Innova 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.

I bought this device as a visual backup, after experiencing flat batteries on a regular basis. I took my car into two repair shops and both said the battery tested ok but it was barely keeping charged up for more than a week. I decided it was time to replace the (stock, six year old) battery as that had to be the cause but wanted to make sure the new battery was charging (alternator was doing its job) and holding enough charge from the 23 mile round trip I do each day. Now I can clearly see that the new battery is charging as I drive (usually around 14.6 volts according to this device) and it also shows that when the car is parked, there is a slight draw but the battery rarely falls below 12.5 volts when sitting. I've left it in all the time (the draw is VERY low)except when I plug in my sat-nav but it has pretty much done its job already. It will be useful to have in the future though, if another car or a friend's car develops problems. For the cost, it is a great little device and was useful to show me that I made the correct decision to replace the old battery, even though the repair shops seemed to think the old battery was still ok.

When the cold weather hit the first thing to go was my car battery. I jump started the car and drove it on a few hour long trips in an attempt to recharge it. I had already ordered this product to see if it for one worked and secondly to see if it would give me an idea of my batteries condition. Again I jump start my car and now I plug this into the 12v port and it indicates that battery is charging while I'm driving. Another cold night and a third jump start get me going but now when I plug in the device I'm getting a charging warning. I turn on the heat after about 15 minutes of driving and now the device is telling me that my battery is failing to charge. With that I continued my drive right to the car dealer and I'm glad I did. The device was giving me very accurate information and if I hadn't continued to the dealer I would have had real problems. My car was ok. My battery had gone from 640 CCA's down to 32 CCA's and was unable to be recharged. It still has 3 months left on the 3 year warranty so the dealing graciously replaced my battery and restarted the 3 year warranty on the battery. I now have a monitor for each car and I would go out on the road without it. It gave me the info I needed to understand that I had a battery issue that had to be addressed asap. It also saved me from potentially being stranded out in the cold waiting for service which during this pandemic could have been hours. There are a number of these devices out there for sale but I can assure you from personal experience the INNOVA 3721 works flawlessly. It is also incredible easy to understand. The included instructions are written for drivers not auto mechanics.

The picture on Amazon site is not correct. This battery monitor shows the voltage value with .01 precision (or two digits after decimal point). That is far more then enough to tell the battery status. I put it in the car, it automatically switches between "battery status monitoring" and "charging status monitoring". When the engine is stopped, it is in "battery status monitoring mode", when engine is running, it will be in "charging status monitoring" mode. Amazon's price is even better then Walmart. Definitely a great value buy. Will recommend this item to my friends. --- Update --- Amazon has updated the new photo for the product. The picture is correct now. --- Update 5/30/2016 --- Lately, my wife's car won't start. I plug in this battery-Charging System monitor and turn on the power. The monitor shows 11.65V. Right there, I know something is wrong either with the battery by itself or the car's charging system. At this voltage level, the battery won't have sufficient power to crank up the engine. A typical reading before turning engine on should be around 12.34V. Nevertheless, I replace the old battery with a new one. The monitor now shows 12.30V when I turn on power. I drive around with the battery-Charging system monitor plugged in. I see voltage level is at 14.34V. That's good. This means the charging system is charging the battery. After driving around for about 15 minutes. I turn off engine. The monitor now shows battery is at 12.74V (higher then the initial 12.30V) . This confirms the new battery is taking charge from the charging system when I drive the car around. This battery-charging system monitor makes it easier to figure out if the battery goes bad or the charging system is not working correctly. Most mechanic will ask for a $120 diagnostic fee to figure out what is going on first, then additional charge for fixing the problem. I just save myself $120 diagnostic fee with this battery-charging system monitor.

This is the one to get! My job sometimes calls for sitting in the car while using an inverter to power a computer. I don't want to idle the car's engine the whole time I sit so I use this to make sure I don't drain the car's battery too much while the engine is turned off. Normally the battery is at about 12.6 volts with the engine off and nothing drawing power. If I go below about 12.2 volts I fire up the engine for a while to top up the battery. One day my alternator failed while I had this device plugged in. I was able to clearly see that the battery was not charging. During the drive to the mechanic's shop with the car's lights and all accessories turned off to save power, I was able to watch the voltage drop hundredth by hundredth as the reserve capacity of the battery was being used. The backlit display is clear and easy to view in all lighting conditions. For nighttime driving the backlight may be a bit too bright, however. Also, the green, yellow, and red status lights underneath the display are on the bright side for my liking. I took a single piece of white electrical tape and wrapped it across those three lights such that the ends of the tape are on the back side of the unit. I can still see the lights through the white tape at reduced intensity. After a short time owning this unit, I added an additional cigarette lighter socket and switch to my dashboard wired to the battery (with an inline fuse). Now this unit has a permanent home so I don't have to unplug it every day. The unit has been reliable for me for over a year (purchased in August 2015) being used just about every weekday.

The Honda 2005 civic has a marginal charging system. This meter is ideal for determining when it is time to turn off the radio to reduce load on the alternator. Voltage reading is very accurate, much better than 1% as measured against a small Beckman pocket meter, which in turn has been checked against a Powerex Wizard aa cell charger. Warning lights function well. Some things to note when using this tester: Standard voltage of a 12 volt battery is 12.6 volts. Some deep cycle absorbed glass mat batteries will read 12.8. This is after loading the battery by turning on the headlights for 10 seconds, to remove surface charge. Note that while the lights are on, the voltage drops quickly at first, then the voltage stabilizes. Turning off the lights causes the voltage to rise again gradually. After a few minutes the voltage will stop rising. If the voltage settles at 12.6 (or 12.8 for AGM battery) battery is charged, assuming that the battery is near 68 degrees F. Lower temps raise the voltage, higher temps lower the voltage. For a standard battery figure about 12.66 volts at 32 F and 12.54 volts at 104 F battery temperature, not air temperature. After a car has been running for awhile with no lights, radio, wipers, AC, heat or window defroster, the alternator may cycle letting the battery voltage drop for a while before kicking in. This is OK provided the charging is steady shortly after turning on the lights. An intermittant alternator will cause the red light to turn on and off when headlights are on. The bar graph for battery condition is not very useful as the meter has only voltage information. The instructions do not state that this tester is for negative ground cars only, a small quibble as positive ground is not common. Had I bought this device six months ago I could have avoided killing a brand new battery in six months. UPDATE: Still working fine as of May 21, 2013

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.