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Trunk Mount Battery 1939 Chev

3K views 20 replies 13 participants last post by  tazhog 
#1 ·
Greetings Fellow Hotrodders,

I have a '39 Chev with a fairly aggressive 350 in it, and currently the battery is under the hood, but due to space, heat, (headers) and maintenance issues, I have been advised to move the battery to the trunk. My questions are these: in the past I have been warned that the hydrogen given off by the battery will eat the lead seams if the battery is in the trunk. Any advice on this? In order to prevent this, I have purchased a Moroso Sealed Battery Box, P/N 74051, but this box is anything but sealed. Each tie down screw (6) leaks badly and none of the included grommets fit well, albeit, there is a vent tube to vent outside the trunk. Any advice, comments, experience, along these lines would be greatly appreciated.

Thanks in advance for your help!

PS The Chev was my Dad's first car which he sold in 1951, but I found in a field and hotrodded it so I would like to keep the car long term - don't want to risk damage from the trunk battery if that may be a factor.
 
#3 ·
Thanks! I am not sure what an AGM type battery is. I currently have a 'sealed' battery - meaning no maintenance - but is that adequate, especially in the Moroso box even if the box is not really air tight? Have you heard of the lead seams being compromised by a trunk battery?

Thanks again for your help!

Diode Dan.
 
#4 ·
I installed an Optima battery (AGM) in my 48 Plymouth trunk, and I had some concerns about hydrogen gas build-up. Supposedly, the Optima will not offgas, but just in case, I fabricated a vent manifold with CPVC pipe, and a flexible hose that vents to the outside of the trunk. The manifold is epoxied (JB Weld) to the vent/relief ports on the Optima. All seems to be well so far, as I haven't blown the trunk lid off yet.:thumbup:
 

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#6 ·
Thanks to all who gave advice. My greatest concern with this is that I have been told that hydrogen gas eats the lead seams of these old cars, doing damage that may not be reparable. Has anyone heard of this, particularly over the long haul?

Again, thanks in advance for any answers/help!

Diode Dan.
 
#7 ·
Never heard of that one, I've only have ever been concerned by a potential explosive atmosphere. My BMWs have batteries, in the trunk, with vents from the factory, They are not in sealed boxes etc....... Works well. I wouldn't worry too much, if it is a vented battery (not sealed, maintenance free) and the vent tube is run outside the vehicle, battery box optional.

If you don't have a vented battery, a sealed battery box vented to the outside would accomplish the same thing, but now there might be a acid fume thing on the inside of your box.
 
#8 ·
Arn't those Optimas dry cells? No acid.....no fumes....I've seen them installed upside down,sideways,etc...
Your main concern when mounting the battery in the trunk should be: NOT having a hot (at all times) wire going from the battery to the starter lug, by using a solenoid its only hot when your starting it. like a ford.
 
#9 ·
I dumped my Moroso battery box in favor of a Summit one.

It is vented with a nylon tube out the bottom of the car, wasps tend to block it with their eggs.



I think it would withstand more abuse than a plastic one.

I have it bolted to a support which is bolted into the car, hard to bolt the plastic one down really firmly.
 
#10 ·
As I understand it, the Optimas have a gel type electrolyte, rather than liquid. And as you stated, I use a Ford style solenoid in the trunk that energizes only when starting. I have a separate #2 AWG cable from the alternator to the trunk mounted battery for charging. That cable is protected by 100A circuit breakers (one under the hood, and one in the trunk).
 
#11 ·
Thanks to all for the helpful information! After considering the Ford solenoid in the trunk to deactivate the high current wire to the trunk, I have decided on another course of action. I have run the 2 gage wire inside a rubber heater hose, so the possibility of any type of accidental grounding of the +12 high current wire is very, very low. This allows me to retain all the original (not stock for '39 Chev!) wiring and eliminates the extra wiring and points of failure to the trunk. Anyone else use this approach?

Again, many thanks to all who have helped!

Dan.
 
#15 · (Edited)
There are many ways to skin a Cat (and many ways that people disagree on how that Cat should be skinned :rolleyes:), however I like some of the out-of-the Box thinking going on in this Thread-

I had the same issues-my Car had the Battery under the Driver's feet (originally), and that space is now taken by my Master Cylinder/Booster, so I agonized on where to put it-my Trunk is polished Aluminum (I didn't want it there), so I was going to make a Box to fit in between my rear Wheel Tubs inside the Car (it is a Business Coupe, so there is a good sized area behind the Seats that isn't being used)-

My Wife is into Storage Sales (I could write a Book about that, it's pretty interesting), and, I was up at her Building looking at all the stuff that she had purchased, and here sits a Navy Ship Box that reads "Sonar Equipment" on it-it was hell bent for stout (and full of Military memorabilia) but it was a perfect size and fit in my Car-

So, I purchased the Moroso Box (and vented it outside) and put it in that Box-it does double duty in that I have also put a rear Fuse Panel in it (that handles my Fuel Pump, Fuel Pump Controller and rear accessories), along with my E-Stopp Parking brake, and I still have storage for cleaning supplies and Tools-:cool:

Now, as for the Battery Cables-I understand the theory behind the Ford Solenoid, but I was taught that anytime an energized wire goes through a metal "Firewall" that you should not only use a Grommet, but it should be fused as well, so, I used 1/0 Cable along with two 200 Amp Rockford Fosgate Circuit Breakers (in Series-400 Amps) to fuse it-
 

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#19 ·
Now, as for the Battery Cables-I understand the theory behind the Ford Solenoid, but I was taught that anytime an energized wire goes through a metal "Firewall" that you should not only use a Grommet, but it should be fused as well, so, I used 1/0 Cable along with two 200 Amp Rockford Fosgate Circuit Breakers (in Series-400 Amps) to fuse it-

Excuse me but 2 200 amp fuses in series is still 200 amps. You need to have the fuses in parallel to get the required current. In a series circuit all the current runs through the fuses one after the other.

In a parallel circuit you have current in 2 paths so you in effect double the fuse rating.

Just sayin,
 
#16 ·
Thanks! I, too thought about mounting the battery under the passenger front fender, but eventually decided not to as it would be difficult to access, and here in the North West, we get rain - not that I drive every day in the rain, but do get caught in it sometimes. I share your concern about a high amp +12 cable going through a body panel but have mitigated the risk by using a traditional grommet as well as running the cable through a heater hose, (actually the full length of the cable) giving it an additional layer of extra thick insulation. A breaker is a good idea, but it has to be so high an amperage that I am not sure of the protection it would offer. Your '38 looks great; I appreciate your information!

Diode Dan.
 
#18 ·
its all unneccesary ,all you need is a solenoid , the primary wire going to the starter is never hot ,only when starting.... the fuse or breaker is only needed on the secondary circuit ,both (solenoid and breaker/fuse) should be as close to the battery as possible
I ran my starter wire (welding cable) inside the frame
 
#17 ·
I have a '39 Chevy also and put a regular battery in the trunk. I use a regular battery because they are lots cheaper and the car is not a daily driver. Batteries usually last me 4+ years and require little attention with clean up about once every 6-8 months. I build a battery holder out of 1 1/2" angle iron, paint it with rubber paint and line it with firehose. Hold down is all thread. Not real easy on the eye so I build a quick removable box and try to make it look like luggage. Run two welding cables (pos and neg) up to the starter with a jumper to the frame and body. Never have had problems with lack of cranking power.
 

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#20 ·
Do it anyway you wish but for the life of me I can't figure out why it's necessary. There are hundreds of thousands of trucks that have long runs of battery cables and they seem to work just fine.

Now I do have a manual master disconnect 70 amp circuit breaker that disconnects all my electrical system except the battery to starter cable..... but that's because the car sits for extended periods and it keeps the battery from going flat.

There are a few other cases it may be necessary, but IMO a long well protected cable is just as safe as a short unprotected one
 
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