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Old 06 October 2006, 08:56   #11
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Country: UK - England
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Boat name: Misty Diver
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Hmm,,,
looks like ebay is going to be the most economical answer.
Agree though need a post mortem to ascertain original fault, a lot of repairers are reluctant to speculate on causes and just do exchange repair,,
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Old 06 October 2006, 18:38   #12
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At 17 Volts your engine is over charging ... should be 13.8 to 14.6 volts.

Even though the electronics are rated at a higher voltage this rating is for DC.
If the voltage regulator 9 (or rectifier which converts the AC generated by the engine to DC ) is blown this could allow AC spikes to the electronics which results in RIP to electronics.

Before you fit the new electronics get system checked out.

Also running your engine with this fault could damage the ECU and will definitely boil the battery.

I have seen this before (Auto electrician by trade).
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Old 06 October 2006, 18:46   #13
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Thanks for that,,,,
Will change rectifier and check charge rate as a precautionary,,,,
Thought about putting a secondary regulator inline between battery and electronics to pin down to 12v and offer extra protection,,,,,
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Old 08 October 2006, 16:34   #14
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I wouldn't put a 2nd rectifier inline as this will drop the battery voltage by typically 0.7v so if you are not running the engine and battery voltage is down a bit, the electronics could mis-function.

The battery itself does a good job of absorbing any spikes from the alternator (acting as a smoothing capacitor). All the rectifier does is invert the negative section of the sine wave from the alternator to positive so the voltage level is oscillating from 0v to approx +14v. The voltage at the battery terminals is a smooth 14V. As mentioned, 17V is way to high - I'm surprised the battery wasn't smoking. Normal lead acid batteries start to boil at between 14.4 and 14.8V.

One question - what are the battery contacts like? If the battery gets disconnected when engine is running (eg bad connection), then it's a completely different situation and the input to the electronics will not be a smoothed DC voltage (but will be going from 0v to +14 or higher). The instruments will have some form of power supply filtering (and will all have their own power supply to take input and regulate it down to say 5v for the electronics and MCU) but they may get damaged if an un-smoothed DC voltage is fed to them, especially if the smoothing circuitry in the instrument itself is not designed for this situation (it would require a fairly large capacitor which takes up a fair amount of space).

You may find the actual running voltage was highter than the 17v you mentioned when you did the tetsing (especially if you'd just started the engine and battery was cold when doing your test) - I'm not sure what a marine alternator is capable of generating but some are pretty high current. If the regulator is broken then the alternator can basically go open loop and will just keep pumping out maximum current (and the voltage will rise if there is nothing to absorb the current being produced).

I'd suggest a new battery and regulator / rectifier unit are required and check the battery terminals are good and clean and free from corrosion when re-connecting. I'd also invest in a panel voltmeter for the boat if you don't already have one - gives a really good indication of the battery cindition, alternator status etc.

Al.
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Old 09 October 2006, 16:22   #15
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If your engine only has a rectifier and no regulator it is normal for the voltage to rise to 17 volts as the battery charges.
A Mariner dealers sugested method of holding the voltage down, is to apply a load when the battery is charged (a spot light for example)
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Old 09 October 2006, 18:16   #16
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Originally Posted by rickuk3 View Post
If your engine only has a rectifier and no regulator it is normal for the voltage to rise to 17 volts as the battery charges.
A Mariner dealers sugested method of holding the voltage down, is to apply a load when the battery is charged (a spot light for example)
I cannot believe that an engine would not have a regulator... Any alternator based circuit should have a rectfier and regulator of some description.

17V is not only way to high for a normal battery but also for a lot of electronics, nav lights, engine instruments etc etc. If an alternator can produce 25 Amps (not untypical - I believe the ETEC has 70amp alternator for example), even a a 50w or 100w spotlight is not going to make much difference to that. Without a regulator, this excess current is still pumped into the battery. This has to go somewhere and ends up boiling the battery, not only damaging the battery but producing a fair amount of hydrogen gas which is extremely explosive!
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Old 10 October 2006, 09:49   #17
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Thanks so far!!!!

Firstly chaps,, many thanks for the replies,,,
Now for an update,,,alternator permanent magnet,,same as a motorcycle
rectifier checks out ok,,same values as new item ,,will fit anyway
Have basic manual,,and yes there does not seem to be a regulator in circuit,, ??
No info on expected voltage output??
output max rated at 9amps
coil resistance in spec at 1 ohm,,insulation test between windings /earth>4megohm,,250volt test,,,
Information I don't have is on the other windings that go to the ecu
RD/RD+WE=1KOHM
BE/BE+WE=7KOHM
Engine runs sweet,,,,so nothing suspect there,,,,
Battery connections good as starter motor runs well,,
Seem to remember my old mains car battery charger gave out about 17 volts,,
showing a draw of about 5amps on a near flat battery..

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Old 10 October 2006, 10:05   #18
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Quote:
Originally Posted by al40 View Post
I cannot believe that an engine would not have a regulator... Any alternator based circuit should have a rectfier and regulator of some description.

17V is not only way to high for a normal battery but also for a lot of electronics, nav lights, engine instruments etc etc. If an alternator can produce 25 Amps (not untypical - I believe the ETEC has 70amp alternator for example), even a a 50w or 100w spotlight is not going to make much difference to that. Without a regulator, this excess current is still pumped into the battery. This has to go somewhere and ends up boiling the battery, not only damaging the battery but producing a fair amount of hydrogen gas which is extremely explosive!
Unfortunately my old Mariner/Mercury 50 didn't have a regulator. A rectifier but no regulator. A major design fault but it was built before GPS's and the likes came along, so I guess it didn't matter too much. I was scared witless the battery would explode someday with overcharging. It was a nightmare. I had to run with the lights on all the time until I got a regulator fitted to the sensitive electronics.
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Old 10 October 2006, 11:49   #19
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On the theme of overcharge,,,
This engine with various electronics has run sweet for the last 10years to my knowledge,
Had only 2 batteries ,last one changed due to deep discharge when origional rectifier failed in 2001,, symptom there was no output and had to call into Tobermory, Sound of Mull for a boost charge which got us started and back to Oban,,
Ahh memories,,,,I digress,,,
Can't really get my head around how modern kit designed to run between 10-30v with HV protection, should all flip together without some major kind of voltage/fault current input,,,,but where from?????
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Old 10 October 2006, 16:41   #20
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Quote:
Originally Posted by al40 View Post
I cannot believe that an engine would not have a regulator... Any alternator based circuit should have a rectfier and regulator of some description.

17V is not only way to high for a normal battery but also for a lot of electronics, nav lights, engine instruments etc etc. If an alternator can produce 25 Amps (not untypical - I believe the ETEC has 70amp alternator for example), even a a 50w or 100w spotlight is not going to make much difference to that. Without a regulator, this excess current is still pumped into the battery. This has to go somewhere and ends up boiling the battery, not only damaging the battery but producing a fair amount of hydrogen gas which is extremely explosive!
Older engines did not have alternators, power is produced by coils under the flywheel and just rectified, some instruments are designed to take the higher voltage (Garmin GPS2106 upto 30 volts), but you are always on tender hooks that some thing will blow.
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