I have a 6 hp Johnson outboard for my sailboat. The motor has a charger which I hook up to my battery and help provide some juice while I motor in and out. Last year when I was commissioning the engine I checked out the voltage output from the charger - I just connected my meter across the the output and saw that the voltage varied with speed from about 7 volts when the motor wasa at idle to more than 17 volts when the engine was running at speed. There was no load on the output. I have heard that this is normal. How should I check out the charging unit? Is there someone who can provide an answer or can point me to the place with an explanation? Thanks in advance for your help and guidance. James O'Day 23 Bognor Limey
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James
I'm sure you must have been reading amps of output from the rectifier (that's the name of the little "charger"), not volts. Seems you measured its output under different rpms. So you know it works. What exactly is the question?
I'm sure you must have been reading amps of output from the rectifier (that's the name of the little "charger"), not volts. Seems you measured its output under different rpms. So you know it works. What exactly is the question?
Sounds normal
The voltage from the charg1ng system would vary with engine rpm if no battery is connected to the output. Connect a charged battery and with the engine running at somthing above idle the voltage should be between 13.5 and 18 volts and may vary somewhat with engine rpm. If its their your good. If the battery is dead or bad it will pull the voltage low and you will get reading out of spec. The important thing to remember is that if you disconect or connect the battery when the engine is running you can dammage the diodes in the charging system. If you suspect the charging system has problems always have the battery checked because a bad battery is a load on the charging system. It pulls the voltage low and keeps the charging system running a 100% all the time and thing burn out in the charging system. At the price things on boats cost and batterys are cheap, still most boats have junk for batterys.
The voltage from the charg1ng system would vary with engine rpm if no battery is connected to the output. Connect a charged battery and with the engine running at somthing above idle the voltage should be between 13.5 and 18 volts and may vary somewhat with engine rpm. If its their your good. If the battery is dead or bad it will pull the voltage low and you will get reading out of spec. The important thing to remember is that if you disconect or connect the battery when the engine is running you can dammage the diodes in the charging system. If you suspect the charging system has problems always have the battery checked because a bad battery is a load on the charging system. It pulls the voltage low and keeps the charging system running a 100% all the time and thing burn out in the charging system. At the price things on boats cost and batterys are cheap, still most boats have junk for batterys.
Me too.
I also have a Johnson 6hp twin with charger. I put a voltmeter across the two cables exiting the outboard and found the same thing, voltage went from 6 volts or so at tickover to 19 volts at higher revs. I assumed the cables must go to a regulator, or even a rectifier/regulator, which would regulate the output to something like 14 volts which is normal to charge a 12 volt battery. 19 volts is much too high. My concern is that any electrical devices attached to this output would be damaged (or fuses would blow) at such high voltages. I didn't want to take the risk of damaging my new Navman so haven't investigated the problem further as yet. If someone KNOWS that an external regulator is typically needed for this outboard, please let me know...!
I also have a Johnson 6hp twin with charger. I put a voltmeter across the two cables exiting the outboard and found the same thing, voltage went from 6 volts or so at tickover to 19 volts at higher revs. I assumed the cables must go to a regulator, or even a rectifier/regulator, which would regulate the output to something like 14 volts which is normal to charge a 12 volt battery. 19 volts is much too high. My concern is that any electrical devices attached to this output would be damaged (or fuses would blow) at such high voltages. I didn't want to take the risk of damaging my new Navman so haven't investigated the problem further as yet. If someone KNOWS that an external regulator is typically needed for this outboard, please let me know...!
The output is unregulated
James question is a valid one. I too have an outboard which outputs power to the batteries. This output is rectified to DC by a bridge diode block (if you're wondering, it's a square thing about one inch square with four terminals) but it is not otherwise regulated and can overcharge the batteries to the point that the depth sounder shuts down. This is a problem for the batteries too, and I would like to find an aftermarket regulator that would control this output. The are several technical reasons why this product may not exist, but if anyone knows of such a device I would like to hear about it. Remember, the charge comes from a magneto not an alternator so it can not be regulated buy a typical regulator. I use a 12 volt DC cooler (peltier cooler) which draws a lot of power to control the charge now but that is less than ideal. Ahy thoughts?
James question is a valid one. I too have an outboard which outputs power to the batteries. This output is rectified to DC by a bridge diode block (if you're wondering, it's a square thing about one inch square with four terminals) but it is not otherwise regulated and can overcharge the batteries to the point that the depth sounder shuts down. This is a problem for the batteries too, and I would like to find an aftermarket regulator that would control this output. The are several technical reasons why this product may not exist, but if anyone knows of such a device I would like to hear about it. Remember, the charge comes from a magneto not an alternator so it can not be regulated buy a typical regulator. I use a 12 volt DC cooler (peltier cooler) which draws a lot of power to control the charge now but that is less than ideal. Ahy thoughts?
They call it a Zeiner Diode
Lots of motor cycles have this kind of arangement (magneto-battery) and they don't overcharge their batteries. The zeiner diode counducts until a certian voltage is reached. Then it stops counducting. So you put one of these puppies as a control circuit to a transistor of sufficient size and wala, you have a regulated magneto. If you want me to I'll bore everybody with a cirucit diagram but if you are atempting this you can figure it out for yourself as it is not that complicated.
Lots of motor cycles have this kind of arangement (magneto-battery) and they don't overcharge their batteries. The zeiner diode counducts until a certian voltage is reached. Then it stops counducting. So you put one of these puppies as a control circuit to a transistor of sufficient size and wala, you have a regulated magneto. If you want me to I'll bore everybody with a cirucit diagram but if you are atempting this you can figure it out for yourself as it is not that complicated.
Flexcharge Controller
I have used the Flexcharge NC25A charge controller on outboard motors for several years. They work great and keep the outboard motor from overcharging the batteries no matter how much you motor. Go to Flexcharge.com for this one and other solar chargers, etc. They are fairly easy to find at the usual marine merchants.
I have used the Flexcharge NC25A charge controller on outboard motors for several years. They work great and keep the outboard motor from overcharging the batteries no matter how much you motor. Go to Flexcharge.com for this one and other solar chargers, etc. They are fairly easy to find at the usual marine merchants.
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