Using Chassis for Negative Ground?
- Thread starter Papa
- Start date
liveforphysics
100 TW
Keep in mind most brushed controllers have a direct connection to the positive lead, and then PWM the negative lead to control current.
Check the leads on the motor for isolation between the motor case and the windings. Just checking ohms on a DMM will do this for you. If its isolated, and its a rear hub so it won't be trying to arc the head tube bearings, then it should work out fine to use the frame as a conductor. It does seem like more work to electrically tap the frame in multiple places than to run a wire though.
Best Wishes,
-Luke
Check the leads on the motor for isolation between the motor case and the windings. Just checking ohms on a DMM will do this for you. If its isolated, and its a rear hub so it won't be trying to arc the head tube bearings, then it should work out fine to use the frame as a conductor. It does seem like more work to electrically tap the frame in multiple places than to run a wire though.
Best Wishes,
-Luke
Thanks Luke.
The motors are brushless and I measured zero continuity from the case to any of the three windings. No motor on the front (this is a delta trike). However, I do have rear swing arm joints to contend with, but I can just use short grounding jumpers between members. My only other concern is inhibiting galvanic corrosion at the brass grounding terminals attached to some frame members, which are aluminum. Any inhibitors available? Appreciate the help.
The motors are brushless and I measured zero continuity from the case to any of the three windings. No motor on the front (this is a delta trike). However, I do have rear swing arm joints to contend with, but I can just use short grounding jumpers between members. My only other concern is inhibiting galvanic corrosion at the brass grounding terminals attached to some frame members, which are aluminum. Any inhibitors available? Appreciate the help.
Perhaps NoAlOx.
NeilP
1 GW
As the title post says, Anyone ground their bike chassis to battery negative?
I do not, but wondered about it today
I do not, but wondered about it today
MadRhino
100 GW
Contrary, it is isolated. I don't want to be caught between my 24s Lipo pos and my bike that would be grounded to the neg. :|
Gregory
100 kW
I think recently AussieJesters controller was accidentally grounded to the frame, and it blew.
NeilP
1 GW
Well sounds like something would have been wrong with his controller in the first place for that to happen. My controller case is grounded to the frame by the mere fact that it is bolted down on the water bottle/accessory mounting points. But grounding the controller case to the frame is not the same as connecting battery negative to the frame.
What happened in AussieJesters case?
What happened in AussieJesters case?
biohazardman
100 kW
The less chance I have to be part of a live high voltage circuit the better I feel about it. Although I do feel the chance is remote anything will happen in most cases. It is still less of a chance when things are isolated.
Farfle
100 kW
I always keep the frame isolated... ALWAYS. it keeps stuff from getting real if a connector accidently grounds to the frame.
NeilP
1 GW
I just find it odd that seems to be the way that we all do it, where as any other vehicle works the the other way..chassis is ground
MadRhino
100 GW
On a vehicle where the electric system is low voltage and power, for purpose of lights and controls, it makes sense to use the frame as a ground. Yet on an electric powered vehicle system that can short 40+ Kw, the same logic doesn't apply.
fizzit
10 kW
I don't know of any electric vehicles that use their chassis as a ground for the traction battery.
SamTexas
1 MW
Using the chassis as a big, zero cost cable is a great idea for low voltage system (up to 24V?). FWIW, I use my regular bicycle frame as the negative cable for my lights (7.4V) so I only have run one single tiny wire to the back for the rear LEDs.
NeilP
1 GW
fizzit said:
I was not thinking to use it as part of the wiring for the main power to the controller, that was not the intention. Not really planning on doing it myself, but I was building a MOSFET switch the other day where I was considering using the tab on the 4110's and the heatsink bar as part of the circuit as has been mentioned on the active inrush thread, but then I thought..no I can't do that as mounting tto the chassis is earth..but then realised that no it was not..as we don't earth to chassis...which got me wondering if any one do.
Anyone know what production electric vehicles..(Nissan leaf/ RAV4 / Zero ) do ? do they use a chassis earth?
shock
1 kW
I've done this by screwing down my lyen controller to the frame. No negative effects. No pun intended lol. Grounding to frame can actually help if the system is built and fused properly.
AussieJester
1 TW
I had grounded controller touched the positive wires from the throttle to frame by accident
Put 75v through the controller popping one fet, a diode and a cap....that I could see anyways...half way through building new controller, stuck till I get to JayCar for some of that braided stuff that removes solder, need to clean up a few spots.
KiM
Put 75v through the controller popping one fet, a diode and a cap....that I could see anyways...half way through building new controller, stuck till I get to JayCar for some of that braided stuff that removes solder, need to clean up a few spots.
KiM
Samd
10 MW
Seems to be a high instance of phase wires on frock motors shorting to the axle.
I'm thinking it wouldn't be ideal.
Sorry to mention frocks Jester
I'm thinking it wouldn't be ideal.
Sorry to mention frocks Jester
No they do not. That would mean just one wire a person would need to touch to DIE.NeilP said:
You have to watch when you use step down voltage regulators/transformers or switch mods some of the cheep ones are not isolated so if you ground the 12v negative it will effectively ground the traction pack and there is DIY ev guys who don't know this. But there is a Tesla video going over the safety of the Tesla in the event of a crash etc. They discuss this more there.
NEVER connect anything to chassis over 12v ever!
NeilP
1 GW
Screwing the controller to the frame will not actually ground the system though. The negative line is not common to the chassis of the controller, it is internally isolated.
AussieJester, sounds like you had other issues that caused your problem. Even with the controller bolted to the bike frame, (at least with all controllers I have seen), you could touch the 5v throttle power feed to the case and all that would do is raise the case voltage to 5volts. There is no way that can somehow put 75 volt through controller,Since it is electrically insulated from the PCB inside it would not zap anything on the board.
Even if you had a battery voltage indicator wire to the throttle, so had the 75volt line as well, and flashed that too the case there would be no issue for the same reason.
The controller case can be at full battery voltage and will still work fine. My mate, Mark, had this on an Electric Rider Xlyte controller. There was physical damage to the insulating mounting strip that insulates the positive side FETS to the heatsink bar. This caused the whole controller case to be at full battery voltage. Bike ran perfectly like this for weeks, he had the controller wedged between fibre board in the battery box. Working on bike one day, while connected to battery he managed to touch a negative lead to the case of the controller, a spark and small flash and controller died.
He called me to look, I soon found case was live. Opened case, no short between PCB traces and case. Opened it up...heatsink bar was live. Removing FETS showed a hole and piece of swarf inderneath a positive FET. Been there since new.
AussieJester, sounds like you had other issues that caused your problem. Even with the controller bolted to the bike frame, (at least with all controllers I have seen), you could touch the 5v throttle power feed to the case and all that would do is raise the case voltage to 5volts. There is no way that can somehow put 75 volt through controller,Since it is electrically insulated from the PCB inside it would not zap anything on the board.
Even if you had a battery voltage indicator wire to the throttle, so had the 75volt line as well, and flashed that too the case there would be no issue for the same reason.
The controller case can be at full battery voltage and will still work fine. My mate, Mark, had this on an Electric Rider Xlyte controller. There was physical damage to the insulating mounting strip that insulates the positive side FETS to the heatsink bar. This caused the whole controller case to be at full battery voltage. Bike ran perfectly like this for weeks, he had the controller wedged between fibre board in the battery box. Working on bike one day, while connected to battery he managed to touch a negative lead to the case of the controller, a spark and small flash and controller died.
He called me to look, I soon found case was live. Opened case, no short between PCB traces and case. Opened it up...heatsink bar was live. Removing FETS showed a hole and piece of swarf inderneath a positive FET. Been there since new.
NeilP
1 GW
Arlo1 said:
Bit dramatic Arlo, but I see what you are saying.
Oh and you got your quote levels in a twist..I said what you attributed to fizzit above..powersupply
100 W
Hi all.
I don't understand why ebikes/scooters etc don't use the chassis to distribute the minus (-) of the battery (or + for that matter).
Cars do it for more than 100 years.
Bicycles do it longer than that even.
I mean the Chinese cut corners everywhere to satisfy our call for yet cheaper prices.
But even they use two (flimsy) wires to carry 30A or more from the battery all the way to the controller. And each and every lamp on my (metal) scooter has 2 wires!
I checked and rechecked some ebikes, everything is isolated, from the motor to the lights.
Any clue?
I don't understand why ebikes/scooters etc don't use the chassis to distribute the minus (-) of the battery (or + for that matter).
Cars do it for more than 100 years.
Bicycles do it longer than that even.
I mean the Chinese cut corners everywhere to satisfy our call for yet cheaper prices.
But even they use two (flimsy) wires to carry 30A or more from the battery all the way to the controller. And each and every lamp on my (metal) scooter has 2 wires!
I checked and rechecked some ebikes, everything is isolated, from the motor to the lights.
Any clue?
You can do it if you want to. I used to use the frame for my 12V lighting ground, though I don't now.
But one major drawback to doing it is that once the frame is part of the power path, every wire that runs anywhere near the frame must be mounted and insulated in a way that it cannot rub on the frame such that the insulation could wear thru--otherwise you will be shorting out whatever wire that is. If it happens to be your pack positive, well, that could be disastrous if you haven't got a fused or breakered battery output for some reason. Could also be destructive if it was a motor phase output--that could not only blow FETs in the controller, but also actively brake your wheel (check out "plug braking"), which if it happened while you were riding could cause a crash.
Another issue is that if you have anything that needs power/ground that is past a bearing point, you have to run a wire to it--You wouldn't want to trust that the bearings would pass current without resistance (wherever there is resistance, there is heating). So stuff on your forks or handlebars will need a separate ground wire run from your frame to it.
But one major drawback to doing it is that once the frame is part of the power path, every wire that runs anywhere near the frame must be mounted and insulated in a way that it cannot rub on the frame such that the insulation could wear thru--otherwise you will be shorting out whatever wire that is. If it happens to be your pack positive, well, that could be disastrous if you haven't got a fused or breakered battery output for some reason. Could also be destructive if it was a motor phase output--that could not only blow FETs in the controller, but also actively brake your wheel (check out "plug braking"), which if it happened while you were riding could cause a crash.
Another issue is that if you have anything that needs power/ground that is past a bearing point, you have to run a wire to it--You wouldn't want to trust that the bearings would pass current without resistance (wherever there is resistance, there is heating). So stuff on your forks or handlebars will need a separate ground wire run from your frame to it.
AussieJester
1 TW
I wouldnt, i did accidently (unbeknown to me) and touched a + wire to frame, it blew the shit out of my controller :-(
KiM
KiM
the higher the voltage, the worst the idea becomes...
also, some bicycles have various types of metal that will react badly ( galvanic reaction i think is what it's called )
also, some bicycles have various types of metal that will react badly ( galvanic reaction i think is what it's called )
