New batteries die quickly!

I just bought a 1998 Salem 30 foot toy box 5th wheel.  It came with a GIGANTIC Catapiler 12 volt battery which wasn't holding a  charge.  I replaced it with 2 large deep cycle batteries wired plus to plus, minus to minus.  They seem to not hold a charge either.  They're dying down to 2 volts each, wether they're wired individually or together.  I also notice that I'm blowing the main fuse on my new Honda 4500 watt generator with even just having the Air conditioning on.  I've been told that that gen should be more than enough to power the unit. 

Any idea what may be killing my battery and not allowing the charge to take place?  When the gen is running or it's plugged into 30 amp service, the charger seems to be reading around 10.6 volts (where the battery is only reading 2.something volts)  I pulled the battery out and jumper cabled it to my ford F350's battery and it took a charge back to 12.6 volts in about 30 minutes.  back into the RV and it dies again.

I've removed every fuse from the 12 volt system, so I don't think it's a short on anything that is powered off the 12 volt system, but if I connnect a freshly charged battery to the RV even with EVERYTHING off (lights, pumps, heat, etc) it still kills the battery within a few hours.

Anyone got any diagnostic hints or ideas of what I should look at?

-Greg

Did you buy your fifth wheel from a dealer where there would be some warranty service or from an individual?  If the latter, did you receive any service history where you might be able to see if there were previous problems?

If information or service is unavailable, can you get a wiring diagram from the manufacturer..where you may also be able to get some insights?

Obviously there is something drawing quite a bit of current, so it needs to be isolated.  When you say all 12VDC fuses were removed, does that mean the batteries continue to discharge while all fuses are removed?

I have seen a wiring situation in an RV where there was a hidden fuse which protected the fuse panel..believe it or not, and the only way to have learned about it was from the manufacturer!

Have you checked the charger/converter to determine if there may be a regulation circuit that has failed and the batteries are discharging into the converter?

You have a short somewhere.  Considering the speed with which this takes down the battery here is a diagnostic procedure, NOTE, use this with caution fire is possible

If you have a battery disconnect,,,, Disconnect it and charge the battery with an aux charger (Like a standard automotive battery charger) you should not leave the battery discharged... NOTE: If you don't have a battery disconnect,,, GET one

If you don't have a BCC skip to "Don't have a BCC"

Next if you have a "Battery Control Center" (remote operated disconnect) like I do on my Damon, still use a battery disconnect (hard switch) at the battery.  they don't cost much and are easier than pulling and reconnecting every test, safer too.    Turn the BCC off

now, again, if you have a BCC use a test light across the OPEN disconnect.. It should not light or very very very dim if it does (The bcc may draw some limted power)  On my motor home it will light well but that is because there are loads ahead of the BCC (After-market)

If the light comes on strong fire up the shore power and measure voltages.. Full 13-14 volts,, GOOD, the problem is beween the Battery and the BCC

If the light does not come on, continue with the following

Don't have a bcc,?
If you don't have a BCC, then measure voltage in the system with shore power on and battery disconnected... 13-14 you got problems I can't help you with... Less than 13 continue

With everythign turned off check for current flow.. You can bring a compass near a power line and it will deflect if the wire is passing current (Wire not passing current won't affect it) or you can CAREFULLY touch.. I suspect there is enough current flowing that these wires will be HOT.  No current flowing

Now.. If you can't find any current flowing you have a bad converter/inverter/charger (Whatever you have) which, by the way, is a SERIOUS posiblity  To test this, fully charge battery,  DISCONNECT 12 volt lead at the converter/inverter and reconnect the battery ...Monitor battery voltage for an hour... IT should not change

In this case... I kind of suspect the converter... The only wire in the unit capable of taking a good high quality battery down that fast without setting fire to the rig is the converter wire  It is also not fused.. Thus I suspect the converter

Temporary solution is to leave it disconnected (tape off wire) and use an external charger,  This is till you can get a replacement

Replacements are not all that expensive, easily installed and generally better than original equipment save for current models