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Can alternators charge EV batteries?

20K views 22 replies 13 participants last post by  777BoeingEngineer 
#1 ·
I recently had the opportunity to drive a friends Nissan Leaf. I loved it.

I know nothing about Electric Cars but was wondering why you couldn't charge the batteries with an alternator of some kind. I think this seems fairly obvious so I know there is an answer to why you cannot. Just haven't found it yet...so...could someone versed in Electric Car Motors explain that to me? Thanks.
 
#2 ·
Do you mean charging using alternators in fully electric vehicle while driving? Guess where the power to run the alternator comes from? Batteries. Motor needs power to turn and alternator also requires some power to keep going. It will never be 100% efficient (power in = power out + losses) There is always some loss of power somewhere in the way. You could charge 12V battery using alternator like in any gasoline powered car though.

Now if alternator is powered by another gasoline engine that's whole different story.
 
#4 ·
Yeah, it's a fairly common question here. Most people don't realize that an alternator puts a pretty strong drag against the engine in a normal car causing it to consume more fuel than if it wasn't there. It doesn't just spin like people think it does.

In order to waste less gas and to produce electricity while in auto-stop, your wife's Accord uses a DC-DC converter and doesn't have an alternator. I don't know if any hybrids do, it is possible that some of the early GM hybrids do but their 36 volt systems don't do much more than engine idle auto-stop anyway and so the GM models never got very popular or much more fuel efficient than other cars as far as I can tell.

For the most part, the idea behind a hybrid is to use a smaller engine so you can keep the engine under a higher load while cruising which gives it better gas mileage. Stopping the engine when it would be idling also can save a significant amount of fuel. The batteries and electric motor(s) in hybrids assist the car to provide extra torque that a smaller engine doesn't have so the driving experience isn't reduced by having a less powerful engine. I like how Honda setup its hybrid drivetrain, it is simple, low cost, and very effective way to do it. I drive a 2000 Insight and love it, and with reasonable mostly highway driving, I get 70+ mpg tanks in the summer and a 1st Gen Insight will be my conversion to electric. I've measured out battery space already and have decided which motor I'd like to fit. I like the Nissan Leaf too but the auto manufacturers could do better in terms of efficiency(my goal) but right now the major manufacturers are aiming for mainstream or slightly higher-end acceptance and I don't blame them which is why I'll convert mine instead of buying what they are selling.
 
#5 ·
I recently had the opportunity to drive a friends Nissan Leaf. I loved it.

I know nothing about Electric Cars but was wondering why you couldn't charge the batteries with an alternator of some kind. I think this seems fairly obvious so I know there is an answer to why you cannot. Just haven't found it yet...so...could someone versed in Electric Car Motors explain that to me? Thanks.
They do, it's called regenerative breaking and the alternator is the drive motor.
 
#11 ·
I see that this hasn't been talked about lately I wanted to see if you have some more information.

My thought is that I have 2 electrical circuits 2 EV batteries and a smart system to run/drive the car off of one battery and recharge the second battery using geared alternators attached to two of the wheels not being used to propel the car. I could also gear the alternators to spin 20-40 times the revolutions of the front wheels much like is done with a servo motors to other equipment.

Why would this setup not work? I understand you would have to be able to recharge the second batter as fast as you could dissipate the first one. Saying that could be done the smart system would switch batteries to now drive off the recharged second battery and now recharge the first.

I'm perplexed on why this would not work...
 
#12 ·
I'm perplexed on why this would not work...
Go open a door. Then close it and have a friend pull against it as hard as they can. Now open it again. How well did that work?

Now you pull and have your friend try to open the door.

You and your friend are batteries. What you are proposing is equivalent to you and your friend taking turns fighting each other to open the door...in an effort to make the door easier to open. Is it?
 
#13 ·
I see your point I must be missing something with the physics I just though of a external circuit that wouldn't draw on the first would some what work I mean even if you could not recharge the entire battery (Same amount of energy spent to make the momentum) you would at the least extend the range by some percentage...
 
#14 ·
There's no such thing as free energy. It has to come from somewhere and you never get it back at 100% efficiency. You would be taking power from one battery pack and transferring it to the second battery pack minus the energy you used just to move the car and the inefficiencies of your alternators putting drag on the car.

You could use regen and get some of the braking energy back, but that's it. Many hybrids and ev's already use regen to recover breaking energy. Basically, instead of transferring all your momentum to heat in the brakes it uses the ac motor as a generator when stopping to transfer some of the energy back into the batteries.

Look up conservation of energy. You should probably refrain from making any more posts until you understand it, but that's up to you.
 
#15 ·
Ok geniuses why hasn't anyone thought of a solar panel built enlayed in the rooftop or as the sunroof. Not only would it be nice looking similar to a carbon fiber accent if done properly, but it would absolutely increase the distance to which the car could travel.
"Solar Roof Panels concept Copyright 2021 GQ1981INC all rights reserved" my crazy idea, just saying!
 
#16 ·
Ok geniuses why hasn't anyone thought of a solar panel built enlayed in the rooftop or as the sunroof.
It's been thought hundreds of times, but for most vehicles would not be worth it. It used to be you could hope for an extra 2% range on a normal car, maybe that's up to 6% with the latest panels. It could only substantially help on an RV or something with a large surface area spending days or weeks between drives.
 
#20 · (Edited)
Owner states this setup is to allow the car to be flat towed behind an RV

View attachment 123153
Which makes no sense. Generating some power (no matter how inefficiently) is not necessary to flat-tow. The Bolt owner's manual (at least the 2019 one that I checked) prohibits flat towing (which they call "dinghy towing", also called RV towing), noting that:
Caution
If the vehicle is towed with all four wheels on the ground, the drivetrain components could be damaged. The repairs would not be covered by the vehicle warranty. Do not tow the vehicle with all four wheels on the ground.
and
The vehicle was not designed to be towed with all four wheels on the ground. If the vehicle must be towed, a dolly should be used.
Generating power fundamentally won't change that, although if the damage would be due to a lack of transaxle and motor bearing oil circulation, and the owner of this Bolt has rigged it to run an electric pump to address this, then power would be needed for that pump.

This rig is the subject of various online discussions, none of which contain any real information beyond the photo. Most are full of "free energy" nonsense. The owner is probably trying to charge the Bolt's battery (just the 12 V battery? perhaps the HV battery?), probably to make up for the energy consumption of a pump, but it would make vastly more sense to do that with an electrical connection to the tow vehicle.
 
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