Charging problem

[John hulme]

Hi guys ,
I have a Suzuki1990’s DT100 V4 that only shows 12.4 volts even at 3000 rpm . If I have the plotter and radio on the voltage drops below 12v at idle . What voltage should I be getting and would the voltage rectifier be suspect ? I can’t put the lights or any other accessories on as the voltage just drops straight away .
Any help would be appreciated

Regards, John

[Simonh66]

What does the battery read at rest?

[John hulme]

Battery reads 13v at rest and 13:65 after charging , it seems to be a charging problem, it copes with running and engine electrics but no other loads

[Simonh66]

It should read around 14.2v at rest, I’d say it’s tour battery

[John hulme]

I’ve changed the battery for two others and they all are between fourteen and 13 , it seems to be on the engine side but I’ll check , thanks

[Seaflyer02]

When the engines running it should be just above 14V. Rectifier usually consists of diodes that change AC output in to DC. Voltage regulator is as the name suggests regulates the voltage. Sounds like the problem is on your charging circuit. Start by identifying your charging coil and check with a test meter

[John hulme]

Thanks for the advice , looks like I’ll need a workshop manual, electrical issues are not my strong point .

[Last Tango]

Originally Posted by Seaflyer02

When the engines running it should be just above 14V. Rectifier usually consists of diodes that change AC output in to DC. Voltage regulator is as the name suggests regulates the voltage. Sounds like the problem is on your charging circuit. Start by identifying your charging coil and check with a test meter

Older engines didn't have a regulator, they only rectified the AC and relied on the battery to regulate the voltage hence the reason "leisure" or "sealed" batteries shouldn't be used with them. They tended to "boil" the batteries so would need topping up regularly. That said, they would only charge at 4 or 5 amps.
I had this issue with a late eighties Evinrude and resorted to fitting a rectifier/regulator for a motorcycle. Dirt cheap and 100% effective.

Need to find out what the OP has.

[ShinyShoe]

Originally Posted by John hulme

Thanks for the advice , looks like I’ll need a workshop manual, electrical issues are not my strong point .

The regulator almost certainly a sealed unit with 4 or 5 wires leading to a (black or metal) box about 2inch by 2 inch that is a heat sink (metal cooling fins on it)

You want to know the voltage going in, and voltage coming out...

Not sure if there are standard wiring colours but at a guess... red and black out to the battery, and yellow / yellow & white to the engine side.

You should use the AC function on your multimeter on the engine side.

If it is giving out 14V on the output... your issue is not the regulator.

If it needs replaced - don't dive into buying a Suzi part... this is almost certainly not engine specific...

[John hulme]

That’s great , I’ll get onto that before I put her back in the workshop .
Thanks for the info , John

[John hulme]

Just a quick update , I managed to get a little time on the boat today and have found the voltage Reg/Rec and hope to test it this week . I’ll keep you posted of progress. Cheers , John

[John hulme]

Thanks for all your help , it was putting out 13.85 engine side at idle and 12.45 battery side so I’ll be getting a regulator.

Regards, John

[Last Tango]

Originally Posted by John hulme

Thanks for all your help , it was putting out 13.85 engine side at idle and 12.45 battery side so I’ll be getting a regulator.

Regards, John

Don't be to hasty. I'd guess neither of those figures is going to cut any ice.

You will loose a bit of voltage through the regulator..just the nature of the beast. You have to try and measure this at a "hard idle" maybe 1500 ish.

I'd be looking for nearer 17volts AC (RMS) to give the regulator a bit of headroom to work with and looking for about 14V at the output. (make sure it's connected to a decent battery when you measure it). You'll not get the kind of charging performance that an alternator gives and it could take a few minutes at hard idle before you start to see the battery voltage creep up.

Sorry, my advice would be go check it again before you dig into your wallet.

[John hulme]

No problem, I’ll check it again at higher revs , the neighbours aren’t going to be pleased . Thanks for the info 👍

[jeffstevens763@g]

Have you got high resistance in your charging cables green joint or dry joint

[John hulme]

Not that I know of but I’ll check them .

Cheers John

[jeffstevens763@g]

john

have a look on youtube for danger marine he does shed loads of stuff it's a great channel he also gives feedback if you contact him

[John hulme]

I will do thanks

[John hulme]

Just a quick update , there were two problems, one was the voltage regulator and the other was a cracked battery lead . All sorted now , thanks for the input