School Bus Conversion Resources

School Bus Conversion Resources (
-   Electrical, Charging and Solar (
-   -   Lift battery charge wiring?? (

Foxpen 08-19-2018 10:20 PM

Lift battery charge wiring??
I took a wheelchair lift off of my Ford E450 shuttle. I canít figure out the wiring on it and maybe you guys can help. Thereís a positive 2awg that runs from the start battery to a charge battery, then on back to where the lift was. The negative wire that was on the charge battery is connected to a lug on the starter. I canít find a relay of any sort. Any ideas why not? No need as the bus is usually running when the lift would be used?? Iíd like to use the existing positive wiring and splice an isolator/relay into it to charge my battery bank, but I canít figure that negative wire to the starter out- any help? Thanks!

roach711 08-20-2018 12:32 AM

Mine has that same negative cable attached to one of the starter hold down bolts. I assume it's there to provide a good ground for the starter.

BlackJohn 08-20-2018 10:52 AM

Sounds like both batteries are getting charged by the alternator now.

grounding to the starter was probably one of the easier options but works ok.

To reuse the lift cable for charging the battery you may want to shorten it up if it goes front to back, can't really say without pics.
Isolator is an easy addition and can be used to boost the staring battery if needed.


Foxpen 08-20-2018 11:18 AM

Can you explain why the negative grounds from the starter? My battery bank is in the very back of the bus- which the positive and neg already run to. Do you think it needs to be shortened due to drop in voltage?

roach711 08-21-2018 09:56 PM

There are two ways to complete a DC circuit, run dedicated positive and negative cables from the battery to the device or run only a positive cable to the device and ground the device to the steel body or frame.

Most grounds in a vehicle are attached to the body/frame. The problem with this setup is that there can be bad connections between the battery and the device which can limit the current available to the device. The dedicated ground from your starter to the battery just gives a direct and high current ground connection for the starter. You'll find several of these ground straps connected between the engine and frame and the frame to the body (well, not your fiberglass body).

Your starter has that large negative ground attached to the starter frame, a large positive cable attached to the top of the starter and a small wire attached to the starter solenoid which is what makes the connection when you turn the key.

As connected, both of your batteries cabled together become one large starting battery so you don't want to connect your house bank to them without some way to prevent the house bank from drawing down the starting batteries while camping. You can use a simple relay or an electronic isolater to do this.

BlackJohn 08-21-2018 10:34 PM


Originally Posted by Foxpen (Post 287160)
Can you explain why the negative grounds from the starter? My battery bank is in the very back of the bus- which the positive and neg already run to. Do you think it needs to be shortened due to drop in voltage?

Starting and lift batteries both in the back? How far from the alternator?
I don't know the physical layout of your start battery and lift battery and alternator. Your info doesn't mention this and didn't you say that you want to keep and use the lift power for something else? What and where is this going?
Short cables will allow better charging and save your alternator from a lot of hard hot work trying to charge at long length from it.

Grounding of the starter is most important for it to function properly with enough cranking power to do the job. Everything grounds through the main block then for continuity to ground on the frame.


Foxpen 08-21-2018 11:00 PM

Thanks to you gentleman for getting back to me. Should have been clearer BlackJohn- my starter battery is under the hood as normal, 18-24 inches from the alternator. The lift battery was approximately halfway down bus length on the chassis, with 2awg running on back to the rear where the lift was. My intention is to move my two battery bank to the very back where the lift was. Unfortunately, this is pretty far (14 feet) from the alternator. Do you guys know how critical it is to keep a VSR/isolator close to the start battery? Can I splice it in 4-6' away from the start battery with 2awg and be alright?

BlackJohn 08-21-2018 11:15 PM

If you have a certain isolator in mind, then check its specific limitations with the manufacturer. Electrical characteristics will vary from brand to brand.
What kind is your alternator and what output is it rated for?


Foxpen 08-21-2018 11:20 PM

Hmm, I don't know that John- I'll check it out and get back

roach711 08-22-2018 02:59 AM

I'm assuming you're putting your house bank in the back, not the starting batteries.

In that case you should size the cable from the isolater to the house bank to handle charging current (not starting current) unless you want the option to connect the house bank and the starting bank for emergency starting.

When it comes to electrical cables bigger is better. I'd be tempted to change out that #2 cable and put in some 2/0 cable to give some future flexibility.

BlackJohn 08-22-2018 12:56 PM

Final layout will have much to do with this as will type of batteries used for house. Not sure what you have in mind but there are some well versed members here on battery differences.


Nant 03-26-2021 02:41 PM

With lift no longer in use and removed and gone to the scrap yard. I have the lift power source available for charging a battery bank now?
And I still need to put in an isolater for the bank?

I have four six volt 225 ah Interstate GC2 Extreme batteries that I can place within 2 feet or less from the house battery on my 1999 E350 Shuttle Bus (Eldorado body). Fully intend to cable up in series and parallel to achieve the 12 volts I need and get the amps (450/225) AND solar panels, soon there after.. Can this be possible?
As I want to utilize the lift power source for the bank and use a 3000/6000 Watt Powerdrive Inverter.

(I've been reading about the connection with a cannon plug as well) (so I'm curious if I can inÁorporate the cannon plug in the set up as well).

I just want to use what I already have in bus. And I figured since I am not going to have lift any longer to use that power available I could try to use it for something else.

It's all for the purpose of Mobile Grooming appliances.

P. S. I also have the electric swing door motor being powered by something, somewhere as well and I disengaged the motor shaft ( the emergency lever so I can open door manually) and I intend to put a lever for manual operation anyways.

I love you all on this site. You are my go to reads and bus authority advice.

As I refuse to watch the news any longer ;)

Thank You! And I Thank God for you all!

All times are GMT -5. The time now is 10:35 AM.

Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2022, vBulletin Solutions, Inc.