[RE-wrenches] Lithium Ion tool batteries

[larrycrutcher]

Wow, spot on Alex. It's breath of fresh air to hear correct info about Li batteries. Far too much misinformation has flooded the web.

Just adding a note about temperature. LFP type batteries can be discharged with cell temperatures down to -5°F and will not be harmed if exposed in storage to as low as -40°F for short duration. We recommend all long term storage be at about 50% SoC.


Larry Crutcher
Starlight Solar Power Systems




On Jan 19, 2022, at 9:58 AM, Alex MeVay <alex at sunforgellc.com> wrote:

Generally, storage or use at cold temperatures shouldn't be an issue,
as long as the battery can still deliver enough power to operate the
tool effectively.

Charging though...at cold temperatures, ion mobility goes down.  If
the battery is charged too fast, the lithium ions can't make it into
the graphite anode fast enough and they start to plate out as metallic
lithium.  At best, this results in a permanent reduction in capacity.
Next worst from there, the lithium metal can create an internal soft
short, immediately or at a later point in time, resulting in high
self-discharge or a dead cell.  Worst case, it turns into a hard short
and a fire.

In theory, the BMS or charger should prevent charging too fast or too
cold, but who knows if an edge-case like this is actually implemented
correctly on any particular battery system.    Be careful charging!

Alex MeVay

Genasun * Blue Sky Energy * http://sunforgellc.com
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