electrical expertise / input needed re battery disconnect / alternator / Smart Start

[Outfitters]

I bought a challenged 1986 M998 in July. I have installed a new 210 amp Niehoff dual volt alternator N1387 Alternatorwith N3225 Regulator(with 200 amp conversion kit)(was 60 amp), cleaned all major electrical connections, added new grounding harness, Nartron Smart Start System (with new yellow banded Glow Plug Controller), and new glow plugs. It is now starting and running great!
I also added a basic keyed battery kill switch on the negative side (Wirthco Rated 50 amps continuous 250 amps surge at 24 volts) for ensuring a stranger or thief cannot start my Humvee. I am planning on swapping that for a Pollak 51-916 to correct the under amperage rating (the Pollak is 185 amps continuous and 1000 amps surge.....but after looking at the Pollak 51-919 (it adds an alternator generator field circuit - designed to break alternator generator circuit prior to battery circuit disconnect) I have questions/concerns...

1. Does adding a battery disconnect on the negative side have potential risks? I am concerned that an over amperage meltdown of the battery disconnect switch while driving will result in a fried alternator and or regulator since the alternator power output will not have a complete circuit...

2. Does the negative side of the batteries that are connected in series carry amps the same way as the positive side? Example: when the glow plugs are heating is the negative side of the batteries that are connected in series carrying the same 100 ish amps as the positive? Is the starter amp load to the negative side of the batteries equal to the positive? Is the upgrade to the above mentioned Pollak needed to put the amp draw within or near specs of the battery disconnect switch?

3. What is the standard "cycling time" for the Niehoff alternator at engine shut down? Should I wait a certain amount of time after engine shutdown to use the battery disconnect switch?

4. What is the standard "Cylcing time" for the Nartron Smart Start System at engine shut down? Should I wait a certain amount of time after engine shutdown to use the battery disconnect switch? I think I read that if the running lights are left on the Smart Start System does not completely shut down until they are shut off....I always switch all accessories to off before engine shut down.

5. Does the 12 inch lead from the batteries to the disconnect switch need to be zero gage like the other leads? or is 1 gage ok?

I may be over thinking this but I my ocd tendencies require I get it right.

Thanks in advance for your timely replies.

 

[Action]

Why not put a kill switch between the batteries and the start switch? It wouldn't have to be so big. It wouldn't kill power to everything, though.

 

[NDT]

That 50 amp switch is subject to a meltdown, it is severely undersized, I would remove it. Yes, the same number of amps travel through the negative as the positive.

 

[papakb]

In an electrical system where you have 2 batteries in series all of the wiring shares the same current so all of your wiring in that area should be the same gauge wire. Installing a battery disconnect switch anywhere in that series loop whether it's on the + side or the - side of the batteries will carry the full current load so again the disconnect switch needs to be rated for the maximum current you expect to see. Most engineers will overrate that by at least 20% for safety reasons so your 250 amp switch should be fine.

Kurt
KG6KMJ

 

[ColonelSanders]

Consider that if you want to bypass your kill switch, it is easy on the negative side, just a wrench to the frame would do it. If you install on the positive side it makes it that much harder to go for joyrides.

+1 on the meltdown. Best case it stops working, worst case is you have a nice electrical fire

 

[mechanicjim]

For the Niehoff once it looses power on IGN it will not produce power as the Regulator with turn off the field coil. Basically just don't disconnect batteries while the Alt is "Running" (power to IGN and Rotating at needed RPM).

 

[rchalmers3]

Removed for thread clarity.

Rick