equalize with 2 FlexMax 80s?

Discussion about the FM100, FM80, and FM60 Charge Controllers

Moderators: OutBack, OutBack Moderator Team

equalize with 2 FlexMax 80s?

Postby Megunticook on Mon Jul 02, 2018 1:00 pm

I just tried tried to perform my first battery equalization and it didn't go so well.

I have 2 FlexMax 80s and a Radian 8048A, grid-tie with battery backup. Normally during the day the two charge controllers are working in tamden, cranking out maximum power at float voltage and selling excess to the grid.

I tried putting them into EQ mode and raising the sell voltage up to 62, and at first they seemed like they were working, but they wouldn't stay there very long, seemed like one would go into "charged" mode after about a minute and stop drawing any current, and then eventually both would shut down. I tried several times before giving up and returning back to GT mode.

Can the two work together in EQ? Ideally, I'd like to do continue selling excess power while equalizing, but I"m wondering if maybe they can't work together like they do in GT Mode.

Any ideas or suggestions welcome.
https://sunnypower.org
User avatar
Megunticook
Forum Guru
 
Posts: 167
Joined: Fri Sep 29, 2017 4:08 am
Location: Maine
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

Re: equalize with 2 FlexMax 80s?

Postby Kurt Lundquist on Mon Jul 02, 2018 2:04 pm

What was the EQ voltage target? If you want to EQ at the 62V sell voltage the CC's should be shooting for 64V EQ target. To sell and EQ at the same time you will have to manually stop the EQ cycle unless you have way more PV than your inverter can sell. Are you sure both FM80s were in EQ mode?

Was your inverter able to keep the battery voltage at the sell target?

-Kurt
Kurt Lundquist
Renewable Energy Project Engineer
http://alphaenergy.us/
User avatar
Kurt Lundquist
Alpha Energy Engineering
 
Posts: 1245
Joined: Tue May 31, 2011 7:23 am
Location: Arlington, WA
My RE system: VFX3524, Mate3, 200Ah 24V AGM Battery Bank

Re: equalize with 2 FlexMax 80s?

Postby Megunticook on Mon Jul 02, 2018 6:59 pm

What was the EQ voltage target?

62.4

But the first time I tried it I had sell at 60 and the charge controllers just seemed really confused about the situation. I also tried bumping sell up slowly bit by bit to see if it would stabilize but the current readings in the CCs kept jumping around eventually and then one and/or both of them would shut down to 0 current.

I tried it again a couple of times and just couldn't get the charge controllers to settle in and work together. At one point I saw MPPT EQ in the status display, then I think I just saw EQ.

Seems like the system ought to run just like in GT Mode except about 8 volts higher. Maybe the inverter doesn't want that much voltage to convert? is the system designed to do this?
https://sunnypower.org
User avatar
Megunticook
Forum Guru
 
Posts: 167
Joined: Fri Sep 29, 2017 4:08 am
Location: Maine
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

Re: equalize with 2 FlexMax 80s?

Postby Kurt Lundquist on Tue Jul 03, 2018 8:12 am

Megunticook wrote:Seems like the system ought to run just like in GT Mode except about 8 volts higher. Maybe the inverter doesn't want that much voltage to convert? is the system designed to do this?


I do not know if OB tested selling power while the FM's are in EQ mode but I can see that the GS8048A can have a sell target as high as 64Vdc. The FM80s can charge as high as 80Vdc so in theory, the charge targets vs sell target allow for selling at an EQ voltage. I think the problem is at the EQ voltage I would guess that your battery is not as stiff of a voltage source. By this I mean it would be very easy for your inverter to pull down the battery voltage too fast for the charge controllers to respond. Once the batteries drop below the sell target the inverter stops selling and FM's are trying their hardest to bring the battery voltage back up. The end result is the battery voltage shoots past the FM charge target so they stop charging.

To help limit selling power you can set the Grid AC input to 5Aac (~1200W). If that can stabilize you can try bumping up the AC input amps to allow for more selling. Setting one of your FM80s to a higher target than the other one might help as well. If it is a cloudy day or you have intermittent shade issues I don't think it will work out very well. I would plan on keeping a close eye on the system during the EQ cycle. Watching the system is especially important if some of your charge target settings are beyond a safe limit for your battery bank.

Please follow up and let us know how it goes if you try again.

Thanks,

-Kurt
Kurt Lundquist
Renewable Energy Project Engineer
http://alphaenergy.us/
User avatar
Kurt Lundquist
Alpha Energy Engineering
 
Posts: 1245
Joined: Tue May 31, 2011 7:23 am
Location: Arlington, WA
My RE system: VFX3524, Mate3, 200Ah 24V AGM Battery Bank

Re: equalize with 2 FlexMax 80s?

Postby Megunticook on Sun Jul 08, 2018 4:11 am

I'm trying a new approach this morning. Shortly after the inverters woke up, and they were in MPPT Bulk Mode, I put both in EQ and figure maybe I can get a 2-hour EQ in before the high-productivity hours later in the day. Wondering if the system will hold off on selling until the EQ is over. If not, I'll have to disable the offset.

Still not clear whether Outback designed this system for selling during EQ. Would love to hear a definitive answer to that, as that would be the ideal scenario for me.
https://sunnypower.org
User avatar
Megunticook
Forum Guru
 
Posts: 167
Joined: Fri Sep 29, 2017 4:08 am
Location: Maine
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

Re: equalize with 2 FlexMax 80s?

Postby Megunticook on Sun Jul 08, 2018 5:44 am

Total failure again. Tried every variation I could come up with and I cannot get the charge controllers to stabilize at the correct voltage. No matter what, whenever they're in EQ mode and approach the target voltage the array current keeps swinging wildly and voltage swings also from about 56 to 62.

Now trying plan B--bumped up my float voltage setting on the charge controllers to 63.6, and sell voltage at 62.4. Put the charge controllers in GT mode, and things have stabilized. Excess current is being sold.

I guess this will work, but I'm curious what's wrong with the EQ mode on the charge controllers.
https://sunnypower.org
User avatar
Megunticook
Forum Guru
 
Posts: 167
Joined: Fri Sep 29, 2017 4:08 am
Location: Maine
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

Re: equalize with 2 FlexMax 80s?

Postby Kurt Lundquist on Mon Jul 09, 2018 7:51 am

The Mate3 and Inverters do not have a Sell during EQ setting nor is there any literature on it that I know of so I can 99% guarantee that OB didn't design the system to sell while doing an EQ.

I'm glad you were able to work something out by using Float/GT mode. The GT mode operation allows for better communication between the inverters and the charge controllers. If you would like to know more about it OutBack has a write up on GT mode here http://www.outbackpower.com/downloads/documents/appnotes/fm_gt_mode_app_note.pdf.

Thanks for the follow-up!

-Kurt
Kurt Lundquist
Renewable Energy Project Engineer
http://alphaenergy.us/
User avatar
Kurt Lundquist
Alpha Energy Engineering
 
Posts: 1245
Joined: Tue May 31, 2011 7:23 am
Location: Arlington, WA
My RE system: VFX3524, Mate3, 200Ah 24V AGM Battery Bank

Re: equalize with 2 FlexMax 80s?

Postby Megunticook on Wed Jan 02, 2019 8:42 am

It's been 6 months since my last EQ, these batteries mostly sit fully charged (I've done 3 discharge/recharge cycles in those six months), and I'm ready to do another EQ. Battery manufacturer(Rolls) says to equalize every 60-180 days, or when the s.g. of cells varies by more than .025-.030.

When taking specific gravity readings last night I noticed a slight drop, from a range of 1.290-1.275 when brand new (1 year ago) to now ranging from 1.290-1.260 (electrolyte at 0 degrees C). My battery manufacturer says 1.255-1.275 is 100% SOC (1.240-1.260 adjusted for temperature).

Last time I EQ'd I sold power simultaneously (which is how this thread started). Seemed to work fine once I settled on a workaround method.

But am I risking damage to the battery bank by doing this? Rolls says to keep current at 5-10% of C20 during EQ, which in my case means 43 amps max. This morning, at about an hour before solar noon, I've got 89 amps flowing (selling to grid). Should I wait until later this afternoon when the amperage drops?

I could just EQ using the grid at night (or stop selling during EQ), just figured it would be most economical to do it with solar power during the day especially if I can sell excess current while EQ'ing. But don't want to be stupid about it and risk my battery bank.

Thanks for any advice on this.
https://sunnypower.org
User avatar
Megunticook
Forum Guru
 
Posts: 167
Joined: Fri Sep 29, 2017 4:08 am
Location: Maine
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

Re: equalize with 2 FlexMax 80s?

Postby Kurt Lundquist on Wed Jan 02, 2019 8:56 am

89 amps on the DC bus does not necessarily mean the battery bank is taking 89 amps. Once the batteries are at the EQ voltage they will only charge with however many amps is necessary to maintain the voltage set point. The other amps are turned into AC by the inverter for loads/selling. I would not be concerned unless you are exceeding the charge voltage target.

-Kurt

PS: If you only have 1 shunt on your FN-DC you can see how many amps are going to the battery bank when you are selling during EQ.
Kurt Lundquist
Renewable Energy Project Engineer
http://alphaenergy.us/
User avatar
Kurt Lundquist
Alpha Energy Engineering
 
Posts: 1245
Joined: Tue May 31, 2011 7:23 am
Location: Arlington, WA
My RE system: VFX3524, Mate3, 200Ah 24V AGM Battery Bank

Re: equalize with 2 FlexMax 80s?

Postby Megunticook on Wed Jan 02, 2019 9:12 am

Thanks--I have 3 shunts. Right now on OpticsRE in the FNDC data it reads:

Shunt A: -91.9
Shunt B: 39.8
Shunt C: 53.4

Since the bank is fully charged, does that mean most of those amps are effectively "bypassing" the bank and going right to the inverter? Meaning I can safely EQ as long as I keep an eye on the voltage?

The Radian is set to shut things down if voltage exceeds 64--is that sufficient protection or could damage happen before the shutdown kicks in?
https://sunnypower.org
User avatar
Megunticook
Forum Guru
 
Posts: 167
Joined: Fri Sep 29, 2017 4:08 am
Location: Maine
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

Re: equalize with 2 FlexMax 80s?

Postby Megunticook on Fri Jan 11, 2019 6:18 am

Rereading the Radian manual I saw that the system is designed to allow selling during equalization.

From page 43:

"The Radian inverter can perform Offset when equalizing. Equalize voltage is also the reference voltage for Offset during equalization."
https://sunnypower.org
User avatar
Megunticook
Forum Guru
 
Posts: 167
Joined: Fri Sep 29, 2017 4:08 am
Location: Maine
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


Return to FLEXmax Charge Controllers

Who is online

Users browsing this forum: Google [Bot] and 2 guests