MrTransistor
Senior Member
Hello hdvectra,
John hit the nail on the head with the ˜wonky contacts'. Having not used the engine for a while, the contacts will develop a very thin oxide coating that acts as an insulator. The first time your coach was fired up, the contactor pulled in but didn't tie the battery banks together because of the oxide coating. Exercising the battery boost switch (with engine off) a few times causes the contacts to make and break and will ˜punch' through the oxide layer and make contact as designed. That's why silver contacts are better. Not that they don't develop an oxide coating but being softer, the mechanical force of the contacts closing every time is enough to break the oxide layer. All relays and contactors should use silver contacts! But then there is the price.
This procedure (getting the tie contactor working) ultimately is much safer than putting a jumper between the battery banks. Depending on the state of charge of each bank and the current available from the engine alternator, there could be a pretty high current flowing in your jumper. If the size of wire is not adequate for this current, then the wire could overheat. What I do is, just after engine start and while I'm waiting for the jacks to retract and air bags to inflate, go to the One Place and check that I have better than 13.1 Volts on both the coach and chassis batteries. That tells me the tie contactor did connect the banks together. If there is say 12.8 Volts on the house batteries and 13.4 Volts on the chassis batteries, then I know there was a contact fault on the tie contactor. If that happens, shut down the engine, press and release the Battery Boost Switch a half dozen times, then fire it up again. This only seems to happen if we've been sitting for an extended period. Once I have cleared the contacts, it will work properly for the entire trip.
I would suggest that you install something like a Xantrex Echo Charge. That way you don't need to run the engine just to charge the chassis batteries and this is much safer than using a jumper. Keeps the banks isolated as well. A jumper could mean that all your batteries go dead instead of just the house or the chassis in case of a fault.
John hit the nail on the head with the ˜wonky contacts'. Having not used the engine for a while, the contacts will develop a very thin oxide coating that acts as an insulator. The first time your coach was fired up, the contactor pulled in but didn't tie the battery banks together because of the oxide coating. Exercising the battery boost switch (with engine off) a few times causes the contacts to make and break and will ˜punch' through the oxide layer and make contact as designed. That's why silver contacts are better. Not that they don't develop an oxide coating but being softer, the mechanical force of the contacts closing every time is enough to break the oxide layer. All relays and contactors should use silver contacts! But then there is the price.
This procedure (getting the tie contactor working) ultimately is much safer than putting a jumper between the battery banks. Depending on the state of charge of each bank and the current available from the engine alternator, there could be a pretty high current flowing in your jumper. If the size of wire is not adequate for this current, then the wire could overheat. What I do is, just after engine start and while I'm waiting for the jacks to retract and air bags to inflate, go to the One Place and check that I have better than 13.1 Volts on both the coach and chassis batteries. That tells me the tie contactor did connect the banks together. If there is say 12.8 Volts on the house batteries and 13.4 Volts on the chassis batteries, then I know there was a contact fault on the tie contactor. If that happens, shut down the engine, press and release the Battery Boost Switch a half dozen times, then fire it up again. This only seems to happen if we've been sitting for an extended period. Once I have cleared the contacts, it will work properly for the entire trip.
I would suggest that you install something like a Xantrex Echo Charge. That way you don't need to run the engine just to charge the chassis batteries and this is much safer than using a jumper. Keeps the banks isolated as well. A jumper could mean that all your batteries go dead instead of just the house or the chassis in case of a fault.
