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Depth sounder affected by state of battery charge
On my last outing to Tangalooma, my sounder - a Navico DS 200 instrument - did its usual trick of reading "3:93 ft". Not very helpful really... I have had earlier trouble with it - now fixed - caused by a leak in the transducer mounting well. This resulted in low castor oil level and poor "pinging". This week's bad reading seems however to be related to the charging voltage from the Yamaha outboard. I proved this by switching to a lesser charged battery, and by switching on some load on the battery (lights) to drop the voltage. Either of these actions was enough to correct the problem.

So my question... Has anyone else experienced similar problems with (perhaps) the outboard charger reaching too high a voltage (? maybe over 14 volts) or the charging circuit being a bit simple and noisy on outboards compared to alternators? (The 9.9 4 stroke Yamaha just uses a magnet spinning in the flywheel to make its power).

[My two sinkers on the piece of cord seems to work irrespective of battery voltage, doesn't need castor oil, and is very accurate in shallow water].

Phil Gardam30-Apr-2004    Edit    Delete 
Voltage affecting instruments.
A few years ago when we were racing Go Karts, a circuit was using electronic scales to measure class weights. during the day the weights would appear to change, after much discussion and argument it was found that the dropping voltage was causing the problem. Most gauges and instruments in cars operate at about 9 volts so that they are stable most of the time. I don't know about marine instruments, but wouldn't be surprised if they were the same. I hope this helps. M, ambuscade 2
Martyn2-May-2004    Edit    Delete 
Yamaha 9.9 voltage
Hi Phil, My Yamaha 9.9 spits out up to 15v into fully charged batteries and I think it is responsible for damaging them. I am looking into splitting the motor starting and charging cable so I can control the output voltage. Any tips you find would be of interest to me. John
John Markwell4-May-2004    Edit    Delete 
Splitting starting cables from charging cables
Thanks John - I've rewired my motor with heavier cables to get better starting and charging and your reading of 15 or so volts seems quite similar to my 14.something volts. I've had the same thought of splitting starter motor load from the charge / discharge current created by charging and lights etc - as is done for automotive ammeters. My intention was to be able to put an ammeter of about +/- 50 amps in the charge / discharge circuit and not have it burn out under the 100's of amps of starting. On my 9.9, the charge wire from the regulator joins the heavy starter-motor cabling under the Yamaha cowling near the starter motor. To monitor charging / discharging, I think I would need to disconnect this charge wire from the battery cable under the motor cowling, attach the charge wire to a separate heavy cable (? 50 amp), and run it to the back of the instrumanet panel. This panel is probably the "centre of load". From there the cable could run via an ammeter to the battery selector switch. I haven't tested this arrangement, and if I was to do it, that would be the next step. The down side would be introducing into the charge circuit additional cabling of slightly higher resistance than the heavy gauge starting cable I now use. Given the 15volt problem, this could be an advantage in dropping the charge voltage! I always get a warm and cosy feeling when I am able to see what current is going into / out of my battery - as opposed to terminal voltage. With current, I can do sums like: "How long have I got before this battery is flat?" Hope this makes sense. Let me know / drop me an email if you are thinking of trying it.
Phil Gardam4-May-2004    Edit    Delete 

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