I am sure you all already know this even thought I have not seen anybody mention it recently, ... but electric motors like for a drill, fridge compressor, etc, usually take 3 times the rated running wattage for starting. "Soft starters" are non existent in small device motors like fridges. I have seen them in well pumps, but not too much else. So a "500 watt" Microwave or fridge will take up to 1500 watts to start. This "surge" value is only about 60% accounted for in a typical genset, portable or otherwise. I am sure I well get a lot of flack over this comment, but that is what all the utilities expect in the homes you all live in. Living example: I built a "energy efficient" home that only ran on 120 VAC, some years ago. It was a 4500 SQ.FT home with all the toys including home theater, 3 computers, sound systems, fine fridge and a pair of deep freezes and central heat and A/C and more. We did some tests for the Idaho Energy Division. The "State" and local inspectors demanded we install a 240VAC, 200 Amp panel. With some delicate timing, we created a scenario where literally everything came on at the same second. That amounted to a total momentary draw of exactly 80 amps at 120 VAC for under 5 seconds, (9600 watts starting, and 3200 watts running). It took lots of legal efforts to force the local utility to accept the "100 amp service" to out 200 amp panel. In their internal documentation, they rated the home as a "10,000 Watt home."
The constant surging beyond the rated capacity of your system is the battery, controller, and genset cap. killer, and less the maintenance or other trivial losses I see folks commenting about.
That is my 2-bits worth.
Keep 'em purin,
Dan H.
Sent: Monday, June 12, 2017 10:46 AM
Subject: Re: [Electric Boats] Opinions
Look closely at the power requirements of the items you want to power:
fridge - maybe 500W
40lb trolling motor - 400W
To make a usable backup power system with a single 100W panel, you'd need a really big battery, pre-charged for a long time. Probably not useful.
On the other hand, with a 100AH deep cell or LFP battery, you could power your 40lb trolling motor for about 2 hours, then recharge over the next 2 or 3 days. I have such a system in my sailboat. Since I only sail on weekends, it meets my needs.
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Posted by: "Dan Hennis" <dhennis@centurytel.net>
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