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Customer Review

27 of 33 people found the following review helpful
1.0 out of 5 stars Serious flaw in the Bosch C3 "smart" charger, February 15, 2013
This review is from: Bosch C3 Fully Automatic 4-Mode 6/12V Smart Battery Charger and Maintainer (3.8 Amps) (Automotive)
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.
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Showing 1-10 of 12 posts in this discussion
Initial post: Feb 28, 2013 10:51:06 PM PST
MGS says:
It's a serious flaw with some people thinking.......this charger is for batteries which are still functioning and slowly losing their charging levels Volts/Amps...If your 12 battery is discharged to a voltage less than 6 V's GARBAGE...or you are the one collecting old ones, try to recharge them and sell them as new....??? How old is that 12V battery with only 6v available ...maybe 20 years...

This is the rule which can be applied to all batteries ( basic in electronic Universities):

-A 12 V battery ( any kind, could be AGM, Gell, etc) with a voltage of 11.5 or less, has a state of charge 0%. 50% of the batteries with this state, will dye completely in max one year (based on the manufacturer). In order to have 100% charge a battery must read min 12.80+ voltage

In reply to an earlier post on Mar 1, 2013 12:36:17 PM PST
Last edited by the author on Mar 1, 2013 12:42:25 PM PST
Darby says:
Well, the battery is now 3 1/2 years old, was 2 1/2 years old when it discharged essentially completely becasue we left the light light on for 3 weeks while we were off on vacation. Before charging it registered 3.5V, it then charged to 6V with the Bosch C3 charger, and then to 12V with the second charger, and has worked ever since, over a year now. I'm certainly no electronics specialist, bit it did recharge back to 12V and is still working fine over a year later. And that's good enough for me.

And no, I have never sold a battery to anybody. When they finally die I recycle them.

Posted on Jun 14, 2013 6:41:21 AM PDT
Loren says:

Darby makes a very good point about the "smart" charger not being able to recognize that it's attached to a 12 volt battery. If you don't already own another charger, you will be forced to buy one, as he did, in order to get this charger to finish the job. I have experienced this same problem with my Vector smart charger as well.

To attack a reviewer because he isn't an electrical engineer just makes you look foolish. His point is valid.

I'm sure that if Darby wanted to learn the latest discoveries in battery chemistry and technology he would do so. Even if he knew all about it, that still does not detract from the fact that this charger will not bring a badly discharged battery back from the dead.

I agree that allowing a lead-acid battery to discharge to well below 6 volts has probably cut its life dramatically, but it's still true that this charger won't bring that battery back.

For what it's worth, I did almost the same thing that Darby did with a pair of Optima AGM batteries that were installed in my diesel pickup. After about a week with the dome light on they were both dead. (I was very surprised that such a small light could discharge two batteries in such a short time.) I recharged them with a good charger and they are still working. I think that was about 8-10 years ago. They do get good maintenance, with a good (smart) charger, especially during our Indiana winters. I suspect that if Darby has a quality battery this single deep discharge may not be the catastrophic event that you think it is, especially if he uses this charger often.

He reported on a situation that many may have overlooked and certainly should not be belittled for doing so.

You're out of line.

- Loren

Posted on Jun 14, 2013 2:27:18 PM PDT
Philly says:
[Customers don't think this post adds to the discussion. Show post anyway. Show all unhelpful posts.]

In reply to an earlier post on Jun 14, 2013 2:29:20 PM PDT
MGS please note that a otherwise well maintained quality batterie that has been discharged to basically 0 volt is by no means garbage. With a good charger it can be brought back to life and used for many years. I agree that Bosch has not considered this possibility with their chargers. It can be done relatively easy in reprogramming the software and I am sure that Bosch will do that with later production.

In reply to an earlier post on Jun 14, 2013 2:29:46 PM PDT
Philly says:
[Customers don't think this post adds to the discussion. Show post anyway. Show all unhelpful posts.]

In reply to an earlier post on Jun 14, 2013 2:30:11 PM PDT
Last edited by the author on Jun 14, 2013 2:33:42 PM PDT
J. Phillips you are wrong. A maintained quality batterie can be discharged to 0 volt and brought back to "normal life" again. A dead/ damaged cell is a totally different issue and can't be fixed no matter what charger you use.

In reply to an earlier post on Jun 14, 2013 3:18:17 PM PDT
C. Plunkett says:
A battery that isn't beyond hope will not register 0 volts on it unless there is a load dragging it down. If you leave the battery in your car with the cables attached to it when you measure this, there is still a load on it that can take the remaining amps off the battery and essentially give you a false reading.

With no load pulling the voltage down, anything under 11 volts or so means there's a bad cell, and it's no longer any good. But even with a healthy battery, turn on the wipers, horn, lights and hit the starter, you might be able to get the voltage this low on something that can still start your car.

In reply to an earlier post on Jun 14, 2013 8:16:20 PM PDT
Darby says:
Well, Darby here again. That same battery which was down to 3.5V after having left the lights on for weeks and which the Bosch charger brought back to only 6V and which the second charger brought back to 12 V: it is still working, now nearly 2 years since the heavy discharge. Still starts the car, still charges normally, still runs lights and radio, etc. And that's good enough for me. The Bosch charger would have left it "dead" at only 6V. The proof is in the pudding guys. I'll let you all know when it finally dies.

Posted on Jun 15, 2013 5:50:51 AM PDT
Last edited by the author on Jun 15, 2013 5:52:38 AM PDT
Loren says:

I suggest that you still use your Bosch C3 charger on that battery occasionally. Bosch claims that the C3 will desulfate the battery. Sulfation occurs to a greater extent if a battery is deeply discharged or allowed to remain in a discharged state for an extended time. Check Wikipedia for an explanation; search for "lead-acid battery".

I have a BatteryMinder (BatteryMINDer Model 12117: 12 Volt 1.33 Amp (12V 1.33A) Charger/Maintainer/Desulfator) that also will desulfate a battery. I use it occasionally on all my batteries and get very long life from them. My first Optima batteries, purchased over 10 years ago are just now starting to show a drop in power.

I forgot to mention it in my earlier comment, but I think you were too harsh on Bosch with a one-star rating for the problem you had. Once consumers are aware of the problem we can use another, really cheap, stupid battery charger to bring the battery to some voltage above 6, then use the Bosch for the final charge. I have had exactly the same problem you mentioned with my expensive Vector smart charger. It seems the smart chargers have trouble with really dead batteries. One of the advantages to a smart charger is that a good smart charger will actually top off the battery. Many other chargers never really get the last 10% into the battery.

Thanks for your comment, though. You certainly have a valid point.

- Loren
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