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Discussion Starter #1
On my progress to my camper van conversion I needed to add a 2nd battery for accessories so that my primary battery would avoid a drain. After many measurements and checking I confirmed a 34/78 battery would likely fit and then found a battery box that would fit under the front seat and avoid any interference. I decided on the optima yellow top because it sealed ($220), Taylor box which was the only one I could find that was small enough $100, and Battery Doctor $70 that I used before that provided simple "smart" isolation as well as the ability to combine or isolate the secondary battery. Wasn't the cheapest set up but it's reliable. Because the battery is so close to the primary you can use aftermarket battery cables from any auto store to make connections and simply just have to add a fuse to the + cable from primary to secondary.


Triple checking the mount location, I decided to use simple straps which will secure the battery at the end. Makes install easy, and removal of battery easy if I need to remove it.

You will have to remove the seat (6 bolts) and disconnect the airbag and seat sensors so you can remove the entire seat off. This is the picture of the two electronic connections you have to disconnect to completely remove the seat.

Make sure you fuse the + line from primary to secondary. Safety is key. I purchase a 150 amp fuse on ebay and some ends I spliced to connect to the fuse box.

Here you can see all the connections. The Battery Doctor is super easy wiring. + line from primary to Battery Doctor, + fused line from Battery Doctor to secondary, - ground line from secondary to chassis, and a - ground wire from battery doctor. Super simple diagram available on their website. I used 4 gauge battery cables from pep boys-colored tape was used to identify positive and ground, ran out of red tape so I used white, just wrapped for identification.

The secondary battery vent hose can be plumbed to the stock location with the other battery vent.

Picture of the battery doctor, I mounted this just front of the battery under the seat so I can easily control it and push a button to jump or see the monitoring.


You can see battery doctor and wiring here to battery

Picture before seats and straps go on

I used simple straps that I ran through the "seat frame" similar to how you would mount a boat battery. No way this is going anywhere and it allows easy removal of battery. Nothing interferes with the position of battery and it isn't gong anywhere. You cannot remove battery w/o removing top of seat, so its super secure. You can drill and mount into floor or frame...gas tank is directly below the seat so really this is the best option. The box is vented and the use of a sealed battery makes this a safest set up w/o putting battery on outside of van which there is no place to do anyways.
 

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Discussion Starter #3
Parts List as this may help give an idea what is needed:
Part Cost: around $450
About 3-6 hour project, difficulty moderate, some special tools for seat bolts (STAR BOLT), otherwise basic hand tools,drill (one hole for Isolator), and saw to cut long bolts.

Taylor 48200 Taylor Aluminum Battery Box - JEGS $100 (seems expensive but a nice kit and you can't find a cheap plastic box that will fit- I tried. This is a very nice box, worth the $)
WirthCo 20092 Battery Doctor 125 Amp/150 Amp Battery Isolator,- Amazon $70

DB Link 0/2/4 Gauge Ga ANL Fuse Holder + 150 Amp ANL Fuses (2 Pack)-Amazon $15
Scosche ERTC4-4 4 Gauge Ring Terminals - 4 Pack-Amazon $6

Optima YellowTop 8014-045 D34/78 - Autozone $200 w/ online discount

Cargo Straps Home Depot $8

Zip Ties $5 pack
3 Battery Cables, 4 gauge- Pep Boys $30 (19", 32", 32") -

few small screws to secure battery doctor and some colored tape as I used ground cables
 

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Nice job, GREAT write up!

A few questions,

Why yellow top over light grey blue top?

Did you think about mounting on its side? I was thinking about doing that and not using a case. As long as it is strapped in well, it seems like the box is not needed.

just wondering...

Ed
 

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Discussion Starter #9
Thanks for the comments, I am glad others find this helpful. My contribution as payback from all the great information I received from others whom post helpful info!

The seat is in it's lowest position - no clearance issues at all. I am surprised no one did this before me to be honest, took a long time for me to make sure it fit, wasn't totally sure at first.

I went with the yellow top rather than the blue because it suited my purpose and I thought I may want to use the side connections. This battery was recommended for aux purposes and RV use and sealed so it was perfect even though Optima quality I think went down somewhat. I purchased it from an authorized dealer so the warranty would be very good just in case. I did not want to mount sideways...just to be extra safe, even though it would be ok, but in a box this cannot be done.

I would not put a battery in your van w/o a box-for me it's a safety issue, do it right or don't do it at all, but you certainly can just put a battery under there, but for $100 more why not do it the right way to keep it as safe as possible? My family is in this van so safety is first and foremost and I don't like doing anything half way. It's in a box, it's vented, and mounted so there is no way its going anywhere even in a roll over. This is not a cheap modification, so why take shortcuts for safety sake. There is a reason NHRA required batteries to be in a box.
 

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Discussion Starter #10
One more safety thing I could think of since the battery could not be mounted into the frame there is a small chance in a very bad accident the terminals could contact the outside of the box. Ideally you could cover the battery connections inside the box so if the battery for some reason contacts the box there would be no chance of a short/spark. The battery is fused, so if this did happen it would blow fuse and disconnect from primary though. I am likely to cover the terminals once I hook up the accessories when the camper top conversion is done next month. Ideally this box would be mounted to a frame, this was just not possible given it's sitting right above the gas tank. In the perfect world you would weld a mounting plate to the seat frame...this would be perfect and meet all safety standards.
 

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I think I would only use a battery with screw terminals rather than typical clamp on battery cable studs in this configuration.
 

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Discussion Starter #13
I did not use screw mounts because the openings/grommets on this box would mean the cables would have to bend a lot to make the connection otherwise I might have gone that direction. (I did explore this first) Certainly wasn't because it would be more difficult mounting. If I did use the side screw mounts I would have had to drill new holes and plug the old ones in the box, the openings in the Taylor box aligned perfectly the the clamp on mounts. I like the screw ones myself also, or you can buy a marine battery and use the top screw mounts but they have a post that "sticks up" also, so defeats the purpose of a flush side mount. Just my experience in this situation. Either way lots of options, this thread I thought would be most helpful just so others know what would fit under the seat so that a battery would not take up any floor space. Normally this is the perfect spot for a huge amplifier for a sound system. :)
 

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Any report on how well the isolator you've installed is working?

Thinking about the metal box, could you fit a rectangular piece of plywood in the cover so that if the box was damaged, the terminals would be insulated from the metal? Just thinking inside the box...
 

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Discussion Starter #16
I used two of these isolators and relied on the many reviews on line for them so no personal feedback. They are pretty popular brand and very simple which is why I liked them to begin with.

You could line the box...or just cover the terminals with covers and would do the same thing. battery is clamped in and doesn't move at all in the box. It's bolted to the bottom of the box. You would have to have a very bad accident for the box to get bent to touch the terminals, the battery is pretty secure. The seat would have to get crushed on battery, or the battery/box moved so hard it crushes the box-for a racing application this should be welded in, but this is more than secure enough I believe. It's more secure than my battery on my boat and that thing bounces all over the place and I have no issues. My boat gave me the idea to mount with the straps.
 

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Thanks for this tutorial. I am thinking I need to do this. Please correct me if I am wrong- I would run the inverter the the aux battery to power any additional items such as a tv/printer etc?
I hate the fact that when I use my printer several times a day, it shuts off when I start the engine or shut off the engine for awhile- then I have to wait for it to cycle to restart. Also, if someone is watching a movie, it's inconvenient to have to restart it after running into a store or getting gas, I'd much rather hit pause. In this case, everything could be left "on" in a standby mode and never drain my starting battery- right?
 

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Discussion Starter #18
Correct, your devices are hooked up the the AUX battery power, so if anything drains it would be "isolated" from your starter battery, that's the primary purpose of the battery doctor - isolates the battery as well as option to "link" the batteries together in case you need a jump or something, and prioritizes the charging. Many manufactures make this type of device, I used this brand because it was reasonably priced, good reviews, super simple to hook up, and easy to use.
 

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Great information and pictures. I installed my second battery and my inverter similar to yours. Are you having any reception problems when your engine is now running. I have noticed decreased reception on the FM stations when my engine runs since I installed this. When the engine is off, I get great reception. Anyone else having this problem?
 

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Question on removing the seat

When you removed the seat did you have to disconnect the main battery for safety of not setting the airbag off?
 
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