House batterry ground

Tikvah · August 04, 2015, 06:25:51 PM

Dumb question...
Every diagram for house batteries/inverter I've looked at does NOT show the house batteries being grounded. The inverter itself has a small chassis ground. Is there a reason I wouldn't ground the bank of batteries?

Dave

Iceni John · August 04, 2015, 08:01:06 PM

Are you looking at diagrams for RE systems in houses, or for mobile uses such as in boats and vehicles? A true ground normally isn't used in an RV or bus, except when plugged into shore power. Any battery system, whether chassis or house, needs both positive and negative connections at the batteries, but in vehicles the negative is usually bonded to the body/frame. Is that what you mean?

My inverter has a 4/0 negative cable running back to a negative busbar made from C110 copper that is connected to each house battery bank's negative terminals (I have two separate house battery banks, but that's just me!) via their catastrophe fuses. This negative busbar is also bonded to the metal structure of the bus. I also have a separate green 2AWG "ground" cable from the inverter to a bolt going through my frame rails, but in a mobile application it's really not needed. If this inverter were in a house the ground would be an actual path for stray current to dissipate safely, but in a bus that cannot happen.

John

bevans6 · August 05, 2015, 02:58:22 AM

I use a full sized cable to a 3/8" bolt that is through the floor of the battery compartment. I think, I can't remember, that it was originally the ground for the condenser fan motor. My inverter is grounded the same way. I don't run a separate cable from the inverter to the batteries, I use the grounds to complete the power circuit.

Brian

luvrbus · August 05, 2015, 05:26:36 AM

? for the electrical guys how could battery bank produce power without a ground

Tikvah · August 05, 2015, 05:36:41 AM

Seems the bank would NEED to be grounded to the chassis for the bus alternator to charge properly. So, I'm convinced I'm going to add a 4/0 cable from the inverter battery "-" to the chassis. I'll add a 3/8" bolt and use it for a few various battery grounds in that area.

Thanks for the help.

Darkspeed · August 05, 2015, 07:10:47 AM

It is not a ground (earth ground) in a mobile electrical system.

It is either frame positive or frame negative, with frame negative being the most common.

There is no connection to ground (earth ground) on the bus unless you are connected to the rv park pole then it becomes frame negative bonded to ground (and also possibly service neutral).

Because your bus does not have a ground rod like a house, ground and neutral should not be bonded in the bus service entrance or in the bus ~120 / 240 ac panel.

The rv hook up box on the pole should either have a ground wire to the parks main service breaker box or it should have ground and neutral bonded with an appropriate ground rod at the rv hook up box.

Any good inverter should have its own grounding lug that should be connected to the ground terminal on bus ac outlets as well as the ground wire in the rv service cord.

Some ( most ) inverters will have continuity between the frame and the negative side of the battery bank.

Shock = If your bus frame is connected the inverter ground lug and your ground and neutral are bonded in your bus 120v panel, if you then have a short in an appliance, your bus frame becomes ~120ac unless you are connected to ground rod to dissipate the potential.

There are a lot of variables depending on equipment ( and mistakes in the wiring on the park rv hook up box )

Tikvah · August 05, 2015, 08:01:18 AM

I stand corrected in my terminology.

Battery negative. My question could be interpreted as asking if the house battery bank negative should be attached to bus body.

I think the term "ground" is commonly miss-used, but common just the same.

So, corrected as I am, my little brain will still go and ground those batteries to the bus body.

Darkspeed · August 05, 2015, 08:14:26 AM

Tikvah, i was not trying to correct you .. just trying to help

Does your inverter have a diagram with battery bank negative tied to the frame, most of the time they are because the generator / alternator negative is usually tied to the frame giving you a frame negative.

Darkspeed · August 05, 2015, 08:21:08 AM

A good way to check is take a continuity meter and touch one lead to the inverter ground lug and one lead to the battery negative connector on the inverter and if you have continuity then you should be good to go, but i always like to look at the diagrams to make sure..