Bosch C3 Fully Automatic 4-Mode 6/12V Smart Battery Charger and Maintainer (3.8 Amps)

The Bosch C3 battery charger is a "smart" charger, which detects the voltage of your battery and decides if it is 6V or 12V, and then charges accordingly. However, there is a very serious flaw here. What if your 12V car battery is heavily discharged to a voltage less than 6V?

Answer: the charger fails, it will NOT recharge your battery back to 12 Volts.

If your battery currently is discharged to less than 6 volts the C3 "smart" chip presumes that your battery is therefore only a 6V battery, and will charge it only to 6 Volts, not the 12 Volts which you need. There is NOTHING you can do to get it to charge to 12V if the charge has drained briefly to less than 6V, regardless of the age or quality of your battery. You are out of luck.

So, a great battery charger if you only need to "top it off", but it will fail you completly if you left your dome light on while away on vacation and then need to recharge back to 12V. That is what happened to me, and I had to go out and buy a different brand battery charger to recover the 12V charge in my perfectly good car battery.

Not worth it.

Chargers have come a long way since I was a new driver back in the 60's. The boxy chargers have been replaced with this modern device. They are no longer a shock hazard and much safer. No metal cabinet to rust. This unit is small and computer controlled with obvious advantages for both. It looks like it will last a lifetime with normal care. This sure makes the task of keeping you batteries in shape a simple task. I feel very safe using this over the old lead acid rechargers I grew up with. I still would use it with a ground fault protector just to be safe on wet floors or humid conditions, but it just looks and feels safer to me. I am happy to have this fine product from a great name, Bosch.

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I've had this charger for almost 2 years. At first I was quite impressed with the design and seemingly high quality. It did a good job charging a riding mower battery and car batteries. However, I quickly began to miss my old analog battery charger that was over 30 years old and had a quick charge function.

The "smart" functions interfere with some of the things I needed to do--charge a really drained 12V battery (it couldn't accurately determine whether it was a 6V or 12V), or charge a battery pack that was neither 6V nor 12V. Yes, I realize this a safety feature but I'm smart enough to know how to charge a battery correctly manually.

I've grumbled and put up with it (especially when it would go off when the power was cut and then not come on automatically), but I recently discovered it is no longer responding to the push button. I have to spend 5 minutes squishing or rubbing it in every direction before it apparently makes contact inside and changes the mode. Very very frustrating.

Here's the kicker: Although it has a 2-warranty, Bosch states, "The limited warranty further excludes normal wear and tear on parts and damage to fragile components (e.g. switches)." Seriously??? The ONLY moving part on this unit and it's fragile? Not worth the money if it's going to fail before 2 years.

Read Best Reviews of Bosch C3 Fully Automatic 4-Mode 6/12V Smart Battery Charger and Maintainer (3.8 Amps) Here

Upon unboxing the Bosch Model C3 6.3/12.6 VDC Battery Charger, it is immediately evident that this is a high quality product characteristic of the Bosch name. The C3 is very compact compared to the old car battery chargers of the past. The charger is constructed of a high impact plastic and therefore not susceptible to rusting as were the old metal box chargers. All mode and status displays are on the front of the charger, as well as the single mode select button. The C3 is equipped with a heavy duty 120 VAC power cord as well as a durable DC charging cable. The DC charging cable is equipped with in inline disconnect, allowing the supplied insulated alligator clips to be left connected to the battery between charges. The DC charging cable is also equipped with an inline 10A automotive type fuse to provide short circuit protection to the C3 charger.

The Bosch C3 battery charger is microprocessor controlled and hence should be considered a "smart charger". The C3 is designed to the sense the charge state of the battery, as well as determine the appropriate charge rate. The C3 can provide a pulsed charging current of up to 3.5 A for deeply discharged batteries, as well as provide a low current trickle or maintenance charge. The C3 continuously monitors the battery charge state and automatically reverts from pulse to trickle charging when the battery is fully charged.

The Bosch C3 battery charger was tested on a moderately discharged Delco S2000 115 AH deep cycle battery. As expected, the C3 immediately switched to pulse charging, remaining in the pulse mode for approximately 7 hours before reverting to a trickle charge mode.The Bosch C3 battery charger performed flawlessly.

The 36 page Bosch C3 instruction manual is very well written and printed in 3 languages, English, French and Spanish. Bosch strongly emphasizes operating safety. The manual clearly addresses the potential for charging wet cell batteries to "off gas", thereby creating an explosive atmosphere. Therefore, the charger should never be connected or disconnected from the battery while the battery is charging. Bosch also cautions the user from operating the charger in wet conditions.

Bosch emphasizes that this charger is only designed to charge 6.3 or 12.6 VDC wet cell or gel cell rechargeable batteries. It is not designed to charge dry cell batteries.

The Bosch C3 Automatic Battery Charger is packaged with the C3 automatic charger, a battery charging cable equipped with a disconnect and an inline 10 A automotive fuse, red and black insulated heavy duty alligator clamps, a removable hanger and an operating manual. Bosch provides a generous 2 year limited warranty on parts and workmanship.

The Bosch C3 Automatic Battery Charger is a high quality product that should provide many years of reliable service when used in accordance with the supplied operating instructions. Although the C3 isn't designed for high current vehicle starting applications, it proves to be very versatile for many battery charging applications.

The only shortcoming found with the Bosch C3 charger is that the AC line fuse is internal and not field replaceable. Bosch might consider making the AC line fuse user replaceable in later production runs of this product.

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I'm very pleased with this Bosch C3 Battery Charger, it's not your basic car battery charger because it's a "Smart Charger" it's computer controlled meaning it adjusts to the needs of the battery that's being charged. You do need to select the type of battery being charged, car, motorcycle or AGM but after that this charger takes control. If the charger senses a 12 volt battery is between 8 and 10.5 volts it automatically switches to pulse charging, this allows the battery to recover the best possible way enhancing the charging process for such a low condition. This is just one of the many computer controlled advantages of this type of battery charger.

I added the optional Bosch C35AC0 Quick Connect Cable Harness for C3 Battery Charger, it's a direct connect harness you can connect to your car or whatever battery that's installed. You simply plug the charger into the end of the harness, I have one in my sports car that's stored Winters, it makes it very simple to just leave the charger connected, once the battery is fully charged the Bosch C3 charger switches over to a trickle, when I want to use the car I just unplug the harness and drive away. I can't say enough about this great charger, buy one and you won't regret it!

Update: I found that chargers made by NOCO use the same plug and make many options for connecting to different application at a lower price. I'm guessing NOCO makes chargers for Bosch and use the same quick plugs. For the same price as Bosch's C35ACO quick connect harness the NOCO harness includes a battery monitor NOCO Genius GC015 12V Eyelet Battery Indicator