How many Amps do you use?

[ajgoldman]

When I have every gadget going on my boat (5 ST60s, chartplotter, radar, laptop, stereo, running lights, fridge, autopilot) I can pull a healthy 18 amps per hour. Way too much for running on an open ocean. But I do like my stereo, I do like having the ST60's running, cold beer is good, being seen at night is good (also a requirement)....

So, my question is this: I am budgeting for about 180 amps a day, minus about 80 amps I will get back from my solar panels (8 amps with about 10 hours of good daylight, oh yea, no clouds to Hawaii right?). This leaves me with about 100 amps a day I need to put back into my bank via engine and/or generator.

How do these numbers seem to those SHTP vets out there?

Thanks,

AJ

 

[Culebra]

Wow AJ, that's a lot of electrons. Leave some for the rest of us, would you? Kidding, of course... 7.5 amps average consumption sounds pretty impressive (meaning low) for all that gear.

I'm hoping to consume about 2/3 of your number (5 amps on average) if I'm conscientious and lucky, but then I won't have cold beer! All lights are LEDs, AIS, no radar, x-5 autopilot, ST60 displays, no plotter, electron miser Garmin GPS portable (sends NMEA data to the other instruments and PC), PC has a lean chip and runs over 8 hrs on its own battery. For music, I thought Adam might play us a song over the SSB. More likely I'll have the siren song of the islands or voices in my head. SSB on board, but used only for voice/check-in, no data. Sat phone for data once or twice a day. House capacity is 300 amp-hr (excludes dedicated start battery), and I plan not to run the house down more than 40%--will run the engine to charge during check-ins (SSB will be happy).

I have enough capacity for 240 amp-hrs per day using my 40% rule (and 2 check-in charges), but I hope to use 1/2 that. If I find I'm consuming too much, I'll engage the Monitor vane or take the helm and sail by compass and windex, sans instruments now and then... actually that sounds like fun... maybe I'll pull out the sextant (doubtful... I'd end up in New Zealand). It'll be a learning experience for me, for sure.

Paul

 

[robtryon]

Amp hours

On Feolena, I had about 400 amp hours available, 100 watt solar panel that would contribute a couple amps even on an overcast day and six amps with bright sun, an AirX wind gen which was the hero of the trip there and back. I ran a laptop, AIS, SSB,a very loud stereo system w/big amp & subwoofers, incandescent masthead light and interior lights. I'd say my average 24 hours use was 150 amp hours, but no refer.

So, AJ, 180 amp hours sounds about right, if you're going to run that stuff 24 hours. I only ran the engine the first two nights because we had no wind and it was overcast. I ran it again about 10 days into the race when I was caught w/no wind again. For me, the wind gen, put back everything I used. In fact, once the trades really filled in, and I was running for two weeks, it was like being plugged in at the dock. My batts were always full, even w/the laptop on most of the day and the stereo running 24/7.

Last race, we had to do an electricity budget worksheet. I think you can still find it on the '08 website. For me, the sheet was pretty much fantasy, but it did give me a good idea of what my usage was. I really like Paul's idea of running the engine while transmitting. That should help.

 

[BobJ]

Link to Electrical Budgets

Here's the link.

Some of the 2008 worksheets aren't filled out or aren't realistic, which is mostly why we dropped the requirement for this year's race. Nonetheless it is critical to analyze your planned electrical usage. Your autopilot and communications (among other things) rely on charged batteries.

Take a look at my budget - I measured all the draws and tried to get Ragtime's numbers close to reality. I budgeted 78 Ah/day, less 35 Ah from the solar panels, for a net usage of 43 Ah/day. This indicated a need to charge the batteries (via alternator) 90 minutes every 24 hours. My actual usage during the race was less than my budget, I got back less from the panels due to lots of overcast, and overall didn't have to run the engine/alternator as much as I projected.

The biggest error in these spreadsheets is probably the alternator output, which drops off significantly after the first few minutes of charging. Mine is a 35 Amp alternator (with an external Balmar ARS-5 regulator). Even when the batteries were 50% discharged the alternator would only show 25-27 amps output, and after the batteries took the initial bulk charge the output would drop to half that or even less. This directly affects your charging time and fuel requirements.