Battery problem

[ECones]

Our battery in the RV went down this weekend and wouldn't stay up while running down the road.

I checked it once back home, and with the switch in "Store", the battery puts out about 8.5 volts whether plugged into 30 amp or not. In "Use" with the truck engine running it checks about 12.5 volts across the terminals, and with it plugged into 30 amp, and the battery switch in "Use" it reads 13 volts across the terminals. It seems to be charging.

Since it went down while driving down the road with the switch in "Use", I'm thinking the battery is done for, but I'd sure like other opinions.

Second part of the question:
If it does need a battery, this RV is only 6 months old. Should the dealer replace it under warranty?

[tenbear]

Coach-man wrote:

tenbear wrote:
My OEM disconnect switch disconnects practically everything. I have had my MH stored for 3 weeks, not connected to power, and the battery voltage hardly changed at all. The engine started right up.

You say "engine started right up"? The house battery has nothing to do with starting, and neither does your disconect switch. The disconnect switch is wired to your house battery, but leaves thins like your steps, LP detector, and sometimes the radio, stereo, which draw power and in some cases run down the battery.

I know the engine and coach batteries are two separate systems that in my case are only connected when the ignition switch is on. I only mentioned the coach battery to indicate that neither battery was discharged during the 3 weeks that I was not connected to power.

[ECones]

burlmart wrote:
edited for clarity

ECones wrote:

FWIW, we left this morning with the battery fully charged, and the battery was at 13 volts. We drove with the switch in "Use" for about four hours, and when we stopped it was at 12.45. I don't know if that's significant or not.

this is very significant.

i still am assuming your rig has BIRD, and it should have kept the house batt charged. 12.45V is a BIG drop

it looks like your engine's 14V(presumed) is not charging the house batt as it should if your BIRD is working. both batts should charge when either is getting over 13.2

i am suspecting a prob in BIRD hookup, or else it's solenoid (Relay)

locate this solenoid and there should be 12V on the two small terminals (if plugged to shore and in USE, or if engine is on and in USE). the 2 large terminals go off to the pos pole of the house and the engine batts . touch either and chassis frame and get that batt's voltage (solenoid is likely close to frame. guess you could trace red cables from either batt)

I felt it was significant as well. Thanks.

I'm much more comfortable working on things with two wheels, but I'll try what you suggest sometime next week. I don' know if it has a BIRD or not. I'll try to figure that out. And ... I'll try to find it 😉

I just want to identify the problem while the rig's under warranty, so maybe I can get it fixed.

[burlmart]

adding to my previous post on engine not charging house...

12.45V is about 3/4 capacity. assuming your house batt has a capacity of maybe 110 amp-hours, in 4 hours your batt went from 110 to 0.75x110, or 7 amps per hour.

[Gene_in_NE]

Coach-man wrote:
You say "engine started right up"? The house battery has nothing to do with starting, and neither does your disconect switch. The disconnect switch is wired to your house battery, but leaves thins like your steps, LP detector, and sometimes the radio, stereo, which draw power and in some cases run down the battery.

To the OP your measure of 12.45 volts on the battery is almost dead. The engine alternator should have been charging as you drove. You either have a big drain on the battery or the battery is bad!

You are correct in 99% of your response. If the engine is running, the alternator would show a higher voltage at the house battery. However, after a short time of the engine no longer running, the voltage will drop to the steady state. According to this
Battery voltage (Temperature compensated) the battery would be 75% if the temperature is 80 degrees.

[Coach-man]

tenbear wrote:

Coach-man wrote:
I hope you are aware that the so called disconect switch disconects pratically nothing! Purchase a marine type disconect switch and install it next to the battery, one that disconects everything for storage, that should help.

My OEM disconnect switch disconnects practically everything. I have had my MH stored for 3 weeks, not connected to power, and the battery voltage hardly changed at all. The engine started right up.

Your disconnect switch is obviously not wired the same as mine.

You say "engine started right up"? The house battery has nothing to do with starting, and neither does your disconect switch. The disconnect switch is wired to your house battery, but leaves thins like your steps, LP detector, and sometimes the radio, stereo, which draw power and in some cases run down the battery.

To the OP your measure of 12.45 volts on the battery is almost dead. The engine alternator should have been charging as you drove. You either have a big drain on the battery or the battery is bad!

[burlmart]

edited for clarity

ECones wrote:

FWIW, we left this morning with the battery fully charged, and the battery was at 13 volts. We drove with the switch in "Use" for about four hours, and when we stopped it was at 12.45. I don't know if that's significant or not.

this is very significant.

i still am assuming your rig has BIRD, and it should have kept the house batt charged. 12.45V is a BIG drop

it looks like your engine's 14V(presumed) is not charging the house batt as it should if your BIRD is working. both batts should charge when either is getting over 13.2

i am suspecting a prob in BIRD hookup, or else it's solenoid (Relay)

locate this solenoid and there should be 12V on the two small terminals (if plugged to shore and in USE, or if engine is on and in USE). the 2 large terminals go off to the pos pole of the house and the engine batts . touch either and chassis frame and get that batt's voltage (solenoid is likely close to frame. guess you could trace red cables from either batt)

[ECones]

A local RV dealer recommended we use "Store" when the RV is plugged into shore power. But my book says that it goes to a maintenance mode and won't overcharge, so it seems it should be on virtually all the time as well.

Ours is plugged to short power virtually all time time anyway.

FWIW, we left this morning with the battery fully charged, and the battery was at 13 volts. We drove with the switch in "Use" for about four hours, and when we stopped it was at 12.45. I don't know if that's significant or not.

After reading through this, I think we should leave the switch in "Use" unless we really are storing it off power. We do plug in when it's parked at our home.

[PaulJ2]

I think some may be in the weeds here. The STORE switch is to be used while the unit is in long term storage or non use for a time. Leave it in the USE position at all other times. In the STORE position battery is not getting charged from the engine or when plugged into ac. You may be replacing a good battery for nothing.

[tenbear]

Coach-man wrote:
I hope you are aware that the so called disconect switch disconects pratically nothing! Purchase a marine type disconect switch and install it next to the battery, one that disconects everything for storage, that should help.

My OEM disconnect switch disconnects practically everything. I have had my MH stored for 3 weeks, not connected to power, and the battery voltage hardly changed at all. The engine started right up.

Your disconnect switch is obviously not wired the same as mine.

[Coach-man]

Some of those phantom loads can be hard to detect unless you use an amp meter. The cumulative draw can be quite high. I have installed positive cut off switches in several RV's and has definitely helped my situation.

[DrewE]

Coach-man wrote:
I hope you are aware that the so called disconect switch disconects pratically nothing! Purchase a marine type disconect switch and install it next to the battery, one that disconects everything for storage, that should help.

That varies from RV to RV.

On my class C, the disconnect switch disconnects everything except the converter, the generator starter power, the steps retraction, and the remote control for the disconnect solenoid, so far as I can suss things out. In particular, the LP and CO detectors, the radio presets backup, and other phantom loads are indeed switched out.

[Coach-man]

I hope you are aware that the so called disconect switch disconects pratically nothing! Purchase a marine type disconect switch and install it next to the battery, one that disconects everything for storage, that should help.

[tenbear]

It seems you use your Use/Store (battery disconnect) switch much more than I do. I usually leave mine in Use (connected) unless I will be disconnected from power for days. When the RV is sitting at the house between trips it is plugged in and the battery is connected (Use).

If you do not have a 3 or 4 stage converter you will have to check the battery often to make sure the water doesn't boil away. Start off checking it every 2 weeks and change the interval when you learn how quickly the water evaporates.

[ECones]

tenbear wrote:
I presume your Use/Store switch is the same as my battery disconnect switch and when set to store it disconnects the battery.

If you have been plugged in and the switch is set to Store, the coach battery would not be getting charged. At least that is how mine works. I believe the Store position is to prevent the battery from being being discharged by parasitic loads while sitting in storage and not plugged in. However not all battery disconnect switches actually disconnect all loads, so there may still be a small drain on the battery in Store.

If you can get your hands on a clamp-on DC ammeter you can measure the current into and out of the battery and see exactly what is going on.

It sounds like a clamp-on DC ammeter may be my next purchase 😉

Thanks