Onan mcck 6.5 not charging start battery.

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swampman
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Onan mcck 6.5 not charging start battery.

Post by swampman »

So the onan 6.5 on my 82 tri cabin does not seem to be charging the start battery . Now , ive talked to Bob about this via telephone and he says if the generator runs , its charging the battery . My meter says otherwise . I replaced the battery two days ago at Bob's suggestion and took my fluke meter to the boat to do some diag. My generator starts , runs and otherwise powers the boat fine , but i do not see voltage recovery at the start battery after starting the generator . i am aware it would be a very low charge rate in amps , but should i not at least see voltage recovery? I had 12.65 volts immediately after installing the battery . After starting the Genset the battery voltage dropped to 12.5 and did not recover as i would expect while i monitored it for the next half hour . can any tell me if this is normal or am i missing something ?

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Big D
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Re: Onan mcck 6.5 not charging start battery.

Post by Big D »

If I recall correctly, there is a charging circuit fuse on the unit's panel that should be your first check. I believe those have a rectifier and a separate winding or tap for the charging circuit. A wiring diagram would help here. Pretty sure the output on those was 5 or 10 amps max. Check all connections to ensure they're tight and clean including those inside the control box.
She was a 1969 36 ft wooden beauty with big blue 440s that we'll miss forever.
And thanks to the gang, 2012 Trojan Boater Of The Year

swampman
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Re: Onan mcck 6.5 not charging start battery.

Post by swampman »

I have the manual for it , it states it charges the start battery at 1 amp . it also mentions that if unit is subject to frequent starting /cranking , a supplemental charger may be necessary . The charge fuse is good . Last season i hooked the 3rd bank of my onboard charger too it to keep it charged , then i read a statement from Bob @ beacon marine stating not to do this as it will burn out the fuel pump in a matter of seconds . It did not burn up my fuel pump but i disconnected it anyways for fear that it could, being as how Bob is the resident expert i gave some validity to his words .
I have come to believe that either the voltage output on the charge circuit is too low to truly "charge" the battery or it produces just enough to keep the genset running and was not meant to charge in the traditional sense . i certainly don't want to burn out a fuel pump , but im just about convinced a supplemental charge is necessary unless someone can explain to me why im told 'if its running ,its charging" but im only seeing 12.5 volts at the battery while running . 12.5 volts will not bring a battery to full charge level.

mrjake56
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Re: Onan mcck 6.5 not charging start battery.

Post by mrjake56 »

Swampman,
To determine whether the battery is being charged check available voltage at the battery with the genset off. Start the genset and check available voltage at the battery with the genset running. The voltage at the battery should be higher with the genset running. In a perfect world a 12V battery has 2.1 volts per cell or 12.6 available volts. If you see 13V or more with the genset running it is charging. If charging voltage exceeds 14.8V the battery can be damaged.

swampman
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Re: Onan mcck 6.5 not charging start battery.

Post by swampman »

It is not above 12.6 nominal battery voltage with the genset running as i have clearly stated . That is why i am asking for advice . Bob at Beacon marine told me when i called to buy the diode that i thought would fix the charging problem , that if the generator starts and runs it has to be charging , and suggested i needed a battery . I now have a new battery , but still am not seeing charge voltage while running . it stays under 12.6 so im sure my battery will run down eventually .

i am looking for clarification on the statement ' if its running its charging ' , because i am not seeing evidence of this .

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oldboat1
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Re: Onan mcck 6.5 not charging start battery.

Post by oldboat1 »

battery switch set to both?
Motors should run. People -- not so much.

1980 F26, Mercruiser 305
1979 14' Starcraft, 1957 18 hp Evinrude and '57 3hp Evinrude kicker

swampman
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Re: Onan mcck 6.5 not charging start battery.

Post by swampman »

Generator is on a dedicated battery . no switch.

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