Alternator not charging the House after battery upgrade. HELP!!!

[Grouchyoldman]

The 4-year old batteries in our 2016 Coachman Freelander 21QB motorhome were getting tired and I decided on a replacement before we begin our winter travels.

The old bank consisted of two 12 VDC 80 AH "deep cycle" AGM batteries wired in parallel with a Victron 712 battery monitor to keep an eye on them. They still worked ok but the usable output was headed down hill and we'd gotten almost five years out of them so... replacement time.

After research and some very helpful advice on this forum I decided to upgrade to two Trojan T-105 GC-2 golf cart batteries wired in series for a useful capacity of about 225 AH @ 12VDC. The install was tight due to their height nudging the insulation foam on the doorstep battery box. Otherwise all went well and after an initial charge using the WFCO charger on shore power I ran a draw down test and found everything spot on.

The problem is that after the upgrade I noticed something strange: when I unplugged from shore power and fired up the engine on our Chevy 4500 it didn't seem to provide charging power to the house batteries from the alternator. Didn't matter whether the battery disconnect switch was on or off.

I've racked my brain as to what's going on, and soon realized that I have no real idea of how my Battery Control Center does its job or how it might even detect the difference between two 12VDC batteries in parallel, or two 6VDC batteries in series? Or maybe something in the Battery Control unit needs to be reset? Or something with the WFCO WF-8900 converter/distribution center?

I have a little voltmeter plugged into the dashboard that shows the engine battery voltage and I can see it jump to 14+ volts when I start the engine, but there's no current flowing to the house!

I've always counted on the house batteries charging while we are driving, so I think this is a new problem but I've never ran any tests, just took it for granted. The engine battery isn't fully charged at the moment (12.4 VDC) and the new house batteries are fully charged (13.6VDC). Is it possible that no alternator current flows to the house UNTIL the engine battery is topped off?

Can you experts enlighten me, or at least provide some hints on where I should look for an answer?

Thanks in advance,
-Grouchy

[TitanMike]

Originally Posted by Grouchyoldman

The 4-year old batteries in our 2016 Coachman Freelander 21QB motorhome were getting tired and I decided on a replacement before we begin our winter travels.

The old bank consisted of two 12 VDC 80 AH "deep cycle" AGM batteries wired in parallel with a Victron 712 battery monitor to keep an eye on them. They still worked ok but the usable output was headed down hill and we'd gotten almost five years out of them so... replacement time.

After research and some very helpful advice on this forum I decided to upgrade to two Trojan T-105 GC-2 golf cart batteries wired in series for a useful capacity of about 225 AH @ 12VDC. The install was tight due to their height nudging the insulation foam on the doorstep battery box. Otherwise all went well and after an initial charge using the WFCO charger on shore power I ran a draw down test and found everything spot on.

The problem is that after the upgrade I noticed something strange: when I unplugged from shore power and fired up the engine on our Chevy 4500 it didn't seem to provide charging power to the house batteries from the alternator. Didn't matter whether the battery disconnect switch was on or off.

I've racked my brain as to what's going on, and soon realized that I have no real idea of how my Battery Control Center does its job or how it might even detect the difference between two 12VDC batteries in parallel, or two 6VDC batteries in series? Or maybe something in the Battery Control unit needs to be reset? Or something with the WFCO WF-8900 converter/distribution center?

I have a little voltmeter plugged into the dashboard that shows the engine battery voltage and I can see it jump to 14+ volts when I start the engine, but there's no current flowing to the house!

I've always counted on the house batteries charging while we are driving, so I think this is a new problem but I've never ran any tests, just took it for granted. The engine battery isn't fully charged at the moment (12.4 VDC) and the new house batteries are fully charged (13.6VDC). Is it possible that no alternator current flows to the house UNTIL the engine battery is topped off?

Can you experts enlighten me, or at least provide some hints on where I should look for an answer?

Thanks in advance,
-Grouchy

When you change from 12V batteries in parallel to 6 volt batteries in series your charging system doesn't know the difference. It only "sees" the two 6V batteries in series as one larger 12 volt battery.

I would start with the charging wire from the vehicle's charging system and look for fuses that may have blown or wires that may have been overlooked during the changeover.

A good Multi-Meter is going to be your best friend.

With engine running start at the chassis battery (starting battery) and measure voltage. Follow back to the Battery Control device and on to the house batteries. At some point in this "journey" you will see where the higher charging voltage stops and the lower house battery voltage begins. This is where you will want to focus.

Since you were able to charge batteries with the Converter it is working correctly and should have no effect on charging from the alternator.

In my experience the most common issue when changing out batteries is overlooking a wire that used to be connected and during the process has "wandered off and overlooked when reconnecting".

[Grouchyoldman]

Thanks TitanMike,

That's a good start. The only "extra" wiring I noticed was the lead from the Victron shunt block to the pos terminal on the batteries, but I'll check again. I'll also try tracing the alternator voltage back.

Am I right tho that all the circuitry that controls this stuff resides in the RV Battery Control Center that is right next to the battery well? For example the circuit that prevents the House from pulling down the starter battery?

The FR Owner's Guide has next to zero info on this area. Are there schematics anywhere, or at least a block diagram so I can understand the buss bars, shunts and diodes in there?

[Toy4Rick]

I'm no expert here by any means...

I had a similar concern so I reached out to Precision Circuits, turns out your statement about the chassis battery is not fully charged is, IMHO telling...

When I reached out, they indicated the BIM won't begin charging the house battery until 1. the Chassis battery is fully charged AND 2. the coach battery has dropped below 12.6v

When using the Victron app, I can see when the charging goes from the chassis to the coach and back again

Good luck

[Grouchyoldman]

Hi Toy4Rick,

I ran a test today on your suggestion:

- I charged the chassis battery up to full power using a charger.
- I pulled the new house battery bank down to 12.4 VDC using the inverter to power a household 120v fan for a few hours.

I used a volt meter at the solenoid in the RV battery control center, then I started the engine and.... nothing.

The solenoid in the RV battery control center clicked (indicating that alternator current should be available, but the voltage to the house batteries stayed the same and the Victron still showed a net loss of amperage as before I started the engine.

So I started looking upstream in the Chevy 4500. Clearly the alternator is working because 14.4 volts were going to the chassis battery.

The chevy fuse diagrams mention two "Auxiliary'' circuits, each with its own fuse and a relay. I only had time to check one of them, a 50A fuse & relay. The relay clicked when I turned on the key and the fuse was good. No problem there, no Eureka moment either.

That leaves me with only one candidate, the other Aux circuit in the Chevy fusebox. I'll check that in the morning but if that isn't it I'm not sure where to look next.

Thanks everyone for your ideas on this.

-Grouchy

[Grouchyoldman]

I think I found the problem, but it was nowhere near where I thought!

I fired up the chevy 4500 engine to produce 14.4 VDC from the alternator and started tracing that voltage back towards the RV house. The very first component downstream of the chassis battery is the item pictured below (the rubber cover says "Bussman").

With the engine started, on the left hand terminal, direct from the battery I read 14.4 VDC from the alternator. On the other side 12.63, the voltage on the house battery bank.

When I shut the engine off and test continuity between the two terminals it is an open circuit. Like a blown fuse. There are no part numbers on the Bussman device so how do I go about identifying and replacing it?



============

Dang it, doesn't look like the images displayed, try these links.

http://www.themeyergroup.org/bussman1.jpg
http://www.themeyergroup.org/bussman2.jpg

[Bama Rambler]

That's an AMG fuse (see below) in a holder. I can't see the amp rating, but all you need to do is find the rating and get a replacement. A local auto parts store may have them in stock.

[TitanMike]

,,,,,

[Grouchyoldman]

Good call Bama Rambler! I just removed the fuse and it's 250 Amp already ordered one and a spare.

I guess it blew when I first connected the new batteries.

You guys RAWK, thanks so much for nudging me along with this puzzler!