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Old 05-19-2012, 11:25 AM   #1
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Do multiple batteries need multiple meters?

Hi all, I'm converting my Chevy Express van into a class B camper. I'm in the process of figuring out my power options. I plan on starting with two 12 volt deep cycles in parallel and have a few questions for the more experienced to make sure I'm on the right track.

First, do I need a separate volt meter for each battery or will just one on the lead battery give me an accurate reading of the battery status?

Next, the only load on the batteries will be the mini fridge and some lighting. Will a directly wired inverter be appropriate? I'm thinking a 1,000 watt should be sufficient?

I also plan on hooking up a maintainer/charger to them to charge them while at the campground.

There is no room at all under the van to mount these batteries, so I've devised a sealed compartment in the back by the rear door with a hole cut in the door to vent the compartment to the outside. Will I need to drill a hole and run the ground wire out to a part of the frame or will mounting it to the sheet metal under the floor suffice?

Have I overlooked anything or am I completely off the wall? I got these ideas based on my friends class C and a few class B's I was looking at.

Any info, suggestions and tips would be greatly appreciated!

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Old 05-19-2012, 11:42 AM   #2
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Two batteries wired in parallel act as one battery. A meter wired to one will give the average voltage of both. Unless you disconnect the batteries from each other, two meters wouldn't show anything different.
As to the ground, perhaps bolt ground wire to sheet metal, then a second ground wire from the bottom of that bolt to the chassis will insure a solid ground. Many issues start with a poor ground connection.
Be sure to have sufficient ventilation for the batteries to outgas, even if you use 'sealed' batteries. Also make sure inverter is in a ventilated space for heat dissipation.

Good luck with your project!


Bob & Donna
'98 Gulf Stream Sun Voyager DP being pushed by a '00 Beetle TDI
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Old 05-19-2012, 11:50 AM   #3
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BFlinn, thanks for the quick reply and great idea for the ground. I like it!
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Old 05-19-2012, 12:25 PM   #4
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battery ventilation

Walmart sells battery boxes with closed lids and a ventilation fitting for rubber hose to the outside. Also make sure the outside vent hose is higher than the battery box lid. Gas rises....If using Walmart boxes you can drill holes, connecting them side by side or end to end, with bolts and connect the cables battery to battery completely inside the boxes. Two more bolts thru one of the boxes for power distribution. Be sure to fasten the boxes down.
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Old 05-20-2012, 04:48 PM   #5
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With two batteries in parallel you have one battery electrically/electronically.

With two six volt in series you likely have a fatter wallet (Due to lower cost for the batteries) , more amp hours (220-230 at the 20 hour rate). and one 12 volt battery. (Equivlent)

When it's hooked up, it does not matter how you do it, you have ONE 12 volt battery. May be made up of several parts, but it is still (And this time I will properly id it) one 12 volt battery bank.

Thus one meter.
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Old 05-20-2012, 08:29 PM   #6
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I agree with wa8xym, 2 -6 volt GC batteries wired in series will be more economical then 2 large 12 volt batteries wired in parallel.

Yes on the direct wired inverter, wire it with 2 gauge or better battery cables close to the battery bank.

Think carefully about the size inverter you want to install. The larger the inverter you install, there is a possibility of quickly draining amps from your battery bank by accident.

I installed a 600 watt Prowatt inverter which seems to work well with my limited battery bank of 375 ah. Sometimes I wish I had installed a 1000 watt model to handle the microwave, but even without using the mw my battery bank usually runs to 12.2 volts overnight. I am not very good at conserving power so it all works out in the end.

Since you probably have far fewer items to run with the inverter, using a larger 1000 watt may be okay. Just remember that if you use it continuously near it's rated capacity, your batteries will need to be recharged after about an hour of use. 1000 watts will draw about 85 ah from your battery bank at full load, or appx 8.5 amps per 100 watts of use.

Look for an inverter with high optimum efficiency (90% or higher) and low no load current draw (less then < .6 A)
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Old 05-20-2012, 11:18 PM   #7
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I agree that two 6 volts in series are better than two 12 volts in parallel. If you use two 12s, make sure to connect the positive terminal from battery 1 to your load and the negative terminal from battery 2 to ground. That way you will use equally from both batteries. If you connect positive from battery 1 to load and negative from battery 1 to ground the result will be overusing battery 1 and under using battery 2.
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Old 05-21-2012, 03:09 PM   #8
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NOTE: I did not say two six volt in series is better than two 12's in parallel.

I said they cost less.

To make the math easy I will round a bit and call 2 sixes 200 amp hours (They are 220-230 depending on who made 'em)

You can get there easily with a pair of 12 volt deep cycle batteries (NOTE: Marine/Deep cycle are STARTING batteries, not Deep cycle)

And 200 amp hours is 200 amp hours.

But where as the two 12's needed will set you back over 100 bucks EACH

The two sixes are closer to 70 bucks each.

Home is where I park it!
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