I have a new DC panel with a digital multimeter.
In my Don Casey book, there is a section on voltage and remaining capacity. It shows 12.2 as 50%. If this is the lowest point I want to bring my batteries before recharging, then I need to confirm is it when meter is showing 12.2 when nothing is running or when something is running (e.g. refrigeration)?
For example when nothing is running I could be seeing 12.32 and when refrig kicks on drop to 12.22. Then comes back up to near previous number when the refrig stops.
Thanks
-PC
Pierre : The Don Casey number is close to the one that I use for the 50% battery voltage. The one that I use for 50% and (I published a graph in the Mainsheet tech notes) is 12.25V for a wet cell. 12.75V being 100% and 11.75V being 0 or flat.
Just remember that this reading is a static (at rest) reading and many minutes after consumers like the fridge kick off. The real health check of a battery is not only the static V reading, but a load test !!
Also remember that the lower the drawdowns each time (maybe only 75% or 12.5V) the more it helps "increase" the number of cycles that that battery bank can produce. A thought
Voltage alone is a very misleading indicator of battery health and/or capacity. To use it the batteries must have been at rest for over 12 hours.
Please read the Power Primer at www.amplepower.com, technical tab. It's THE document I've found to be honest, straightforward and REAL about taking care of batteries.