I loaned a family member a dewalt 20v sawzall, they returned it with a completely discharged battery!!! There is hope, the battery should have internal cutoff at determined low voltage
NO NO No it’s not OK to have a Li-Ion deeply discharged at all.
Here is why:
When discharged below its safe low voltage (exact number different between manufacturers) some of the copper in the anode copper current collector (a part of the battery) can dissolve into the electrolyte. The copper ions then in turn can stick on to the anode during charging by chemical reduction and cause dendrites. The dendrites might cause a short circuit inside the battery. So basically discharging too much is as bad as charging too much. But the dendrites caused by overcharging is formed out of lithium.
Normally the battery pack should have some sort of supervisory circuit that disconnects the cells from the charger or load when the cells are above or below the recommended voltages.
Deeply discharged Li-Ion won’t last a year, especially in storage where large ambient temperature changes are possible. It is recommended to store Li-Ion half-charged, to prevent “overcharged state”
Here is the Technical information
Review of ONE manufactures instructions for rechargeable batteries:
Manufacture Charging recommendations
Important Charging Notes
1. Longest life and best performance can be obtained if the battery pack is charged when the air temperature is between 65 °F and 75 °F
DO NOT charge the battery pack in an air temperature below +40 °F , or above +105 °F.
This is important and will prevent serious damage to the battery pack.
2. The charger and battery pack may become warm to the touch while charging. This is a normal condition, and does not indicate a problem. To facilitate the cooling of the battery pack after use, avoid placing the charger or battery pack in a warm environment such as in a metal shed or an un- insulated trailer.
3. A cold battery pack will charge at about half the rate of a warm battery pack. The battery pack will charge at that slower rate throughout the entire charging cycle and will not return to maximum charge rate even if the battery pack warms.
4. If the battery pack does not charge properly:
a. Check operation of receptacle by plugging in a lamp or other appliance;
b. Check to see if receptacle is connected to a light switch which turns power off when you turn out the lights;
c. Move the charger and battery pack to a location where the surrounding air temperature is approximately 65 °F – 75 °F (18° – 24 °C);
d. If charging problems persist, take the tool, battery pack and charger to your local service center.
5. The battery pack should be recharged when it fails to produce sufficient power on jobs which were easily done previously. DO NOT CONTINUE to use under these conditions. Follow the charging procedure. You may also charge a partially used pack whenever you desire with no adverse effect on the battery pack.
6. Foreign materials of a conductive nature such as, but not limited to, grinding dust, metal chips, steel wool, aluminum foil, or any buildup of metallic particles should be kept away from charger cavities. Always unplug the charger from the power supply when there is no battery pack in the cavity. Unplug the charger before attempting to clean.
7. Do not freeze or immerse the charger in water or any other liquid. WARNING: Shock hazard. Don’t allow any liquid to get inside the charger. Electric shock may result.
WARNING: Burn hazard. Do not submerge the battery pack in any liquid or allow any liquid to enter the battery pack. Never attempt to open the battery pack for any reason. If the plastic housing of the battery pack breaks or cracks, return to a service center for recycling.
1. The best storage place is one that is cool and dry, away from direct sunlight and excess heat or cold.
2. For long storage, it is recommended to store a fully charged battery pack in a cool dry place out of the charger for optimal results.
NOTE: Battery packs should not be stored completely depleted of charge. The battery pack will need to be recharged before use