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Old 05-06-2017, 09:11   #16
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Re: Do I really need a new battery already?!?

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Originally Posted by jbinbi View Post
If I have my solar/plug in via battery charger/alternator all working, that is the only way I am going to charge the battery. Are you saying I can't fully charge it this way?
Maybe you can with your existing equipment, maybe you can't.

Most stock alternator setups aren't well optimized for getting depleted deep cycling banks back to 100% full as quickly as possible.

What solar controller? How is it programmed?

What shore power charger? How is it programmed?

What voltages do each put out, how quickly do they make the transition from Bulk CC to Absorb CV?

Then how many hours do they hold Absorb before going to Float? What is the algorithm for each source for doing so?

It is the norm that that latter transition happens way too early, so the bank never gets to 100% Full.

Which leads to very early bank Death. Preventing that takes knowledge and the proper equipment.
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Old 05-06-2017, 09:28   #17
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Re: Do I really need a new battery already?!?

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My boat was put into service Oct 15, I brought it from where it was bought to where is was to be winterized. Batteries were disconnected for that winter. Boat was used about 25 days last year, nothing very heavy, all day sailing. I put 2 280 solar panels on it. Left battery connected through the winter.

Getting boat ready for service this past weekend, and noticed last night (so no solar), battery was reading 12.4 with some cabin lights on(all led), 12.5V when I went to bed. I was kind of freaked by this, I am not sure if this seems low, so I got out the hygrometer, and tested 9 of the 18 cells, most read between 1225 (which is the upper end of 'fair' on my device) to about 1250). So this should be OK.

This morning, with the sun out, V is 13.7, which on my MPPT controller is float. The batteries should be fully charged, I ran both engines for about 2 hours yesterday, I have 2 80 A alternators going into a 420 Ah bank. The controllers have been reading float while I was doing work on the hard during the past month.

I can't find a SOC table for my exide batteries, I remember in some post on this forum seeing one. (there are probably lots). did a search, way too many posts. But normally, I think 12.8 is 100% and 12.5 is like 60%? I did not shut the battery switch and measure across the terminals, which I should have done, so there was some load, I should have read this open circuit I think?Can someone post this table, and let me know if I my batteries need replacing already.
Those are normal readings for a new battery at rest. A pair I had recently would read 12.45 and 12.46 in the am with zero load.
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Old 09-06-2017, 10:37   #18
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Re: Do I really need a new battery already?!?

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Originally Posted by jbinbi View Post
Boat was purchased brand new. Assuming batteries are close to that, so 2 years old. Batteries were not connected to boat until Oct 15, then disconnected Nov 15, reconnected May 16, solar installed.

Have Niger Caldwell's book. Have a degree in electrical engineering, but mostly on mathematical analysis of signals. But have more than a basic understanding of electricity.



I am going to assume, and that is wrong of me, but the boat wasn't used for 6 months, from Nov 16 till now. It has 560 w of solar. I know winter isn't the best time, but I would believe that after 180 days, the solar would have charged the batteries. After that, for the last month, while prepping the boat, I have had it plugged in for about 24 hours with a 40A charger. Since it was put in the water, engines have been run about 6 hours, with 2 80A alternators. All during this time, there has been no load except 2 hours of instruments.

I believe that my batteries are fully charged, or should!



This I will do!

Appreciate everyone's input.
Make sure they are installed firmly and with posts side to side, not fore and aft
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Old 12-06-2017, 10:30   #19
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Re: Do I really need a new battery already?!?

12.5 when you went to bed? That is 90% - with no load! You had some lights on, perhaps some other loads that you might not think of - panel lights, etc.,

The last 10% is an ideal that most of us never see. You might want to "test" your batteries by turning off the solar, and leaving your frig, etc on over night and checking the voltage in the morning (after disconnecting everything and letting your batteries rest for an hour) When I start seeing my morning test voltage down to 50% - 12.06v (based on typical overnight loads) I think about replacing my batteries before a long cruise. (New batteries for me show 80% on the overnight test)

Don't worry, be happy, and go sailing.
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Old 12-06-2017, 14:23   #20
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Re: Do I really need a new battery already?!?

Voltage is a very poor proxy for guessing SoC.
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