Refilling the UPS

When we got our UPS system a couple of years ago (dedicated to the computer and Internet), we bought it from a car battery shop. It turns out that UPS batteries are the same as car batteries, so the same suppliers usually deal in both. Ours was a single battery as well as an inverter that allowed us to plug in AC devices. It's a bit of a waste because that AC is immediately converted back to DC to use in our computers, but at least it works for now and we don't have to worry about power shutdowns.

The cells of our UPS battery have to be replenished periodically. Each cell has its own floating rod to indicate the level, and now, after two and a half years, we noticed that the levels had become quite low. Ideally one is supposed to top the cells up with distilled water, but RO water also works at a pinch. (When the battery of our BSNL WLL phone was on its last legs we got it topped up with acid a couple of times to give it a boost, but we weren't sure how exactly that worked for our current battery).

We didn't know of any place to get distilled water nearby, and neither do we have an RO water filter, so we were getting ready to buy distilled water from battery shop in Salem (or, failing that, fill a bottle from Patti's RO filter). Then, last week, I went to the post office to send a parcel, and we decide to ask the postmaster where he gets distilled water for his UPS batteries. After the postal service got "digitised" several years ago, there was a spell of intermittent power supply, which prevented the post office from getting any work done. Eventually, the postmaster got fed up and set up a UPS system in the office, complete with a battery of batteries (three in total). The power is back now, but the batteries are still in operation, and the postmaster must be topping them up from somewhere.

I went to the post office and handed in my parcel for registration. The postmaster asked why I don't use Speed Post instead; I asked if the price wouldn't be higher, and he was looking in the computer to check both rates. In the meantime he took a letter from two boys who had come on behalf of the petrol bunk, realised they didn't have change, and sent them back to get it. Speed Post turned out to be ₹5 more than a registered parcel, so I sent it by the latter option (the slabs are different, so Speed Post sometimes turns out to be cheaper, but only the destination is relatively nearby). The petrol bunk people came in the middle and gave their change; then, as I was paying for the parcel I asked the postmaster where to get water for the UPS batteries. It turned out that such water is available at the petrol bunk!

I was going to the petrol bunk anyway to refill the bike, so while topping it up, I asked if they have "water for UPS batteries". They asked if I want just water or also acid! It turns out selling distilled water as well as battery acid at petrol bunks is a regular thing—another reminder that a USP is just a special variety of car.

The acid cost ₹45 per litre, but I wasn't sure about it so I bought the ₹25 bottle of distilled water for now. We unscrewed the indicators of our battery cells and poured it in—we ended up using almost exactly the entire litre—so our batteries are now back to being full.

Our next job is to ask the postmaster how ofter he fills his batteries with water, and how often he fills them with acid.