36 volt battery meter/ bad charger?

[Gibb]

Yepper Dawgn,
Cause I didn't do my homework enough, thats about all I can say bout that.....
Besides, ya learn MORE from hard knocks. Next Time Next Time

[JohnnieB]

Originally Posted by Gibb

I unplugged and replugged the charger in about 3 hours ago , just checked them again and the pack is reading 45.5v and individual batts are reading a range from 7.0v to 7.8v and the charger is still on. Not a pro with the DVM so Im not sure if the individual batts are ok at 7.0 7.8.

If the batteries are the same make & model, about the same age and have been subjected to the same charge/discharge conditions, they should have the same voltage on them at all times. (On-charge, at rest and under load)

Ideally, if the pack voltage was 45.5V, the individual batteries would all read 7.58V, but no batteries are truly identical, so some slight differences in voltage may be seen.

A difference of 0.1V between highest and lowest reading is acceptable, and you've got a difference of 0.8V.
Since each of the 18 cells in your 18 cell battery pack contributes 2V to the total and the difference is less than 2V, all the cells are working, but some aren't working as well as others.
In other words your battery pack is imbalanced and needs to be equalized.

If you don't have access to a high end charger with an equalization mode (46.5V constant voltage mode), there are two ways of approximating an equalization charge at home.

1. Charge a "Fully" charged battery pack with your regular 36V charger four or five times, lightly discharge and recharge once more. Let rest at least 6 hours to deplete most of the surface charge, or take a quick trip around the neighborhood, and check individual battery voltages. If still greater than 0.1V between highest and lowest. Repeat process.

2. Charge the lower voltage batteries separately until they come up the the same voltages as the higher voltage batteries.
a. If you have a 6V charger, you can do them one at a time without disconnecting the interconnecting cables in the pack.
b. If you only have a 12V charger, you may need to move the batteries around in the pack so the lowest two are adjacent to each other for charging with the 12V charger.

----------------

Load testing is the best way to determine battery health, but load testing deep cycle batteries takes $pecialized test equipment.
The inexpensive load testers found in auto parts stores are designed for SLI (Starting - Lights - Ignition) batteries, so the charts that come with them are more or less meaningless for deep cycle batteries. They will show major problems, but if you don't already have one, don't buy one, there is a better way.

Fully charge batteries, let rest a few hours and record individual battery voltages.
Drive cart for about a half an hour, let rest for about 15 minutes and record voltages again.

Both the before and after voltage spreads should be within 0.1V.
The voltage on the weaker batteries will drop more than the good or better batteries.

Hope this helps.

[Gibb]

I just checked my pack after being on the charger all night and its reading 36.9v

Individualy Im reading
6.18 6.16
6.13 6.12
6.11 6.13

So am I on the downward spiral for needing new batteries? How long may I get from these?
Anyway to bring them back to life 10% or more, they are about two yrs old?
I just bought the cart about 3 weeks ago and know little about it but learning more everyday thanks to BGW :)

[Gibb]

JohnnieB,
Just saw yer post, u beat me to mine!!
2 out of the 6 differant.

[scottyb]

It is possible to find 2 good used batteries and make a healthy pack out of a 2 yr old set. If that is truly what is needed. I never saw any individual readings of the entire pack

[JohnnieB]

Originally Posted by Gibb

I just checked my pack after being on the charger all night and its reading 36.9v

Individualy Im reading
6.18 6.16
6.13 6.12
6.11 6.13

So am I on the downward spiral for needing new batteries? How long may I get from these?
Anyway to bring them back to life 10% or more, they are about two yrs old?
I just bought the cart about 3 weeks ago and know little about it but learning more everyday thanks to BGW :)

The good news is that all the batteries are within 0.1V of each other. (Spread is 0.07V)
The bad news is that all the readings are terrible.

You could try repeatedly charging them with little or no discharge between charge cycles for a couple days, but I have my doubts it it would improve them very much.

Sorry, but I believe the bottom line is that you need a new set of batteries.

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When you get the new batteries, be sure to fully charge them before first use, then break them in properly and then keep them as fully charged as possible or practical.

[Bud Man]

I agree with JohnnieB but if it were me I would not give up yet, keep working with them charge charge charge they may be salvageable or at least may last a while so you can save up $$ for some new ones.

[Gibb]

You could try repeatedly charging them with little or no discharge between charge cycles for a couple days, but I have my doubts it it would improve them very much.


-------------------

Little discharge meaning,
5 min?
10 min?
15min?

I only travel a mile or two from my house so far and when I get back the cart still seems to have plenty of power left in it so I really dont want to bust out more $$ like Bud Man says on new batteries right now.

I'll do the discharge and charge charge charge thing for now besides if I tell my wife we need to buy new batts we all know the OUTCOME seeing that I've ordered everything to make it street legal and a lift....

[JohnnieB]

I meant you could restart the charger immediately after it shut itself off, or after a few hours had elapsed, but do it at least two or three times a day, and that it is fine if you need/want to use the cart.
If it is running strong after a couple miles, fine, but if it is barely running on the way home, that is too far.

What has happened to your batteries is that lead sulfate has built up on the plates, reducing the area exposed to the electrolyte. Lead sulfate is part of the normal charge/discharge chemistry, but if it is allowed to sit on the plates too long, or too much of it is allowed to build up, the normal charging process cannot occur.

Technically, amorphous lead sulfate (soft) is what the plates turn into during discharge, but if it is allowed to sit, it turns into crystalline lead sulfate (hard), which does not readily revert to lead (negative plate), lead dioxide (positive plate) and sulfuric acid (electrolyte) when electrons are passes through it.

Soft lead sulfate does not suddenly change into to hard lead sulfate, so a modest amount of the "Not quite hard yet" lead sulfate can be convinced into turning back into soft lead sulfate by charging the cells until the specific gravity of the electrolyte ceases to increase while a charging current is passing through the cell.

Unless you have a special charger, the closest you can come to doing this is repeatedly initiating a regular golf cart battery charger when the batteries are charged to the maximum storage capacity they have with the amount of sulfation that exists on their plates.

Will there be an improvement? Maybe, it depends on how deeply they were discharged and how long they sat that way, plus a bunch of other factors.

How much improvement? I don't know. I got about 10% higher SoC, but I started at about 85%, while you are starting at about 65%.

About all I know for sure is that there isn't much of anything that can be done to those batteries that will harm them more than they have already been harmed.

I know what you mean about keeping momma happy.

[Gibb]

How would I know the differance between a high end charger with an equalization mode (46.5V constant voltage mode), from what I have? The reason I ask is, my boss has a 36v ezgo with a charger that looks a lot different than mine.

I did notice some of the batteries are leaking from around the filler caps and the water is up about an inch from the plates or an inch down from the top of the batt. Would it help if I pulled some out to where the water is just covering the plates?

Thanks for the help guys ( Trying to keep momma happy ;)