2nd Battery/7-way connector

[wbrownrr]

Is it possible to add a 2nd battery to my 2002 22' CCD through the 7-way connector at the front of the trailer? I'd like to simply buy a 7-way plug like the one on the tow vehicle, attach that to the new battery pos. and neg. terminals, place a 20a fuse in the positive line, and plug that into the AS 7-way connector. Then, when dry camping, I can place the 2nd battery on the ground and plug it in. Isn't this just the same as providing dc like the charge line does from the tow vehicle?

I've got a 120w watt solar panel which, I hope, will then charge both batteries. This seems much simpler than welding a new bracket for two batteries onto the AS tongue, which would be required to add a 2nd battery to the trailer.

Has anyone added a battery this way? Let me know what you think.

[markdoane]

That sounds like it would work, but you should add a knife switch to your existing battery. Otherwise the 2nd battery will go dead trying to charge the first battery.

You can use a battery isolator if you can get enough voltage out of the solar panel. The isolator will cost you about a half a volt.

[wbrownrr]

Why would I need the knife switch? Wouldn't the batteries be wired in parallel, with both charging and discharging at the same rate?

[markdoane]

If you always have them parallel, and they are the same construction, that's true. But you will be using the first battery while on the road, or at rest stops, so it will always have less charge than the 2nd battery.

So when you get to your campsite and unload the 2nd battery and plug it in, it will have a higher charge and try to equalize with the first battery.

It could work, as long as you are aware of the limitations.

[wbrownrr]

I see your point. But, the first battery will charge while on the road, either through the solar charger, the T/V charge line, or both. So, actually, the second battery will sometimes have LESS charge. This will probably shorten the life of both batteries. I'm curious if anyone has tried this before.

[uwe]

I would opt for the bracket modification, and have identical batteries mounted to the coach. I imagine you would soon tire of dragging the battery in and out, and making the connections etc.etc.

In addition, the 7-way plug can not transfer high amperage currents, which might want to flow when yor coach battery is depleted and you hook up the second battery, especially when 12V items are running inside the trailer.
A better way to connect a second battery temporarily would be a welding connector and some 6G battery cable.
The danger would be to potentially burn up your trailer connector, causing undue repairs, and a ruined camping trip.

[wbrownrr]

Thanks for the feedback.... I'm beginning to wonder if it was such a good idea after all. I'm most concerned about the differences in usage/charging between the two batteries. If I put a 20amp fuse in the connection, I could pretty much avoid any damage to the connector/pigtail... However, I can't help but wonder how much the life of both batteries would be shortened because they would sometimes be at different levels of charge.

[Silvertwinkie]

You know as I read this post, I was thinking exactly what Uwe had said, then I read Uwe's post.

I agree 110% with Uwe's comments.

[john hd]

wbrownrr

if you really really want to do this go find some heavy welding cable, something like 2/0. and a forklift quick disconnect.

wire the two batteries directly in parallel with the quick disconnect, leaving your umbilical cord out of the picture!

when you pull the plug on the spare you can just leave the connector on the tounge of the trailer. secured of course!

automotive electrical or snowplow suppliers should have the parts you need.

john