Still more Battery questions......

[bigstik40]

I think I have stretched my batteries almost as far as I can, but still have a question or two!! I have six Trojan T-105's (dates are Jan 08) in my 07 EZGO TXT with PDS. My symptoms are that after only 1-1/2 miles of running and after a full charge, two of the batteries just "lay-down" (Voltage drops to maybe 3 volts each) and the cart slows some. Before that happens, the cart runs great and running voltage is 35-36 volts. I know my pack is just "fair", as the open circuit voltage (after charge and 12 + hrs rest) shows only 90% state of charge. My question is: is this typically the way these batteries act when they are nearing "the end", or is there a possibility that I have a charging problem?? Is there any hope of recovering some capacity if I individually charge these two batteries?? I have noticed lately that the charging time is becoming pretty short (5 hrs), but I think maybe it is those two batteries at fault. The charger finishing voltage rises to 45-46 volts, so that seems to be in order. Should I just give-in and get new batteries?? - RAY

[scottyb]

It does sound typical of the complaints I heard from clients with old worn out batteries when I did service work.

Let me guess, that the 2 that are the weakest are the 2 that provide the 12v accessory power? Sometimes that will make those 2 fail sooner than the rest.

[JohnnieB]

Those batteries are going on 5 years old, so it is time to "give-in" and bite the bullet.

With proper sizing and care, a set of batteries may very well last longer than that, but I suspect they didn't get much TLC before you acquired the cart.

What are the individual battery voltages 12 hours after charging?

[bigstik40]

Just measured them this morning after more than 12 hrs rest! They are as follows: 1.6.30 volts 2. 6.30 volts 3. 6.29 volts 4. 6.33 volts 5. 6.32 volts 6. 6.28 volts. The low capacity batteries are #1 and #4 and my pack is not tapped for accessories. The two low batteries act like they are each 50 AH batteries, and before they "give up the ghost" their internal resistance seems to be similar to the other four, because my meter shows a fair loaded voltage (33-35 v) for most of the mile or mile and a half. I believe new batteries are in my near future . - RAY

PS- Johnnieb, just saw where you are on antibiotics via IV. Hope you are feeling better except for the port. A gal here in our community is doing the same thing due to immune system problems. She has made a remarkable recovery with this regimen. Good luck....

[JohnnieB]

The "fully" charged voltage is consistent between batteries, only a 0.05V spread.
However, they are all low and two drop out under load.

A new set of batteries is in your foreseeable future.

If you plan on waiting until spring to replace them be sure to keep the old ones charged during the winter so they don't freeze and bust the case, leaking acid in your cart and on the floor.

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You could try charging the ones that fail under load separately, but I doubt if it would help much.
On the other hand, it won't hurt them.

[bigstik40]

Thanks for the responses, guys !! Yes, I did "give in", now have 6 new T-105's. After searching around the net a little more, I came up with an article aimed at the "off grid" folks. Here is a quote of one of the bullets in it that (I think) answers my original question.

"False" Capacity
"A battery can meet the voltage tests for being at full charge, yet be much lower than it's original capacity. If plates are damaged, sulfated, or partially gone from long use, the battery may give the appearance of being fully charged, but in reality acts like a battery of much smaller size. This same thing can occur in gelled cells if they are overcharged and gaps or bubbles occur in the gel. What is left of the plates may be fully functional, but with only 20% of the plates left... Batteries usually go bad for other reasons before reaching this point, but it is something to be aware of if your batteries seem to test OK but lack capacity and go dead very quickly under load."


This is exactly the symptoms of my recent two bad batteries. (I lost one 6 months ago also with the same symptoms, so that makes 3 out of 6.) I don't think the rest were very far behind!! Thanks again for your responses - RAY

[JohnnieB]

I'll bet your cart is running better.

Be sure to break those new batteries in right. http://www.cartsunlimited.net/Batter...n_Methods.html

Most the battery info on the "Off-Grid" sites is pretty good, but not all of it.
Here is what I found on one of them:

Gassing - is when batteries start to gas when you attempt to charge them faster than they can absorb the energy. The excess energy is turned into heat, which then causes the electrolyte to boil and evaporate.
The first sentence is almost true.
When a charging current passes through a lead-acid wet cell, three things happen:
1. Part of the energy is used converting lead sulfate back into lead (Negative plate), lead dioxide (Positive plate) and sulfuric acid (electrolyte)
2. Part of the energy is used decomposing the water component (H2O) of the electrolyte into the two gasses it is composed of, Hydrogen and Oxygen.
3. Part of the energy is converted to heat.

How much of the available energy is used by which of the three varies with the internal resistance and on-charge voltage of the cell, but most is used by the first two unless there is something seriously wrong with your battery charger, or the charger is the wrong voltage and/or ampacity for the batteries being charged.

The second sentence is completely false.
The boiling point of pure water is 212°F and the boiling boiling of diluted sulfuric acid (electrolyte is about a 30% concentration) is much higher.
Unless there is something seriously wrong with the charger or the wrong charger is being used, the batteries are not likely to climb above about 120°F unless the air temperature is over 100°F and even then it will not get anywhere near the boiling point of 30% H2SO4.

The bubbles rising to the surface are bubbles of Hydrogen and Oxygen gasses.

Gassing (electrolysis of water) occurs throughout the charge cycle, but heavy gassing begins at about 2.35V per cell, or about 42.3V for a 36V pack.

The second sentence implies you are doing something wrong if it occurs and that it is a bad thing.
It is a normal part of charging lead-acid wet-cells and it is a good thing because it mixes the electrolyte so the concentration is the same throughout.

[scottyb]

I'm going to double post this from another thread because it is so important that everybody understand what is happening and why in the charge cycle:

64v = 2.66 v per cell = 10.66 v per 6/8v battery
This is the final equalization phase of the charging algorithm (pattern)
Equalization is essentially a controlled over charge.
Higher capacity wet (flooded) batteries sometimes benefit from this procedure, particularly the physically tall batteries. The electrolyte in a wet battery can stratify over time, if not cycled occasionally.
In equalization, the voltage is brought up above typical peak charging voltage (to 11 to 12 volts in a 8 volt system) well into the gassing stage, and held for a fixed (but limited) period.
This stirs up the chemistry in the entire battery, "equalizing" the strength of the electrolyte, and knocking off any loose sulphation that may be on the battery plates.

For more information go to > Scottyb's Carts Unlimited

[JohnnieB]

Scotty, those equalization voltages might be a little high.

Trojan User Guide suggests an equalization voltage of about
2.6V per cell.

However, if you can give me a source for those number, I'll check them out.

Might just be a typo in the equation. With 64V on a 48V system, the per cell voltage is 2.667V.

[scottyb]

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