Author Topic: Lithium charge cutout with Classic  (Read 367 times)

bigal

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Re: Lithium charge cutout with Classic
« Reply #15 on: October 07, 2018, 09:42:42 AM »
I've done more reading from group of early lifepo4 users in Australia. To prolong cell life, they finally adopted a charging plan that shuts off charge at preset voltage near 3.45 volts (HVD).  When cells drop to 3.3, bulk charging is resumed.

No system that used a form of float voltage was successful LONG TERM. These batteries are not tolerant of being kept at or near 100% charge . It shortens the number of charge cycles.

This brings me back to my original premise of disconnecting the Classic at a preset voltage, and reconnecting at a lower voltage.

This could occur multiple times a day.

I'd like the Midnite Brains to comment on the wisdom of the using a Classic in this manner!! Am I going to have problems?  How could I safely do this??
« Last Edit: October 07, 2018, 01:55:14 PM by bigal »
27-235 watt Canadian panels, 2 CLASSICS,  Magnum Inverter,  Forklift Battery,  powers entire house easily.
Lots of sun here, recharge by 1 pm normally. 2 Fujitsu mini splits for summer AC.  13 solar thermal panels for heat.

FNG

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Re: Lithium charge cutout with Classic
« Reply #16 on: October 10, 2018, 05:09:09 PM »

Simple question, if I use a solenoid disconnect, will Classic tolerate a quick disconnect without damage? Charging current would be low, perhaps 10amps@48v

I have had battery bank disconnected from a Classic when in bulkmppt charging. No problems and the classic  continued to power an AC inverter. On another system when a battery breaker tripped the Classic again suffered no ill effects and with nowhere for output current to flow to the PV input current just dropped to near zero.
Dgd

Correct, The classic couldnt care if the battery goes away it will just set in absorb or float and power itself from the pv. if a sweep is forced it will of course then drop out do to 0 amps during the sweep but it will not hurt anything at all

australsolarier

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Re: Lithium charge cutout with Classic
« Reply #17 on: October 14, 2018, 01:51:28 AM »
bigal, it seems to me to you are still a bit confused.  HVD disconnects the battery via a breaker or relay. (to protect the battery from being overcharged.

in the midnite classic you can set the max voltage that it ever permits. and low. it has nothing to do with bulk and float settings. or HVD or LVD.

my bulk setting is 56V. end amp 8A. so in the morning it charges to at max 56V and then tapers out. after end amp kicks in, the midnite switches to float and keeps it there abouts at 53.6V.

you will have to adjust the voltage that the midnite shows with a good quality volt meter. (in the menu, they have excellent manuals) and then it might  still be out a tenth of a volt or so. that does not seem much for lead acid batteries, but it is much for lithium. in my case to absorb at 56, one midnite classic is programmed to 56.2V,, the float for 53.6, is programmed 53.7. it then DOES float and absorb in the demanded voltages) (after the voltages have been adjusted.)

generally you should not have a low voltage disconnect. i am not usually going underneath 60% SOC. but i have tested down to 10% with both systems. the large 400ah system did trigger a programmable disconnect. now,  a low voltage disconnect should only happen when there is none or little solar input anyway. it is the last of the defenses, before the battery will be destroyed. in my opinion, a disconnect should not harm the midnite classic. there are 10s of thousands of midnite classics out there and it is the least of the problems or questions thrown up. similar say you have a 10kw inverter running at full capacity and turn off a switch to disconnect a 10kw load. should just turn off without problem.
 

Ron Swanson

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Re: Lithium charge cutout with Classic
« Reply #18 on: October 14, 2018, 11:35:53 AM »
Are you doing all this with the BTS disconnected or what?