Equalization current for flooded batteries questions

mcgivor · June 2017

Having replaced a Morningstar TS 60 PWM controller with a Schneider 60-150 MPPT, i've noticed during equalization the Schneider has an algorithm completely different from that of the Morningstar. The Schneider has a one hour EQ with a high current, ~25 amps on a 24V nominal 260Ah battery, battery Ah is programed correctly. The Morningstar on the other hand has a 3 hour EQ at a much lower current, usually around 6 amps if memory serves me right. Many say that an elevated voltage with low current is the normal profile. So the question is, does Schneider assume, being a solar charger, there may not be enough hours in the day to fully charge then do an extended EQ of 3 hours, hense the one hour at higher currents and if so could this in fact be detrimental, your thoughts and opinions will be greatly appreciated.

Marc Kurth · June 2017

Equalization is only performed on a battery that is fully charged, so the current draw should be comparatively low when the voltage ramps up to the equalization level.

You can set the max current, which the charge controller will achieve by reducing the voltage - but the whole point is to hold the higher Equalization voltage. I don't see a need for limiting charge current, because the increase in current draw will be transitory anyway.

Estragon · June 2017

Is the EQ temp compensated with a properly working remote sensor? It sounds like either the battery wasn't really full before the EQ, or the EQ voltage is too high relative to temp. IMHO the EQ should only draw more than a small current for a short time (while voltage rises from Vabs to Veq), then just take a couple amps to hold it there.

Also, I assume the 25a is really net to the battery (not including any loads).

mcgivor · June 2017

Marc Kurth said:

Equalization is only performed on a battery that is fully charged, so the current draw should be comparatively low when the voltage ramps up to the equalization level.

You can set the max current, which the charge controller will achieve by reducing the voltage - but the whole point is to hold the higher Equalization voltage. I don't see a need for limiting charge current, because the increase in current draw will be transitory anyway.

The voltage programed for EQ is at 32V , the current limit is programable but currently set high, 50A to satisfy opportunity loads, didn't think it nessary to reprogram to perform an EQ. The CC will only go into EQ if fully charged, or 2% current vs battery Ah capacity, once this is satisfied the voltage rapidly climbs to 32V , along with the current,~25A, the count down timer displays time left in EQ and holds this current until termination, one hour. The batteries are approaching their end of life, so perhaps this is a factor.
The voltage is temperature compensated, no loads present, to answer questions whilst writing this, the one hour EQ is the curious question, longer slower, or hard and fast, perhaps someone with Schneider experience can shed some light

littleharbor2 · June 2017

Sounds like a question for @Dave Angelini.

Marc Kurth · June 2017

To be clear, I think that you have said that:
Your Morningstar controller would hold EQ voltage, but the batteries only drew 6 amps.
Your Schneider controller holds the same EQ voltage, but the batteries draw 25 amps.
I can't wrap my head around that.
Was the current draw with the Morningstar low because it wasn't reaching the equalization voltage?

If you meant that you only want to hear from people with Schneider experience, I will stop now.

Marc

mcgivor · June 2017

Marc Kurth said:

To be clear, I think that you have said that:
Your Morningstar controller would hold EQ voltage, but the batteries only drew 6 amps.
Your Schneider controller holds the same EQ voltage, but the batteries draw 25 amps.
I can't wrap my head around that.
Was the current draw with the Morningstar low because it wasn't reaching the equalization voltage?

If you meant that you only want to hear from people with Schneider experience, I will stop now.

Marc

The Morningstar reached the voltage but at a lower current for a longer period.
The Schneider reaches the voltage at a higher current for a shorter period,, 1 hour vs 3 hours

mcgivor · June 2017

@ Marc Kurth, sorry, not just people with Schneider experience, although they would be helpful, Amy input is welcome , thanks, your coments are valuable and appreciated.

Marc Kurth · June 2017

mcgivor said:

Marc Kurth said:

To be clear, I think that you have said that:
Your Morningstar controller would hold EQ voltage, but the batteries only drew 6 amps.
Your Schneider controller holds the same EQ voltage, but the batteries draw 25 amps.
I can't wrap my head around that.
Was the current draw with the Morningstar low because it wasn't reaching the equalization voltage?

Marc

The Morningstar reached the voltage but at a lower current for a longer period.
The Schneider reaches the voltage at a higher current for a shorter period,, 1 hour vs 3 hours

But the battery determines the current draw based on the voltage being applied. At any given voltage, a battery will draw exactly the same amperage from whatever is applying that voltage (Assuming that the power is available)

The only way that a charging source can control amperage draw by the battery is to change the voltage being applied to it. A charging source cannot increase the battery charging rate, unless it increases the voltage.

I'm wondering if your battery(s) have developed a partial short. That would explain the higher 25 amp draw at the same voltage that previously caused the battery to draw only 6 amps.

Just thinking out loud, because something doesn't make sense.

Marc

Estragon · June 2017

It's not making sense to me either. If the change in behavior happened when the CC was changed, it mostly (but not entirely) rules out the condition of the bank.

Have you checked SG at any point(s) in the process? It may help to know if the end of absorb really is at fully charged.

It might also be worth checking actual voltage at the bank and manually working out the temp compensation as a sanity check to be sure the CC is properly compensating.

mcgivor · June 2017

Perhaps there may have been some oversights on my behalf, including factors such as cell ballance being different during the respective EQ's. It is entirely possible the Morningstar may have begun at a higher current during the first hour without my noticing, as it was not a concern at that point in time, tapering down in the latter stage, hour 3. It would be reasonable to assume the battery will accept all the current it can absorb at a given voltage, baring an internal short, so my observation during the Schneider's 1 hour EQ may merely be anxiety, if the EQ were allowed to continue for 3 hours it may well terminate with a lower current. Should this be the case, it may indicate the battery needs a longer time in EQ than the 1 hour fixed Schneider default, which seems short, all literature I've read indicates a longer cycle. All cells have ballanced SG at 1270, string charge/discharge currents close and individual monoblock voltages within 0.05V, but the battery is nearing end of life.

Marc Kurth · June 2017

I would concur with that!

WaterWheel · June 2017

I also have the 1 hr Schneider EQ with my 80-600. The current drops as it gets further into the EQ or if after the 1st hr of EQ I program in a 10 minute absorb and another hour of EQ. After the 1st 15 minutes on the second EQ the current continues to drop.

I really with there was a way to program the Schneider to go for a longer (like 3 hour) EQ so I could terminate it manually when SGs evened out.

mcgivor · June 2017

WaterWheel said:

I also have the 1 hr Schneider EQ with my 80-600. The current drops as it gets further into the EQ or if after the 1st hr of EQ I program in a 10 minute absorb and another hour of EQ. After the 1st 15 minutes on the second EQ the current continues to drop.

I really with there was a way to program the Schneider to go for a longer (like 3 hour) EQ so I could terminate it manually when SGs evened out.

Will try a second EQ next time to see if it in fact drops, I would agree with having the option to extend the 1 hour as useful, the engineers who developed it must have had their reasons, perhaps a cautionary one, like no auto EQ capabilities, just a reminder, which personally I think is better, strange things could happen if you are not there to monitor and they usually happen that way.

Vic · June 2017

Flooded batteries that are otherwise is good condition, but seriously need an EQ will require considerably more current (into the battery), than will the same size/age battery that on needs a mild amount of EQing.

Older batteries that are in generally good condition, seem to have EQ currents that are higher on exiting EQ, than those which are young..

Like to watch the measured battery current (Shunt current) when the EQ is done, this can be an indicator of general battery health.

This is relative to batteries that have received a full charge preceding the EQ, and for Veq that is temperature compensated, and for Veq settings that are the same, when comparing Ieq ... in general.

It is certainly true, that just as in Absorption, the battery charge current depends upon the Vabs (or Veq), AND Acceptance of the battery. Increase the Vabs (or Veq), and the measured battery current will increase, and taper over a period of time.

Just my observations, FWIW, Vic

Photowhit · June 2017

It might just be end of life drama, but if the battery is accepting 25 amps, I doubt it is getting fully charged. I don't know the size of the battery bank, but from your profile, it's between 200 and 460 ah. so 25 amps represents >5% charge rate. I think I get about a 20 ah into my @660 Ah battery at the beginning of equalizing and I've got a pretty bad cell in it.

I think Marc has already said, the charge controller really only increases the charging voltage to allow the current to flow into the battery. The current is regulated by what the battery will accept.

Equalization current for flooded batteries questions

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