New U1 Battery: 12.7V Max Charge

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Purchased a new U1 flooded garden tractor battery, supposedly 350 CCA. Store had a bunch on prominent display. No date of manufacture stamp. DMM displayed 12.24V directly from store (maybe 65-70°F). Placed on 12V/2A manual charger for 8 hours. Battery was just slightly warm when I checked a few hours into the charge session, but cooled before the 8-hour session was complete. 12.9V immediately after charging; 12.7V the next day. Seems to attain maximum of 12.68V after some use and subsequent charge/rest/check, at about 80°F. Loses maybe 0.02V per day.

Would any effects of sulfation, from sitting at low charge in the store, show up now, as diminished voltage capacity, or only later, as diminished battery life?

Any recommended break-in procedure? E.g. place load to lower to 12.5V, then recharge to full? Have seen this mentioned.

What are your opinions or general assessment? Likely good battery? Should I expect higher resting voltage from this new battery? Battery has a warranty, but I'm not sure how store determines whether to replace. What criteria should I use to determine whether to request a replacement before the warranty period ends?
 
Sulfation on the plates reduces capacity and the maximum current. As the plates shed the sulfation in fine particles, it accumulates on the bottom and eventually shorts things out.

If it was me I would give it a good discharge to under 11v and slow 2 day recharge.
 
Doesn't seem like you have fully charged the battery as of yet. When first removed from the charger the voltage should be well over 13.5 volts.
I would charge the battery slowly at around 0.5 amps for at least a day or more. To bring the charging amps down low you could put a resistor in line with the charger leads. A 12 volt light bulb can do this if you have a tail light bulb with socket or something similar.
Having a multimeter that measures current would help.
 
Keep a battery tender on it, when not in use. Have you checked the electrolyte level? If it’s low, top up with distilled water.
 
Would any effects of sulfation, from sitting at low charge in the store, show up now, as diminished voltage capacity, or only later, as diminished battery life?
Sure will. Which is why batteries are sold with more capacity, and sufficiently low impedance, that it doesn’t matter. Even with a reasonable amount of time at low voltage (store should have put a charge on and not let it get to 12.24v), it should still make nameplate capacity.

Since you have no calibrated way to pull a set amount of Ah out, capacity is tough. I’d discharge it and charge it again. You want to see >14v while charging. There’s gobs more info out there about charging batteries, but at minimum I’d want some assurance that the charger is doing the job right.
 
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If it was me I would give it a good discharge to under 11v and slow 2 day recharge.

Is this recommended for all new batteries? 11V seems severely discharged. Is there a danger of reducing longevity by doing this? Is it necessary to go this low, is it preferred, even? How to dscharge? Just leave garden tractor lights on?

WobblyElvis: "I would charge the battery slowly at around 0.5 amps for at least a day or more. To bring the charging amps down low you could put a resistor in line with the charger leads."

Just attach the bulb leads to charger terminals along with battery? I have a 15V/350mA wall wart. Would that work instead? Would take over 5 days to charge from 0% at this rate, according to my charger manual.

wpod: "What is the date code on the battery?"

As I said in original post, "No date of manufacture stamp."

MParr: "Keep a battery tender on it, when not in use. Have you checked the electrolyte level? If it’s low, top up with distilled water."

No, it doesn't have screw caps. I may be able to pry off part of the top, but I'm not sure this is intended. Looks the top may be a 6-in-1 cap, but I'd have to try prying to find out. Would periodic charging be as good as using a maintainer?

JHZR2: "Sure will. ... I’d discharge it and charge it again."

Sure will ... which result? Diminished voltage capacity, diminished life, or both? Discharge to which voltage level? 11V?
 
JHZR2: "Sure will. ... I’d discharge it and charge it again."

Sure will ... which result? Diminished voltage capacity, diminished life, or both? Discharge to which voltage level? 11V?
I don’t know what “diminished voltage capacity” is. These are electrochemical systems, the voltage means something.

I also don’t know what diminishes life is. Since you have no way to measure impedance or ampere hours of the battery, there is no reliable metric that is data driven. Then eat you can hope for is to condemn it when cranking voltage drops too low. If you had real data you might condemn when the battery is at 80% capacity, or impedance doubles. Now life is dependent upon calendar ageing, subsequent abuse, etc. worry less about the past. As I mentioned, the batteries are produced with more capacity than nameplate so you’re probably still good relative to that. Now what matters is if it can crank the engine for the next x years.

The amount you discharge isn’t particularly important. What you want to do is get it off full charge and work the plates a bit. I’d probably argue a 1C discharge for 30-45 minutes would be good.
 
If you can't get it up to the mid 14s when on trickle charge the battery is damaged.

Is 12V/2A considered trickle charge? That's what my charger provides, and I've seen it provide 13.1V during a charge session, but not sure how this varies as the battery accepts a charge. Should I check for mid 14s toward the end of the session?

So, to summarize, have a relatively new battery that charges to 12.7V. The recommendation is that I discharge it a bit, then recharge. My only available way to discharge is to turn on the headlights with the engine off. I don't know if turning on the headlights will discharge the battery at a rate of 1C, as per a suggestion above. Anyway, let's say I turn on the headlights for 45 minutes (is that about right?). At this point voltage should be ... ??? I can then recharge at 12V/2A, as my charger allows, or preferably, connect a 12V lightbulb to the charging terminals along with the battery to reduce the current going to the battery. Charge for several hours until ... ???

Is this correct? What result can I expect to achieve by doing this?
 
No it should maintain 14.5v (once charged) with minimal amperage input, 1/4 amp or less. Depends on the plate chemistry actually. Any gas bubbling is excess current.

With only a 2A max input it may take a couple of days or more to reach your terminal voltage. 2A x 24 hr = 48 Ah.
 
No need to discharge a lead acid battery for maintenance. That does more harm than good.

The fact that your battery settles to 12.68 after resting for a day or two tells me that it is likely in good shape. If you don't use it for more than a few weeks it would be beneficial to put a battery tender on it, but just make sure that it doesn't charge with more than 13.2v to 13.6v continuously after it's full or it will over charge.

This article should fill in all the blanks.
 
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