Salvage your UPS batteries
In many countries that endure interrupted supply of electricity from the national grid, such as where I live in South Africa, residents rely on backup power solutions during load shedding. One of the more affordable and quieter options (as opposed to a petrol/diesel generator) are Uninteruppted Power Supplys (UPS), the most affordable of which use lead-acid batteries.
I’ve been through several and so far the more expensive power inverter with lithium-ion batteries has served me better, especially since I work remotely from home. However, I still had a few UPS’s lying around with degraded lead-acid batteries (usually caused by battery sulfation) that I wanted to salvage to power less demanding work loads such as my raspberry pi projects, wifi-extenders or LED lights. Instead of discarding the old batteries (which is inevitable), I thought I’d squeeze a little more mileage out of them.
Note: Even with dead batteries the capacitors on the circuits could still have a charge that could lead to a nasty electric shock. Ensure that the UPS is not plugged into mains and that it is in an off state. You will also void your warranty if it is still valid by proceeding further. Do this at your own risk!
Here’s what you’ll need:
- Latex gloves and safety glasses
- Stanley knife
- Screwdriver set long enough for the depth of the UPS casing
- Distilled water
- A syringe
- Silicon glue
Open up the UPS casing to expose the batteries, you may have to remove any brackets holding them in place. If there are multiple batteries take note how they are connected together and to the UPS circuitry. Most UPS batteries will be connected in series.
Carefully remove the terminal connectors and remove the batteries. Place the batteries upright on a level service. I was able to do this by only disconnecting the terminals from the UPS itself.
Most of the batteries have a thin plastic cover that you will need to remove to expose the filler holes, I used a Stanley knife to cut through the seam and a small flat screwdriver to lift away the cover.
You can “pop” off the rubber caps (wearing your safety glasses) to expose the holes.
Get your distilled water and syringe ready for filling.
Fill the syringe up with distilled water and try not get any air bubbles into the syringe and fill the holes until the water reaches the top of the filler nozzles, I used a round robin filling approach in a clock-wise direction but it doesn’t really matter.
Repeat the steps above on the other batteries. Tap gently on the batteries to let any air out and allow the distilled water to settle, you may need to top up and monitor until you’re satisfied that the batteries are completely full.
Carefully dry any water that may have spilled on the batteries, especially around the nozzles and then replace the rubber caps.
You may need to glue the plastic cover back on to the batteries where you used the Stanley knife to break the seam.
Carefully re-install the batteries in the UPS, double check for any water leakage and close up the UPS.
Plug the UPS into the mains and let it charge. Monitor for any signs of malfunction and disconnect immediately if there are.
If everything is operating normally and the UPS has had enough time to charge the batteries (status indicators may not be accurate yet) then power off the UPS and connect a load below the maximum threshold of the UPS. Allow for a few cycles of discharging and charging and you should notice a significant improvement in uptime when there is no mains power source, (was about 10 for me before I noticed approx. 90% efficiency).
If this project was successful, you saved some cash and earned a Ron Swanson nod of approval.
