by Barry and Cindy 1997 U270 36′ 3/1/2008
When we bought our coach (pre-owned), we found our dry-camping ability to be ok and assumed both house batteries (gel 8D) were serving us well.
A few months later, I bought two shunts and put one on each battery. I ran the small wires from the two shunts up into coach to meters above the dash, so we could read amps going in or out at any moment from EACH battery separately.
Low and behold, I found that one of my two parallel wired gel 8d MK batteries was always zero amps, on charge or discharge, so we had been happy on just one battery.
I could not have known if one battery was ‘dead’ without a separate shunt on each battery.
When I swapped battery positions, the zero amps moved with the battery, so it was not a cable problem. Foretravel swapped out both batteries and we are still going fine 5.5 years later
I have used Deltecco model WB Shunt types for surface mount. But I like Delteco model WO2 types for direct mount on battery’s ground terminal. Other Shunts at empro shunts
I use 500 amp / 50 millivolt shunts. That way amps are a ‘direct’ readout by just moving or eliminating decimal points on the meter. 500 amp draw displays as 50 on the meter (millivolt scale). Just add a zero and you have amps. 100 amps display 10, 50 amps display 5. In all cases add a zero.
Shunts are very inexpensive. Our costs have been $9 to $15 each, with none purchased in the last 5 years.
And almost every digital multi-meter measures millivolts. Even small $10 Harbor Freight meters. There are also inexpensive millivolt panel meters. Cheapest being 9-volt battery operated (needed to separate meter-battery from measuring-battery).
Any decent twisted-pair cables can be used to connect shunts to the meter.
This is one of the most important areas of battery management, yet it is not mentioned by RV manufacturers. Multiple parallel wired batteries in a bank often may not equally share in the load. And if a battery has an ‘open’ cell, that battery performs just like it is not installed.
Most of the time, batteries of the same size & age work well together, but there is no way to know about differences without a shunt on each battery. For less than $50 to $100, amp measuring for a couple of batteries is possible.