Battery Mystery

[2ndwish]

We purchased a pair of Group 27 Lead Acids ( Ever Start Marine)from Walmart over the summer. The batteries are rated to 105 AH and 750 MCA. For a house bank we don't really care about MCA. About a month ago we were out for a daysail, switched the fridge on and two hours later the batteries were reading 12.3 V. I had not had the AH meter set up, ut even with 5 A for 2 hours, we should have used 10 AH on a 210 AH bank...hard to imagine them getting drawn down to 12.3 V.

I suspected the charger, but checked back at the dock and our charger is fine. Pulled the batteries and took them back to Walmart expecting to get a replacement under the 1 year warranty. They put the batteries on their (Midtronics?) tester which showed 700 MCA still on the battery. MCA or CCA is apparently their criterion for "good" or "bad". They then put them on a rapid charger and retested on a different machine. This time they got 850 MCA, but I noticed on the printout, the fully charged battery was only at 12.4 V (the second was at 12.48). I tried to explain to them that 12.4 V is very low for a fully charged battery and they would have none of it . I left rather annoyed and returned to the boat.

I checked the batteries back at the boat with my voltmeter and they were 12.4 V as the printout said. I also checked my starting battery which is charged off of the same charger and it was sitting (after being off for several hours) at 13.1 V. Reinstalled the batteries and the ammeter confirmed that they were indeed fully charged. Assuming that the batteries were bad and had little remaining capacity, I set out to prove it. Reset the AH meter and left the boat on house bank for 24 hours running the fridge and some other things . Within a few minutes the voltage dropped to 12.3. The next morning 12.2V (28 AH used) and 24 hours 12.18 (55 AH used). If I were to extend this curve, I believe the available AH might be about 105 per battery (assuming 11.7 V is >50% drawn down).

I have not heard of a battery which sits low like that. It might be consistent with a bad cell, but it seems unlikely (but not impossible) that both batteries in the bank have a bad cell (both topped out at <12.5V when independently charged). Also, the behavior seems different than when we installed the batteries. During a cruise over summer, they never dropped below 12.3 V with much more usage. Could temperature be a factor? Also, if they are bad, how does one get the vendor to accept they are bad when the symptom does not cause a failing grade in MCA, which is what they evaluate (this is really a problem for boaters since deep cycle batteries are not particularly concerned with cranking amps.)? 

Sorry for the long-winded post, but I can't stand an unsolved mystery.     

[Clay Greene]

What happened to the voltage when you turned off the refrigerator and other items drawing power?  Did it bounce back up over the next hour or so? 

I assume that these are flooded batteries and the water levels were fine.  Did you try measuring the specific gravity in each one of the cells to determine if you had a bad cell?

 

[Clay Greene]

You might also check this out regarding the process of "breaking in" new flooded batteries:

http://c34.org/bbs/index.php/topic,6353.0.html

[Ron Hill]

2nd : Look in WiKi and find the Voltage reading/Approx state of charge graph that I posted.

For flooded batteries 12.75v is approx. 100% charge.  /  12.4v is 65% charge  /  11.75v is 00% charge
(after 24 hrs of no charge or discharge)

A thought

[mainesail]

Two words...

RESTING VOLTAGE

Loaded voltages tell you little to NOTHING unless you have previously graphed it out, which is very, very time consuming to do..

A 24 hour resting voltage, especially if the batteries are below 70F,  is all that matters. That said these batteries simply do not sound broken in.... Give them some more deep cycles and I suspect you will see them hold voltage a little better.

Just to refresh you can NOT tell SOC looking at the voltage from a LOADED battery....

How has it been determined the battery charge is fine?

How long had the batteries been on-charge before hitting Wal*Mart?

What is the absorption charging voltage?

[2ndwish]

How has it been determined the battery charge is fine?

How long had the batteries been on-charge before hitting Wal*Mart?

What is the absorption charging voltage?

Thanks for the quick replies.

The batteries had been on the charger (for a week) when I pulled them. Charge current was 0 A at set point 13.7 V. When I got them to Walmart, they put them on a rapid charger. I got them back to the boat 1-2 hours later and measured the 12.4 V for the resting (for the 1-2 hours) unloaded battery. By the same token, the starting battery, also a Group 27 lead acid which had been on the boat charger (separate output) and resting for 3 hours was 13.1 V. I put the batteries back on the boat charger and they drew 0A at 13.7 V which told me they were charged to their capacity whatever that might be. Our charger is a single stage charger (lewco). It current limits at 5 A and max voltage is 13.7V. It is certainly possible that the batteries are not broken in, but the surprising thing is the low "resting" voltage, which is not fully accurate since it didn't sit 24 hours. This weekend I'll let them sit for 24 hours and check again. If they remain low, I'll deep discharge them and recharge and see what happens.

[mainesail]

FLA batteries really a good gassing voltage to fully recharge and limit the effects of sulfation. The results are not surprising with your voltage so low. That low charge voltage is going to kill your batts over time and lead to short life.. You are due for a good smart charger. Reaching a good absorption voltage matters to the longevity of the bank.....

When you get a good marine charger your fist step should be to check the SG and then equalize.....

[Roc]

Speaking of equalization, what is the procedure for doing this?  I have a Xantrex True Charge 40 that I got several years ago (it's been working fine, it's probably made before Xantrex went downhill)...  It has an equalization button but I've never used it.  I've been always afraid of creating an explosive condition so I've always shied away from doing this.  I have the 4 golf cart battery set up.....  would appreciate any thoughts on this.

Thanks!

[Jim Hardesty]

Some good information here for battery maintenance that I never knew about.  Some of it is for Rolls batteries, but was real helpful to me.

http://support.rollsbattery.com/support/solutions

Hope it helps.
Jim

[Stu Jackson]

Speaking of equalization, what is the procedure for doing this?  I have a Xantrex True Charge 40 that I got several years ago (it's been working fine, it's probably made before Xantrex went downhill)...  It has an equalization button but I've never used it.  I've been always afraid of creating an explosive condition so I've always shied away from doing this.  I have the 4 golf cart battery set up.....  would appreciate any thoughts on this.

Roc, it's a controlled charge at 15+ volts at low amperage.

http://batteryuniversity.com/learn/article/equalizing_charge

Trojan also has a writeup on their webpage.

It's part of battery maintenance, but check first if your golf carts are OK with it with the Trojan website.

Explosive?  Open the hatches, and BE THERE. It should take about 2 to 4 hours.  Maine Sail recommends doing each battery individually, so you'd have to do two at a time with 6 Vs.

[Clay Greene]

Xantrex has a pretty good description of the equalization process in the manual for the True Charge:

http://www.xantrex.com/documents/Battery-Chargers/TRUECharge-2/3G%20TC2%20Manual.pdf

[sailaway]

I would look at your amp draw. Maybe your fridge is low on freeon and running all the time. I own walmart everstart marine deep cycle group 27 that are 7 yrs old. Every Ohio winter I fully charge them then unhook just the neg leds. In the spring I read them with a meter. Two reads 12.5v and one reads 12.4 every year I don't know why.

[tonywright]

Jim, The Rolls info is pretty good, except for this bit:  "If the batteries become discharged, the electrolyte can freeze when stored below +20° F (70° C)``....;-)

[Jim Hardesty]

The translation to Canadian was wrong.  Eh
Best Wishes,
Jim