Battery status monitoring

[citylights]

Can I get some recommendations for battery status monitoring equipment?

Simple volt meter? All in one status unit?

[MtnDon]

A simple digital voltmeter can tell you a lot. AZ Wind-Sun has good info. Scroll down the page linked to and see the voltage / charge chart. There are some 'meters' that display by colored led's instead of numbers. I prefer the numbers.

Be aware that numbers can mislead when the system is under charge or recently has been charged or heavily discharged. Voltages are best after resting for several hours.

Upscale meters like the Bogart Trimetric can act more like a fuel level gauge after being setup, but are more costly.


For our CT we are using a digital meter. For our off grid cabin we use a more elaborate, expensive meter system from Outback (same mfg as the charge controller and inverter).

[MtnDon]

Of course, for a wet cell battery, one with removable cell caps, a hydrometer and thermometer are the most accurate method and permit comparing cells. Not applicable to AGM and other sealed batteries.

I take hydrometer readings every three months after a full charge and record the reading in a log for future use at our cabin. Not sure if I will carry the same routine through to the CT.

[bdosborn]

There are some low priced battery monitors but you get what you pay for.

A Turnigy meter is a great deal for monitoring power coming *out* of the battery but it doesn't track what goes back in:
Turnigy Linky

I'm starting to see some cheap battery monitors showing up on eBay but it's shipped from China (YMMV). Pretty cheap and supposedly tracks amp-hrs in and out. I haven't used one so caveat emptor:
eBay Battery Monitor

After that you can step up to the Cadillac meter - Trimertric/Victron/Xantrex (pick one). They work great but are big $$$$. They track amp-hrs in and out of the battery, and other battery parameters like last equalization, number of discharges, etc.:
Trimetric Linky
I have a Trimetric 2025 RV and love it (but I'm a bit obsessive about battery SOC). I like the Trimetric because it has a LED display and is a lot more visible (to me) then the LCD type.

And finally, a voltmeter will give you an educated guess at battery SOC and is the cheapest option:
Voltage versus SOC chart

Bottom line - precise battery SOC charge monitoring costs money, how precise do you want to be?

Bruce

[Shadow Catcher]

I went with a Victron battery monitor, in part because of small size and ease of setup and calibration.

[citylights]

Well, an analog and digital volt meter with a switch.

A little fun time in the garage, $10, and now the teardrop has a battery metering station.




Poor 9v battery got abused while I tested my circuit. Better this battery than the teardrop battery!




Analog volt meter

http://www.amazon.com/gp/product/B005116ULG/ref=oh_details_o06_s00_i00?ie=UTF8&psc=1

Digital volt meter

http://www.amazon.com/gp/product/B00B689UGA/ref=oh_details_o07_s00_i00?ie=UTF8&psc=1

The switch I just picked up at an auto parts store, but here is one too...

http://www.amazon.com/Rocker-Toggle-Switch-On-off-Control/dp/B007TQ2PRO/ref=sr_1_10?s=automotive&ie=UTF8&qid=1400274635&sr=1-10&keywords=12+v+switch

Used speaker wire for the connections. I mounted them in a spare piece of 1/8th inch plywood and painted it black. I tested the circuit with the 9-volt battery. The switch with light was driving me nuts with its three connection points! The first time I wired it I shorted the battery. No big deal on the 9-volt, it just got warm. It would have been a bigger deal on a 12-volt teardrop battery! So when I was happy with the way the circuit was running, I installed in the teardrop and connected to the 12-volt battery.

The key to reading this is a charged 12-volt will read up to 12.8 volts or maybe a little more. As the battery discharges, the voltage will drop to around 12-volts. That is where you want to stop using it and recharge. Letting the voltage drop much more than 12 volts is going to shorten the life of the battery.