Best practices for off grid battery life?

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grunt
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Best practices for off grid battery life?

Post by grunt » Mon Jun 29, 2020 5:14 pm

I have a 48 volt 980ah (20hr) forklift battery, the charging parameters from the manufacturer are as follows.
Float 53.04
Bulk 55.2 2hr
Eq 63.36 1hr
My system comprises of a Radian 8048 with 3 fm80's and roughly 11.2 k of panels. Fully off grid
Here is my question on a daily cycle my system goes through its 3 phases bulk, absorb and then float. The mate 3 display reads 100% at the end of the absorb phase and goes in to float. Now once it is in float the battery indicator slowly works its way down even in full sun. I would guess the reason for this is the DNC is set to read the voltage that the absorb voltage is the topped off voltage as fully charged. Yesterday we had a lot of morning cloud cover and it was a day I had to equalize, so it took longer in the day to get it done, but because of this the battery voltage was higher going in to the night time and consequently the morning battery indicator voltages were higher. Which means I did not draw my battery down as much during the night. Sooo..what is the best practices should I set a rebulk option. Should my DNC be set to a float voltage? I would like to keep the battery at 100% untill the loss of sun vs now, once they get done with the absorb cycle at noon they just tick down from 100% and we enter the evening mid to low 90%. Thoughts?

raysun
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Re: Best practices for off grid battery life?

Post by raysun » Mon Jun 29, 2020 5:53 pm

grunt wrote:
Mon Jun 29, 2020 5:14 pm
I have a 48 volt 980ah (20hr) forklift battery, the charging parameters from the manufacturer are as follows.
Float 53.04
Bulk 55.2 2hr
Eq 63.36 1hr
There's a lot going on in this post. I'm going to start with the first chunk.

Is this a flooded lead acid battery, or a sealed battery? I'm guessing the latter.

The charging voltages and times seem unusual for such a big capacity, heavy-duty battery.

Bulk 55.2V @ 2hr. I assume this is the Absorb voltage and time. Correct?

Float 53.04V The manufacturer actually specifies the voltage to 4 hundredths? Not many chargers are going to be capable of such precision.

EQ 63.36V Over 8V above Absorb for such a short EQ time sounds like a desulfating cycle.

Of course the manufacturer is authoritative.

What is the manufacturer and model of the battery?

By DNC, do you mean FNDC (FLEXNet DC) battery monitor?

grunt
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Re: Best practices for off grid battery life?

Post by grunt » Mon Jun 29, 2020 8:58 pm

It is a GB forklift battery that is sold in banks of 6 2 volt cells for solar applications. So it is wet cell. Yes I do mean the fndc. The charging cycles are figure by adding up the requirements of each bank.

grunt
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Re: Best practices for off grid battery life?

Post by grunt » Mon Jun 29, 2020 9:06 pm

You can see all the model numbers and components by clicking on my profile. The equalization cycle is used for desulfication and is recommended to be done every 5 days.

grunt
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Re: Best practices for off grid battery life?

Post by grunt » Mon Jun 29, 2020 9:22 pm


raysun
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Re: Best practices for off grid battery life?

Post by raysun » Mon Jun 29, 2020 9:28 pm

grunt wrote:
Mon Jun 29, 2020 5:14 pm

Here is my question on a daily cycle my system goes through its 3 phases bulk, absorb and then float. The mate 3 display reads 100% at the end of the absorb phase and goes in to float. Now once it is in float the battery indicator slowly works its way down even in full sun. I would guess the reason for this is the DNC is set to read the voltage that the absorb voltage is the topped off voltage as fully charged. Yesterday we had a lot of morning cloud cover and it was a day I had to equalize, so it took longer in the day to get it done, but because of this the battery voltage was higher going in to the night time and consequently the morning battery indicator voltages were higher. Which means I did not draw my battery down as much during the night. Sooo..what is the best practices should I set a rebulk option. Should my DNC be set to a float voltage? I would like to keep the battery at 100% untill the loss of sun vs now, once they get done with the absorb cycle at noon they just tick down from 100% and we enter the evening mid to low 90%. Thoughts?
The FNDC doesn't use voltage to derive state of charge. It calculates it from the battery AH capacity, amount of current flowing into and out of the battery, and the battery charge factor. It does use a voltage setting (Charged Voltage) to determine when the charge parameters are met.

Once the battery reaches Float, the chargers should keep it at the Float voltage. If not, you might check that the charge controllers are calibrated to the battery voltage. Also, enable Float Coordination on the Mate.

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Re: Best practices for off grid battery life?

Post by fcwlp » Mon Jun 29, 2020 10:18 pm

grunt wrote:
Mon Jun 29, 2020 9:22 pm
4 of these
https://gb-battery.com/products/ols/pro ... ery-module
I found that also when searching for your p/n. However, I can find no information on charging parameters. Some info on equalization cycles for forklift type apps that are not hopefully not applicable to solar (i.e., an equalization cycle every 10 charging cycles).

raysun
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Re: Best practices for off grid battery life?

Post by raysun » Tue Jun 30, 2020 2:22 am

fcwlp wrote:
Mon Jun 29, 2020 10:18 pm
grunt wrote:
Mon Jun 29, 2020 9:22 pm
4 of these
https://gb-battery.com/products/ols/pro ... ery-module
I found that also when searching for your p/n. However, I can find no information on charging parameters. Some info on equalization cycles for forklift type apps that are not hopefully not applicable to solar (i.e., an equalization cycle every 10 charging cycles).
With an indirect specification of a 3 hour EQ charge time.

The scenario described stated it better for cycle life to discharge the battery 80% before recharging, rather than daily cycles. I believe it also suggests frequent EQ charges because of the deep discharge.

It also advised against "opportunity charging".

Another suggestion I didn't quite follow is the charger should be rated at C20AH - 100A. In this case 938 - 100 = 838A. I don't understand that, or if I even read it right. It did mention the typical advice against too low charge current leading to sulfation and short service life.

All the above is in reference to the battery in a forklift application. They do mention Solar application has different considerations but don't reference them.

I'd suggest contacting the company for concise charging instructions for the battery in off-grid usage and daily cycling.

grunt
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Re: Best practices for off grid battery life?

Post by grunt » Tue Jun 30, 2020 6:33 am

The charge cycles I posted are not located on the website and were a email I received from tech support. Should the FNDC be calibrated to float representing 100%? Or should it be calibrated to the state of the battery after it has met its absorb requirements?

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Re: Best practices for off grid battery life?

Post by provo » Tue Jun 30, 2020 6:34 am

raysun wrote:
Tue Jun 30, 2020 2:22 am

Another suggestion I didn't quite follow is the charger should be rated at C20AH - 100A. In this case 938 - 100 = 838A. I don't understand that, or if I even read it right.
I didn't see that part, but I saw this: "Charge Rate Recommended -- Min/Max charging amps: 55 - 125 Amps."

Wow, that's a big battery! And heavy ...

grunt
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Re: Best practices for off grid battery life?

Post by grunt » Tue Jun 30, 2020 7:25 am

Another question I have, is on the mate 3 screen, on the screen used for setting up the charging parameters. It has a current limit and then a section labeled as "Absorb End Amps" the default for this is "0" . What should this be set to?

raysun
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Re: Best practices for off grid battery life?

Post by raysun » Tue Jun 30, 2020 9:12 am

grunt wrote:
Tue Jun 30, 2020 7:25 am
Another question I have, is on the mate 3 screen, on the screen used for setting up the charging parameters. It has a current limit and then a section labeled as "Absorb End Amps" the default for this is "0" . What should this be set to?
Absorb End Amps on the FX80s should be set to 0.

The FNDC can control charge termination for all the controllers by proper setting of the Charged Return Amps parameter, which is typically set at 2%-3% of the C20 AH value.

raysun
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Re: Best practices for off grid battery life?

Post by raysun » Tue Jun 30, 2020 9:22 am

grunt wrote:
Tue Jun 30, 2020 6:33 am
The charge cycles I posted are not located on the website and were a email I received from tech support. Should the FNDC be calibrated to float representing 100%? Or should it be calibrated to the state of the battery after it has met its absorb requirements?
That's not how the FNDC works to determine state of charge.

Charge the battery per the manufacturers instructions. Once you are sure they are at 100% State of Charge, perhaps by measuring the specific gravity of the electrolyte, synchronize the FNDC by unplugging it from the Hub, waiting a few seconds, then plugging it back in. It will power up assuming the battery is at 100% SoC.

From that point, the FNDC will "count charge" by tracking the current flowing into, and out of, the battery. The SoC will be continuously calculated by the net current flow.

Did the vendor give you a Charge Efficiency specification for the battery?

Did they provide an End Amps (Charged Return Amps) spec?

The settings in the FNDC Battery Charging page (here taken from OpticsRE) determine both battery State of Charge, and the values that satisfy Charged Parameters Met:
20200630_084257.jpg
I'm speculating the proper settings for the battery here.

Battery AH: 980 - the C20 AH capacity

Charged Voltage: The voltage that must be reached to assume battery is charged fully. 0.4V below Absorb is the usual recommendation.

Charged Time: The time Charged Return Amps is to be held.

Charged Return Amps: The net charge current that indicates the end of the Absorb phase. Usually 2-3% of C20 capacity.

Charge Factor: The battery charging efficiency. If 100AH is removed from a full battery, and 115AH of charge is needed to return it to full, the Charge Factor would be 85%.

provo
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Re: Best practices for off grid battery life?

Post by provo » Tue Jun 30, 2020 12:39 pm

Actually, if this is your battery,

https://gb-battery.com/products/ols/pro ... ery-module

the 20h capacity is 938Ah, not 980Ah.

raysun
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Re: Best practices for off grid battery life?

Post by raysun » Tue Jun 30, 2020 2:55 pm

provo wrote:
Tue Jun 30, 2020 12:39 pm
Actually, if this is your battery,

https://gb-battery.com/products/ols/pro ... ery-module

the 20h capacity is 938Ah, not 980Ah.
Oh right. I saw that earlier. My eye landed on 980 in another post. 938AH

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Re: Best practices for off grid battery life?

Post by chinezbrun » Wed Jul 01, 2020 10:16 am

hello guys, interesting topic :)

My battery bank is lead acid tubular floated 48v 375AH C5 - semi traction(forklift), heavy duty one.
My objective is to prolong as much as possible the life of the battery.

I contacted manufacturer, to have the recommendation for charging and i received this curves:
IUIA.JPG
or
Wa.JPG
I was wondering about this 2.65v at the end, and i called them. They said "don't worry" these traction batt should reach an intense gassing stage at the end to have a good charge and avoid acid stratification problems.

So, this profile: constant current till 2.45v (let say bulk), then constant voltage 2.45v (absorption) then again constant current until 2.65v is reached i was not able to do it with FM80 :)

I was trying for several months to find out the best charging setting for it.
This is my final setup:
In the morning i have the battery at 75-80% SOC
then

Bulk phase: max 10 to 55Amp - around 2-3 hours till absorption
Absorption: 2.45v/cell, 2h or return amp 7 Amp for 20 min - absorption is ending after ~100 min and then goes to float
Floating: 2.35 v / cell for proper topping till end of the day

@ the end of the day SG is ~ 1.285-1.290 you can hear very small gassing

Question one: do you believe that is enough? I'm planning to set also an equalization at every 5 day to go to the famous 2.65v/cell
Question two: should i go to 60% SOC? will be better for the health of the battery -- I'm wondering if this being a traction battery, should be discharged more.

Thanks.
D.

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Re: Best practices for off grid battery life?

Post by fcwlp » Wed Jul 01, 2020 10:46 am

FWIW I have not worked with traction batteries but it is a FLA battery. A traction battery may have thicker plates and more electrolyte but it is still a FLA battery.

An absorption voltage of 2.45V/cell or 58.8V for a 48V system is a very typical number. Since you are daily getting to a S.G. of 1.285 to 1.290 you are doing a good job of charging the battery on a daily basis. I would not recommend going to a deeper DOD as every battery manufacturer that publishes DOD vs cycles specs shows a substantial increase in number of cycles for shallower DODs.

Equalization is required when the specific gravity of the cells vary by more than a specified amount, which depends on the battery manufacturer. The Rolls battery manual recommends equalizing when the cells vary by more than 0.025-0.030. Other manufacturers typically say x number of days or months. When I asked Trojan tech support about their every 30 day recommendation, he said that was for those people who did not measure the S.G. For those who measure S.G. it is when the cells vary by >0.030.

An equalization voltage of 2.65V/cell or 63.6V for a 48V system is a very typical number. I would never do an equalization every five days, as equalization will reduce battery life if done excessively. Since you are getting to a good S.G. on a daily basis, I would check on a monthly basis initially and equalize if you see >0.025 between cells or every couple of months if it makes you feel better.

chinezbrun
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Re: Best practices for off grid battery life?

Post by chinezbrun » Wed Jul 01, 2020 12:18 pm

thanks.
I will try to monitor on monthly basis SG then i will decide on preventive equilibration

grunt
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Re: Best practices for off grid battery life?

Post by grunt » Wed Jul 08, 2020 2:43 pm

raysun wrote:
Tue Jun 30, 2020 2:55 pm
provo wrote:
Tue Jun 30, 2020 12:39 pm
Actually, if this is your battery,

https://gb-battery.com/products/ols/pro ... ery-module

the 20h capacity is 938Ah, not 980Ah.
Oh right. I saw that earlier. My eye landed on 980 in another post. 938AH

yes it is 938ah , typo .
I thank you for the input on the presets but my problem still persist, let me see if I can explain it better. When I lived at my last house we had a grid tied system that was a xantrex 6048 with a battery backup. When the power would go out during times of sun. The system made enough to ramp up for the momentary a.c. Loads and still keep the battery at float. If we had a cloud of no sun, the battery would provide the power and then when the cloud would leave the the system would top off the battery and normally have enough to offset whatever a.c. Loads we may had during the cycle. That is how I want this system to work but right now the only time I can throw a.c. loads on and know they are not going to draw the battery down ( according to the mate3) is if I run the load during the charging cycle. If the charging cycle is met by 10 am in the morning that means by 10:05 I will be at 99% and by solar noon I will be around 95%. Its like the system does not produce or allow the usage of the 11.2 k of solar panels I have for the a.c. loads after the float cycle is met. Now if I change the system to equalize then all of a sudden my charger controllers produce gobs of juice and keep the battery at 100% . What was a system barley producing 2 k to keep the batteries at float now jumps up to its full capacity. I want the system to open up and handle what ever incoming a.c. loads I have and keep the battery at 100% as long as I have ample sun. Right now it throttles its self back to the point it can't do either once the float is met.

provo
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Re: Best practices for off grid battery life?

Post by provo » Wed Jul 08, 2020 4:10 pm

grunt wrote:
Wed Jul 08, 2020 2:43 pm

If the charging cycle is met by 10 am in the morning that means by 10:05 I will be at 99% and by solar noon I will be around 95%. Its like the system does not produce or allow the usage of the 11.2 k of solar panels I have for the a.c. loads after the float cycle is met.
I saw something similar once in very hot weather. I was supposed to be in float, but the batteries kept discharging. It turned out that the temperature compensated float voltage was too low to keep current flowing into the batteries -- I turned up the float voltage a couple tenths of a volt, and the current into the batteries rose to the usual 0.6V, and the inverter handled the loads as well.

It was very weird, I've only seen it once, and I don't claim to understand it, but check the current into (or out of) your batteries once they go into float, and see if the current is positive into the batteries. You may have too low a float voltage setpoint.

raysun
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Re: Best practices for off grid battery life?

Post by raysun » Wed Jul 08, 2020 4:21 pm

provo wrote:
Wed Jul 08, 2020 4:10 pm
grunt wrote:
Wed Jul 08, 2020 2:43 pm

If the charging cycle is met by 10 am in the morning that means by 10:05 I will be at 99% and by solar noon I will be around 95%. Its like the system does not produce or allow the usage of the 11.2 k of solar panels I have for the a.c. loads after the float cycle is met.
I saw something similar once in very hot weather. I was supposed to be in float, but the batteries kept discharging. It turned out that the temperature compensated float voltage was too low to keep current flowing into the batteries -- I turned up the float voltage a couple tenths of a volt, and the current into the batteries rose to the usual 0.6V, and the inverter handled the loads as well.

It was very weird, I've only seen it once, and I don't claim to understand it, but check the current into (or out of) your batteries once they go into float, and see if the current is positive into the batteries. You may have too low a float voltage setpoint.
Interesting observation.

FWIW, my battery Temperature Compensation is Limited: Low=53.5V, High=58V. Float=54V.

grunt
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Re: Best practices for off grid battery life?

Post by grunt » Wed Jul 08, 2020 4:43 pm

provo wrote:
Wed Jul 08, 2020 4:10 pm
grunt wrote:
Wed Jul 08, 2020 2:43 pm

If the charging cycle is met by 10 am in the morning that means by 10:05 I will be at 99% and by solar noon I will be around 95%. Its like the system does not produce or allow the usage of the 11.2 k of solar panels I have for the a.c. loads after the float cycle is met.
I saw something similar once in very hot weather. I was supposed to be in float, but the batteries kept discharging. It turned out that the temperature compensated float voltage was too low to keep current flowing into the batteries -- I turned up the float voltage a couple tenths of a volt, and the current into the batteries rose to the usual 0.6V, and the inverter handled the loads as well.

It was very weird, I've only seen it once, and I don't claim to understand it, but check the current into (or out of) your batteries once they go into float, and see if the current is positive into the batteries. You may have too low a float voltage setpoint.

interesting. I will try that, I have the compensation set to wide, is that a ok default? I will check with the float voltage a bit. Just to make sure if the arrow is pointing up on the batt on the mate 3 that means current is going in right?

grunt
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Re: Best practices for off grid battery life?

Post by grunt » Wed Jul 08, 2020 4:52 pm

provo wrote:
Wed Jul 08, 2020 4:10 pm
grunt wrote:
Wed Jul 08, 2020 2:43 pm

If the charging cycle is met by 10 am in the morning that means by 10:05 I will be at 99% and by solar noon I will be around 95%. Its like the system does not produce or allow the usage of the 11.2 k of solar panels I have for the a.c. loads after the float cycle is met.
I saw something similar once in very hot weather. I was supposed to be in float, but the batteries kept discharging. It turned out that the temperature compensated float voltage was too low to keep current flowing into the batteries -- I turned up the float voltage a couple tenths of a volt, and the current into the batteries rose to the usual 0.6V, and the inverter handled the loads as well.

It was very weird, I've only seen it once, and I don't claim to understand it, but check the current into (or out of) your batteries once they go into float, and see if the current is positive into the batteries. You may have too low a float voltage setpoint.

interesting I will try that, the temp compensation is set to the default wide and we stay about 80 to 70 degrees. I will try bumping up the voltage slowly and see how it adjust.

raysun
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Re: Best practices for off grid battery life?

Post by raysun » Wed Jul 08, 2020 5:15 pm

Are you using Float Coordination Enable on the Mate?

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My RE system: Sixteen Evergreen EC-120
(4 strings, total 1920W)
Eight Rolls S-550 (2 strings, total ~800Ah @ 24V)
One FM80
One VFXR3524A
Hub 10
Mate3s
FNDC and Trimetric
Location: Sierra foothills

Re: Best practices for off grid battery life?

Post by provo » Wed Jul 08, 2020 5:24 pm

raysun wrote:
Wed Jul 08, 2020 4:21 pm

FWIW, my battery Temperature Compensation is Limited: Low=53.5V, High=58V. Float=54V.
Yeah, my setpoint is still at the Rolls recommended 27.0, but I raised my Compensation lower limit to 26.6. On the Wide setting it was getting down to 26.4, and that wasn't enough to keep the battery current going in.

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