Comments on this setup?View attachment 5001Could this work?
Comments on this setup?View attachment 5001Could this work?
Hi you have asked an interesting question. It sounds like you are considering bypassing the SCC and going straight to the BMS thru the charge port on the BMS. I think the BMS could regulate small differences in the incoming charge, but as for my system the voltages would be too far out of range of the BMS, and as a result the BMS would rarely allow any charge to the battery. I will be interested to learn, what you find out. Good luck, and I hope you see no magic smoke.I am learning here myself but it seems like the C- could be used to disconnect ground from the solar array in order to block the solar from further charging. The charge controller would still be connected to the battery. The voltage and current from the solar array is variable so you would need to make sure the BMS could handle any extremes. I haven't tried this and may be missing something.
I called Midnite Solar and asked if the Midnite Classic 150 would be damaged if the battery were to be disconnected while the PV array was supplying power. They said it would not be an issue for the Classic because the controller simply shuts off when disconnected from the battery. So, it depends on what solar charge controller you are using I guess.Most people that i talked to said that when you cut off the batteries from the Charge Controller while the solar panels are connected will surely damage the controller.
Sorry about that ..I'm confused, you ask about using 2x common port bms but you show a picture of a separate port bms and a relay.
You are tweaking my OCD.
Seems like it should work to me. As mentioned by another there may be a momentary drop in voltage during the switch but I would think the MPPT could handle that. I haven't tested that though.Hi all!
I have a 8 cell 24v system under construction. Using the Victron MPPT (100/30) and Smart BatterySense for low-temp cutoff.
I have the Daly 100A common port ordered, but I worry about what happens if the BMS will do a cutoff (low voltage for example) if I have both load and charge through the BMS.
But, what if one would put a 24v relay on the negative from the charger, so when the relay has power the charging will go through the BMS, but if the BMS does a cut-off the relay would switch the negative from the charger directly to the battery (and bypass the BMS)?
Then the battery would be charged although the BMS did a low voltage cutoff, right? And when the BMS goes back online then the relay would would be powered and switch the negative back through the BMS.
What do you all think?
View attachment 665
Also, I posted this elsewhere sometime ago:
Quick update for advanced LiFePO4 raw cell systems using a Daly BMS:
On my website I recommended using a separate port BMS for over voltage protection for the mppt connection (if common port BMS is used, possibility of destroying mppt during low voltage disconnect).
Well yesterday, a viewer and I finally received our separate port BMS from Daly, and the amp rating was not as advertised on the listing. The separate port can only handle 10 amps!
Considering the likelihood of over voltage situation from most high quality mppt, and the chance of matched LiFePO4 cells going out of balance is rare (and BMS will correct for cell drift over time), and that LiFePO4 can be over charged to 4.2v per cell before electrolyte degradation... I would say its safe to connect mppt directly to the battery bank, and bypass the BMS entirely. We have been doing it this way for years, but people still want to use a BMS.
I would say use BMS for loads, and not for chargers. If you have mismatched cells, and some hit a higher voltage at high SOC quicker than others, drop the upper limit voltage of your controller. 14.0-14.2v is a safe charging voltage that can give full capacity with LiFePO4 12v.
I hope this helps! I bet most people building these systems will figure this out when they see this problem, but if you are a beginner trying to build an advanced level system, then this bit of information will be very useful. Let me know if you have any questions
As a newbie to this BMS learning curve for DIY LifePO4s, I am wondering: What does" SCC" stands for? I study this full thread as see it I can figure that out.The big problem with separate port BMS is the current is extremely limited. Not uncommon for a 100a separate port bms to have a charge line that can only handle 8-15 amps. If you are building a system for solar, use a common port for your loads, and connect the SCC directly to the battery.
Solar Charge ControllerAs a newbie to this BMS learning curve for DIY LifePO4s, I am wondering: What does" SCC" stand for?
As a newbie to this BMS learning curve for DIY LifePO4s, I am wondering: What does" SCC" stands for? I study this full thread as see it I can figure that out.
There are a couple we (unfortunately) need to add:Svetz has put together a list of commonly used Acronyms here
Mikey likes it!There are a couple we (unfortunately) need to add:
*View attachment 10679
- LiFePo4 - Lithium Iron Polonium(IV).
- LifePO4 - View attachment 10678 Phosphate.*
Too picky?