Battery charge question

[Mark42]

I have been charging the marine battery (not deep cycle) on a 2 amp charger setting to get it ready to put in the boat. The multi-meter shows the charge to be 13.43 volts, and slowly drops down. Checked it again this morning after sitting all night off the charger and its holding steady at 12.93 volts.

I guess the battery has a bad cell. So I did a search on this forum for some battery info and found this thread that says not to charge on 2 amps:

http://forums.iboats.com/showthread.php?t=295932

So I'm wondering if the battery should go back on the charger at the 8 amp setting or is it just on its way out?

Battery is about 4 years old, and all cells are topped off with distilled water.

 

[Chris1956]

Re: Battery charge question

Mark, Amperage and voltage are related. When you first started charging the battery the voltage was higher since the battery was not fully charged. After a while the charging rate was lower, and the voltage was lower. Put the multimeter on the battery charger, when it is disconnected from the battery and you will see 14VDC. The load of the battery brings it down when you first connect it. As the battery charges, it's load becomes greater, dropping the charging rate and voltage.

That 2 Amp trickle charger is actually superior to the 8A charger (IMHO), if you have the time to wait for the battery to charge.

 

[Mark42]

Re: Battery charge question

Mark, Amperage and voltage are related. When you first started charging the battery the voltage was higher since the battery was not fully charged. After a while the charging rate was lower, and the voltage was lower. Put the multimeter on the battery charger, when it is disconnected from the battery and you will see 14VDC. The load of the battery brings it down when you first connect it. As the battery charges, it's load becomes greater, dropping the charging rate and voltage.

That 2 Amp trickle charger is actually superior to the 8A charger (IMHO), if you have the time to wait for the battery to charge.

Both the voltages I listed were with the charger disconnected. Seems that the battery voltage drops off right away after disconnecting. After sitting for two days, the voltage reading was down to 12.43.

I put in on the 8 amp setting and it has been taking a steady 4 amps. But as soon as the charger is removed, the voltage starts to drop from about 13.93 down to 12.34. So it this battery shot or what?

 

[Rocky_Road]

Re: Battery charge question

Both the voltages I listed were with the charger disconnected. Seems that the battery voltage drops off right away after disconnecting. After sitting for two days, the voltage reading was down to 12.43.

I put in on the 8 amp setting and it has been taking a steady 4 amps. But as soon as the charger is removed, the voltage starts to drop from about 13.93 down to 12.34. So it this battery shot or what?

Nope....

The most that a battery can show (off the charger, and leveled off) is 12.6 volts...6 cells (plates) at 2.1 volts per cell. That is the physical limitations of a flooded battery...period.

Your batteries are far from shot...but the only real test of their condition, will be a load test.

Any decent battery store can do the load test for you.

 

[Rocky_Road]

Re: Battery charge question

P.S. If your charger doesn't have the automatic cutoff feature, that goes into a 'float' mode, when it senses that your batteries are fully charged...and you keep charging them in an effort to raise your voltage above the 12.43 settled range...you WILL surely ruin them!

 

[mthieme]

Re: Battery charge question

You should really check your battery with a hydrometer.

 

[JB]

Re: Battery charge question

Nothing wrong with either battery or charger.

Those are 12.6volt batteries. That is the storage voltage.

When a charger is first removed there will be an additional voltage, called a capacitive charge, that will pretty quickly leak off, dropping the voltage back to the storage value.

You may charge a starting battery at any rate you choose up to about 10Amps but deep cycle batteries prefer to be charged at lower rates. . .2 to 4 Amps is common.

The true state of charge cannot be determined with a meter unless the battery is under full load, which would be a waste of energy.

The only accurate way to measure the state of charge is with a hydrometer, as mthieme says.

 

[Mark42]

Re: Battery charge question

Thanks for all the info. Batteries are not my forte. I have a hydrometer somewhere, just have to dig it out.

 

[Boatist]

Re: Battery charge question

Like everyone has said your battery voltage is very normal. Lead acid batteries each cell is 2.1 volts at 70 to 80 degrees. 2.1 volts times 6 cells is 12.6 Volts. Voltage will be a little less at lower temperatures.

As far as charging I do not feel you can use too high a amperage to charge but the charger needs to be a smart or automatic charger so it will not over charge. Also a Smart or automatic charger has a voltage regulator so the voltage is controlled and will not over charge. Most will run between 13.8 volts and 15 volts while charging. I think more damage is done by slow charging a battery that is run down. Starting batteries should not be discharged more 20 percent and deep cycle no more than 50 percent. When they are discharged damage is done and the longer they are discharged the more damage is done. So Fully Charge as soon as possible if you want your batteries to last a long time. Also use at least a 10 amp charger.

As a example My boat is a I/0 with a 65 amp alternator and it charges one deep cycle and one starting battery thru a 70 amp battery isolator. My boat is a 1980 I bought new an every battery has lasted at least 6 years. My Dad's truck and camper has a starting battery and a deep cycle and his truck has a 130 amp alternator and his batteries last over 5 years.

Best thing for battery life is to remember all lead acid batteries self discharge over time. They discharge faster in hot summer weather and slower in cold winter weather. If you use the boat or not good idea to fully charge the battery once a month in summer. In winter ever two months.

My boat is a trailer boat so One thing I do is fully charge the minute I get home. The alternator take care of the bulk charging but after I shut off the engine the radios are still on and the electronics left on sometimes. Also raise motors and trim tabs so have use some battery.

When I get home and park in the back yard I get out the battery charger and hook it up to the front of my boat where I can charge both batteries thru a battery isolator. I then unload the gear and tackle and fish. Put the gear away and clean the fish. Put the cover on then checked the battery charger and it will always be less than a half amp so disconnect and put away.

Also if you have batteries caps should check the water level once or twice a year. Keep filed to the eye with distilled water.

The eaiser you make it to charge your batteries at home or at the dock the more offten you will do it and the longer your batteries will last.

 

[Mark42]

Re: Battery charge question

Thanks for all the great info. Hopefully I can get another season or two out of this starting battery.

BTW, I was pricing marine starting batteries and they are EXPENSIVE compared to the car battery of the same cranking amps. Holy moly! Got to take better care of the batteries!

 

[Boatist]

Re: Battery charge question

Marine batteries to me are not any better than regular batteries unless there mounted up front.
I bought all my batteries from Cosco. They have 3 years free replacement then a 100 month prorated cost.
My current deep cycle if a Delco Voyager bought at Price club before they changed the name to Cosco.

Now if the battery is mounted up front where there is a lot of vibration and pounding then a marine battery may be a good idea.

Best thing you can do to keep make your batteries last a long time is fully charge as soon as possible after use. Also between uses charge once a month in summer and every 2 month in winter. Never leave in a discharged condition even for a short time.

 

[matt9923]

Re: Battery charge question

I have a automatic trice charger, a 2 am deep cycle, 10amp deep cycle
what should i use on a deep cycle trolling/starting battery? I fried a small starting battery with 10amps supposed to be 2 or less i guess.
Matt

 

[Boatist]

Re: Battery charge question

Matt
Unless your charging a small lawn mower battery or a Motorcycle battery a 10 amp automatic or smart charger will not harm the battery. Look at cars today with small starting batteries, they still have 60 to 100 amp alternators.

Any charger that is a manual charger can over charge a battery, even a 2 amp trickle.

Automatic or smart charger will regulate the charge to taper to zero or shut off completely when the battery is charged.