Cranking battery recharging

[FishinLogician]

I noticed the voltage level on my fish finder reads 12-13 volts when my 1985 50hp Mercury outboard is running (even at high RPM). Last weekend on the river at 2 am the motor failed to crank. Fortunately we had the trolling batteries on board to get it started. This is my first year with this boat but I remember earlier in the season I was seeing 15-18 volts read when the engine is running and have gone the whole season without having to charge the cranking battery.

We do run some accessories at night like a spot light, 55 watt headlights, fishfinder, 2 small internal incandecent bulbs and the nav lights. They are all on at the same time only when the motor is running and we're moving. When all but the fishfinder is turned off, the voltage reaches 12 but that's not a good sign as far as I'm concerned.

Should the normal running of the motor generate charging voltage?(12v or more) If so, what would cause the motor to stop generating the proper charging voltage?

[morpho]

on a car its 13.5-14v

thats spotlight lighst and headlights draw quite a bit of power i'm throw a charger on her give it and hour everytime you go out just like the trollers

[FishinLogician]

I'll do that from now on but are you aware if an outboard motor is supposed to charge it's battery(s). I've been told that it does and told it doesn't from different people. Does anyone know for sure? As I said it's a 1985. I don't know if that's important.

[This message has been edited by FishinLogician (edited 09-09-2004).]

[morpho]

afaik some do some don't valve would be a good guy to ask i'm sure he'll stop in here i just know that would be a pretty large load to put on an alt in a car

[FishinLogician]

It's about 1-3 volts by my measurements and as I said it's only while the motor is running. It's also only when we're out at night otherwise there is no more load than the fish finder which is minimal. Thanks mopho, hopefully valve will notice this string and comment.

[This message has been edited by FishinLogician (edited 09-09-2004).]

[This message has been edited by FishinLogician (edited 09-09-2004).]

[Valv]

Only newer motors with alternator have enough power to charge battery well.
Yours has to run approx at least 1500/2000rpms to have it charging, and even in that occasion the charge is not very fast since I believe it has only 6 watts output, or slightly more.
Small items like sonar, nav lights, a radio and interior lights will not draw a lot of power, but if you troll at idle a lot and use big portable lights plus other gadgets, your motor won't have anough power to charge battery.
Also try to clean contacts, it might help a little.

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Val Vignati

www.kvesurplus.com
[email protected]

[FishinLogician]

Thanks for clearing this up for me Valv,

I have one cranking battery and two for my trolling motor. I've decided to combine one of the trolling batteries with the cranking battery when I go out catfishing. This should allow for longer battery life as we do use the lights quite a bit at night. I take the trolling motor off to allow for more room on the boat when we plan to anchor fish so I don't need the trolling batteries. It should work well.

[buzbunni]

Saweet!

Now, if you're fishing partner could put you on that big flathead you'd be set !

No more drums.

no

nope

nada

zero

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SERIOUSLY! It was THIS big!

[panolo]

Valv is right on. I have to charge my starting battery about once a month otherwise it will be low in charge.

[Surface Tension]

Its a good idea to charge your cranking battery every so often.
Best advice I could give is get the lights and livewell off your cranking battery and onto your deep cycles. Deep cycles are made to handle slow drains like lights, cranking batteries are not.

[MuleSkinner]

I second what Surface Tension says. I simply ran my entire accessory board to some heavy (6 gauge) wires back to my trolling battery. So now all my starter battery does is crank the engine. Took care of my problem of starting battery being dead when I fish in dark. (Which happened alot-old 40 horse Merc). Have not had a problem since.

[Northlander]

Ill third what ST said. All I run on my main starter battery is my motor and downriggers wich dont get used too much lately. Oh well maybe another week and Ill get the ok to get out.

[Rost]

That same thing has happened to me before. A great tip I learned for this situation is to buy a set of jumper cables and keep them in your boat. Hook them up between your trolling and cranking battery and your off. This way, it only takes about 30 sec to get up and running again.

[Northlander]

I also see guys with those jumper packs in the boat just in case. Great peace and mind.