Car Battery for post-season bot
 

i want to get a lot more speed and power on 4 CIMs and i want to use a car battery at 12v. Is this possible, and if not, can i use two EX batteries that we use at comps? I want 4 victors in it and dont know if the high AMP will cause the fuses to break. I also want to use one spike for a superstructure and run the compressor as well. Im planing on making a robot that can carry a heavy load, go fast, and also will have some cool superstructure that uses the actuators (i dont know what superstructure i will do, but know i want to use pneumatics). So, can anyone help and answer my questions about if its possible to use a car battery?

Thanks,
Eric

Re: Car Battery for post-season bot
 

A car battery will not give you more speed or power. Only more runtime. Also, I would not recommend it as they are not sealed gel cel type. Just get a giant battery from BB battery or your local battery store. It shouldn't cost too much. While you can use a car battery, I wouldn't due to spillage and safety concerns.

Re: Car Battery for post-season bot
 

Eric,
Four motors or six doesn't matter if you don't get the reduction right to put the motors in a correct spot on their respective curves. A car battery will certainly let you run longer but you will be stressing the other components if you plan to run for a greater length of time then two or three minutes. Many teams are running very close to trip temperature on the breakers in a two minute match. You might have to redesign the electrical system if you plan on a longer run time. Whereas the kit battery is capable of several hundred amps in short bursts, a car battery is capable of 1000's under the same condition. The choice of that battery will change a lot of design criteria.

Re: Car Battery for post-season bot
 

well, i want longer battery life, that is good enough for me. My design was changed so i dont need extra power to the motors or go faster. I just need to have 4 motors running, a compressor, and one solenoid. So, i dont think ill over heat it with the EX battery we use now in comps. The motors wont be running when i use the solenoid to pressurize the actuator. I just want it to run a like 20-30 minutes minimum. I can add a lot of fans and heat sinks for over heating issues, and i dont understand why car batteries are not sealed. Well, how do i solve the amp problem?

Re: Car Battery for post-season bot
 

I would be concerned about using the CIMs for a long amount of time. They do not have cooling airflow like the drill motors do. If I remember correctly the CIMs were designed for short use, something like raising the front trailer wheel on a camper.

Of course you can modify the motors for non-competition use, but I dont know if they even have the internal blower blades like the drill motors do?

You might want to look into something like an electric scooter motor, or electric wheelchair motors - something that is designed to be run continuously.

Re: Car Battery for post-season bot
 

Eric,
Many car batteries are of the sealed type in a sense. Our are a gelled electrolyte not a liquid, which allows them to be used in any configuration including standing up. Car batteries cannot be used that way. We pulled a dead chalupa motor apart just last night. There are no fans internal, they are designed for short term light load uses. Fans will help a little but not much if you are running heavy loads for long periods of time.

Re: Car Battery for post-season bot
 

well, than is there a vey inexpensive motor/engine that can use a car battery? I can mount the car battery vertically, so there is not a problem there. The only problem is motors from what im gathering from this information. Oh, and the heavy load is a person, just to let people know. Im building a transportation device for a fundraiser for cancer, its call Relay For Life, and i want to build it so people can ride it around a track. I dont want gas engine. So, anyone know a cheap motor/engine that can work for my project? My max spending limit is like 100 bucks. But even that is very high. I wanted to use CIMs as myt team already has them.

Re: Car Battery for post-season bot
 

You won't need 4 CIM motors for that purpose. If you are low on funds and want to use KOP parts, try using the FP motors with the stock transmissions. Those things are designed to cart people around.

Re: Car Battery for post-season bot
 

I see this project getting very dangerous very quickly. Do not mount the car battery in any orientation other than horizontal.

Re: Car Battery for post-season bot
 

i can mount it in any direction. thats what i ment to say. i thought car batteries are mounted vertically, the battery orientation, not the mount. doesnt mater, i can mount the battery in 360x360x360 degrees. Any direction. I just need to modify the design to do that.

Re: Car Battery for post-season bot
 

If you need more capacity, there are 'car batteries' that are sealed gell cells. Look at 'Optima' brand for one.

Re: Car Battery for post-season bot
 

yeah. thanks. now the engine/motor problem is my issue. thanks again for your guys's help.

Re: Car Battery for post-season bot
 

I agree with Tom that two stock FP motors with transmissions are the best bet for you. You might need to follow up with a little different transmission (final gearing) to make up for the fact that you are driving bigger wheels than what the transmission is intended for. The kit battery might getyou around the track but a larger version of the same battery might be a better bet. You can buy new ones but there are various surplus shops around that might have used or surplus devices for sale. You will need to check around in your area. Since this is for charity, a local battery shop or car parts outlet might be willing to lend you or donate a battery of more capacity.

Re: Car Battery for post-season bot
 

Im thinking of the 8 inche wheels, only because our team uses a 6wd on our comp robots and use 6's for the wheels. We have a lot of 8 inch wheels. If those are not good, what will be. And, is there a way i can integrate 2 fp motors together. We have like 4 of them. Or will 2 be enough? A car battery will do the work, im almost positive from my research, so that will be the bigger battery.

Re: Car Battery for post-season bot
 

I have seen people use old generators from car engines for small electric go-carts. Not alternators, it has to be a generator. VW bugs had generators up till around 72 or 73 (not sure the year they swithed to alternators).

There are two things that make these work well:

1. the are designed for a 12V application
2. they have a separate field winding that you can use to vary the speed. The stronger the field, the slower the speed (with more torque)

also they have fan belt pulleys already on the shaft. I would take a wild guess that you can get maybe 5HP out of one of these!

just to give you an idea, this is what they look like: the ground is through the metal housing, one connection is the armature, the other is the field

http://cgi.ebay.com/ebaymotors/VW-TY... 4644044QQrdZ1

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.

Re: Car Battery for post-season bot
 

hmm that seems wierd im gonna go do some more research and that and see what i can find out.

Re: Car Battery for post-season bot
 

I found this page:
http://www.tpub.com/neets/book5/18b.htm

I know it is mainly about AC motors, but do a search for "alternator" and this should come up:
"The construction of the synchronous motors is essentially the same as the construction of the salient-pole alternator."

So it's not the same as a squirrel-cage motor, but it still requires AC and would be a pain to power. :D

Re: Car Battery for post-season bot
 

I just did some research, and i found Bosch motors for generators. I saw that they had vey fast motors with low torque, and high torque motors with low speeds. They had high torque window motors. What if i take a normal windo motor from the kit and gear that way up to make the rpm way faster. Would that burn out the electronics and/or motor? I could not find the generators they make on their website, but i do know they make them for the old volvos. I want to get a pair of the generators for at max 120. The lowest price i found for one alone is 130. So, can i use the window motors?, and are there cheaper generators?

Re: Car Battery for post-season bot
 

that website that Elderon found is awesome!

They used DC generators on cars, which worked great, but they had a few drawbacks. They were somewhat expensive to build, and the commutator and brushes would wear out sooner or later and would have to be replaced.

An alternator is an AC generator that used diodes to rectify the AC to DC. They also use an induction armature (or rotor) which makes them less expensive to manufacture.

This is why you can use a generator as a motor, but not an alternator. The diodes in the alternator only let current out, not back in, and if you took the diodes out then you would need to power it with AC to make it run like a motor.

Its interesting to note that the EV1 electric car made by GM did have an AC motor, with electronics that converted the DC from the batteries to AC. I think the main reasons for doing that were the motor was lighter, less expensive, and easier to control.

But if you want a simple motor that runs on DC from a battery, then an old car generator or something like a wheel chair motor, riding scooter motor - those are the kinds of things to look for.

regarding the car window motors. I dont know how much HP you can get out of those. There are limits, any given motor will only take so much current before the windings melt, and you can only spin them so fast before they self-destruct. Also, if they use permanant magnets (like the window motors, CIMs, drill motors...) you can only drive the armature magnetic field to the point where the metal core material saturates. After that you cant practically get a stronger magnetic field, and any additional current you supply is turned to (copper melting) heat.

So as with everything else in engineering, the laws of physics impose limits to what you can do. You can only get so much HP from a motor before one of those laws maxes out and you either melt it down, or it rips apart.

Re: Car Battery for post-season bot
 

Why do other CIMs, not the FIRST ones, last a long time, yet the FIRST ones cant run that long, as stated earlier. It says on FIRSTWiki that they un a long time. Why cant i get a bigger battery, but use like 4 CIMs from the kit?

Re: Car Battery for post-season bot
 

Eric,
The smaller Chalupas are designed for powerful but intermittant duty on a trailer jack. The larger ones are designed for more prolonged duty on a scooter but have different power vs. RPM specs. The larger ones might be just perfect for your application.

Re: Car Battery for post-season bot
 

so this years large ones can work? I can order 2 more, as they are not as expensive as other ones. The only problem is the frying electronics. It happened once before, and how do i prevent it this time?

Re: Car Battery for post-season bot
 

Eric,
I assume you are speaking of the speed controllers. This is normal when the system draws too much current from the controller. If you make a mechanical design that runs the motors below 40 amps you shoul be fine. The thing that kills speed controllers is running the motors at near stall where the current is over 100 amps.

Re: Car Battery for post-season bot
 

so if i can rig the fuses in series with a 30 amp fuse instead of a 40 amp, would that cause the speed controllers to not fry. Is there any other option i have besides switching the fuses?

Re: Car Battery for post-season bot
 

you can use a 30 amp breaker instead of a 40 but it may trip more often, the bigger CIMs certainly last a while we ran our robot for a few hours and we use the bigguns for our drive and had no problems with them overheating

Re: Car Battery for post-season bot
 

The 40 amp breakers should be good to protect the Victors. The situations in which you are likely to burn out Victors are things like

having a drive train that can stall the motor. If the motor cannot turn it will draw its max current through the victors until the breaker opens. You keep doing this and the Victor will eventually fail.

having a drive train that is geared up so it takes several seconds for the motor to reach its top speed

having a driver who throws the motor from full forward to full reverse and back.

Keep in mind the breakers are intended to protect you wiring and Victors from shorts. If you repeatedly overload the breakers (so they click click click all the time) you are over stressing your entire motor drive circuit (including the Victors).

Re: Car Battery for post-season bot
 

So, if i take 4 large CIMs (i buy two more, as well as 2 per side equaling 4), and wire them up for the drive, and since i will be running it on a flat rubber track, they wont stall. If i design it right, than i wont bun anything out right? But what if i want to take it full speed? (on the straight-aways :) ) I know you mentioned you have taken full speed and has taken time to do that, but are you refering to stall in the since that there is a force causing the motor to stop with power going in?

Ken, "Keep in mind the breakers are intended to protect you wiring and Victors from shorts. If you repeatedly overload the breakers (so they click click click all the time) you are over stressing your entire motor drive circuit (including the Victors)."

It protects the victor on the other side of the victor from the motor. Does it protect the victor when the motor is causing the victor to smoke/spark from over heating? No, need explaing if it does, just a yes or no answer because i can figure out both senerios if it does or doesnt protect the victor on the motor side.

Re: Car Battery for post-season bot
 

Eric,
Stall means that the motors are so loaded that they cannont turn, even when full power is applied. If you design the mechanical system such that the motors are turning very slowly when full power is applied you are drawing more than either the motors or the speed controllers are designed to supply. JVN or Paul Copioli or Andy Baker can give a better description or a better design criteria for your use. If you look at the power curves for the motors, you will notice a point at which the motors are the most efficient, are at stall or at no load. On these curves are the tested currents for each of these conditionsl. A designer chooses wisely the point on the curve he wishes to operate by selecting the final RPM delivered to the wheels and the correct gear or pully reduction that will put the motor into a specific point on the curve. (not at or near stall and hopefully closeer to the most efficient point on the curves or printed specification.
Although the breakers are thought to protect the motors and/or the Victors, they are in fact chosen to protect the wiring from damage. If you were to consult the wire tables from the NEC (National Electrical Code) you would find that a #12 in free air with intermittant duty can be protected by a 40 amp fuse or circuit breaker. In conduit or in continuous duty that current must be reduced to prevent damage to the wiring. It is easy to see that breakers protect wiring, since many of the more powerful motors supplied in the kit are capable of well over 40 amps when heavily loaded or near stall. When the Victor fails, the circuit breaker trips to protect the short from drawing so much current in that branch that the wiring starts a fire.

Re: Car Battery for post-season bot
 

Thanks Al, I think i may want to have direct drive though to the wheels. But if not, can someone help a little bit more with the curve, i think i understand what you are talking about, as my next paragraph explains. Is it the one on the spec sheets on FIRST, or a different curve. I know the pm i want. I want around 850, which with 8 inch wheels is 20 miles an hour or so, if outside factors did not limit it. I think the large CIM is at 1600 rpm at 40 amps. Well thats what the spec sheet shows. It also has 210 torque of oz-in.

Now, looking at the graph, http://www2.usfirst.org/2006comp/Spe..._FR801-005.pdf
I want about 200 oz-in of torque to give just about 1700 rpm, which is perfect for gearing 2:1 to get my desired speed. The only problem is it is 35 amps, which i dont know how to achieve this. I think this set up wont stall the motors, as well as allow a fast ride with a lot of torque.

Re: Car Battery for post-season bot
 

WHOA! I would NOT want my grandma flying around the track at 20 mph on a handcrafted powered chair! If you are still using this for the same purpose (Relay For Life) I highly suggest you don't let your machine ever come anywhere close to that speed! Seeing as the normal walking pace is ~2.5 mph, you should probably try to keep your machines output topped out at about 4 or 5 mph (in case their partner wants to run.)

If you directly couple a Fisher Price gearbox to a 12" Pnueamatic wheel, (One of these assemblies on each corner), your nominal speed will be about 3.25 mph.

Re: Car Battery for post-season bot
 

Eric,
I agree with Tom. If I read your post correctly, you want the reduction to give 850 RPM to the wheels. That sounds pretty high. I am out of my element on mechanical design here, but, backing into the calculation, a 6" wheel needs to turn about 170 RPM for 3 MPH. For a larger wheel that number needs to be reduced. A 15" wheel would only need 67 RPM. Is that what you get, Tom? Again, on the published curve, I think you want to design around paramater on the left side of max power. I would feel more comfortable for a mechanical guy to chime in here but I would think the 150 to 200 oz.in. part of the curve should be OK. Keeping the RPM up and gearing down multiplies the torgue and lowers the current.

Re: Car Battery for post-season bot
 

I dont want to take it 20, just know that if i get into a race, i can whoop som a$$. :) Well, i want it to go faster than what a normal person runs, which is about, im guessing because the walking speed is 3-5 mph, that running is around 10-13 mph. Do you think max speed is ok at 15 mph then? Im going to control the speed with a potentiometer next to the steering wheel. I doubt ill ever bring it that high when there is people on the track, but i find 15 mph ok. The pot will be not be contected to the motor, but programmed to slow the motor.

Tom, thanks for the reality check. Online on google... ahhahah google... well it says that the average human walking speed is between 3-5 mph, which makes sense due to the fact that in PE 10 min to do a mile, well im middle school for me it was, but that is so that they know everyone ran a part of it. 1h/5mph= 1/5 (60) *min in an hour* = 12. Aka the 12 min mile which senior citizen walk. So the average human walk is about 3-5 mph. Also, our robot, i am almost certain at top speed is more than 5 miles per hour. We use four CIMs to drive, as well as after the gear box, we gear it up a little.

So, is 15mph still too high?

Re: Car Battery for post-season bot
 

Eric,
10 ft./sec is about 7 MPH. Depending on your design, a device that gets up to 10MPH may get unstable on a rubberized track. You don't want to go fast and throw your ride on the ground. Remeber that CG is going to be inherently high in a ride with a person sitting up.

Re: Car Battery for post-season bot
 

so 10 should be good? I think ill stick to 10 then (as i wont take to full speed most of the time), as i dont want to mess up a track, especially when the new rubber tracks that Birmingham and my school, Granada, have. I got a lot of designing to do... thanks for all the help. I going with a four large CIM drive system, 2 on each the back wheels, and geared to 10 mph. That as well as a larger 12v battery with 4 spare 883's. I think im all set. Thanks again, all you guys, for the advice and information.

Re: Car Battery for post-season bot
 

you owe us jpegs when its up and running :^)

Re: Car Battery for post-season bot
 

Its a long way away. But if it gets approved, which im going to fight to get it approved, ill post pics and at least a couple of videos. The reason why it may not get approved is because of the previous thing where they smoked the victors. But im not going to let that happen. Now i have to do a write up for the proposal. There is way more than just being a go-kart, but i wont reveal what that is :) . But it will ROCK YOUR SOCKS OFF!!! ahaha. Well, back to chicken soup and designing, being sick really is a bummer.

Re: Car Battery for post-season bot
 

Go-Kart was declined :(
But im still using all of this info for another project that is just as cool, but underwraps until unveiling... :)