--- product_id: 1832205 title: "3721 Battery and Charging System Monitor" brand: "innova" price: "€ 55.27" currency: EUR in_stock: true reviews_count: 7 category: "Innova" url: https://www.desertcart.fr/products/1832205-3721-battery-and-charging-system-monitor store_origin: FR region: France --- # Clear LCD bar graph display Instant plug-in power check Color-coded LED battery status 3721 Battery and Charging System Monitor **Brand:** innova **Price:** € 55.27 **Availability:** ✅ In Stock ## Summary > 🔋 Stay charged, stay ahead—never get caught powerless again! ## Quick Answers - **What is this?** 3721 Battery and Charging System Monitor by innova - **How much does it cost?** € 55.27 with free shipping - **Is it available?** Yes, in stock and ready to ship - **Where can I buy it?** [www.desertcart.fr](https://www.desertcart.fr/products/1832205-3721-battery-and-charging-system-monitor) ## Best For - innova enthusiasts ## Why This Product - Trusted innova brand quality - Free international shipping included - Worldwide delivery with tracking - 15-day hassle-free returns ## Key Features - • **Smart LED Alerts:** Color-coded LEDs provide quick, intuitive battery health status—know when to act before it’s too late. - • **Visual Voltage Clarity:** High-contrast LCD with bar graph lets you instantly gauge battery charge levels at a glance. - • **Adjustable Viewing Angle:** Pivoting head design ensures perfect visibility from any driving position or workspace. - • **Plug & Play Battery Insight:** Simply plugs into your vehicle’s 12V power port for real-time voltage monitoring—no installation hassle. - • **Engineered for 12V Negative Ground Systems:** Precision monitoring tailored for modern vehicles, protecting your engine computer and accessories. ## Overview The Innova 3721 Battery and Charging System Monitor is a compact, plug-in voltmeter designed for 12-volt negative ground vehicles. Featuring an easy-to-read LCD bar graph and color-coded LEDs, it provides instant, accurate battery and charging system status. Its pivoting head ensures optimal viewing angles, helping professionals and enthusiasts alike prevent unexpected battery failures and protect vehicle electronics with confidence. ## Description The INNOVA Battery and Charging System Monitor displays the condition of your battery and charging system instantly. It protects the engine computer and 12-volt accessories from damaging surges when jump starting or recharging. Easily plugs into the vehicle's cigarette lighter or power receptacle to monitor battery and charging system voltage. The LCD screen displays the measured voltage with a bar graph to indicate battery charge level and the color-coded LEDs quickly identify the battery's charge status. The head pivots for easy viewing and angle adjustment. Review: Having both a Light and Digital Display is worth it. - 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). Review: VERY GOOD FOR SUCH A LOW PRICE - 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 ## Features - Easily plugs into vehicle’s cigarette lighter or power receptacle to monitor battery and charging system voltage - Designed for 12-volt negative ground systems - LCD displays measured voltage with a bar graph to indicate battery charge level - Color-coded LEDs quickly identify battery’s charge status - Head pivots for easy viewing and angle adjustment ## Technical Specifications | Specification | Value | |---------------|-------| | ASIN | B000EVWDU0 | | Best Sellers Rank | #100,339 in Automotive ( See Top 100 in Automotive ) #120 in Battery Testers | | Brand | Innova | | Color | black | | Customer Reviews | 4.4 4.4 out of 5 stars (2,626) | | Date First Available | July 7, 2004 | | Global Trade Identification Number | 00042173037216 | | Is Discontinued By Manufacturer | No | | Item Weight | 3.2 ounces | | Item dimensions L x W x H | 10 x 1 x 6.5 inches | | Item model number | 3721 | | Manufacturer | Innova | | Manufacturer Part Number | 3721 | | Measurement Type | Voltmeter | | Min. Operating Voltage | 12 Volts | | Model | 3721 | | OEM Part Number | 3721 | | Power Source | Corded Electric | | Product Dimensions | 10 x 1 x 6.5 inches | | Style | 12-volt | | UPC | 077344875533 043944196088 604945305505 042173037216 043993994284 074994532588 | | Voltage | 12 Volts | ## Product Details - **Brand:** Innova - **Color:** black - **Item Weight:** 3.2 ounces - **Power Source:** Corded Electric - **Style:** 12-volt ## Images ![3721 Battery and Charging System Monitor - Image 1](https://m.media-amazon.com/images/I/71M5TQTAY8L.jpg) ## Customer Reviews ### ⭐⭐⭐⭐⭐ Having both a Light and Digital Display is worth it. *by F***Y on October 9, 2016* 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). ### ⭐⭐⭐⭐⭐ VERY GOOD FOR SUCH A LOW PRICE *by J***T on November 11, 2010* 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 ### ⭐⭐⭐⭐⭐ Review *by A***R on May 4, 2016* 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 ## Frequently Bought Together - Innova 3721 Battery and Charging System Monitor - 12V Plug in Car Battery and Charging System Tester, Test Battery Condition & Alternator Charging (LCD Display Car Battery Monitor) - NOCO GENIUS1, 1A Smart Car Battery Charger, 6V and 12V Automotive Charger, Battery Maintainer, Trickle Charger, Float Charger and Desulfator for Motorcycle, ATV, Lithium and Deep Cycle Batteries --- ## Why Shop on Desertcart? - 🛒 **Trusted by 1.3+ Million Shoppers** — Serving international shoppers since 2016 - 🌍 **Shop Globally** — Access 737+ million products across 21 categories - 💰 **No Hidden Fees** — All customs, duties, and taxes included in the price - 🔄 **15-Day Free Returns** — Hassle-free returns (30 days for PRO members) - 🔒 **Secure Payments** — Trusted payment options with buyer protection - ⭐ **TrustPilot Rated 4.5/5** — Based on 8,000+ happy customer reviews **Shop now:** [https://www.desertcart.fr/products/1832205-3721-battery-and-charging-system-monitor](https://www.desertcart.fr/products/1832205-3721-battery-and-charging-system-monitor) --- *Product available on Desertcart France* *Store origin: FR* *Last updated: 2026-04-23*