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Old 05-09-2018, 09:59 AM   #1
Orville12
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Default battery tests for deep cycle batteries

I read where after doing voltage and hydrometer tests on golf cart batteries a load test should be done if batteries appear to be a problem. My question is that I thought load tests are done more for car batteries than deep cycle. Do you use the same type of meter? for this test? My problem is that my batteries on an RXV 48 volt EZGo cart read 12.5 for 3 batteries and 12.25 for one battery for hydrometer and approx. 12.60 for 3 batteries and 12.5 for one battery on voltmeter 24 hrs. after a charge. The charge rate was 12.9 to 13.9 so initially the volt reading right after charge considerably higher than after the 24 hrs. The group voltage after 24 hrs. was 49.9 as well the group charge was 50.9 immediately after charge. However my problem is the golf cart will not complete 18 holes before it runs out of power. The voltage of each battery continues to drop and about the 16 hole power is gone. Our course is flat with no hills. What kind of result should I expect from a load test? What may be the problem as batteries are also only one year old? Thanks for the help or ideas. Batteries are crown 1275 or BCI 1275 CR GC 150
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Old 05-09-2018, 10:14 AM   #2
radioman
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Default Re: battery tests for deep cycle batteries

A load test will probably give you the same as a 16 hole run. Your batteries are probably shot.
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Old 05-09-2018, 10:18 AM   #3
usgicollector
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Default Re: battery tests for deep cycle batteries

You could have a bad cell or two. Measure each battery after it starts slowing down and report it back here.
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Old 05-09-2018, 10:44 AM   #4
JohnnieB
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Default Re: battery tests for deep cycle batteries

If the 12.50V and 12.25V readings were taken after about 12 hours of rest (no charging or discharging), then three batteries are about 80% charged and one is about 65% charged, so the cart won't travel very far.

The battery with the lowest voltage is likely to be the one that powers the 12V accessories. Using a 48V to 12V converter is a much better way to power the 12V accessories since doing so doesn't imbalance the battery pack and shorten the lifespan of the batteries.

How often are the batteries charged?
How fully charged were they kept over the winter months?

Looks like your 1 year old batteries are at the end of their usable lifespan.
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Old 05-09-2018, 04:41 PM   #5
WalterM6
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Default Re: battery tests for deep cycle batteries

Do your batteries constantly look wet on top. I had a set that did and after a year they were gone. Bottom line is they leak.
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Old 05-09-2018, 08:50 PM   #6
Orville12
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Default Re: battery tests for deep cycle batteries

JohnnieB Point of clarification the hydrometer tests are 1.25 (1250) which is just in white for 3 batteries and 1.225 (1225) for other one.
No moisture on battery and no corrosion.
Voltage reading on batteries golf played today
Started and measured every 2-3 holes 12.64 12.66 12.65 12.59
12.59 12.60 12.60 12.54
12.51 12.51 12.52 12.46
12.42 12.43 12.43 12.39
12.34 12.35 12.35 12.30
12.29 12.28 12.28 12.24

Stopped on 16 hole
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Old 05-09-2018, 09:00 PM   #7
Orville12
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Default Re: battery tests for deep cycle batteries

Wanted to add that measured after coming immediately off charge batteries
read 13.40 13.32 13.43 13.10

shortly after 12.90 12.90 12.90 12.84

after 24-48 hrs they would be in 12.50 to 12.65 range before next use
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Old 05-10-2018, 11:11 AM   #8
JohnnieB
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Default Re: battery tests for deep cycle batteries

Quote:
Originally Posted by Orville12 View Post
Wanted to add that measured after coming immediately off charge batteries
read 13.40 13.32 13.43 13.10

shortly after 12.90 12.90 12.90 12.84

after 24-48 hrs they would be in 12.50 to 12.65 range before next use
There are three meaningful battery voltage measurements and they have specific parameters associated with them. Battery voltage measurements taken outside those specific parameters have less usefulness in problem solving, if any usefulness at all.

At-Rest Voltage: Typically measured about 12 hours after charging ceases, with no discharging occurring other than self-discharge and the parasitic discharge intrinsic to the specific cart. The rest time needed varies with make/model and age of batteries, but the minimum is usually about 8 hours and the max is usually about 24 hours, or so.

Why a minimum rest time is needed is because during the charging process the electrolyte in close proximity to the plates acquires a higher concentration of sulfuric acid than the electrolyte further away from the plates so the battery voltage is artificially high until the electrolyte reaches an equilibrium throughout. Unless agitated, this takes several hours.

The maximum rest time is less critical. Once the sulfuric acid concentration is equal throughout the electrolyte, the self-discharge rate takes over and the battery voltage progressively decreases.

A similar, but opposite, effect occurs during discharge. The sulfuric acid concentration in the electrolyte next to the plates is less than the that of the electrolyte further away from the plates, so the battery voltage is artificially low. However, it only takes about an hour for the electrolyte to reach an equilibrium in this direction, most of the recovery occurring in the first few minutes. (About 73% recovered in first 10 minutes from the testing I've done.)

On-Charge Voltage: Battery voltage while being charged.

Maximum on-charge voltage reached is determined by the charger.

Under-Load Voltage: Battery voltage while being discharged.

Battery voltage decreases when amps are being drawn. In and of the batteries themselves, a 36V 225AH battery pack drops about 1.0V per 100A of current being drawn. The interconnecting cables and connections also drop voltage, so the observed voltage drop of the pack may be two or three times that.

Attached are Crown SG and SOC charts
Attached Images
File Type: jpg Crown SG.jpg (40.4 KB, 0 views)
File Type: jpg Crown SoC.jpg (66.7 KB, 0 views)
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