Relocating Batteries

Nice install, but I agree on additional venting...I would have placed two of those vents, one close to the floor and one as high in the space as possible. As the hydrogen exits regular air needs to be able to come in.

climb.on wrote:

Question: Is rewiring the batteries in a new location, as simple as I think it is? Battery negative bonded to the frame and Battery Positive to the 2nd lug of on the charger/converter circuit board (see picture)? I would also add a battery disconnect near the new battery location, like we have up front.

I would not. I wouldd run a wire from the positive side of the battry to the positive side of the controller and a second wire from the negative side of the battery to the negative side of the controller. Running the negative through the frame like you suggest is just going to add resistance to the circuit and add additional possible points of failure. I would not be surprised if the negative battery terminal is currently run through the frame so the manufacture could save a buck fifty in wire but you are better off running it directly to the controler and since you are so close you might as well. There should already be a wire from the negative side of the controller to the frame so there is no need to add a second when you wire directly to the negative side of the controler.

Also, there are electrical component wiring (emergency brake, tongue jack,etc) at the old location on the tongue that I think will still operate as long as I leave the existing positive battery cable in tact. I will leave all the existing wiring to the front, in tact anyway, as to easily return to the original setup if desired and to keep power to the front junction box. Is there something I am forgetting to consider here?

It sounds like your conclusions are correct and you are not forgtting anything. Just make sure you insulate the current battery lugs well so they don't acidentally short out. Especially the current positive lug, you don't want it to acidentally short to the frame. Electrical tape should be sufficient for this.

myredracer wrote:

Some info.:

http://www.caravanandmotorhomebooks.com/articles/battery_enclosures.html

http://www.bdbatteries.com/hydrogenventing.php

http://www.yachtingmonthly.com/plus/530747/how-batteries-can-explode-and-how-to-avoid-it

Thermal runaway example

I just got back to doing some reading from the these sources - excellent info. Very informative. Thanks!

myredracer wrote:
That MTS Products sealed & vented battery box has an intake on the bottom.
I dunno... IMHO, you need to make ventilation improvements. Nice work otherwise!

Good to know - thanks! I didn't realize it these had a lower vent as well. Yup I agree, I need to add a vent in through the floor to get the appropriate cross ventilation. Will get that done asap.

That MTS Products sealed & vented battery box has an intake on the bottom. In fact, the upper and lower pieces are identical. Many FW trailers use this same MTS box and they all have the intake extended into the space below the front storage compartment and the exhaust vent is a foot or more above the top of the box. If that's what RV manufacturers do, that's what I would copy. I installed a vented & sealed battery box in our last TT, and after doing a lot of internet research, I ended up doing basically the same as what FW trailers do.

The exhaust vent should be min. 6" above the top of the sealed boxes. I can't find info. on the internet at the moment that discusses this but I have found it in the past. I don't see how hydrogen and air can flow out the single upper vent without an intake (in the correct location). If there is tech. info. on this on the internet from a credible source, I'd be interested in seeing it. Under some temp. conditions, the hydrogen will just sit inside the box so it's important to have the venting right.

It's also important to keep the battery compartment adequately vented and cooled so the batteries do not reach 100 degrees F for sustained periods otherwise the batteries can potentially overheat and go into thermal runaway with catastrophic consequences.

Some info.:

http://www.caravanandmotorhomebooks.com/articles/battery_enclosures.html

http://www.bdbatteries.com/hydrogenventing.php

http://www.yachtingmonthly.com/plus/530747/how-batteries-can-explode-and-how-to-avoid-it

Thermal runaway example

I dunno... IMHO, you need to make ventilation improvements. Nice work otherwise!

Aah, I didn't consider things snagging on the wing nuts. I also didn't notice the exterior door frame right next to the box. You should have no trouble standing outside and just reaching in and dragging the batteries out for service. I agree with you on them possibly not needing maintenance. My Costco 6 volts were built in 2009 and I've only ever added water once. And they really didn't need it, it just seemed like why not. :)

opnspaces wrote:
Interesting mod, I like it. Is there a way for fresh air to come in near the bottom as hydrogen exits near the top. Although I'm picturing the tornado inducing bathroom vent fan in my trailer. If I run the fan with all the doors and windows closed it creates a good suction. this could would possibly suck air into the trailer through a fresh air vent in the battery box and bring any fumes in with it.

Also have you thought about possibly adding some studs and wing nuts to hold the side of the box on? I'm just thinking that the easier it is to access the batteries the more likely it will be that they get inspected.
Link
They sell these at Home Depot in the drawers of specialty bolts in located in the nuts and bolts aisle.

I wonder if you can somehow make a sliding tray to make checking the batteries even easier. Maybe some drawer slides laying flat on the floor with a piece of 3/4 inch plywood mounted on top to act as a sliding floor.

I like the way you think! These are all good thoughts and things I had considered. The box is sealed and I don't feel like any suction from the fans will overcome the siliconed seams and weather stripping on the access panel. The camper is plenty "leaky" in a variety of other places :R

I only used one vent since that's all the manufactured "vented/sealed boxes" use, like this one. If it's adequate for them, I think it will be adequate for me.



I did consider the studs and wing nuts and I might still go that route, but I wanted the exterior of the box to be as clean as possible since I will pile stuff against the box and didn't want things to catch on the protruding wing nuts. I don't think I'll need to access the batteries all that often anyway. We'll see.

I also considered a drawer slide, but I am maxed out on height and I don't have the width. It would have required a much more significant retro fit to get that to work.

You can see that he has attached a gasket material to the carcass of the box, that will seal it real well. It looks almost like the adhesive backed weatherstripping I used for my box. The weatherstripping is a great sealing gasket.

My understanding is that if you have a vent to the exterior and it's located towards the top where the hydrogen could accumulate, the transfer to the outside will be taking place without a separate intake. I will probably install a separate, small intake in the lower part of my battery box but will cover it with a flap of soft rubber so that it can't ventilate to the cabin. Although I think it's unneeded for the hydrogen venting, it should exchange air better and allow for warmer cabin air to enter the box in Winter. A separate vent for entry air from the exterior would probably also increase the air transfer.

BTW, thanks for the link to the hanger bolts, I was just thinking about them, yesterday and had forgotten the exact name. Elegant idea about the sliding tray, too.

Interesting mod, I like it. Is there a way for fresh air to come in near the bottom as hydrogen exits near the top. Although I'm picturing the tornado inducing bathroom vent fan in my trailer. If I run the fan with all the doors and windows closed it creates a good suction. This could would possibly suck air into the trailer through a fresh air vent in the battery box and bring any fumes in with it.

Also have you thought about possibly adding some studs and wing nuts to hold the side of the box on? I'm just thinking that the easier it is to access the batteries the more likely it will be that they get inspected.
Link
They sell these at Home Depot in the drawers of specialty bolts in located in the nuts and bolts aisle.

I wonder if you can somehow make a sliding tray to make checking the batteries even easier. Maybe some drawer slides laying flat on the floor with a piece of 3/4 inch plywood mounted on top to act as a sliding floor.

westend wrote:
Nice job! All shrink-wrapped and even the Ground identified with a couple wraps, I really like that.

A word about hydrogen from the batteries: When I was building my battery box, I found that the hydrogen produced on a pair of 6V's is really not that much. I've forgotten the source but do remember that the amount was a lot less than what I presumed. As long as the vent is at the highest point of the enclosure, all should be safe.

Thanks! I read some similar information about the amount of gas produced. That combined with the fact that it is something that is done regularly (although not ideal) in the marine and occasionally in the RV industry I'm comfortable with it. This location allowed me to add an inverter very easily as well, which was an added bonus.