Maintain lead acid batteries regularly

Thursdays are usually maintenance day for the electrical power supply company in my area. So there was nearly a full day power cut. Luckily, I have a UPS so that sorts out the problem for 8-9 hours. The lead acid battery I use for my UPS is about 3-4 years old, and these being unsealed batteries they last long, really long if maintained properly.

In the past I have had one such battery last for a decade before requiring a replacement.

Unsealed lead acid batteries require two important maintenance activities:

  1. Topping up distilled water every 6 months
  2. Applying petroleum jelly / grease on the terminals to prevent corrosion

The distilled water topping up is done regularly because I buy the bottles in bulk, but I didn’t have the battery terminal grease to apply and had been procrastinating over buying it for quite some time.

Then disaster happened – the UPS started beeping low battery. I checked the voltage at the battery terminals when the UPS was under load, it was showing 12.4V. Then I checked the voltage at the end of wire after the lugs it was dropping to 9.8-10V in between. The cables and terminals had lot of deposit accumulated over the years, which I had cleaned recently after the UPS beeped last time which seemed to fix the issue temporarily. But yesterday it showed no signs of stopping. Additionally I observed the positive wire was quite warm which usually doesn’t happen otherwise. Time to do a permanent fix.

Here you can see the condition of the lug, the nut and the bolt which I removed from the battery, corrosion completed ate the metal in that!

So I purchased new lugs, nuts and bolts, crimped them and installed after scraping off the corroded material collected on the terminals using sand paper. Beeping stopped. Then I applied Lithium NLGI 3 grease on it to prevent further corrosion. Making an event in my calendar to check this every 3-6 months. 😅

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