Alternator not charging house batteries on MBS

[bob5560g]

I just replaced the batteries on my Forester MBS, and installed a Victron 700 battery monitoring system (BMS). It works, with a 6 amp load from lights and fans, I see current flowing out of the batteries and their voltage slowly dropping.

When I plug into 120VAC or start the generator, I see current flowing back into the batteries and their voltage slowly rising. All is well, except.....

Now the alternator is not charging the house batteries. (Yes, the battery disconnect is in the normal "ON" position.) When you start the engine, even if you rev to 2,000 RPM,the BMS does not change at all, nor does the voltage measured with a multimeter.

When manually measured with multimeter, engine battery was at 12.65V with key off, house batteries were at 12.88V, BMS showing the 6 amp load. (BMS calls that 85% charged). Start the engine, it's battery jumps to 14.1V as it should, but absolutely no change on the house battery, whether measured with meter or BMS. Voltage stays the same and outflow of current does not change (whereas it should reverse.

So I must have not reconnected the wire the wire that comes from the alternator wherever that is! The ONLY wires I disconnected were 6 AWG battery cables. But with two 12V in parallel, two circuit breakers, etc. there were a bunch of positive connections at the battery posts. I took pictures before disconnecting and put everything back like it was but logic would say that something changed.

The multiple red battery cables are not easy to trace, as they go into plastic wire looms, pass through the floor, are buried under the stuff they spray under RVsS, etc. Anyone have any ideas, especially about where the alternator connects to the house electrical system?

[KatanaPilot]

I do not know the exact voltages involved, but it is possible your Battery Control Center is working normally. My understanding is that the relay will close to charge coach from alternator or chassis from converter only when needed.

My suggestion would be to put a big load on the coach DC circuit (maybe the furnace fan, Fantastic Fans, water pump) to see if the relay closes and the alternator charges the coach batteries.

To make sure the converter will charge the chassis battery through the BCC - plug in shore power or run the generator and turn on a big chassis load - like the headlights. Again, the relay in the BCC should close and you should read the same voltage with your Victron on both the chassis and coach batteries. Of course, you would need the engine shut off in this case.

At least this is how the BCC works on our 2015 Forester MBS.

[bob5560g]

Thanks for the ideas KatanaPilot. My MBS is also a 2015.

With the house batteries at 80% (which should draw a charge from any source), and a 13 amp load applied, they are drawing a 40 amp charge from the AC sourced power converter. But they get nothing from the alternator when I start the engine.

For the BCC, the solenoid does NOT "clunk" (close the circuit) in the above scenario, whether you connect the AC (even though it's charging the batteries trhrough the converter), nor when you start the engine.

However, in the second test you recommended, headlights on to draw a load, it clunks as soon as you plug into AC, thereby feeding a charge from the power converter to the engine battery. So it is working in that direction. I'm not sure if the BCC is supposed to be involved in charging the house batteries from the alternator.

One thing I did not mention is that when I removed the factory batteries to replace them with bigger ones, a red cable fell off when I touched it. (They had put a smaller AWG 6 cable into a larger AWG 4 crimp connector so it was a poor crimp.) This cable came from the circuit breaker behind the left battery in the battery well under the entry stairs. I repaired it with the proper connector but this just added to the confusing tangle of red cables going to/from the batteries and their breakers in the battery well. So it's conceivable that I did not hook something up 100% correctly but I doubt it.

But back to the BCC, shouldn't the solenoid close to allow DC to flow from the alternator to the house batteries?

[Sagecoachdriver]

Do you have the Precision Circuits Bttery Isolation Manage in your step well(see photo below)? If so, read this explanation of how the bi-directional system works. http://www.precisioncircuitsinc.com/...nager-RevF.pdf
and
http://www.precisioncircuitsinc.com/...e-Shooting.pdf
Does strange things like have the alternator only charge house batteries for 1 hour while driving. Alternator may only be charging engine battery because it is low. When charged up, it should charge house batteries, but only for 1 hour.

[KatanaPilot]

Originally Posted by bob5560g

Thanks for the ideas KatanaPilot. My MBS is also a 2015.

With the house batteries at 80% (which should draw a charge from any source), and a 13 amp load applied, they are drawing a 40 amp charge from the AC sourced power converter. But they get nothing from the alternator when I start the engine.

For the BCC, the solenoid does NOT "clunk" (close the circuit) in the above scenario, whether you connect the AC (even though it's charging the batteries trhrough the converter), nor when you start the engine.

However, in the second test you recommended, headlights on to draw a load, it clunks as soon as you plug into AC, thereby feeding a charge from the power converter to the engine battery. So it is working in that direction. I'm not sure if the BCC is supposed to be involved in charging the house batteries from the alternator.

One thing I did not mention is that when I removed the factory batteries to replace them with bigger ones, a red cable fell off when I touched it. (They had put a smaller AWG 6 cable into a larger AWG 4 crimp connector so it was a poor crimp.) This cable came from the circuit breaker behind the left battery in the battery well under the entry stairs. I repaired it with the proper connector but this just added to the confusing tangle of red cables going to/from the batteries and their breakers in the battery well. So it's conceivable that I did not hook something up 100% correctly but I doubt it.

But back to the BCC, shouldn't the solenoid close to allow DC to flow from the alternator to the house batteries?

Crimping battery cables must be the entry level job at FR with the $5 Harbor Freight hammer-style crimper. The exact same thing happened to mine. You would think a billion dollar corporation owned by Warren Buffett would be able to afford a hydraulic die style crimper. You can buy a Chinese-made one for less than $100. Even they will make a better crimp.

And yes, the BCC should close the relay and allow the alternator from the coach to charge the house batteries. The Battery Isolation Manager in the BCC performs all of these functions, if I understand the functionality correctly. The diagram linked in the previous post should help you determine if everything is hooked up correctly.

[2020pete]

Check 50amp circuit breaker under drivers seat

[Comanchecreek]

You need to see the specs on your battery isolator. Many have circuitry that make the starter battery and the coach battery secondary. If you are checking voltages right after start up the isolator will not be sending power to the coach battery. It will then send it, (hopefully) after the starter battery is fully charged. If there is any issue with your starting battery it will never switch over. I've always preferred the solenoid type isolator where it connects whenever the key is on. Not as problematic, but you need to see what you have. May be as simple as a blown fuse.

[Eric99]

I thought I had a problem with the alternator charging my house batteries also. I did a bunch of troubleshooting but I found out I just need to wait longer for the BCC to connect in the alternator. On my 2014 Solera it does not connect in right away. I also have had a battery cable pull right out of the crimp. Seems like a lot of people have this problem.

[brucemc]

i have a similar issue on our 2016 Sunseeker - however I have 12v from the chassis to the BCC; the relay closes when pressing the emergency start & the voltages match when the relay is closed.

Here's my post in the Sunseeker forum:
http://www.forestriverforums.com/for...is-138447.html

I'll also add a note to this thread in that thread... (circular references? Fun)