Converter and Battery Question

Hello all,

I plan on installing an inverter in my travel trailer in the near future, as well as moving my battery from outside the trailer to the front storage compartment to minimize the distance between the battery and inverter, as well as reduce the possibility of theft once I upgrade my battery bank to something more expensive.

My first question is about the ground wire for the battery. It is currently grounded to the frame outside the coach, meaning the positive wire connects to the trailer electrical system, and the ground just dumps to the frame. I'm assuming that if I move the battery inside, I just need to reroute the ground to wire into the storage compartment and to the battery, correct? It doesn't need to be connected to anything else? What about when I eventually install a solar charge controller? Just need to move the negative battery cable to the controller and ground the controller at that point, right?

My second question is about the converter. My electrical panel has a breaker for the converter that allows me to shut it off, and when I do that the 12V system still appears to work just fine. I have the type that plugs into an AC outlet, not one that is wired directly into the panel. I've read online that sometimes removing the converter completely can disable the 12V system, which I suppose means the converter not only charges the battery, but also powers the 12V when plugged into shore power. Is this accurate, or is the 12V side of the panel powered directly by the battery? Is it different for different manufacturers? I'd like to relocate the converter to be next to the battery setup so everything battery related is together, but if I have to run wire through the coach to do it I think I might not bother. My RV came with the "extreme weather" package, so the entire bottom is covered with insulation, and I'm not confident I can run the wire through the floor without hitting obstructions.

Thanks!

14 Replies

cavie
Explorer
Mar 27, 2020
Before you do anything, the storage compartment must be HIGHLY vented at ALL TIMES and HIGHLY sealed off from the interior of the trailer. Installed in a battery box that is vented to the outside is one way. Battery vented gases can kill you.

The wires from the inverter to the battery must be sized to the wattage of the inverter installed and the distance to the battery. It's called voltage drop. They will be large. You cannot run the complete trailer off the inverter. You will need to install a inverter sub panel and wire just a few things to it. Batteries do not provide enough power to run A/C and WH's. Sounds like it's time for an electrician.

The 12 volt system works with the converter turned off because it keeps the battery charged. If it is off all will work until the battery goes dead.
avarusbrightfyr
Explorer
Mar 27, 2020
theoldwizard1 wrote:
If you have not bought your inverter yet, buy on that is a combination inverter/charger/transfer switch. Much easier to install and use ! Basically, you remove/bypass your existing converter charger.

Heavy loads (such as your new inverter/charger) should have their positive and negative (ground) connection directly. If there is a ground bus bar inside of your DC fuse panel, you should run a heavy gauge wire from that to the battery negative post.

Small loads (lights, typical 12VDC outlets) can use the frame ground.

Thanks for the suggestion. I'm trying to find a balance between convenience and price. I've looked into inverter chargers, and the decent ones appear to be items like the Victron Multiplus for $1,200 or the GoPower IC 3000 at around $1,400. From what I've read,
other models appear to have issues powering both sides of the 50 amp service.

For half that price I can buy a 3000w inverter, a brand new converter, a 30A outlet to wire to the inverter so I can plug my RV power cord in that way with an adapter, a switch that will automatically cut off power to the converter, and the various wiring and connectors required to connect it all together. I also think that doing it this way will make it so that if a part gets damaged, it's more easily repairable or replaceable than a factory produced single unit.

At least that's the hope anyway...
theoldwizard1
Explorer II
Mar 27, 2020
If you have not bought your inverter yet, buy on that is a combination inverter/charger/transfer switch. Much easier to install and use ! Basically, you remove/bypass your existing converter charger.

Heavy loads (such as your new inverter/charger) should have their positive and negative (ground) connection directly. If there is a ground bus bar inside of your DC fuse panel, you should run a heavy gauge wire from that to the battery negative post.

Small loads (lights, typical 12VDC outlets) can use the frame ground.
time2roll
Nomad
Mar 26, 2020
avarusbrightfyre wrote:
My second question is about the converter. My electrical panel has a breaker for the converter that allows me to shut it off, and when I do that the 12V system still appears to work just fine. I have the type that plugs into an AC outlet, not one that is wired directly into the panel. I've read online that sometimes removing the converter completely can disable the 12V system, which I suppose means the converter not only charges the battery, but also powers the 12V when plugged into shore power. Is this accurate, or is the 12V side of the panel powered directly by the battery? Is it different for different manufacturers? I'd like to relocate the converter to be next to the battery setup so everything battery related is together, but if I have to run wire through the coach to do it I think I might not bother. My RV came with the "extreme weather" package, so the entire bottom is covered with insulation, and I'm not confident I can run the wire through the floor without hitting obstructions.

Thanks!
The battery should run the RV with or without a converter. That is until the battery is dead. If you have a charging system direct on the battery you are good to go.
wa8yxm
Explorer III
Mar 26, 2020
I agree both wires from converter should go direct to battery. The frame is often "negative Ground" but...... the connections may be less than optiomal so it should be direct connected.

As for the 12 volt stuff working with the CONV breaker off.. Yes. that's what the battery does. it powers the 12 volt side of life when the converter is off due to breaker trip, shut off or loss of shore power.

True story: For reasons of electrical safety I have a Surge Guard system (Mine is the TRC but well I would rather have the Progressive Industries but one "Heck of a sale" decided me)

The other day we had a thunderstorm. One lightening flash was within half a mile of where I'm parked (about 1 second or between 1000 and 2000 feet between Flash and BOOM) the EMP triped the ground fault detector in the surge guard.. Thanks to the 12 volt battery bank and an inverter it was like half an hour before I noticed an indicator NOT lit and went out (THe rain had seriously let up by then still misting but not downpour) Thanks to the 2000 watt inverter even the TV was till playing recorded video.. A quick off/on of the breaker and 2.x minutes later CLUNK lights brighter as the converters kicked in.,
Lwiddis
Explorer II
Mar 26, 2020
"Solar controller should be close to the battery. You will pull new wire direct from the controller to the battery terminals. Main battery ground wire to the frame remains connected."

Use 6 guage at least.
BFL13
Explorer II
Mar 26, 2020
When you also get your battery monitor such as a Trimetric it will have its 500a shunt for your negatives.

Now the battery to frame ground wire is disconnected from the battery and goes to the side of the shunt that has all the other neg wires, and one fat wire goes from the other end of the shunt to the battery.

That still has the battery neg grounded to the frame, but you get the info to the monitor by having the frame amps through the shunt.

With the inverter, converter, solar controller, and frame ground, all to the shunt, it will stack too many lug terminals under the shunt's bolt. So use a neg buss to collect the various neg inputs and then a fat wire to the shunt from the buss.
avarusbrightfyr
Explorer
Mar 26, 2020
time2roll wrote:
Solar controller should be close to the battery. You will pull new wire direct from the controller to the battery terminals. Main battery ground wire to the frame remains connected.

Gotcha. I've been researching solar setups in preparation for my eventual install, and couldn't remember how that connection worked. Thanks for the response.
avarusbrightfyr
Explorer
Mar 26, 2020
DrewE wrote:
The battery can be grounded to the frame wherever it's convenient to do so. With a solar controller, that doesn't need to change for any reason; the battery negative side of the controller can likewise be connected to a convenient chassis ground location (not necessarily the same one as the battery). The frame does provide a good, low-impedance path for the current, provided the connections to it are good and clean and tight. You'd be hard-pressed to create a better, lower-impedance connection with a wire in most cases.

Any halfway modern system will basically have the converter, the battery, and the DC fuse panel connected in parallel, ignoring the battery disconnect switch for the moment. This may be physicallly accomplished by having the converter connect to lugs on the DC distribution panel, basically making it be the junction point for all three, but electrically it's equivalent in theory. Others have the converter wired more or less directly to the battery lugs, or perhaps to some intermediate bus bar or other junction point. In any case, the converter does supply power not only to the battery but to the rest of the 12V system when plugged in, since they're all interconnected. A standard battery charger clamped to the battery would do the exact same thing, for the same reasons. You continue to have 12V power when unplugged simply because the battery is now carrying the load, and you have a working battery.

The specific details of what connects together physically and in what locations is somewhat more variable than the basic electrical setup. Fiddling around with those connection points is perfectly reasonable, provided of course you employ appropriate electrical safety practices, such as making sure sufficient overcurrent protection (fuses) are there for the circuits you reroute.

It is perhaps worth observing that modifying the converter connections may alter how the system behaves if the battery disconnect switch is used to disconnect the battery. If the converter is connected to the electric panel (or anywhere on that side of the switch), then it will power the 12V system when the battery is disconnected but not charge the battery. If it's on the battery side, then it would charge the battery but the 12V system for the RV would have no power. Neither one is especially desirable in most situations.

My converter is connected to the panel side of the battery disconnect. I have to switch of the disconnect and the AC main circuit breaker to stop power flow on the 12V side, which I figured out when I installed my vent fans last year.

I believe I might go with the suggestion of buying a separate converter and leaving the factory one in place. That way I can get an upgraded unit and I can just keep the factory one turned off...and avoid the extra wire routing for the automatic shutoff I want to try.
time2roll
Nomad
Mar 26, 2020
Solar controller should be close to the battery. You will pull new wire direct from the controller to the battery terminals. Main battery ground wire to the frame remains connected.

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Converter and Battery Question

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