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Hello, once again sailing in Nova Scotia after one long Winter.

I have checked my marine battery with two different voltmeters and I get a high reading of 15.7.
I checked this battery throughout the winter and got the same reading. I understand this may indicate a worn out battery. Is that correct?

Also, with a 30 watt solar charger connected to the battery in full sunlight what reading should I be getting on the battery?

Any recommendations for best marine battery?

Thanks.

Peter, Elan 7.7 trimaran
 

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The resting voltage of the battery depends on what type it is, each battery chemistry has different optimal values. Along the same lines, a 30W unregulated solar cell could be putting out 18V and could overcharge the battery so the voltage reading at charge could be any value. It depends upon which charger and what charge method it uses.
 

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bingo...I bet that panel is unregulated...

are you testing the battery voltage isolated from the panel and all other sources?
 

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Hello, once again sailing in Nova Scotia after one long Winter.

I have checked my marine battery with two different voltmeters and I get a high reading of 15.7.
This is NOT GOOD...


I checked this battery throughout the winter and got the same reading. I understand this may indicate a worn out battery. Is that correct?
By now your batteries are pretty much toast if the meters are to be believed..

Also, with a 30 watt solar charger connected to the battery in full sunlight what reading should I be getting on the battery?

Any recommendations for best marine battery?

Thanks.

Peter, Elan 7.7 trimaran
You can't simply direct connect a 30W panel to a battery without a charge controller. Sounds like you need a controller and a new battery....
 

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Discussion Starter #5
Thanks for the replies.

I checked the battery without the panel connected. I had checked the battery periodically throughout the winter and it read around 15.

Another piece of information is that connected to the panel which is in full sunlight the reading only goes up to about 16.5. I remember is as being much higher.

The battery is about 4 years old. Years ago, I had read that a 30 watt panel could be directly connected without a controller. So, it was connected directly on a previous boat and now this one. The batteries seems to have lasted about 4-5 years.

Also, there is low drain on the battery just an autopilot and handheld GPS.
 

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Im surprised they lasted that long...

I killed a flooded deep cycle in one season by connecting a smaller 10-15watter but it went up to 18-19volts unregulated...

it was the first time I was away from a boat so long so figured it was fine...but I learned the hard way...battery was completely shot when I got back 6 months later

you must explain what battery type you have some have high voltages as standard around 14.5 volts...forget which ones..
 

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Discussion Starter #8
It is a Group 24, deep cycle marine battery.

It is not a fixed solar panel. My normal practice is to set the panel up when finished sailing.
I disconnect and store it when I sail. Depending on weather etc. I may get a few hours charge. It is never left connected for more than a few days.
 

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petertribo - Group 24 just refers to the size, and deep cycle means it has thicker plates, but neither tells us what the voltages should be. Do you have a make and model? Is it a sealed battery or can you check liquid levels in it?
 

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its more than likely a floooded acid battery where typical charging voltages are around 13.5 and the battery when alone should be in the normal 12.5-13v range if in good condition

btw op just cause you disconnect the panel doesnt mean you arent doing harm when charging...

its still pumping out over 16 volts...I bet at midday sun with clear skies you will see 18 volts

thats still an UNREGULATED panel so either get a cheap pwm charge controller or get a better panel and use mppt controller to get the suns full advantage

cheers
 

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btw if indeed you have 15.7 volts at the battery with nothing connected...many things like small bulbs and the like or fuses might pop...so are you absolutely positive that the voltage is 15.7 with NOTHING connected to the battery, not even the battery switch, negatives etc...?
 

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Discussion Starter #12
Thanks for all the info.

It is a 12 volt, flooded deep cycle battery. From the posts, I see the problem.

I will replace the battery. So, for a Group 24, flooded, deep cycle battery using a 30 watt panel what would be the specifications for a pwm charge controller? Best brand of controller to buy?

Also, I am just wondering why this battery is reading 15.7 and did so all winter with no charging at all. I checked it with two voltmeters.
 

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a 10amp pmw will do you good...and allow for adding another panel at a later time...
 

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Best choice is a Genasun MPPT controller - the GV-4 if the 30 watt panel is all you will have or the GV10 if you plan to add another panel. They will give you the best charging from the panel at the proper voltage.
 
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