Setting up outback SCC for lead acid batteries

So I just got my new outback flexmax 60 SCC today and I guess my question is will the 60 amp charge rating of the SCC be too many amps going to my 2 6 volt 232ah lead acid batteries , will that much current damage this small battery bank?
I know that the SCC is overkill but I want to upgrade to 4 battleborn batteries and go to a 24 volt system eventually so the large SCC seemed like the correct move right now. I think you can lower the amount of current to the batteries with this SCC and if that is possible then what amount of amps would be a good setting , or will the SCC just automatically take care of the max current going to the batteries and I'm worried about nothing.
Thanks everyone

6269ed said:

So I just got my new outback flexmax 60 SCC today and I guess my question is will the 60 amp charge rating of the SCC be too many amps going to my 2 6 volt 232ah lead acid batteries , will that much current damage this small battery bank?
I know that the SCC is overkill but I want to upgrade to 4 battleborn batteries and go to a 24 volt system eventually so the large SCC seemed like the correct move right now. I think you can lower the amount of current to the batteries with this SCC and if that is possible then what amount of amps would be a good setting , or will the SCC just automatically take care of the max current going to the batteries and I'm worried about nothing.
Thanks everyone

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Personally I wouldn't be worried about it - 60A into a 232Ah bank is still only just over .25C, which is perfectly acceptable by any Pb manufacturers I'm aware of - in fact perfectly acceptable for LFP as well. I think you're good.

Justin Laureltec said:

Personally I wouldn't be worried about it - 60A into a 232Ah bank is still only just over .25C, which is perfectly acceptable by any Pb manufacturers I'm aware of - in fact perfectly acceptable for LFP as well. I think you're good.

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Hey thanks I am going to hook it up tomorrow and now I feel better about it.

What I have read is that 0.2C is acceptable for lead/acid if battery temperature is monitored. If the batteries start getting hot above that charging rate, you should stop immediately. As long as the batteries don't get physically hot, then the charging rate is OK.

MichaelK said:

What I have read is that 0.2C is acceptable for lead/acid if battery temperature is monitored. If the batteries start getting hot above that charging rate, you should stop immediately. As long as the batteries don't get physically hot, then the charging rate is OK.

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Oooo I will keep an eye on the temp . Thanks for the heads up.

Justin Laureltec said:

60A into a 232Ah bank is still only just over .25C, which is perfectly acceptable by any Pb manufacturers I'm aware of -

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So that I understand calculation of acceptable A into a Lead Acid BB; I currently have 12 - 2V Batteries (85T - 17) rated at 1065 Ah at 72 hours and 850 Ah at 20 hours. I read somewhere that an acceptable charge rate is 10% of the 20 rate, so in my case 85 Amps Max. The formula suggested above equals 266 A at the 72 hour and 212 A at the 72,

Is there some other way to calculate the maximum charge rate or which is the correct answer from above or ???

PS, maximum output of my SCC is 100 A, so will be below that, just don’t know what a safe level would be for these older batteries?

6269ed said:

So I just got my new outback flexmax 60 SCC today and I guess my question is will the 60 amp charge rating of the SCC be too many amps going to my 2 6 volt 232ah lead acid batteries , will that much current damage this small battery bank?

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Your battery manufacturer will have the recommended charge rate for your batteries, usually as a ratio of capacity. Without this, I would not recommend charging a FLA above C/10, some AGMs can handle C/5, gels generally have a lower charge tolerance than FLA. Your charger should, ideally, come with temperature correction too i.e. lowers charge current as ambient temperature increases.

I have a 70A charger, my 220AH AGM battery bank is rated for a C/5 charging rate, therefore, I have to limit charge current to 44A.

Without further guidance from your battery manufacturer, I would recommend that you limit your charge current to 23.2A.

p.s. Overcharging lead-acid batteries contributes more to premature ageing than over-discharging.

Edit: Added postsript.

tictag said:

Your battery manufacturer will have the recommended charge rate for your batteries, usually as a ratio of capacity.

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I inherited this System and the batteries are about 18 years old; I can't find any info for them.

tictag said:

220AH AGM battery bank is rated for a C/5 charging rate, therefore, I have to limit charge current to 44A.

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What is the calculation you used to get 44A?

tictag said:

Without further guidance from your battery manufacturer, I would recommend that you limit your charge current to 23.2A.

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What is the calculation you used to get this number?

tictag said:

p.s. Overcharging lead-acid batteries contributes more to premature ageing than over-discharging.

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Yes, understood. That is why I joined this Forum; I am anticipating having to replace these old beauties in the upcoming future and will be going to Lithium. Because I am upgrading to a more efficient VE MPPT, capable of 100 A, I want to know what I should set it at; so far I have about 5 different numbers.
Thanks

TommyD said:

What is the calculation you used to get 44A?

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Max charge current for my AGMs = C/5
...therefore, max charge current = 220AH / 5
...therefore, max charge current = 44A

TommyD said:

What is the calculation you used to get this number?

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Max charge current for FLA (without further advice from battery manufacturer) = C/10
...therefore, max charge current = 232AH / 10
...therefore, max charge current = 23.2A

Note: a 232AH 6V battery connected in series to another 232AH 6V battery gives you a 232AH 12V battery.

TommyD said:

Because I am upgrading to a more efficient VE MPPT, capable of 100 A, I want to know what I should set it at; so far I have about 5 different numbers.

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Most Lithium-ion battery chemistries support up to 1C charge rates, so if you had a 232AH lithium battery you could charge it at up to 232A! Lead-acid battery technology falls way short, especially when it comes to charging. All batteries are different, have different recommended charge rates. Without guidance from the manufacturer, all I can offer is my own personal experience. Prior to my AGMs I had two 110AH FLA batteries and I charged them at C/5, even though the manufacturer recommended C/10. I had to replace them both after a year.

p.s. It is very unlikely that charging at a higher rate during the constant current phase (Bulk phase) will cause a safety issue, a lead-acid battery will only start to 'boil' with cell voltages above 2.45V (6S = 14.7V), which your charger will not allow, but you will prematurely age the battery due to the higher internal temperature. Maybe this doesn't matter if you're going to be replacing them soon anyway? That's your call.

Edit: Added postscript.

So, obviously I didn't have enough Coffee this AM; math is simpler that I was looking for !!

But, am I still missing something. You indicated earlier that I should limit the charge Amperage to 23.2A. You apparently used a C10 rate in this example. But each of my 2V Batteries is rated at 1065 Ah @ 72 hours and 850 Ah @ 20 hours. These batteries have a significantly higher Ah than your example; do these batteries have a C10 rating of 106.5 A or 85 A respectively? And if so, seems the 85A max charge rate is correct?

I was actually replying initially to the OP (@6269ed). Sorry for any confusion. You always use the C20 discharge rate when calculating charge rate using your manufacturer's recommended charge rate ratio e.g. if they recommend a C/10 charge rate then you would limit current to 85A, if they recommend a C/5 charge rate, then you would limit charge current to 170A etc. I am assuming you have lead-acid batteries.

With lead-acid, the lower the charge rate, the longer the batteries will live and the more capacity they will retain (Puekert effect).

Super!! Thanks