Battery charging voltage

[kaman]

Managed out in my sib a few days ago to break in my new Tohatsu 9.8hp 4 stroke.
The engine has a rectifier/ charging coil fitted to it.
On rigging the charging circuit up to my little 12 volt 7ah which runs my sonar / phone charger the voltage sky rocketed to over 17.5 volts 😳 .
Voltage stabilised once the engine stop running but shot up again upon restart.
I know this is probably down to the small capacity of the battery but is this safe enough to use.
I had visions of the battery boiling up inside 😂 .
TIA!

[Salty Pete]

Can't help you in regards to your engine etc but looking at the manual for my 30HP Suzuki, the output of the charging coil is 4V manual start and 8V electric start.

Looking at that yours does appear a bit high. Your engine may be missing a regulator.

[jakew009]

Originally Posted by Salty Pete

Can't help you in regards to your engine etc but looking at the manual for my 30HP Suzuki, the output of the charging coil is 4V manual start and 8V electric start.

Looking at that yours does appear a bit high. Your engine may be missing a regulator.

4 volts or indeed 8 bolts is not going to charge a 12 bolt battery. You have your figures muddled.

[jakew009]

Originally Posted by kaman

Managed out in my sib a few days ago to break in my new Tohatsu 9.8hp 4 stroke.
The engine has a rectifier/ charging coil fitted to it.
On rigging the charging circuit up to my little 12 volt 7ah which runs my sonar / phone charger the voltage sky rocketed to over 17.5 volts 😳 .
Voltage stabilised once the engine stop running but shot up again upon restart.
I know this is probably down to the small capacity of the battery but is this safe enough to use.
I had visions of the battery boiling up inside 😂 .
TIA!

How are you measuring the voltage? Are you sure your meter is not crap?

Try it in a bigger car battery and see how it behaves. But it sounds like the rectifier circuitry might be dodgy.

[Oldman2]

Sounds to me like the outboard has a charging coil fitted (for lighting) but no rectifier.

[mikehhogg]

normal charging voltage should appear as 13.8 to 14.5 . as mentioned it appears to be an unregulated output or the multimeter or measuring device is on the wrong setting.

[kaman]

Pretty sure the meter is accurate as getting the same voltage on my battery meter and reading on my Garmin depth sounder voltage meter too.
I'll have a look at the wiring and see if there's something wrong.
It's the proper Tohatsu rectifier kit that's been fitted to it.
Just wonder if it is running off the lighting output and not the charging output if that output is unregulated....?

[mikehhogg]

do you have the part number for the charging kit fitted it should be

3V2 76160 0

You would also have to fit alternator coil

[jeffstevens763@g]

sounds like its not regulated just a rectifier. unless its a bad battery some info below

[kaman]

Hi here are the part numbers fitted

Quicksilver Parts:3V2-06128-0 Genuine Alternator Kit

Tohatsu Parts:3V2-76160-0Genuine Tohatsu Rectifier Kit (MFS8 MFS9.8)

[Pikey Dave]

Originally Posted by kaman

Pretty sure the meter is accurate as getting the same voltage on my battery meter and reading on my Garmin depth sounder voltage meter too.
I'll have a look at the wiring and see if there's something wrong.
It's the proper Tohatsu rectifier kit that's been fitted to it.
Just wonder if it is running off the lighting output and not the charging output if that output is unregulated....?

My brand new Suzuki 20hp was advertised by Suzuki as having “6A available for lighting & battery charging”. What it doesn’t tell you is that you have to fit an additional £100 regulator in order to access it. I suspect you’re in the same boat, so to speak. You’ve got the coil but need to fit a regulator to, well, regulate it.

[kaman]

��
Just spoken to a Tohatsu tech on the phone where I bought the set up.
He says there is a minimum Ah size of battery that needs to be fitted to the charging circuit.
His explanation was that basically the battery is too small, the kit is not sensing a strong enough current therefore its throwing its maximum charging output of 18 ish volts into the battery.
He says try it on a larger battery and see if it stabilises. Doesn't sound right?
A bit counterproductive if this is the case as I'm trying to keep my setup light. I don't want a large battery �� �� ��

[Pikey Dave]

Originally Posted by kaman

��
Just spoken to a Tohatsu tech on the phone where I bought the set up.
He says there is a minimum Ah size of battery that needs to be fitted to the charging circuit.
His explanation was that basically the battery is too small, the kit is not sensing a strong enough current therefore its throwing its maximum charging output of 18 ish volts into the battery.
He says try it on a larger battery and see if it stabilises. Doesn't sound right?
A bit counterproductive if this is the case as I'm trying to keep my setup light. I don't want a large battery �� �� ��

Hmm[emoji848] ergo, when your “large” battery gets charged & the current tails off as the internal resistance rises, the regulator will ramp up & try to drive yet more current through at 18V. That 18V will also be applied to any kit connected to the battery. I’m not convinced. Also, why would you want a large battery connected to a 9.9hp motor. Doesn’t sound quite right to me.
What is the spec of your current (see what I did there) battery?

[Fenlander]

If the two kits Kaman has fitted (post #10) have accurate descriptions then he's fitted a coil to get an AC output and a rectifier to convert to DC. Nowhere is there mention of the regulator needed to keep the voltage stable at higher revs.

I think the Tohatsu guy... sadly... misled him re the battery size. After all some motorcycles have batteries around 8AH size and because their charge output is regulated they don't see much more than a 14v charge.

I'd be looking for a generic regulator or even a generic rectifier/regulator to replace the Tohatsu rectifier... they're only a tenner.

[kaman]

Cheers guys for the input.
So it looks like maybe the kit i have been sold does not regulate the output voltage.
It was sold as a complete all you need kit.
Clearly something isn't right when my battery is reading 18+ volts!
I'll phone them back !

[kaman]

Spoken to Workshop Manager.
He says the kit they sold me should regulate the voltage going into the battery hence it is a regulator/ rectifier combo.
He is calling Tohatsu today and will feed back later this afternoon.
We will see.......

[jeffstevens763@g]

worth reading Kaman


https://www.sailnet.com/threads/smal...%20at%20only%2

[kaman]

Originally Posted by jeffstevens763@g

worth reading Kaman


https://www.sailnet.com/threads/smal...%20at%20only%2

Cheers Jeff.
Seems there may be an element of truth that the high voltage readings could be due to the small battery.

[jeffstevens763@g]

Yep in the scheme of things your around 2.5 to 3 volts over the norm of 14.5 volts you’ll get voltage drop across the battery more plates more resistance my 12 AMH runs at 15 volts regulator supposed to be 14.7 volts. If you can get hold of a larger battery to prove would be my next move. I have read that a duff battery can through the regulator out also the voltage of around 14.5 volts goes to the battery the rest to ground from the regulator my guess a 14 AMH battery will sort it if the charging kit is ok

[kaman]

Cheers for the input guys.
Not heard back as of yet what Tohatsu UK are saying to the matter.
In the meantime I've ordered a 12Ah battery.
I'm not prepared to go any bigger than that in that particular Sib set up as I'm trying to keep the weight down.
Hopefully that will tame the voltage down.
If not the kit will be getting removed and sent back for a refund as I'd rather just take the 7ah as aspare battery if I'm going away multi day camping than run a battery at 18 + volts.
My larger Sib has a 28ah battery connected to charging circuit on my Tohatsu 20hp 4 stroke.
It sits nicely around 13.4 volts when I'm buzzing along.