Main battery not holding charge

[RonVBT]

I'll agree with mike Bartelt, my Morningstar Solar controller is the best battery charger/maintainer of the bunch. It's only when my coach is parked inside that I have any battery problems.

[adamchimes]

Thanks to all for the assistance. I feel really silly, but it looks like the cause of the issue was that I had pressed the chassis battery disconnect switch. In our RV it's hard to tell when the battery is connected or disconnected since there is no indicator light and the switch is more like a button (i.e. it doesn't flick up or down, but you do need to press it up or down to either connect or disconnect).

Luckily, a neighbour at our last campsite suggested checking this. I had thought that if the battery had been disconnected it simply wouldn't charge, but he advised that it could be jumped off the Aux battery and then hold a little charge but would continually drain while the disconnect was active.

Anyway, just thought i'd post my solution here in case anyone else is working through the same issue.

[jergeod]

Always look for the dumb things first. You will save a lot of your money that way.

[jergeod]

Sorry

[RonVBT]

I'm glad it was something easy. It turned out to be quite an exercise in troubleshooting for the group though. It still doesn't explain why the chassis battery would charge off the generator and not shore power unless you were connecting and disconnecting the chassis battery without really knowing it. I know my chassis battery won't charge when it is placed in the disconnect status (mine is a momentary switch also but there is a light next to it that indicates it's status).

That is the subject of the recall I posted earlier. On my coach, the solenoid that the disconnect switch controls in the BCC (Battery Control Center) went bad and caused my chassis battery to discharge while I was driving it in heavy city traffic! The result was the instrument panel went dead followed quickly by the engine quitting. I had no power steering or brake assist. Luckily, when the instrument panel started acting up, I moved to the far right lane and was able to coast off the highway onto a safe spot. I had just bought the motorhome and was only about 5 miles from the dealership. I called them and they came right out. A Highway Patrol (CHP) also stopped to see what was going on. He suggested that I get the motorhome fixed before proceeding.

One of the mechanics remembered the recall and did the service by memory. Once I got home, I made it a priority to learn all about my DC and AC power systems in the coach.

A motorhome is way more complex than just a house on wheels.

[adamchimes]

Thanks RonVBT, the situation you described above is EXACTLY what happened to me on the road between Texas and Louisiana last month, so if our battery troubles persist after the current supposed 'fix' I will definitely check that solenoid in the BCC.

I also was under the impression that were the battery disconnected it wouldn't charge or function at all. Whenever we aren't connected via shore power, I'm running the generator 2-3 hours a day, so perhaps it was just getting enough charge each day to keep it alive (even though it was consistently draining). Anyway, appreciate your feedback :-)

[Mike Bartelt]

I'll still say consider getting a battery combiner or charge relay.

It will pass a charge from one bank to the other when it detects a charging current, but disconnects them when it is not receiving a charge or notices the banks are charged. It will also prevent it so you don't drain two banks. It will also prevent overcharging as well. Well worth the $100 or so and the hour it would take to install.

[RonVBT]

Here is a picture of the solenoids in my RV Custom Products BCC. They are located under the circuit board. I have removed the circuit board to get this picture....Not recommended or even necessary! I just like to take things apart.




The upper left solenoid (silver in color) is a fairly common one that you can find in RV Parts stores. It is the interconnect relay that connects both battery sets together under certain conditions such as both batteries over a certain voltage and disconnects them when the voltage goes below that voltage. It insures you don't drain both battery sets while camping. It is also the emergency switch to allow you to start your engine with the coach (Aux or house) battery if the engine battery goes dead. This solenoid requires power to it to hold it in the closed (connected) position.

The other two rectangular black solenoids are fancier ones that "latch" in whatever state they are in with no power required to hold them there. That is why they are controlled with a momentary switch. The top right one is the chassis solenoid that went bad on my BCC. The red wire going to it comes from the alternator. The metal bar attached to the top side goes back to the chassis (Main or engine) battery. You can see it here...



You see the black cable at the top of the BCC. I bought it at the local Auto parts store (it should be red but they didn't have red). It is connected to the top two terminals and effectively bypasses the chassis disconnect solenoid. This is to comply with the recall because if (and when) this solenoid fails, your engine will quit.

The rectangular black solenoid on the bottom is the Coach (House or Aux) disconnect solenoid.

It is worth (In my opinion) to track this system down in your coach and have an understanding of how it works. It is helpful to have a schematic of it as well.

You notice that all the batteries come to the BCC box. That means if you want to jump one battery to the other or install a charger/combiner as was suggested in an earlier post, monitor voltage or just about anything...here is a convenient place to do it.

Here is a picture with the BCC circuit board in place...

[RonVBT]

I Made a simplified schematic for myself that includes the Solar system I installed.



You will notice that there is a manual bypass switch which is a battery switch from the local auto parts store that I put in place of the black bypass cable pictured in the post above. This allows me to easily bypass the chassis battery disconnect solenoid when I am on the road to insure that I don't lose power again. I turn it off (open the switch) when in storage to allow the disconnect to work.

On the simplified schematic, in the lower left corner is the WFCO converter. It is located inside my coach (under the wardrobe) and has all the 110 circuit breakers on it as well as some more 12volt fuses. It is the 110vac to 12vdc converter for your coach. It takes 110vac and uses it to power your coach's 12 volt items (Lights, etc.) while on shore/gen power and also charges your batteries. It is fed by shore power or generator through the transfer switch (separate box) that decides which is appropriate. The transfer switch favors shore power.

Follow the wire from the WFCO converter on the schematic up to where it connects into the system and you see that the 12volts to charge your batteries has to go through the coach disconnect solenoid and the interconnect solenoid to charge the engine battery. The engine alternator, on the other hand, is labeled "Chassis Electronics" on the schematic (upper right side of schematic) and 12vdc from the alternator must go through the chassis disconnect to reach the engine battery, the coach (house) battery, or the rest of the motorhome systems.

If you have time on your hands, a motorhome can be a fun hobby!

[RonVBT]

I was reviewing the schematic/troubleshooting guide for the RV Customs BCC earlier today and noticed that the Interconnect relay that connects the Coach and chassis batteries together latches when one of the batteries is above 13.2 volts and unlatches (disconnects) when the system goes below 12.6 volts. It also says that the interconnect relay uses .5 amps to keep it closed. This means that any Motorhome that uses this BCC will discharge at a rate of at least .5amps until the two battery systems goes below 12.6 volts.

If you are chasing phantom power draws, this could be the culprit!

Turning both disconnects to the off position (disconnect) will cause the interconnect to unlatch....unless you have complied with the service recall that bypasses the Chassis disconnect relay as described earlier in this string. In this case, the interconnect will remain latched until the system goes below 12.6 volts.

This is a bad design and my intention is to modify mine to a simpler design. In the 70's, there were only two conditions that closed the interconnect relay
1) the ignition is on or;
2) the emergency start switch is depressed.

The 70's setup would not allow the house converter to charge the chassis battery.
A charge splitter may be the answer.

I'll have to think this through to come up with a better system.

[twinboat]

It will discharge 1/2 amp until either battery, not both, drops its voltage to 12.6 volts. That is the resting voltage of a standard 12 volt battery. Anything above that is a surface charge and will bleed off quickly.

Activating the isolation relay with only the key, will overload and overheat your alternator and discharge your start battery, if your house bank is large and low.
That is why the needed to move away from the dumb system.

The smart system will drop out the house bank, if it starts to drag down the chassis battery below 13.2 while driving.

This was needed as the house banks grew larger and larger, inverters were added and electronic engine and transmission controls were introduced that need a stable voltage.

My 1999 Class C has a key activated isolation relay, but it only has 1 house battery and it's about the same size as the chassis battery. The high output alternator the comes on MH chassis can handle that, but not a large 400 to 600 AH battery bank without some regulation from the voltage sensing controls.

[RonVBT]

[QUOTE=twinboat;3682313]It will discharge 1/2 amp until either battery, not both, drops its voltage to 12.6 volts.

Twinboat, I have to point out that when both batteries are connected together (via the interconnect relay) they will be at the same voltage within a tenth of a volt of each other, therefore, both batteries will be at 12.6 volts (plus or minus .1vdc) when the interconnect relay opens (disconnects).


[QUOTE=twinboat;3682313]Activating the isolation relay with only the key, will overload and overheat your alternator and discharge your start battery, if your house bank is large and low.

Twinboat, The BCC does the same thing as using the ignition switch to activate the interconnect relay except the BCC connects the battery sets together after a 15 second delay. The BCC manufacturer says the purpose of the 15 second delay is to allow the system voltage to stabilize prior to connecting the batteries together but the BCC (smart system) would still overload/overheat the alternator if that was a factor. I'm not sure if stabilizing the system voltage is just a selling point for the BCC or if there is something to it. The Ford F53 chassis uses a 175amp alternator which is pretty robust and it is coupled to a Ford (smart) regulator that regulates the voltage. The BCC doesn't regulate the charge voltage or charge amperage, it just connects the battery sets together when the voltage is high and disconnects them when the voltage is low. If your batteries are going to “tax” your charging system, the BCC won’t prevent it.

On the other hand, if your chassis battery goes dead and you activate the emergency start button (which closes the BCC interconnect relay), you then have the exact same situation as using the ignition switch to activate the interconnect relay – in that the batteries are connected together prior to starting the engine.

A BCC, in part, is a device to “fool-proof” your charging system. It does other things too like taking certain accessories off the ignition switch . . . i.e. Fog lamps, step motor, cabin lights, etc..

A human can make better choices for the charging system....if he or she remembers to do so. The problem is that my BCC has malfunctioned (story told earlier in this string) causing my coach engine to quit while driving down a busy highway. Also having the batteries connected together anytime there is something in the system above 12.6 volts is not always ideal either. I’m afraid that (at least in my case) a perfect system will require some manual input from the operator. In other words, a totally automatic system doesn’t cover all circumstances.