Back about 2003 or 2004, I bought an Orion Telescopes Dynamo Power Station to power my telescope drives. This is essentially a sealed lead-acid battery with an integrated charger and flashlight, similar (although with less storage capacity) than this one. This was after an unfortunate accident with trying to cheap out and use a motorcycle battery in a box. It spilled in the back of the Corvette one evening, damaging the carpet.
It worked great--but when the clouds finally cleared long enough in the last few days to again use a telescope, I discovered that it would not recharge. The LED saying "NEEDS CHARGING" would not clear. This is not a surprise; no rechargeable battery lasts forever. I was expecting to find that the replacement battery would be either:
1. Hard to remove from this unit.
2. Hard to find a replacement.
It turned out that while it was a mild hassle disassembling the unit to get out the sealed lead-acid battery, it was really not difficult to find a replacement. I called up Batteries Plus in Boise, and they had an exact replacement in stock: same dimensions, 12 VDC, 7 amp-hour, just like the original. Even better: for a couple dollars more ($34.95) they had a 9 amp-hour battery with the same dimensions. This made it possible for me to get this operational again the same day, and I was able to use my telescope this evening.