BULK = ABSORB = FLOAT?

[sigp2101]

How do I set up BULK = ABSORB = FLOAT?
I am getting ready to winterize my system so I want to turn my controller into constant voltage constant power for the duration of short winter sun hours.
The strategy here is to top up my batteries and leave them on trickle charge for the duration of a few months in order to extend BB lifespan.

Thanks!

[FNG]

I think what you are asking is how do you set absorb and float to the same value?

I assume you are lowering absorb down as you wouldn't want float raised for the winter.

To set voltages press main menu repeatedly until charge is highlighted and press enter
Scroll to volts and press enter
Scroll across and change what you want, Press enter to save and you will see data sent and saved.
Press status once


Now that said if it where me I would use skip days so the battery still gets a full charge once every X days, personally I set skip days on my seasonal cabin systems to 14 days this trickles them for 14 days and does a full absorb charge once every 2 weeks.

[sigp2101]

I can't set float to be same as absorbing. It is always lower than absorbing value by default.
If I set ABSORB to 10V Float drops down to 9.9, for example. The controller will not let me set it to the same values.
Then there are no BULK values setting.

Now that said if it where me I would use skip days so the battery still gets a full charge once every X days, personally I set skip days on my seasonal cabin systems to 14 days this trickles them for 14 days and does a full absorb charge once every 2 weeks.

What happens if there is no sun that day? I didn't know that skipping days puts the controller into trickle charge mode. Where are settings for that?

[ClassicCrazy]

I can't set float to be same as absorbing. It is always lower than absorbing value by default.
If I set ABSORB to 10V Float drops down to 9.9, for example. The controller will not let me set it to the same values.
Then there are no BULK values setting.

Now that said if it where me I would use skip days so the battery still gets a full charge once every X days, personally I set skip days on my seasonal cabin systems to 14 days this trickles them for 14 days and does a full absorb charge once every 2 weeks.

What happens if there is no sun that day? I didn't know that skipping days puts the controller into trickle charge mode. Where are settings for that?

What kind of battery are you charging ?  10 volts is too low for any common 12v battery . The typical float for a 12v flooded  lead acid battery would be over 13 volts like maybe 13.2 or bit higher  - check with battery manufacturer recommendations - will be different for AGM sealed batteries .

You may want to read this for some info
https://www.emarineinc.com/Marine-Batteries-Maintenance-101

Larry

[Vic]

I can't set float to be same as absorbing. It is always lower than absorbing value by default.
If I set ABSORB to 10V Float drops down to 9.9, for example. The controller will not let me set it to the same values.
Then there are no BULK values setting.

Now that said if it where me I would use skip days so the battery still gets a full charge once every X days, personally I set skip days on my seasonal cabin systems to 14 days this trickles them for 14 days and does a full absorb charge once every 2 weeks.

What happens if there is no sun that day? I didn't know that skipping days puts the controller into trickle charge mode. Where are settings for that?

Hi sign..,

Even if the Float and Absorb voltages are different by 0.10 volts,   this is no big deal.

With the Classic (and most good Charge Controllers (CCs),   there is NO Bulk voltage setting.   We all just use the Absorb voltage setting.

Use,   Charge>Advanced>Skip days,   to set the number of desired Skip Days.   On a Skip day,   the CC starts in Float-MPPT.   When there is enough PV power (and the batteries have been charged a bit),   the Classic will switch to Float.   The CC will remain in Float for the rest of the day,  until there is too little PV power (or too much load on the system)  to maintain the Vflt.   At this point,  the CC will show Float-MPPT.

Float  is the setting that will try to keep a fully-charged battery,  fully-charged.   This is your Trickle charge setting.

If there is too little PV power to reach Vflt,   when using Skip Days,   the CC  will begin Skipping Days again,  on the following day (there is no Make Up for this day that has too little PV Power to reach Vflt).

Some folks,   in Northern climes,   orient their PV modules at,   or very near perfectly vertical during Winter.   This allows good snow shedding,   and is appropriate for the low Sun angle.

Does any of this make sense?    FWIW,   Vic

[ClassicCrazy]

Vic,
I just tipped my panels up today because we are supposed to get up to 4 inches of snow tonight. As you say - makes it easy to clear the snow -  just touch the top with the broom and often all the snow will avalanche down .  Fun too !

Larry

[sigp2101]

Thanks gents, what I am trying to accomplish for the duration of winter months is a trickle charge them, and was confused about how to go about doing that.

[FNG]

Well if your goal is to charge at a constant voltage any time the sun is up set Absorb for the voltage you want and set absorb time to 18 hours. That way it will always charge at absorb voltage.

That said if these are lead-acid batteries this seems like a bad idea, I suspect you will see significant sulfation with several months of constant under charge

[sigp2101]

Well if your goal is to charge at a constant voltage any time the sun is up set Absorb for the voltage you want and set absorb time to 18 hours. That way it will always charge at absorb voltage.

That said if these are lead-acid batteries this seems like a bad idea, I suspect you will see significant sulfation with several months of constant under charge

Why that approach would be better than killing batteries by cycling them every day? As far as I know, we can trickle charge them indefinitely once they are fully charged.

[ClassicCrazy]

Well if your goal is to charge at a constant voltage any time the sun is up set Absorb for the voltage you want and set absorb time to 18 hours. That way it will always charge at absorb voltage.

That said if these are lead-acid batteries this seems like a bad idea, I suspect you will see significant sulfation with several months of constant under charge

Why that approach would be better than killing batteries by cycling them every day? As far as I know, we can trickle charge them indefinitely once they are fully charged.

Research battery electrolyte stratification. My understanding is that  if flooded lead acid batteries are not cycled occasionally the acid in the electrolyte can stratify - separate into layers so with low acid on parts of the plate then they can sulfate which is not good. A vigorous charge cycle every so often gets the electrolyte to mix up so that it does not stratify over time . I believe that is the way it goes.
So instead of just leaving them in float all the time you want to give them a long absorb cycle every so often  - I have seen 10 days suggested before - and that will help. One solution may be to set automatic equalize every 10 days using Absorb setpoints. 

Larry

[FNG]

Some batteries are made for constant float charge and some are not, Typically if they where purchased for off grid they would not like constant float. Say a rolls flooded or a trojan flooded they will be damaged by doing a constant float. In these two examples I would set up skip days for some range between 14 and 21 days this way they dont cycle daily but they do get absorbed every x many days.

What I would suggest is calling your battery manufacturer and ask them there opinion

[sigp2101]

I can't set float to be same as absorbing. It is always lower than absorbing value by default.
If I set ABSORB to 10V Float drops down to 9.9, for example. The controller will not let me set it to the same values.
Then there are no BULK values setting.

Now that said if it where me I would use skip days so the battery still gets a full charge once every X days, personally I set skip days on my seasonal cabin systems to 14 days this trickles them for 14 days and does a full absorb charge once every 2 weeks.

What happens if there is no sun that day? I didn't know that skipping days puts the controller into trickle charge mode. Where are settings for that?

Hi sign..,

Even if the Float and Absorb voltages are different by 0.10 volts,   this is no big deal.

With the Classic (and most good Charge Controllers (CCs),   there is NO Bulk voltage setting.   We all just use the Absorb voltage setting.

Use,   Charge>Advanced>Skip days,   to set the number of desired Skip Days.   On a Skip day,   the CC starts in Float-MPPT.   When there is enough PV power (and the batteries have been charged a bit),   the Classic will switch to Float.   The CC will remain in Float for the rest of the day,  until there is too little PV power (or too much load on the system)  to maintain the Vflt.   At this point,  the CC will show Float-MPPT.

Float  is the setting that will try to keep a fully-charged battery,  fully-charged.   This is your Trickle charge setting.

If there is too little PV power to reach Vflt,   when using Skip Days,   the CC  will begin Skipping Days again,  on the following day (there is no Make Up for this day that has too little PV Power to reach Vflt).

Some folks,   in Northern climes,   orient their PV modules at,   or very near perfectly vertical during Winter.   This allows good snow shedding,   and is appropriate for the low Sun angle.

Does any of this make sense?    FWIW,   Vic

Thanks for your input. It make sense.
Like I said, i just wont to fully charge my BB and leave it unattended for 5.5 months. During this time will be up to CC and panels to maintain my BB. All I want is gentle charge not cycling every day charge (when there is sun on the sky). It is very hard to program any logic into CC when weather is so unpredictable. Just looking for best possible strategy based on experience of others for my case scenario. Remote off grid cabin alone for 5.5 months.

[sigp2101]

In these two examples I would set up skip days for some range between 14 and 21 days this way they don't cycle daily but they do get absorbed every x many days.

I like that idea as well. But what happens if on that particular day there is no sun on the sky?

Thanks!

[Vic]

In these two examples I would set up skip days for some range between 14 and 21 days this way they don't cycle daily but they do get absorbed every x many days.

I like that idea as well. But what happens if on that particular day there is no sun on the sky?
Thanks!

Hi sigp..,

When using Skip Days,   and there is little or no PV power production,   there is little or no battery charging.   The following day,   the Classic will again Skipping Days  --  it does not keep attempting to do a full charge on successive days.

BUT,   Flooded Lead Acid (FLA) Deep Cycle  batteries are very forgiving.   Perfection  is generally not required.   Good enough charging and discharges are generally good enough.

You do need to Cycle your batteries,   as this is what deep cycle FLAs were designed to do.

Think that you have gotten some very good advice here from FNG and Larry.

Generally,   it is best for the health of most FLA deep cycle batteries,   to not frequently recharge them until their State Of Charge (SOC) is 90% or lower.    Again this is a general term,   one need not be perfect in this sense either.

On the other hand,   IMO,   it is generally better to err on the side of  overcharging these batteries,   than to regularly undercharge them.

Hope that you will have a chance to try different numbers of Skip Days to find the approximate "correct number" of days before vacating your site.

Assume that you will be leaving the cabin due to harsh Winter conditions.   Cooler temperatures will reduce the amount of Self Discharge of the batteries,   which can mean that you should be able to Skip more days,  than if the bank was at a higher average temperature.

As you know  FLA batteries that are not at a fairly high SOC can be subject to FREEZING,  which would destroy that battery bank.

If you have some idea of the lowest temperatures that the battery bank will experience,   this will help,  at least a bit.

Of course,   you will want your inverter to be switched (as in disconnected) from the battery while you are away from the cabin.

EDIT:  Also,  you may wish to go to the WInd-Sun Forum to ask for added info on what others do to keep their batteries healthy during long absences,   at their Northern latitude locations (assumed on my part):
https://forum.solar-electric.com/

FWIW,   Vic

[FNG]

I can't set float to be same as absorbing. It is always lower than absorbing value by default.
If I set ABSORB to 10V Float drops down to 9.9, for example. The controller will not let me set it to the same values.
Then there are no BULK values setting.

Now that said if it where me I would use skip days so the battery still gets a full charge once every X days, personally I set skip days on my seasonal cabin systems to 14 days this trickles them for 14 days and does a full absorb charge once every 2 weeks.

What happens if there is no sun that day? I didn't know that skipping days puts the controller into trickle charge mode. Where are settings for that?

Hi sign..,

Even if the Float and Absorb voltages are different by 0.10 volts,   this is no big deal.

With the Classic (and most good Charge Controllers (CCs),   there is NO Bulk voltage setting.   We all just use the Absorb voltage setting.

Use,   Charge>Advanced>Skip days,   to set the number of desired Skip Days.   On a Skip day,   the CC starts in Float-MPPT.   When there is enough PV power (and the batteries have been charged a bit),   the Classic will switch to Float.   The CC will remain in Float for the rest of the day,  until there is too little PV power (or too much load on the system)  to maintain the Vflt.   At this point,  the CC will show Float-MPPT.

Float  is the setting that will try to keep a fully-charged battery,  fully-charged.   This is your Trickle charge setting.

If there is too little PV power to reach Vflt,   when using Skip Days,   the CC  will begin Skipping Days again,  on the following day (there is no Make Up for this day that has too little PV Power to reach Vflt).

Some folks,   in Northern climes,   orient their PV modules at,   or very near perfectly vertical during Winter.   This allows good snow shedding,   and is appropriate for the low Sun angle.

Does any of this make sense?    FWIW,   Vic

Thanks for your input. It make sense.
Like I said, i just wont to fully charge my BB and leave it unattended for 5.5 months. During this time will be up to CC and panels to maintain my BB. All I want is gentle charge not cycling every day charge (when there is sun on the sky). It is very hard to program any logic into CC when weather is so unpredictable. Just looking for best possible strategy based on experience of others for my case scenario. Remote off grid cabin alone for 5.5 months.

In my case I professionally installed and maintain around 2-300 systems, I have several off grid cabins using lead acid batteries and what I do is set the skip days to 14 and have never had any issues, Water useage is acceptable and never had any issues