Re: Car Battery for post-season bot
 

Eric,
The smaller wheels should be better. I was envisioning you modifying a regular wheel chair rather than building up from scratch. The FP motor and transmission is used on ride toys for 60 pound kids as a single unit. Two of these should be good for up to 120 and may work up to 150 pounds total weight. The larger Chalupa motor is used on a scooter type device. I repaired one once for a friend and rode it for several minutes. I am well over 200 pounds (no I'm not going to get scientific and give you an exact weight.) and it carried me at a relatively quick pace. It did have a safety device that required you to get the scooter up to speed before the motor could be engaged. It contained a centrifical switch that closed when the motor was spinning at more than the minimum speed. It used a simple toothed belt transmission to couple to the rear wheel.

Re: Car Battery for post-season bot
 

I cant find any lartger CIMs that will work with 12V. I found some at 24V, but i dont know if i can use Victor 883's, we have a lot and want to use since we cant use them in comp anymore. I dont want to blow the speed controllers out. The robot, kart, im looking at weighing about 90 pounds max. and the person weighing about 200 pounds max. So it needs to be able to push 300 lb. Of course, im using two motors. but i need to know if i wont blow up the victors.

Ken, does that attach to the wheel to recharge the battery while it runs? Im very new at electronics outside of FIRST and guitar electronics. That will charge the 12V battery, but if i get a 24V, do they make them?

Re: Car Battery for post-season bot
 

Eric,
I believe ken was indicating that a generator can be used as a motor and it already has a pulley attached and a few nice mounting brackets. The larger CIM motors in the kit this year are the ones I was talking about. (we call the chalupa) If speed is not important, I would think you could use two of those motors with a larger 12 volt battery and you should be OK for once around the track.

Re: Car Battery for post-season bot
 

well, im a little skeptic of using a lot of FIRST electronics because two years ago, i found this out today, that we tried building a go-kart and the electronics fried because of amp over heating the motors. Will the same thing happen with a lager battery. Thats why i want to get a car battery and bigger CIMs as the amps will be used and not fry the electronics. Thank god im not building without designing on this or i would have had an expensive problem. ahahah. thanks again for all your help.

Re: Car Battery for post-season bot
 

What Al said - you can use a generator from a car for a motor.

I dont see any reason why you could not run it at 24 V - it will have 4 times the power. The limiting factor on motors is the current level that melts the armature, and the max speed (that rips the windings and commutator off the shaft).

There are specs for the Victors on the IFI web site. I think they are rated for 12V only, but check for yourself, they might have other ones intended for other applications?

Re: Car Battery for post-season bot
 

so, if i used two, both a 12v, than i should be good right. Then i dont have to worry about getting new speed controllers. But will it push without over heating at 12v? If so, can heat sinks and fans cool it down enough? Also, mounting, is it easy to mount like the CIMs in the gear box? Also, can i buy them new at a cheap price?

Re: Car Battery for post-season bot
 

Eric,
If you correctly size the motor to wheel reduction the current in the motors will be low. The reason we have been suggesting a larger battery is the distance/time that it will take to get around the track. The best designs in our competition will get 3-4 matches from a single battery but there is rarely continuous current draw. With a larger battery, you should be able to run for a much longer and continuous period without worrying about the battery becoming discharged.
If the goal is to get someone around the track then a simple design should work fine. If the goal is to beat other teams around the track then that will require a little more design time and some better engineering.

Re: Car Battery for post-season bot
 

The Victor 884 is rated to 15V stock, however I read somwhere that the limiting factor is the fan, and if you replace the fan with a 24V fan you can run it at 24V.

Re: Car Battery for post-season bot
 

I wouldn't recommend over powering the victors, they are expensive stuff and I don't believe you can change it around. As you will see IFI has higher voltage PWMs running with only 24 volt (even 12 volt) fans, does that change what they are rated for? No.

Don't worry there are other solutions though, did you guys know that IFI makes stuff for a business and not just for FIRST?

Yes it's true! And they have Higher Voltage PWM's!!!
Victor 883 (6-30 rated 24 Volt recommended)
Victor 885 (6-30 rated 24 Volt recommended)
Victor 36HV (12-42 rated 36 Volt recommended)
Victor 48HV (12-60 rated 48 Volt recommended)

All the fans for the victors are available in 12 or 24 volt models, if your voltage is greater than 15 volts, I recommend bumping it up to a 24 volt model.

Re: Car Battery for post-season bot
 

The fan is not integral to the Victor but that is not the limiting factor. The FETs are different to handle the voltage spikes produced by a 24 volt motor. I believe the part number is 885 for the 24 volt version.

Re: Car Battery for post-season bot
 

Just thought i would chime in here about victors. The 883s are rated for 24 volts and i used them in that orientation for my battle bot this past summer.s As for motors if you are going to spend some money anyway i would seriously consider electric scooter motors. There is a great website http://electricscooterparts.com/ that has motors, batteries, and other control electronics if you are trying to move away from the IFI system.

Re: Car Battery for post-season bot
 

Ah, sorry about that. I guess I confused the 883s and the 884s! :o

Re: Car Battery for post-season bot
 

I still want to use a past robot and operator controller in the electronics. But i think i still can with non-FIRST drive systems. Im still trying to find a good price on a bigger 12v battery. I cant find any other car generators that are not alternators besides that one that Ken mentioned.

20 min later: found battery. 12v 50ah 89$ Or i can get cheaper ones that have like 33ah for like 53$. So, ill get some 24v fans, as we have the 883's on hand. Generators are the main thing i cant find.

Re: Car Battery for post-season bot
 

Could you explain the difference between the generator and alternator for a car, i was fairly sure that an alternator could also be used as a motor until i read that post, im now a little confused?

for motors it may be a good idea to salvage some of your teams old Drill motors we are using them for a cart designed to haul as much as half a ton

Re: Car Battery for post-season bot
 

From what I remember, the alternater generates AC which is then rectified into DC, whereas the generator directly generates DC. Turning the generator into a motor is a simple matter of applying DC to the "output", but an alternator has to be driven like a squirrel-cage AC motor, including powering the field coils.