Electricity

I have just finished installing my Sterling Alternator to Battery Charger and my Sterling Power Management Panel.

The Alternator to Battery charger (A2B) is a clever device that tricks the alternator into producing more output in order to charge the batteries faster. It does this without any modifications to the alternator. And you can connect two alternators to it provided their total output is less than the max for the A2B.

The Power Management Panel (PMP) is a device that measures voltage and current and can calculate the number of amp-hours drawn from your battery. (These are pics from Sterling's website - the PMP is much smaller than the A2B).



A few months ago I installed a Sterling pure sine wave inverter-charger to keep my batteries topped up while I am connected to the marina shower power. The inverter-charger works very effectively as an uninterruptible power supply as it automatically starts generating 230v ac from the batteries if the shore power fails. I proved that it works by accidentally overloading the shore power which then tripped off. However I did not notice until the inverter started beeping because it was overloaded. The 2.5kW inverter continued providing over 3kW until I switched off one of my electric appliances. I presume it would eventually have shut down.

The purpose of all this electrical equipment is so I can enjoy 230v ac when I am not attached to shore power. To test my new installation I switched off the shore-power and turned on a fan heater. With the boat engine running it was comfortably able to provide 1kW and spare amps to continue charging the battery. As 1kW is 83 amps at 12v (and more when you allow for inverter inefficiency) it was clear that both 70 amp alternators were contributing. When I turned the heater up to 2kW the alternators could not cope and there was about 75 amp drawn from the batteries. However at that rate I should have enough battery capacity for about 2 hours usage, and I can't imagine wanting as much as 2kW for more than a few minutes a any time. (Needless to say I have no intention of driving the fan heater from the inverter - it was just used for test purposes.)

My main 230v demand will be a microwave, fridge and washing machine. I bought a regular 230v fridge/freezer rather than pay the exorbitant price for a 12v fridge.

I have installed the A2B so that I can re-wire the system back to its original state easily. I must write down how to do it while I still remember!

I also installed the inverter charger so that I can connect the shore power through the inverter-charger (the normal day-to-day situation) but I can also connect the shore power straight into the domestic 230v circuit.

I intend to put some sort of indicator in the saloon/kitchen area so I can easily see whether the shore power is working - so that I don't inadvertently use battery power.

It's in the back of my mind to have a mains socket in the boat that draws directly from the shore-power and never from the inverter. It would be useful, for example, to avoid accidentally heating water with battery power.