A typical alternator that most people might have a basic understanding of generates power that is used to recharge a vehicle's battery. Why that's correct in principle the reality is that when the voltages are only 13.3-13.8 volts as typically found after the first 5 minutes of starting a vehicle. This is why an alternator is only used to replace the energy used to start the vehicle in the first place. Many people may make short journeys to and from work and have already found how quickly their battery needs a replacement this is due to it not getting adequate charge.

Also if you revise charging voltages why are they important in our FAQ you see this isn't enough voltage to fast charge (or bulk charge) a vehicles battery. This problem is compounded if a secondary battery is attached.

Now for the Smart Alternator, it goes one step further and is controlled by the engine management system which controls when the turning of the alternator by the motor is applied. This additional load that is placed on the engine also consumes fuel, therefore, increasing emissions and that costs the manufacturer Carbon Credits so they now actively limit the time the alternator is on. Which means more flat batteries which is why we see the rise of EFB or AGM batteries as start batteries to try to counter the problem.

The engine management system knows how much power is drawn by every factory fitted item in the vehicle and therefore if you turn on lights, wipers and are using electric fans to cool the motor the vehicle knows to provide just the right amount of current the vehicle needs to operate with little wasted energy. Unfortunately, that previously wasted energy was actually absorbed by secondary battery banks needing a charge. These days this doesn't occur as much, in fact, with recent tests we have found a factory Iveco van only outputs a maximum of 22A above the engine management system requirements. That's typically the same amount of current required to run a DC powered fridge while driving. So your batteries aren't really getting any charge while driving from the alternator. Many vehicles now have smart alternators like Mercedes, VW, Fiat, Renault, Ford & more.

To try and combat this problem DC chargers draw their power from the start battery and by design try to flatten the start battery while the engine is running by feeding the secondary battery bank the correct voltage up to the max current of the charger. This in-turn causes the start battery to flatten which in-turn forces the alternator to come on and recharge the start battery While this is a very crude overview of the process the result is the alternator running for longer charging the secondary battery bank with the added benefit of being charged at the correct voltages for the secondary batteries which may be more than the output of the alternator. All in all that can lead to batteries being charged 30% quicker than the old alternator systems and est. 80% quicker than the new smart alternator setups.