Added a second battery and made a custom switch box

howlin4you · 06-12-2016, 09:17 PM

Over the weekend I ditched the Interstate HD24-DP the dealer installed and put in two 12 volt true deep cycle batteries. I wanted a way to switch between them and be able to monitor voltage of each independently so I made a custom switch box with voltmeters built in. I used a marine 4-way battery switch, waterproof voltmeters, a small SPST momentary switch, and a project box. I thought it turned out really well so I wanted to show it off.

I also took the time to rotate my tongue jack 90 degrees so I can open my tailgate.

There's a small push button switch on the forward side of the box you press to read the voltages. For whatever reason they wouldn't show up correctly in a photo but you get the idea.

**Mustang65** · 06-13-2016, 06:50 AM

I like it!!!! Very nice

Don

RoyBraddy · 06-13-2016, 08:29 AM

We used the BLUE SEA four position Switches here as well... They are super sealed high DC current rated switches...

I mounted three of that same switch you have on the trailer frame area just behind the tongue area. I have a setup for four 12VDC batteries. I am setup now to use all four batteries, or three, or two , or one or NONE haha...

Like your Blue Sea small round VOLTMETERS haha... Your readings sure caught my eye however. Those readings shown sure are a long way from 12.6-7VDC haha...

Roy Ken

Camper_bob · 06-13-2016, 08:35 AM

Nice Setup!

Questions: For charging purposes; would you have to manually switch the batts over while the coach is plugged in to get the batteries to charge? (Would you have to charge them one at a time?) Is the "1+2" position functional?

howlin4you · 06-13-2016, 08:47 AM

Quote:

Originally Posted by RoyBraddy

Your readings sure caught my eye however. Those readings shown sure are a long way from 12.6-7VDC haha...

For some reason the display on the voltmeters wouldn't photograph well. They were actually showing 12.9 or 12.8 volts when that picture was taken.

howlin4you · 06-13-2016, 08:52 AM

Quote:

Originally Posted by Camper_bob

Nice Setup!

Questions: For charging purposes; would you have to manually switch the batts over while the coach is plugged in to get the batteries to charge? (Would you have to charge them one at a time?) Is the "1+2" position functional?

The 1+2 position is functional and when selected will allow the trailer converter to charge both batteries at once. However, if one battery was discharged and the other fully charged I would probably avoid that. In that case you would have to manually switch it. I plan on charging both separately with an external charger prior to a trip, using one battery until it drops to 12.0 volts, then switching to the other. We only boondock for 4 or 5 nights at the most (usually only 2 or 3) so this set up should be more the adequate.

**Mustang65** · 06-13-2016, 11:44 AM

Just asking everyone why ? ...

I find it hard to understand why when you have (2) 12Volt batteries we install a switch to run one battery at a time? The way to look at is like you have 2 gallons of water, you hook them together with a connector valve to allow you to drain one gallon and then flip the valve and drain the other. You still only have 2 gallons to work with. No more than hooking the 2 gallons of water together with one output.. still only 2 gallons.

The same for batteries if you have (2) 100Ah 12volt batteries in parallel = 200Ah, but of the 200Ah you can only use 100Ah due to the 50% rule, so why run one battery down to the 50 Ah level (12.1Volts) and then switch to the other battery where you will use the other 50Ah.

If you use them together 100Ah, you are going to get the same amount of output as running them one at a time. You then have 2 batteries that are not at the same level of charge, so you can not charge them together and have to charge them individually, where as if you leave them together you recharge them together.. the Ah used is the same across the 2 batteries so the charge time will be the same.

The odds are that the 2 batteries (in the long run) will not get the same usage and one will age faster than the other.

I do realize that it is a disconnect switch also, and maybe that is the main intent..

Just wondering

Don

howlin4you · 06-13-2016, 12:04 PM

Don, I see where you are coming from and you're right the capacity is the same whether we use use the batteries one at a time or together. The main reason I want to do it this way (and also one of the reasons I opted to not go with two 6 volt GC-2's) is that when I run down the first battery I want to be able to switch to a second fresh battery, remove the first one for charging, and still have a functional trailer. Say it takes me 3 nights to deplete battery 1, I then switch to battery 2 and figure I have 3 more nights to figure out how to charge battery 1. I carry a battery charger with me and can always try and find somewhere to plug it in (an empty electric site or a shower building, or at least the 115v outlet in the truck). This way I have time to investigate options and if I can find an outlet for a few hours I can go indefinitely and never not have power in the trailer. If I have two 6 volts or two dead 12 volts now I HAVE to get them charged right away or we have no power. It also provides me peace of mind while on the first battery that we always have that fresh one to run the slide out, awning, and tongue jack.

Most of the time this shouldn't be an issue because we probably won't even boondock long enough to bother with charging the first battery. I just like the idea of being able to swap between them and never having a dead trailer. As far as the issue of aging, I never plan to run them together anyway so it doesn't matter.

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