Hi All,

Some of you may know me from an older post where I talked about my energy efficient small offgrid house where I live now.
I made the decision to use Lithium iron phosphate (LiFePO4) battery for energy storage since it is the most cost effective solution for energy storage.
There was a problem that needed to be solved and that was to build a solar charge controller able to charge and monitor this type of battery (and any other Lithium since is fully programmable) since still a large majority use the old and expensive Lead Acid.
The solar BMS (Battery Management System) charger is now in beta stage and decided to make this Open Source and available on Kickstarter for those that need something like this.
Here is a 3D render of how the final solar BMS will look like there are some minor changes from the beta most significant the 6 capacitive buttons instead of the capacitive scroll wheel and 3 buttons.
And here is a link to the Kickstarter project page for more info.


 

Interesting, I agree that better battery management is needed. Can you run through the economics of why these specific batteries are more cost effective than a well managed (ie, always at a fairly high state of charge) bank of lead-acid batteries? Some data I see:

Cost about $150 each.
3.2 Volts, 100Ah
2000 cycles at 80% DOD

I looked into it more and while there are pros and cons, the newer lithium batteries make sense. And I don't see any other good products that combine charging and monitoring lithium batteries from a solar panel input. The project is close to being funded, I hope it makes it.

you can save a high power energy with solar cell for you can use in villages for light way.

Lithium Iron Phosphate cells have almost a decade of powering a variety of electric vehicles.  In many cases the battery management has consisted entirely of pack voltage limits and a "commissioning process" that balanced the cell voltages (at either the fully charged or fully discharged state) once with series connected cells making up the pack   THERE IS NO NEED FOR MORE! The cells stay balanced so long as the only load is upon the whole "string"  Any charge controller that offers a constant upper limit on charging voltage, at the desired voltage, can be used to control charging. A low voltage load cut is also desirable to protect the cells and is found in many charge controllers.   If the proposed product has more than TWO wires to the battery pack it will have a negative impact on battery performance and life. Further, if it's like the typical JUNK sold as a "BMS" it will be a fire hazard and seriously shorten cell life.

Any good balancing/protection circuit (with a wire to each cell) increases performance, life and safety. Unlike lead acid batteries, you can't overcharge some cells to force the cells into balance. And of course every cell in a string isn't exactly equal to the others. So the state of charge of the whole pack doesn't mean much about an individual cell.

Jorr
The trouble is there is no "GOOD" "balancing/protection circuit". They ALL add parasitic loads that cause the cells to deviate from each other! You are correct that "you cant overcharge some cells to force into balance" BUT once "balanced" they stay balanced if only series connected (without different parasitic loads on some cells). The "commissioning process" includes an initial "balancing of cell voltage/state of charge. There after limiting pack voltage excursions has been proven the safest most reliable way to assure safe long life of LIFEPO4 cells in a series connected pack! Virtually ALL hardware sold as a "BMS" is in fact a BATTERY MURDERING SYSTEM because the discharge currents it adds differ from cell to cell and WILL discharge individual cells to eventual destruction especially if left unattended.

If you left a balancing (or any other) circuit on for a long time and it wasn't also a charger (but most are), then I'd agree that it would drain and eventually damage the pack. Other than that, we will just have to disagree.