Winter battery charging at cottage

[Bob D]

Our system is unused for 3-4 months in the winter.
I leave the system on to make sure the battery is charged to avoid freezing.
I have the controller adjusted so that the absorb and float voltages are close together, to minimize the time in absorb.

However, I think a better solution would be to leave the battery alone for a few days, allowing the self-discharge to occur until a voltage of, say, 24.5V is reached ( nominal 24V system), then let the controller run through a normal bulk--absorb-float cycle, then wait again until the low voltage is reached.

This can be accomplished with a couple of relays and using the Aux 1 and Aux 2 outputs.
Simplifying a bit, use Aux 1 Vent Fan Lo set to close at 24.5V to connect the PV panels to the charge controller.  Then use Aux 2 Float High to disconnect the PV panels when the charge cycle is complete, at which point the PV panels will stay disconnected until Vb drops to 24.5 again.

Is there any reason not to do this when the system is idling for a few months?
Anyone see any problems?

[dgd]

I suppose it depends on how many days it takes your fully charged battery to discharge down to 24.5v
If the weather is freezing and there is no PV input to allow the Classic to bulk charge, when AUX1 switches in the PVs, then will the battery V at 24.5v continue to drop to the freezing point?
You could be starting a period of bad/freezing weather with a 24.5V battery instead of a 26v (or whatever) battery.
or is that an unlikely scenario?
dgd

[vtmaps]

However, I think a better solution would be to leave the battery alone for a few days, allowing the self-discharge to occur until a voltage of, say, 24.5V is reached ( nominal 24V system), then let the controller run through a normal bulk--absorb-float cycle, then wait again until the low voltage is reached.

Welcome to the forum.

I think you are correct that your battery will be better off not being absorbed every day, but there's got to be a better way to do it.  How about setting absorb equal to float voltage, and set an auto equalization to occur once a week (set the EQ voltage to your absorb voltage). 

I recall that forum member Chris Olsen inquired about this... he thought that using the rebulk setting would do the trick if he turned off autoRestart, but it doesn't work that way.  The Classic resets every night and wants to start the new day in bulk.

--vtMaps

[Halfcrazy]

what I would do is this.

Set days between Bilk charges to say 14
Set ReBulk for a safe number. Say 24.4 ish?
Set EndAmps for 1-2% of the AH capacity of the battery
Set Float slightly lower than normal by say 3-4 tenths

This will basically just maintain a float (Lower than normal) charge for 14 days or until the battery falls to 24.4 and then it will do a new bulk and absorb charge

Ryan

[Bob D]

Ryan, what you propose accomplishes what I outlines without adding any hardware, but i thought I read somewhere that the days between bulk charges is a one-time setting that sets itself to zero after executing.
I can't find where I read that so it may be incorrect.
Does the days between bulk timer restart once a bulk and absorb is executed?

[vtmaps]

what I would do is this.

Set days between Bulk charges to say 14
Set ReBulk for a safe number. Say 24.4 ish?
Set EndAmps for 1-2% of the AH capacity of the battery
Set Float slightly lower than normal by say 3-4 tenths

Another great feature I didn't know about!  Is the ability to set 'days between bulk' a new feature?  I just reread the manual and didn't see it mentioned.

--vtMaps

[vtmaps]

Ryan, what you propose accomplishes what I outlines without adding any hardware, but i thought I read somewhere that the days between bulk charges is a one-time setting that sets itself to zero after executing.
I can't find where I read that so it may be incorrect.
Does the days between bulk timer restart once a bulk and absorb is executed?

maybe here:  http://midniteforum.com/index.php?topic=1197

--vtMaps

[Resthome]

Ryan, what you propose accomplishes what I outlines without adding any hardware, but i thought I read somewhere that the days between bulk charges is a one-time setting that sets itself to zero after executing.
I can't find where I read that so it may be incorrect.
Does the days between bulk timer restart once a bulk and absorb is executed?

Ryan/boB..  I was going to ask the same question about the days between bulk setting. I'm not at the boat so can say this for sure I only tested it once to see what it would do and I wasn't there long enough after this feature was added to ready see what does happen after it hits zero. I know it counted down to zero (0). Are you saying after it hits zero and does the bulk/absorb the days between bulk setting would reset to 14 days in your example. Perfect if it does ask I am in the same situation as Bob D and would love to see this functionality be repeatable.

Thanks

[Resthome]

what I would do is this.

Set days between Bulk charges to say 14
Set ReBulk for a safe number. Say 24.4 ish?
Set EndAmps for 1-2% of the AH capacity of the battery
Set Float slightly lower than normal by say 3-4 tenths

Another great feature I didn't know about!  Is the ability to set 'days between bulk' a new feature?  I just reread the manual and didn't see it mentioned.

--vtMaps

It was in the Read Me file for the last firmware update.

[zoneblue]

Days between bulk was added in 1609, so technically still beta.

Hopefully theyll add it to the local app soon so i can try it out.

[Resthome]

Days between bulk was added in 1609, so technically still beta.

Hopefully theyll add it to the local app soon so i can try it out.

REV 1609/1608 Production Firmware for Windows  10/4/2013 

[Resthome]

From the ReadMe Change.txt file for firmware 1609


   Bulk/Absorb can now skip a preset number of days up to 380 days.

New EndAmps menu item selects number of days to skip a new Bulk/Absorb cycle.
   A selection of zero (0) days is the same as "Disabled".  The number of days
   the Classic is waiting until the next Bulk/Absorb is displayed below the
   programmed number of days to wait.  When this number is NOW= 0, the next
   morning will initiate a new Bulk/Absorb cycle.

[Resthome]

Ryan, what you propose accomplishes what I outlines without adding any hardware, but i thought I read somewhere that the days between bulk charges is a one-time setting that sets itself to zero after executing.
I can't find where I read that so it may be incorrect.
Does the days between bulk timer restart once a bulk and absorb is executed?

maybe here:  http://midniteforum.com/index.php?topic=1197

--vtMaps

Or it could be my observation on a quick test  http://midniteforum.com/index.php?topic=1412.msg12339#msg12339

Hopefully Ryan or boB can set us straight on this functionality. I for sure didn't test it for more that 1 day to skip to see that it did go to Float and then when it reached 0 it went to Bulk/Absorb. I then had to leave so made sure the feature was disabled. According to my wife it would not be the first time I was wrong about something. 

[Halfcrazy]

Yes "Days between Bulk" is in 1609 firmware and that is now considered Production Firmware. Yes Days between bulk is a re occurring thing so once the timer expires it will finish a bulk charge and reset the timer to start the process over. This was driven by Surrette and Chris Olsen and I see it as a VERY useful tool. Especially when combined with the WBjr so you have true End amps etc.

Ryan

[Halfcrazy]

From the ReadMe Change.txt file for firmware 1609


   Bulk/Absorb can now skip a preset number of days up to 380 days.

We changed it from 380 days to 30 days as I was afraid some one may set it for to long of a period. If the consensus is it should be longer we can accommodate that?

Ryan