For a fully charged Nickel-Iron (NiFe) battery, the Specific Gravity (SG) of the electrolyte (potassium hydroxide and lithium hydroxide mixture) is typically between 1.21 and 1.23.
Any NiFe Battery that is Not holding Charge at 1.2V~1.6V, You need to TEST the Cells;
- First do a Continuity Test to see if any of the Terminal Plates are Shorting !
- Test the Electrolyte Specific Gravity (SG), the reading should be between 1.21 & 1.23, if SG is Less than 1.18, it is an indication that the Electrolyte may need Changing if the Battery has been recently Charged.
- CLEANING: Remove all the Electrolyte by siphoning or Tipping out the electrolyte into a Non Corrosive Bucket/Container, Keep OUT of the Way of CHILDREN, ANIMALS and let settle with a Cover over it for Safety.
We have been told you can Fine Filter the Electrolyte down to 2 micron & re-use, we have not tested Filtering.
- Now, get a Garden Hose and Re-Fill the Cell with clean Tap Water to just above the Cell Plates.
- Put the fill Plugs/Bungs back on, so theirs little or no splashing, then Rock the Cells back & fort vigorously, that should dislodge any loose Debris on or around the Plates, it might be a good idea to place Rags under the Battery to stop any Damage from Rocking.
- Tip the Flushed Contents into the Ground/Grass, or into a Large Plastic Garbage bin or Non corrosive Container, if you want to see what/if any Debris comes out.
- Repeat steps 4 & 5, until No Debris & Clear water comes out.
- If/When there is No silt or residue on the inside of the Battery, do a Continuity Test to see if any of the Terminal Plates are Shorting !
- NB:You Don't need to do this to all the Batteries at the Same time, you can start with the Batteries that are Problematic, obviously you should Mark each Batteries you service them !
- RESTORING: If done correctly, a New batch of Electrolyte, the Batteries should work again for another 7~15years, and remember to Only add Distilled Water to Maintain Electrolyte between the Min. & Max. Marks.
The Electrolyte
There is a lot of mythology surrounds the electrolyte, and it's mixture is fairly critical, as higher and lower concentrations of KOH can have interesting effects.
For example 1.25 g/ml of KOH to distilled water gives the longest life, while 1.34 g/ml gives the highest output (and greatly helps the cells resist freezing in cold climates). This could be very useful for those OFF-Grid" in Cold climates.
Another popular item floating around the internet is the addition of lithium hydroxide to the electrolyte. The popular misconception is that this adds to the cells capacity. In actuality, lithium hydroxide decreases the cell's capacity somewhat, however it has a protective effect on the cell during conditions of high temperature cycling. If you choose to use KOH and lithium hydroxide, the mixture We've been told are most pleased with has been: Potassium hydroxide 1.3 g/ml, lithium hydroxide 15 g/l.
If You are finding Your Electrolyte in Not Lasting for 5+ Years, you may be Consuming more than 80% of the kWh Energy Storage, as this can shorten the life of the Electrolyte Quicker !
Solution is simple, Purchase more Energy Storage and connect all to Bus-Bars, as that segregate each Battery Bank.
As Much as we like NiFe Battery Technology, Nothing comes close to Lithium Iron Phosphate Energy Storage for Cost & Reliability, where Super Capacitor (SC) Energy Storage are just as good, but cost approx. 300% more per kWh ! |
