3721 Battery and Charging System Monitor

Nice to have a device that has both "Quick" and More Advanced Features to display how a 12 volt system is working. So far I've used it with my Car and to check a couple of "Booster Packs" (to verify how much a "full" charge or 1-2 green lights equals in Volts). Had been debating about getting a cheaper model with only a Digital Display... While that'd work... Having a simple at a Glance option for knowing if it's Ready or Not (or Maybe) is helpful. Less guess work and distraction... I also like the estimated charge level icon... while it doesn't seem to be very consistent I'm not sure if it's because of the gauge or the battery/car/driving style I have. Usually shows Full to 50% charge when I'd assume it'd always be 75% or better. Could just be misguided expectations, assuming my Charging System is Perfect and the Batteries are Excellent. Why did I buy this Tester again? That's right to scientifically verify what's actually happening. Looking forward to testing it more now as the Temps fall and I have a baseline for comparison to see if my Batteries are doing their Job as they are demanded to perform more. Should be worth it just to confirm a good Jumper Connection/Voltage in the Middle of Winter when multiple failures to start are not good for many reasons. If Both Batteries go "green" or I can raise the Voltage of the "dead" Battery I know I've got a better chance. No guessing/crossing fingers, I'll know what to expect and anticipate perform, or make adjustments if the Voltage doesn't maintain itself. Update: 2/17/19 Still working hard for me everyday. Was extremely useful about 2 years ago when I unexpectedly "lost" (Shredded) my Serpentine Belt at night. Had to run on Battery Power for 10 Minutes. Heard it go out and my Vehicle's Battery light came on I was able at a glance to see the Battery wasn't charging and how much voltage it had. Was able to dim the instrument lights, turn off/unplug all but the necessities and make it home. (Then the Mechanic, the next day... After a "top off" charge) More recently as I noticed my Battery was approaching 5 years in Service, while it still started and "performed" as I was accustomed to it... even after a top off charge I'd often see the monitor report a State of Charge between 25-50% after a short time (say next morning). While not something I (or the manual) trust to be 100% accurate... (Different 12v Outlets, Extension Cords, or conditions can throw it off and give different readings) You do get a feel for what it should read before Starting the Car in the Morning or how low it should get if you're just sitting with the Radio On for 10 minutes after a drive. Based on the suspicion it was on it's last legs and it was still under a Pro-rated Warranty (Spoilers! Got $12 (12 months) back). Decided I should buy a Digital Load Tester to confirm it needed replacing. It matched the Store's assessment Replace 515CCA Battery that should be 690CCA. Its been a great tool and now that I have a few other testers ( and battery chargers) I can follow up on "odd" readings and narrow down if it really is the battery, alternator, other device(s) at fault. Often take it along in other vehicles on road trips just to check the vehicle (and Jumper Packs, etc. are working).

When my car's charging system light began coming on randomly I checked the battery and alternator without finding a problem. The fault was too intermittent and short lived to diagnose, so I bought the Equus 3721 to verify that when the charging system light came on, my alternator was still delivering power. The unit is simple to use, plugging directly into any cigar lighter outlet / power port. By using the port under my radio I could monitor the system voltage and watch what it was doing when the warning light came on. This allowed me to both determine that it was not a failure of the alternator to produce power, and also have confidence that nothing bad was about to happen (dead battery from lack of charging). The Equus has a digital display which shows instantaneous system voltage, a bar showing battery condition and three LEDs which give a quick indication of system health. It also has a hinge where the meter joins the socket connector shaft. This allows the unit to be angled to improve readability. This device is great for a situation where you need to know what your voltage is doing right now, with precision to the hundredth of a volt. For the price it is a good value.

I purchased this battery voltage meter back in 2013 when a car I had was giving me hard time with the battery. I now have a different car that I purchased a couple of years ago and last year the dealership replaced the battery under warranty but this winter I started having battery problems again and so I dusted off this meter and plugged it in to try and get a better picture of what is going on with this battery. First, let me say that all that matters is the voltage reading and the green, yellow and red led indicators on it are useless and pointless. Now, let me say that the bar graph to the right of the voltage reading and the symbols above that are also useless and pointless. Once you understand the voltage numbers that you see you will find this to be a very useful tool and if you are willing to read further, I will attempt to explain the voltage readings you will get. If you do not want me to bore you with details, all you need to do is plug this in and get 12 to 13V while the car is not running and get 13.5V or more while the car is running. Checking your battery's health: A lead acid car battery is typically 12V but a healthy fully charged 12V battery that has no load connected to it will give you a reading of 13V or a little over that. A car battery under normal load (not cranking the engine but have the ignition key turned to on without the car running) should not give you a reading of less than 12V. If you plug this meter to your receptacle and turn the ignition key to on (engine not running) and you get a reading less than 12V, your battery needs to be charged soon. Most cars will not crank "happily" if the battery voltage is less than 12V before you start cranking. Based on this, if you want to see how is the health of your battery, you should get in the car after the car has been off for more than 12 hours, turn on the ignition (do not start the car) and take a reading. The reading should not be less than 12V and the higher it is the better the battery is doing. You should not expect that you will see the "fully charged, no load" reading of 13V because unless you have an antique, your car uses battery power even when the ignition is off for many things including waiting for you to press the buttons on your keyfob or turn on the dome light when you come close to your car door with keyless entry. The truth is that the best indicator of your battery's health is how fast the battery discharges under load but you will not know how much "load" is on your battery while you are taking the voltage readings so it is hard to explain this in a review. Checking your charging system (alternator) health: When your car is running, the alternator is charging the battery. To do so, it has to provide higher voltage levels than the battery itself so the battery can be charged. A typical alternator will provide 14V to 15V while the car is running but alternators are not like generators and they need to keep adjusting the output voltage with a circuit called the regulator because the engine revs are rarely constant. Because of this, when you take voltage readings while the car is running, you may see the voltage move up and down and seem unstable. However, you should not see the voltage jumping up and down more than a few tenths of a volt constantly. So to see if your car's charging system works well, plug in this meter and start your car. You should get a reading close or a little more than 14V but generally readings between 13.5V and 15.0V while the car is running are good and this means that your car is charging the battery. Having said that, contemporary charging systems may monitor the amount of amperage that the battery is drawing and stop charging the battery because it is fully charged. In this case, you will see readings of less than 13V while the car is running but that will be short lived because the battery will not be fully charged for long and the voltage should jump back up to start charging it again. In conclusion, this is a useful tool and I do not like to have it plugged in all the time but if you doubt your battery's health plug it in and get some readings. Don't let the led lights get you dizzy because they mean nothing. To have any meaningful indication from the led lights and the bar graph, this unit would need to be calibrated to your specific car. You could get the same readings from a digital multimeter or even this inexpensive voltmeter ( Green Dc 4.0-30v LED Panel Digital Display Voltage Meter ) but it is worth every penny to have the voltmeter in a package that plugs in your car and swivels. As for my battery, I was getting readings of 11.6V every morning and if I would leave the car at rest for more than 24 hours, it would go below 11V. So I replaced it myself and did not trust the dealerships batteries for the temperatures in the northeast so I got one that was made for colder climate.

Works fantastic for my Rv . I now Always know exactly the level of my battery's . I compare the voltage on the Innova 3721 with my Multimeter and it's exactly the same. Great product

Gives me the information I need to check my battery & alternator condition as I've been having issues with my battery.

Item worked well. Did what was advertised.

Para de un golpe de vista saber como esta la carga de mi Batería

Very good product, works as it should.