Motor Amp Load/draw

[aaugman]

When a dual motor set up is in a bind what is the amperage load or draw that it creates ?

I know those micro switches from radio shack work (for the most part) but what kind of loads are those motors actually creating ?

[Rockcrawler]

I would think somewhere around 80 amps although I thought I remember someone saying around 60.

[j.e.n.i.k.82]

I´m interested in it too.. Because of battery.. I have 3S Zippy 1300mAh and 2200mAh, they have 20C. And now I´m really not sure, if they can handle two Integy 45s on Tekin FXR and Hitec 7955tg. Could anybody measure it for sure?

[aaugman]

Originally Posted by Rockcrawler

I would think somewhere around 80 amps although I thought I remember someone saying around 60.

That sounds crazy high, an electric 220v oven draws less than 50amps, all the lights in my house are on 3 15 amps circuits, U think that 11.v lipo and 2 motors would draw more than a whole house of lights ??


are you referring to milliamps ?

[Rockcrawler]

The Motor Construction Thread aka What Motor should I Get?

[62 bugzilla]

Apples and oranges. 11.1 volts at 60amps is no where near 10 amps at 220volts. And ya sounds about right 2 motors pulling 60 to 80 amps peak power in a bind maybe more (peak). I've had some boats pull over 125 amps average over a packs worth of time. Some bigger stuff will do more but ussually people go to more voltage to go faster and intern it brings the amp load down.

[j.e.n.i.k.82]

Try it in other words.. Can I use my batteries? 1300mAh and 2200mAh.. I thought I will use 1300mAh in competitions (for about 15-20 minutes - it was my plan) and the 2200mAhs for bashing (I will be in nature, so I need longer runtime). I thought it wrong???

[Rockcrawler]

The 2200 mah pack should be fine. The 1300 pack I am not so sure about.

[ErichF]

Originally Posted by aaugman

That sounds crazy high, an electric 220v oven draws less than 50amps, all the lights in my house are on 3 15 amps circuits, U think that 11.v lipo and 2 motors would draw more than a whole house of lights ?? are you referring to milliamps ?

The best way to illustrate consumption among different voltage and amperage systems is to use Watts. Watts is the electrical term for work done, as is horsepower in mechanical terms. You figure Watts by multiplying Voltage X Amperage.

In your house current of 220V, 50 Amps is only needed because the voltage is so high. In this case, your oven is consuming 11,000 watts (actually a little less than that, since I doubt the oven is maxing out the amp rating of your house circuit.) To put that in terms of 12 volts, that would mean an amperage requirement of 916 Amps.

To the OP, if you can find the Wattage of your motor, you can calculate the estimated amperage required at full power. If it's an 800W (probably a lot bigger than what we use in crawlers) motor, then at 12V, you'd need 66 amps. Then, to be safe, add 50% to that for stall amperage. That would be roughly 100A. A 2100 3S at 100A would equate to 47C, way over the rating of the pack. In this example, a 5000mAh pack would be in order. This would also be the case if you had a pair of 400W motors and both of them stalled (rare).

Hope that makes it clear as mud

[Terranaut]

Can anyone find info like this for the motors we typicaly run in crawlers? Note Watts and Stall Current in the chart.

http://http://www.mabuchi-motor.co.j..._ID=rs_540rhsh

Also, LiPo discharge ratings are not reliable. If it says 20C that usually means the max sustained discharge without blowing it up. Often they are capable of a 'burst' rate which may be 25C or 30C, burst meaning not more than a few seconds. So, if at it's burst rating it can match the motor's stalled current, you should be safe, assuming you are not stalling it too often. However, a bigger pack would obviously be better to provide some margin.

Cheers.

[binaryterror]

Originally Posted by j.e.n.i.k.82

Try it in other words.. Can I use my batteries? 1300mAh and 2200mAh.. I thought I will use 1300mAh in competitions (for about 15-20 minutes - it was my plan) and the 2200mAhs for bashing (I will be in nature, so I need longer runtime). I thought it wrong???

I run a 25C 1345mah 3S lipo on an FX-R without any issues.

You will HAVE to run an external BEC though. On a 3S lipo your BEC amperage becomes basically useless.

[Rocksolo]

I am having issues too getting my dual motor /FXR/Outrage 1345ma rig running too.
I have radio shack switches, and I am on my third set ....so far the switches last about a battery pack not quite. I dont know what I am doing wrong other than the switches cant handle the load?

[JohnRobHolmes]

The radio shack switches are quite small, they will burn up fast when you turn them on/off while on the throttle.

Something like a 55t will pull about 35 amps in a stall on 6 cell nimh, maybe more depending on how stout the cells are. As you double the voltage the stall amperage increases fourfold.


I only use high discharge 1300 packs for rare competition use in my berg. Generally I use 2200 packs instead.


Driving style has a lot to do with amp draw too, If you hammer down with some nice lipos the amp draws can spike up into the 60s for a decent handwound 35t.

[Rocksolo]

I feel like an idiot asking this but is there a diagram showing how to connect two motors to the esc without the dig switches.
I am utterly confused and sick to my stomach with myself and/or my rig:-( I do not compete. Therefore its not worth the time and stress right now. I will buy the first plug n play electro-dig thats proven. Till then I would like to connect the motors with a Y of some sort and forget the dig crap all together.
help!

[ErichF]

Originally Posted by Rocksolo

I am having issues too getting my dual motor /FXR/Outrage 1345ma rig running too.
I have radio shack switches, and I am on my third set ....so far the switches last about a battery pack not quite. I dont know what I am doing wrong other than the switches cant handle the load?

It will be easier on the switches if you wire them on the negative side of the load (Motor). The induced arcing is not as bad. I used to be a field tech on electric forklifts, and all the control switches are wired on the negative side of the load for this purpose.

Also, those typical Radio Shack micro switches are only used in 15A or less circuits. They are not intended to carry power loads. They are generally used to carry control voltage to solenoids and contactor coils.

[binaryterror]

Originally Posted by ErichF

It will be easier on the switches if you wire them on the negative side of the load (Motor). The induced arcing is not as bad. I used to be a field tech on electric forklifts, and all the control switches are wired on the negative side of the load for this purpose.

X2

Negative cut out has treated my switches very well.

Also do not DOG the switches...this put more heat into them and can cause failure.

Worse case buy the Manly ones from Holmes Hobbies rated at 3 times the Radio Shack ones. 15A for JRH, 5A for Radio Shack.

[Rocksolo]

Originally Posted by binaryterror

X2

Negative cut out has treated my switches very well.

Also do not DOG the switches...this put more heat into them and can cause failure.

Worse case buy the Manly ones from Holmes Hobbies rated at 3 times the Radio Shack ones. 15A for JRH, 5A for Radio Shack.

Originally Posted by ErichF

It will be easier on the switches if you wire them on the negative side of the load (Motor). The induced arcing is not as bad. I used to be a field tech on electric forklifts, and all the control switches are wired on the negative side of the load for this purpose.

Also, those typical Radio Shack micro switches are only used in 15A or less circuits. They are not intended to carry power loads. They are generally used to carry control voltage to solenoids and contactor coils.

thanks alot for your input guys, I appreciate it!
I am realizing that the electronics is way over my head. I am going to simplify things for now by eliminating the dig altogether. I crawl solo so I'm only entertaining myself, I dont compete so if I have to reverse I reverse.

[Espeefan]

You'd be amazed how much current a little DC brushed motor can pull. On start up and in a stalled condition. I wouldn't say 40 to 50 amps is out of the question, given the right set-up and situation. Multiply that by two for a dual motor set-up and you've got yourself some serious current draw.

How do I know? Some time back I was actually going to measure the start up current of a motor. It was just a regular brushed DC motor on a 6 cell pack. I wired my meter in series, which had a 20 amp fuse in it. With the first pull of the throttle the motor blipped for a fraction of a second, and then nothing. It easily blew the fuse on my meter. So a stalled motor will easily draw more then 20 amps. Granted, start up current draw is always more then running current draw, but if you crawler is stalled and bound up, you'll probably be letting off the throttle and then hitting it some more to try and get it out of the hole. That's start up current, and a bound up situation.

If you use your head, hopefully you can keep the current spikes in check. Most battery packs will not handle that much current draw continuously, until you pay the big bucks for them. Current surge for a couple seconds is much different then a continuous rating.

[aaugman]

I found this store http://www.robotmarketplace.com/store_td-rc.html I want to try their dual switch set up, Its made for fighting robots so they have to make something that would work.

What do you think ?

[JohnRobHolmes]

Pretty cool little unit, not bad for $50 since it can be made into an H bridge

http://www.robotmarketplace.com/prod...TD-RCE225.html