Hey guys, I am planning on putting a battery disconnect switch on the ground lead of my battery, just as storage / theft devise. What amp switch do I need to run. I see the 175 amp ones and they are faily decent priced, and the higher amp ones are more expencive. Just wondering if anyone has run one of the 175 amp ones, or do I need to pony up an but the more expencive 250+ amp one? This is going in my model a coupe with the battery in the trunk, if that helps. Thanks, Scoggman
The rating depends on the cranking amps that your starter needs to spin your engine. Big high-compression V8 engines pull more amps than a low compression 4 banger.
Here are some thoughts on that, MY thoughts: You WILL lose all electronic information, radio stations, etc. Might not matter in an ON Topic car, though. This does introduce more resistance to the starter circuit, and a lot of starters I've tested on car take more than 175 amps. And these are mostly 4 cylinders. Possibly a better option would be an auxiliary switch that cuts power to the ignition, but leaves the high amp circuits alone. If this is just to eliminate battery drain, just remove the cable, there are quick release cables available. Cosmo
Any regular battery kill switch at your local auto parts place will do the trick. Like Cosmo stated as for your radio if you have one you can run the radio memory lead to the batt if ya want.
Radio? ....... haha. Who needs a radio when if you got a hot motor to listen to, that should be music to any car guy's ears. But, too each his own. Just being funny here ......,please don't take it wrong way If you have a master cut off switch at least you will be able to sleep at night knowing that the shop didn't burn down because of some fluke electrical accident. Master cut off switches are made for this purpose and loss through them is minimal. They can be placed where easily reached. Make sure cables are correct gage based on amp draw and length of cable. The battery may be hard to get to if you are talking about that A in the picture (like in the trunk as you said, or underneath the body). Master cut off also alows for quick shut off when on the road. If the car is on fire, it will most likely be burned up before you get to the battery in the trunk, behind whatever else is in there at the time, and undo one of those quick disconnect terminals. Battery store can tell you want switch to run. Generally - more amp switch is more heavy duty.
This debate about what side to put the cut-off switch, positive or negative. Ron Francis recommends positive side only. But saw factory cutoff on a Ferrari on the negative side. confused. Ago
Both positive and negative work, but I always put them on the positive side. I work in the marine industry and that is the way 99.9% of the boats are done and how it is mandated by the American Boat and Yacht Council. Just go to any marine discount house and pick up one there that only has two positions. Perko makes one, but Blue Seas makes a better one that is also smaller. They even make ones with removable knobs for theft protection. Don Even a simple one like this works great. My Son is using this one on his T bucket.
Same here, all mine are on the positive cable. I also put a 1 amp fused constant hot off the input side for the cars that have radios with memory.
Arguments I've heard. Positive side disconnect, you cut the power at the source. If something shorts, no problem til you turn it back on. Negative side disconnect, power is always "on". But if the switch is at the battery, nothing can ground out til you turn it back on. Seems same same to me if the switch is battery mounted, no power flows. Am I missing something? RB
If the switch is on the ground side than any accidental ground will become the carrier. Ask the guy who had his car burn down because the copper oil line to his gage became a ground. If there is no current from the battery there can be no problems, just put it the hot side. I once saw a car that had a disconnected ground wire start when someone touched their bumper with their cars bumper. Accidents happen!
'Typical' starting current for a V8 will be about 250 amps and will be unlikely to be less than 200, and installing the battery in the trunk can increase that unless you size your battery cables large enough. You can add another 10-20 amps load if the cables are smaller. Spring for the larger switch.... and install it in the positive cable.
I believe there are several threads on this subject. Check out this switch from Speedway. It is rated at 1000 amps instantaneous and 180 constant. I have these on a couple of cars with no problems. Also check out the PDF instructions. They (and NHRA) recommend putting it in the POS circuit. (on a NEG ground car). http://www.speedwaymotors.com/Four-Post-Battery-Disconnect-Switch,6967.html
yep, 175 Amp is plenty. use one that has on/off plate. I prefer ones that the handle stays on switch. that way in an emergency you will not be looking for removable handle. use on positive side. be sure to use large gauge cable for all battery cables.
I used to work for a heavy truck OEM and when figuring out one on my '57 pickup I asked a buddy of mine who worked in the electrical group. They were all installed on the positive side. Good enough for an OEM, good enough for me. Also make sure your cables are sized accordingly depending on the battery and switch locations.
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