If I'm going to cook via electric, or use any electric 120/240 volt device via the batteries for that matter, than I'll need to use an inverter to draw the power from the batteries.
I found a calculation example:
3 amps x 120 VAC x 4 hours = 1440 watt-hours divided by 24 VDC battery environment equals 60 amp-hours.
So, for a proposed hot plate, that may draw 6 amps. Let's assume I have it on for 1/2 hour.
That's 6 amps x 120 VAC x 1/2 hour = 360 watt-hours divided by 12VDC battery equals 30 amp-hours....
I found a single burner hot plate at target for $20. It draws 800 watts. I'm assuming that means 800 watts divided by 12 VDC is about 67 amps per hour or about 33 amps in a half hour of cooking.
Why didn't I pay more attention to all this electrical stuff when I was in college!!!
Who would've known stuff in college could be useful ;p
I still have to double check, but I think my one deep cycle battery is rated at 75 Amp-hours.
I do have two batteries parallel-wired together, which means the amps of the two batteries are added together, if I have the battery switch on "both." I have a battery switch that enables me to use one, the other, or both.
So, let's say I have 150 amp-hours available... hmmm... perhaps I can use a hot plate...
Still... a 75 Ah battery can deliver (in theory) 1 amp for 75 hours, or can that be reversed? 75 amps in 1 hour? If so, then, if i'm looking at this correctly... cooking on a 6 amp hot plate for 1/2 hour just totally drained one of my batteries to "nominal charge." Which probably means I should recharge the batteries after every single hot plate cooking event! Hmmm... The deep cycle battery I have indicates it's capable of 350 cycles... I'm assuming that means discharge/recharge. I wonder if once I use the hot plate I'll probably have enough power left to start the engine to recharge the batteries (assuming I'm in a situation where I might not have solar power availability...)...
I did look at weights of larger amp batteries... upwards of one hundred and more pounds!!!
I don't think there's any way I'd be getting those on/off the boat, never mind in/out of the battery storage area down in the starboard locker!
I'm going to seek advice/council of the math genius in my office...
This power issue is making me crazy. How can I justify using up batteries... that may or may not end up getting recycled depending on what really happens when you drop off a battery somewhere... compared to the justification of an explosive non-renewable energy source of propane... I think I'm still leaning towards........ i don't know. head is spinning.
Other helpful info I found online...
12 Volt battery fully charged should read 12.7 volts on a volt meter.
12 Volt battery at "nominal voltage" or about 60% charge will read about 12.2 volts on a volt meter... not much change. definitely need the digital read out volt meter!
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And to make your head spin more check out the inverters. Look at which ones can give a continues rating for all that big wattage. And in the transfer from 12v to 120v there's a bit of a loss too.
What happens when your engine dies and you can't charge batteries your cold, misserable and really crave a hot meal. Or maybe you want to heat water to pour into the shower bag. Propane gets the job done every time. I have never seen a hot plate on any kind of cruising sailboat. But then again for docksiders it's good value.
I'm going to West Marine tonight to order my propane stove top ! but... which propane tank should I get... hmmm... decisions decisions !!!!
Am enjoying your journey towrds "Salty Dogdom"!
I knew a couple who lived aboard a 29.9 some years back in Pensacola.
They had tow six volt (golf cart) batteries installed under the quarter berth for house needs, along with a group 27 deep cycle for starting.
Its doable...
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