I just over discharged a battery to 2.9v in a mech, what should I do?

[Niamh]

Was just using my mechanical mod and did not notice vapour production drop off, quite suddenly there was no vapour, so I took the battery out and checked it with a multi meter, the battery had discharged to 2.9v, I don't understand how this happened as usually I would be recharging batteries at around 3.6v, I would notice that there was much less vapour. I'm searching on the internet and it seems that over discharging batteries is dangerous. Should I monitor this battery to ensure there are not problems with it and for how long? I am a bit scared to go to bed! Presumably the battery needs to be discarded? Battery University just say that if Li ion are discharged below 2.5v they will "fall asleep", which does not sound too worrying, but on other sites there is talk of batteries potentially becoming volatile.

 

[retired1]

Doing it once or twice isn't going to be the end of the world as long as you don't discharge them further than that. Just don't make a habit of it and pay closer attention.

 

[NicoHolic]

You should take retired1's advice and continue to use it. It's no less safe.

 

[WarHawk-AVG]

The dangers of over discharging is LEAVING it overdischarged...leaving it low allows copper shunts to form on the charging strata, next time you try to recharge..shorts across the media make heat, heat makes more shorts, more short make more heat 'splody 'splody

Charging Lithium-Ion Batteries

Over-discharging Lithium-ion

Li-ion should never be discharged too low, and there are several safeguards to prevent this from happening. The equipment cuts off when the battery discharges to about 3.0V/cell, stopping the current flow. If the discharge continues to about 2.70V/cell or lower, the battery’s protection circuit puts the battery into a sleep mode. This renders the pack unserviceable and a recharge with most chargers is not possible. To prevent a battery from falling asleep, apply a partial charge before a long storage period.

Battery manufacturers ship batteries with a 40 percent charge. The low charge state reduces aging-related stress while allowing some self-discharge during storage. To minimize the current flow for the protection circuit before the battery is sold, advanced Li-ion packs feature a sleep mode that disables the protection circuit until activated by a brief charge or discharge. Once engaged, the battery remains operational and the on state can no longer be switched back to the standby mode.

Do not recharge lithium-ion if a cell has stayed at or below 1.5V for more than a week. Copper shunts may have formed inside the cells that can lead to a partial or total electrical short. If recharged, the cells might become unstable, causing excessive heat or showing other anomalies. Li-ion packs that have been under stress are more sensitive to mechanical abuse, such as vibration, dropping and exposure to heat.

 

[Niamh]

Hey thanks, think I'll be monitoring batteries a bit more closely in future

 

[Scarey]

If it charges, it should be good. Just be careful. If you had killed it, it wouldn't take a charge anymore.

 

[epcii]

I accidentally brought mine down to 2.8v once and it didn't concern me much since the eFest specs say 2.5v minimum. It still works fine.

 

[dam718]

2.9V is well within the safe specs for discharge... You should be fine!