Homemade regen braking to charge solar house batteries....

[Thomas Barlow]

Hey what's up guys I came up with this crazy idea the other day. So my rig is a 2001 e450 shuttle bus with the 7.3 powerstroke. I bought it for $2,700 a couple years ago and it has been the best purchase I ever made.

I lucked out and it came with a electromagnetic drive shaft break called a Telma which essentially allows the first 25% of my stopping power to be done via frictionless magnetic eddy currents in these big steel spinny disks on the driveshaft.

It works really really well and got me thinking instead of drawing 150 amps from the alternator to power the Telma what if there was a way to attach an "alternator/ 12v generator" to the drive shaft but was only applied load "charges" when you press the brakes.

I'm thinking a Ford alternator only requires a 12 volt reference signal and if you were to connect that to the truck's brake lights it would only be charging while you're on the brakes.

I'm going to attempt to retrofit a 200 amp truck alternator onto the drive shaft so every time I am slowing down for a red light or whatever i am charging a full 200amps into my lifePo4 batteries

Seems like free juice to me.

What do you guys think because my 1260 Watts on the roof is not cutting it.

Attached are pics of the Telma Brake.

 

[FilterGuy]

I am not sure how practical it is but that sounds like a fun project!

I'm thinking a Ford alternator only requires a 12 volt reference signal and if you were to connect that to the truck's brake lights it would only be charging while you're on the brakes.

Yes, you definitely will want an alternator with an external voltage regulator so you can control the coils.

The big question is this: Will the added friction of the alternator reduce your millage too much?

 

[FilterGuy]

On a shuttle bus, they are constantly starting and stopping so the break wear can be extreme. Consequently any milage loss from the Telma is probably compensated by reduced maintenance. Your situation is different.

BTW: Is that cable harness draped on the drive shaft normal? It seems like that would be a problem.

 

[schmism]

I'm going to attempt to retrofit a 200 amp truck alternator onto the drive shaft so every time I am slowing down for a red light or whatever i am charging a full 200amps into my lifePo4 batteries

200a output from a 200a alternator is at like 6000 alternator rpm. Driveshaft rpm is significantly lower than engine rpm. slowing down for a red light = extremely low rpm = extremely low alternator output. This is why this plan does not work.

 

[FilterGuy]

200a output from a 200a alternator is at like 6000 alternator rpm. Driveshaft rpm is significantly lower than engine rpm. slowing down for a red light = extremely low rpm = extremely low alternator output. This is why this plan does not work.

Good point. You would have to 'gear up' to get the needed RPM and the gear ratio would be much higher than a simple pulley system would provide. You would probably be better off finding generator that can run at a lower RPM.

BTW: This kinda reminds me of the generators that were powered off the wheels on the old train caboose.

 

[schmism]

Good point. You would have to 'gear up' to get the needed RPM and the gear ratio would be much higher than a simple pulley system would provide. You would probably be better off finding generator that can run at a lower RPM.

BTW: This kinda reminds me of the generators that were powered off the wheels on the old train caboose.

This plan doesn't work because if its sped up via belts/gears to be in a decent range at low ground speed. at high ground speed you overspeed the alternator. so now you have to build a system that monitors ground speed and engages when its at a low enough ground speed to work.
and what about downhill at high ground speed (down the backside of the mountain) you just throw all that way because you'll over speed it.

So again, its not a system that can just be kluged onto an ICE powertrain and work as it does on electric cars. Its apples and oranges.

 

[FilterGuy]

This plan doesn't work because if its sped up via belts/gears to be in a decent range at low ground speed. at high ground speed you overspeed the alternator. so now you have to build a system that monitors ground speed and engages when its at a low enough ground speed to work.
and what about downhill at high ground speed (down the backside of the mountain) you just throw all that way because you'll over speed it.

So again, its not a system that can just be kluged onto an ICE powertrain and work as it does on electric cars. Its apples and oranges.

Yup.... the system would need to be able to 'spin' at high RPMs for long periods. However, breaking is not always going to be low RPMs, Breaking happens at all speeds.... so it might work for highway breaking but at city breaking, the generation may be too low to do much.

If you started with a generator that was designed for generation at lower RPMs, you would not have to gear it as much and you could probably get a larger RPM range of production....but that is your point: The 'regen' system has to be designed for the need and an alternator probably does not fit the design parameters of the need.

Your overall point is valid, and it mirrors my first post on this thread:

I am not sure how practical it is but that sounds like a fun project!

The project probably won't work as described but it is fun to contemplate how it could be done.

 

[Tecnodave]

In real world dynamic braking is done on virtually all trains......They are diesel electric..the diesel engine (4500-6000 hp.) spins a large generator which is 600 volts DC or 3 phase AC....this is fed to axle motor/generators on each axle of the engine. On dynamic braking the drive motor/generators light up huge resistor banks at the very back end of the locomotive.....thats 1250 kw. per axle and 6 axles on a modern locomotive.....now with a freight train coming down a mountain with 6 loco’s....that is enough power to light a city....blown away as heat, and we wonder about global warming...electrically powered trains recharge the overhead power network on dynamic braking

 

[12VoltInstalls]

I read all this but my first thought is the same: 768W is one horsepower. How many horsepower is required for zero-to-sixty? Multiply that by 768 …
Since your alternator presents a “shorted load” of around 2500W and you need guessing 115,000W to provide comparative braking power.
So a magnetic field and coils could be designed with an electrical load variably presented- but the diameter and mass would render this impractical.

However, alternator charging could be done by only presenting the battery charging load under braking for the full ~3HP effect A second alternator with a small pulley could be incorporated for up to 5-6HP of braking power.
I don’t see any other way