draw a good 100+amps when we sit on it riding around. We power this all from a single 7AMP DOSS SLA which is 2.6kg. We use an IBC controller and it handles this fine.
In reguard to the gold motors, drill some 8mm vent holes in the case, add some suppression caps if your dont already have them, gear them down more to get the same speed as you would want for on 24v and use 3 x 12v NiMH 3000mAh packs. I dont know much about the H5 controllers, but they sound like they will do fine.
Pushing the limit is all apart of Robot Combat :)
LOL - I dont think youll be getting 200 amps out of a 7Ah SLA
I think you may find that in that circumstance your battery is providing you with more than a little bit of current limiting !
Ed
http://www.teamstorm.comhttp://www.teamstorm.com
We originally though that too Ed, but weve managed to pull 250 amps continous for 1min out of our DOSS 7AMP SLAs on our featherweight spinner Annihilation before the power slowed down.
Weve tested it on two amp meters and both times weve had the 400amp initial start up current then the a drop to 200-250amps continous till the battery drops to 10.6v and our weapon relay shuts off. Funny enough, we thought the batteries would die quite quickly with this type of abuse, but after 4 events with several battles at each, the batteries are still going good.
If your willing to pay $15 Aussie and the P&P, Id gladly send you one for you to do some testing with :)
Surely at 200+ amps for 1 min continuous the little faston terminals would start to melt?
We used to use 4Ah SLAs at 120ish Amps (peak) and after a couple of events the bottom of the batteries had started to sag from the heat they were generating. After a 5 min fight they were too hot to handle.
Im with Ed, I cant believe you are pulling 200+ Amps continuous from such a small battery.
250 amps for 1 min is a discharge rate of 35C on a 7Ah Battery.
To compare like with like, a 35C discharge rate from a fairly standard robot battery like a Hawker Genesis would mean 1 x 16Ah Hawker being capable of delivering 560amps for say 1 min.
Even the 16Ah Hawker Genesis is only rated for 535 Amps for 5 seconds before the voltage drops to below about 7 Volts, and the voltage heads south from there to the point the battery becomes un-usable.
I did have a whole section of the post where taking into account efficiencies of SLA batteries vs rated capacity and Ah ratings I worked out that if you *really* developed 250amps for 60 seconds, you actually exceeded the rated capacity of the battery, and ended up with the terminal voltage of the battery hitting 0v.... and thats before you look at the size of the terminals ! (so I just decided to delete all the maths as it would have just bored people!)
Bottom line is guys, Im sorry, but theres no way a 7Ah battery can supply 250 amps (or 200 for that matter!) (3Kw of power!!!!) for 60 seconds.....
Ed
http://www.teamstorm.comhttp://www.teamstorm.com
Well, I want some of those 7Ah batteries because they perform far far better than anything else on the market. Im with Daniel and Ed on this one, its just not possible for a 7Ah SLA to provide 250A for one minute. A really good SLA like a 16Ah Odyssey has a 4C Ah factor of about 40%, this further reduces with higher drains. If we were really generous with your 35C drain and assumed 25% Ah efficiency then your 7Ah battery would only last 25 seconds at 250A. The power dissipated in your battery assuming a typical internal impedance of 28m Ohms would be 1.75kW i.e. meltdown. As Ed suggested, the maths is getting boring.
Paul
Ill try to get some more testing done on them to get some more accurate data for you. Weve tested the same motor and weapon setup with the amp meter on a 15amp SLA and we get the same amperage readings. The terminals are slightly discoloured but they havent melted yet.
Im not sure what voltage it drops down to, but it stays high enough for the relay to keep the solinoid going. Im really tempted on sending one over to you Paul for free just to hopefully prove they these batteries are quite good.