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 > Converter and Battery Question

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avarusbrightfyre

San Diego

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Posted: 03/26/20 09:06am Link  |  Quote  |  Print  |  Notify Moderator

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!


2019 34' Minnie Plus Travel Trailer
San Diego, CA


2oldman

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Posted: 03/26/20 09:32am Link  |  Quote  |  Print  |  Notify Moderator

Your inverter should have both its wires connected directly to the battery.

BFL13

Victoria, BC

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Posted: 03/26/20 09:32am Link  |  Quote  |  Print  |  Notify Moderator

The battery neg wire to frame still goes to the frame. The neg wire from the solar controller goes to the battery.

When the converter is unplugged you still get 12v from the battery. The converter only works if you have 120v from shore power or generator. (it also works from the inverter, but you don't want it to or you get that infamous "loop")

You can just buy a deck mount converter and put it up with the inverter and battery bank and leave the original converter where it is. No big wiring job. Put the controller in there too.

The battery bank needs a vented box because you don't want the inverter and converter to get ruined by battery fumes or the fumes to get a spark from the inverter. AGMs get around all that.


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DrewE

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Posted: 03/26/20 09:39am Link  |  Quote  |  Print  |  Notify Moderator

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.





avarusbrightfyre

San Diego

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Posted: 03/26/20 09:55am Link  |  Quote  |  Print  |  Notify Moderator

BFL13 wrote:

The battery neg wire to frame still goes to the frame. The neg wire from the solar controller goes to the battery.

When the converter is unplugged you still get 12v from the battery. The converter only works if you have 120v from shore power or generator. (it also works from the inverter, but you don't want it to or you get that infamous "loop")

You can just buy a deck mount converter and put it up with the inverter and battery bank and leave the original converter where it is. No big wiring job. Put the controller in there too.

The battery bank needs a vented box because you don't want the inverter and converter to get ruined by battery fumes or the fumes to get a spark from the inverter. AGMs get around all that.


Good to know. I plan on either AGM or LifePo4 drop in equivalents at this point for the batteries.

time2roll

Southern California

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Posted: 03/26/20 09:57am Link  |  Quote  |  Print  |  Notify Moderator

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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avarusbrightfyre

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Posted: 03/26/20 10:01am Link  |  Quote  |  Print  |  Notify Moderator

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.

avarusbrightfyre

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Posted: 03/26/20 10:02am Link  |  Quote  |  Print  |  Notify Moderator

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.

BFL13

Victoria, BC

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Posted: 03/26/20 10:26am Link  |  Quote  |  Print  |  Notify Moderator

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.

Lwiddis

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Posted: 03/26/20 11:38am Link  |  Quote  |  Print  |  Notify Moderator

"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.


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