Generator won't start unless RV engine has been started

[bluebarry1964b]

Hi guys;

Getting ready for another trip; this one about 4600 miles in total. Noticed that the last couple of times I was at the RV (2003 Holiday Rambler Neptune) the Onan diesel generator wouldn't start unless I started the RV first. I'm thinking maybe the batteries are shot as they are 3 years old. Two things confusing me, though, are:

1) According to the readings I'm getting on my Energy Management Center, both the House and Chassis batteries are fully charged.

2)The RV itself seems to start just fine. I have 4 house and 2 chassis batteries. I would think that the generator and RV both use the chassis batteries to start, so it's weird that the RV starts with no problem, yet the generator doesn't even turn over unless I start the RV first.

Anyone else out there experienced this?

[bluebarry1964b]

Thanks for all the ideas; I really appreciate it.

[wa8yxm]

At 3 years, if they were properly maintained the batteries are the equivlent of a human teenager, Not even "in the prime" yet (that would be 4 years) Batteries properly maintained are like a popular convience store 7-11 (years though) (The store, originaly, was open 7am to 11pm in case you wonder where the name comes from, I'm old enough to remember those days).

However if the batteries are LOW.. or if they have not been maintained, or if the terminals are a bit dirty. (All very common) then you must supplement. Two ways to do that.

one, you figured out

Two, Press and hold the EMERGENCY STAT (may be labeled aux start or BOOST) switch, while starting Generator (what I do) this is the same button you use to "Jump Start" the main engine from the house batteries.

But have your house batteries tested.. Clean and test.. Easier to test 'em than replace 'em.

[Sam_Spade]

bluebarry1964b wrote:
My understanding is that ALL batteries, regardless of whether they are house or chassis, have to be replaced if even one house battery is shot? Am I correct?

NO.

BUT.....if the chassis battery is also 4 years or more old AND it hasn't had any special attention while in storage, it might be a good idea to replace it anyway.

DO check the main connections to the house batteries though.

And get them tested. If you can find an Auto Zone or WalMart with a big enough parking lot you can even get them tested right in the unit. To get a good test, they should be fully charged first.

[rdmike]

No. Chassis and house two seperate purposes. Just changed my house, 4 batteries, purchased Interstate at Costco for 83 bucks each.

[DSDP_Don]

They are a completely separate system. Before you go too crazy, it could be as simple as a dirty ground (connections). If you have dirty connections, it will take more power to start the generator.

[bluebarry1964b]

This is the OP: I know that you have to change-out all of the house batteries even if only one or two are shot. I do understand that all of them will need to be replaced simultaneously. But what about the chassis batteries? If I find that the house batteries are shot, are the chassis batteries considered to be part of the same system in the sense that they, too, would have to be replaced at the same time if I'm replacing the house batteries? Or are they considered to be a completely separate system. My understanding is that ALL batteries, regardless of whether they are house or chassis, have to be replaced if even one house battery is shot? Am I correct?

[Matt_Colie]

I did a lot of boat work before the depression shut me down. I have seen this multiple times.
Put a meter on the house bank and crank the APU/genset.
Does the meter drop below 10?? The bank is shot.
The meter barely moves? There is a bad connection between the house bank and the APU after the isolator cross feed.

Matt

[Sam_Spade]

bluebarry1964b wrote:
yet the generator doesn't even turn over unless I start the RV first.

Anyone else out there experienced this?

Many have. How long did it sit since the last use ?

Starting the gen is the most severe job that the house batteries have. As they get weak, it is likely to show up there first.

Starting the engine operates a solenoid and ties the two batteries together.....to charge the house batteries while driving. If you have an "emergency start" switch, it should accomplish the same thing but it's really designed to recover from a dead truck battery.

It's fairly common for a worn out battery to charge up fully but not be able to give back that charge when asked to. You might be able to nurse some more time out of them by connecting a battery tender when not in use.....but that is not a real fix.

[Mandalay_Parr]

2oldman wrote:
It seems likely your generator starts via the house batteries. A simple voltmeter check will tell you this. It's also likely the house batteries are shot. Again, voltmeter.

Same here.

[2oldman]

It seems likely your generator starts via the house batteries. A simple voltmeter check will tell you this. It's also likely the house batteries are shot. Again, voltmeter.