DROK Digital Multimeter DC 6.5-100V 20A Voltage Amperage Power Energy Meter, DC Volt Amp Tester Gauge Monitor LCD Digital Display with Built-in Shunt

So I bought this as an indicator for a 24 volt solar power system built into a tote. I found that it worked very well although as others have mentioned, it needs some sort of enclosure so I designed and 3D printed a suitable housing for the shunt. This worked great for me. One thing to keep in mind is that the quality of the wire connections to the shunt and the battery are really critical as far as accuracy. The shunt itself is only a few milliohms of resistance and the voltage drop across that is very small, so the slightest bit of extra resistance introduced by a substandard connection on one of the wires will completely throw the readings off. Use really good quality crimp ons and then solder the wires after they're crimped. If you do that and follow the installation instructions to the letter, there shouldn't be any issues with accuracy. I don't know about longevity at this point but for the price this is a really good meter.

The meter works as advertised and for the price it has excellent value. Note that the current meter is in the negative side between DC IN - and Load -. This is important if you use a switch, like I do, to change the meter's polarity between charging and discharging a battery. The current meter will not run backwards. In other words, the meter will only increase its reading when positive current flows in the direction of DC IN + to Load +. Current will flow in the other direction, but the power and current meters will not read negative values, and the Watt-hour meter will not decrease its reading.To use the meter to monitor power from a solar panel to a battery, I connect the solar panel to the DC IN + and DC IN - terminals, and the battery itself to the Load + and Load - terminals. When discharging the battery into the intended load, I reconnect the meter (using a switch) into its conventional connection topology. Since the current meter is in the negative side, DC IN + and Load + are connected together in the unit. In other words, they are the same node.The unit is made to mount in a square hole in 0.032" thick material. I used a thin bead of Silicone adhesive around the bezel to strengthen this mechanical connection.The operation of the screw terminals can be confusing, and can lead to damage if one is not careful. They come tightened down, so to connect a wire first loosen the terminal by turning the screw counterclockwise several turns, insert the wire in the gap that's just been opened, and then tighten the screw in a clockwise direction. I verified that the terminal block will accept 12 gauge wire.

UPDATE:After about a month of solar panel monitoring I decided to upgrade my wiring setup to monitor the output side of my charge controller instead of the line from the solar panel. When I went to remove this from the circuit, I was surprised to see the accumulated energy field read 238 Wh when it last read 1058 Wh. It should have stayed in 4 digit Wh range or at most switched to kWh readings. There's no way my 15w panel could have generated the 9,998-odd kWh necessary to roll the display.Mine also isn't showing the right voltage anymore. A 12V DC supply applied to the line side reads about 19V yet the output side reads 12V with a multimeter. When new, the display was very accurate.I still like this meter, but obviously something is wrong with mine.This is a pretty slick tool -- my review is probably closer to 4.5 stars, excellent but not quite perfect. The screen is very easy to read even in outside daylight and it draws very little power -- my 15w solar panel will light this up with a no-load indicated voltage of 13w under fluorescent lighting. For me the killer feature is the energy (watt hours) figure and the fact that it has memory and will retain this value even when it loses power, which is important for my use of monitoring the net energy production of my solar panels.My only complaints are pretty small -- the wiring terminals are kind of tiny, and while they accept the 16ga wiring my 15w panel uses the little flat head screws are tough to screw down securely. A molex type socket would be a lot more secure. The only other thing I wish was a "factory" option is a pre-fit project box for this. I bought one that's a pretty good fit, but had to do my own cutout in the lid and tap and seal my line and load holes.I plan to use this between a solar panel and a charge controller to determine how much charging my panel actually accomplishes. It's a 15W nominal panel and in theory even at a daily average of 5W I figure I should be getting around 50Wh worst case out of it. For a panel that sits out in direct sun, I *should* be adding 250Wh or 20Ah to my 12v battery for the 5 days it sits unused yet last summer the battery stopped holding a charge completely. This monitor will clear up whether the battery just gets overused or whether the panel isn't supplying meaningful power. I notice this vendor also sells battery monitors and I may add one of those plus another one of these on the load side of my battery to figure out what my power drain is; I may just be using more power than my alternator plus solar panel can put back in.If the vendor ever gets into more complex products, this would be an awesome thing to add networking to for remote monitoring.

Using this on my electric bike. It's working perfectly so far

This meter does a good job for my purpose. I bought it to monitor the charging voltage and current for my ebike. You must hookup the wires per the instructions or you will not get a correct reading. I experimented with the hook up to see what would happen and it makes a difference. This meter does not actually monitor the current directly. It measures the voltage drop across the shunt and it is important that the shunt is the last part of the circuit per the instructions. I 3D printed a case to contain all of the wiring and it turned out to be a good tool for my needs.

Worked great, right out the box. The wiring instructions are on the multimeter and are extremely easy to follow. I liked it so much I just ordered two more.