Thanks Larry.
The information to stop when absorb voltage was reached is like, 10 or
more years old and so I
don't know if that voltage reach and stop charging algorithm is still
used by any BMS's.
This is probably why we had to add a logic input to tell the controller
to stop charging from the BMS.
After the 0.3 hours at Absorb for balancing (which makes perfect sense
for a BMS), does the MX/FM then
go to float at 3.65V per cell after that ?
Does your systems just restart a new bulk/absorb cycle the next morning
or do you also do a Re-Bulk if
or when battery voltage falls below a certain point ?
Also, listening (reading) chat here on what might be needed that may not
have been addressed by
Li battery, BMS and/or charge controller manufacturers.
Thanks,
boB
On 12/1/2021 12:03 PM, larrycrutcher wrote:
If you stop charging a Li-ion battery when the CV (absorb voltage) is
reached, you may reduce or stop the needed cell balancing time. We
have had customers develop unbalanced series cells from continuous
undercharging. Because of internal cell resistance, one cell will
always reach saturation before others in the group. This can happen at
less than 1mv difference. The more unbalanced a group of series cells
are, the sooner one cells voltage will spike causing over voltage
events at a lower terminal voltage.
Our Li batteries (Elite Power Solutions-GBS and LiFeBlue) can be held
at 3.65Vpc continuously, no problems. We have customers using both MX
and FM controllers for 8 years now. Our recommended setting for the
Absorb timer is 0.3 hours. This allows for cell balancing and for the
capacity meter to recalibrate. Some chargers will stay at CV for
several hours. No problems doing this either as long as cell voltage
is lower than 3.8V (LFP chem.).
Larry Crutcher
Starlight Solar Power Systems
On Dec 1, 2021, at 9:38 AM, b...@midnitesolar.com wrote:
Depends on the requirement for the BMS.
Usually, but not 100% always, the requirement is to get the voltage up
to "absorb" and then stop charging.
Just set the min and max times very low, like 1 minute and that
should satisfy that one.
I do not remember if the MX60 had a Re-Bulk setting but I think it did ?
The MX did not have a logic input for turning it on and off of
course. OB had a communications
device that converted their communications protocol to Modbus or
Ethernet I think it was which
may (or may not) be able to make it work.
Could always buy something newer and keep the MX60 as a spare.
boB
On 12/1/2021 9:10 AM, frenergy wrote:
boB,
Interesting...Sounds like this is not a candidate for
L-ion batteries.
Bill
On 11/30/2021 10:47 PM, b...@midnitesolar.com wrote:
Hi Bill....
As I remember, the min is of course... Minimum time in Absorb.
Max is maximum time in absorb but depended on how long it took to
get from Bulk MPPT to that Absorb voltage.
So if it took 3 hours to get to Absorb that morning and you had t
set for Max 2 hours, it would Absorb for 2 hours.
If it only took 1 and 1/2 hours to reach Absorb voltage, the MX60
would Absorb for 1 and 1/2 hours.
It worked "OK" but these days I would probably just set it for min
of some 2 or 3 hours and then a max could be the same
time or longer for FLA batteries.
boB
On 11/30/2021 7:16 PM, frenergy wrote:
Yes, the old one, not the FM. This oldie had an interesting way to
set the absorption time. You would set the "min" time (in minutes)
and you would set the "max" time (in hours, you have to set it to
1,2,3 or 4 hours).
I need to know if I set the "min" to 10 minutes and the
"max" time to one hour or two or three or four, how long will it
stay in absorb?
I called Outback and Megan there didn't know how this
old fart works, apparently tech support isn't supporting us their
old relics.
Bill
Feather River Solar Electric
Bill Battagin, Owner
4291 Nelson St.
Taylorsville, CA 95983
530.284.7849
CA Lic 874049
solar powered since 1982
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