Using gold motors

[knightrous]

Using gold motors

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

[mute]

Using gold motors

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.

[storm]

Using gold motors

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

[m2xt]

Using gold motors

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

[knightrous]

Using gold motors

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.

[Guest]

Using gold motors

How exactly are you measuring the amps the motor draws? If your winch motors do draw that much power your IBC should have blown long ago.
Ive been wanting to ask that for a while.

[m2xt]

Using gold motors

Please do send a battery, I can test batteries up to 200A drain and data log the current (+/- 3% accuracy), voltage and temperature from 1mS intervals upwards.

Paul

[knightrous]

Using gold motors

@Daniel: We used Nicks ampmeter at the Marayong Annihilator when we were going put one of NiMH packs in, but he wanted to check if the motors would draw too much from the NiMHs, Andrew just gave it half throttle and then grabbed the wheel and it shot up over the 100amp mark for about 1-2 sec until he couldnt grip the spinning wheel.

On Annihilation we use a 1000amp analog shunt ampmeter, we use to run it on a 300amp scale but on start up it would just go off the scale, so now we use the 1000amp scale.

I think the IBC takes a bit more because we have a fan mounting on ours and tend to give them a break every now and then when driving them. When Brett did the testing on the older version of the IBC with the crap fet insulator washers, it would take 120amps for 5 secs when the insulators melted before blowing the fets. I dont know how much it could take with the new insulator washers installed.

@Paul: Ill be in Melbourne for RoboWars 2 in just over a week, Ill pick a few more DOSS SLAs up. Will grab and extra for you.

[Guest]

Using gold motors

Sounds to me that you need to re-calibrate your amp meter. If you have previously saturated either of those meters then they will no longer give you accurate readings. You should always set the meter to measure a higher reading than what you expect then work your way down to avoid overloading the meter. The best way to test the meter (or measure any current in any circuit) is add a resister of known value in series and measure the voltage accross the resister. Use Ohms law to get a value of the current through the resister (I = V / R). Compare this value against the readings from your amp meter.
I also remember hearing that T2M can run for over 5 min with the 7Ah SLA but when I was running 2 x EV-warriors off a 7Ah SLA the robot was useless after less than a minute and I know for a fact that I was not drawing more than 80A total (I instaled circuit breakers to protect my speedos during testing).

[knightrous]

Using gold motors

@ Daniel: The 7amp you are using I believe are the Supercheap ones, which we have bought a few and they have been pretty crap, no where near as good as our DOSS SLAs.

The winches seem to draw a lot of amperage quickly when really loaded IE: Person sitting on it. But with the force required in pushing another featherweight and driving itself around, it draws bugger all and has been know to fight 2-3 battles in a row without getting charged(RoboWars 2003, didnt have time to charge).

Do you have HellBringer 3 intact still, as I wouldnt mind lending you a DOSS battery and seeing how long you go with it.

In regards to our amp meter, it could be inaccurate, but weve tested it with RS-550s and its been within 1-2 amps of there specs. About the resistor part, the shunt on the ampmeter is a piece of resistor plating if Im correct, and we just move the wire from one bolt to the another one further or closer depending on which scale we are using on the ampmeter.

Anyway Ill talk to you more about them at RoboWars 2, I think we should give the Gold Motors there thread back and possibly start a DOSS SLA thread

[ewan]

Using gold motors

Back on the thread...

I recently brought 3 12v gold motors and I wondered what the gear/timing pulleys specs are (looks more like a timing pulley but you never know...). Each of the motors came with a pre-keyed fixing (gear or timing pulley) which may come to be useful...

Regards, Ewan

[team_ireland]

Using gold motors

Ewan just to let you know that you will have to suppose the shaft of the 12v gold motor some way as they have no bearing built in as are available on the 24v versions.

As for gears etc. contact HPC and get a catelogue, I have one and their invaluable.

Regards
Ian

[ewan]

Using gold motors

Ewan just to let you know that you will have to suppose the shaft of the 12v gold motor some way as they have no bearing built in as are available on the 24v versions.

As for gears etc. contact HPC and get a catelogue, I have one and their invaluable.

Talk about stating the bloody obvious, that wasnt my question anyway

[blazerbotics]

Using gold motors

the HPC catalogue is a good referance but its cheaper to buy from RS or Technobots. See if you can get hold of a couple of old 24v Golds and use their front plates instead of the ones fitted on the 12v ones. Are you running the 12Vs at 24v? Alpha uses MOD1 steel gears, probably abit OTT but theyre the smallest i could get hold of, i could turn them down...but that requires time :P

[stu]

Using gold motors

If your talking about the Timing pulley already on the gold, id reccomend against using that size belt which goes with that pulley. They snap and slip and all sorts. Heat it up and pull it off. Just a suggestion, we learnt with Kitty, and so did the very first Cutlet..

Mr Stu