Batrium Low End Voltage & Questions

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May 6, 2017
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This may have been covered elsewhere, but how low of a voltage is it safe for your battery pack to get before you allow it to recharge?

My setup is 14s100p, charged from daylight to dusk with PCM60X mppt solar charger. Have a Schneider Conext SW4048 Inverter that can be used on or off grid. From daylight until dusk have turned OFF the AC grid support, and turn the AC grid support ON between 10 and 11 pm. Electricity is crazy cheap, like $0.015 per kWh between 11 pm and 7 am, so prefer NOT to allow battery pack charging from the grid except after 11 pm. Problem is that must physically flip a breaker switch to turn AC support ON or OFF.

Today was a cloudy day, and battery pack did not fully charge, so am running lowest pack at 3.4 v and highest pack around 3.6 volts right now...so how low can it go before it just shuts off? The cellmon setting in Batrium is set at low voltage of 2.90 volts, and this appears to be the default, as I have not changed it. So will it continue to discharge down to 2.9 v, and is that safe, or WAY too low.

Been watching it go down, and lights still on, but when should I pull the trigger and flip the switch??? Or should I just keep watching one night and see where it is when the lights turn off???


daromer said:
Ah that click. Can you pull them out again? If not... then they are in there :)

With a computer power supply you can power a DPS unit. They are killer things! They have a 20A unit that just is awesome! I did a video about it just days ago too if you check that out!


Very nice video. Got mine built and powering it with 12 volt computer power supply. Currently charging one of my lower voltage packs on the bench. Have it set to charge at 4.20 volts and 10 amps. Question is how long to charge, and is it safe just to let it run all night? Will it stop once the pack gets to the 4.20 volt level, and then stop? Or should I set it at 4.15 volts???
 

Korishan

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Charles Francis Speakman said:
This may have been covered elsewhere, but how low of a voltage is it safe for your battery pack to get before you allow it to recharge?

Quick answer: Desired voltage per cell * Number in Series. This is both top and bottom of the charge curve. So, if the bottom voltage per cell is 3.2V, then 3.2 * 14 = 44.8V.
3.2V is usually the preferred lower end per cell for standard Lithium Cobalt based cells (most laptop cells)
 

daromer

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Low end on 18650 depends on the chemistry inside. Some is 3V and some is as low as 2V... Generally for LiIon mixed packs i would say 2.8 is dead bottom but dont go below 3.2 because there is nothing to fetch.
 
Joined
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daromer said:
Low end on 18650 depends on the chemistry inside. Some is 3V and some is as low as 2V... Generally for LiIon mixed packs i would say 2.8 is dead bottom but dont go below 3.2 because there is nothing to fetch.

Thanks, makes sense. Set my AC support on inverter to charge with grid power when pack goes below 45 volts.


CharlesFrancisSpeakman said:
This may have been covered elsewhere, but how low of a voltage is it safe for your battery pack to get before you allow it to recharge?

My setup is 14s100p, charged from daylight to dusk with PCM60X mppt solar charger. Have a Schneider Conext SW4048 Inverter that can be used on or off grid. From daylight until dusk have turned OFF the AC grid support, and turn the AC grid support ON between 10 and 11 pm. Electricity is crazy cheap, like $0.015 per kWh between 11 pm and 7 am, so prefer NOT to allow battery pack charging from the grid except after 11 pm. Problem is that must physically flip a breaker switch to turn AC support ON or OFF.

Today was a cloudy day, and battery pack did not fully charge, so am running lowest pack at 3.4 v and highest pack around 3.6 volts right now...so how low can it go before it just shuts off? The cellmon setting in Batrium is set at low voltage of 2.90 volts, and this appears to be the default, as I have not changed it. So will it continue to discharge down to 2.9 v, and is that safe, or WAY too low.

Been watching it go down, and lights still on, but when should I pull the trigger and flip the switch??? Or should I just keep watching one night and see where it is when the lights turn off???


daromer said:
Ah that click. Can you pull them out again? If not... then they are in there :)

With a computer power supply you can power a DPS unit. They are killer things! They have a 20A unit that just is awesome! I did a video about it just days ago too if you check that out!


Very nice video. Got mine built and powering it with 12 volt computer power supply. Currently charging one of my lower voltage packs on the bench. Have it set to charge at 4.20 volts and 10 amps. Question is how long to charge, and is it safe just to let it run all night? Will it stop once the pack gets to the 4.20 volt level, and then stop? Or should I set it at 4.15 volts???


Charged one pack on bench all night set at 4.2 v 10 amps, and pack was up from 3.86 v to 4.13 v, so stopped charging. Worked great. Going to put it back into service, and pull out another slightly lower energy pack for testing. Looks like answered my own question via trial...
 

Redpacket

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Good call using the off peak power like that :)
If you're taking individual packs out to charge them, then putting them back & using the system before you've charged all the other packs, you're risking out of balance issues. Ie your wall might read say 48V & you're pulling power from it but one or more packs could be dropping well below the 3.2V min.
 
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Redpacket said:
Good call using the off peak power like that :)
If you're taking individual packs out to charge them, then putting them back & using the system before you've charged all the other packs, you're risking out of balance issues. Ie your wall might read say 48V & you're pulling power from it but one or more packs could be dropping well below the 3.2V min.

Knowing what I know now, probably would have only charged that pack up to 4 volts. BMS is top balancing it down to the level of the others. This was the first time I had a way of charging on my bench (kitchen counter top). Pretty happy with my DIY converted pc power supply and DPS5020 unit built with parts from Banggood.


Still acquiring 18650 cells for a second 14s100p power wall, and am trying to understand how to integrate with what I already have up and running.

This would be a separate power wall attached to a second Schneider Conext SW4048 Inverter and PCM60X charger and 9 more solar panels.


Can I simply add additional longmons and attach to same watchmon? Or do I need another watchmon to go with the additional 14 longmons?
 

Redpacket

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Charles Francis Speakman said:
Can I simply add additional longmons and attach to same watchmon? Or do I need another watchmon to go with the additional 14 longmons?

Yes you can use the one watchmon with extra longmons on the second bank. I did this on my 4 banks & it's working great!
 
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Redpacket said:
CharlesFrancisSpeakman said:
Can I simply add additional longmons and attach to same watchmon? Or do I need another watchmon to go with the additional 14 longmons?

Yes you can use the one watchmon with extra longmons on the second bank. I did this on my 4 banks & it's working great!
Do I need a shunt for every bank, or will one suffice, or do I need one at all?
 

LithiumSolar

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CharlesFrancisSpeakman said:
Redpacket said:
CharlesFrancisSpeakman said:
Can I simply add additional longmons and attach to same watchmon? Or do I need another watchmon to go with the additional 14 longmons?

Yes you can use the one watchmon with extra longmons on the second bank. I did this on my 4 banks & it's working great!
Do I need a shunt for every bank, or will one suffice, or do I need one at all?

One shunt for everything. The shunt goes right after you connect all of your banks together. Between your banks and any chargers/inverters/other loads.
 

wim

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You only need 1 shunt, connected in between the inverter/charger and the batterybank(s).
It is there to calculate the SoC% of the battery, not so much for safety...
 
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