Instant, off the shelf battery capacity measurement
I've come up with a bulletproof way to test battery capacity. It does only work for 12 volts, but since I use a serial / parallel jumper plug to my 48V pack for charging, it is easy to tap the same pack for 12 volts as well.
I take a conventional 12V inverter. The one I have is 400Watts capacity. I hook that to my test battery with heavy capacity cabling. I then plug a "Kill-a-Watt" power meter into the 120V output of the inverter. I then plug a 275Watt resistive heater into the Kill-a-Watt.
The Kill-a-Watt will then monitor and total the electrical power used by the heater. A 275 Watt load means 2.3 Amps @ 120 Volts, which requires that the inverter draw 27.5 amps from the 12V pack. (Of course, the inefficiency in the inverter means that the actual draw on the battery is a little greater (by this source, that would amount to 6% more.
It can be as simple as a big resistor - as I showed in the 'Li-Ion cell testing' thread. And there are existing products available at auto parts stores everywhere for load testing 12v batteries, like these: Advanced Tool Design Model ATD-5495 125 Amp Fixed Load Tester and Battery Load Tester
If you're using the kill-a-watt for counting amp-hours, there's a simpler way. Both all-battery and batteryspace (see the links above) carry little power measuring widgets that connect in-line to a circuit and show volts, amps, can measure amp-watt-hours.
Another factoid is the official way to measure capacity is to draw from the battery at a fixed amps rate. That is, how many hours will the battery deliver 'n' amps. However batteries, especially lead-acid, vary the amps they deliver over time as the battery exhausts. This means the resistance of the load needs to decrease over time to keep the amps constant. Are you going to monitor the battery manually over the whole period of the discharge test? Again, all-battery and batteryspace (links above) both carry a computerized battery analyzer that's supposed to make this automatic.
Um, I didn't say "Load" testing. I said "capacity." The lnks you provided all seemed to allow a "stress test" of the maximum current the battery could deliver.
no, they were very much capacity.
the tests taking hours to do is the dead give away.
the DC watts up runs on 12v IIRC.
thats both Ah counter and Wh counter.