This all started when I bought an AMP Meter to monitor current draw on the house batteries. Here is a link to the one I bought.
http://cgi.ebay.com/3-DC-300A-Blue-LCD-Digital-AMP-Panel-Meter-Shunt-/250599217531?pt=LH_DefaultDomain_0&hash=item3a58e0 997b
Cost was $40.00 including the shunt. It takes a while because it comes from China.
Anyway I ran the wires, the hardest part of the install, to the House Batteries and installed the shunt in the ground leads going to the battery bank and it appeared to be working fine. The charging current was low but changing as I expected it to. I checked the voltage of the house batteries and at maintainers charge state they read about 13.4 VDC which I also expected. But this wasn't a "Load Test" so I used my 100 AMP load tester and for the ten second test recommended all was well. Now I decided to really pull some current and check the meter. So I unplugged the coach and turned on the inverter then started the Microwave on a Beverage Cycle. This is about a two min. run. When I checked the meter it read 177 AMPS being drawn out of the batteries, a little higher than I expected but a good test of the meter. After 30 Sec. of the Microwave running the inverter shut down the AC output for low voltage on the batteries and they read about 12.5 VDC. It became pretty clear to me that I had just discovered a better load test. 177 AMPS for two mins.. tells you if the batteries are really up to the load.
I went off to Sam's Club and bought four Golf Cart Batteries for $67.00 each, something I intended to do anyway since the original batteries were installed Feb of 2002. Ran the same series of tests and the only one producing differant results was the Microwave test. After two mins. of running the Microwave the voltage was at 13.2.
Conclusion: Although the load tester is a reasonable test for a very short time, the Microwave on the inverter is a more representative picture of the battery bank real condition.
Here is a picture of the new Batteries Installed.
Dick
Linear Mode
