no need to equalize if batteries cycled hard?

Discussion about OutBack Inverters in Grid Tie Applications

Moderators: OutBack, OutBack Moderator Team

Post Reply
User avatar
Megunticook
Forum Guru
Posts: 241
Joined: Fri Sep 29, 2017 4:08 am
My RE system: 6.4 kW solar array (21 QCell 305 panels in strings of 3)
GS8048A FLEXpower Radian (Radian 8048A, 2 FlexMax 80 cc's, Mate 3s, FlexNet DC, Hub)
8x6v Rolls-Surette 550 FLA batteries, 428AH
Location: Maine
Contact:

no need to equalize if batteries cycled hard?

Post by Megunticook » Sun Jan 12, 2020 11:14 am

Based on some conversations with a tech at Rolls-Surette, I'm under the impression that I don't need to equalize my FLA batteries necessarily if they are cycled hard regularly (down to 70% SOC and good stiff current to recharge). Is this true?

I'm in my second year with my batteries and am not even half-way through the break-in period (50-60 cycles according to Rolls). They stay on float most days. Decided to step up my occasional maintenance charging cycles to weekly in order to avoid sulfation and stratification. Today for the first time I charged them with the maximum amount of current recommended by Rolls for my setup (82 amps, or 20% of 20-hour AH rating. Temperature rose almost ten degrees Celsius but nowhere near what's considered "hot" (maxxed out at 16 degrees C).

If I do this weekly, will that stir up the electrolyte enough to prevent stratification and keep the plates from sulfating? Or should I also do an occasional EQ as well?
https://sunnypower.org

raysun
Forum Emperor
Posts: 2101
Joined: Tue Jul 26, 2016 5:57 am
My RE system: Flexpower One: FX3048T, (2) FM80, MATE3s, FlexNetDC
Outback 200NC batteries (8 @ 48v)
Outback IBR3 battery enclosure
Suniva 330 watt panels (12 - 6 strings of 2 in series)
Hyundai 355 watt panels (6 - 3 strings of 2 in series)
Honda EU7000is gas fuel generator

Re: no need to equalize if batteries cycled hard?

Post by raysun » Sun Jan 12, 2020 12:30 pm

The Rolls-Surette guidance is if the individual cells' specific gravity varies by 0.030 or more on a normally charged battery, run an EQ.

Regular workout for the battery (robust discharge and robust charge) is more likely to keeps the SG's in line.

User avatar
Megunticook
Forum Guru
Posts: 241
Joined: Fri Sep 29, 2017 4:08 am
My RE system: 6.4 kW solar array (21 QCell 305 panels in strings of 3)
GS8048A FLEXpower Radian (Radian 8048A, 2 FlexMax 80 cc's, Mate 3s, FlexNet DC, Hub)
8x6v Rolls-Surette 550 FLA batteries, 428AH
Location: Maine
Contact:

Re: no need to equalize if batteries cycled hard?

Post by Megunticook » Mon Jan 13, 2020 4:28 am

I don't really have a good way to discharge them hard (unless I run my well pump continuously for a few hours!) but I can push max current into them either using the grid via the inverter charger or waiting until the sun is up high so the array can put out 5kW or more.

So I take it this process stirs up the electrolyte to prevent stratification? And the plates shed any accumulated sulfation?
https://sunnypower.org

raysun
Forum Emperor
Posts: 2101
Joined: Tue Jul 26, 2016 5:57 am
My RE system: Flexpower One: FX3048T, (2) FM80, MATE3s, FlexNetDC
Outback 200NC batteries (8 @ 48v)
Outback IBR3 battery enclosure
Suniva 330 watt panels (12 - 6 strings of 2 in series)
Hyundai 355 watt panels (6 - 3 strings of 2 in series)
Honda EU7000is gas fuel generator

Re: no need to equalize if batteries cycled hard?

Post by raysun » Mon Jan 13, 2020 6:13 am

Megunticook wrote:
Mon Jan 13, 2020 4:28 am
I don't really have a good way to discharge them hard (unless I run my well pump continuously for a few hours!) but I can push max current into them either using the grid via the inverter charger or waiting until the sun is up high so the array can put out 5kW or more.

So I take it this process stirs up the electrolyte to prevent stratification? And the plates shed any accumulated sulfation?
Yes, it will help maintain proper battery chemistry to apply charging current, during Bulk, of about 13% of the C20 AH capacity. For a 400AH battery, roughly 50A. If using a higher charging current in high ambient temperature, be mindful of battery temperature (as you are when putting the 80+A Bulk charge into the battery.)

I'm not a personal fan of Bulk charging above the 13% rate unless the manufacturer specifically requires it. IME, higher charging rates raise the internal impedance and terminal voltage too fast. Reaching Absorb voltage at SoC = 85% is about right.

The cycle that really stirs things up is Absorb. This phase is a controlled overcharge that executes when the battery chemistry has changed enough to cause a marked rise in voltage. During Absorb, the charge being forced into the battery increases the off-gassing. The bubbles stir the electrolyte. This is also when a good deal of Lead Sulfate is broken apart. The activity also causes a bit of corrosion to the grids in the battery, which are generally protected by inclusion of calcium as an anti-corrosive. Watch the Absorb cycle for the time needed to reduce charge current to 1%-3% of C20 AH capacity. When the charged return amps reach this level, Absorb has done its job.

The corrosive action of overcharge is more pronounced during EQ, so use that charging cycle only when needed.

Post Reply