Is 12.4 Volts on a Deep Cycle Battery Acceptable?

stopngo

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Hell Y'all. Hope I posted in the correct area.

I bought my 12 v Deep Cycle battery about 18 months ago and have used it a few times on my trolling motor and have always kept it charged even when not in use.

It does not charge higher than 12.6 V and within 1 hour of disconnecting the charger it reduces to 12.4 V. Does this seem Defective to you all??

Thanks in advance.
 

bruceb58

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Have you ever let it completely discharge?

What type of meter are you using? If it's a cheap Harbor Freight one or similar, I wouldn't trust it.

12.4V means it is at 80% capacity or slightly less.
 

CraigBarnard

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My understanding is a batteries standing voltage if fully charged is 12.5V so i would think .1 of a volt isnt much to worry about.
 

hemi rt

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On a lead/acid battery, each cell - fully charged has 2.25 volts so a fully charged battery should be at 13.5 volts. Now the big question is what type of charger are you using? Output - charge rate etc.; how long are you charging it for? Deep cycle batteries take a lot longer to charge than a normal battery and at a lower charge rate.
 

stopngo

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First of all thanks to all.
" Now the big question is what type of charger are you using?"
Not sure how to describe it accurately but it is the same charger (the one that came with the trolling motor) that charges my other regular 12 battery to just over 13 volts which after an hour settles and holds at 12.8

"Output - charge rate etc.; how long are you charging it for? Deep cycle batteries take a lot longer to charge than a normal battery and at a lower charge rate."

I always use 2 Amp trickle charge and there is a green light that comes on when fully charged so I think I am comparing apples to apples here.

As to the question of letting it completely discharge I am a bit foggy on that.
 

bruceb58

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On a lead/acid battery, each cell - fully charged has 2.25 volts
That is not correct. Cell voltage for a fully charged batter is approximately 2.12V for a total of 12.7V

A trickle charger is a poor way to charge a battery. You really want a 3 stage charger.

If you had a true deep discharge battery like a Trojan battery, their recommended charge rate is betwen 10-13% of its 20 hour capacity. For a large Trojan battery, that would mean between 20A and 30A.

What type and brand of battery do you have? Is it one of those Marine batteries which is really a hybrid?

Here is a chart that shows battery voltage vs % discharge, You never want to discharge your battery past 50%.

battery.png
 
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stopngo

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"A trickle charger is a poor way to charge a battery. You really want a 3 stage charger."

I need to stress here that I am using the same charger for the two batteries I am comparing. So I am not quite understanding re quality or type of charger.

One battery charges up and holds the charge......the other does not.
 

fhhuber

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"nominal" voltage of a battery is a good time to be putting the battery on the charger... but you aren't hurting it yet.

A float charger keeping it about halfway between nominal and peak isn't hurting anything. Very conservative setting for preventing damage.
 

stopngo

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Bed Time for me. Will answer a few of your questions tomorrow. Thanks Y'all
 

stopngo

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Here are the Specifics of the Charger

Minn Kota Mod MK 105 P..........1 Bank .5 Amp......Output 12 VDC 5 Amps

When the green light comes on (fully charged) the better battery shows 13.06 immediately after disconnect and is at 12.8 in the next hour

The questionable battery (green light on) shows 12.95 (not 12.6 as I erroneously stated earlier) after disconnect but goes to 12.4 in next hour.
 

bruceb58

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That's a lot better charger than I thought you had. Not a 3 stage but better than just a trickle charger.

When you take a battery off of a charger, you need to let it set for 30 minutes to measure it so that the surface charge dissipates.

EDIT: it helps if I actually read your post. Does sound like that battery has an issue.
 

stopngo

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Totally bewildered now.

A.......Decided to run the Battery right down all the way and then Charge from square one to see if it accepts a higher full charge and holds higher than 12.4.

B......Ran motor in garbage can full of water (just to simulate load on propeller) and it went for 4.5 hours at #4 speed setting.

C......Connected Charger Positive lead to positive Battery and Negative to negative (no brainer)

D......PROBLEM........Red Light comes on indicating Check connection which means incorrect polarity.

E......Reversed polarity momentarily......Red Light again. What now???
 

bruceb58

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Never ever run the battery all the way down. Worst thing you can do for a lead acid battery . Only run it down until it gets to 12.0V and stop discharging at that point.

The problem now is that the battery probably has such low voltage that the charger issues a fault. Many chargers will do that. What is your battery voltage now?
 

stopngo

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"What is your battery voltage now? " Battery is on charger. At the moment 12.25

"
"Only run it down until it gets to 12.0V" Since it only charges up to 12.4 I would think fishing would have to be pretty good to adhere to that....No??

I thought the whole idea of Deep Cycle batteries was that they tolerate multiple discharges.
 

bruceb58

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I thought the whole idea of Deep Cycle batteries was that they tolerate multiple discharges.
Yes...50% is considered a deep discharge. If you go below that multiple times, you severely reduce the subsequent capacity of the battery.

A battery that is discharged 50% each time will last twice as long as one that is discharged 80%.

Which brand and model battery do you have? If its one of those marine batteries you buy from Costco or Walmart, deep discharge of those is even worse.

"What is your battery voltage now? " Battery is on charger. At the moment 12.25
Battery voltage off the charger for more than 30 minutes. Voltage on the charger doesn't mean much.

If you have a true deep discharge battery like a Trojane, this chart explains the life
6v-12v-deep-cycle-battery-cycles-vs-life.jpg
 
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