# Can alternators charge EV batteries?



## dantheman (Feb 11, 2012)

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.


----------



## mora (Nov 11, 2009)

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.


----------



## dantheman (Feb 11, 2012)

mora said:


> 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.


Hmmm...I see...I guess that is what hybrids do? My wife has a Honda Civic Hybrid.

Thanks for that obvious answer...makes total sense.


----------



## MN Driver (Sep 29, 2009)

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.


----------



## icec0o1 (Sep 3, 2009)

dantheman said:


> 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.


----------



## Wild (Aug 19, 2011)

Now take that alternator and make it into a wind turbine and set up the necessary electronics and a battery bank you can then charge that leaf.


----------



## piotrsko (Dec 9, 2007)

But NOT attached to the car.


----------



## rmay635703 (Oct 23, 2008)

piotrsko said:


> But NOT attached to the car.


I have seen several non-electric model cars drive into the wind with a turbine on top, the gearing you need to do so, is such that you move very slowly though.


----------



## Wild (Aug 19, 2011)

rmay635703 said:


> I have seen several non-electric model cars drive into the wind with a turbine on top, the gearing you need to do so, is such that you move very slowly though.


Yeah let's get serious already.


----------



## Ziggythewiz (May 16, 2010)

rmay635703 said:


> I have seen several non-electric model cars drive into the wind with a turbine on top, the gearing you need to do so, is such that you move very slowly though.


It doesn't really have to be slow, you can go as fast as the gearing will allow, the key is you can drive into THE wind (which is a massive power source). You cannot drive into your own wind using this method.


----------



## dubbau (May 2, 2012)

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...


----------



## Ziggythewiz (May 16, 2010)

dubbau said:


> 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?


----------



## dubbau (May 2, 2012)

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...


----------



## jeremyjs (Sep 22, 2010)

dubbau said:


> 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...



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.


----------



## GQ1981INC (Jul 17, 2021)

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!


----------



## Ziggythewiz (May 16, 2010)

GQ1981INC said:


> 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.


----------



## brian_ (Feb 7, 2017)

GQ1981INC said:


> 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!


That's a common idea, and has appeared on several production cars. The rooftop area isn't enough for the panel to be significantly useful, but it's handy to provide power to run ventilation in a parked car (more sun = more heat but also more power).

By the way, you can't copyright a technical design - that's what a patent is for. And you can't patent something which has already been done, which this has. By the old rules, you couldn't patent anything that was obvious to people skilled in the technology, and this is certainly obvious.


----------



## brian_ (Feb 7, 2017)

It's a bit surprising that this didn't get moved into the Alternators, Free Energy, Perpetual Motion, Over Unity and all that... with the rest of this nonsense.


----------



## rmay635703 (Oct 23, 2008)

Hmm two EVs with tractor powering solar (sort of)


Redirect Notice



Owner states this setup is to allow the car to be flat towed behind an RV


----------



## brian_ (Feb 7, 2017)

rmay635703 said:


> 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.


----------



## GQ1981INC (Jul 17, 2021)

Ziggythewiz said:


> 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.


That doesn't make sense if the car is sitting and not moving or being used the panels still charge so how is it you only get 2% I would think 2% if you were driving continuos. Would I be wrong in that assumption?


----------



## brian_ (Feb 7, 2017)

GQ1981INC said:


> That doesn't make sense if the car is sitting and not moving or being used the panels still charge so how is it you only get 2% I would think 2% if you were driving continuos. Would I be wrong in that assumption?


Just pick a vehicle, work out the roof area, calculate the energy collected by solar cells covering the roof, and compare that to the consumption of the vehicle. You can't assume an amount of range increase unless you also make specific assumptions about the vehicle.


----------



## 777BoeingEngineer (Dec 20, 2021)

rmay635703 said:


> Hmm two EVs with tractor powering solar (sort of)
> 
> 
> Redirect Notice
> ...


Question: are there plans for this? Web link? What is the owners name??


----------

