Running a wiper motor from 12v battery

[transatlantic]

I have been experimenting with running a wiper motor from a 12v 7ah lead acid battery as I want to create a robot. I am using the faster of the two speeds. But even after only 5 minutes of the motor running constantly, the motor is too hot to touch? It seems to be running at a continuous 6A which is about 9A on startup.

Is this normal for this type of motor? I guess these motors aren't designed to run continuous like this?

 

[MikeMl]

Most electronic apparatus is designed to run too-hot-to-touch. The wiper motor is normally bolted to a chunk of metal which is effectively an infinite heatsink. When you unbolt it from a car, and run it, without its heatsink, it is going to get much hotter...

 

[tcmtech]

Those motors are designed to run continuous duty in a very hot environment while supplied from a power source that can run up to around 15 volts so if it's overheating that fast off of a 12 volt battery either you have it overloaded or the motor is going bad or you have something wired wrong.

 

[Pommie]

Wiper motors normally only move little wipers and, I would guess, draw 1-2 amps continuous. If you're using them to drive a vehicle then you are overloading them.

Mike.
Edit, if you leave them running with no load do they still get hot?

 

[Nigel Goodwin]

It's quite common to use wiper motors in 'small' robots, and it's normal to run them from 24V to increases their speed and power (bear in mind you should be using PWM speed control) - I can't say I've ever touched a wiper motor to see how hot it is, but I wouldn't be surprised if they run pretty hot even at 12V.

One of the famous competitors in Robot Wars (can't remember his name, but he was the first to use a flipper to self-right his robot) created a smaller fighting robot design in the magazine Ultimate Real Robots using wiper motors - and mentioned that he's used large numbers of them professionally for moving models in museums and displays etc. and never had one fail, all run from 24V.

 

[GromTag]

Heavy dense magnets and large contact brushes, tend to weigh quite a bit as well. They can get quite hot depending on the model and initial torque, and that's all ways guesswork unless information from the manufacturer is available by name and model number.

 

[GromTag]

Would it perhaps be a self reversing model? vague memory of some time ago, repair manuals warned of not rewiring a self reversing motor in a 360 continuous operation, excessive heat would be generated. How to do this, I do not remember.

 

[Mickster]

Wiper motors are usually installed beneath a cowling, which has slots for ventilation.
When the wiper motor operation is required the vehicle is usually moving and air, along with water, is flowing over the motor body and cooling it.
However, there are other situations where wiper operation is required - dusty environments such as would be found in middle-eastern countries.
You would likely find that the wiper motor would be "too hot to touch" in the ambient temperature of those countries, before it was even switched on.
How hot is "too hot to touch"?
That depends upon the person, but usually around 65°C for metal objects.
Google search results show .pdf datasheets for a few wiper motors that I found and the max working temperatures were in the range of 85°C to 105°C, depending upon the manufacturer.
If you want to find out whether your motor is being run outside it's upper temperature limit, you need to use a better method than simply checking with your hand.
A regular thermometer, non-contact IR thermometer, or a multi-meter thermocouple will be much more accurate.

 

[transatlantic]

Thank you for the replies. I did try and find the specs for the motor itself but couldn't find anything other than car manufacturer info. I also tried searching for the OEM number with no luck. But here is the product I bought if it helps?

**broken link removed**

I also did some tests using a laser thermometer and accurate timing, here are the results. It was at about the 15 min mark I would say it was too hot to touch, so my initial quote of 5 mins was /slightly/ off

Room temp - 18c

5 mins - 38c
10 mins - 50c
15 mins - 62c
20 mins - 74c

Also - this is with no load. Just two wires from the motor to a 12v 7ah lead acid battery. The two wires chosen are the ones to use the faster of the two speeds. There are five wires in total for the motor, and depending on the configuration, there is 2 speeds, and a few other modes for non continuous rotation.

 

[tcmtech]

Wiper motors are usually installed beneath a cowling, which has slots for ventilation.

Ford and many others put them in the engine compartment where they are subjected to as much heat as everything else in there. No liquid or like cooling there!

 

[tcmtech]

Thank you for the replies. I did try and find the specs for the motor itself but couldn't find anything other than car manufacturer info. I also tried searching for the OEM number with no luck. But here is the product I bought if it helps?

**broken link removed**

I also did some tests using a laser thermometer and accurate timing, here are the results. It was at about the 15 min mark I would say it was too hot to touch, so my initial quote of 5 mins was /slightly/ off

Room temp - 18c

5 mins - 38c
10 mins - 50c
15 mins - 62c
20 mins - 74c

Also - this is with no load. Just two wires from the motor to a 12v 7ah lead acid battery. The two wires chosen are the ones to use the faster of the two speeds. There are five wires in total for the motor, and depending on the configuration, there is 2 speeds, and a few other modes for non continuous rotation.

Are you sure you have the correct wires given most wiper motors are frame grounded not wiring harness grounded.

That and it's an ebay motor which very well means it could be low grade junk (price would imply likely cheaply made) that was never designed to run continuously as would a decent quality motor.

 

[JonSea]

Take a look at this YouTube Video on using wiper motors that just came out. He should be able to give you some hands-on results, rather than so many opinions.

 

[transatlantic]

Are you sure you have the correct wires given most wiper motors are frame grounded not wiring harness grounded.

That and it's an ebay motor which very well means it could be low grade junk (price would imply likely cheaply made) that was never designed to run continuously as would a decent quality motor.

Well - I am able to run both speeds. Surely if I had wired it wrong it wouldn't be spinning?

 

[shortbus=]

Would it perhaps be a self reversing model? vague memory of some time ago, repair manuals warned of not rewiring a self reversing motor in a 360 continuous operation, excessive heat would be generated. How to do this, I do not remember.

I keep seeing the "self reversing" thing come up when talking about wiper motors. Can you give a car make or model that uses them? Never seen one that did that, other than the old vacuum wiper motors. Every electric wiper motor I've ever worked with used cranks and bell cranks to get the back an forth motion.

 

[tcmtech]

Well - I am able to run both speeds. Surely if I had wired it wrong it wouldn't be spinning?

More than likely you have it wired right, but give the amount of basic wiring/setup oversight related issues we see on these type of forums one has to ask the question anyway.

Unfortunately the majority of my service tech life is spent looking for and seeing the small but critical 'obvious details ' others miss and correcting them. In the electrical/electronics area miswired/open/shorted circuit issues is by far the most common thing I deal with.

My guess is that you simply have a cheap motor that was not built for high load continuous duty applications given my brother used to use old wiper motors for his fireworks chemical mixing rigs and those could run for hours at a time when he was doing multiple batches of mixes back to back.

#1 failure was from mechanical failure due to the plastic gears and shaft bushings wearing out due to higher than designed for side loading. Not motors burning up.

 

[tcmtech]

I keep seeing the "self reversing" thing come up when talking about wiper motors. Can you give a car make or model that uses them? Never seen one that did that, other than the old vacuum wiper motors. Every electric wiper motor I've ever worked with used cranks and bell cranks to get the back an forth motion.

I think it refers to the more modern wiper systems that 'park' the wiper blades down lower on the windshield than where they normally are at when in use.

When wiping the windshield the motor rotates in one direction but when shut off power is applied to them in some way that reverses the motor a bit thus making the crank mechanism change its sweep angle range in order to pull the wipers down below the field of view. That's what that complicated rotary switch assy on the back of the worm gear compartment is for. It set the range of travel limit for the motor when it goes backward to park the wiper blades.

Good chance your own vehicles have that self reversing function to park the wiper blades when you shut them off and you never thought about how it works.

 

[GromTag]

Can not find that book for anything. I recall it was more about a rear wiper assembly that would reach a point then self stop the rotate, then other direction using a 3 pin ring "sensor" on the motor that would link a signal to the motors relays for this function driven by completing the circuit to the control boxes relay to the motors 3 ring circuit then to the control boxes N-Ch BJT transistor collector.

Once the pin left the ring track within the motor the link from the relays negative connection to the N channel BJT Collector was broken ( went open circuit) and at the same point the ring would contact the other relay into operation changing the polarity to the motor from the relays. Those types have to be insulated from chassis GND as why they have 2 wires for the motor. And would be close to producing a short circuit by design if not for the control box having a delay IC of some sort, lots of ND, Nippon Denso chips seen to apply this function.

However without the control box in the effort, the motor could be run directly.

 

[shortbus=]

Good chance your own vehicles have that self reversing function to park the wiper blades when you shut them off and you never thought about how it works.

I know how that works. I saw the post as saying, as many want to say, that a motor runs one direction to wipe away from the rest point and the reverses rotation to wipe back to the rest point. That is something I've never seen, other than the old "trico" vacuum wiper motors.

 

[tcmtech]

I know how that works. I saw the post as saying, as many want to say, that a motor runs one direction to wipe away from the rest point and the reverses rotation to wipe back to the rest point. That is something I've never seen, other than the old "trico" vacuum wiper motors.

I see. I assumed you were talking about normal wiper motors that reverse to park the wipers down low.

As GromTag points out there are some special application motors that use full motor reversal to do their back and forth sweeps. Some heavy equipment used, and likely still does but from what I recall of them they were expensive and at the time used a sort of snap action DPDT mechanical switch to do the reversing.

Or at least the one I played with years ago worked that way. I don't recall what it came from other than a big payloader of some sort and the direction reversing switch inside had worn out. ~$200 in 1990's money for a new wiper motor unit because a few cents worth of parts for a switch had broke.

 

[transatlantic]

More than likely you have it wired right, but give the amount of basic wiring/setup oversight related issues we see on these type of forums one has to ask the question anyway.

Unfortunately the majority of my service tech life is spent looking for and seeing the small but critical 'obvious details ' others miss and correcting them. In the electrical/electronics area miswired/open/shorted circuit issues is by far the most common thing I deal with.

My guess is that you simply have a cheap motor that was not built for high load continuous duty applications given my brother used to use old wiper motors for his fireworks chemical mixing rigs and those could run for hours at a time when he was doing multiple batches of mixes back to back.

#1 failure was from mechanical failure due to the plastic gears and shaft bushings wearing out due to higher than designed for side loading. Not motors burning up.

Well I stand corrected. Looks like I did have it wired wrong..... maybe? By using the chasis ground and the white and yellow, I am able to get two speeds. The slower is about 1.5a and the faster is 2.5a, where as the way I wired it before, it was 4a for the slower and 6.5a for the faster. However the old wiring does have a faster RPM. Its still hot after 20 mins @50c though, but it'll do i think.

mmhmm

I just assumed that as I was getting two speeds with the original wiring I must hae gotten it right. Nope!