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MG MGA - Special request: Coming from twin 6 volt batteries

I spend most of my time in the TD-TF discussions, popping over to the MGA side only to track down information for my fatherís 1960 MGA. As Dad nears his 92nd birthday, jaunts in his MGA, now with me behind the wheel, may be nearing an end. Earlier this month I tried to set-up his MGA for the summer, only to discover the twin 6 volt Diehard batteries were way low on water and, after filling, would not hold a charge. The battery compartments are as original. I measured 7Ē wide and 7 ľĒ deep.

Iím looking for the easiest, realistic way to get the MGA on the road. Unless Iíve missed a source, the few options I can still find for 6 volt batteries are so expensive that they are only appropriate for a show car. No single 12 volt battery is small enough to fit in the original compartment. I donít live very close to my father and I donít weld. If I canít find a battery that fits the existing compartment, the only option I envision is to build a shelf to accommodate a larger 12 volt battery.

I can fabricate the shelf and track down the battery more local to me. This is where I would appreciate some guidance (shelf plans? battery recommendation? other options?).

Iím open to any suggestions that can put the MGA on the road with the least amount of fuss. Thanks for your indulgence with another battery question.

Larry
Larry Shoer

Larry, I've used single 12v batteries in my "A" since I got the car running some 30 years ago; started with Diehards and then I switch to an Optima Red Top several years ago (the car does sit for extended periods of time). All batteries fit neatly into the passenger side battery tray without modification. Only thing I did was to add a 3/4 piece of plywood under the battery to give it a bit more height. Hope this helps.
N Kopernik

From the appearance of the Optima Red battery on the manufacturer website, the battery terminals would be arranged so that one terminal would be to the front of the car and the other terminal to the rear (in the 9.34" battery length). I assume there is room for this.

Would a battery box be a good way to extend the battery tray and provide a battery hold-down mechanism?

Thanks.

Larry
Larry Shoer

Larry - Whatever battery you get, also get a Battery Tender or one of the other brands of a battery conditioner and keep it hooked up to the battery whenever the car is not in use (I rigged up a socket and plug for the Battery Tender that I use on the TD to make it easier to hook up the Battery Tender). A battery conditioner will cycle the battery up an down to keep it at optimum charge and keep the plates from developing a sulphate coating on the plates. Cheers - Dave
David DuBois

Larry,
I have run a single 12v battery in my car since I bought it in 1972. The 6v battery tray is too short for a 12v but not that difficult to modify with a bit of hacksawing. You can fabricate an extension with some steel, stainless, or aluminum angle and pop rivets. A hold-down can be made from threaded rod and and a piece of angle across the battery top. Not sure which size of 12v battery fits best but I think you will find that info if you check the BBS archive. Alternatively, you can put a piece of plywood under the battery to raise it above the rear lip of the 6v tray but must be careful then that the terminals don't touch the cover or body shelf.
Tom Heath

Larry, the Optima battery is bought is a model 75/25; 910 CA; 720CCA; and 90 amp reserve. This battery is pricy, but I believed the features more than made up for the cost. One of these was the fairly deep reserve charge so I could go months without starting the car (more than 6 at one point) or having to charge it. The plywood under the battery lifts it to a good height to make easy battery connections, but not too high to hit the frame crossover or the cover; it also extends a bit beyond the existing compartment to provide more of a base for the battery. The hold down is a universal one, with the battery crossover being plastic and held down by 2 "j" bolts which were shorted to fit properly and connect to the sides of the existing battery tray. Hope this helps.

Nick
N Kopernik

My father would be none too pleased if I took a hacksaw to his MGA--for any reason!

I'll look at building a tray (either out of wood or metal) that sits in the existing battery frame. While an Optima is an attractive option, my cost preference is for a small, maintenance-free battery that will fit in this setup.

If there is a template out there for what an add-on tray might look like, please let me know.

Thanks, everyone, for your comments.

Larry
Larry Shoer

Larry, take a tape measure and visit your local battery shop. I found a class 26 fit mine, but then I rebuilt the old frame, but I think the original size.
Art Pearse

Art,

In combing the MGA archives, I discovered that many MGAs have had their battery trays modified from original. In particular, if a Group 26 battery fits (approximate size 8 1/4" by 6 3/4"), the tray has been modified.

As mentioned in my original posting, the battery tray in my father's MGA is as original (7Ē wide and 7 1/4Ē deep).

In the MGA archives Peter Dubaldi describes a very interesting removable battery tray that can hold a Group 26 battery. I think I will build something similar.

Larry
Larry Shoer

I must have customed it around the 26 size. A few years back!
Art Pearse

Larry,
I have a small 12 volt battery on my A. No need to hack saw or weld, just tweak the cabling. It is an Odyssey PC680. It is small, but packs a punch and I got it because my brother had one on his 2.4L Porsche 911 and it started that OK, and my A has a 2.1L bored engine. It is a sealed battery, so needs no topping up.

It's not cheap but (in the UK) cheaper than 2 6v batteries.

Alternatively, there are some cheaper, more traditional, square 12v batteries that are the same size as the 6v, but they have less cold cranking amps and some require toping up, such a those by Bosch.

all the best,

Grant :-)
G Hudson

Grant,

I noted that there are some traditional lead/acid 12 volt batteries available in Europe that are drop-in replacements for the twin original 6 volt batteries. To the best of my knowledge, none are available in the US.

The Odyssey PC680 is an interesting option. I have been cautioned that these smaller batteries don't have the reserve capacity of larger batteries. I'm not an expert at reading automotive battery specifications, but looking at the Odyssey manufacturer website is interesting. The PC680 has a listed CCA of 170 and nominal capacity of 16 AH and Reserve Capacity of 24 minutes. This is much less than the original twin 6 volt batteries (which in tandem, I believe, delivered about 300 CCA). I'm not saying the PC680 doesn't work well for you, but it does not appear to offer much reserve capacity.

Another Odyssey battery (PC925) is small enough to fit in the original tray (7.05 width and 6.64" length) and offers 330 CCA, 28 AH capacity, and Reserve Capacity of 52 minutes. This capacity more closely matches the original and a modern Group 26 battery. It is not inexpensive, however, with an Amazon price of $163 (50% more than the cost of the PC680). Since the Odyssey battery would be a drop-in replacement for the twin 6 volt batteries, I'm very tempted.

http://www.odysseybattery.com/battspecs.html

Larry
Larry Shoer

Original twin 6V batteries had 58-AH storage capacity.
Barney Gaylord

Hi All:
The early Mazda Miata had a very small 12 volt battery that is almost the same size as an A's 6 volt. Two of these could be run in parallel (instead of in series like the 6 volt originals) and give lots of starting amps.
It might be worth measuring and pricing this alternative.
I have one in the tail of my single-seater
Godspeed in Safety Fast
Jc


John Crawley

There are some severe warnings against connecting two batteries in parallel. If one of then might short internally (and it happens occasionally) the results could be catastrophic. You need large fuses to protect parallel batteries.
Barney Gaylord

Wow! Thanks Barney I had never heard that before.
Jc
John Crawley

Wow! Thanks Barney I had never heard that before.
Jc
John Crawley

John

I have two x 12 volt batteries in my MGA. I have them in parallel like yourself but I have isolators on each and only ever run one at a time. I only did the mod after I ended up with a spare battery and decided it was perhaps an option to 'carry' the spare in case of a failure when out and about. Over the years it has come in useful a couple of times when I switched on both together for that extra starting oomph in mid winter. One of the batteries is now on its last legs and I will not be replacing it; reverting to the conventional layout.

Steve
Steve Gyles

In Europe, the Fiat Punto battery will fit. I am fitting one to my B.

The footprint is the same as a 6v but it is slightly shorter in height.

Varta B35 is a popular model.


Dave O'Neill2

Dave,

Although Varta is now owned by Johnson Controls, a US company, Varta batteries are not sold in the US.

I opted to buy an Odyssey PC925T. The "T" means the battery has the familiar SAE posts for cable termination (which are an extra cost option for PC925).

I spoke with the manufacturer and learned something else interesting. This was described to me:

Not all chargers are compatible with the Odyssey batteries. The Odyssey approved chargers (listed under the FAQ section) charge the battery to a slightly higher voltage. Non-approved chargers may charge the battery to a lower voltage (and maintain that voltage), holding the battery in a state of partial discharge. This can cause significant shortening of battery life.

The company service representative told me the OMAX-6A-1B charger was a reasonable one for the PC925 battery. (Note that the company website doesn't explicitly list the PC925 battery with this charger.) I expect to buy this charger before the end of the driving season.

Thanks, everyone, for your help.

Larry
Larry Shoer

This thread was discussed between 21/05/2013 and 24/05/2013

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