 | Home > In Car Electronics > Inverter - How to earth? |
 
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| Landowner Member Since: 06 Jan 2023 Location: Somerset Posts: 60   
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Hi, is the earth lug also connected to the -ve (battery) input?
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1st Feb 2023 11:07pm |
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| lolo Member Since: 18 Jul 2021 Location: Vaud Posts: 118  
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No, not yet, might be, I admit that I do not know what to connect to what or nothing regarding this earth
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1st Feb 2023 11:10pm |
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| camelman Member Since: 27 Feb 2013 Location: Peak District Posts: 3314
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That's a big inverter, you must be powering something large!
Worth noting that 2500w from a 12v supply = 200+ Amps so will drain the battery in no time...  |
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1st Feb 2023 11:19pm |
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| lolo Member Since: 18 Jul 2021 Location: Vaud Posts: 118
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About daily 20min of portable induction cooktop + 5min of coffee machine on a 200A lithium battery. It will be ok... up to 57min
 But this still do answer on how to earth it or not... |
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1st Feb 2023 11:31pm |
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| Landowner Member Since: 06 Jan 2023 Location: Somerset Posts: 60
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Yes, the lug should be connected to a good common earth point on the vehicle.
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2nd Feb 2023 7:22am |
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| miker Member Since: 13 Sep 2015 Location: Surrey Posts: 1758 
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In theory that is for sourcing a local earth when you are using mains from inside the vehicle and able to touch things outside the vehicle. So in practise that would be an earth rod.
In reality it depends... If all your loads are double insulated, then it's not anything to worry about. If you want to do some reading up, look at you local electrical standards for generators installed in vehicles. It's possible (though not guaranteed) that the earth stud already has continuity to vehicle negative through it's case and possibly the negative battery lead. |
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2nd Feb 2023 11:49am |
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| MadTom Member Since: 10 Sep 2013 Location: Olomouc Posts: 564  
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Just imagine damaged isolation on the output cable to you induction plate. Somethink like wire chaffing to car body because of long term vibrations. Without this grounding you can touch 230V on the car body, and this is really not healthy. This ground is not for power purposes, but for safety, so it will trip some fuse in the inverter instead you. And becasue it is for safety, in cannot be replaced by power ground connection between inverter - battery minus - car body. In case of car body to battery minus wire broke, inverter would still work, but the safety connection is gone.
For this power use thick ground wire - at least 6mm2. Induction should have double insulation but I'll not trust this. Just imagine watter in the induction. "Drobek" = The Small One - Discovery 2, "Blufínek" = The Blue Thing - Defender 130, and for me at least Ford Mondeo  |
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2nd Feb 2023 2:19pm |
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| MarkBrown Member Since: 03 Oct 2022 Location: Mid Wales Posts: 315 
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My 500 watt inverter is connected via the positive cable to a battery isolator, then to the second battery via a voltage sensitive relay. Nothing is left on unless I'm in the vehicle. The earth connection is connected to earth, which is by the second battery. Hope this helps.
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2nd Feb 2023 3:16pm |
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| rallysteve Member Since: 10 Feb 2014 Location: Cumbria Posts: 2196 
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I am not convinced that is the case with a battery based inverter system. The voltage source is locally derived and totally separated from the ground plane by the vehicle tyres so there is no complete current path. Therefore there would be no touch voltage between the mains and the actual ground, it would be like holding the positive terminal of one battery and the negative of another battery, no actual current would flow. Happy to be proved wrong though....  02' 110 TD5 Double Cab Rebuild Thread
84' 90 3.9 V8 Caged Pickup Build Thread - Now For Sale Mobile Diesel Heater Build Thread |
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2nd Feb 2023 3:56pm |
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| lolo Member Since: 18 Jul 2021 Location: Vaud Posts: 118
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Thank you all for your feedback and info. It is not an easy subject.
In my case I am not connected to shore power, my appliances are type I (plug with 3 poles, 1 phase, 1 neutral, 1 yellow/green earth wire), my inverter earth bolt is internally bound to earth cable of the two 220v outlets. In short below what an electrician told me, at least what I have understood: - inverter provides a floating neutral. Neutral is not connected to earth. There is no earth in the car. It is useless to add a Residual Circuit Device (RCD) as there is no earth. - inverter case/chassis must never be connected to the vehicle chassis, this to avoid a mass loop and avoid to potentially inject 220v to 12v circuit in case of isolation fault. - using the appliance from inside the car and being inside the car: no problem. In case of insulation fault, the earth cable of the type I appliance will bring the current back to the inverter, inverter (fuse) will blow and break the circuit. - using the appliance from outside the car and touching the ground: problem. So in this case the inverter case/chassis or appliance case/chassis must be connected to an earth rod sticked into the ground. - probability to have an insulation default on appliance in good condition is very low, but you never know. I hope I have well understood. If not, I might become more brilliant than usual |
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4th Feb 2023 11:10am |
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