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Old 28-03-2017, 04:41   #16
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Join Date: Sep 2013
Location: Miami
Boat: 2012 Tartan 47
Posts: 206
Re: diesel Power generator or Solars+bigger alternator

If we didn't run A/C on the hot nights, I know I would not have our generator. We run two chart plotters, fridge, freezer and autopilot during the day and our two 195 watt solar panels almost keep us topped off. 30 minutes or so getting to our anchorage almost invariably gets us near 100%. We use LED cabin and anchor lights at night and sometimes even watch TV for an hour or two (NOT the satellite receiver) before retiring and, during the winter (tropics) never run the generator. The generator is noisy, fussy, expensive and uses a considerable amount of diesel in 8-10 hours of daily use.

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Old 29-03-2017, 21:47   #17
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Join Date: Mar 2017
Location: East Coast Australia
Boat: Schionning Wilderness 1620
Posts: 17
Re: diesel Power generator or Solars+bigger alternator

Freshman, as has been already stated you need to do some homework and calculate your current needs and also your planned needs. Add to this your safety margin and then total capacity (over say 3-4 days/0.6 (60%) of your needs to determine your total house-bank capacity. i.e. you should never run your Lead acid (of any kind) down below 60% (trouble starts at 80% for 'flooded types') AND they (house battery types) do not like high-current draws (i.e. the coffee maker; aircon etc) even if there is an inverter that will deliver it. Equally they (Lead acid) do not respond well if never fully re-charged. To this end it is my understanding you LA battery cannot (does not like) 'high current' charging in any case regardless of whether your new alternators can deliver it (will cook them - acid stratification or sulfation for proper terms - see good websites for how to look after your LA batteries). One reference which is I find helpful Absorbent Glass Mat (AGM) Battery Information - Battery University

Your investigation may therefore take you to new battery technology (i.e. Li) as this does accept high charge rates (and reduces weight for same VA.

Based on our needs (incl contingency) we installed a water-cooled 4.5 kVA generator. This is a Northern Lights unit which at the time (five months ago) was the 'smallest' capacity generator that ran at 1,500 RPM to make it 'tolerably' silent (water cooled) - we do not actually need 4.5 kVA. We use this for 240 AC supply for tools, coffee maker, microwave, (all high current devices). We have 1 kW solar (latest generation so optimal production for low solar angle and partial panel shading issues); and even after several days of rain or poor solar radiation we have not needed the generator solely for charging the batteries. We motor sail reasonably regularly or when repositioning - regularly not less than weekly and with 60 AH alternators on each engine and cannot 'use' all their output in any case; we rarely visit marina's (shore power) so solar is needed 'every day' to take the LA batteries (AGM type) back up to full power (i.e. 'float' for hours is needed). Our NL generator only uses just over 1.2 l/hour when running (1.9l/hr full load = 4.5 kVA is never achieved even when we heat our 60 litres hot-water to make the most of the generator capacity as the 'element' is limit to 750 watts so that shore power (220 V / 15A) regulated) is not exceeded assuming that other 'loads' will be present together with the water heater when connecting to shore power. Again this is only practically whenever the real-coffee caffeine-low light comes on (say every 3rd day) or we are hosting guests with increased water (fresh water generator) shower usage; lights, equipment recharging etc; cooking (microwave, cake mixer; more frequent fridge opening etc. is required. The 'cost' was not really justified given that we have two engines each with alternators but I did not want to run a 75 hp engine (much higher fuel consumption and absolutely hates being idled for hours without 'real' load) to generate power. Also got rid of our 2KVA (= 8-9 amps) portable unit as this was unable to run power tools (e.g. portable grinder, coffee maker, aircon etc. and with it sitting out on the rear deck it was noisy (all the time) and in the rain (when often needed to recharge batteries before new solar) it was downright dangerous.

Hope this helps.

Live aboard Schionning Wilderness 1620 cat s.v. THOR
Mike & Åse
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alternator, diesel, generator, solar

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