I want to install a quick battery disconnect switch on my T, so I don't have to keep taking disconnecting the ground cable every time I put my T away in the garage.
Happy motoring, Warren
ps: of course if I used it every day I would not have to disconnect the battery.
get a good one and not the little brass one with the plastic sheet to insulate the parts and the green knob made in China. I use a rotary switch sold by Cole Hersey. It may be made in China but it is good quality.
Is your battery easily accessible from the top? If so, use one of these.
I use one and it works well
Frank beat me to it. Mine is exactly what he is describing not to use, but I've had one on all our T's and they have yet to cause me an issue.
I put one like that on all my Model T's, just in case, when putting away in the barn. You can't be too careful. Have to open the rear floor to access the knob, but that is a small price to pay.
I put them in the floor of my 26 and 27 right in front of the seat riser.
Easy to reach and not noticeable.
I had one like the one Greg showed. It got corroded and one day the car would not start. Not even enough to buzz the coils. This happened after I had been driving it and parked for about 3 hours. When I went to start it, it wouldn't start. I thought the battery was dead and was able to start with crank and magneto. Fortunately there must have been enough connection left that the generator did not get damaged. I removed the switch. If I want it disconnected I remove the ground cable at the battery. Don't need the switch. If you are afraid there might be a short, use a fuse in the main line.
Does your T have a starter? If so you need a good quality disconnect to handle the heavy current draw.
No starter? Almost anything will work.
I like the advice on that switch; "Keep clean and tight."
I try my best to follow that advice. Think I'll have a drink.
I adhere to the John Regan theory,and don't use any battery switches. Just one more thing to give you trouble.
Norman - A fuse might not help in the case of a high impedance fault (i.e. to a painted frame rail). All it takes is a few sparks and a small gas leak and ka-blew-ee, you've got a problem.
I just have a battery switch in between the battery and the starter mounted just below the driver seat. I also have a battery tender mounted to the battery so for longer down times it keeps the battery charged and in good shape. So, I just turn the switch off and plug the Tender in.
perko marine battery switches are the deal. 40.00 or so. 3 hole mounting or you can lay it on the back under seat floor. heavy duty. we install dozens a year here at the marina. I have had no problems using a 12 volt switch on my 6 volt car. turn the switch easy.
The switch illustrated above is what I've had for the past 11 yrs. No problems with it at all. Because of the large area of exposed brass, I have it installed on the negative battery terminal. This way, something metallic falling between it and the battery box won't cause a meltdown.
The main reason I have the switch is in case the insulation fails in the starter switch and it shorts to the chassis. Fusing is sufficient protection for the rest of the wiring.
I use this type of cut-off switch and it's hidden under the front seat of my '15 Touring.
The controversy over whether it actually enhances safety aside, my insurance company sees it as an anti-theft device and so, takes a few bucks off my annual bill.
Because my no-maintenance, Optima battery is hidden under the rear floorboards, it's difficult to access. When I need to charge the battery, it's a simple matter to hook the red charger cable up to the hot terminal on the switch and the black cable to the frame.
The cut-off switch also enables me to welcome spectators to pose for photos in the car without any concern about somebody engaging the starter by accidentally stepping on the button.
And, as I'm a little paranoid about getting rear-ended, my brake lights are adjusted to light up when the parking brake is on (like when I'm waiting at a red traffic light). The cut-off switch keeps the battery from discharging when the car is parked with the brake on.
Bob - Thanks for the info. I'd be curious how you fit it around the gas tank?
Why would you think that the battery needs to be disconnected if you don't use the car every day? I can't imagine any reason related to the number of days the car is or is not used. In general there is no reason I can imagine to introduce another set of connections in the circuit.
I hate the thought of anything that decreases reliability while increasing cost.
There's plenty of room for the switch under the seat and though the cables are curved, they're not encircling the gas tank. They're beneath the car.
Gee, if you are afraid of shorts causing fires or explosions, why are you not worried while driving the car? It seems that it is just as likely if you are driving the car too. I think they are silly myself.
If the switch costs less than $25 it will only slow the starter down a little when used on 6 volts.
The knife switches cause the most trouble, they corrode in the knife pivot.
"if you are afraid of shorts causing fires or explosions, why are you not worried while driving the car?"
Because you will be aware of it and can deal with it before the flammable parts of the car actually ignite.
Compare that to a car sitting in a garage out of sight for days, with crumbling insulation around the starter switch terminals. Maybe I should try an HRC fuse for the starter?
The reason people disconnect their battery while it is in storage is that fires can and have been started by faulty wiring. All it takes is one mouse determined to chew through the insulation.
The reason that people use a quick disconnect is because constantly removing and retightening the battery terminal lug stresses it to the point of failure. Plus, its more convenient.
Thank you to everyone who replied to my question. Dan B summed my thoughts best when he said "The reason that people use a quick disconnect is because constantly removing and retightening the battery terminal lug stresses it to the point of failure. Plus, its more convenient."
I am planning on enclosing the back cargo area of my T and it would be difficult to access the battery.
Happy motoring, Warren
So the general train of thought here is to not fix the crumbling insulation that could start a fire, but put in a disconnect for when the fire starts? Ok.
Doug - It's not good to generalize when you do not understand.
The reasoning behind installing a battery disconnect switch is the same reason behind a fuel shut off valve.
I get the discourse over water pumps, Kevlar bands, oil type. But didn't expect it over such a commonly found item in use for all sorts of applications.
Any vehicle that has been parked in my garage for any length of time has had a battery disconnect installed. Is it necessary? Probably not. Does it make me sleep better at night? Absolutely.
"Gee, if you are afraid of shorts causing fires or explosions, why are you not worried while driving the car? It seems that it is just as likely if you are driving the car too. I think they are silly myself."
If a fire starts while I'm driving the car, it probably won't burn down my shop, several other cars, tools, parts, tractor, toy collection, and bar when it happens. Letting a $10k car potentially burn down $150k+ worth of stuff, seems more "silly" to me than a $8.00 switch that can be removed in 5 minutes if it ever gives any trouble.
I have a rotary... plastic one on my 1927 which helped me save the car when my worn out wires grounded. On the forum John Regan pooh-poohed the use of the cut out as it causes more faults than saves problems.
Well, I want to officially state that John is, as always, right. I'm just finishing up the 1913 Brigade car and trying to get it running and de-bugged. I've been going crazy sometimes getting it to run and other times not. Finally today I found, JUST AS JOHN WARNED, that the brand new rotary cut out switch which has a beautiful installation in an inaccessible location (now that the sheet metal is on) is intermittent! I can set it half way between on and off and have it stay on... not good. I wired the hot lead to the battery with fusable wire and have a fuse block, so now I am going to rewire the ground to the frame... I'm sure that is what John would have suggested.
No cut off, just good modern insulated stranded wires.
I do advocate a single 25 amp weatherproof fuse be installed in T's that have electrical systems. My background is electrical and I don't have a disconnect switch on any of my cars. In truth if I was to put one on any car it would make the most sense to put it on my modern cars. They have way more likelihood of catching fire than my T just due to the probability of a worn wire or pinched wire somewhere. The more wires and connections the more likelihood of a short but modern cars are well fused and that is more important since a fuse works whether you are there or not and it even does something that people do not do with their switch and that is that it will continue to melt and blow itself open even if the fault starts to go away since a fuse that starts to melt takes less current to finish itself off than the amount that started the melt. This makes fuses a very good protection device. They do cause one more connection so adding fuses willy nilly everywhere just installs problems with no added protection.
I want to address one fault that has been mentioned several times now. I have no dog in this fight since I am not here to change anyone's mind really but I do come here when I see something that I feel is unsafe and people are not aware of the danger in the same way I personally about burned my shop down by being unaware of the danger of linseed oil. What nearly burned me out was not the linseed oil but my ignorance of what I was doing. My own lack of knowledge was the real danger. Being just afraid of something does not make you safer by just staying away from it. Understanding the danger and trying then to prevent that danger from happening is far safer. I could have just purchased a larger fire extinguisher when I nearly burned my shop down but that would not have saved my shop since I was not addressing the real fault which was ME and my own ignorance about spontaneous combustion. Disconnect switches are sold based upon fear and ignorance. The "brass green plastic switch" i looked at that was pictured on this thread was not even made from brass but rather brass colored anodizing or plating on some sort of cheap steel or iron but that is not my point.
There was talk of a direct reason about having a switch on the battery negative lead in case the starter foot switch insulation failed. Doug Money commented that it might be better to fix the insulation and he was totally correct on that one as far as I am concerned but that too is not my point here. The foot switch has 2 studs that are insulated from a direct frame connected ground via the starter switch bracket which is very near the battery. In other words if one of those starter switch stud washers fail then it is correct that a very major short will occur. But a disconnect switch mounted on the battery was touted as being the best safety item for that. That is totally false and here is why. I doubt if many of you have ever witnesses a car battery boil. I am not talking about overcharge boiling away of the electrolyte but rather the actual boiling of the battery due to tremendous internal heat from an absolute direct short on the battery caused by a very low resistance path that will not melt or go away. Very high currents often cause a short to weld in place and not be removable even with substantial force. The foot switch could do that easily since the bracket, studs, and battery cable if correct size could easily destroy a battery and you would see a terrible sight of a battery that is boiling. It melts and deforms and gives off smoke and fumes and acid leaks everywhere. The suggestion that you could stop your T - get out and lift up a door or floor board in time and disconnect your battery via a disconnect switch is ludicrous. You would not want to go anywhere near a battery that is boiling or about to start boiling. Your best shot at that point is to get well away and hope for the best to be able to fix up the car later.
You cannot make a good reliable switch unless you can prevent the mating surfaces from tarnishing or becoming pitted and dirty. Switches that are reliable use precious metal on the contact surfaces to prevent tarnish and pitting. Gold is/was used on really high reliability low voltage switch surfaces and I assure you that there is not one ounce of gold used on any battery disconnect switch or it would cost a ton. These are low grade metal contact devices generally. To make a reliable switch that can switch 200 amps or more and not drop any or extremely small amounts of voltage is no easy thing to do. Even a few thousandths of an ohm will drop enough voltage to make the starter drag and that will cause it to overheat. How is that safer? The switches quickly become intermittent simply because it is nearly impossible to keep the required massive contact surface in perfect mating contact with the other to get the extremely low resistance you need. Even if you get it near perfect you have a tarnish issue on switches that switch less than about 35 Volts. Most cheap switches on other applications besides high current battery switches rely upon a "wiping action" to wipe the contacts across each other on their way to final positioning. The T starter switch works that way. This is to clean the contacts and hopefully wipe away any tarnish. This is also sometimes used on household switches that are not mercury but those switch 120 Volts and generally speaking all switches that switch less than about 35 volts will have a problem with oxidation build up if they are not used often. I had a guy call me once who was looking for a new relay for every one of his door power windows on an old 6V chrysler. I walked him through a procedure to simply remove the switches one at a time and put them in series with a 25 watt light bulb at 125VAC and switch them a couple of time to remove the oxidation on the switched contacts. The contacts were well insulated and were typically rated much higher than 6V. I told him to run the windows up and down at least once every month and he would not likely have the problem again. Those switches had silver on the contact surfaces but they had enough tarnish to block the contacts when the switches sat unused for many months and were only switching 6V. Low voltage switches have problems that your house switches do not have. Be safe but learn and understand if and why you are safe or not. If you don't understand it all and are simply operating out of fear then you have listened too long to the guy selling you the disconnect switch and have not learned what you need to know to be safe. Things are safe and made reliable not by safety devices as much as by being designed safe in the first place.
Sorry for the long winded post.
I am trying to learn to be safe but I need to learn and understand.
Why does a few thousandths of an ohm drop (due to some electrical resistance} cause the starter to drag and cause it to overheat? I would think that the added resistance before getting to the starter would result in less voltage and less amperage getting to the starter.
If I think of a light bulb replacing the starter, then in I put less current and voltage to the bulb than designed for, would not the bulb be not as bright and not run as hot?
Thanks again to everyone for taking the time to offer your thoughts on this subject. As stated before I'm considering installing this not so much for safety, but because I want to enclose the back of my T and that will make it difficult to get to the battery. I like what Greg said "Any vehicle that has been parked in my garage for any length of time has had a battery disconnect installed. Is it necessary? Probably not. Does it make me sleep better at night? Absolutely." I also agree with Derek, "If a fire starts while I'm driving the car, it probably won't burn down my shop, several other cars, tools, parts, tractor, toy collection, and bar when it happens. Letting a $10k car potentially burn down $150k+ worth of stuff, seems more "silly" to me than a $8.00 switch that can be removed in 5 minutes if it ever gives any trouble."
Happy motoring, Warren
I have a battery disconnect on both my regular-use Ts... cheap green knob on the touring and a heavier through-frame switch on the speedster.
Neither has given any trouble — yet — but their primary use is at my volunteer job. On nice days I drive a T to work and the car stays outside and accessible to the public for six hours at a time. Most people respect the Please Don't Touch signs but occasionally the horn gets beeped, the starter pushed and so on. One time the headlights had been turned on and the battery partially run down. A battery shutoff here makes a lot of sense.
The light bulb in your example is designed for continuous use. A starter motor is not designed for continuous use. For devices designed for intermittent use the temperature in them begins to rise immediately when you apply power and the assumption is that the device will be turned off quickly before the heat becomes excessive. If your starter drags your T may be difficult to start and your starter motor will get hot with the extended cranking time.
i am like jim i put one on the floor in front of my seat on my 27 and haven't had any trouble yet . i would rather have it not start sometime than maybe burn up.
Here's an idea...
I have one car with a battery disconnect. John Regan's suggestion of using the 25 amp fuse seems to make more sense. I am not an electrical genius by any means as witnessed by last months flames. If you install a disconnect because you're worried about shorts and having a fire the fuse should blow before a fire ever starts. The fuse is always in place, you could forget to turn the disconnect off. If you really want a break in the circuit you could always pull the fuse out an accomplish the same thing.