Any use for a 36V DC motor?

[vpt]

So my kids cheap battery powered 4 wheeler has bit the dust and the kids have out grown it. I see some useful parts but am most curious about the motor which is still good from it. It is a 36V DC motor that doesn't list HP but something about amps or something on the tag. The motor is about 6" across and 8-10" long. It had plenty of power to move me along on the 4 wheeler and do a good 10+mph. It has a chain sprocket drive right now as well.

[SteveP]

Amps x Volts = Watts
746 Watts = 1 HP

Those are *input* numbers--the output from the motor will be less. There should be a speed controller for the motor which presumably still works. If you can find a source of 36 volts (3 PC power supplies in series?) it could be useful. Big, though, compared with RC motors. How many wires going into it?

Got photos? What's the nameplate number for watts or amps?

--Steve

[vpt]

I will run out and check for accurate numbers off the plate here in a few minutes. There are two wires going to the motor. There is a twist throttle control and a controller box under the seat. These both work great yet, the battery is shot, tires, bearings, and stuff. I don't think it is exactly air cooled but it does have around 6 3/8" air holes in the end cap with a screen filter. Maybe just breather holes for the brushes?

[vpt]

I exaggerated a bit. The motor is around 4x7"ish and the holes are around 1/2"

[PStechPaul]

It would be just about perfect for a battery powered bicycle. Or maybe a trolling motor for a small boat or canoe. A DC motor that size is probably 1/2 to 1 HP. That would be about 20-30 amps at 36 volts. You can get 12V 12A-h SLA batteries for about $25-$35 each. A set of those might give you a half-hour of run time and maybe an hour if you aren't pushing it hard.

[edit] You beat me to the post - 500 watts is about 2/3 HP. The input is 18.5A at 36 volts or 667 watts, which is 75% efficiency. Not bad, but it means there will be 167 watts of heat at rated output. It can probably be "pushed" to 2-3x power for short bursts. The MY1020 is a fairly common DC motor, but the same model seems to have multiple ratings:
http://www.monsterscooterparts.com/36vo10mowsps.html (1000W)
http://www.monsterscooterparts.com/36vo500wamow.html (500W)

[vpt]

It would be just about perfect for a battery powered bicycle. Or maybe a trolling motor for a small boat or canoe. A DC motor that size is probably 1/2 to 1 HP. That would be about 20-30 amps at 36 volts. You can get 12V 12A-h SLA batteries for about $25-$35 each. A set of those might give you a half-hour of run time and maybe an hour if you aren't pushing it hard.

[edit] You beat me to the post - 500 watts is about 2/3 HP. The input is 18.5A at 36 volts or 667 watts, which is 75% efficiency. Not bad, but it means there will be 167 watts of heat at rated output. It can probably be "pushed" to 2-3x power for short bursts. The MY1020 is a fairly common DC motor, but the same model seems to have multiple ratings:
http://www.monsterscooterparts.com/36vo10mowsps.html (1000W)
http://www.monsterscooterparts.com/36vo500wamow.html (500W)

It always amazes me how cheap some motors are to buy. Thanks for all the info! I wish it were a 12v motor though. What are the advantages to a higher volt DC motor?

[PStechPaul]

The main advantage is lower current and thus smaller wire and less resistive losses. Higher voltage controllers tend to be smaller and cheaper for the same power, up to a point. Voltages are generally considered "safe" up to about 48 VDC. With multiple smaller batteries in series, they can be located more conveniently and are easier to handle than large automotive types.

[darryl]

Along with lower resistive losses, and part of that, is that the brushes won't heat as much with the higher voltages. There is a point in the construction of the motor where voltages between commutator sections would be high enough to cause arcing and brush problems- generally there are more comm segments in higher voltage motors and less segments in lower voltage motors. I'm kind of thinking that 36 to 48 volts is about optimum for a brushed dc traction motor of significant power output. Brushless is of course a whole 'nuther story. Using 12 volts to power a motor that has to deliver the better part of a horse or more on a more or less continuous basis- well I'd say it's not really good engineering practice. The typical permanent magnet lower voltage dc motor is a pretty rugged beast overall, though.

[ironmonger]

It always amazes me how cheap some motors are to buy. Thanks for all the info! I wish it were a 12v motor though. What are the advantages to a higher volt DC motor?

In the electronic controller world, current costs money. Todays IGBT's handle high voltages easily. High current takes heavier wiring, heavy switches and fuses. The electronics for high current is more expensive as well. Thats why electric cars use high voltage battery packs.

Look at inverter welders, they typically do the power conditioning and control at 800 to 900 volts DC then generate high frequency and feed it to small, efficient high frequency transformers and then rectify the AC to DC weld voltage. They rectify all the incoming single or three phase into dc before processing in the electronics.

As far as single phase vs three phase input for the VFD, pretty much watts is watts. All the input current, single phase or three phase, is rectified and converted to DC and from this the 3 phase variable frequency and all the features are electronically derived. So if you can supply enough single phase current the end result is the same. The advantage of three phase driving motors does not translate directly to VFD's.

paul

[darryl]

Electronic device technology is getting right up there- what did we see a few days ago- a device capable of handling 30 amps without a heat sink- the video showed three of them in parallel being tested at up to 120 amps, at which level they were blowing air over them, but still without a heatsink.

But regardless, if your application is calling for that kind of current you would want to look at getting the power required by raising the supply voltage as well. And even though battery technology has progressed, and they are capable of outputting high current levels, it's still not good to work them that hard in general. Even in RC models, where much power is required the supply voltage is often made to be 30 volts or higher- up to 80 volts I've seen, which is a bloody lot of cells wired in series.

[J Tiers]

Nobody would use an IGBT for that usage..... too much loss.

There are plenty of mosfets with milliohm "on" resistance and 100 or 200 volt ratings.... devices rated for so much current the package leads are the limit..... 70 plus amps for a TO-220 as a headline rating. And cheap.

36V is still a good voltage.... but it will push 50V on charge.

[fixerdave]

It's not uncommon these days to control a motor with PWM (pulse width modulation) AND use much higher voltages than the motor rating. Have you tried hooking 12vdv up to said motor? It's possible it will make plenty of power at that voltage; it's possible 36vdc straight into it will be way too much without the PWM.

David...

[PStechPaul]

At 12V the motor will run at about 1/3 nominal speed and power, or about 160 watts at 18.3 amps, but the resistive losses will still be about the same as they are at full rated 36V. You might safely apply up to 48V (or even 60) to this motor to get higher speed (and power), but higher current will soon burn brushes and windings, and any internal cooling fans will be rather less effective. At high frequency, a PWM drive will be equivalent to the same constant level of DC, but at lower frequencies it will have a "cogging" effect, or "torque ripple", which in some cases may be advantageous (like a hammer drill). This type of permanent magnet brushed DC motor also has a regeneration property which can be used to recharge the battery, or for dynamic braking.

[vpt]

So its a good motor to stick on a windmill?

Can any 12v batteries be ran in series to make up 36 volts? Maybe in the end I will see if I can pick up some cheaper batteries and fix the 4 wheeler a bit. The controller is set up to run reverse/fwd, slow, and fast mode. Slow mode the 4 wheeler runs at about half the speed of the fast setting. They label it as "training mode".


This is a video I made of my kid playing on the 4 wheeler a few years ago. This was in "training mode".

http://www.youtube.com/watch?v=6lW6BcpfJ0E

[J Tiers]

"Any"? Technically, yes.

For best results, they should be the same capacity, since then they will all discharge together. If any is of lower capacity, the danger exists of it becoming reversed in polarity on a deep discharge, and the current capacity will be that of the smallest.