Guest Automatic 5/10 Amp Charger

[Jon Wehrenberg]

I'm already seriously confused.

I thought the trip to Prevost to replace the isolator cured that problem.

There is something wrong, wrong, wrong.

[0533]

Jon: Lets review why this occurs on Marathon single alternator setups, which is my case.

My regulator gets its signal for the need for alternator power (single 270 amp alternator) from the house side. The regulator senses its need to deliver a charge from the house side. The electrical connection has been MOVED by Marathon from the 12/24 volt chassis switch at the drivers side rear door entry (where we all turn off the chassis side) to the house side shutoff just above at the same door location. Therefore when the generator is on, or the shore power is on while the engine is running the regulator will not sense a need for a charge as the house batteries are getting their charge from the generator or shore A/C power. therefore no charge will be sent to the chassis batteries regardless whether they are needed. This would only occur in this event, no problem when GEN/Shore is off.

The thought at Marathon was to provide the owner with a way to operate the bus using only the 270 AMP alternator to charge the house batteries without the need for the Gen/shore A/C source charging the house batteries keeping the house batteries charged at the proper levels saving fuel and the gen hours for use only at a dry camping situation I guess.

It is a pretty simple system if you view in these terms. The problem comes in if you find a need to run the generator while driving down the road. This will cut off the charging cycle to the chassis side.

So with this in mind, I use my OTR air while running along and rely on the alternator to charge the house batteries when the regulator senses a need.

I would be curious to know how Liberty handles this situation, especially when the coach is running down the highway without the GEN on and a load on the house batteries. What senses in this case, I guess if you have the inverters on auto start this would accomplish the same goal. How are other Marathon single alternator setups installed.

In my case, all I would have to do would be to move the wire from the regulator from its current location (House shutoff) over to the chassis shutoff, very simple change over.

PS> The isolator was a separate issue from this and it is solved. The Guest charger is only for charging the batteries while it sits for extended periods, nothing to do with any operational charging issues. my chassis batteries get a full charge while running down the road when the alternator is functioning.

PSS> If the regulator senses a power need from the house side, how would it function any other way than what I have presented??

[phorner]

Bruce,

Our Liberty set-up is pretty simple. There are 2 alternators. One handles the house batteries, the other the chassis batteries.

If either alternator fails, or both for that matter, (with the Guest charger installed) I can run the generator and still charge the batteries through the inverter/chargers.

I am at a loss regarding your system.

Wish I had more to offer you.....

[phorner]

Also, Bruce,

Your post makes it sound as if your single alternator senses only the house batteries while running down the road, and sends charging current accordingly.

If that is the case, how do you ever charge the chassis batteries? Under what conditions does your alternator send charging current to your chassis batteries as opposed to your house batteries?

[jack14r]

On my 2001 Marathon the OTR was wired to the house batteries with a 270 amp alternator charging them,the coach batteries had a 100 amp alternator charging them.On both Liberty's I have owned there is a single 270 amp alternator that will charge the coach or house batteries,also the OTR is wired to the coach batteries.I don't know how the sensing works but at times I can see on the gauges both sets of batteries being charged at the same time.

[Ray Davis]

So Bruce, if I understand what you're saying with regards to Marathon moving where the system senses the voltage to determine how much charge to provide out of the alternator, it would seem that any of us with a Marathon coach should be able to test this, and note battery voltages both with and without generator when running the engine?

I'll try to remember to make that test next time I'm out in the bus.

Ray

[Jon Wehrenberg]

Bruce........

Lets get basic here for a minute.

Your 24V alternator charges the entire coach when the engine is running. The alternator sends current through the isolator whose sole purpose is to prevent one set of batteries from pulling down the other set of batteries. In your coach and mine we can have the house batteries fully discharge, and the chassis batteries will still have a full charge, or vice versa.

Your 24V alternator voltage regulator has been set up to sense house current. There may have been a reason for that, but as you now know that reason was ill conceived. If you want you can go the expensive route and put in a second alternator, with a second regulator and increase the chances of a regulator or alternator failure in the future.

If you want to cure the problem you have with the chassis batteries not getting any charge when the bus engine and generator are running the solution is simple. Take the sense wire off the house circuit and instead sense the chassis batteries. In that way the problem goes away.

I don't know your coach. I don't know what loads you can have on the house batteries while you drive, or what conditions you determine are necessary to run the generator. None of that matters. If you want to end you problem I can talk you through making one wire connection to make your problem go away. By making this change you can get experience with it and determine if it makes the problem you are having go away, or if it transfers the issue to the house curcuits or if there is another piotential problem I am not anticipating.

Paul has a 12 volt house and a 24 volt chassis so his use of 2 alternators is because he is charging two different voltages. He has true bus air (some call converter installed AC bus air but it is not Prevost OTR with heavy DC loads) so he needs to have the big alternator, but his house battery system is a three battery in parallel set up making it an ideal candidate for a second alternator.

[Ray Davis]

Correct me if I'm wrong here, but at least with my Marathon's, they are wired such that the while driving the inverters can each run one A/C. This is assuming that the alternator is charging the house batteries while driving.


So, perhaps this makes an assumption that you should rarely need to run the generator while driving down the road, i.e. you should have dash air, and up to two cruise air or roof airs available from the engine. An A/C select button allows you to chose which A/C on an inverter is actually powered up.

Obviously, you could still run the generator, but perhaps that would cause the lack of charging to the coach batteries. I would think that if you limit the generator use in this case, then perhaps that was an intended trade-off?


Ray

[0533]

Also, Bruce,

Your post makes it sound as if your single alternator senses only the house batteries while running down the road, and sends charging current accordingly.

If that is the case, how do you ever charge the chassis batteries? Under what conditions does your alternator send charging current to your chassis batteries as opposed to your house batteries?

The regulator is sensing the house load, and directs the alternator accordingly.

The regulator is adjusted to a Max Output of 27.

There is an isolator and equalizer. The chassis batteries will receive an equivalent charge up to the Max Output of the regulator I believe.

There is only one sensor from the regulator on all Prevost car regulators, it simply depends on where you place the sense wire. In this case its the house side (not through the inverters i might add) but at the Main shutoff in the back of the bus.

[0533]

Jon: let me answer in your text copy below.

Bruce........

Lets get basic here for a minute.

Your 24V alternator charges the entire coach when the engine is running. The alternator sends current through the isolator whose sole purpose is to prevent one set of batteries from pulling down the other set of batteries. In your coach and mine we can have the house batteries fully discharge, and the chassis batteries will still have a full charge, or vice versa.

Yes the alternator will charge both the house and Chassis at the same time (as long as the genset or shore power is not on)

Your 24V alternator voltage regulator has been set up to sense house current. YES There may have been a reason for that, but as you now know that reason was ill conceived. If you want you can go the expensive route and put in a second alternator, with a second regulator and increase the chances of a regulator or alternator failure in the future.

I have considered this option or to simply move the sense wires back to the chassis side and forego the alternator.


If you want to cure the problem you have with the chassis batteries not getting any charge when the bus engine and generator are running the solution is simple. Take the sense wire off the house circuit and instead sense the chassis batteries. In that way the problem goes away.

Yes I agree But I sort of liked the idea for a while as it seemed to offer a solution instead of using the generator. I must admit that sometimes I do not like running my genset because the exhaust is on the roof and leaves a mess sometimes, especially if it rains after a long genset usage. The benefits of having the exhaust on the roof probably better overall. Different issue.

I don't know your coach. I don't know what loads you can have on the house batteries while you drive, or what conditions you determine are necessary to run the generator. None of that matters. If you want to end you problem I can talk you through making one wire connection to make your problem go away. By making this change you can get experience with it and determine if it makes the problem you are having go away, or if it transfers the issue to the house curcuits or if there is another piotential problem I am not anticipating.

Thanks, I assume it is to simply move the regulator wire to the chassis main shutoff?? If so I might well do this, and set the genset back to auto start again.

Paul has a 12 volt house and a 24 volt chassis so his use of 2 alternators is because he is charging two different voltages. He has true bus air (some call converter installed AC bus air but it is not Prevost OTR with heavy DC loads) so he needs to have the big alternator, but his house battery system is a three battery in parallel set up making it an ideal candidate for a second alternator.

I understand. Ours is a marathon OTR, smaller works well uses less juice.

Thanks Jon.

I am surprised by this type of install, have asked Marathon Coburg to confirm this, both Marathon Fl. and Prevost Car showed me this install and Marathon Fl concluded that it was the way it was originally setup, there are in fact Marathon #'d wires attached to the Prevost regulator wires. I have to believe there are other Marathon setups like this???
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