Review on 🔋 Battery Monitor and Voltage Capacity Tester for 12V, 24V, 36V, 48V, and 60V Iron-Lithium & Lead-Acid Batteries – Battery Capacity Indicator with Voltage Capacity Percentage by Joseph Long

As a very active electronics enthusiast I use a lot of batteries and battery packs. I typically use two types of batteries here - a 12 volt lead acid "gel cell" and lithium ion batteries with different cell counts depending on the voltage I need. I bought this battery voltage monitor to add to one of my battery packs so I can easily see the status of the battery pack. The device came in a nice little box in a padded envelope. Arrived in perfect condition, no damage. The box contained a gauge, a couple of wires connected to a connector, a piece of foam to cover the back of the gauge, and four mounting screws, two round head and two countersunk. . The device didn't come with printed instructions, but instead had a QR code sticker that instructed the user to scan a code for a link with instructions. Instead I just followed the instructions in the Revain product description. Following the instructions I had no problem setting up the unit for either a 12 volt lead acid battery or a different number of lithium ion cells. There are some reviews here claiming the instructions are wrong, but I found the instructions in the Revain product description to be spot on: hold the button, turn it on, release the button, then use the button to select the correct battery type. and cell count. 1P is 12V lead-acid battery, 2P is 24V lead-acid battery, etc. 1c is single-cell Li-ion battery, 2c is two-cell Li-ion battery, etc. Please note Make sure the device is rated for at least 8 volts. This is important - the device is powered by a fully charged 4.2 volt lithium-ion battery, but without a backlight as the voltage is too low. You can set it to a single cell lithium ion battery with the "1c" setting, but the device will not work properly as the voltage is below the minimum 8 volts. If you set it to the "2c" setting and connect it to a 2-cell lithium-ion battery, the device works properly, but below 8 volts the backlight becomes very dim. So a 3 cell lithium ion battery is probably the lower cell count limit for this device. Other reviews mention that the backlight only stays on for a short time. In my testing, I found that it turns on the first time I turn it on and doesn't turn off. I'm not sure if the design of this block has changed over time, but at the time of writing this (late August 2020) the backlight is on all the time, except when the battery voltage drops to 0% - the block turns on off the backlight. This is very clever - since the block with the backlight draws about 5mA and without it it's so low that I can't measure it. Monitoring the state of charge of a battery (% full) by measuring voltage is very difficult - there are many variables and parameters that affect the measurement. For example, a fully charged lithium-ion cell will measure 4.20 volts, while the same cell charged at 1.5 amps now drops to about 3.90 volts. To see how accurate this meter is I ran some tests on the 1P setting and the 3c setting and applied different voltages to see how full the meter was. The results are shown in the graph. In my opinion, this meter works very well! I don't want to discharge my gel batteries below 11 volts with no load, so a value of 0%, which is 11.03 volts, is ideal. A fully charged gel cell will measure around 13 volts with no load, so 13.04 volts is ideal for 100%. Looking at the diagram of a three-cell lithium-ion battery, 9.34 volts at 0% equates to about 3.1 volts per cell. In my opinion this is correct. 12.47 volts equals 4.16 volts per cell, which again is correct! It is important to note that the curves have different shapes: a lead-acid battery tapers off slowly, while a lithium-ion battery has a sharp drop below 10%. Both correspond to the discharge curve of the battery chemistries involved. The device has good input filtering and takes a while to reach 100% when first plugged in. This is good as it ignores sudden voltage changes and prevents unstable readings. In summary, this is a great product. It is well packaged, I found it exactly as described in the Revain product description and it works very well. I will definitely buy more of these devices in the future.