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marlinfield

Need to charge up batteries every night. Why??

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marlinfield

Have a 05' VLX i just bought. The guy I bought it from said he needed to charge up the batteries every night. This doesn't make sense to me. I have friends with just as much stereo as me and they do not have this problem.

 

What I have:

 

- 2 AGM Northstar batteries in new shape

-Amp: gladen 4 channel x 150RMS to power 1- 12" focal sub @ 250 watts RMS and 4 x mb quartz 6"x9" speakers @ 75 watts RMS each

-Kenwood Deck with 4 x 45watt RMS to power: Speakers: 6 - Focal 6.5" at 70watt RMS each .

 

I have tested the alternator at idle and it puts out 14.6 volts. 

If i am out on the water doing a mix of half surfing half floating, the battery at the end of the say will be at 11.5 volts. Somehow they arent getting enough juice put back in. The boat will still start but all accessories such as perfect pass and the tach wont work when batteries get low.

Stereo isnt anything crazy. Doesnt make sense to me why the batteries are not getting fully charged up.

 

Thanks for any help!

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mikeo

Maybe I missed it, but how old are the batteries? Most batteries don't last more than about 5 years, and if they've been over-charged (unregulated charger) every day then they may be fried internally.

You state that they're AGM batteries, so they're probably "maintenance free" and you can't do anything to the electrolyte. Take one to a local auto parts store and have them load test it, (not that I would want it to) but I'll bet it fails a bench test.

I've had a few "lemon" batteries that were new and wouldn't hold a charge, but my bet is on age.

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MadMan
6 hours ago, marlinfield said:

 

I have tested the alternator at idle and it puts out 14.6 volts. 

If i am out on the water doing a mix of half surfing half floating, the battery at the end of the say will be at 11.5 volts. Somehow they arent getting enough juice put back in. The boat will still start but all accessories such as perfect pass and the tach wont work when batteries get low.

 

Are you saying that even with the alternator putting out 14.6 volts the accessories won't work?

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marlinfield

Mikeo - batteries were new last summer, i was thinking of getting them load tested as well but not sure if that will be the case. ill do that next week when im back from work to be sure.

 

Madman - correct, if i dont charge up overnight then when i go out the second day the perfect pass wont work and will beep consistently and the tach bounces all over the place even with the boat idling putting out the 14.6 volts. I had hoped the alternator was putting out low voltage due to being worn out but unfortunately thats not the case. will check batteries next week with a test, otherwise im not sure what else.

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oldjeep

I'd be checking your accessory ground bus

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marlinfield

oldjeep - what should i bee looking for in the negative bus? i have been under there and looked at it. but not sure what i should be looking for as far as potential issues?

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oldjeep
9 minutes ago, marlinfield said:

oldjeep - what should i bee looking for in the negative bus? i have been under there and looked at it. but not sure what i should be looking for as far as potential issues?

Just that the connections are tight and clean.  Take the main ground off the bus and make sure that it doesn't have any corrosion, use some dielectric grease on it.  Do the same thing with your negative battery cables.  Just sounds like a bad ground issue to me if it starts fine but isn't powering the accessories properly.

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RTS

And the measure of an alternators health would be how many amps it's putting out, not the voltage.  My money is on batteries that are bad...and likely older than seller disclosed.  

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MLA
19 hours ago, marlinfield said:

I have tested the alternator at idle and it puts out 14.6 volts.

So where was this measurement taken, batteries or right off the alt? Next questions, are the batteries actually reaching a full charge? 

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marlinfield

i tested this right off the alt. i also tested the batteries. number 1 battery which hadnt been used the day before was at 14.6v and batter 2 which had been used the day before was at 12.4 and slowly climbing as it ran

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marlinfield

Thanks RTS. I pulled the batteries out last week as part of my winterization tasks. I will be taking them into the battery shop next week to have them run a test. would be nice if this were the issue. Ill confirm my findings when i find out.

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MLA
19 hours ago, marlinfield said:

number 1 battery which hadnt been used the day before was at 14.6v and batter 2 which had been used the day before was at 12.4 and slowly climbing as it ran

Something is not right here, unless the boat has a VSR/ACR between the banks. If one battery was ready full alternator charge and the other was coming up, then the batteries are somehow wired in parallel yet with a problem. They should both read dang near the same. Just an FYI, 12.4 is only a little low for a battery that didnt just come off a charger. 

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marlinfield

MLA - the reason the batteries would be different voltage is because the night before i charged them both up to 14.6 volts. the next day on the water i had the perko turned to battery 2 which is why the voltage was down on battery 2 compared to number 1.

 

Update - i had the batteries load tested today and are in great shape. batteries are not the issue. next step will be to an amp check on the amperage output of the alternator in the spring to see if its performing properly. if so, i guess a high output alternator is in my future.

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MLA
1 hour ago, marlinfield said:

if so, i guess a high output alternator is in my future.

I doubt it

 

1 hour ago, marlinfield said:

because the night before i charged them both up to 14.6 volts. the next day on the water i had the perko turned to battery 2 which is why the voltage was down on battery 2 compared to number 1.

A 12V battery will not charge to 14.6. Thats charger voltage, not battery voltage. 

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marlinfield

Forgot to report my findings on here. batteries are fine, alternator is fine. Batteries were draining and not charging because previous owner had batteries wired in a** backwards. Had it so one battery was never receiving a charge from alternator and then had it so amps were always hot even with the switch off so it constantly drained down batteries.

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JasonK

Nice find

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MLA
3 hours ago, marlinfield said:

 then had it so amps were always hot even with the switch off so it constantly drained down batteries.

Going to bookmark this post for the next time the battery switch debate comes up.  

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