Technical Suggestions for mounting battery in trunk

Haven't had a battery mounted in the trunk for many, many years...looking for do and don't suggestions.
Battery will be against/near the passenger side wheel well, in a closed but unsealed box, solidly mounted to the floor, with insulators over the pos and neg posts, and battery mat in bottom of battery box. Will use 1.0 cables and good grounds.
Questions:
In general, trunks are much more sealed up than under hood mounts. What issues does this bring, if any?
I see some boxes are sealed and have vent tubes. What does this provide?
Any additional concern about battery acid odor?
Underside of trunk lid has a nice paint job...any concerns about corrosion?
Any other suggestions will be appreciated.

 

Vent tube should be run through a hole out side the vehicle or use a OT high tech non lead acid battery like AGM or spiral etc

 

I've had a battery in the trunk in my car for 48 years and have never had an issue. The battery is in a marine style plastic battery box. I have also placed an acid absorbing blanket under the battery inside the box in case it does leak. No acid odor or corrosion of any kind. Hope this helps.


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Sealed battery is a good idea. Drag racers are mounting them transverse to the car centerline ''so the plates don't short together under acceleration''. Wonder how hard you would have to leave for that to happen..

 

I still have not figured out a good reason to move a battery to the trunk...

btw the thing about venting a battery, is that when you charge a battery it produces hydrogen gas and oxygen gas, and in case you didn't know, you can cause those gases to explode, with just a little bit of effort. Batteries need to be vented!

 

Do yourself a favor and run both pos and neg cables to the engine. Grounding to the body can (and probably will) cause headaches in the future. Grounding to the frame works sometimes and sometimes not; probably depending on the quality of the workmanship.

For reasons not germaine to this conversation the battery in Clarence has been behind the passenger seat for over 25 years. Both cables are the same size and go all the way to the engine compartment. Never had a moment's problem in all that time.

 

It wasn't my first choice for the location, and not super happy about it either. But, as it turned out, we were able to get the engine in the Stude with only a little ball peening of one area of the firewall near the driver's side valve cover. The almost un-molested firewall looked so good to me that I decided not to mount the battery on it, and opted for the trunk location. The frame modifications on the car would have made it pretty tough to mount it under the body.

 

Vent it. Some say you don't have to vent AGM batteries but err on the side of caution sounds like a good idea. Oh, if you want to race, NHRA and most local track tech inspections require a visible external battery shut off switch on any car with a battery in the trunk.

 

I have three cars with the battery in the trunk on passenger side in marine plastic battery boxes. I use a cut off switch & welding cables on all pos & neg posts. Some are 6V & one is 12V. Some have been that way for 20 years. I like optima red top batteries. Wal-Mart carries the marine boxes in two sizes. I also use straps to hold them in place.

 

There are a few more rules about relocated batteries, if you want to go drag racing. 3/8" minimum diameter mounting bolts, steel or aluminum firewall between trunk and passenger compartment unless the battery is in a metal box, rear mounted cutoff switch (that kills the motor too) on any car that has a relocated battery.

If it's the only place you can put it, then go for it, but be careful, and be safe. A couple of my friends have had trunk mounted batteries explode. It's not fun.

 

I could not fit the AC compressor and large alternator with with the battery in the stock location.

Shock towers, the power steering pump, and the distributor precluded relocating it anywhere else in the engine bay.

 

heh...I've been known to do away with shock towers, power steering pumps, AC compressors, and large alternators.

I guess we have different priorities with small cars. And on large cars, it's not an issue.

 

Maybe weight over the rear tires, instead of the front end.

 

I suppose....???? I have a car that has been in the nines with the battery up front and 7" tread slicks.

 

Several modern cars run the battery in the trunk. My BMW 325i convertible has the battery in the trunk. I bet if you check other makes they do the same.


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Using a gel battery in the trunk should be fine if you have to move to the rear of your car. Use a circuit breaker or fused close to the battery. Maybe even think about a cut off switch by the battery. Its good for safety and theft deterrent..

 

The sealed boxes with vent tube bring legality if you are racing. Most newer sealed batteries don't out gas much so it shouldn't be an issue. But that is what the sealed boxes provide more than anything else is making you legal with most sanctioning bodies.

Remember keep your ground as short as possible and make sure that it is grounding.

 

Yes! And on the other side, I suggest keeping the positive cable to the starter energized only when cranking to prevent issues with a 10 or 12 foot constantly energized power lead. I used a ford style solenoid mounted by the battery in the trunk of my OT 442. AGM batt, vented steel porter cable battery box, 3/8th bolts through trunk floor, quick pull external disconnect, 1 gauge terminal cables, 4 gauge charging cable ran thorough a 80 amp breaker from one wire alt, battery grounded to frame, same as engine, trans and body.

I mounted the battery in the trunk for heat purposes, my Olds was cooking them at the track. Maybe due to the Aluminum heads, maybe the timing I have cranked into it, maybe the aluminum radiator and the close proximity to the battery...for whatever reason it was too hot. Moved it 4 years ago with zero issue since. No hot start issues either now due to remote solenoid.

I am using the same wiring method in my 34 roadster this winter as it is both effective and Personally proven.

 

Oh, here's a reminder. Last Friday after golf I was perched at my favorite watering hole when someone hollered that a truck was on fire in the parking lot. I was driving the afore mentioned Olds, since it is the only car I own big enough to still have room in the trunk for both a battery box and my golf clubs. Always secured to the side of the stainless battery box, to a metal plate I riveted on, is my trusty fire extinguisher with a 4" magnetic base so I don't have to mess with brackets in an emergency.

I put out the fire on the sweet little apache truck post haste. I was back to my roost and done with my drink before the fire truck showed up. This is on point as the apache had the battery behind the seat and a hot lead to the GM starter solenoid. Fire started there and spread to rubber vacuum hoses and insolation. SO...

Thinks to remember:
1. Always wire your rigs correctly or hire someone else to do it for you that knows what they are doing.
2. Never read shit on the internet and figure you know what you are doing
3. Always carry a chemical fire extinguisher and make sure it is charged and you know how to use it
4. Always buy a drink for the guy who saved your truck from burning to the ground...and offer to re-charge the extinguisher.

And if that pretty little aqua Apache belongs to one of you, see item 4 above and I'll be at the Prairie Tavern!

 

Good Luck Billy on getting the extinguisher refilled along
with your drink. You might be lucky enough to get a thank you note . MAYBE !!!
Jus remember KARMA

 

I used a boat battery box in the roadster and used welding cable for the positive and negative . HRP

 

Just don't tell early VW owners that their batteries are unsafe under that rear seat!!!!!
IMO smart / secure mounting and no smoking always helps!!

 

My wife had several New, from the factory, Cad's in the last 15 years and they had the battery under the back seat.

 

Hell I'll send you a drink and add to your list never assume that what you just read on the web is true.

I ran welding cable 00 on the Pusher and used an old printers box in the bed. The box isn't relevant for this thread I have used more than my share of marine boxes over the years no problems even with old batteries that probably needed external venting.

I ran a boat box behind the dog house on an Econoline with a souped 300 in it for over a year. No problems. They work just not NHRA legal in most apps.

 

My wife had a little foreign car that came OEM with the battery in the trunk...special battery, with a vent tube sticking out of it.

The OEMs understand the hazards, and take effort to make them safe. Take a close look at how they do it.

The truck on fire example is great...it shows how important this stuff is. Pay attention.

 

C3 shark Corvettes got the battery behind the driver's seat. That was probably driven by lack of space under the hood as much as anything. Shifting the 1-2% of the vehicle weight bias rearward ain't a bad thing.
Miata's and my daughter's 2008 Volvo have their batteries in the trunk OEM.

Porsche 356s from the 50s and 60s carry their batteries all the way forward in the nose I believe. Looks like a maximum weight re-distribution effort as much as a "where will it fit" kind of thing.

A couple of voltage drop while cranking tests would make it clear if cables are undersized, the body-as-ground is adequate (it should be) , connections are loose or corroded, etc, etc and etc

 

How can I forget her? You gots to watch that Karma chick, got a mean ass temper and she forgets nuttin. Used to date her (long legs, wick'd smile) but it was a terrible breakup, been paying fo it ever since.

 

RE:Hydrogen gas."Remember The Hindenberg".
Good luck.Have fun.Be safe.
Leo

 

I actually have had more then one bike battery that had a vent tube that could be run under the frame. Most older bikes you sit on the battery. We used to make jokes about getting hit in the junk with a piston but getting your arse blown off by a battery was probably more likely. Hydrogen is really gnarly stuff. I am not sure how they work a modern battery, some are sealed up pretty tight.

I never dated her but I did sleep with her homley step sister once and she is still mad about that.

 

AGM is the way to go regardless of battery location if you can afford one. "Absorbed Gas Mat" they are sealed, require no venting though I still prefer to do so. They also weigh next to nothing and have big CCA numbers. Price is dropping on them all the time and their performance keeps increasing.