Strange Equalization Behavior

[wingssail]

My four two year old golf cart batteries started loosing capacity (they charge up fast but run down fast) they were good for two years and all the charging and discharging numbers made sense until last week, then WOW, I could only get about 110AH into or out of them. Previously I could get 160AH.

OK, disappointed, but it is what it is. I decided to equalize them so back to the dock and shore power. Ran an equalize cycle in my Magnum Charger/Inverter. Followed all the steps and instructions to the letter. 15.5 volts, four hours. The cells gassed plenty but didn't loose any electrolyte. The SG gradually crept up to about 1.262, across the board.

But here's the funny thing: The batteries continued to accept 35-45 amps, all the way to the end of the cycle.

And after equalization there is some improvement but not much. I can get about 140AH in and out of these batteries.

So I will run them until they die and buy some new ones, but I am really curious about the high amperage acceptance during the equalization cycle.

[Jim Cate]

The cells gassed plenty but didn't loose any electrolyte.

Fred, how can this be? The gas comes from disassociating the electrolyte, does it not?

Jim

[Tomodore]

Yes strange, but the bottom line is the batteries are toast or nearly toast. We just changed golf cart batteries after 4 years and it’s like a new lease on life. They charge faster, last longer and jump higher….well maybe not the last part. Whether it was something you did or the batteries or your system that’s at fault is open, but even though they should last longer they don’t seem to be lasting. Equalization is important and how often is open to opinion. Consider replacing the batteries, imagine a boat owner with an unexpected project and expense, well it didn’t take much imagination.
Fair Winds

[Stu Jackson]

Originally Posted by wingssail

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But here's the funny thing: The batteries continued to accept 35-45 amps, all the way to the end of the cycle.

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My Freedom 15 limits equalization current to around 15A on a nominal 400 ah house bank. Yes, it sounds funny.


With your house load on a daily basis, what's your load and house bank capacity?

[wingssail]

Originally Posted by Jim Cate

Fred, how can this be? The gas comes from disassociating the electrolyte, does it not?

Jim

You tell me.

All I know is that they bubbled plenty, and I could hear that throughout the boat, blub blub blub and I watched the electrolyte level like a hawk with my bottle of distilled water at hand and a funnel, and it didn't go down, not a millimeter, not in any of the twelve cells.

[wingssail]

Originally Posted by Stu Jackson

My Freedom 15 limits equalization current to around 15A on a nominal 400 ah house bank. Yes, it sounds funny.

With your house load on a daily basis, what's your load and house bank capacity?

Well, we have 450AH capacity and we use and replenish, about 140-160AH per day.

It goes like this: In the morning the batteries are sitting at about 12.3-12.4v. They get a little lower before the solar cuts in strongly. After a good day's solar, during which we bring in about 60-80AH, the charging cycle in the evening adds whatever else we need to get them up to 14.7v ("float" on the regulator) and when we go to bed charging is over and they are at 12.6-12.5.

That's before they started losing capacity. Now (before the equalize fiasco) they would hit 14.7v much sooner while charging, and run down more over night.

I guess they are nearly toast, and we'll run them to death then replace them.

But that doesn't stop me from being curious.

[smac999]

Hitting 14.7v means nothing. A dead battery with a charger on it can read 14.7v. You need to see the current at that voltage to know if they are full or not. I bet you never fully charged the batteries at sea. Which kills batteries.

You say you use 160ah a day and bring in 80 a day with solar. Where is the other 80 coming from?


To know if the batteries are still good or not you need to fully charge them (easiest at dock). And then do a c20 drain test.

[wingssail]

Originally Posted by smac999

Hitting 14.7v means nothing. A dead battery with a charger on it can read 14.7v. You need to see the current at that voltage to know if they are full or not. I bet you never fully charged the batteries at sea. Which kills batteries.

You say you use 160ah a day and bring in 80 a day with solar. Where is the other 80 coming from?


To know if the batteries are still good or not you need to fully charge them (easiest at dock). And then do a c20 drain test.

The other 80 or more comes from charging with the main engine using the Balmar alternator. I track it carefully.

Yes you are right, the batteries are rarely fully charged at sea unless we motor for a long distance, say 10-20 hours of motoring.

When I say we charge until they reach 14.7v, that's the voltage set in the regulator to end the "bulk" charging phase. Does not mean fully charged, but it's more than "nothing". It is where we cut off charging because the charging rate really cuts down after that. Cutting off charging, after about 1 hour, the batteries settle down to 12.7v

After our equalization cycle (at the dock) we did run a discharge test. After 24 hours of discharge at 8-10amps the batteries had gone down from 12.7 to 12.2v. This is about standard for us with our low battery capacity and low solar output.

Given the earlier weird equalization readings, which I still don't understand, and a charge/discharge cycle to test them which showed no improvement, I decided the batteries were near end of life.

But here is the second weird thing: We went back on our cruise, determined to make the best of the batteries and change them when they died. For two days it was same as before: short charging cycle, limited amp acceptance, and quicker than optimal discharge.

But on day three, whole new ball game. The batteries suddenly came back better than ever. Now they take 80-95 amps for 90 minutes and the voltage only reaches 14.7 at the end of that period, AND, they hold their charge like they did two years ago. So, it seems like I have a self repairing electrical system. I have noticed or made NO OTHER changes in the system, but the batteries are all of a sudden much better. Happy me.

[nightowle]

I'm sure it's because you finally sailed beyond the Bermuda Triangle.

[Jim Cate]

After our equalization cycle (at the dock) we did run a discharge test. After 24 hours of discharge at 8-10amps the batteries had gone down from 12.7 to 12.2v. This is about standard for us with our low battery capacity and low solar output.

So, after a full charge (implied by reaching equalization limits) you then took ~200 ahr out and the resting voltage showed ~ 50% SOC , assuming normal temperatures.

That seems pretty good to me, Fred... I'm not sure what the problem is.

Jim

[wingssail]

Originally Posted by Jim Cate

So, after a full charge (implied by reaching equalization limits) you then took ~200 ahr out and the resting voltage showed ~ 50% SOC , assuming normal temperatures.

That seems pretty good to me, Fred... I'm not sure what the problem is.

Jim

Yes, it seems OK, right now. My query was the weird equalization behavior, but it's going to be one of those things I shrug about.

We're back on our cruise and I'm just watchful.

[donradcliffe]

Did you fuss with the battery connections?

[wingssail]

Originally Posted by donradcliffe

Did you fuss with the battery connections?

Yes, a couple of days before equalization I removed the battery connections and cleaned them up then re-attached them. I also filled the cells which were low on electrolyte.

Now here is a question to anyone who is still reading this:

Since my original question was what about the 40-50 amps going into the batteries during equalization? I wonder now if there might be a drain into the alternator? The alternator output leads go directly to the battery (through the battery switch). During equalization the battery was switched on. Everything else was switched off (except the alternator was still connected).

Could the current I read going to the batteries have been actually been going through the alternator positive lead to ground? If I do another equalization next time I am on shore power I'll check the alt for warmth or actually disconnect the pos lead and see if the amps going to the the battery system go away.

As it is, when everything is switch off, but the battery switch is "ON", I don't see any sign of current flow out of the batteries, like it does not appear that current is flowing to the alternator and then to ground during normal situations or connections.