Watched how Daivid Frieberger wired his system disconnect in his Model A racecar and he used 2 (200 amp) Cole Hersee continuous duty solenoids. Said they were about $50 each. Where I'm looking on Amazon, they are now about $75 each. While I want the USA made Cole Hersee, most others I see are 300 Amp and foreign made. They are about $15-$20 each and the reviews on them are mostly 4 stars or better. Anyone had any experience with the off brands ? Basically its hard to justify $150 over $40, especially when most people buying them seem to be satisfied.
You are saving $110. How much are the components you are protecting? Reviews on the big sites have been bought and paid for going on over a decade now. One more little opinion, I used to watch his stuff. After a while, I noticed he put together a bunch of stuff, but most of the time, it blew up faster than he could build. Blasphemi has how many passes under full power without breakage? I'd rather hear from someone who has done a few power tours and finished, or even better a few drag weeks and had a driver after. Like the other gentleman commenting before me. What is the thing running that needs that much amperage? Electric fan, maybe 30 amps, fuel pump the same, ignition is probably under 10 amps. Electric water pump too? Either this is for a WOT high output alt and some crazy sound system, or it's overkill. Speaking of which,. I'd look at the competition sound arena. They have some high draws and expensive stuff behind the safety. Some of the stuff is just Joe Blow who burns through everything, but some are serious and take care to do it right.
I use one of these. It works fine. https://watsons-streetworks.com/product/toggle-battery-disconnect/
In Friebergers case he is using them to disconnect/shut off the engine per NHRA rules. His explanation is that the way most people wire their cars, if the alternator is spinning, an engine can continue running off the current from the spinning alternator even though the disconnect has been disconnected. His words, not mine. The 200 Amp disconnects are sized for current spikes I guess. I have a couple new/rebuilt CS style alternators. I plan to run a 145 amp alternator, so 200 is about the closest one to provide a margin of error. I have another rebuilt CS130D alternator thats rated for 105 Amps. It came with a copy of the "Test Report" from the rebuilder. It shows that the 105 Amp unit puts out 125 Amps @ 4000 rpm and continues up to about 134 Amps @ 6000 rpms. Now an alternator spins at a higher rpm than the motor does, so it should reach 4000 long before the motor does. That line of thought however makes me wonder just how many Amps my 145 Amp unit will actually produce? This concern is all about what will happen when/if I have a problem. I realize the alt won't be producing these kind of amps during most of my driving. Here is the 105 Alt Test Sheet to show I'm not imagining this. Here is something similar to what I'm looking at. Here are some notes I made from the Frieberger show. He was going to have 3 shut offs in his Race Model A. Rear Main, Dashboard,and Firewall. I don't want all that, but would be nice to have at least one disconnect. So, this is kinda sorta what I'm looking at, but just one shut off.
Depends what the load is. You haven't mentioned that yet, I don't think. Do you think you need the same protective stuff as an 8 second drag race car? If so, why?
And that is true! Most are not NHRA complaint kill switches, just battery disconnects. I have had this argument with guys on here before that claim there's will kill the motor. I tell them to go home and try it and report back and I never hear form them again. All my cars have kill switches that will kill a running engine because they have 4 posts on the switch and the alternator runs through them. This Longacre from Summit is my go-to. $100 bucks but a lot cheaper than what you propose. I don't build race cars, and I just one on each car and I shut them off every night when I bring them home for both peace of mind and to prevent parasitic drain from clocks and such. For what it's worth.
I have never used my battery switch to shut off the engine. I use it to isolate the battery when in storage. I shut the engine off with the ignition switch.
Yes, a basic 2 post kill switch does not shut down a running engine with a charging system, but the answer is shown by @Bandit Billy. @pprather , it's a safety item for sanctioned racing. If a car crashes and the safety team gets to the scene with the car still running or damaged enough to have electrical concerns, it's so they can shut off all power. This is for drag racing, circle track and road racing. Not so much on street stuff. I agree that it is not the way to turn things off normally. The charging system should be providing only enough amps to supply the needs during most operation. The only time it will go to higher output is just after startup with a partly drained battery, when it's supplying normal draw AND charging the battery. I agree that it's a good idea to plan for a worst case scene when sizing components. However, you need a 200 amp switch so that if the battery is almost dead or the charging system full fields and the engine is turning at 4000 RPM and you can't just turn off the ignition but you can reach the kill switch, it will be sized properly.
Your 145 Amp alternator will never put out that many amps unless it fails or you have 145 Amps worth of electrical draw in your system. Add up all your accessories and that's your max amp draw. Realistically, how many of those are on at the same time? That's the number you need to be concerned with. An alternator only supplies what is required, no more, no less. You could have a 200 Amp alternator in a highboy roadster with a Magneto, headlights and no other electrical components and that alternator will be barely working.
In the one diagram I see dual 200 amp circuit breakers feeding one main that feeds into a underrated switch and no wire gauge sizes noted. A combined 400 amp main is going to need a huge wire gauge to be effective or the wire will become the fuse. On my rig I went with the battery switch and three 50 amp mains that feed to the various submains to power the car. I would rather have three smaller wires than one huge feed and that eggs in one basket thing to keep in mind. I divided the three 50 amp mains into power groups (lighting, powertrain, accessories) and the stereo amps are triggered via the stereo remote lead but wired/fused directly to the battery switch for their main power. Next to the battery switch is the main fuse for the alternator output. Twist one switch and press the manual trip on the breaker and the car is electrically dead.
You need to send the Alt Charge wire to the battery side of the Cut-Off switch. But the Alt wire is live in the engine bay even when the battery is disconnected. What I do is add a decent Vishay Diode to the charge wire [close to the Batt] so the Alt can charge but cannot discharge. This ^^^ is really handy when working in the engine bay You only need a 30A -40A cut off switch if you know what you''re doing [40A = 480W which will power the brightest of headlights] The trick is to put a Ford Starter Solenoid next to the battery and bridge the solenoid at the starter [which also fixes starter motor heat soak issues] By doing this the main battery cable to the starter is "dead" unless the engine is being cranked over. This is a schematic of how I did the wiring on a Falcon Touring Car [this is up to FIA specs which exceed NHRA specs] I used a simple marine 20A toggle switch on the Front Fender [FIA Rules] as a Battery Isolator I have witnessed a car burn to the ground after being T-Boned and the main battery cable short circuited with gas everywhere. With my above method /schematic this shouldn't happen. Everything is dead by default This is a Vishay Diode If you don't want to go to this trouble ,just use a simple cheap 2 post battery isolator ,and connect the Alt Charge wire to the battery side of the switch [But I still recommend the diode] This stops the Alt charge looping back and feeding the ignition, AND it is not good for the Alt to be disconnected from the Battery while the engine is still running
Thanks for the diagram and info @Kerrynzl. I'm learning a lot from you guys....... I don't know yet what my max load will be because I haven't finalized all the components. My 2000 Chevy pickup with basic features (auto/air/radio/factory efi) came equipped with the same 145 amp alternator. I figure it should be easy to find one at any auto parts store for a long time if I break down, and should be plenty for my Coupe which should probably be near the same. Mostly I want to insure that at lower cruising and idling, that the alt is producing a good charge. I know a lot of people have problems with no/low charging with the older style alternators. Its more of "just wanting to do it" than a necessity. I do like the idea that if I have an engine malfunction while testing and tuning a newly built engine ($$$), I can insure that I can shut it off quickly. Yes, but I believe in looking at the "worst case scenario" and trying to plan ahead of it..........then hope I never need it. You know how life goes, if you plan for something ....you never need it......and if you don't plan for it, you do.
I use a Cole Hersee 24200 Continuous Duty Latching Solenoid as a remote battery disconnect on nearly every car I wire.
The circuits would be so that either circuit could carry a full load of 145+ Amps if the alternator malfunctioned. It would not be a total of 400 Amps.........but I can see how the diagram could be interpreted that way. I was trying to sketch this while watching the video. Thanks for pointing that out.
The Jalopy Journal
