Energy Unlimited by Victron

8.4. New: the hybrid or battery assisted AC concept, or “achieving the impossible” with PowerAssist

8.4.1.

PowerAssist The next level in generator and shore power support is to actually help the generator or shore supply when otherwise an overload would occur. This is what the Phoenix MultiPlus does with PowerAssist . Continuing our example of section 8.3.3., one may want to run a 2 kW air conditioning compressor and at the same time do the washing, bringing the peak power to 4 kW. Or to heat water in a hot water kettle (2 kW), or simply make coffee (1 kW), or use an electric stove (6 kW) instead of gas. With the MultiPlus this is all feasible. When the AC power required increases beyond a pre-set limit, the Multi will stop charging the battery and operate as an inverter in parallel with the generator or shore power. In our example the generator would be boosted from 3 kW to 3 + 2.5 = 7.5 kW. As will be shown in the next chapters, the saving in weight and fuel consumption of the electric power supply system can be substantial.

The MultiPlus solves the problem of insufficient shore or generator power by adding additional power taken from the battery.

8.4.2. Other advantages when operating Multi’s together with a generator

In the previous sections we explained the advantages of PowerControl and PowerAssist : the possibility to use a smaller generator, or to reduce generator running hours, to increase the AC load, or to boost shore power.

Other advantages are:

Uninterrupted AC power AC power will always be available, either from the Multi’s, or from the generator or shore power. A digital clock or the settings of a video recorder will not be reset every time that the generator is stopped. Immediate availability of AC power When installing sufficient Multi power any AC appliance on board can be switched on without the need to start the generator first. Redundancy When several Multi’s are operating in parallel, a faulty unit (although unlikely that this would happen) can be isolated from the healthy ones. There is a second AC redundancy because of the presence of the Multi’s and a generator. And finally there are at least 2 sources of DC power to recharge the battery: one or more Multi’s and the alternator on the main engine.

8.4.3. Shore power

We have seen that one way to cope with insufficient shore power is the MultiPlus: with PowerAssist shore power can be boosted to up to 4 times its nominal rating.

An alternative is to use the DC concept for shore power. In other words: use a battery charger to convert shore power to DC and convert DC back to AC with the inverters or Multi’s which are on board anyway. The house battery will supply additional energy when a lot of power is required on board, and will be recharged by the battery charger during periods of low power demand.

For more details, see sect. 8.5.3.