Increasing Alternator output

[bubblehead]

I have an older (93) Merc 9.9. When running at trolling speeds my voltage output is only about 11.3-11.5 volts. This becomes a real problem at night when I have to run with my running lights on. If I run up the RPM, I can then get 12.5-13 volts after running it awhile. As a result of this, I have to intermittantly (every 30-45 minutes) start and run my big motor to charge up the battery. I know from previous automobile expierience that we would change stators (like from and older 42 amp GM, to a 60 amp stator, same housing) Has anyone tried this? Or any other suggestions to give my output a boost?

Thanks

 

[Laddies]

Re: Increasing Alternator output

That would sure be a easy fix wouldn't it but no one that I know of builds one. If you could find a electric whiz they could probably wind one for you but it still wouldn't charge at idle I'am afraid

 

[j_martin]

Re: Increasing Alternator output

A group 24 battery in decent shape should run the running lights for 20 hours or more. If you're running a couple of live wells also, or entertainment electronics, that cuts down your time.

I wouldn't expect the main engine to recharge it fully on the way in, unless you have a long run. If you start with a fully charged battery in good condition, you shouldn't have an issue. Put an automatic charger on it between uses.

Either leaving the battery discharged, even partly, or overcharging it with a cheap charger will greatly shorten it's life.

 

[JCF350]

Re: Increasing Alternator output

Need more battery or batteries, if the one you have is in good shape.

 

[domains]

Re: Increasing Alternator output

Stator can be recoiled thicker with rebuilding it .Alternator shops or electricians should know specs on overwraping stators for more output. Guy up here rebuilds for 160$ expl. But more output not sure what else needs twicking.

 

[JCF350]

Re: Increasing Alternator output

Stator can be recoiled thicker with rebuilding it .Alternator shops or electricians should know specs on overwraping stators for more output. Guy up here rebuilds for 160$ expl. But more output not sure what else needs twicking.

"overwraping" a stator will only give you more amps not an increase in voltage. For an increase in voltage you need more push and pull. This is a permanent magnet alternator. So for more voltage at a lower rpm you would need stronger magnets.

 

[j_martin]

Re: Increasing Alternator output

"overwraping" a stator will only give you more amps not an increase in voltage. For an increase in voltage you need more push and pull. This is a permanent magnet alternator. So for more voltage at a lower rpm you would need stronger magnets.

You could wrap the alternator for whatever combination of voltage and current you want within the confines of the strength of the magnets.

More turns of finer wire will give you more voltage at any rpm and less current.

 

[JCF350]

Re: Increasing Alternator output

You could wrap the alternator for whatever combination of voltage and current you want within the confines of the strength of the magnets.

More turns of finer wire will give you more voltage at any rpm and less current.

After doing some checking I stand corrected:redface:

Plus I learned something about voltage regulation that I didn't know before.


http://continuouswave.com/whaler/reference/PMA.html

 

[MercFan]

Re: Increasing Alternator output

Since the output from the stator is AC, wouldn't it be simpler to wire a step-up transformer into the line, with a bypass switch that you can flick when you're done trolling?

But in all honesty I'd suspect a damaged/worn/old battery. It's just chewing too much power the whole time, and you really notice it at low rpm. Never let your battery drop below 10.5V.

 

[Texasmark]

Re: Increasing Alternator output

Following along with this, some comments:

The Merc sales brochure for a fairly recent 9.9 indicates a 70 watt max capability which is not had at idle....gotta have it wound up pretty good to get max out of it......even though it's an alternator.

Inductance is what produces voltage....V = L di/dt where L is inductance, di is current and dt is time. di/dt in this case is the frequency of the sine wave produced which is the number of poles x rate of flux change....rpm's.

L is inductance and is the unit for magnetic strength: Number of windings (complete turns of wire) being cut by magnetic movement, strength (in gauss) of magnet, and location of rotating magnet to coil of wire.

So if you want more of what you have you have to change something that makes V larger per the equation.
------------------

But, barring a malfunction, if your battery is fully charged and in decent shape, the OEM alternator should be putting out more like 14v at moderate rpm's. You aren't even getting to the fully charged battery voltage which is 12.75 for me. Others have a different number but this works for me.

I think you need to look at your battery.

A 3-4" 12v sealed beam (for farm use anyway) is rated at 35 watts. That says that if you start with a fully charged battery, and run your engine at half throttle or better, you ought to maintain your charge running 2 lights.

HTH

Mark

 

[bubblehead]

Re: Increasing Alternator output

I understand that the voltage is a function of the power output P=I x E. My explanation of low voltage was a layman's term of saying i need more power. I have a 31 series deep cycle battery, it held up much longer than the 27 or 39 series. BUT, my problem with running a Lowrance X-38, AND the GPS, AND the running lights, is that after an hour or two, the voltage (a function/indication of the power output of the alternator) drops. I was just wondering if anyone had ever beefed these up? THanks for the input and any further comments.

 

[domains]

Re: Increasing Alternator output

Get a cigarette lighter adaptor and run a 120v outlet ,then get a 10amp charger and charge batt.

Might need other twicking for this mod.

 

[JCF350]

Re: Increasing Alternator output

Get a cigarette lighter adaptor and run a 120v outlet ,then get a 10amp charger and charge batt.

Might need other twicking for this mod.

Where is the power going to come from? I assume you are talking about using an inverter?

 

[domains]

Re: Increasing Alternator output

Power will come from a third batt . to invert 12v to 120v then charge with 10amp for 10 mins then drop to 2 amp for 2h.

 

[JCF350]

Re: Increasing Alternator output

Power will come from a third batt . to invert 12v to 120v then charge with 10amp for 10 mins then drop to 2 amp for 2h.

While there might some out there, every battery charger I've seen (besides my cell phone charger) doesn't like the output from a MSW inverter so you would need to get a true sine wave inverter (BIG BUCKS!!).

Why not just put the third battery in the circuit with the one being used as a "house battery" then you won't be wasting power to run the inverter?

 

[Sig_Mech]

Re: Increasing Alternator output

I think we need to take a step back and use the K.I.S.S proceedure. Before we even talk about rewinding, third batteries and power inverters, let's address the original problem. Make sure that your battery is in top condition and that you have no dead cells and that it will take and hold a charge. Then make sure that all the connections and splices for the charging system (stator, rectifier, etc ) are clean and tight. Is your rectifier good? Now check the wiring and sockets for all your lights. Broken or frayed wiring can add resistance to your charging circuit and drag your voltage down. While you're at it, check the lamps in the sockets, make sure that the bases are clean and that there is no corrosion built up in the socket. These things might help in curing the main problem. Another thought would be to switch all your lighting to LED's. They might cost alittle more but they will last longer and they don't require as much power to run as incandescent lamps and it will probably be cheaper than a stator rewind.

 

[bubblehead]

Re: Increasing Alternator output

The battery is good, the connections are clean, the lights and powered on accessories all had new or recently updated wiring. The motor will charge the battery up at higher rpm, as I've had to run it this way when it discharged the battery too much. But, when I'm just trolling, the amount being generated is not as much as be used. I switched to the 31 series battery to help give me more run time, and it has increased the amount of time I can run quite a bit. I also carry another 31 series battery as a backup, so I can use it for an emergancy jump start for the big motor if I do get too discharged. But, once again, I was just wondering if anyone had come up with a fix for these older low amperage alternators. I know that up until just the past few years when the motor manufacturers finally caught on, none of these little motors had much of a charging factor. You see the new ones listed at much higher capacity, but I think these were only rated for like 6 amps.

Thanks again

 

[domains]

Re: Increasing Alternator output

Check if new 9.9 stators fit on older models for overcoil. Or you could invest in a small generator there cheap on gas besides that like stated clean all connections. When charging batt 10amps if you see lots of bubbles within a min of charging in one cell then its weak and that could be your prob.

 

[domains]

Re: Increasing Alternator output

Laddies is the man. I guess retired knowledge that has my Most respect..i'm 34 reminds me when i was younger mechanic told me why buy needle and valve system when you can grind them. Now its rubber tips but just evolution .

cheers.

 

[MercFan]

Re: Increasing Alternator output

If everything is in tip top shape and there really is nothing wrong, except that the engine is really running at too low rpm, I'll make 4 more recommendations.
1) If they're not already, change your lights to the energy saver type globes, instead of normal halogen+filament types. They use much much less power, and your charging circuit might just be able to keep up.
2) Change your prop to a much finer pitch so you can rev a drop higher and still maintain trolling speed.
3) You can even just have the diameter of the prop turned down on a lathe, to just make it much less efficient. That'll also keep the speed down, and bring the rpm up.
4) You can also drill vent holes in the prop. The exhaust gas that'll pass through these holes will give you some good prop slip at troll speeds. So you'll also need to run a bit higher rpm to maintain troll speed. From my experience the point of not charging, to actually charging are very close to each other. To give an example, the circuit might charge at 20% capacity at 1500rpm, but it'll charge at 80% at 1800rpm. It's very sudden, I don't know why though.

Play around with your throttle. Forget about maintaining troll speed and just see how much rpm you need to kick up the charge. It won't be much, probably 500 rpm more.