| Author |
Message |
Jerry (205.188.209.11)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, February 24, 2003 - 7:07 pm: | |
I’d like to put in a battery disconnect switch(s) for both the “coach” (engine starting and other vehicle systems) and “house” batteries battery systems. And, until I can get to that part of the priority list that says I can now spend the $ on an automatic solid state isolator or paralleling relay (so that both sets can be charged from the one engine generator) I want the capability to manually parallel both battery sets for charging. I have two of those four position (selecting battery 1,2, both, or off) battery switches one is rated at 360amps continuous 600 amps momentary that I will use – more than enough capacity for charging (the 4106 has a 225 amp generator) or other current or anticipated loads – except possibly the starter. The question is can / should the starter be switched? How many amps does a 12V starter draw for a typical 8V71 during starting (which will answer the question if I have an adequately rated switch to switch the starter)? Thanks - Jerry 4106-1750 |
Henry R. Bergman, Jr. (Henryofcj) (65.194.145.47)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, February 24, 2003 - 8:21 pm: | |
Would suggest that you leave the actual starter circuit out of your excellent plans. I also am going to install a disconnect switch an E-mail buddy got me for my Crown.
How powerful is a 12 volt starter and how many amps could it draw/pull while cranking your mighty Detroit? A bunch. A switch capable of handling such amperage would be very big and ....
....heavy...thus limiting where it phyically would be mounted on the coach. I want to put my switch near the starting batterys as a failsafe disconnect. While somewhat close to the starter....
....it would probably not be close enough to be efficient. Therefore I plan on NOT including the starting motor circuit in my scheme, but only the starting relay. Not the starter itself. Good luck. Henry of CJ. |
Tom Caffrey (Pvcces) (64.114.233.40)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, February 24, 2003 - 9:49 pm: | |
Jerry, another side of the argument about whether to switch the starter is that, on occaision, the starter solenoid contacts can stick enough to keep the starter powered up, even after the engine is running.
In that case, including the starter in the battery switch circuit will make disconneting it a lot simpler. AFAIK, the main reason that the contacts stick is insufficient battery power, so including the starter in your switched circuit could slightly increase the risk of a stuck contact.
However, if you should ever experience a stuck contact in the solenoid, you may find that the time it takes to unhook your batteries is enough to fry the starter, so I think I would go that route.
When I checked our cranking current on our Link 2000, it was only about 400 amps. The weather was moderate and the batteries were up. If anything should cause the engine to crank more slowly, such as low batteries, cold weather, wiring or engine problems, the current will rise.
If you're the kind of person who does *not* continue to crank your engine if you have low batteries, you shouldn't have any problem with switch capacity. Having plenty of cranking power is one of the best ways to safeguard your starting system.
For what it's worth.
Tom Caffrey PD4106-2576
Suncatcher |
John Clark (Jvc) (205.188.209.11)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, February 25, 2003 - 3:58 am: | |
Hi Jerry,
One thing about this board is you will get a lot of opinions, and they are probably all correct. An 8V92 starter can pull over 1800 amps, so I imagine an 8V71 can require well over a 1000. I have tried the isolator route and the solenoid route with mixed results. The marine industry has been working with this problem for years and their most recent solution has worked very well for me. Forget the isolator and use a Heart interface echo charger for your start batteries. Put everthing else on your house batteries and you eliminate the need for solenoids, isolators and human input (very important to us old fogies). My start batteries are connected direct to the starter with a normally open disconnect switch connecting them to the house system. I have yet to activate the switch (two years and counting) and the system has worked fantastic. Good luck jc |
FAST FRED (209.26.115.116)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, February 25, 2003 - 5:37 am: | |
Another aproach is to contemplate how many times this will be needed.
If your like many big batts are needed but a complete seperate system might not be.
One simple solution is to get a disconect from an MCI or some transits and only disconect the house when its needed.
Some can be cable operated , so you don't even have to open a bay.
Advantages ,
the coach disconect was made to start thru,
the house batts WILL help you start in most starts and do keep the voltage from going down on a 2 or 3 try cold weather start,
a simple solenoid (big amps) and the ACC terminal of the key start switchwill automatically combine the sets , should you forget to combine the systems some AM.
Disadvantage , if you go someplace for a few days and havent seperated the systems , you could end up dead.
So just put the switch on your parking check list.
FAST FRED |
nuts (66.123.253.71)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, February 25, 2003 - 8:15 am: | |
http://www.westmarine.com/webapp/wcs/stores/servlet/WestAdvisorDisplayView?advisor=464-465.htm |
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