Battery will not Charge

[grs5211]

I have replaced the battery on my 1988 Bayliner capri with Force 125hp O/B motor.
It does have the power switchoff panel, which I use after each use. However the battery is flat when I go out the next weekend. I suspect it is not being charged. How do I test if the Motor is charging back to the battery?

 

[steelespike]

Re: Battery will not Charge

With the motor at about 1500 to 2,000 rpm measure the voltage across the battery terminals.Should be about 14 volts.If your battery is dead after sitting most likely something is drawing it down or it is defective.
Not sure about your motor but most older outboards don't use battery power to run only to run the starter.If your motor starts properly you could probably start it 50 or more times without any obvious change in the battery output.
if you accidently crossed the battery leads then your rectifier is most likely blown.And you won't see the 14 volts only something around 12 +.

 

[RRitt]

Re: Battery will not Charge

do you have a voltmeter?

there is a square thing bolted onto side of starter bracket with four wires. That is effectively your charger. It is a simple, industry standard, square bridge rectifier. For $3.50 you can buy a 50A one from mouser electronics. The only thing special about your $40 "marine rectifier" is the plastic bag it ships in.

Anyway, take your voltmeter and measure AC voltage across one diagonal and then the other (with engine running). You should get anywhere from 10-50V on the input diagonal and zero on the output. If you get 0V-AC across both diagonals then your stator isn't putting out. Now switch your meter to read DC voltage and repeat. You should get zero on the input and 12-14VDC on the output. If you get any significant DC on the input then your rectifier is bad.

Because the force uses the battery as voltage regulator you can't disconnect battery with engine running. If you do then it might fry your console electronics or your ignition. Which means (as far as i know) there isn't an easy way to absolutely, positiviely test your rectifier. If every other part checks out and you're still having troubles, then spring the extra $3.50.

 

[grs5211]

Re: Battery will not Charge

Yes I do have a voltmeter.
Can you tell me what specs I should use to order the rectifier from Mouser. They have a vast array of stuff.
I will try the options you so kindly gave me. Thanks for your input.

 

[RRitt]

Re: Battery will not Charge

there are only three specs
amperage, voltage, physical shape (aka package)

the original was 35A, anything of 35A or higher is fine. I got some 50A modules off ebay for $10 a pair including shipping. You can either crimp on bayonet connectors or tap the center hole 8-32.

voltage doesn't matter since even the lowest available spec is 10x higher than you need.

it is the most common industry standard package for 25-50A square bridge.
You should be able to click on the part number and get detailed info.

 

[Frank Acampora]

Re: Battery will not Charge

Even though the battery is new, check to see that the terminals are clean, corrosion free, and tight.

 

[grs5211]

Re: Battery will not Charge

I found this Rectifier on Mouser for $6.50.
Will this do?

Package / Case: MP-50W
Product: Bridge Rectifiers
Termination Style: Thru-Hole
Product Category: Rectifiers - Bridge
Forward Continuous Current: 50 A
Forward Current: 50 A
Forward Surge Current: 400 A
Max Surge Current: 400 A
Max Voltage Drop: 1.2 V
Reverse Voltage: 100 V

 

[RRitt]

Re: Battery will not Charge

I found this Rectifier on Mouser for $6.50.
Will this do?

Package / Case: MP-50W
Product: Bridge Rectifiers
Termination Style: Thru-Hole
Product Category: Rectifiers - Bridge
Forward Continuous Current: 50 A
Forward Current: 50 A
Forward Surge Current: 400 A
Max Surge Current: 400 A
Max Voltage Drop: 1.2 V
Reverse Voltage: 100 V

if it is the right size and shape then the specs look perfect. make sure that is has the mounting hole in the middle. I don't think they make that package without center mounting hole because thats how it attaches to a heatsink ... but it always pays to be prudent (the starter bracket is your heatsink).

 

[steelespike]

Re: Battery will not Charge

Yes I do have a voltmeter.
Can you tell me what specs I should use to order the rectifier from Mouser. They have a vast array of stuff.
I will try the options you so kindly gave me. Thanks for your input.

Have you checked voltage at the barttery with the motor at the indicated speed?