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Thread: generator size?

  1. #1

    Default generator size?

    real quick question...
    How many watt generator do I need to run a 10 amp battery charger? how about a 20 amp charger? Im trying to find a way to keep my batteries topped off w/o access to shorepower. Any other ideas or tips appreciated. Thanks

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    Member dkwarthog's Avatar
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    I know that a 2000w honda Eu2000 is capable of providing 12 amps normally and a bit more under a surge condition.

    Just a rule of thumb, but watts divided by voltage equals amps. keep in mind that all or most generators are labled at their surge capacity not the normal operating capacity. So generally, a 2000 watt gen is really 1500 or so in real life....

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    Member Dan in Alaska's Avatar
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    P = IV

    In English, power (watts) is equal to current (amps) x voltage (volts). A 12V charger will draw about 120W at 10A; 240W at 20A.

    A 1kW generator will easily run the battery chargers you're talking about.



    Edited to add - the bat. chargers link is not mine. It popped in there automatically.
    Last edited by Dan in Alaska; 01-04-2012 at 10:29. Reason: the link is not mine

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    I use a solar panel battery tender , i have it bolted to the roof of my truck to keep the battery's up 5 watts if i remember right.I just plug it in to the power point inside the cab.Works great if you have good sun light or even on a over cast day it still puts out . Forgot to mention i have a power stroke ,i hate to keep the engine heater pluged in for long periods.So the solar panel works great,I've had installed for 3 years now with know problems .

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    Member patrickL's Avatar
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    Dan in Alaska is right. I use a 1000 watt honda to charge batteries all the time in the field. I even keep a little 400 watt, 2 stroke generator on my boat to charge up batteries in a pinch. Pretty slick little generator when you're short on space.

  6. #6

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    wow a 400 watt? that sounds great! I dont think I have ever seen one that small. What brand?
    Thanks for the help everyone!

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    Member patrickL's Avatar
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    Its a Honda 2-stroke. I was actually wrong, its a 350 watt. The model number is the EX350 if you want to google it. From what I can tell it hasn't been made in about 10 years but you can still find them around. I did see one on craigslist about a year ago. That's where I got mine and so far its been perfect for charging batteries on the water or even when I'm parked in a camp ground.

    The EU1000 generator Honda makes is also great but a bit bigger. Its a 4-stroke and I've used them for years day in and day out all summer long.

  8. #8

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    anyone try one of the solar battery chargers during winter in Southeast AK? Seems like a great option, but not sure how much light they require.

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    Member Cap'n Ron's Avatar
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    Fishfinder....I have no direct experience with solar panels, but my son and his friends have convinced me to get one for my cabin in PWS...according to them, cloudy days and even under shade of trees only reduce full capacity of solar panels about 10-25%...in other words, they are very efficient at low light levels. Now, I don't know how that translates to SHORT days, but I think that day length is more important than having full sunlight...and, if you are using a battery heavily, like keeping lighting on, that will cause a lot more drain that starting an engine a couple of times a day. I hope that helps!

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    Quote Originally Posted by fishfinder View Post
    wow a 400 watt? that sounds great! I dont think I have ever seen one that small. What brand?
    Thanks for the help everyone!
    fishfinder - I've got one of those Honda 400 watt generators collecting dust in my garage in Seward I can let go pretty cheap. I have a built in diesel generator in my boat so don't need it. PM me if interested.

  11. #11

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    Quote Originally Posted by patrickL View Post
    Dan in Alaska is right. I use a 1000 watt honda to charge batteries all the time in the field.
    ...yep, that there honda generator(wisper light?) will be the new addiion to the boat and camper this spring--tiny, light and quiet!!.....combined with my intelligent battery charger, i should be all set!...i have been using a noisy, heavy 1000 watt 2 stroke!!.....as a matter of fact, i am charging up all my batteries at the moment..my weeks project!!...2 for the litlle jet boat, 2 for the camper and 3 for the 'PEZ GORDO"!!....larry

    29' Wooldridge Pilot House, Twin 200 Hp Etecs! "...Pez Gordo..."
    18' Wooldridge Sport with 200 hp sport jet. "...Little Pez..."

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    Member dkwarthog's Avatar
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    Yup, I had brain flatulence when I posted. A 2000W honda can put out say 15 amps, but that is at 120V, not the output in DC to the battery.

    Just for kicks I measured the current coming in and out of my 1.5 amp trickle charger. At 2.0 amps on the 12v battery side, the incoming 120v amps were 0.3. In other words it takes 1/3 of an amp 120 VAC to create 2.0 amps 12VDC for that particular charger.

    I bought one of those "cheapy" 2 stroke generators from Shucks auto supply. That was an incredible waste of a hundred bucks. Recoil fell apart on the second pull, loud, stinky and burned fuel like a sled dog. Glad you guys found some out there that work good for you.

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    Member dkwarthog's Avatar
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    When it comes to general use...I see no reason to buy a 1000w honda. The 2k is as quiet, runs longer on a tank of fuel, and doesnt weigh hardly any more than the 1k.

    And you can run one heck of a lot of stuff on the 2k. Like a skill saw or a table saw.... and there is not much difference in the purchase price....


    heyyy!!!! the post I was responding to disappeared and left me hanging!! LOL

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    Couple of points, just because a charger/ generator said it will charger a battery at 8 amps does not mean your battery will be getting a 8 amp charge all the time. There are other factors that will limit the charge the battery gets.

    When you turn on an electric motor like a skill saw, table saw, or freezer it needs a surge current of several amps for a second, that most small generators can not handle.

    If you want to use a small generator to charge a battery or run a motor do your home work if you donít you may find you wasted a lot of money.

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    Fish Witch. I just sent you a PM. I may be interested if it runs and the price is right. Thanks

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    Quote Originally Posted by fishfinder View Post
    anyone try one of the solar battery chargers during winter in Southeast AK? Seems like a great option, but not sure how much light they require.
    Fishfinder, I think Samson was talking about a battery tender (low-amp trickle charger), rather than a battery charger (high-amp quick charger). Solar panels work okay under overcast skies but power output is proportional to the amount of light coming through, so expect far less than the "rated" output.

    Quote Originally Posted by Cap'n Ron View Post
    Fishfinder....I have no direct experience with solar panels, but my son and his friends have convinced me to get one for my cabin in PWS...according to them, cloudy days and even under shade of trees only reduce full capacity of solar panels about 10-25%...in other words, they are very efficient at low light levels. Now, I don't know how that translates to SHORT days, but I think that day length is more important than having full sunlight...and, if you are using a battery heavily, like keeping lighting on, that will cause a lot more drain that starting an engine a couple of times a day. I hope that helps!
    Cap'n Ron, you're half right and half not. Yes to cloudy days, but no to "even under shade of trees". Yes to only partial reduction, but those percentages sound too low. Yes they'll work in low light, but no to being "very efficient" without direct sun. (Solar panels are wonderful, but they're not efficient!) And the importance of day length vs. light intensity depends on your equipment and system design, since it's possible to optimize for either one.
    Inspiration is simply the momentary cessation of stupidity.

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    Fishfinder just got a flier in the mail Harbor Freight has 800/900max portable generator on sale for 129.99 regular 149.99 .For that price one can't go wrong,i know it's not a Honda . But you can even buy a extended warranty for a few bucks more . I have take stuff back to them and they replaced it no question asked and most of the small generators have a 12V plug to charge batterys direct from generator control panel .Just thought i would share info in flier. Have a good day!

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    Quote Originally Posted by samson View Post
    Fishfinder just got a flier in the mail Harbor Freight has 800/900max portable generator on sale for 129.99 regular 149.99 .For that price one can't go wrong,i know it's not a Honda . But you can even buy a extended warranty for a few bucks more . I have take stuff back to them and they replaced it no question asked and most of the small generators have a 12V plug to charge batterys direct from generator control panel .Just thought i would share info in flier. Have a good day!
    Yes, you can go wrong. Ten bucks says that thing is ungodly loud. If I was sharing an anchorage in PWS with someone running something like that I'd probably end up shooting it off the back of their boat.

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    Member patrickL's Avatar
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    Quote Originally Posted by samson View Post
    Fishfinder just got a flier in the mail Harbor Freight has 800/900max portable generator on sale for 129.99 regular 149.99 .For that price one can't go wrong,i know it's not a Honda . But you can even buy a extended warranty for a few bucks more . I have take stuff back to them and they replaced it no question asked and most of the small generators have a 12V plug to charge batterys direct from generator control panel .Just thought i would share info in flier. Have a good day!
    That's certainly a deal but I'd wonder about a generator that costs a fraction of the cost of the staple in the industry. I've bought a few cheap generators and they last a year or so and then I wish I'd bought a honda. I'm not a huge honda fan but they do make the best generators. Its like a chainsaw, I go with the staples, stihl or husqvarna, because the cheap ones you buy at the local hardware just don't last.

    One other important point, whatever you go with don't use the 12volt plug to that comes with the generator to charge batteries. It puts out a max amperage regardless of what the battery needs so a near charged or charged battery is going to boil. This will ruin just about any type of battery in a heartbeat and particularly an AGM or sealed battery. Trust me, I figured this out the hard way....twice .

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    Member pacific23's Avatar
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    We always plugged the Gen into the shore power receptacle so the onboard batt. charger could do it's job. We also hung the small Honda with bungy cords off of the bow rail so it didn't vibrate the deck . We ran the gen when on the hook while we cleaned fish , ate and partied . One tank would last until time to hit the rack , about 4 hours.

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