Battery cut off switch

frankenyoter

frankenyoter

No Rain, No Rainbow
Joined
Mar 17, 2009
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Going to put a battery shut off switch on the blue truck and options seem endless. I know the $12 one is not what I need and the same with the $150 ones.

what’s a solid option of a good switch? Amps? Will 175 continuous be enough or do I need the 300?
 
Blue Sea 9003e (350A cont, 1200A for 30sec), or Blue Sea 3000 (600A cont, 1750A for 30sec). About $40 for the former, and $50 for the latter I think.

That's just a single circuit, On/Off switch. If you need more circuits than that, or an A/B battery switch, or an extra alternator field wire disconnect, they have options for that stuff too.

If you need something with a removable plastic key, Blue Sea 6005 (there's a part number for black as well). Slightly lower rated (than the others I mentioned) at 300A continuous, 900A for 30sec cranking. $30 for those I think.

They're all IP66 rated too, so mud/water/whatever is not a problem getting into the switch body.
 
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What about the chinesium knife switch terminal that is at all parts stores? Looks skookum enough if all you want is a battery disconnect without "security".
 
Fabrik8 said:
Blue Sea 9003e (350A cont, 1200A for 30sec), or Blue Sea 3000 (600A cont, 1750A for 30sec). About $40 for the former, and $50 for the latter I think.

That's just a single circuit, On/Off switch. If you need more circuits than that, or an A/B battery switch, or an extra alternator field wire disconnect, they have options for that stuff too.

If you need something with a removable plastic key, Blue Sea 6005 (there's a part number for black as well). Slightly lower rated (than the others I mentioned) at 300A continuous, 900A for 30sec cranking. $30 for those I think.

They're all IP66 rated too, so mud/water/whatever is not a problem getting into the switch body.
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im looking at all of their options and even the ones with alternator field wire state to turn off the vehicle before turning off.

what I want/need is for the switch to not only disconnect the battery but also shut off the vehicle. Say rolled and couldn’t reach the key or was knocked out, so someone could walk over and turn the bed mounted switch and kill power and turn off the rig.

My little mind thinks that AF field switch would run charging wire through it and when I turn it off everything goes cold. I’m I headed the right direction?

If not please advise how this should be accomplished on my 97 3.4 Toyota motor?
 
frankenyoter said:
im looking at all of their options and even the ones with alternator field wire state to turn off the vehicle before turning off.

what I want/need is for the switch to not only disconnect the battery but also shut off the vehicle. Say rolled and couldn’t reach the key or was knocked out, so someone could walk over and turn the bed mounted switch and kill power and turn off the rig.

My little mind thinks that AF field switch would run charging wire through it and when I turn it off everything goes cold. I’m I headed the right direction?

If not please advise how this should be accomplished on my 97 3.4 Toyota motor?
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Normally you can't do both functions (engine shutdown and battery disconnect) at the same time with a battery disconnect switch. That's really the difference between a kill switch and a battery disconnect switch. You actually need a kill switch for what you're talking about (they have more poles to isolate more stuff usually), and I don't think the addition of the AF disconnect is going to be enough (I'll need to ponder that).

The AFD contacts in the switch open before the main contacts open, so the field collapses to protect the diodes before battery power is disconnected. You need to have an external regulator obviously, because you're shutting off the field wire (not the charging wire). You don't want to disconnect the load from the output of the regulator by disconnecting the charging wire, that would be bad. That's basically the same as disconnecting the battery with the engine running, as far as the alternator load dump is concerned.
 
You could use a regular kill switch wired in to the ignition run wire if you want it to kill the engine.. like fabrik8 said, if you find one with two circuits, one high current and one low current, you'd be good. Or don't worry so much about battery disconnect and just kill the ignition - pump and all shuts off when you turn the key off...
 
I disagree with the last posts.
Killing the ignition is fine and all to stop the motor, but you want a total battery kill in a rollover safety switch.
Ask me or @rockcity what happens when your rig is upside down, the motor is killed and the dang electric fuel pump just keeps on squirting gas on the the literal flame...

Ever seen that "drive it like a rental" busted knuckle shirt?...that picture is from that EXACT scenario.

I agree and understand with what @Fabrik8 is saying regarding being hard on the alternator..but I think he is making a theory over execution folly. You arent going to use this switch (presumably) to cut the rig off everytime, this is an emergency only kill, right? You arent going to destroy an alternator by using this method 2-3 times over the course of a forever.

Next you go down the rabbit hole of whether to break the + or the -....

553756_357355851005548_2089375119_n.jpg


burnt-up.jpg


burnt-3.jpg


That is how you turn 60k into $3.50 in 15 minutes....
 
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Ron said:
I agree and understand with what @Fabrik8 is saying regarding being hard on the alternator..but I think he is making a theory over execution folly. You arent going to use this switch (presumably) to cut the rig off everytime, this is an emergency only kill, right? You arent going to destroy an alternator by using this method 2-3 times over the course of a forever.
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I agree mostly, but I was really saying that he may need a different type of switch instead of just a simple battery disconnect.

And yes, you can destroy a regulator/rectifier assembly with a one-time load dump, depending on conditions.
If just having a safety shutoff is the most important thing, the alternator doesn't matter that much if it gets damaged because of a lack of load dump protection. But, once you're back with tires-down, you may not have a functioning alternator anymore to get you back home.

There are ways to do load dump protection though, by shunting the energy somewhere else (a TVS array, etc.). Again, actual kill switches sometimes have things like load dump protection built in, and additional poles to take care of some of the other practical considerations. Now why can't I find one of the damn things while we're talking about it.....?
It's possible that your truck already has some alternator load dump protection built in, but I'd want to know where it is first, so you don't end up isolating the load dump protection by disconnecting the wrong part of the circuit. A lot of modern stuff has the load dump protection inside the alternator, but I have no clue whether it does or not, and whether Toyota would be doing that in 1997. I'm just assuming it doesn't, because I don't know.

How the alternator is disconnected, what side of the disconnect switch it is attached to, etc., are all considerations if the battery is to be disconnected and the engine needs to be shut of at the same time. For example, if you connect the alternator to the battery side of the disconnect switch, load dump doesn't become a problem, but then you aren't disconnecting the alternator from the battery if a simple SPST disconnect switch is used, even though all of the power is now disconnected from the ECU, fuel pumps, ignition, etc. So your engine is no longer running, but your battery isn't completely isolated either. If the alternator is on the engine side of the cutoff switch, and the alternator output is not disconnected, the engine will not shut off.

It's really a matter of what you're trying to actually do for particular safety situations, and what you want to disconnect versus completely isolate, etc.

As you've noticed, I'm not much of a "Just do this, you'll probably be okay. Maybe." type of person. :D

Seriously though, you could just disconnect the alternator and sort out how to deal with the damage after it happens, if it happens.
 
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If your intent is that everything turns off when you operate the battery kill switch, make sure it’s wired properly. If you put it inline with the battery, it won’t kill your motor as the alternator will keep the engine running. Wire it inline with the alternator.
 
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Ron said:
the motor is killed and the dang electric fuel pump just keeps on squirting gas on the the literal flame...
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however if the fuel pump is run off of the ignition on position, the fuel pump will go off when you hit the shut off switch. If the battery disconnect were simply in the positive battery cable it wouldn't necessarily kill the motor when you disconnect unless you seperate the alternator wire like discussed above. I didn't mean to make it seem unimportant to entirely disconnect the battery, just unnecessary if you're cutting off the fuel pump since it's powered only when ignition is hot.
 
I appreciate everyone’s input, however I’m not any more clear than before.

What I’m after is to have a switch in the bed that kills all power and stops the motor from running. The majority of the time that switch will be hit for when the truck just sits waiting on the next trip through town or to Harlan, but I want the safety feature of a one stop shop kill switch/battery disconnect so my pile doesn’t end up like the photo that @Ron posted.
 
frankenyoter said:
I appreciate everyone’s input, however I’m not any more clear than before.

What I’m after is to have a switch in the bed that kills all power and stops the motor from running. The majority of the time that switch will be hit for when the truck just sits waiting on the next trip through town or to Harlan, but I want the safety feature of a one stop shop kill switch/battery disconnect so my pile doesn’t end up like the photo that @Ron posted.
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TLDR: disconnect the switch while it's running. Motor dies? Good, it'll work. If it continues running, get a disconnect with an additional circuit and wire it in on the hot wire to the ignition, and retest.

There.

I think that clears the muddy waters. And satisfies @Ron s concerns.
 
Yes, make damn sure it kills the power generated by the alternator. I had a similar issue with my boat a few years ago. Ignition switch failed. Tried to kill it with the cutoff switch. No go. Bummer. Finally killed it but had to rewire kill switch so it actually worked as expected. Luckily it wasn’t on fire, but it could have been disasterous none the less.
 
Have the ignition and fuel pump turned on with a relay.

Hook one pole of the disconnect switch between this fuel & ign relay and ground.

The other pole of the disconnect switch between battery (-) and main chassis ground.

Will that work as needed?

When the disconnect/kill switch is closed, everything works as normal.

When the disconnect/kill switch is open, the motor is killed bc ignition and fuel pump is shut off, and entire ground is interrupted?
 
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