Equus Battery Monitor

[Paul Braun]

Eric T recently posted a message on another forum containing a link to a battery monitor that plugs into a 12 volt outlet and gives measurements of what charge is left in your battery. I found the unit is only available from Amazon, and will run about $18 US with shipping. Here is the link and description:

http://www.amazon.com/Equus-3721-Battery-Charging-Monitor/dp/B000EVWDU0/ref=sr_1_1?ie=UTF8&s=automotive&qid=1280538628&sr= 8-1-spell

I took some time on a recent week long trip to compare the Equus battery monitor that Eric recommended with hydrometer readings. Supposedly hydrometer readings are the most accurate method of measurement short of having expensive test equipment.

I would have to say that hydrometer readings are difficult, touchy and the instruments suffer from poor quality. It took me two purchases to find a working model and the second model is going back as it has filled itself with battery acid and it cannot be easily drained. It is also made of glass. The inexpensive hydrometers give readings on a scale with tick marks between numbers, the glass insert must be balanced so it is floating in the acid you have drawn from the battery. In addition, you must add or subtract depending on what the thermometer tells you. In all, I felt a cumbersome process that is easily skewed. There may be better models available but after visiting four stores I felt I selected the best available, it was less than $6.

Below is a table of what I found with readings from the Equus battery monitor and a hydrometer test. As you can see there is a pretty good correlation of results. I really distrust the hydrometer readings because there is so much chance for error and obtaining a precise reading.

In conclusion, if you boondock, have a 12 volt outlet and want to monitor your battery this definitely beats running hydrometer tests on your battery. You have a precise number and can even tell what power a particular device is drawing by running it and seeing the monitor change. I recommend a hydrometer for occasional (seasonal) testing on all the cells on your battery but if you want to to easily watch your battery the Equus batttery monitor does the trick.