Lithium batteries

wa8yxm wrote:

pianotuna wrote:

time2roll wrote:

pianotuna wrote:
The "cold" end is the dangerous part. Charge below that, and the batteries become expensive door stops.

Or the BMS stops the charging at low temperature and protects the battery until it can be determined why the heating system has failed.

You left out part of what I said which was there is no need to have heaters cut in at 50 f.

Warning.. there is a video where an engineer (We like to take things apart as well as build 'em) took apart a LiFePO4 battery.. Down to the cells (He did not take them apart)

The battery clearly claimed to have both low and high temp sensors and protection (High temp is to prevent thermal runaway and fires.. Rare with LiFePO4, common in some other LiOn types)

IT did have a high temp sensor.. But no low temp at all. He tested.
So just because it says it's low temp protected... Does not mean it is.

that was a store bought boxed one and what that engineer may have missed is that one temp probe can be used for both high and low limits.. when you build them yourself you know exactly what they have in them. high temp is mainly to prevent charging when the battery is to warm, not for thermal runnaway, as LifePO4 is highly resistant to that. in fact if you have ever seen the vido of what it takes to get a LiFePO4 to actualy catch fire, its pretty amazing..