[RE-wrenches] Outback MX-60 - Li-ion charging

Wed Dec 1 15:24:38 EST 2021

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, bob at 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, bob at 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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