# Electric motor question **URL:** \ **Category:** General Discussion\ **Created:** [June 30, 2021, 8:57pm UTC](https://community.cartalk.com/t/electric-motor-question/177775 "2021-06-30T20:57:21Z")\ **Posts on this page:** 20\ **Page:** 4
**Author:** ![bing](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/bing/32/4619_2.png) [@bing](https://community.cartalk.com/u/bing)\ **Post date:** [July 2, 2021, 8:21pm UTC](https://community.cartalk.com/t/electric-motor-question/177775/61 "2021-07-02T20:21:11Z")
Just another thing to consider. > **[Morris fire: Lithium batteries a concern as blaze burns for 2nd day;...](https://abc7chicago.com/morris-paper-mill-lithium-battery-fire/10846262/)** > > A massive fire involving thousands of lithium batteries continues to burn in Morris, prompting officials to extend the evacuation order for another night. ---
**Author:** ![Marnet](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/marnet/32/41_2.png) [@Marnet](https://community.cartalk.com/u/Marnet)\ **Post date:** [July 2, 2021, 8:22pm UTC](https://community.cartalk.com/t/electric-motor-question/177775/62 "2021-07-02T20:22:50Z")
> [@VDCdriver](#): > > When my father asked what had been wrong with Robert, my answer was… > _He had too many parts!_ > > Apparently I understood the concept of _irony_ , even at a very young age. Priceless! 🤣 ---
**Author:** ![bing](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/bing/32/4619_2.png) [@bing](https://community.cartalk.com/u/bing)\ **Post date:** [July 2, 2021, 8:27pm UTC](https://community.cartalk.com/t/electric-motor-question/177775/63 "2021-07-02T20:27:47Z")
Wish I would haveknown that. When I overhauled my lawn mower transmission, I got all done and found a washer on the bench. Couldn’t tell if it was a regular washer or a thrust washer. But disassembly and reassembly goes faster the second time around with a comparison with the schematic to see what was not there. I should have changed the gears at the same time so third time was the charm. ---
**Author:** ![Marnet](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/marnet/32/41_2.png) [@Marnet](https://community.cartalk.com/u/Marnet)\ **Post date:** [July 2, 2021, 8:29pm UTC](https://community.cartalk.com/t/electric-motor-question/177775/64 "2021-07-02T20:29:29Z")
Am I correct that Lithium-Ion batteries are more prone to catching fire than lead-acid batteries? ---
**Author:** ![Renegade](https://avatars.discourse-cdn.com/v4/letter/r/b4bc9f/32.png) [@Renegade](https://community.cartalk.com/u/Renegade)\ **Post date:** [July 2, 2021, 8:38pm UTC](https://community.cartalk.com/t/electric-motor-question/177775/65 "2021-07-02T20:38:07Z")
My grand father used to say that if you did not have parts left over you did it wrong. ---
**Author:** ![circuitsmith](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/circuitsmith/32/40376_2.png) [@circuitsmith](https://community.cartalk.com/u/circuitsmith)\ **Post date:** [July 2, 2021, 9:10pm UTC](https://community.cartalk.com/t/electric-motor-question/177775/66 "2021-07-02T21:10:22Z")
> [@Marnet](#): > > Am I correct that Lithium-Ion batteries are more prone to catching fire than lead-acid batteries? A lead-acid battery cannot itself catch fire because its parts are not flammable. It can of course start a fire in other materials. Lead, acid and water are not flammable. OTOH the parts of a lithium battery are flammable, some very much so, such as the lithium itself. LiFePO (lithium iron phosphate) are the most fire resistant variety of lithium battery, but they don’t hold as much energy per unit weight as other types. > **[BU-205: Types of Lithium-ion](https://batteryuniversity.com/article/bu-205-types-of-lithium-ion)** > > Become familiar with the many different types of lithium-ion batteries: Lithium Cobalt Oxide, Lithium Manganese Oxide, Lithium Iron Phosphate and more. ---
**Author:** ![weekend-warrior](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/weekend-warrior/32/26122_2.png) [@weekend-warrior](https://community.cartalk.com/u/weekend-warrior)\ **Post date:** [July 2, 2021, 9:27pm UTC](https://community.cartalk.com/t/electric-motor-question/177775/67 "2021-07-02T21:27:37Z")
just in case someone does not know… Over-charging a vented **lead** **acid** **battery** can produce hydrogen sulfide (H2S). The gas is colorless, very poisonous, **flammable** and has the odor of rotten eggs. ---
**Author:** ![texases](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/texases/32/862_2.png) [@texases](https://community.cartalk.com/u/texases)\ **Post date:** [July 2, 2021, 9:34pm UTC](https://community.cartalk.com/t/electric-motor-question/177775/68 "2021-07-02T21:34:58Z")
It also produces hydrogen gas, which is explosive and odorless, that’s why you don’t hook up the jumper cable negative side to the battery, to avoid sparks near the battery. ---
**Author:** ![Mustangman](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/mustangman/32/44130_2.png) [@Mustangman](https://community.cartalk.com/u/Mustangman)\ **Post date:** [July 2, 2021, 9:42pm UTC](https://community.cartalk.com/t/electric-motor-question/177775/69 "2021-07-02T21:42:36Z")
> [@Marnet](#): > > replacing gas engines in cars with electric motors doesn’t necessarily mean less weight You can make a gasoline engine primarily out of aluminum but electric motors need magnetic metals (iron and steel) plus metal that conducts electricity well (copper is best, aluminum OK) so they will be HEAVY. Figure a 200 hp engine weighs twice what a 200 hp electric motor weighs. Electric cars don’t need much in the way of a transmission so that is a big savings, too. And then you get the batteries… 16 gallons of gas, the tank and pumps are maybe 120 lbs. The batteries in an EV are maybe 1500 lbs… that is WAY more than the savings from the electric motor vs engine. That is why the Tesla Model S weighs 4650 lbs where a comparable gas engine car would weigh about 4000 lbs. ---
**Author:** ![Marnet](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/marnet/32/41_2.png) [@Marnet](https://community.cartalk.com/u/Marnet)\ **Post date:** [July 2, 2021, 9:45pm UTC](https://community.cartalk.com/t/electric-motor-question/177775/70 "2021-07-02T21:45:43Z")
> [@Mustangman](#): > > That is why the Tesla Model S weighs 4650 lbs where a comparable gas engine car would weigh about 4000 lbs. Wow! Thank you for the explanation. ---
**Author:** ![Barkydog](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/barkydog/32/2470_2.png) [@Barkydog](https://community.cartalk.com/u/Barkydog)\ **Post date:** [July 2, 2021, 11:58pm UTC](https://community.cartalk.com/t/electric-motor-question/177775/71 "2021-07-02T23:58:33Z")
Imagine 200,000 lithium batteries catching on fire. > **[Firefighters Deploy New Techniques in Battle Against Morris Lithium Battery Fire](https://www.nbcchicago.com/news/local/firefighters-deploy-new-techniques-in-battle-against-morris-lithium-battery-fire/2544930/)** > > Firefighters say that a lithium battery fire, which began to burn on Tuesday, is still smoldering in Morris, but progress has been made and officials are looking to execute new strategies to put out the blaze. According to Morris Fire Chief Tracey... ---
**Author:** ![George\_San\_Jose1](https://avatars.discourse-cdn.com/v4/letter/g/e5b9ba/32.png) [@George\_San\_Jose1](https://community.cartalk.com/u/George_San_Jose1)\ **Post date:** [July 2, 2021, 11:58pm UTC](https://community.cartalk.com/t/electric-motor-question/177775/72 "2021-07-02T23:58:36Z")
The ones I used were NiCads I think. Haven’t tried the Li ion versions. Although it seems like a corded version for the same power output would always be heavier b/c no matter how light weight the battery, it still weighs more than no battery at all. ---
**Author:** ![Barkydog](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/barkydog/32/2470_2.png) [@Barkydog](https://community.cartalk.com/u/Barkydog)\ **Post date:** [July 3, 2021, 12:05am UTC](https://community.cartalk.com/t/electric-motor-question/177775/73 "2021-07-03T00:05:00Z")
Like other posters above, I gave up on rechargeable batteries after too many failures. Cords are not that heavy or obtrusive to me and I have a screwdriver that runs on AA batteries. Gas powered snowblowers, chainsaw and lawnmower. Just to bitch why do leaf blowers and motorized bicycles make more noise than a car. I usually don’t mind but trying to sleep the church nearby 3 am guys spent 2 hours with leaf blowers to clear the snow 😚 ---
**Author:** ![George\_San\_Jose1](https://avatars.discourse-cdn.com/v4/letter/g/e5b9ba/32.png) [@George\_San\_Jose1](https://community.cartalk.com/u/George_San_Jose1)\ **Post date:** [July 3, 2021, 12:07am UTC](https://community.cartalk.com/t/electric-motor-question/177775/74 "2021-07-03T00:07:35Z")
> [@shadowfax](#): > > electric cars use induction AC motors The Tesla model 3 apparently uses a permanent magnet design rather than induction. When I’ve heard the term “brushless DC” motor in the past that is the configuration I’ve always assumed they were referring to. Brushless DC gained its popularity for use in computer disc drive motors in the 1980’s as I recall. If you can get powerful enough magnets attached to the rotating part there’s no need for electricity to move from the stationary part of the motor to the rotating part. [Tesla motor designer explains Model 3's transition to permanent magnet motor | Electrek](https://electrek.co/2018/02/27/tesla-model-3-motor-designer-permanent-magnet-motor/#:~:text=Tesla%20made%20a%20significant%20change,the%20logic%20behind%20the%20move). ---
**Author:** ![B.L.E](https://avatars.discourse-cdn.com/v4/letter/b/848f3c/32.png) [@B.L.E](https://community.cartalk.com/u/B.L.E)\ **Post date:** [July 3, 2021, 1:05pm UTC](https://community.cartalk.com/t/electric-motor-question/177775/75 "2021-07-03T13:05:31Z")
> [@Mustangman](#): > > Figure a 200 hp engine weighs twice what a 200 hp electric motor weighs. A 200hp CONTINUOUS DUTY electric motor is usually heavier than a 200 hp gasoline engine. Figure around 200 pounds just for the copper wire. The “360 HP” motors in a Tesla are really approximately 50 to 75 Hp motors that can be overloaded to 360 hp for a short time. This makes engineering sense because because most 360 HP car engines spend at least 90 percent of the time making less than 50 HP. To get an idea of how underloaded most car engines are, turn your gas mileage into gallons per hour. My Yaris gets around 40 mpg at 60 mph cruise, that comes out to 1.5 gallons per hour. An airplane with an engine of similar HP rating will burn around 8 gallons per hour at full power and 5 gallons per hour at 70% full power cruise. I recently put a new stator winding in a 60 KW alternator. 60KW contiuous/75KW standby. The nameplate weight of the alternator was 600 pounds. The rotor all by itself weighed 230 pounds on our scale. ![](https://global.discourse-cdn.com/cartalk/original/3X/d/5/d5074b7dd1ab0ee3c496f89d81da4ebc66c037b8.jpeg) You’ll notice that this is a brushless alternator rotor. The armature on the back generates 3 phase that is rectified into DC to excite the rotating field windings by a small rectifier bridge that rotates with the rotor. Why can’t they make car alternators that way? The engine that drives this alternator is a 4.5 liter John Deere 4 cylinder diesel engine. I googled the engine model number and found out it weighs around 780 pounds, this a cast iron diesel engine, not an aluminum block gasoline engine. I’m not sure if the weight includes the accessories. Radiator, 12 volt alternator, air cleaner, etc. An aluminum block auto engine could easily be lighter than this alternator, particularly if it is geared down from 3600 to 1800 rpm that the alternator needs to generate 60 Hz AC. That brings us back to the motors on Teslas. These motors are connected to the axle with a gear train, double reduction, that allows the motor to spin around 10,000 rpm at highway speeds. The motor, gearbox+differential, inverter, transaxle unit actually weighs close to 600 pounds. ---
**Author:** ![Mustangman](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/mustangman/32/44130_2.png) [@Mustangman](https://community.cartalk.com/u/Mustangman)\ **Post date:** [July 3, 2021, 1:48pm UTC](https://community.cartalk.com/t/electric-motor-question/177775/76 "2021-07-03T13:48:26Z")
Yes agree with all that. The 200 hp continuous duty motors my company used to build were BIG and HEAVY but 200 hp short burst motors are much lighter. In an ICE auto. The heaviest lump is the powertrain assume a FWD where everything is included. In an EV the heaviest lump is the battery. The powertrain 200 hp ICE vs 200 hp EV might be a wash depending on the design choices, but the battery vs fuel tank weight is the issue. ---
**Author:** ![keith](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/keith/32/5518_2.png) [@keith](https://community.cartalk.com/u/keith)\ **Post date:** [July 3, 2021, 7:55pm UTC](https://community.cartalk.com/t/electric-motor-question/177775/77 "2021-07-03T19:55:40Z")
> [@B.L.E](#): > > You’ll notice that this is a brushless alternator rotor. If that is a brushless alternator rotor, what is the commutator for? ---
**Author:** ![B.L.E](https://avatars.discourse-cdn.com/v4/letter/b/848f3c/32.png) [@B.L.E](https://community.cartalk.com/u/B.L.E)\ **Post date:** [July 3, 2021, 9:12pm UTC](https://community.cartalk.com/t/electric-motor-question/177775/78 "2021-07-03T21:12:17Z")
> [@keith](#): > > If that is a brushless alternator rotor, what is the commutator for? What commutator? The black thing behind the small exciter generator is a three phase full wave bridge that converts its AC into DC and sends it to the field poles on the rotor, no commutator or slip rings involved whatsoever. The main winding that generates the 480 volt three phase is stationary and the four field pole magnets on the rotor turns inside it. The small exciter winding turns in its own field provided by these stationary field poles that are magnetized by a low voltage DC current provided by the automatic voltage regulator which is powered by the output AC voltage of the main winding. ![](https://global.discourse-cdn.com/cartalk/original/3X/7/1/717866a8d91a14f212d1236088b57a0d2e8ff77f.jpeg) Exciter field. ![](https://global.discourse-cdn.com/cartalk/original/3X/9/d/9d028ef8df8f93705e15eccd895494999b09b824.jpeg) Automatic voltage regulator. ---
**Author:** ![keith](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/keith/32/5518_2.png) [@keith](https://community.cartalk.com/u/keith)\ **Post date:** [July 3, 2021, 11:29pm UTC](https://community.cartalk.com/t/electric-motor-question/177775/79 "2021-07-03T23:29:47Z")
> **[Commutator (electric)](https://en.wikipedia.org/wiki/Commutator_(electric))** > > A commutator is a rotary electrical switch in certain types of electric motors and electrical generators that periodically reverses the current direction between the rotor and the external circuit. It consists of a cylinder composed of multiple metal contact segments on the rotating armature of the machine. Two or more electrical contacts called "brushes" made of a soft conductive material like carbon press against the commutator, making sliding contact with successive segments of the commutator... ---
**Author:** ![circuitsmith](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/circuitsmith/32/40376_2.png) [@circuitsmith](https://community.cartalk.com/u/circuitsmith)\ **Post date:** [July 4, 2021, 12:33am UTC](https://community.cartalk.com/t/electric-motor-question/177775/80 "2021-07-04T00:33:56Z")
> [@keith](#): > > what is the commutator for? Below is what I suspect you’re mistaking for a commutator, and I agree, it being smaller than the main poles, it has the right visual proportion and looks similar to commutator slots. But those poles do not go against brushes. Note also the poles are insulated from the windings. Think of it as two alternators on one shaft. One big, one small. ![d5074b7dd1ab0ee3c496f89d81da4ebc66c037b8_cr](https://global.discourse-cdn.com/cartalk/original/3X/f/5/f5066135c9a0a88287c3457fcf7e61f9df18f67e.jpeg) [Previous page](https://community.cartalk.com/t/electric-motor-question/177775.md?page=3) [Next page](https://community.cartalk.com/t/electric-motor-question/177775.md?page=5)