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Topic: How to link whole-house inverter to battery monitor (Read 6 times) previous topic - next topic
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How to link whole-house inverter to battery monitor
Yahoo Message Number: 136358
I upgraded to AGM batteries located under the rear-facing dinette bench of a 2004 RB and a battery monitor mounted on the side of the same bench facing the side entry for convenient reading.
 Later I had a whole-house inverter installed under the same bench as the above items.  From the sidewall of the coach to the center aisle, the order is:  inverter, batteries, monitor.
 Days later, hundreds of miles down the road, I discovered deep discharging of the batteries not reflected in the battery monitor read-out.  Further investigation revealed that when the inverter was installed, it was not connected in the circuit to the battery monitor.  So now, the battery monitor is accurate only to the extent that the inverter is not being used.
 How big a deal would it be connect the inverter to the battery monitor?  In the 2004 RB, the fuse panel and converter are located under the fridge across the center aisle from the dinette benches.  Can an amateur who is able to follow directions complete this task, or is it better left to a professional?  What would be involved?  Thanks--Ted
Re: How to link whole-house inverter to battery monitor
Reply #1 –
Yahoo Message Number: 136362
Ted,
 In theory,  it should be very simple.  Your inverter wiring is bypassing the battery monitor "shunt".  You would need to move one end of one wire so it doesn't bypass the shunt.  If you weren't hundreds of miles away I'd go back to the installer of the inverter to get it done right.
 You really need to understand the potential danger of working in that area.  For example, if you cause short with a ring on your finger, you could melt the ring and lose a finger.  Relatively immense energy is available at the batteries.  So, we forewarned.  If you have to ask the question, you may be better off letting someone else do it.

Alex Rutchka, SE #4 '05 MB
Re: How to link whole-house inverter to battery monitor
Reply #2 –
Yahoo Message Number: 136363
A battery monitor such as a LinkLite, LinkPro, or Trimetric relies upon a "shunt" inserted into the battery circuit as a way of measuring total current through the circuit. The shunt is a very precise high-current, low-resistance device that usually looks like a small stack of brass or copper plates on a plastic base. It's installed in the battery compartment, as close as possible to the batteries.

For the monitor to work, ALL current must pass through the shunt.
 The usual way to achieve this is to remove all the connections from the battery bank's negative terminal, run a short, heavy cable from that terminal to one side of the shunt, and then connect all the wires that used to go to the battery's negative side to the other side of the shunt.
 The key here is that *only the shunt* may be connected to the negative battery post. No other wires may go to that post. Everything has to go through the shunt--both charging and discharging.
 I don't know what kind of battery monitor you have, or how it's connected, but you should be able to assess the situation by eye. Most likely the person who installed the inverter connected it directly to the negative battery terminal, instead of connecting it to the shunt. Relocating that cable to the shunt should fix the problem.
 The usual cautions apply: while electrocution is unlikely with a 12V system, any mistake can result in large currents going where you don't want them, possibly resulting in fire, battery explosion and acid spattering. So wear safety glasses, don't wear anything metallic (e.g., watchband or other jewelry), and be extremely careful not to short together any two terminals with your wrenches or other tools.
 If you're not comfortable with this, get a professional to do it. It shouldn't be an expensive job--most likely the technician just needs to move one cable.

Andy Baird http://www.andybaird.com/travels/
Andy Baird
2021 Ford Ranger towing 2019 Airstream 19CB
Previously: 1985 LD Twin/King "Gertie"; 2003 LD Midbath "Skylark"
Re: How to link whole-house inverter to battery monitor
Reply #3 –
Yahoo Message Number: 136364
I have a Trimetric battery monitor.  Does that change your description of the process or prompt you to add anything?  Thanks--Ted
Re: How to link whole-house inverter to battery monitor
Reply #4 –
Yahoo Message Number: 136368
"I have a Trimetric battery monitor. Does that change your description of the process or prompt you to add anything?"

Nope. It's the same deal: EVERYTHING must pass through the shunt.

Andy Baird http://www.andybaird.com/travels/
Andy Baird
2021 Ford Ranger towing 2019 Airstream 19CB
Previously: 1985 LD Twin/King "Gertie"; 2003 LD Midbath "Skylark"
Re: How to link whole-house inverter to battery monitor
Reply #5 –
Yahoo Message Number: 136370
Quote
Days later, hundreds of miles down the road, I discovered deep discharging of the batteries not reflected in the battery monitor read-out.  Further investigation revealed that when the inverter was installed, it was not connected in the circuit to the battery monitor.  So now, the battery monitor is accurate only to the extent that the inverter is not being used.
If you think of the batteries as 'upper' - the one with the positive terminal connected to the 12V side of the wiring, then the ONLY item that should be connected to the negative terminal of the 'lower' battery is the cable from the shunt.

Steve
2004 FL
2013 Honda Fit