Does Generator Charge Bus Batteries??

[Jon Wehrenberg]

Bruce,

It sounds like you have the apples mixed up with the oranges.

I will be doing a seminar on this in Spearfish, but the short version is your bus batteries are not getting charged while your engine is off regardless of how long you run a generator or if you are connected to shore power unless you have a battery charger dedicated to the chassis batteries, and it is turned on.

The house batteries are charged automatically when the engine is running, when connected to shore power and when the generator is running because your inverters are on all the time and when the engine is running the alternator is charging them.

[truk4u]

Jon - My CC and the previous Marathon is like yours, it can set a long time with no problem and still have 24 + volts and I never turn off any of the switches. I suspect some of these with short chassis battery life when the switches are off is caused by a bad battery(s). One weak cell can drag down the group in short order. Even new batteries as we know can be bad.

Bruce - Letting the charge get to float assures you have put a full charge back in the batteries and the next cycle of use will last as long as possible. If you cut it off during absorbtion, your not getting a full charge. I experimented a little with this and it makes a difference. Also, remember 12.2 volts is 50% discharged.

[0533]

Jon - My CC and the previous Marathon is like yours, it can set a long time with no problem and still have 24 + volts and I never turn off any of the switches. I suspect some of these with short chassis battery life when the switches are off is caused by a bad battery(s). One weak cell can drag down the group in short order. Even new batteries as we know can be bad.

Bruce - Letting the charge get to float assures you have put a full charge back in the batteries and the next cycle of use will last as long as possible. If you cut it off during absorbtion, your not getting a full charge. I experimented a little with this and it makes a difference. Also, remember 12.2 volts is 50% discharged.

Thanks Tom,

I will wait until it floats before turning off the genset.

I had new Chassis batteries installed in Coburg last December, who knows one may already have bad cells, how do I check for this with sealed batteries??

[Jon Wehrenberg]

This is a comment to all and relates to Bruce's concerns.

Our batteries are our lifeblood and because of that we need to treat them with respect. At the very least all owners should go to various sites such as these:

http://www.lifelinebatteries.com/rvbatteries.php

http://www.windsun.com/Batteries/Bat...ting%20battery

The important thing is to understand batteries, how to charge them, and what impacts their life.

The next step obviously is to get to know your coach. How is your inverter set up for charging? What is the charging voltage of your alternator? Do your batteries hold a charge or are they losing a charge? If they are losing a charge why are they losing a charge? Putting on a charger to compensate for batteries going dead is akin to taking an aspirin for a brain tumor. It masks the underlying problem.

To address Bruce's question specifically, there is a simple way to determin if you have a bad battery. Separate the batteries electrically (take the cables off them) and using a battery tester check them to see if they are just in need of a charge or if they have gone bad. In the absense of a tester, there is another way, but it will be inconvenient if you are living in the coach. Separate the batteries electrically. Measure and record the battery voltage for each battery. Do not reconnect the batteries or use power from them, but let them sit overnight. Remeasure the voltage after a 12 or 24 hour period. If you have not pulled any power from them they should have retained the voltage measured the day before. A bad battery will show a much lower voltage.

In the case of chassis batteries this should be no problem, but if your house batteries need to be checked you really can't use the second method if you are using the coach.

I will maintain my original position on this. If the chassis batteries are losing a charge within days or even a couple of weeks there is something pulling them down. As Tom points out it could be a bad battery or there is a load on them that needs to be determined. There should be no loads with the switches turned off except possibly some DDEC circuits. Those circuits should have minimal current draw, if any.

[truk4u]

Good advise from Jon, but be sure you test the batteries with a load tester, not just a meter.

[Ray Davis]

I may be on the wrong tack here, but the Marathon coaches have a control panel to set the charging rate for the house batteries. I know this affects the incoming shore power, in case you are connected into a 20 or 30A service.

What I don't know for sure, will that affect the charging rate, if the genset is running. IF so, then perhaps your charging rate is set too low, and you're not coming up to charge in the time you're running the genset?

Ray

[Jon Wehrenberg]

This is a tough place to get into a deep discussion, but Ray's comments are also on the right track. If the generator is set for auto-start the house batteries should get a full charge before it shuts off. If the coach is used for a lot of dry camping that means the charge rate on the inverters needs to be set to its maximum.

But if the coach is used for a mix of dry camping and full hookups then when connected to shore power it is probably the lowest charge rate needs to be selected otherwise power management becomes an issue. When using low amperage hookups like 20 or 30 amps a high charge rate will likely result in tripped shore power breakers if any other devices are used such as AC units.

Note however this has nothing to do with a chassis battery issue. Shore power, generator power, or no power should have zero affect on the charge of the bus batteries unless the coach has a chassis battery charger and it is turned on when using shore or generator power.

[0533]

My friend next door to me (the Michelin factory manager) has a portable bank of solar panels that he can position for the best sun location, each one produces 80 watts, X 3.

has anyone considered this method for either house or chassis battery charging. I mean on a larger scale, not as a trickle charge, but with an array of panels with lets say 1,000 watts, would this have any real benefit when dry camping and how would one connect it to the coach grid?? Like to come up with a way to beat the genset requirement.

[Jon Wehrenberg]

Let's say your refrigerator uses 7 amps. That is 840 watts.

My guess is that the array of solar panels just to keep pace with the most basic loads would need to provide 1500 watts because on our coaches we have a lot of "key-off" loads ranging from tank level sensors, to the alarm system, to clocks, outside thermometers, to the water pump etc.

Of course you could get away with less wattage if you set your charge time to the night when loads are less.

[0533]

Let's say your refrigerator uses 7 amps. That is 840 watts.

My guess is that the array of solar panels just to keep pace with the most basic loads would need to provide 1500 watts because on our coaches we have a lot of "key-off" loads ranging from tank level sensors, to the alarm system, to clocks, outside thermometers, to the water pump etc.

Of course you could get away with less wattage if you set your charge time to the night when loads are less.

There is a lot of load for sure, but with the cost of fuel and the hassles it is a subject worth investigating. I will do some research and report back. I have to believe there are solar options sized and large enough to meet the the demands of our buses.