Relocating Battery

[moggiegeek]

I'm wondering about relocating the battery to the boot in order to create space for a remote oil filter and thermostat as well as brake and clutch fluid reservoirs and windscreen washer reservoir.
The engine is originally a 1275 A+ with filter above starter motor and space is limited - servo position for example.
My question is whether such a long cable run between battery and starter motor would be a problem with voltage drop or otherwise? It worked for the mini after all....

[philthehill]

My battery has been re-located to the boot and I have never had any problems.
I used a classic Mini (which has the battery in the boot) feed cable. The cable is inside the car and feeds from the boot round the side of the boot to passenger bulkhead.
My engine is a 1275cc 'A' Plus Ital item with a very high compression ratio and the MG Midget starter turns the engine over very well with no discernible power drop.

[svenedin]

My car has always had a bit of a stink of petrol in the boot despite a new tank, sender, filler hose etc. A spark from the battery could potentially cause trouble in the circumstances. Under the bonnet is much better ventilated. Presumably the battery would ideally be mounted in a central position in the boot and securely anchored against moving. One advantage might be that the battery can be lower than it is under the bonnet and seeing as batteries are heavy this would help lower the centre of gravity of the car a bit.

Stephen

[geoberni]

No problem with mounting the battery back there, so long as the correct size cable is used.

However, any battery mounted in the boot, which as Stephen says can often smell of petrol fumes, must have suitable external ventilation of the battery.
If you're using a modern 'sealed' battery, all you need do is fit vent pipes to the vent holes on the battery.
Those are the holes that have the Red Plugs in them on a new battery (and sometimes get forgotten about when people fit a new battery..... )

https://youtu.be/SRQSDKsXV3M

[kevin s]

Battery in the boot will be fine, the one in myTR7V8 is there and starts that just fine, the likes of car builder solutions sell the cable by the metre, 50mm2 should be fine for a minor, 70mm2 even better.

It's also worth fitting a fused earth cable so if the cable gets crushed in an accident you don't turn the battery into a bomb I used mk6 transit one but there are other options out there.

[Myrtles Man]

All Rover P6's had boot-located batteries too and that arrangement worked just fine.

[moggiethouable]

As long as you use a well insulated cable losses are negligible, current rated above what you think is required.

[moggiegeek]

Thank you all for your replies. I'd like to do this, using 50mm2 or 70mm2 cable, venting the battery as suggested. I'm having difficulty locating a suitable fused earth cable ( it's -ve earth wired.)
Given it's a safety critical item I'd prefer to buy new. What amperage fuse should it have? It's a standard midget starter motor. Does anyone have a a suggestion as to where to source?
Many thanks

[dp]

Curious to learn more about fused earth.

Anyhow,

if you're planning to have a remote oil filter, it's a small step to adding an oil cooler into the mix a the same time.

[geoberni]

As long as you use a well insulated cable losses are negligible, current rated above what you think is required.

The Cable Losses will be governed by the mm2 of the cable, nothing to do with the insulation.

There's been some pretty hefty suggestions of what cable to get.
I wouldn't go more than 40mm2, that'll be happy supplying up to 300A; you're starting a classic car, not a Diesel HGV.
I have a Clamp Multimeter, so it's easy to check current without messing around with high current connections, and my 1098 cranked for 15-20 seconds with the Ign off draws a steady current of between 107-109 Amp.
So even if for some remarkable reason your 1275 pulled twice that, a 40mm2 cable will be more than suitable.

If you want to fuse the Battery circuit, there's several options out there.
I'd recommend AES for Cable and Fuse choices. There's some neat little Cube Fuse assemblies you can get these days, or you can fit a Midi Fuse Holder with fuse. It's not normal practice to fuse an earth, you should fuse the supply line.
https://www.autoelectricsupplies.co.uk/

[Bill_qaz]

I'm wondering about relocating the battery to the boot in order to create space for a remote oil filter and thermostat as well as brake and clutch fluid reservoirs and windscreen washer reservoir.
The engine is originally a 1275 A+ with filter above starter motor and space is limited - servo position for example.
My question is whether such a long cable run between battery and starter motor would be a problem with voltage drop or otherwise? It worked for the mini after all....

With lots of room for a servo on the carb side of the motor why do you need to move the battery?
Or is it just something you wanted to do.

20230622_155213.jpg (2.21 MiB) Viewed 6850 times

[moggiegeek]

Thanks for the contributions. In answer to the last point the changes are really just to neaten up installation of brake and clutch fluid reservoirs, wash bottle, remote oil filter and thermostat for oil filter which is located at front of radiator having modified front panel and inner rad panel to suit. It all just needs plumbing in. So it's really "a keep me happy task!"
I do take the safety issues of battery in close proximity to fuel tank seriously hence the earth lead fuse and breather.
Happy to go with 40mm2. Actually I've got loads of 25mm2 cable so could I run three cables in parallel as live feed from battery?
Looking at new cable prices is a bit scary - in region of £50.
Thank you

[Edward1949]

You'll be moving the centre of gravity rearwards by a small but not insignificant amount. This will have a slight adverse effect on the car's directional stability.

[ndevans]

With lots of room for a servo on the carb side of the motor why do you need to move the battery?
Or is it just something you wanted to do.
20230622_155213.jpg

There's plenty of room if you've got a 1098 with a standard exhaust and carb, but not so much if you've got a 1275 with a 3 branch exhaust and an HIF38 or 44 carb.
My servo is on the other side of the engine bay, there's just about room between the starter/distributor and inner wing. Access to the starter isn't great though, with the Marina 1275 lump having the oil filter right above the distributor & starter.

[kevin s]

Ours is on the RH side too, as you say it all gets pretty crowded down there, I'm contemplating moving it to the wheel arch area just below the headlamp (we have wheelarch liners so it's fairly dry under there)