A call from a "friend" looking to rope me into replacing the batteries in his powerchair (again -- No Good Deed Goes Unpunished). I begged off as my schedule is overly full for the next few months (fourth quarter is usually spent upgrading and replacing kit).
This proving to be a good choice as he's making noises about switching to LiFePO4 batteries instead of the SLAs he's always used (the SLAs being cheaper but have relatively short lifespans... a few years). That looks like it will quickly become a timesink.
But, it got me thinking about whether I should make that change for *my* chairs.
The SLAs are typically 12V @ 75AHr -- about 50 pounds each. Comparable (physical) *size* lithiums are about double that capacity and don't "degrade while parked" (if you kill the parasitic loads as I do, given that my chairs are seldom used).
I see two major problems:
- the charger will have to be replaced (and consideration for anything that might be impacted along the wiring harness with such a change as you can't easily access the batteries)
- the "fuel gauge" will be useless (as it relies on the discharge characteristics of the SLA pack) This last being the most serious as you can't easily recover from a battery that's "suddenly" gone flat (like driving in a car with a broken fuel gauge)
I can address both of these issues -- but, it rises to the level of a real "project"; not some quick fix.
Anything else that could complicate such a decision? (I haven't researched travel or shipping issues which could be complicated, given the association of "lithium" with "spectacular fires")
[Replacing the chair is not practical as it's not something that I "need" or for which I could justify the outrageous cost...]
[[I know a guy who has done this but he REALLY made a project out of it... replacing all of the drive electronics, motors, brakes, etc.]]