Gen Batteries Dead?

[jmgrigsby]

I recently had my MH in the shop from about 4 weeks. When I got it we had to jump start the engine. It's been plugged into 110 volts for 24 hrs at home. But I discovered that the generator will not turn over - just clicks.

Even when I push the battery button on the dash it still will not turn over. I can start the engine.

Is the Generator powered by the "house bank of batteries"? Why won't the push button work? The lights inside the coach work. And the battery disconnect is not disconnected.

FYI - I have 2 engine batteries and 4 house batteries.

Is it possible the house batteries are dead dead and won't charge? What should I check?

Jim

[shields]

Hi,

Some of the more mechanical sorts will probably have a better understanding than I do, but here's my two cents worth.

1. The MH was at the shop for a month; so there was lots of time for the batteries to be drained from various sources.

2. When you picked it up from the shop, the engine had to be jumped; so the engine batteries were depleted.

3. When you picked it up from the shop, the generator would not crank; so the house batteries were depleted also.

4. After driving home, and plugging in for awhile, the engine starts on its own; so the engine batteries are getting charged (from the alternator, shore power, or both).

5. The genset is still not cranking on its own, but the lights in the coach work; so the house batteries have taken some amount of charge (or are still holding some voltage). They just don't have enough power to turn the starter.

Maybe the house batteries just need more time to charge. I'd leave the coach plugged in for another day or so and see if they charge up. Or, if you're good with a multimeter, you can check the voltage and see if they are charging. If you're so inclined, write back and we'll help you through the process.

Another (less joyous) prospect, is that the batteries are damaged, or the charging system is not working properly. By the way, was the MH in the shop for anything electrical?

Good luck,

Tim

[jmgrigsby]

It was not in shop for any electrical problem. It has an air lock as a result of my changing the fuel filter - so they had to use the engine batteries a lot.

I have that Echo Charger on my inverter, so I think my house batteries are being charged. They may have been weak to start with. But I thought the dash switch would tie the engine and house batteries together and - that would start the gen.

I'll give them more time to charge and try again.

jim

[wolfe10]

Jim,

One reason there have not been more posts (other than Tim's excellent post) is that there are so many different ways that your electrical system can be wired.

Some but not many coaches have a separate generator start battery. Definitely look at your wiring diagram or contact your coach manufacturer for details on exactly how your batteries and their charging are configured.

Many electrical systems are configured as follows(again, will NOT apply to all cases):

Two battery banks, CHASSIS and HOUSE.

House normally is wired as generator start battery, but there are certainly some that use the chassis battery.

Engine alternator charges both battery banks, generally through a battery isolator which can be diode-based or solenoid/relay-based.

Inverter/charger or converter always charge the house bank. Some also charge the chassis bank. If you have an Echo charger, it is likely that it is used to charge the chassis battery bank when the inverter/charger or converter charges the house battery bank AND voltage exceeds the pre-set minimum on the house bank.

A digital voltmeter (start under $20 at Radio Shack, Sears, etc) will allow you to check for voltage at each battery bank and at the large positive lug on the generator.

Here is what you should find:

Shore power off and generator off: Both battery banks should read different voltage and with no load on them range from 12.2 VDC (50% discharged battery) to 12.8 (fully charged battery).

Starting the engine and bringing engine RPM to fast idle should show both banks in the 13.5 to 14.2 VDC range.

Engine off, shore power on, inverter/charger or converter working: House battery bank should be 13.5 to 14.5 VDC. With an echo charger, voltage on the chassis bank should be similar.

Brett

[jmgrigsby]

Brett,

My generator starts from the house batteries.

Thinking back - when I tried to start gen, the batteries apparently were not full charged up. Because the gen starter turned over very slow then click,click, click. I read in the Onan book that there is a "Low Cranking Fuse on starter solenoid" - But it is ok. Seems it could be 2 things - batteries still too weak even though they operate house lights good or the slow cranking damaged the starter.

I checked my batteries and the voltage is 13.45 with shore power on.

I guess I need to check them without shore power.

What can I do next?

jim

[Guest BillAdams]

Brett,

My generator starts from the house batteries.

Thinking back - when I tried to start gen, the batteries apparently were not full charged up. Because the gen starter turned over very slow then click,click, click. I read in the Onan book that there is a "Low Cranking Fuse on starter solenoid" - But it is ok. Seems it could be 2 things - batteries still too weak even though they operate house lights good or the slow cranking damaged the starter.

I checked my batteries and the voltage is 13.45 with shore power on.

I guess I need to check them without shore power.

What can I do next?

jim

Also check the voltage of the batteries when you try to crank the generator. If the voltage suddenly drops during cranking then they are shot and will need to be replaced.

[chucknewman]

To add to Bill's post, when you get your new voltmeter, also purchase a bag of (fairly) large clip leads. Clip directly to the generator's starter post and chassis ground. Be careful as this will be hot at battery potential. You should see 12 vdc to 14 vdc from the house batteries while the RV is plugged into shore power. Position the meter so you can watch it when you activate the local gen start switch. This is so you don't need a second person to be at the battery bank while the other starts the generator.

If the voltage drops below 9 vdc and the gen will not properly turn over, you are looking at undercharged/defective batteries, a wiring problem, defective starter, or defective circuit board/switch.

[jmgrigsby]

I had the House batteries checked - they were bad - and replaced.

The generator starts fine now.

jim

[Guest BillAdams]

That's what it sounded like. Sorry to hear about the additional cost but glad to hear you found the problem. Now, if the batteries were not "too" old you might want to ensure that the coach charging system is working properly causing a premature failure. If they were more than 7 years old or never properly maintained then the new ones should give you good service for many years to come.

[shields]

Hi Jim,

Thanks for letting us know how things worked out. I'd echo Bill's comment to check for proper charging as the new batteries start their service cycle. It only takes a few minutes and the voltages are listed in the posts above.

Good luck and happy travels.

Tim

[jameseh]

You are missing the Point. To check house batteries take a DC VOLTMETER and probe positive post and minus post of each battery and check the voltage. Then, while cranking the generator check the voltage at each battery-- should be 5 to the 6 range. This assumes the batteries are 6 VDC batteries wired in series and you are checking each individual battery.

Then go with the voltmeter probes one to the plus side of one battery and to the minus on the second battery (you are now checking across the two in-series 6 VDC batteries so nominal voltage is 12 VDC) and crank the generator and the check the voltage-- it should not go below 9 volts.

Also check all cables connections.

If one battery is bad you need to change out both batteries as a PAIR. The old battery will pull down the new battery and you will still have a problem because the internal resistance are different. Do the same on the main motor battery-- should not go below 9volts when cracking. With this method there is no guessing.