Higher Than Expected Voltage on Charger

[carbon60]

So I finally installed a permanent voltmeter into my truck, so I can keep an eye on my battery bank. (The very expensive but super nice Blue Sea 1733.)

Yesterday morning, about 22 hours ago, I hooked up a Noco G7200 (previous generation) battery charger to the two-battery 12v starter bank, and enjoyed watching the voltage slowly climb. Went out this morning, and noticed the following:

• The charger was blinking the 100% indicator, meaning it was almost fully charged, which seems odd since it has been around 22 hours.
• The voltmeter showed 13.96v, which seems really high.
• Unpluged the charger, replugged the charger: it now thinks the bank is fully charged, meaning that it should be maintenance/trickle mode.
• Voltage floated back down and is stable at 13.05v.

Does that seem right to all of you?

Going to go measure the specific gravity.

 

[carbon60]

Just went out again and measured the specific gravity at 1.235 or so. Which seems low.

And the voltage has floated down to 12.85v.

I'm confused.

 

[DLTooley]

What's the history of your batteries?

I'm by no means expert but it sounds like the batteries may be failing. Do keep them on the trickle charge for a while, maybe a month, and see how they respond. Running an equalization cycle and checking water before and after would probably be worth a try. Again, I'm not an expert on these specifics.

 

[DLTooley]

I just did a bit of research on those numbers. Please feel free to check my numbers. Float/trickle voltages are typically 13.8v for Flooded Lead Acid. It is normal for voltages to run a bit high after charging and they will ease. According to Battery School your specific gravity says the resting voltage should 12.45. Give it a full day off the charger and measure volts again. If you are fully charged, that means you have 80% capacity left. Again, let it rest on the trickle charger and run an equalization cycle. You might also run an actual capacity test, seeing how much wattage you actually get out of the battery.

http://www.batteriesnorthwest.com/batteryschool.cfm?TID=5

 

[carbon60]

These batteries were installed new in January, and are cheap flooded Group 27s.

I can't really do the suggested tests as I live in this truck, commute to work with it, and have a fridge.

Happy to hear that the high voltage on the charger is normal, though.

Thanks guys,

A.

 

[john61ct]

Most quality lead batts require an Absorb setpoint at 14.6V or higher.

A deep cycle batt say 50% depleted will take 5-7 hours, assuming a high-current charger, like 25-60A.

13.x is a Float setpoint, only suitable for maintaining a battery that's already full.

 

[john61ct]

Most quality lead batts require an Absorb setpoint at 14.6V or higher.

A deep cycle batt say 50% depleted will take 5-7 hours, assuming a high-current charger, like 25-60A.

13.x is a Float setpoint, only suitable for maintaining a battery that's already full.

 

[luthj]

Most chargers use an voltage only algorithm. The 12.8V open circuit voltage combined with the rapid rise to the chargers set voltage makes it think its full. Given your specific gravity your batteries are probably not fully charged. Are the batteries very far from 75F? If so the hydrometer may be off a bit due to temperature drift.

Given these are flooded batteries, they may be equalized. If the SG remains low after 4 hours at the absorb setpoint (14.6v), they may need an equalize/condition charge. This is generally about 15.5V, and can last 2-8 hours. This will help to recover a sulfated battery.

 

[john61ct]

All depends on what batts you have, get the charge specs from the mfg and ensure charger follows them.

Adjustable profiles are best

 

[carbon60]

All depends on what batts you have, get the charge specs from the mfg and ensure charger follows them.

Adjustable profiles are best

Yeah, except that these cheap starter batteries have no such customer service.

 

[carbon60]

Do you guys think the the intermittent current draw of the fridge would cause the "smart" charger to get confused?

 

[john61ct]

No

 

[mezmochill]

Dont know if this has been asked, but are ALL your connectiins rock solid and have a clean solid grounds?

 

[carbon60]

Dont know if this has been asked, but are ALL your connectiins rock solid and have a clean solid grounds?

I believe so, but that reminds me that I should be cross-checking this new panel voltmeter against a meter at the battery posts. Will do that!