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Old 17-01-2015, 23:07   #1
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c20 rate for battery banks and equalizing

Hi Folks,

When a manufacturer says to use a constant charger for equalizing set to 3% of the c20 rate.. is this for the total c20 rate for the bank or for the individual battery pair?

For example, we have trojan t-145Plus batteries, which individually at 6volts has a c20 of 260.

In a parallel at 12 volts the c20 remains 260 but we have four batteries, so am I correct in my calculation when I come to the conclusion that I should use about 15 or 16 amps for equalizing? ((260*2)*3%)

This is what I have used in the past but I am second guessing myself.

Thanks,

z
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Old 18-01-2015, 06:13   #2
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Re: c20 rate for battery banks and equalizing

in parallel you would add the amps, in series the amps are still the same
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Old 18-01-2015, 10:23   #3
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Re: c20 rate for battery banks and equalizing

Quote:
Originally Posted by zboss View Post
Hi Folks,

When a manufacturer says to use a constant charger for equalizing set to 3% of the c20 rate.. is this for the total c20 rate for the bank or for the individual battery pair?

For example, we have trojan t-145Plus batteries, which individually at 6volts has a c20 of 260.

In a parallel at 12 volts the c20 remains 260 but we have four batteries, so am I correct in my calculation when I come to the conclusion that I should use about 15 or 16 amps for equalizing? ((260*2)*3%)

This is what I have used in the past but I am second guessing myself.

Thanks,

z
I don't know why battery manufacturers persist in talking about amperage limitations when equalizing. This is very misleading.

The important thing is to limit the VOLTAGE, usually between 15.0 and 15.5VDC for 12VDC flooded LA batteries.

The batteries themselves will limit the amperage they will accept at any voltage. Doesn't matter if you have a 1000-amp charger, the batteries will only accept a certain amount of amperage -- the correct amount -- so long as you limit the voltage.

The voltage limitation is to prevent damage to the plates from excessive boiling and heating.

Bill
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Old 18-01-2015, 19:11   #4
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Re: c20 rate for battery banks and equalizing

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Originally Posted by btrayfors View Post
I don't know why battery manufacturers persist in talking about amperage limitations when equalizing. This is very misleading.

The important thing is to limit the VOLTAGE, usually between 15.0 and 15.5VDC for 12VDC flooded LA batteries.

The batteries themselves will limit the amperage they will accept at any voltage. Doesn't matter if you have a 1000-amp charger, the batteries will only accept a certain amount of amperage -- the correct amount -- so long as you limit the voltage.

The voltage limitation is to prevent damage to the plates from excessive boiling and heating.

Bill
That was my experience the first time I equalized. I switched to the 3% the last time I equalized.
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Old 18-01-2015, 22:37   #5
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Re: c20 rate for battery banks and equalizing

Nobody had a constant current charger on a boat. So it's a moot point anyways. Maybe in a battery shop.

It's done by voltage.
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Old 19-01-2015, 17:50   #6
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Re: c20 rate for battery banks and equalizing

I trick my Mastervolt into providing constant charge by setting the bulk and absorption phases both to the same voltage and about 8 hours long, then set the wait time on the float cycle to the highest setting, which I think is 4 hours - one advantage to a completely programmable charger. This may not be exactly what a constant charger does but its the best I have and it works really well.

The manufacturers assume that you are already at 100% charge before you begin the equalization, so the acceptance rate is very low anyhow.

I set it back when I am done.

The equalization switch on the bottom of this Mastervolt charger is not only hard to get to but it doesn't seem to function properly... I'm not the only mastervolt that has an issue with this.
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Old 20-01-2015, 05:09   #7
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Re: c20 rate for battery banks and equalizing

To answer your question yes the C20 rate for the total bank unless you are charging each battery individually, which is not a good idea. The other replies are all valid too
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Old 20-01-2015, 08:02   #8
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Re: c20 rate for battery banks and equalizing

Quote:
Originally Posted by btrayfors View Post
I don't know why battery manufacturers persist in talking about amperage limitations when equalizing. This is very misleading.

The important thing is to limit the VOLTAGE, usually between 15.0 and 15.5VDC for 12VDC flooded LA batteries.

The batteries themselves will limit the amperage they will accept at any voltage. Doesn't matter if you have a 1000-amp charger, the batteries will only accept a certain amount of amperage -- the correct amount -- so long as you limit the voltage.

The voltage limitation is to prevent damage to the plates from excessive boiling and heating.

Bill
Bill,

I believe the reason they do this is safety & likely lawyers. With a current limit if the EQ causes an internal shorting failure then you don't have a 100A charger dumping 100A into a 10V battery. Don't ask me how I know about this type of problem... Some chargers automatically limit the max current when in equalization mode, just depends on the charger..

If the batteries are healthy this is not an issue, and as you said the voltage limit will dictate the current flow, but folks often try to revive batteries too far gone and create potentially dangerous situations.

In my own shop I use the lowest current that will maintain the equalizing voltage and no more.. The batteries are also fully charged first. By fully charged I mean 0.5% acceptance at absorption voltage before I EQ. Sometimes batteries are so sulfated I can't get down that low so I stop at .75% or 1% of capacity and then equalize or leave the battery on a high float for a few days..

I personally find a small benchtop variable power supply to be a great tool for equalizing. Set the current, set the voltage and use a wall timer if you absolutely must walk away.....
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Old 20-01-2015, 08:11   #9
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Re: c20 rate for battery banks and equalizing

Maine,

I agree with your comments 100%. Yes, my comments pertain to healthy batteries, not to those compromised by, e.g., an internal short.

I've also found such variable curent & voltage bench power supplies to be great for equalizing. Love my Mastech HY-5020E!

Take care,

Bill
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Old 20-01-2015, 08:18   #10
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Re: c20 rate for battery banks and equalizing

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Originally Posted by btrayfors View Post

I've also found such variable curent & voltage bench power supplies to be great for equalizing. Love my Mastech HY-5020E!

Take care,

Bill
I have two Mastech's, a 3030EX and a 3050EX but also have two BK Precision 1900's and use those a lot for my capacity testing bench. They are 1-16V X 60A. Nice little units but $$$... I like them because they have a dedicated voltage sensing circuit. I wish Mastech would go that route.....
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Old 20-01-2015, 08:33   #11
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Re: c20 rate for battery banks and equalizing

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Originally Posted by Maine Sail View Post
I believe the reason they do this is safety & likely lawyers. With a current limit if the EQ causes an internal shorting failure then you don't have a 100A charger dumping 100A into a 10V battery. Don't ask me how I know about this type of problem... Some chargers automatically limit the max current when in equalization mode, just depends on the charger..

If the batteries are healthy this is not an issue, and as you said the voltage limit will dictate the current flow, but folks often try to revive batteries too far gone and create potentially dangerous situations.
I can't imagine equalizing batteries on a boat without being physically present monitoring the process. Even the manufacturer's published methods require one's presence for regular monitoring of specific gravity, with stopping the process once the cells are balanced.

The above danger is pretty much removed if one is present and monitoring the process.

Mark
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Old 20-01-2015, 08:39   #12
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Re: c20 rate for battery banks and equalizing

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I can't imagine equalizing batteries on a boat without being physically present monitoring the process. Even the manufacturer's published methods require one's presence for regular monitoring of specific gravity, with stopping the process once the cells are balanced.

The above danger is pretty much removed if one is present and monitoring the process.

Mark
I agree 150% but you'd be amazed at how many I know who do and who don't want to sit there for 2, 4, 6 etc.. hours...... I am also amazed at how many equalize as a bank not individual batteries but I do understand the constraints when away from the dock or with short dock time to do this..... With healthy batteries this is obviously fine, but I've seen golf cart batteries murdered in year, so what is healthy & safe becomes the big question...
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Old 20-01-2015, 09:10   #13
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Re: c20 rate for battery banks and equalizing

Unfortunately, we are one of those folks that equalize the bank as a whole. We simply don't have room to stuff another constant piece of equipment anywhere in the boat! I've been told my wife gets AC first.

I would really like to take the batteries out and do it the right way but it just isn't going to happen.

The reality is a bank of our size in either trojan or another manufacturer (like the Duracells) doesn't need to last me 10 years. In the grand scheme of things even if I had to replace my batteries every 4 years, that's $200 amortized per year - on the high end. Not a lot in boat buck terms.
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Old 20-01-2015, 09:17   #14
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Re: c20 rate for battery banks and equalizing

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Originally Posted by zboss View Post
Unfortunately, we are one of those folks that equalize the bank as a whole. We simply don't have room to stuff another constant piece of equipment anywhere in the boat! I've been told my wife gets AC first.

I would really like to take the batteries out and do it the right way but it just isn't going to happen.

The reality is a bank of our size in either trojan or another manufacturer (like the Duracells) doesn't need to last me 10 years. In the grand scheme of things even if I had to replace my batteries every 4 years, that's $200 amortized per year - on the high end. Not a lot in boat buck terms.
If you put a series of on/off switches on each battery equivalent in your bank, you can easily isolate only one battery at a time to be equalized. This also allows you to quickly "remove" a bad battery from the bank without physically having to remove it and rewire the others.

Mark
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Old 20-01-2015, 09:26   #15
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Re: c20 rate for battery banks and equalizing

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Originally Posted by colemj View Post
If you put a series of on/off switches on each battery equivalent in your bank, you can easily isolate only one battery at a time to be equalized. This also allows you to quickly "remove" a bad battery from the bank without physically having to remove it and rewire the others.

Mark
That's a great idea. We have 4x 6 volt batteries, so I would have to remove two simultaneously without having to remove them from the boat. I guess I could use a battery switch. My current switch has an A/B/All but we only have them wired to one bank.

Unfortunately, Cabo Rico thought a smart lace for our battery switch is opposite side of the boat under our wet sink(!), so I would have to add a bunch more wires. Maybe I could put another switch in the battery compartment instead.
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