Battery Questions/run time!!!

[06madaman]

Guys I have a question about run time and pack voltage. First, I have a 2008 RXV Freedom. Batteries are from 7/17, I bought them new. I have had no issues driving my cart 8-9 miles round trip with my factory SOC meter always staying at “full”. Cart is driven weekly to kids football games, dinner. My run time has significantly diminished. I have to admit, I missed a month of checking on water and had to add about half gallon across all batteries. After my wife limped home one day. Since then I have ran the cart only 3-4 miles with voltage dropping faster than normal. The attached photo has the volts per battery after 30min resting after charge.

Battery 1= 13.0v
Battery 2= 12.8v
Battery 3= 12.8v
Battery 4= 13.0v
Total pack= 51.6v

Have I caused damage? And why is my run time shorter? The only variable is the new digital soc meter from eBay... Any tips or info would be great

[usgicollector]

You really need to fully charge your batteries and put a dvm on your battery pack. But first get a reading of each battery and record it. Take a ride and watch the dvm and see what voltage it is reading. Make that ride at least 3-4 miles. Get a reading of the pack and of each battery right now after the ride. Then let the cart sit for about 15 minutes and get a reading of the pack and each battery again. Come back and tell us what you got.

[06madaman]

Originally Posted by usgicollector

You really need to fully charge your batteries and put a dvm on your battery pack. But first get a reading of each battery and record it. Take a ride and watch the dvm and see what voltage it is reading. Make that ride at least 3-4 miles. Get a reading of the pack and of each battery right now after the ride. Then let the cart sit for about 15 minutes and get a reading of the pack and each battery again. Come back and tell us what you got.

The individual battery voltages were from tonight after it was done charging. I’m going to Ft.Wilderness Thursday. I can get those numbers and report back. Thank you!

[06madaman]

Ok, finally got around to taking the cart for a 5 mile ride. Prior to leaving, after charging cart overnight (keeping it plugged in) and taking it out this morning I have some worries. 50.3v after just unplugging it from Charger. Then, 5min later we left the drive way and it was at 50.1v. Drive for 5 miles. Get home, 48.7v. Let rest for 15min, 49.5v. I forgot to take individual battery voltage before we left. But, I did after getting back and resting. If you go by the previous image in this post on battery numbers: battery 1, 12.4v battery 2, 12.2 battery 3 12.2 battery 4, 12.4. I have a powerwise qe charger. Is it working properly? If you look at my initial post almost a month ago, battery volts were a lot higher. Is it normal for the two “middle” 12v batteries to be a bit lower than the pack + and - batteries? Batteries are full with water as well. Any help would be appreciated.

[Cobra,1]

Have you tried back to back charges. Fact you had to add that much water to batteries may take a few charge cycles to bring them back up assuming you did’nt damage them when low on water.

[JohnnieB]

There are three separate battery voltage measurements, each taken at different times and under specific conditions; And each has a significance in estimating the health of the batteries and charger.

At-Rest: This voltage is measured approximately 12 to 24 hours after the charging cycle terminates (charger shuts off) and is used for SoC estimations.

Can also be measured about an hour after the cart stops and discharging ceases.

In-Use (aka Under-Load): The battery voltage drops significantly and rapidly when amps are drawn from it. About 1V/100A for a 36V battery pack, about 1.25V/100A for a 42V pack and about 1.5V/100A for a 48V pack.

In addition there is the voltage drop caused by the resistance of the high current cables, contacts and connections, which, depending on the health of the high current circuit, can be as much. or more than the voltage loss of the batteries in and of themselves.

However, the voltage drop due to the resistance in the high current circuit disappears the instant the amps stop flowing while it take the batteries an hour or more to return to the At-Rest voltage.

On-Charge: The battery's voltage while a charging current is passing through it.

The lowest On-Charge voltage is measured the moment the charging current starts to flow. Many golf cart battery chargers have to see at least 1.5VPC to turn on, but others will will turn on regardless of battery voltage.

The highest On-charge voltage is measured the moment the charging current ceases to flow. The maximum On-Charge voltage reached depends on the charger design.

Legacy designs like the ferroresonant transformer types shut off when the On-Charge voltage climbs to a predetermined voltage that is thought to be high enough to adequately charge newer batteries without being high enough to overcharge older batteries. Typically this is 2.5VPC.

Modern designs use dV/dT (change in Voltage over change in Time) technology to terminate the charge cycle. Technically, a lead-acid battery is not fully charged until the Specific Gravity of the electrolyte ceases to increase while there is a charging current passing through it. Since the battery's On-Charge voltage tracks the ON-Charge Specific Gravity of the electrolyte, it can be inferred that a lead-acid battery isn't fully charged until the On-Charge voltage ceases to increase with a charging current passing through the battery. The size and cost of the electronics needed to shut off a charger with dV/dT have came down enough to make using it feasible in consumer grade chargers.

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What are the At-Rest voltages for you 48V battery pack and individual batteries?

[06madaman]

Originally Posted by JohnnieB

There are three separate battery voltage measurements, each taken at different times and under specific conditions; And each has a significance in estimating the health of the batteries and charger.

At-Rest: This voltage is measured approximately 12 to 24 hours after the charging cycle terminates (charger shuts off) and is used for SoC estimations.

Can also be measured about an hour after the cart stops and discharging ceases.

In-Use (aka Under-Load): The battery voltage drops significantly and rapidly when amps are drawn from it. About 1V/100A for a 36V battery pack, about 1.25V/100A for a 42V pack and about 1.5V/100A for a 48V pack.

In addition there is the voltage drop caused by the resistance of the high current cables, contacts and connections, which, depending on the health of the high current circuit, can be as much. or more than the voltage loss of the batteries in and of themselves.

However, the voltage drop due to the resistance in the high current circuit disappears the instant the amps stop flowing while it take the batteries an hour or more to return to the At-Rest voltage.

On-Charge: The battery's voltage while a charging current is passing through it.

The lowest On-Charge voltage is measured the moment the charging current starts to flow. Many golf cart battery chargers have to see at least 1.5VPC to turn on, but others will will turn on regardless of battery voltage.

The highest On-charge voltage is measured the moment the charging current ceases to flow. The maximum On-Charge voltage reached depends on the charger design.

Legacy designs like the ferroresonant transformer types shut off when the On-Charge voltage climbs to a predetermined voltage that is thought to be high enough to adequately charge newer batteries without being high enough to overcharge older batteries. Typically this is 2.5VPC.

Modern designs use dV/dT (change in Voltage over change in Time) technology to terminate the charge cycle. Technically, a lead-acid battery is not fully charged until the Specific Gravity of the electrolyte ceases to increase while there is a charging current passing through it. Since the battery's On-Charge voltage tracks the ON-Charge Specific Gravity of the electrolyte, it can be inferred that a lead-acid battery isn't fully charged until the On-Charge voltage ceases to increase with a charging current passing through the battery. The size and cost of the electronics needed to shut off a charger with dV/dT have came down enough to make using it feasible in consumer grade chargers.

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What are the At-Rest voltages for you 48V battery pack and individual batteries?

50.6 for pack
12.7 “positive battery”
12.5
12.5
12.7 “negative battery”

Not sure why the total pack voltage don’t equal the sum of all individual battery volts.. also, it has been “colder” for our Florida weather. Lol. I know the heat/cold affect the pack.

[yurtle]

Originally Posted by 06madaman

50.6 for pack
12.7 “positive battery”
12.5
12.5
12.7 “negative battery”

Not sure why the total pack voltage don’t equal the sum of all individual battery volts.. also, it has been “colder” for our Florida weather. Lol. I know the heat/cold affect the pack.

They should, likely a rounding error.

Do you have access to a 12 volt car charger? You should really try and get those two 12.5 volt batteries up to 100% SOC. Do you have a handheld digital multimeter (DMM or DVM)? It's best to know an individual battery's voltage to two decimal places. 12.50 is only 80% SOC. They really shouldn't stay that low. As to the imbalance, mine are 6 volts, but all eight are within a couple of hundredths of a volt from each other. They always have been since I got them 11/11/11.

[06madaman]

Alright, DVM says:
12.77 “positive” battery
12.55
12.57
12.76 “negative” battery

50.65 total

I do have an automatic 12v car charger, should I leave it charging on individual low batteries till full? Settings on charger are 2amp, 10amp, 30amp. Any preference? What would cause charging imbalance?

[yurtle]

Are these readings 12 to 24 hours after charge completion? 12.77 and 12.76 sound too high. If the readings are less than 12 hours after charge is complete, all four will likely go down.

Based on the attached, I'd pick 2 amps. that might be too low, but since this is a one time deal (hopefully). I'd try and get each one to 12.73 after they've been off charge for 12 hours. May be an iterative process. Once they are within one tenth of a volt from each other, I'd do several back to back charges, then report back. May take a while if you work.

As to why the imbalance? I haven't a clue. Are they all the exact same age, month and year? Do you have anything connected to one or more, besides the interconnecting cables (lights, radio)? Check water levels and only use distilled water. Not tap, or "bottled" or "purified" or... You should have been charging them every time you drive, even if it's only a short trip. Never let them sit partially discharged or you will permanently reduce your run time and useful life.