EZGo 36v Interpret Battery Test Results

drosen

Hello everyone:

Sorry for the longish post, but I'm a newbie here and I want to be as complete as I can so someone to help me.

Last summer I was given a 2002 EZGO TXT electric 36v with all new Ray-O-Vac Ultra batteries. These may not be the best, but they worked fine for the few times cart was used. When fully charged, the batteries showed 37.6 volts. The cart gets limited use, but it gets fully charged every 2 weeks.

A couple months into this summer I noticed the car runs out of charge much faster than it did last summer. Full charges still produce 37.6 volts like last year.
I recently gave it a full charge and haven't driven it since. I disconnected one cable so I could test each battery individually, and let the batteries "settle" per a post in this forum. I tested the voltage right after the full charge and again after waiting 12 hrs, 24hrs, and a week from when fully charged.
The results were:

Right after full charge: 6.3, 6.2, 6.2, 6.3, 6.3, 6.3
12 hrs later: 6.4, 6.3, 6.3, 6.3, 6.3, 6.3
48 hrs later: 6.2, 6.2, 6.2, 6.2, 6.2, 6.2
A week later: 6.2, 6.2, 6.2, 6.2, 6.3, 6.2

QUESTION: Is there anything in these results that indicates any abnormality?
What else and how do I test for what might be an age-related sudden extra battery draw when driving it?

Thank you in advance for any help.

BGW

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hunt365

A full charge should be around 38.2. At 37.6 you're starting at around 85%. You can load test each battery by hooking up your dvm individually and driving the cart up a hill. record the voltage at the start and the lowest voltage during the climb. Do this to each battery. Compare the difference in voltage for each battery. Make sure the water is covering the fins by a 1/4 in or so after a full charge. use distilled water. Really good write up in the stickies on battery maintenance. I prefer to charge my batteries after each use. Its not good for them to sit in a discharged state.

drosen

Thank you for the quick response and for taking the time to reply.
I suspect the lowish voltage of 37.2 is really because they are inexpensive batteries, and I would be ok with only moderate performance, but what concerned me was how the full charge reading is the same as last year but the run time before struggling to go up a hill is about half.

Because it's old (me too!) I wondered if there is and electrical part like a voltage regulator or something that is causing it to draw too much juice and run down extra fast.

Thanks for the tip on charging it more often even if the batteries are not used and not run down, and for the load test description.

ThreeCW

The load test that hunt365 outlines should give you the best indication of your battery's performance. The low battery pack voltage (only 85% charge) is certainly a concerning factor, but as you said ... no change since last year except your hill climbing ability. Perform the hill climb test and the results certainly may indicate a bad battery ... which is not visible in the "no load" test that you performed.
Regards, 3CW

JohnnieB

Battery voltage is determined by chemistry rather than cost.

The voltage of a 6V lead-acid wet-cell deep-cycle battery ought to be about 6.37V about 12 hours after the charger shuts off automatically, or about 38.2V for a 36V pack - see attached chart.

A 36V deep-cycle battery charger typically shuts off at about 45V, so immediately after the charger shuts off, each 6V battery ought to be at about 7.5V.

The voltages given in your first post for right after full charge add up to 37.6V, but the voltages after 12Hrs add up to 37.9V. That is abnormal since the batteries ought to start self-discharging the moment the charging stops.

What make/model charger are you using?

What is the Amp-hour rating of your batteries at the 20 hour rate?

Attached Images

SoC vs Voltage.jpg (259.3 KB, 0 views)

drosen

ThreeCW - Thank you for your reply. If it ever stops raining here I'll be able to try the load test. If I understand what you wrote, I'll be looking for one or more batteries showing a significant voltage drop while under load climbing a hill.

JohnnieB - I am using a PowerWise battery charger, Model 28115 G04.
The bartteries are RayoVac Ultra Pro SLiGC110. The 20amp-hour capacity is 215.

NEW INFO: When I got the car last summer, the plates in each cell were all covered (barely). The distance from the top of the plates to the bottom of the tube was about 3/4" so I added distilled water. This summer I had to add about 1/2" water to each cell. In the old days with car batteries adding more water (from evaporation) diluted the acid and weakened the batteries. We used to buy and add a little extra sulphuric acid. I don't know if that would help, or if they even sell sulphuric acid to do that any more.

hunt365

Not sure about the sulphuric acid, might work. I've only added distilled water to mine and they still check like new after two years. keeping the plates covered is important as to not let oxygen get to them. Too much water and they'll boil out during charging. You may try running a couple of charges consecutively to see if it helps. Watch you dvm during charging to see what numbers you come up with. As Johnny B stated the voltages rising sounds funny. Mine are always highest immediately after the charger shuts off. Hopefully the load test will reveal something.

yurtle

Only water evaporates, not the acid.

cgtech

As far as I know, the acid in the battery is the acid in there for life. Only the water components of that mix leave during charging & discharging. Hydrogen & oxygen are all that's lost during the electrolysis process, and therefore pure water is all that needs to be put back in. That's why having your batteries "boil over" is bad for them, then some acid content is lost.

JohnnieB

Your batteries are made by East-Penn and are sold under several different labels by big-box stores. Other than being a bit lower than the standard 225AH, they should perform well and give several years of service. The lower Amp-Hours will lessen the max distance that can be traveled on a single charge and lessen the usable lifespan a bit, but that is all.

The PW 28115 is a charger that was shipped with EZGO carts for several years and when working properly does a reasonably good job of charging a 36V battery pack, however the voltages posted for right after charge indicate your charger is not working properly and it may have not been working right for as long as your batteries have been in the cart.

When working correctly the PW 280115 does not shut off automatically until the on-charge voltage climbs into the 44V-46V range.

Basically, your batteries may not have ever been fully charged since they were new. If so, they have been damaged, but they may recover some with back-to-back charging from a properly working charger.

Attached are the service manual for a PW 28115 and how to check the transformer and capacitor.

Attached Images

	Transformer-Capacitor test - Text.JPG (176.2 KB, 0 views)
	Transformer-Capacitor test.JPG (66.2 KB, 0 views)

Attached Files

PW Charger manual.pdf (3.02 MB, 0 views)