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negative ground to trailer frame


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I have 2 6 volt batteries and the negative wire grounded to the chassis, but now I am seeing rust start up and what looks like battery corrosion under the battery tray. should I have the negative wire grounded to something else?

Mike Foster

2020 Transcend 221RB

2017 Chevrolet 2500 HD




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No the battery is typically grounded to the frame.  You do need to have a maintenance routine to check all your battery connections periodically and clean them and tighten them.  You also need to make sure they are properly watered if they are Lead Acid batteries.  

If you are getting excessive corrosion, you may be over charging the batteries and causing them to boil or excessively off gas.  This can happen when the RV is regularly plugged into shore power and your battery charger/converter is a “dumb” charger that constantly puts a full charge voltage to the batteries.  In other words, it does not back off the charging voltage as the batteries get close to full charge and then are at full charge.  A good smart charger/converter will have at least three stages - bulk, absorb and float - and some will have a fourth stage called equalize.

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Since the forties and fifties when it became standard in the automotive industry YES indeed the chassis/frame of vehicles was bonded to the battery NEGATIVE so I don't see that as your problem. Acid spill over and/or excessive overcharging yielding highly corrosive acidic fumes may settle in the battery holder area causing your problem. Keep an eye on electrolyte levels (Do NOT have battery over filled) and avoid overcharging and excessive outgassing can help ASSUMES YOU HAVE FLOODED LEAD ACID BATTERIES ??? A good thorough cleaning of the tray is in order followed by a good coating/treatment. On post top batteries I use the felt washers underneath followed by the red anti corrosive battery terminal spray.

 Of course a failing battery can be another problem. Most shops will test them for free, its worth a try if you're unsure of their condition ???

 Clean everything up,,,,,,,,,,,,Maintain proper level but NOT overfilled electrolyte,,,,,,,,,,,,Insure your charger is NOT overcharging,,,,,,,,,,,Have batteries checked...………….

 John T

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4 hours ago, mesa said:

should I have the negative wire grounded to something else?

As long as the ground cable is of sufficient size and the connection to the chassis is solid, that is all that is needed. If it is very close to the batteries it might be worthwhile to get a longer negative cable and move that connection farther from the batteries. For the area under the batteries, a good cleaning with a mix of water and baking soda would be a good thing. If you get rid of all of the residues and then make sure that the batteries are not being overfilled with electrolyte and you don't overcharge them, that should take care of the problem for a reasonable length of time. 

Good travelin !...............Kirk

Full-time 11+ years...... Now seasonal travelers.
Kirk & Pam's Great RV Adventure



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Mesa,  Thanks for the feedback. You may well already have it this way, but FYI if some don't, while I have my battery bank Negative frame grounded, the big main Negative cables from the Charger and Inverter and to the main DC Distribution Panel and Genset etc I HAVE CONNECTED DIRECT TO THE BATTERY NEGATIVE BUSS/TERMINAL   IE I DO  NOT use the frame as a current return for the main loads.   Sufficient sized cables properly bonded and then sealed/protected against moisture and contamination goes a long way. NOTE I prefer my main frame/chassis ground bond be made at a large main frame iron structure with an adequate size cable  NOT any thin wimpy sheet metal enclosure or box or accessory that happens to be metal.   


 Happy Early Thanksgiving to yall

John T  Still live from SKP headquarters in Livingston, Texas headed to Austin soon

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John T, If you have your negative battery cable connected to your frame and your Charger and inverter connected to the battery negative in any way, they are then connected to the frame. Chuck


Chuck and Susan      1999 Fleetwood Bounder 34            Triton V10 on Ford Chassis

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6 hours ago, chuckbear said:

John T, If you have your negative battery cable connected to your frame and your Charger and inverter connected to the battery negative in any way, they are then connected to the frame. Chuck 

Good Moring Chuck, thanks for your comments, of course I agree, you are EXACTLY CORRECT. Even though you already know all this just as FYI to others, HOWEVER I (as most others do) still use big Negative cables direct from my Inverter and Charger and Genset connected to the Batteries big main Negative Terminal/Buss   VERSUS   those currents returned SOLELY via the chassis/frame.  I would never just run Positive Cables to my Charger and Inverter and DC panel and tie the other end to frame ground alone. Its just NOT in my Electrical Engineers DNA lol. I run BOTH Pos and Neg Cables to my main DC loads and to the Panel instead of using Chassis/Frame return. But HEY sure it would "work" (subject to connection integrity and resistances etc) if you ran ONLY the Pos cables to the Charger and Inverter etc and used Chassis/Frame as the return current path even though its NOT how I do it.

The typically necessary Chassis/Frame Ground serves as a connection point for those smaller loads that actually use frame as a 12 VDC current path as typical in cars and trucks. That's not to mention how the RV Chassis/Frame is also bonded to the 120 VAC power distribution systems Equipment Ground.  

Fun chatting with you Chuck, take care be safe and Happy Thanksgiving

John T

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