
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.

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.
Buy Bosch C3 Fully Automatic 4-Mode 6/12V Smart Battery Charger and Maintainer (3.8 Amps) Now
As inteligent as this units charging features are there is a basic flaw in its logic when it comes to being a battery maintainer. You need to push a button before it will do anything! So, if you have you battery being maintained and the power is interupted for a split second, it will just sit there and do nothing until you notice and push the button again. Just imagine coming out to your garage to start your lawn tractor after a long winter to find your battery dead because the power flikered one evening during the winter.
Pretty dumb design for a smart maintainer.
If you want it for a charger, it is VERY well built as you would expect from Bosch.
Read Best Reviews of Bosch C3 Fully Automatic 4-Mode 6/12V Smart Battery Charger and Maintainer (3.8 Amps) Here
I bought this because of the built-in desulfator feature. The issue is it does not allow you to enable the feature manually. I'm pretty sure my SLA battery needs to be reconditioned since the charge does not last long. But this charge never goes into desulfator mode.
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I would have liked a meter on it but other than that this is a very good, easy to use battery charger that is as close to fool proof as you can get. Bosch makes high quality products and the price through Amazon was very good.
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