Unlike the lithium battery in your phone, the lead-acid battery in your car likes to be constantly kept at a full charge. Both lithium and lead-acid batteries however don't like to be fully discharged (otherwise known as deep-cycled in lead-acid batteries).

Modern car electronics and alarm systems however puts a high demand on batteries even when the car is switched off and can sometimes drain the battery in a matter of days when you're not driving the car. This can be a problem if you have vehicles that you don't use often enough to keep the batteries charged or if your job requires you to constantly be away.

Rather than constantly starting and idling fuel away just to charge the battery, the easiest and safest option is to purchase a smart charger and keep your batteries hooked up to it when it's not being used.

A charger is a charger, right?

In a world of battery chargers, you have the basic battery chargers that just pumps in both voltage and amps until it's full (and requires that you manually disconnect it) and the more expensive plug-and-forget smart maintenance chargers - The Bosch C3 falls somewhere in the middle of these two worlds.

The C3 allows you to set the voltage and amp for various battery types and automates everything from that point onwards until the battery is full. Once the battery is full, the C3 then automatically switches to a trickle charging to keep the battery fully charged without being overcharged.

Compared to the basic chargers, most basic charger only allows you to charge 12 volt batteries at a set 0.8 amp output and requires that you manually disconnect the battery once it's full - failure to do so can actually overcharge and damage your battery.

A smart maintenance charger however automates everything from detecting the type of battery to its amp-hour rating (i.e., the size of the battery) and even has a testing, desulphate/reconditioning and trickle-charge mode. In short, it's literally just plug-and-forget.

Multiple charging modes.

The C3 has a user-selectable 6V 0.8A, 12V 0.8A, 12V 3.8A and a 12V 3.8A (that outputs 14.7V max for AGM batteries) mode (Mode 1 to Mode 4) all via a manual select button and LED indicators. 

After you set the initial mode select for the battery voltage and amp, the C3's charging is fully-automated with microprocessor-controlled pulse charging and trickle charging capabilities. Once the battery reaches a full charge, the C3 then switches to its trickle charging mode that monitors and maintains the battery at a fully-charged state with no risk of overcharging.

You can leave the C3 hooked up directly to your bike or car battery, while still being in the vehicle, for months on end, come home, disconnect the charger, start the vehicle and ride or drive away.

The plus points.

The plus side with the C3 is that if you happen to have classic vehicles with 6V charging systems - like classic British motorcycles or even the first generation Honda C70, you can just as easily hook up the battery to the C3 and keep it trickled charged. Ready to ride at your convenience.

The C3 works particularly well on 12V sealed/maintenance-free lead-acid batteries (which is as common in modern vehicles sold locally as are normal lead-acid batteries - the type which you have to top up the electrolytes with distilled water) as well as the less common Absorbent Glass Mat (AGM) also known as spill-proof batteries and probably only used in motorsports or serious off-roading vehicles.

And since it has a manual select button, you can also crank up the amps by using the 12V 3.8A 'car mode' instead of the 'motorcycle mode' to quickly bring a discharged motorcycle battery to a full charge within minutes instead of hours if you find yourself with a flat battery come Sunday morning ride.

..and the not-so-good news.

Unfortunately, these 'basic' settings on the C3 also require you to know what type of battery you have in your car or motorcycle and some basic understanding of how lead-acid batteries work. If all you did was hook it up the battery and turn on the power mains, the C3 would just sit there and stare back at you.

In contrast, when pitched against the more advanced (read: more expensive) smart maintenance chargers, the C3 falls short of automatically determining what type of battery and at what voltage and amps that is safe to pump in to that battery.

No desulphate/regeneration mode.

The C3 also lacks a 'desulphate mode' which is useful to recover deeply discharged or refresh sulphated batteries. This 'desulphate mode' is not to be confused with the C3's pulse mode which is enabled automatically for batteries from 8V to 10.5V to aid in charging a mildly discharged battery.

Some similarly-priced lower-end smart chargers do come with a 'desulphate mode' but lacks the C3's charging capabilities. Bosch however offers a "desulphate mode" which it calls 'regeneration mode' in its more expensive C7 charger.

Nitpickings, etc.

Since we're nitpicking, we also didn't like how Bosch decided to combine the alligator clips leads and the charging leads (which you attach semi-permanently on your battery) into one - you connect the eyelets to the alligator clips. 

Combining two leads is smart (and would probably save some coins in the manufacturing process), but if two major brands of smart chargers can include two separate leads we don't see why Bosch can't. Also, we're spoilt by the convenience of just leaving the leads attached to the car's battery and still being able to charge other batteries using the alligator clips on other maintenance chargers.

The wall socket is also a Europlug two-pin instead of a UK 3-pin and only runs off a 230V main. While this isn't a problem for the Malaysian market, we noted that one manufacturer included a UK-style plug (with a built-in 13A fuse) over their Europlug two-pin with their smart charger.

Bosch however did include a plastic hanger with the C3 which allows you to either hang the charger from the car's bonnet latch or mount the hanger against the wall in your garage instead of permanently installing the charger on the wall like most other chargers.

As for the 6V charging capabilities, in this day and age, there's few vehicles with a 6V charging system and most owners of old British bikes would've converted their 6V charging system to a 12V system so the 6V mode is questionable but remains a nice feature to have.

The C3, like most maintenance chargers is rated IP65 (dust and splashproof) which means it can be permanently installed in your garage and doesn't require babying like most indoor chargers.


For the price and its wide-range of charging flexibility, we'd rate the Bosch C3 a 3.5 out of 5 stars. If you don't have a smart charger and constantly find yourself with a dead/dying battery, then perhaps you should just consider getting a smart charger rather than constantly spend money on new batteries.

Batteries that are constantly on the 'plug' are known to last easily 2-5 times longer than those that are not, coupled with the assurance of having a vehicle that starts up when you want it to, then a smart charger would eventually pay for itself.

CT Hardware top-tip: If time wasn't an issue, the lowest amp setting is preferred over a high-amp charging. So assuming you're not going to use your car for the entire week, it's better to just leave the C3 charger in the motorcycle mode (12V 0.8A) instead of the car mode (12V 3.8A) to charge your car's 12V battery.

#Bosch #batterycharger #maintenancecharger #12Vcharger #C3 #carcharger #motorcyclecharger #cthardware #cthardwaretoptip