20hp Electrical Output

[fishguy]

This one's likely a no-brainer, but I'm still collecting my boating brains.<br /><br />1975 Evinrude 20hp. <br />Mod# 205B62B<br />Ser# C96083<br />I tried out the generator and found that it's working. Hooked up a couple single filament auto bulbs as a test. <br /><br />The manual specs the output as AC power at "45 watt at 12 volts"<br /><br />So I guess I can run my white light and my bow light, and that's about it. I was thinking of putting in a small battery (along the lines of an ATV or lawn tractor battery) to power the lights when I'm fishing late in the evening. But, having 12v AC, I can't charge the battery off the generator. Or can I ?<br /><br />If I convert AC to DC with a rectifier I'll end up with 6 volts, won't I?<br /><br />And can I use regular automotive bulbs? Will I be replacing them every time I turn around because of powering them with fluctuating AC voltages?<br /><br />Or, should I just hook the darn things up with an inline fuse and the pull switch and shut the heck up?

 

[Xcusme]

Re: 20hp Electrical Output

Well, ...lets see. 45 watts divided by 12 = 3.75 amps. Can you convert the A/C to D/C ?? Sure, use a rectifier. What will be it's output?? AC or DC? ...DC of course. Will the voltage drop to 6 VDC?? Nope, you'll still have 12 volts, only now it will be DC. Can you use regular automotive bulbs, sure, they're 12 VDC.<br /><br />"should I just hook the darn things up with an inline fuse and the pull switch and shut the heck up? " Sure, why not, no problem, but please, don't shut the heck up, we're here to help. Remember, the only dumb questions are the one's not asked.....<br />knowledge is power.....

 

[fishguy]

Re: 20hp Electrical Output

Okay.. So with a 'rated' output of 45 watts at 12vAC, I can add a rectifier and end up with 12vDC at..what?<br />Sorry...I know there's a 3-sided doohickey formula that I learned way back when....Amps = Volts/Resistance...or something.<br /><br />And when I go to (Radio Shack, I presume) what do I ask for? Any special rating?<br /><br />Sorry..I usually try to figure things out with a little help, but in this case, I'm asking someone to figure it out for me and just give me the answer. hehe<br /><br />Thanks in advance (again) <br /><br />As far as the battery goes...I'm thinking pretty small....smomobile battery, lawn tractor maybe....<br />All it would power would be the red/grn bow light and the white stern light after dark, and maybe a cig lighter socket for the cell phone or something...no starter or anything like that.<br /><br />I just don't feel like dragging the battery into the shed to charge it every time, or dragging the charger out into the driveway...I like being self contained.

 

[Paul Moir]

Re: 20hp Electrical Output

The other formula you want is watts=volts x amps. <br />Yup, rectify and you get your 12v. I know it sounds painfully simple. <br />Get any "bridge rectifier" rated at more than 6 amps. Actually get the 35 amp one. I know it's way overrated, but it comes with large lugs you can attach to, plus a bolt hole for easy mounting. It's like $2.99. Forget about the voltage (PIV) rating - it really doesn't apply to you.<br />Connect the leads your getting the 12v from now to the ~ leads (either or). You get your DC off the + and - leads. You'll probably want to wire the - one to the engine block...<br />If you have a Pricess Auto nearby, they have these great 46AH batteries in the surplus section. They're deep cycle, but they can drop 600amps, so you can crank an outboard on them no problem. They're a little light duty, but they're AGM, so if they get dropped and cracked, they don't leak acid everywhere. $59.99 or something.

 

[fishguy]

Re: 20hp Electrical Output

Thanks Paul!!! Super information.<br /><br />I think I'll still go with a very small battery....like I said, I have no electric start on the motor..it would just be to run the 2 lightbulbs (bow and stern) and a cig lighter....might get fancy and put a little radio and a couple small speakers up under the dash..<br />Okay, don't give me ideas..hehe<br />It's a 14' boat with a 20 on it, so I'm underpowered as it is...better not add extra weight I don't really need.<br /><br />Thanks again!!<br /><br />p.s. Tarped up the boat today and put it away for the winter. Now comes the long winter of watching Boats And Places on TV....aghhhh...is it spring yet?

 

[Paul Moir]

Re: 20hp Electrical Output

Oh - I missed the part about it being a pull start. I'd do the same and use a really small battery in that case too. <br />Your running lights probably draw about 2.5Amps, which would be useful for figuring out your battery capacity. If your using a starting battery you may find this useful:<br /><br />RC = Reserve Capacity (minutes)<br />AH = Amp x Hours. A 20AH battery can supply 2Amps for 10 hours.<br />AH = RC / 2.4. <br /><br />eg. A 80 Minute RC battery has a 33.3AH capacity. <br /><br />Draining a lead acid battery past 50% damages them. This applies to a deep cycle battery too (they're just better able to take the abuse.) <br />I've actually put a cig lighter on my brother's boat. Bic's on sailboats are awful..<br /><br />Weather here is nice today. Actually anything would be fine with me... We're still a little shell-shocked down here as far as weather goes.