BobJ and Sandy,
Thanks for the reference. This is a very useful thing for all cruising boats to do.
I took a quick look at five of them (Alchera, Chesapeake, Dream Chaser, Nana, and Ragtime).
Some very useful data there. However, I did note a couple of things which seem off:
1. refrigeration consumption was very low
, compared to installations I know about; not many boats are going to get by with 20-30AH total draw per 24 hours;
2. computer consumption was way low
, at least for laptops. They certainly draw more than the 16-25 watts shown....many draw 6-7 amps; maybe they're talking about dedicated chartplotters?
3. SSB transmit draw was often shown as near the maximum
; while this could happen with data transmission
voice is way less...more like 40-60% of maximum draw average.
4. some didn't seem complete
, i.e., they must have had some of the equipment
onboard for which no data were shown. Of course, as you said, these are racing
boats, or at least boats participating in a race
5. the recommended battery size
apparently results from a simple multiplication factor, and doesn't take account of the boat's size, things missed in the listing, etc. Some of these seem way off, e.g., the recommended battery size of about 100AH (for the boat which showed an incredibly low 73AH/day consumption rate). I wouldn't set off for Hawaii
in ANY boat with only 100AH of house battery power aboard :-)
6. the charge times
are, as the spreadsheet says, based on 100% alternator
output. This only happens for the first few minutes. After the alternator
warms up, it's output will be reduced. Might have been better to build in a compensating factor, like 75% of alternator output.
Some of these boats were no doubt fitted with energy monitors, like the Link series. I'd be interested to know how closely the results on paper came to the "actuals" as measured by the monitors.
All-in-all, a very useful exercise, though.