Adaptive Charging

Judy’s last post exposed my ineptitude in electrical design, I am now obliged to reply to good questions posted in comment.

I was asked:
“…why does the AC battery charger only charge the starter batteries?
Or does the Quattro do this for the house batteries? If it does, why is the separate charger necessary?”

Thanks for selecting the electrical matter of most concern to me.

A big electrical problem most people seem to have with small ships is a mismatch between the requirements of a deep cycle house bank and a that of a starting bank with completely opposite discharge usage and charging requirements. This mismatch which causes early battery failure, becomes a problem if one assumes, as most operators do, that a separate start bank is a basic safety requirement.

As a lot of people before me have discovered, the very simple design of most alternator charge systems originates from the automotive world and is not at all intelligent enough to handle the disparate charging problem outlined above.

The simplest approach used by many is a “spill-over system” to charge one of the banks until it reaches a good state of charge, and then use a combiner or simply a manual switch to start charging the other. The usual end result is either a start bank overcharged to death or a house bank undercharged to death.

There are a number of charging solutions manufactured that are bolt-ons to the the spill-over system. Most approaches are piecemeal and therefore when all aspects are addressed become massively complex. Some of are quite excellent in the attempt to achieve an accurate charge for both banks by using DC to DC charging technology. However, the lingering concern I have with all these systems is fragility, in that the installations demand a location that is dry, cool and very close to the engine. This is major problem as our boat has two engines that are located aft in each hull in their own compartments which in our climate are hot and very humid. To exacerbate this, the engines are approximately 7 metres apart and also 7 metres diagonally from the house bank, therefore the size and layout of our boat works against minimising large amperage cable runs.

I decided that with the following I could achieve everything required to address these problems:

• isolate the house bank and start bank completely from each other’s loads, which for the start bank is only engine start and possibly an emergency circuit for communications
• maintain a four stage adaptive charging program (See here how adaptive charging works) for each battery bank by having:
• all generation current AC and DC managed by the integrated Victron components and then using that combined substantial resource to allow:
• the Quattro to complete the charge requirements of house-bank and
• the Phoenix dedicated intelligent charger to manage the start-bank

Unfortunately although the Quattro is a very capable state of the art system, the starter battery output is only a 4 amp trickle. If Victron Energy included a four stage, second starter output of say 15-20amp, I would have reduced redundancy which as one can see is a feature on our system.

The information provided by the Blue Power Panel would cover all the charging/discharging functions of both banks if I included an additional battery controller. However I have chosen a separate battery monitor for the start bank. which saves cost and provides the information independently of the Blue Power Panel.