Jumping engine battery with coach battery?

[jbkoonse]

Just wondering for peace of mind. If the engine battery is low and won't provide a good crank, can you jump start it with a charged house battery? Thanks!

 

[lavarock1210]

If you do first connect the batteries and wait at least 10 minutes before you try to start the engine. 

 

[Jammer]

Yes.  Some rigs have a button you can push to make that happen without using jumper cables.

 

[Jammer]

If you do first connect the batteries and wait at least 10 minutes before you try to start the engine.

Oh yeah, and use a surge protector, you know, just to be sure there aren't any surges.

 

[RV]

Oh yeah, and use a surge protector, you know, just to be sure there aren't any surges.

I don't get this... are you guys just kidding around?

 

[Jammer]

Um.  Yes.  I thought that was obvious, sorry.

There's no need to wait 10 minutes, just as there's no need for surge protectors.  But, in both cases, do it if it makes you feel good.

 

[RV]

Ya got me on that one.....

 

[jbkoonse]

Yes.  Some rigs have a button you can push to make that happen without using jumper cables.

Oh, I have that button but have never known exactly what is was for. It says "Emergency Start." Does it draw the power from the coach battery when pushed?

 

[Jeff Brown]

Mine says Battery Boost, but yes that is what that button does.  It can be a life saver!

Jeff

 

[lavarock1210]

There is a good reason to wait 10 minutes before you start the engine.  The fact you are jumping the engine battery I made the assumption that the engine battery was dead.  If you wait the 10 minutes it will allow some charge to be transferred to the dead engine battery.  If you do not wait you risk reversing a cell in the dead battery which will ruin the battery.  Also if you wait your chances of starting is increased many fold as the dead battery now has some charge and the current that will have to flow in the jumper cables will be less.  You may get buy with 5 minutes but I have had better luck with 10 minutes. 

 

[jbkoonse]

Thanks for that!

 

[99WinAdventurer37G]

And with diesels it may take a little longer.  I've let mine run for 15 minutes and still not crank.  It depends on "how dead" they are.  Diesel starters need a little more juice.

 

[Jeff]

I have followed Freightliner's directions for usng the boost start and have never seen anything about waiting 10 minutes. Engaging the start relay provides coach battery power to the cables of the start batteries which should transfer power to the starter.

If my coach batteries are getting low from sitting I start the generator first to put a charge back on them. Its always worked for me on our last 4 coaches.

 

[Weewun]

I have to agree with LavaRock, If you have a badly depleted Chassis Battery(s) and jump it with either the Boost Switch or Jumper Cables You may not get enough current to the starter as it is passing thru the Chassis Battery trying to charge it (Current takes the path of least resistance which is the deeply discharged battery).

It is best to wait a couple of minutes until the Chassis Battery gets some charge, 10 minutes seems excessive the longest I have ever waited is 5 minutes maximum.  If the Starter will not turnover after 5 minutes you probably have a shorted Chassis Battery in which case I disconnect one lead off the Chassis Battery and use the House batteries by themselves.

 

[lavarock1210]

I did state you may get by with 5 minutes.  But remember you will probably only have one try.  If it does not start after 5 minutes or even after 10 you will be spending hours finding a battery charger or talking someone into jumping with their rig.  I will not jump start with my truck battery.  The risk of something going wrong is to great in my book.  I have seen the tops of batteries come off because someone crossed the jumper cables. What is an extra 5 minutes?

 

[scottydl]

I jumpstarted my MH battery with a "regular car" numerous times.  It's the same type of chassis battery, at least on my rig... I don't see what would make it any more dangerous than jumpstarting another car.  I agree that letting the dead battery "charge" for 5-10 minutes (or even longer) while hooked up to the cables is a good idea and makes the process easier.

I have seen the tops of batteries come off because someone crossed the jumper cables.

That would be a user error, due to either negligence or ignorance of using the cables... not really a symptom of car-to-MH jump starting.

 

[jbkoonse]

Now I do remember trying the "Emergency Button" earlier. It only causes a noise that sounds like a solenoid clicking , no engine crank. So I guess that I get to investigate this...

 

[tswms]

Last year on the trip to FL my alternator went out and the battery went dead . The engine stalled on the bypass in Dothan GA. I carry a jumper cable in the toad, I got it out in traffic, and used it to jump from house to chassis battery.(Both are located up front under the hood) I left it in place and was able to get started and drive to a repair shop on the house battery.

 

[Just Lou]

Now I do remember trying the "Emergency Button" earlier. It only causes a noise that sounds like a solenoid clicking , no engine crank. So I guess that I get to investigate this...

You need to learn how the emergency start switch and solenoid work.

Pressing the switch only picks a solenoid which connects (jumpers) the chassis and house batteries together.  You have to hold the switch depressed and crank the engine in the normal fashion with the ignition.

Hold the switch depressed for as long as you think necessary to transfer charge to the chassis battery before trying to start the engine.  I generally do it all in one motion.

BTW - before everyone gets their undies in a knot, the OP did describe a low battery situation, that did not provide a good crank, not a completely DEAD chassis battery.

 

[jbkoonse]

You need to learn how the emergency start switch and solenoid work.

Pressing the switch only picks a solenoid which connects (jumpers) the chassis and house batteries together.  You have to hold the switch depressed and crank the engine in the normal fashion with the ignition.

Hold the switch depressed for as long as you think necessary to transfer charge to the chassis battery before trying to start the engine.  I generally do it all in one motion.

BTW - before everyone gets their undies in a knot, the OP did describe a low battery situation, that did not provide a good crank, not a completely DEAD chassis battery.

You are correct re: battery status; low, not dead. Bought unit used and it had no manual.  Thank you for the directions on emergency start switch! much appreciated!