Absorb and bulk times

[sigp2101]

Hi sigp..,

The required Absorb for the battery depends upon how deeply-discharged the battery happens to be.   This is a variable.

End Amps from the Classic might be able to do a good job managing the end of Absorb,  but,  without the WBjr and a Shunt,  the Classic's EA function  (where Absorb can be ended by the current that the CC providing to the battery AND any loads)  will use all of the current being provided to the battery,  and all loads on the battery  (inverter,  and any direct DC loads).

If your loads on the battery are fairly constant during the time that the Classic is near the end of Absorb,  or if the loads are fairly constant,  and a larger load is intermittent,  CC EA (without WB & Shunt),  can still work fine.

The EA function relies on the fact that as batteries become fully-charged,  the amount of current that the battery needs tapers.  When this tapering battery current diminishes to a value where the rate of change is quite small,  Absorb can be terminated.

You can set a Maximum Absorb time in the Charge> Time menu.   This max time will end the Absorb,  even if the EA current value that you have entered in the Advanced menu has not be been reached.

With Flooded batteries (FLA),  the SGs can be checked,  and any small error is the EA setting can be compensated for by changes in Absorb voltage.

The Shunt + WBjr is an inexpensive option for the Classic,  and seems to me to be well worth the small additional cost.   This option will allow a more accurate termination of the Absorb stage,  using Shunt EA.

This might be a bit too much detail at this point ...

FWIW,   Vic

Huh, OK, I have to digest all this info first. Your contribution I highly appreciated.

SIGP2101

[russ_drinkwater]

Have two more whiz bang's in the mail.
$326 for the 2 including postage. But that is cheaper than the $400 plus dollars to get them locally!
Splitting my 2 classic 150's between 2 battery banks has killed off my follow me plans.
Next job is the build a covered enclosure for the last lot of batteries.

[sigp2101]

Hi sigp2101,

Very few Solar CCs have a Bulk voltage setting.   So,  would set the Absorb voltage to 44.5 V.

Good Luck,  Vic

I was watching videos last night and it was mentioned in one of them that Classic's Absorb = Bulk. That is rather interesting because in the same videos customers are often instructed to consult with manufacturers data for various settings.

Here is instructions from Trojan for example on how to properly recharge their batteries.

Voltage 6 Volt 8 Volt 12 Volt 24 Volt 36 Volt 48 Volt
Bulk Charge (2.47 VPC) 7.4 9.9 14.8 29.6 44.5 59.3
Absorption Charge (2.35 â€" 2.45 VPC) 7.05 â€" 7.35 9.4 â€" 9.8 14.1 â€" 14.7 28.2 â€" 29.4 42.3 â€" 44.1 56.4 â€" 58.8
Finish Charge (2.70 VPC) 8.1 10.8 16.2 32.4 48.6 64.8
Equalize Charge (2.70 VPC) 8.1 10.8 16.2 32.4 48.6 64.8
Float Charge (if desired 2.25 VPC) 6.75 9.0 13.5 27 40.5 54

So according to Trojan we have 5 different charge regimes and our classics offers only two/three. That is what confuses me a most. So Bulk and Absorption voltages are pretty close and that takes care of that but Finish and Float are significantly different. This is all very important for longevity of our systems  and how to properly set those values is question I am struggling to find the answer.

[Resthome]

Hi sigp2101,

Very few Solar CCs have a Bulk voltage setting.   So,  would set the Absorb voltage to 44.5 V.

Good Luck,  Vic

I was watching videos last night and it was mentioned in one of them that Classic's Absorb = Bulk. That is rather interesting because in the same videos customers are often instructed to consult with manufacturers data for various settings.

Here is instructions from Trojan for example on how to properly recharge their batteries.

Voltage 6 Volt 8 Volt 12 Volt 24 Volt 36 Volt 48 Volt
Bulk Charge (2.47 VPC) 7.4 9.9 14.8 29.6 44.5 59.3
Absorption Charge (2.35 â€" 2.45 VPC) 7.05 â€" 7.35 9.4 â€" 9.8 14.1 â€" 14.7 28.2 â€" 29.4 42.3 â€" 44.1 56.4 â€" 58.8
Finish Charge (2.70 VPC) 8.1 10.8 16.2 32.4 48.6 64.8
Equalize Charge (2.70 VPC) 8.1 10.8 16.2 32.4 48.6 64.8
Float Charge (if desired 2.25 VPC) 6.75 9.0 13.5 27 40.5 54

So according to Trojan we have 5 different charge regimes and our classics offers only two/three. That is what confuses me a most. So Bulk and Absorption voltages are pretty close and that takes care of that but Finish and Float are significantly different. This is all very important for longevity of our systems  and how to properly set those values is question I am struggling to find the answer.

Some Mfg show/call the Equalize set point Finish as you can see they are the same. I would not recommend that you Equalize (Finish)your batteries after every charge cycle. More like once a month or less unless the S/G between cells a far apart. Normal operation is it go from Absorb to Float.  Bulk is max current required to achieve Absorb voltage set point. The voltage is held constant in Absorb while the current will decline. End Amps is the absorb current where it flattens out and does not drop any farther this is the point where you should go to float an maintain float voltage. You need a WBjr and shunt attached to use End Amps.

[sigp2101]

Some Mfg show/call the Equalize set point Finish as you can see they are the same. I would not recommend that you Equalize (Finish)your batteries after every charge cycle. More like once a month or less unless the S/G between cells a far apart. Normal operation is it go from Absorb to Float.  Bulk is max current required to achieve Absorb voltage set point. The voltage is held constant in Absorb while the current will decline. End Amps is the absorb current where it flattens out and does not drop any farther this is the point where you should go to float an maintain float voltage. You need a WBjr and shunt attached to use End Amps.

Thanks for your input, really appreciated.

[Vic]

sigp2101 said,   "So according to Trojan we have 5 different charge regimes and our classics offers only two/three. That is what confuses me a most. So Bulk and Absorption voltages are pretty close and that takes care of that but Finish and Float are significantly different. This is all very important for longevity of our systems  and how to properly set those values is question I am struggling to find the answer"

Those types of battery charge profiles are for Grid Charging,  and are often used for batteries that are used on Floor Scrubbers,  Forklifts,  etc.   Charging from Renewable Energy (RE) power sources is generally much different.

You have Trojan batteries,  what is the exact model number of the battery?

You should probably try to contact Trojan,  for specific charge instructions for charging them from RE power sources,  like from PVs.

With the model number of your batteries,  we can probably find some good info on-line,  but would help if you tried to also get that info from Trojan.

Agree with John,  that,  generally you will not want to use that Finish charge,  on every charge cycle.

Regarding using EA without the WBjr and a Shunt,  this works quite well on systems with relatively constant loads,  and for systems that also have varying loads that cycle,  and will remain off for five or so minutes  --  like fridges,  freezers,  A/Cs,  etc.

.   Have used CC EA for many,  many years ...  really have NEVER used a fixed Absorb time.   But if the system has completely out-of-control,  large loads (ie with several others in a household running vacuums,  hair driers/curlers,  large pumps and so on),  then CC EA (without the WBjr)  is probably not a good approach.

Thanks,   more later,   Vic

[sigp2101]

sigp2101 said,   "So according to Trojan we have 5 different charge regimes and our classics offers only two/three. That is what confuses me a most. So Bulk and Absorption voltages are pretty close and that takes care of that but Finish and Float are significantly different. This is all very important for longevity of our systems  and how to properly set those values is question I am struggling to find the answer"

Those types of battery charge profiles are for Grid Charging,  and are often used for batteries that are used on Floor Scrubbers,  Forklifts,  etc.   Charging from Renewable Energy (RE) power sources is generally much different.

You have Trojan batteries,  what is the exact model number of the battery?

T-105 T2 technology

You should probably try to contact Trojan,  for specific charge instructions for charging them from RE power sources,  like from PVs.

I will eventually.

With the model number of your batteries,  we can probably find some good info on-line,  but would help if you tried to also get that info from Trojan.

Agree with John,  that,  generally you will not want to use that Finish charge,  on every charge cycle.

Regarding using EA without the WBjr and a Shunt,  this works quite well on systems with relatively constant loads,  and for systems that also have varying loads that cycle,  and will remain off for five or so minutes  --  like fridges,  freezers,  A/Cs,  etc.

.   Have used CC EA for many,  many years ...  really have NEVER used a fixed Absorb time.   But if the system has completely out-of-control,  large loads (ie with several others in a household running vacuums,  hair driers/curlers,  large pumps and so on),  then CC EA (without the WBjr)  is probably not a good approach.

Thanks,   more later,   Vic

This CC EA you talking about is so far away from me at this point, I am slowly chewing this up. One weekend at the time. Thank you for your tremendous support. More questions coming in separate thread.

[Vic]

Hi sigp..,

Thanks for adding a Signature,  and for the model number of batteries and the inverter size.

You said,   "...   This CC EA you talking about is so far away from me at this point, I am slowly chewing this up. One weekend at the time. Thank you for your tremendous support. More questions coming in separate thread   ...   "

The Classic can End Absorb,  based on the output current of the Classic,  WITHOUT the WBjr and Shunt.   I call this CC EA,  (as opposed to Shunt EA).  This can work fine,  if your larger loads cycle on and off,  and are off for about five minutes or more per cycle.

Will look for charge parameters for that model of Trojan T-105.

It seems that  the running load from your fridge is not excessive.  An unknown,  presently,  is the idle load from your inverter.   This inverter idle load can be fairly substantial in a 24 hour period.  If you were looking at running the fridge 24/7 in your absence,  this could possibly be a bit of a concern,  without you being there to monitor your battery SOC.

Do you have the Idle,  or Tare power (or current) consumption of the inverter,  a Link to a data sheet for it,  or perhaps the brand and model number for it?

Thanks,    Vic

[sigp2101]

Hi sigp..,

Thanks for adding a Signature,  and for the model number of batteries and the inverter size.

You said,   "...   This CC EA you talking about is so far away from me at this point, I am slowly chewing this up. One weekend at the time. Thank you for your tremendous support. More questions coming in separate thread   ...   "

The Classic can End Absorb,  based on the output current of the Classic,  WITHOUT the WBjr and Shunt.   I call this CC EA,  (as opposed to Shunt EA).  This can work fine,  if your larger loads cycle on and off,  and are off for about five minutes or more per cycle.

I would not mind at all using that feature if you say is good one. But I do not know much about it. What it is, what it does, and how to program it into Classic. My main concern on this small system is over or undercharging batteries.

Will look for charge parameters for that model of Trojan T-105.

Thanks!

It seems that  the running load from your fridge is not excessive.  An unknown,  presently,  is the idle load from your inverter.   This inverter idle load can be fairly substantial in a 24 hour period.  If you were looking at running the fridge 24/7 in your absence,  this could possibly be a bit of a concern,  without you being there to monitor your battery SOC.

Do you have the Idle,  or Tare power (or current) consumption of the inverter,  a Link to a data sheet for it,  or perhaps the brand and model number for it?

Thanks,    Vic

Idle load for inverter according to specs is 0.7A. It is Chinese made unit and it was custom made just for 36V. Price was right. Fridge and Inverter will be disconnected completely in unintended state. That is for now, first I have to learn system and gain confidence before I even start to experiment leaving things on one week the time. Winter months all will be definitely disconnected. Only BB will be connected to CC <=> PV.

[sigp2101]

Hi sigp..,


The Classic can End Absorb,  based on the output current of the Classic,  WITHOUT the WBjr and Shunt.   I call this CC EA,  (as opposed to Shunt EA).  This can work fine,  if your larger loads cycle on and off,  and are off for about five minutes or more per cycle.

Thanks,    Vic

OK I think I started to grasp the concept of this. What do I need to do to come up with EA number in order to take advantage of this possibility? My system will have no loads between weekends.

Thanks!

[boB]

Looks like you are getting great advice here, Sig...

I would add that Ending Amps AE works best when using the Whizbang Junior shunt sensor because then
it know what is going into and out of the battery and doesn't look at inverters and other chargers and loads
in the system.

There is also (in the newest  firmwares) an Absorb "Skip Days" feature  where  the Classic will do an Absorb
cycle every so often.  This is because an Absorb isn't absolutely necessary every single 24 hour period
and it "can" actually be harmful for longest battery life by hitting that high voltage too often.
Absorb is kind of like a mini EQ and helps to reduce sulfating.  I have heard that some batteries can
go  a month or more without an Absorb.  I do not really know what the optimum time or period
would be so the manufacturer should know.

boB

[sigp2101]

Looks like you are getting great advice here, Sig...

I would add that Ending Amps AE works best when using the Whizbang Junior shunt sensor because then
it know what is going into and out of the battery and doesn't look at inverters and other chargers and loads
in the system.

There is also (in the newest  firmwares) an Absorb "Skip Days" feature  where  the Classic will do an Absorb
cycle every so often.  This is because an Absorb isn't absolutely necessary every single 24 hour period
and it "can" actually be harmful for longest battery life by hitting that high voltage too often.
Absorb is kind of like a mini EQ and helps to reduce sulfating.  I have heard that some batteries can
go  a month or more without an Absorb.  I do not really know what the optimum time or period
would be so the manufacturer should know.

boB

Sure I do Bob, and I am grateful for that. This forum is a friendly bunch and all contributors are great. I feel like at home.
Summer was great as well and I had a chance to feel and experiment with my little system. I learned a lot. System is running my fridge, my lights and TV. Occasionally I can/can't run vacuum cleaner but that is another topic discussion.

Generally my system is 5 days recharge 2 days of use. During those 5 days there is absolutely no load on the system. During 2 days we do not use up even 1KWh daily. BB is fully charged every time I checked with hydrometer. I am happy, now it is time to find out how far I van push what I have. But there is still entire winter ahead of me.

[dapago]

There is also (in the newest  firmwares) an Absorb "Skip Days" feature  where  the Classic will do an Absorb
cycle every so often.  This is because an Absorb isn't absolutely necessary every single 24 hour period
and it "can" actually be harmful for longest battery life by hitting that high voltage too often.
Absorb is kind of like a mini EQ and helps to reduce sulfating.  I have heard that some batteries can
go  a month or more without an Absorb.  I do not really know what the optimum time or period
would be so the manufacturer should know.

boB

Trying to keep up with this post but You lost me here. Are you saying that absorb every day is a bad thing for batts life? How can the CC goes directly from bulk to float without passing through absorb? Doesn't the bulk voltaje higher than absorb? I have actually noticed something on my classic: voltaje rise when reaching absorb so maybe you are referring to that. Does that means that during absorb current is lower but voltaje is higher?

[Vic]

There is also (in the newest  firmwares) an Absorb "Skip Days" feature  where  the Classic will do an Absorb
cycle every so often.  This is because an Absorb isn't absolutely necessary every single 24 hour period
and it "can" actually be harmful for longest battery life by hitting that high voltage too often.
Absorb is kind of like a mini EQ and helps to reduce sulfating.  I have heard that some batteries can
go  a month or more without an Absorb.  I do not really know what the optimum time or period
would be so the manufacturer should know.

boB

Trying to keep up with this post but You lost me here. Are you saying that absorb every day is a bad thing for batts life? How can the CC goes directly from bulk to float without passing through absorb? Doesn't the bulk voltaje higher than absorb? I have actually noticed something on my classic: voltaje rise when reaching absorb so maybe you are referring to that. Does that means that during absorb current is lower but voltaje is higher?

Hi dapago,

For systems that have relatively large battery Capacity,  verses the average Depth Of Discharge (DOD),  doing a full recharge every day is not needed.  And,  generally,  there are only so many charge cycles that a battery will endure,  until end of life for the battery.

Also,  many batteries will do well with cycling between 50 or 60% State Of Charge (SOC) and let's say 85 - 90 % SOC,  with only several full recharges per week.

Some batteries will essentially never need a complete recharge.

So,  Skip days can help keep from depleting the number of rated discharge cycles, of  many battery types.

Many CCs,  like the Classic and KIDs have NO setting for Bulk voltage.  There IS an Absorb voltage setting.  The Bulk stage continues with the Renewable Energy (RE) power source providing maximum current available, until the Absorb voltage is reached.  At this point,  the Absorb stage begins.  Absorb continues until the set Absorb time setting is reached,  EA setting is reached,  or,  perhaps,  the CC reverts back to Bulk,  if there is insufficient RE power available to maintain the Absorb voltage.   When the set Absorb end point is reached,  the CC transitions to Float.

The Absorb voltage is regulated to the Absorb set point (but is usually compensated for the measured temperature of the battery via the BTS).  If the CC stays in Absorb,  the Absorb voltage will remain constant (except for changes in temp compensation when the battery temperature changes).

In Absorb,  the battery charge current DOES diminish as the battery charges.  Near the end of a full battery charge,  the rate of change in the battery charge current levels off,  and at some point,  simply stops diminishing.  This is usually considered to be the point where the battery is fully-charged.

In Absorb,  the only thing that would change battery charge voltage,  would be a change in battery temperature.

The battery charge current can most easily be measured by the WBjr and a Shunt.  Looking at the current from the CC can be misleading,  as this current display includes any/all loads on the battery,  usually all from loads on the inverter.

Vic

[dapago]

Hi Vic,
Reading your post meanwhile taking my morning coffee so be forgiving ;-).
I understand that batt have a cycle life but doesn't cycles rise depending on DOD?
In order to understand the skip day function, First I need to know how cycles are calculated.
If during a day with a load, batt charging pattern goes from absorb to float several times a day (from let say 80%SOC to 100% SOC), does that means every time batt goes from absorb to float it counts for 1 cycle or some kind of a portion of a cycle? From what I can see on the Trojan cycle curve, I understand that it should count for only a portion of a cycle and the skip absorb function is then  valid only when a minimum load is put on the batt, i.e. WE cabin