Which Battery Switch

Before we get into my next thread about the latest problem with Dr.Perky 6.354, I need to put a big battery switch on my starter battery to help diagnose what is wrong. Looking at Defender, it seems like the only difference in switches (single on/off) is the amperage. My Energizer starter batter from Sam's club doesn't have a CCA number on it than I can see, so should I just buy the highest amperage I can find? (600A) Then, the starter wire is currently (<-- pun intended) older welders wire, do I need to put together a 1/0 AWG wire or will 2 AWG be enough to make the 18" jump from the switch to the battery?

Thanks y'all,
Tom-

P.S. If you want to get into the problem in this thread, we can do that. It's not a stretch to call it an electrical issue. Even though I had plans to put it in the Power Systems section. It's up to y'all.

Tom, The amperage for your battery or CCA have nothing to do with the size of your switch. It is the potential amps your starter can generate. Where are you putting the switch? Not between the battery and starter I hope. Chuck

That's exactly where I was going to put it.

The yet unpublished problem I am having with my engine is that when I turn the key to start it, something is keeping the starter motor engaged and spinning. That sends me lunging into the bilge to spin off the wingnut of the starter battery and yanking off all of the leads in a shower of sparks. The plan was to put a switch there to make it easier and safer to test out possible fixes and always have a way to remove the battery from the starter. The genset is currently like that now and I figured that it was something I was needing to do anyway.

Am I wrong? Please explain.

Gonzo have you checked your starter solenoid.It sounds to me like it is staying engaged.

* I concur, sounds like it's a bad solinoid, you know the round thing on the started that the battery cable is attached to.J.T.Duncan

It's brand new... And the last time it did this with the same starter, I took it back to the same guy that rebuilt it and he tested it as fine. Weird.

Ok then, do I need to lube the thrust shaft?

Hiya,
** Could be a sticky bendix (Mr. Gonzo, might try cleaning and lightly lubricating the shaft and drive)....Ahhhh, what about your starting switch?* Could THAT be faulty?

All stuff I need to check. In fact, I tested the ignition switch last time.It tests as good, but I'm still curious about Chuck's comment about battery switch placement.

Nevertheless, I guess I have to pull the starter YET again. Dang, that gets old.

-- Edited by GonzoF1 on Monday 17th of January 2011 09:17:56 PM

How about just disconnecting the small wire that powers the solenoid. It sounds like the solenoid is staying energized through the start switch circuitry.

If you are determined to put a switch someplace so you can troubleshoot the system, put a small cheap toggle switch on that wire very near the solenoid.

Actually, Rick, that's what we THOUGHT was wrong last time. After replacing the $3 12V relay, it seemed to have fixed the problem. But no... it has resurfaced as the exact same problem. I now have extra relays and it was the first thing I tried this weekend. However, it appears to be a new problem. So, I have to assume that it might actually be the bendix sticking or something.

But that still leaves me needing a battery switch to de-energize the starter if it happens again. It's burning up my new starter and killing the battery. Neither of which are good things. Since I trust Chuck's input, I still want to know why to NOT put a switch between the battery and starter.

If you are just going to use the switch as a temp. solution a heavy knife switch would be the best. Not too expensive either.

If yanking the power leads off at the starter "cures" it, I don't see that it would be a stuck bendix. Wouldn't that remain engaged and continue making a racket? I would also guess it's a sticking solenoid, but I'm not clear on whether Gonzo actually disconnected the starter switch wiring at the starter as Rick B suggested, or, if he has, if that stops it. He mentions new relays, but that could still leave a problem at the switch/button or maybe an intermittent short in the wiring between the switch and the starter.

Maybe first pull the switch circuit wire at the solenoid and use a mutli-meter between the wire and ground. There should be zero volts between that and ground unless the ignition is on and the starter button is depressed...right? I would then have someone press the starter (ignition on) and see if I have 12-volts, and also if it immediately returns to zero when the starter button is released. If that looked OK, I would then try the same sequence with a load between the wire and ground using something near the same amperage as the solenoid. That should check to see if something in the wiring is somehow shorting under load. 10-amps would require 120 watts. I could see rigging up a couple of 60 watt car headlight bulbs wired in parallel.

If all that is OK, then I would change the solenoid (although I have no idea how to do that).

I'm no engine mechanic so if there's anything dumb in the above, please correct me.

Practical Sailor did great tests on rotary switches ,

and there is a HUGE difference between mfg. in terms of safe current carrying ability.

Gonzo, provided you use one of the rotary switches that is heavy duty enough you can have it in series with the starter motor. I have exactly that set-up and it works faultlessly. The PO did it as a hidden secret safety device I think for when he had it out on an unprotected mooring, as the ignition switch is a sick joke as any type of security protection. A screwdriver will turn it. It therefore gives me a separate way of isolating the starter motor from the starting batt, or selecting house or both if needed to start. I never have had to do that, but I could. The batt chosen by the main helm selector switch, (usually the house batt on there), therefore only activates the starter solenoid. Works for me, and has done for 10 yrs.

-- Edited by Peter B on Tuesday 18th of January 2011 06:23:40 AM

If your bendix is sticking it is not an electrical problem. If you want to put a switch between the battery and the starter and open it during one of these episodes, select one that you don't mind throwing away after one use because if the starter is remaining energized the switch will probably be destroyed.

Any switch you can afford to buy is designed to work offload, not while passing a heavy DC current.

There aren't that many trees in this forest.

Could it be an underpowered solenoid? Possibly a cheap one used by the guy who rebuilt the starter. Meaning, if it does not retract when the starter is engaged because of the pressure of the meshing gears, but does once voltage is disconnected when pressure is relieved. I know it's far fetched. Just thinking out loud.

Tom-

It doesn't work that way.

As Rick said, there is a good chance the switch would be destroyed. Chuck

To answer your original question.* Beware this is not my strong area.* *

*
We have a selector switch for the 8 D start batteries which is rate at 500 amps and the terminal are for ½ wire.* #4 wire is 13/32 and #2 is 15/32.* *We had an insurance audit which required 400 amps fuse be installed so the selector switch and wire are protected.* It takes a good battery to turn over a diesel engine, so clean the cable connections including the common negative bolt where the negative cables are bolted together which is usually down in the bilge close to the engines, and tighten all connections with pliers/wrench not just hand tight.* At most auto stores you can buy a load tester to see how much of a load your batteries are good for. ******


I installed a starter button in the engine room so I can see/hear/smell what is going on when starting the engines.* If the Engines to not turning over in 1 to 2 seconds and the engine does not start in 5 seconds then something is wrong.* I had the starter on the 671 rebuilt and it came back with an external solenoid in addition to the one built into the starter not sure why but it works.


Anyway you can protect the switches with high amp fuses.****If all else fails call a diesel mechanic which you will need at some time in the future.*In the long run it might be cheaper.***********


-- Edited by Phil Fill on Tuesday 18th of January 2011 05:13:30 PM

-- Edited by Phil Fill on Wednesday 19th of January 2011 10:13:46 AM

Why not just buy a new starter complete.**I can't see you getting to the wires in any reasonable time to disconnect them with out overloading the starter. *You may have ruined the old one by now. *If it does it then you know it is an electrical problem.* And the electrical problem is the key switch.* That is the only way the solenoid can be energized.

I'm thinking it is sticking or the current through it is causing the current to flow even after you let go of it.* As Rick has said there aren't many trees.

-- Edited by JD on Tuesday 18th of January 2011 05:18:57 PM

"Anyway you can protect the switches with high amp fuses."

No P/F, fuses won't protect the switch. I hope you don't do your own electrical work.

Opening the switch under a heavy DC current flow will create an arc that can destroy the contacts and their mounts and can start a fire. The current doesn't increase above what it was when the switch was closed so your fuses won't do squat. Even though the condition is intentionally induced, it is a form of arc fault and can be very destructive.

Please please please stop giving advice about things that are beyond your area of knowledge. You consistently advise people to do things that are either dangerous or can lead to a dangerous condition.

-- Edited by RickB on Thursday 20th of January 2011 06:21:36 AM

"No P/F, fuses won't protect the switch. I hope you don't do your own electrical work.

Opening the switch under a heavy DC current flow will create an arc that can
destroy the contacts and their mounts and can start a fire."

Fast acting DC rated fuses are designed to protect the entire system, including switches.* You can easily get proper DC block fuses up to 800 amps which will blow instantly when their rating is exceeded.* If the DC fuse is rated lower than the inrush or intermittent rating of the rotary switch the switch is protected and armaggedon avoided.* Here's the type I have:* http://www.amplepower.com/products/fuses/index.html

Rotary switches have stated amperage ratings, one for continuous and one for cranking or inrush current.* The 600 amp Blue Seas switch I use has a 10 second rating of 2,750 amps and is protected with a 500 amp block DC fuse.* Ample Power offers one designed as a starter disconnect with similar ratings and more compact design http://www.amplepower.com/products/switches/index.html.* Long before those switches have a problem, the fuse has blown or the wires have melted down.*

Good advice about not offering advice in areas "beyond your area of knowledge," but unless I'm missing something, what you said was correct Phil.

It still sounds Tom has a starter problem, so papering over it with switches and fuses (hatchets?) seems less direct than replacing the starter after making sure the starter switch is disconnecting properly, which you can check with a voltmeter on the solenoid while someone starts the motor.

"... but unless I'm missing something .."

Yes you are missing the fact that the current rating of the contacts on those inexpensive (even if they seem pricey) switches are not the current rating they can break or make. They are designed to operate under little or no current flow because they have sliding contacts and make or break very slowly compared to a solenoid. The first and last bit of contact is a tiny area and that is what starts the arc.

Even a start solenoid makes the contacts only under the load required to start spinning the armature. The heavy current occurs after the bendix engages and the cranking load starts, long after full contact area is made. The solenoid breaks the circuit after the bendix is spun off the ring gear and the starter is just spinning under no load, at minimum current and the entire contact area is separated nearly instantly. The fast acting nature of the solenoid allows the occasional failed start but even they weld themselves together sometimes.

A manually operated sliding switch does not provide the contact surface area of a solenoid at the instant of make or break so it is all but guaranteed to create a large and destructive arc when slowly switched by hand under load.

Neither of you seem to understand the difference between making and breaking a switch, particularly a DC switch conducting a heavy current, and the current carrying capacity of a static set of contacts.

Actually, I was thinking the other route to test it. By disconnecting the key switch and engaging it with a jumper, if the problem happens again, the key switch is not the issue. More than one way to skin a cat I suppose. Still, it WOULD be nice to be able to stop the motor from spinning should it happen again without the fireworks show of yanking the wires off the battery.

All you need is a short piece of wire between the battery lead where it connects to the starter and the solenoid. Disconnect the solenoid supply coming down from the start switch (at the solenoid) then jump between the battery lead and that terminal. The engine should crank. If it keeps cranking after you remove the jumper then it has been confirmed that your solenoid is bad, not the starting switch circuit.

Many installations are such that a long heavy screwdriver or pair of pliers will serve as a very good test jumper.

There is another side to this that you have to determine. You mention a shower of sparks. If the starter remains engaged because of a stuck bendix it will spin up but the current draw will be fairly low since the engine is driving it, not the other way around. The starter may well be de-energised already. The sparks (which none of us have seen so can't evaluate) could just be coming from the normal DC loads and the dying gasps of runaway alternator voltage.* Depending on where you take starting/charging control *circuit power off the battery it is possible that the engine quits when you remove the battery lead because the run solenoid is de-energised. The bendix then retracts and you are set up for another entertaining round of electrical antics.

-- Edited by RickB on Thursday 20th of January 2011 11:13:53 AM

Having a battery switch that can disconnect the battery in case of emergency is an excellent idea. I've had a starter hang up before.* I had 49 passengers aboard, and had no idea there was even a problem until one of them mentioned smoke coming out of the engine room.* Without a battery switch positioned OUTSIDE the engine room, there would have been no way to disconnect the starter without opening the engine room door, never a good idea when there is smoke indicating possible fire.*

On the other hand, using the switch to routinely disconnect the starter while trouble shooting may not be the best idea.* Doing so once or twice probably won't destroy the switch, but there are better ways to trouble shoot.** Also be aware that disconnecting the battery while the engine is running, runs the risk of blowing the diodes in the alternator unless there is a field disconect circuit on the switch.

My guess is that if you have pulled the small wire that energizes the solenoid, and the starter continues to spin, you've got a starter / bendix / solenoid problem.* Why not replace it?* I've seen new 6.354 starters on Ebay, as I remember for under $200.00.* I carry a spare, just because I have one from a core engine I bought to rebuild. My guess though, is that I'll never need it.

As for a battery switch, having one located OUTSIDE the engine room might some day be a life saver. Easyer to install is a remotely operated solinoid switch, I think Blue Seas offers a suitable one....................Arctic Traveller

"Yes you are missing the fact that the current rating of the contacts on those inexpensive (even if they seem pricey) switches are not the current rating they can break or make"

Blue Seas HD-Series switches Agency Standards:* UL Listed - UL 1107 Electric Power Switch Meets UL 1500 and SAE J1171 external ignition protection requirements, meets American Boat and Yacht Council (ABYC) requirements for battery switches.

Stop digging Rick.

I have reread this thread from start to finish. I can't seem to determine if the bendix is the problem or the starter motor itself.

I had a similar problem with a starter that was giving me problems. Sometimes it just would not start unless I beat on it with a hammer and *jumped it with a screw driver. Other times the bendix would just keep spinning.

It turned out that the shaft in the armature* as it sets in the stator had developed a flat spot where the magnetic force would pull the shaft against the stator and bind it.**we are talking tolerances in the microns

Testing the starter didn't show this because it would only happen when the flat spot on the shaft aligned perfectly with the wear spot on the stator.*

It wasn't untill a new armature was installed in the starter moter was the problem solved.*I had that starter apart so many times I know it by heart.

SD

I am pulling the starter tomorrow and bringing it home to goto a starter/alternator shop here in Raleigh. I already took it back to the guy that rebuilt it the first time. He bench tested it and said it was fine (and I trust him), but I feel like I need to get a second set of eyes on it. When I called the Raleigh shop, he was pretty sure it would be a rusty shaft. So we'll see next week if it helps.

Thanks for the insight SD.

I still would like to have a switch there somewhere, but I can't see that it wouldn't just toast the switch. And a blade switch doesn't seem very safe.

Tom-

Tom,
Anytime I install a new/ rebuilt starter I keep the negative cable loose enough to remove until I go through a few start cycles. Just in case it were to "hang in" as your is doing. I don't remember you saying if this happens while cranking over and continues to hang in after the engine starts.
You have studs and wing nuts. Maybe you could leave the negative wingnut off, have someone else start your engine while you hold the negative cable "levered" against the post by lifting at an angle. That way you can be sure the problem is solved.
I also suggest that you check the voltages to your starter WHILE spinning over. I usually would check these with the engine starting disabled. I am always looking for 10.5 volts at the battery post on the starter. And the minimum "switch wire" voltage I look for is 9.5 volts. Phil, the extra solenoid you saw installed on your starter was a "step up" solenoid. It is a way to assure 9.5 volts or more to the switch wire. Instead of the switch wire voltage source tracking through the harness, key switch and neutral safety switch before energizing the pull in coil on the starter- the switch wire leaves the neutral safety switch and then triggers the step up relay. The step up relay then connects the battery post on the starter with the switch wire terminal on the starter. Instead of 20' of wiring and several voltage drop potential areas, it shortens the circuit to about a foot. Hope this makes sense- it might be easier to draw out