I have a cabin that I am at occasionally use am going to solar power will be using 4 each 300ah batteries for 48 volt will be using pwm charge controller.
I want extra protection of batteries charge range 80 to 20 percent I know the controller and batteries have setups just don't want batteries to over or under charge. I have some electrical and electronics experience. would like some ideas on what I would need reading and controlling voltage. Let me know if this makes sense.
Do you know the maximum charge and discharge rates for the batteries?
Hi paulwilson9623,
I have some experience with exactly that, controlling the charge level to keep it in the more heathy region for the batteries.
Forget about voltages. This is only giving information in the extremes (>>95% or <<10%) where you don´t want to go.
You need a battery meter like
Victron Energy Smart Battery Shunt to get a good estimation of the state of charge in between.
Wehn you use a Cerbo GX and solar charger from the same manufacturer, then you get a very smart setup, where Node Red can run in the Cerbo GX and control the charging process depending of the SOC.
That´s what I am doing.
Hi Jim,
there might be very special kinds, but generally the LiFePo4 batteries can be healthily charged and discharged with one c, in this case 300A. Everything below is normally very comfortable for them.
Of course they can deliver much more, for short peak applications 2 c is no problem, when the BMS is able to deal with that.
I guess that is possible but what does that have to do with adding extra battery protection?
As far as I understand the question, it should be discussed, how extreme SOCs can be avoided, which are unhealthy for the LiFePos. Max charge or discharge rate of LiFePos are typically far away from needed currents in the application, that's not where protection for the batteries is needed.
He wants to limit the usage between 20-80% SOC, which is a typical recommendation for a long life of LiFePos. And for that you need to monitor the charge and discharge current, to understand the SOC with such a shunt. Because voltage is not giving any good hint, where you are between 20% to 80% of SOC.
What chemistry are the batteries?
Also, why PWM instead of MPPT, much more efficient.
LiFePO.
It´s in the title.
And you are right. A MPPT charger should be used, to get the max power out of the PV as long as charging is needed. That´s part of my recommendation of Victron products. They only have these.
Can be of cause other brands. I just have experience with them.
Sorry, missed the chem. I used Victron in my 7,200 wH solar setup, totally bomb proof.
You are absolutely right. I mis-understood the requirement.
Thanks, just got my bill for the month and realized I haven't been up during this period 62 kWh.