DC Watt Hour Meter

[Perry]

Seems like waiting for 2-3 hours for the batteries to settle out and measuring the voltage is an inconvenient way to determine state of charge and know when the batteries are getting too low.


I think something like this would be on my wish list to keep track of the watt-hours going into my batteries:

http://www.rc-electronics-usa.com/ammeters/rv-battery-monitor.html

If I also got a Kill-a-watt meter (on the output of the inverter), I could keep track of the power produced by the panels and the power used by my loads to see how the system was running.

I could also get an idea when my batteries were at 50% so I would know when to start worrying.....

[Sunking]

I think something like this would be on my wish list to keep track of the watt-hours going into my batteries:

http://www.rc-electronics-usa.com/ammeters/rv-battery-monitor.html

Those are useful but you would really need two of them. One on the output of the charge controller to see what is going in the batteries, and one on the load side of the batteries.

However there is a way to just use a volt meter using SOC voltages, but it takes work on your part, but requires you to have a very accurate hydrometer with temperature correction. Rather than me write it again click this link for the procedure. and scroll down to
To determine or verify the 50% voltage set point:
[LIST=1][*]Put all or as many loads as possible on the battery. Disconnect any in coming current inputs such as panels / windmills and grid power. Contact your dealer for specifics.[*]Take the specific gravity of one cell.[*]Take another reading 15 minutes and

[Paul54]

Seems like waiting for 2-3 hours for the batteries to settle out and measuring the voltage is an inconvenient way to determine state of charge and know when the batteries are getting too low.


I think something like this would be on my wish list to keep track of the watt-hours going into my batteries:

http://www.rc-electronics-usa.com/ammeters/rv-battery-monitor.html

If I also got a Kill-a-watt meter (on the output of the inverter), I could keep track of the power produced by the panels and the power used by my loads to see how the system was running.

I could also get an idea when my batteries were at 50% so I would know when to start worrying.....

I use 2 of the RC-Electronics meters on my smaller DC only system. But like Sunking says you really need two. One to measure how much charge is going in to your batteries, and one to measure what you are taking out. They are a great tool to fine tune a system to get a good balance between charging and consumption. They have a limit of 60 amps of current flow through them, but for the money they really are quite amazing.

[Perry]

But like Sunking says you really need two. One to measure how much charge is going in to your batteries, and one to measure what you are taking out.

If you are only using 120 V AC loads, you can use a Kill-A-watt meter to measure what you are taking out of the batteries. The Kill-a-watt meter is only $20 and it will handle much larger wattage loads..

[Paul54]

The Kill a Watt meter is a great tool, very reasonably priced. But I still like to have some way to measure how much I am producing on the DC side. Once you know what kind of loses you have on the output side, a Kill a Watt meter is probably all you would need. My biggest concern is to not over discharge my batteries. I know how many amps I can pull out to stay within a certain rate of discharge. Having a meter on both sides makes it real easy to see how much DC power I am taking out and at what rate. I can easily see if I am replacing the power and doing it at the right time.

[Perry]

The only problem with "measuring DC amps (or watts) that comes out of the battery" is ....

if you use something like a skill saw that draws 13 amps at 120 volts, it will be sucking 130 amps from your batteries. You would need a bigger DC amp/watt meter than the one from the link.

I went to the auto parts store and got a Battery Hydrometer. This will tell you the actual state of charge of the battery.