lithium iron phosphate (lifepo4) solar storage battery bank - lithium iron battery
Lithium-ion batteries are quite new in the solar field.
My family used 24 volt lead acid (
See the picture on the right).
These failed after a year of use.
This is a costly mistake.
My alternative bank is life425.
Like the photo on the left, the 6 volt battery.
I bought Amazon for $241.
Each battery has built-in BMS for undervoltage/over voltage protection, battery balance and temperature safety protection. LifePO4 (
And any lithium secondary battery)
2 stages are required (
Constant current, constant voltage)charging.
In my arrangement, the floating voltage is allowed as the load is always drawn by the inverter.
No explosion or fire like lithium cobalt (
Found in mobile phones and laptops, etc).
It has no toxic chemicals, and compared to lead acid, it provides four times the power density in the third part of the volume.
For these reasons, I feel it is safe to have such batteries at home.
In addition, there is a preference for local charge and partial discharge for the life4chemistry.
Compared to lead acid, you will not have the danger of charging these batteries under charge, and lead acid will become sulfuric acid if it is under charge.
If you are serious about solar power to your home, be sure to use ps4.
Led lighting and inverter air conditioning are also available.
Energy saving, your cost will be much lower.
Since the internal BMS provides short circuit protection, I used a simple single-knife single-shot toggle switch to provide isolation for maintenance.
The rated current of this switch is 20 amps and the cost is quite low.
In order to reduce the cost and reduce the material, I welded the head of the bolt on one of the terminals of the switch.
This provides a connection of mechanical strength and low resistance.
To fix the switch on the positive battery Rod, simply screw in and tighten the nut.
Again, I tightened the nuts and bolts for the negative battery.
I welded a wire directly to the head of this bolt.
The size wiring used for each battery is 12 GW obtained at the local car audio store.
Of course, you can use a larger cable, but the maximum voltage drop is 1 when my home draws the peak current. 2 percent.
To measure the ampere hour capacity of each battery pack (
My battery is connected in parallel)
I used a low-cost meter from Amazon.
In my setup, the maximum current through these meters is 10 amps, which is the worst design load.
In fact, the current per meter is less than 3 amps.
I have parallel batteries per meter, which can provide low-cost metering solutions, while only 1 m per battery.
I saved cable costs and auxiliary hardware (
Nuts, washers, bolts, lugs).
In general, if the ampere hour capacity of the battery pack is less than 60% of the original value, then it is time to replace it.
The electric energy meter for each battery pack will provide this monitoring.
My old lead-acid Bank is hard wired, large spec wired, with circuit breakers every 24 v string.
For my new setup, I would like a simpler way to add/remove the battery from the solar system.
I used two standards.
There are 6 outlets in each 15r outlet.
Please note that this is not a standard use for these outlets, but I have registered a logo warning about the use of these outlets.
The advantage of this arrangement is that I can safely insert and remove any battery pack without affecting the rest of the power system.
The connector on the battery side is the fit of two prong polarization-15 plug.
I chose the bigger blade as my front.
It is impossible to insert the wrong polarity into the socket.
Safe, high current, easy to get, low cost.
The main cable from the socket to the DC load/solar maximum power point tracking controller is 2gw with old inverter.
Please note that the DC rated current of the cable and electrical connector (
Not switch or relay)
AC rated current higher than the same cable.
This is due to no skin effect on DC.
I had a hot scan of the battery at night max load.
No problem with any connection was observed.
I also mechanically verify the connection by trying to rock/rotate each one.
All lithium technologies prefer two phases (
Constant current, constant voltage)charging.
My solar charging controller is a maximum power tracking unit for inland flexmax 80amp.
This provides three stages (
Final stage of floating)for lead acids.
Here are my settings. CC: 0.
5c or 5 amps per battery: 80 amps in total. CV: 29. 0vAbsorption (CV)
Timer: 120 minutes.
5 v since my inverter is always connected to the life4bank, the floating voltage will not have a negative impact on my battery.
If you only use a lithium ion battery in standby, then floating charging can be a problem: you have to use 2-stage (
CV is behind CC)charging.
Currently, there is no major manufacturer of solar charging controllers to provide configuration files for ps4.
I have emailed outback power systems and they are not willing to take this action yet.
Once you have a programmable charging controller, using the settings I provided will allow you to use a lithium ion battery, but note that there must always be a load on the battery.
For example, using LiFePO on desktop ups, which I do not recommend at the moment, because floating charging in the backup service may reduce the performance of the s4.