Now that we’ve found enough evidence to suggest the battery was degraded by constant over-charging, there are a few options forward: repair, replace, or upgrade.
The first option is to try to repair the existing battery cells. The information on Wikipedia indicates the cells could be repaired by performing several deep discharge+charge cycles. This must be done on an individual cell basis, because deep discharge of a pack risks irreparable damage to the weaker cells from cell reversal. It would be time-consuming even if the equipment to automate this process is on hand.
The second option is to purchase new Ni-Cad battery cells and replace the degraded ones in the Dustbuster. Ni-Cad batteries are cheap, but assembling them into packs are usually done with the help of a small spot welder. In theory the battery tabs could be attached with a soldering iron, but it’s very difficult to solder a battery cell because the metal can acts as a heat sink drawing heat away from the solder joint. If too much heat goes into the battery cell chemicals, it will damage the battery.
Whether repaired or replaced, the existing power adapter that constantly overcharges the battery pack will need to be retired. What we would need is a good charger with a controller that knows how to properly charge a NiCad battery. Without this knowledge, we’ll quickly return to the same predicament with a battery pack ruined by overcharging.
Usually, when working on a project, it’s fun to buy new tools necessary for the job. Our candidates are:
- Individual Ni-Cad cell deep discharge+charge cycler.
- Ni-Cad battery tab spot welder.
- Ni-Cad aware smart battery charger.
Unfortunately, they’re all dealing with Ni-Cad battery cells, which has faded to niche applications and their use is not expected for future projects. The present (and foreseeable future) solution to portable battery are lithium-ion chemistry cells, and that’s the motivation for the next option:
Since the battery charger would need to be replaced anyway, that removes the main motivation to stay with an electrically compatible chemistry. Freed from that constraint, the most interesting path forward is to find a way to power this old Dustbuster with an entirely different type of battery.
Let’s bring this Dustbuster into the 21-st century with a lithium battery upgrade.
(Cross-posted to NewScrewdriver.com)
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