grounding ac and dc system on a electric propulsion sailboat ?!

sprinter99

New Member
Joined
Oct 29, 2020
Messages
14
hi,

I have questions about grounding/bonding. I am getting ready to install my victron 48v quattro inverter/charger, I have a 280ah 48v eve pack and a 20kw electric motor. I plan on doing my charging solely by solar and a honda suitcase generator that plugs to the victron charger.

How and where ( or do I need to ?) do I ground my Victron inverter ? do I bond my 48v dc system and ac system together with a grounding plate ? does the plate go outside the hull in the water or inside ? or should i just ground it to the prop shaft ? Any information will help as I am very overwhelmed with grounding on a boat.
 

Kruncher

New Member
Joined
Mar 9, 2022
Messages
9
Check with the manufacture regarding grounding the electric motor. I'd probably just give them a call. There might be a ground lug on the motor.

Good luck.
 

newbostonconst

Solar Addict
Joined
Sep 24, 2019
Messages
879
Guessing you have sacrificial anodes on the boat. I would search about them, I believe I watched a very good one a while back....(West Marines Channel, or Yachting Monthly)

Guessing it is best to bring all the grounds together along with the anodes. If the large component like the motor doesn't have a ground then usually you remove a bolt and add a ground with an eyelet like at the mount or to the case.

Exciting stuff....please correct me if I am wrong I am going off memory....
 

mikefitz

Photon Sorcerer
Joined
May 28, 2020
Messages
1,306
Read section 7 and 8,

Depending on the material of the hull, grounding the prop shaft and through hull valves could be complex.

I advise installing prop shaft so it's insulated from the motor and gearbox, couplings are available for this.
The shaft metalwork and thus prop to be bonded to all metal hull fittings below the water line and external anodes. This is not your earth.

The internal battery negative will be the isolated 'earth' within the boat, no grounding plate.

No shore power makes life easier.

If the hull is steel or alloy there are other considerations.

Charging via a petrol suitcase generator seems very inefficient .

If the inverter charger powers AC appliances note the requirement for protection as indicated in the pdf.

Mike
 

jdege

New Member
Joined
Dec 16, 2020
Messages
39
The boat should be grounded, and it should be bonded.

Most sailboats with inboard diesel auxiliaries are bonded through the shaft and prop. Older boats would rely on the engine itself to bond the engine's ground to the shaft, though AIUI these days it's preferred to have a direct connection from the grounding bus to the shaft.

If you had a diesel replaced with an electric, the bonding issues should have been addressed at that time. Though they may not have been.

If your electric motor is inboard, there may be enough exposed metal in the shaft to serve as a bonding plate.

I'm currently considering replacing a diesel with electric pod drives. I'll be removing the shaft and the pod will not serve as a bonding plate, so I'm going to have to add one.

There's a lot I need to learn. I'm currently working through Charlie Wing's Boatowner's Illustrated Electrical Handbook, which I'm finding very helpful.

I'm going to include one diagram from the book and call it "fair use":
 

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