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Author Topic: Jump Start Relay / House Battery Charge  (Read 2525 times)
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82, Model 10 8v71, 95 Model 15 60 Series

« on: February 03, 2007, 02:59:07 PM »

If all goes well, I have attached 4 pictures to the post and question.   I'm new to the bus and to posting on this site.

I  have attached the following photographs, My complete 3rd bay, a closer view of the electric panel, a close up of the Jump Start Relay. and my inside control panel. 

I'm not sure if the system works yet, does anyone else have this setup. 

I've been reading about isolators and solenoid relays to split the charging from the alternator to keep the house batteries charged.   I would like to know or make sure I can charge my house batteries while going down the road, and let the family run the inverter or 12volts items without fear of discharing the batteries.

This raises my question, will this jump start relay, also back feed power from the starting batteries to charge the house batteries if engaged while the bus is running. (I haven't traced the wires just yet, I assume its feeds back to the start batteries.)

As you can see on my control panel, I have a switch to engage the Jump Start.  I also have a battery charger switch (not sure what it runs to at this time).  (I have 2 displays for my generator volts/shore power, a invertor volt display, and dc volts display to help me monitor.  The relay seemed a little small to me, but I'm no electrician.   Any thoughts on this set up is appreciated, and any thoughts whether I need a seperate solenoid to charge from my alternator.  I'm getting ready for summer, and would like to run 1 roof top air unit off the inverter on the hot days.

I just need to spend about 3 hours with someone that knows buses.  As always, Living and Learning as I go. 
Hope the pictrures help.

Evan / LegalEagle82

Legal Eagle
Nashvile, Tennessee
82 Model 10 8v71
95 Model 15 60 Series
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« Reply #1 on: February 03, 2007, 06:37:05 PM »

Hi Evan

It is hard to tell you what you have with out seeing it live. If there is 2 switches my guess is that you have 2 relays. The switch that says " Jump Start " energizes a momentary on or " starter relay " to combine the batt. banks for emergency start. The switch that says " Batt Charging " energizes a constant duty solenoid to allow alt output to the house bank. It should be easy to confirm with a volt meter at the batt banks.

Good luck, Duane

Remember, anythingís possible itís just iron, well, almost.
Tom Y
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80 5C With Cummins L10 in Progress

« Reply #2 on: February 04, 2007, 05:58:03 AM »

I read your post last night and went to repond today, ended up on the wrong post.  Look at the battery isue one.  Never claimed to be the sharpest tool in the shed.  Tom Y

Tom Yaegle
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Pete RTS/Daytona ->'89 TMC 35' 102" 6V92TA 4:10


« Reply #3 on: February 04, 2007, 09:49:16 AM »


One solenoid to connect your house and vechicle batteries together - seems a little small
many solenoids are only 80 AMPS continuous - others are 200amp continuous and 400 peak


Remember - there can be worst case conditions like -->
<>50DN alternator is capable of putting out 250-270 amps on full charge
....so if your house batteries go dead and you start the engine - that's a lot of amps thru that solenoid
<>The starter can pull even more than that when starting
....If you have a boost switch that brings up the solenoid to boost dead vechicle batteries - that's big amps thru the solenoid

The system i'll be using will use (qty 2) 12volt - 200 amp/400 amp solenoid with the outputs in parallel -  and  the pickup coils wired in series so if one solenoid coil fails neither will energize (safety feature)

the solenoids can get energized by:
<> 24 volt engine run circuit  or use the 50DN "R" terminal 12 volt signal to energize a small cube realy to send 24 volts to the solenoids - (so as long as the engine running -  both batteries sets are charging) -

<> 24 volt dc from a small transformer (wall wart) thats plugged into my "pole Power" line (so both batteriy sets  get charged when plugged into shore poweer

<> 24 volts from the manual (spring loaded) "battery Boost switch on my dash" - to manually conbine the batteries during emergency starting

Pete RTS/Daytona

If you ain't part of the solution, then you're part of the problem.
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« Reply #4 on: February 04, 2007, 11:04:37 AM »

I used the same jump relay as you did (what looks like the old Ford starter relay).  Couple of points- my bus is 12v and has a 300amp 50DN alternator.  The relay I am using is 150 amp continuous duty.  What I did was to use two of them so to have 300 amp capacity, used a heavy metal strap to bolt them together to have them in parallel.  They have been 100% reliable.  I have it wired to an on-off-on toggle on my dash.  One way is that it is wired through the ignition switch so it activates when the engine is running.  The other way is wired through the deep cycle batteries for manual use in case the starting batteries go dead, it can still activate and help start the bus with the deep cycle batteries (and it has been used).  I have my gen starting also through my 2 engine starting batteries.  If the starting batteries go dead, I can flip the switch to the deep cycles and at least start the gen to charge the batteries.  Also, if the deep cycles have gone dead (this too has happened-left something on), I can flip the switch to ignition side, turn on the ignition and the inverter/charger will reactivate if plugged in (inverter has to have 12v to start working-sort of strange).  I have left the relay activated for several weeks on end by accident and they still work well.  Be sure to get continuous rated relays.  Good Luck, TomC

Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
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