New T105 Battery Voltages differences different code dates

[radioman]

I purchased a new set of six T105 batteries a few days ago. Three have code date L6 (Dec 2016 and three have C7 (Mar 2017. After several charge cycles and letting set over 12 hours I made the following voltage measurements. The three L6 batteries measured 6.38 volts each. Two of the C7 measured 6.57 volts each and the other C7 6.49 volts. The total pack voltage measured 38.76 volts. Is these slight cell voltage differences going to cause problems later or is everything OK.

[JohnnieB]

The three L6 batteries have been sitting on a shelf four months longer than the C7 batteries, so they self-discharged further before the initial charge you gave them.

I'd use a 6V charger on the four lower voltage ones to bring the voltage up as much as possible. If you can get all of the within 0.1V of the others, great.

If you are using one of the old ferroresonant transformer type chargers the shuts of at about 45V, the voltage spread will grow wider with time and use. If you have a modern charger that uses dV/dT, the spread will narrow.

[yurtle]

Two in series will allow you to use a 12 volt charger.

[radioman]

Thanks JB and yurtle. I connected a 12v charger across two adjacent L6 batteries in series and a lone 6v charger on the other L6. Will leave them charging overnight. I will let you all know how it turns out in a few days after I do some more measurements after several more charge cycles after normal daily use.

[rib33024]

How many amps is the 6 and 12v chargers

[radioman]

Originally Posted by rib33024

How many amps is the 6 and 12v chargers

The 12 volt charger connected to the two 6 volt batteries in series is rated at 8 amp charging @2 amps. The 6 volt charger is rated at 6 amps charging at about 1 amp. The 6 volt is an old NAPA 6/12 charger about 50 years old. I plan to leave the 1 amp charger on twice as long on the single battery than the two batteries on the 2 amp rate charger. Let them set about 12 hours and check the voltages again.

[radioman]

After charging the lower voltage batteries individually for about 8 hours and running cart about 30 minutes I put cart back on charge. I checked each individual battery this morning after 12 hours and it was exactly the same as in my first post. There was no improvement in the battery voltage differences of the L6 and C7 dated batteries. The batteries work fine. I'll just keep checking them from time to time. By the way my charger is an old powerwise industrial model. I checked the terminal voltage of batteries at 46.5 volts as the charger was topping off charge. Voltage of batteries varied 7.66-7.83 while charger was cut back to several amps, the most voltage difference was between two of the C7 date batteries. None of this makes sense to me. No rhyme or reason. I will just quit worrying about it. I wish I had never checked the voltages. I will just continue watering them as necessary with rain water collected from only the most severe thunder storms.

[radioman]

Update: Checked the voltages on new T105 batteries after a month in service. The three code date C7 batteries with the slightly higher voltage (2@6.57-1@6.49 volts) has not changed. The three code date L6 lower voltage batteries increased .03 volts from 6.38 to 6.41 volts.

[orangeman6]

That's good that they've come up some. I'm anxious to hear what guys think about the voltage spread now. Should radioman keep trying to bring them up with a 6 or 12v charger? What spread in voltages would we call acceptable?

Another question, and sorry to hijack: is there a standard expectation of date code similarities when purchasing new batteries? Should I take a dvm with me and check voltages as well, when getting new ones?

[JohnnieB]

The spread has gone from 0.19V to 0.16V in a bit over three weeks, so whatever radioman is doing, I'd keep doing it until no more improvement is seen.

There is not standard expectation on date codes that I know off, other than trying to get them as close as possible and as new as recent as possible.

Take a DVM with you.