Duracell 215ah 6v x2

[Wabbit]

Just bought 2 of the batteries from batteriesplus(see link). When I first bought them about 2 weeks ago, I took the SG readings from each cell real quick. One of the cells seemed to be lower than the others in that battery. I ignored it and figured I take the SG again after they were charged fully.

First question, should all 3 cells in both batteries(6 cells in total)read the same or am I looking for each battery to read the same across its own cells(3 cells)?

Second question, if one of the batteries is bad, is it OK to just replace that one even if the voltages will be different when I goto charge them as a set(series) with solar? Will they balance out if one is holding a lesser charge than the other?

Hopefully that sense.

https://www.batteriesplus.com/batte...ical=9021925&gclid=CLCPzquBwtYCFZS1wAodxO4C5Q

 

[Trebor English]

If the batteries are the same brand, model, age, series connected, same load, same charging, then all 6 cells should be the same.  It is possible to put a 6 volt charger on one if necessary.  Equalizing is the process to overcharge some cells so that all cells are fully charged.  Usually that requires more charging than a typical solar installation can provide.  

If one 6 volt battery is bad it is just fine to replace that one.  The 12 volt pair will only have the amp hour capacity of the lesser of the two.  If you have a 4 year old pair, replace both.  If you have a one month old pair, replace just the bad one.  

Research equalizing.  You may be able to raise your charge controller voltage setting.  If you have a "12 volt" solar panel you might bypass the controller.  Pull fuses or disconnect things you don't want fried by high voltage charging.  While equalizing you must watch what is happening and stop charging when done or when necessary.  You must be present.  New batteries need this kind of attention as much as old batteries.

 

[Wabbit]

These batteries are new(2 weeks old). If I take one battery back to the store and replace it with same brand\ah rating. Then put it in my battery bank with the other 6 volt battery(setup in series). Can I charge that bank even though one 6 volt is at 6.37 volts and the other battery is at 6.2 volts(or whatever)?

EDIT: I don't have a 6 volt battery charger, just a 12 volt battery charger.

 

[Trebor English]

What makes you think one battery is bad?  Is it leaking, only 5 volts, specific gravity doesn't rise with charging?  

If you get a situation where "one 6 volt is at 6.37 volts and the other battery is at 6.2 volts" then you should charge them.  Ideally a 6 volt charger on the more discharged battery will bring it closer to matching the other.  A load like an old car headlight applied to the higher charged battery for 2 hours will bring them closer.  Otherwise, connect them in series and charge them.
 
Equalizing.  Make all cells be equally charged.  This is done at the full charge level.  The cells that are full first convert water to hydrogen as you continue to charge.  Eventually 5 of 6 cells are fully charged.  More charging current just makes hydrogen in those 5.  Finally the last cell is fully charged.  At that point all cells are just making hydrogen.  There is no more lead sulfate to convert to sulfuric acid and lead.  You know you are at this point when the specific gravity stops rising.  All cells bubbling does not mean you are done.

This is done to batteries that are fully charged.  They have been bulk charged, absorb charged, current tapers.  Then they are allowed to cool.  The equalizing charge must be stopped when battery temperature gets too high.

The Batteries Plus folks where you got the batteries may be able to advise.

 

[Wabbit]

I will need to get hooked into shore power. I'm trying to get this bank charged up with 100 watts solar and I don't think that's enough to get them to fully charged. My bad all around. Battery is prob fine, I took a quick SG measurement when I first got them, before any charging. And one cell seemed low.

I hate it when I think I know better than established knowledge and then it turns out I don't. Shore power it is for a few days. Have to wait till Friday for payday. Thanks Tebor!

 

[Weight]

Connect them in series. Use quality large cables with clean connection points. Then give them a good charge with a good charger. Open cell batteries will get better with a bit of use before they start a downward trend.
Are both batteries the same date? There is a sticker with a date code. If not take them back and exchange for proper set. If stickers were removed before you got them, take them back. The manufacturer is required to mark the date of manufacture on the batteries. B+B may not be that knowledgeable about those batteries. If they sat on the shelf, they could be lower voltage. But all the cells in each battery should be the same SG. One cell being lower is a bad sign. It can be difficult to get a SG measurement.

 

[Wabbit]

Yeah both same date. Will recheck SG after a full charge\equalization.

 

[Trebor English]

I searched for charging info on your batteries and came up empty.  I went to the trojanbattery page to see what they have to say.  

Trojan recommends equalizing flooded batteries (NEVER AGM or Gel batteries) only when batteries have low specific gravity, below 1.235 or wide ranging specific gravity, > 0.030 points between cells, after fully charging. Please consult Trojan Battery’s complete User’s Guide and your battery charger’s user manual for detailed instructions on equalization.  

For 2 T105s they recommend charging 14.8 and equalizing 16.2 with a max equalizing rate of RC/3 which might be 25÷3=8.3 amps.

My recommendation is, until you can get a shore power charge next weekend, to set your charge controller to 14.8 or as high as possible not over 15 at the battery.  Minimize electrical usage.  Check level and add water daily.  When some cells get charged up they will start to take water.  Maybe by the weekend things will be improved.  

One more thing to check.  When I was searching there was a user with a problem I'd never heard of.  The plates in one cell were smushed over by a tube used to water the battery.  Get a flashlight and look into each cell.  All the cells should look the same.  Use eye protection.  If you don't have splash proof glasses at least put plastic wrap over the battery while looking into cells.

 

[Weight]

This is quoted from Maine Sail. Rod does lots of research and shares his knowledge.

"The Sam's East Penn made Duracell GC2 is a Deka GC-10 with a Duracell Sticker. The Sam's EGC2 is a Deka GC-15 with a Duracell Sticker.

The recommendations from East Penn, for that battery, in a cycling / off-grid application are. (Note: floats are higher in off-grid than typical golf cart use).

At 12V:

Max Charge Current = 30% or less of Ah capacity (20 hour)

Absorption Voltage = 14.4V - 14.7V
Absorption End Point = Current change over 1 hour period of less than 0.1A
Max Absorption Time = 12 Hours

Float Voltage = 13.8V - 14.1V
Float End Time = No Limit

Equalization = 15.0V to 15.3V
Equalization End Point = Current change over 1 hour period of less than 0.1A
Max Equalization Time = 12 Hours

Temp Compensation = -.018V for every degree °C rise above 25C

Note:

For dock charging you may want to compensate float down to 13.4V to 13.6V the guidance above is for off-grid or deep cycling applications where the batteries are cycled daily.

Stick to the 14.7V end of the absorption range and the batteries will do much better if they are cycled while cruising. "