I've already reduced my home usage of electricity to 1kw per day . . . sometimes considerably less. Uh, sure, but given you're drawing the energy from the battery either way, it distracts to talk about the battery inefficiency. In your nom. 1kw example (80a, 12v), if you truly needed 960watts of auxiliary power, an 80% efficient inverter would require 100amps from the 12v to deliver the same 960w to an AC load. If going to pure DC is easy, do it. If it's costly or difficult, work out an energy usage profile to see if it's worth it to go pure DC. In the above example, while there was a 240w theoretical savings in using pure DC over an inverter to same 960w load, it may be that 960w is 4x what you'd really need for max aux power. So maybe only a 60w difference in savings between DC vs AC. Further, an 80% efficient inverter isn't such a good inverter these days and instead of losing 20%, a 12% loss would be reasonably attained. Finally, there are other measures which can reduce the load---as mentioned earlier, replace some of your lighting with DC LED lighting and now those loads are moved off the AC end. That's your best strategy---explore which loads are easy to move to DC, do an energy balance and find out what inverter options are available to meet the rest. -mt From: electricboats@ I'm not an electronic mathematical genius, so bear with my thinking. On Tue, Mar 30, 2010 at 7:37 AM, Steve Dolan <sdolan@scannersllc. George, I believe most converters/ Inverters are about 80% to 90% efficient. My Sensata is rated at 88%. Steve in Solomons MD From: electricboats@ What do you want to know? There are inverters available in many regular retail outlets that will convert 12VDC to 120VAC, ranging from 150 to 500 watts. Sine wave AC output is better for electronics. Anything else?
I'm ready to say goodby to AC current and looking forward to boat living at the equivalent of about 0.3-0.4 kw per day MAXIMUM.
7" TV
3" MP3 player for videos and music
12 volt cooler which almost NEVER get's opened(I really have to think about this one)
LED lights for overall lights(including navigation) and LED "spot" lights for individual needs.
Lots of batteries with the idea that no battery will hardly ever see 20% discharge
about 160+ watts of solar capability
and a small windmill to make use of nighttime breezes to boot.
a manual washing machine(hand-
propane and alcohol stoves
large frenzel-lense(
well-made, self-designed wind-scoop
well-made, self-designed, well-fitting and quickly set-up rain cover sort of type bimini
basically, a reduction of electric needs to the point where almost any type of recharging system would be overkill for everything except the sometimes needed electronic propulsion system. After all, it IS A SAILBOAT.
I'm 2 years to retirement and already 2 years past-due.
John Francis
Pearson 26(soon to be a Pearson 30)
Port Clinton, Ohio
Sent: Tuesday, March 30, 2010 6:17 AM
Keep in mind if that 80%-90% only refers to the 60%-70% of the power your battery has to offer(before you discharge too low), that the loss(of the usable battery power) is actually very substantial.
80%(inverter) of 20%(usable flooded battery). I would guess that means that 400 rated "usable" amps(printed on the battery), would result in 64 or so truly usable amps instead of the 80 amps you'd expect to use without the inverter which could be critical to the intended usage.
I guess what I'm saying is that unless there's a real worthwhile advantage to run off of AC, why not run off the DC(and save that extra money for a few more batteries at that)?
I say batteries, batteries and more batteries, to the point that no one battery should ever be expected to be taxed too much . . . but that's just my un-educated thinking.
John Francis
Pearson 26
Port Clinton, Ohio
Sent: Tuesday, March 30, 2010 7:22 AM
To: electricboats@
Subject: Re: [Electric Boats] Re: converter
Hi Eric
How much power is lost due to the conversion. Is it appreciable or negligible?
For example, if I had the choice between running a certain item off of DC or off
of AC , would my battery bank last a lot longer off DC?
Thanks George- - - - - -Read my sailboat building blog at: http://buildingmysa Happiness is a tall boat and a breeze to sail her byGeorge F Farrell, Jr.
Eric wrote:
Fair winds,
Eric
--- In electricboats@
>
> somebody tell me about low voltage DC to high voltage AC conversion.
>
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