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LiPo storage voltage and safe storage
A LiPo that sits fully charged or flat ages faster and is riskier. Here is the storage voltage to aim for and how to keep packs safely.
The storage voltage
BYU's combat robotics guide says to charge cells to 3.8 to 3.85 V per cell for storage longer than three days. Most hobby chargers have a Storage mode that does this for you: select LiPo, the right cell count and Storage. Typical totals, as a guide, are:
| Pack | Approx. storage voltage |
|---|---|
| 1S | 3.8 V |
| 2S | 7.6 V |
| 3S | 11.4 V |
| 4S | 15.2 V |
| 6S | 22.8 V |
These are simple multiples of 3.8 V. Makers' recommendations vary, so check your own battery label.
Why not fully charged or fully flat?
A full cell sits at 4.2 V and is under stress. A flat cell, below about 3.0 V, can be permanently damaged and should never be charged or used. BYU says not to use or charge a LiPo charged above 4.2 V per cell or below 3.0 V per cell. A mid-level charge is the compromise that keeps cells healthy.
Where to store
- Cool and dry. West Yorkshire Fire and Rescue advises avoiding very hot or very cold conditions.
- Away from anything flammable, not in a hallway or escape route, and not near a boiler or in a hot loft or car.
- In a LiPo-safe bag or a suitable container. BYU warns not to store LiPos in a bag with other loose components, since a loose wire could short the plug. West Yorkshire Fire and Rescue says to store spare batteries in plastic containers away from metal items such as keys and coins.
- Out of reach of children and pets.
- Not on charge. Do not store a pack plugged into a charger.
Before a long break
- Check each pack for swelling or damage and retire any that fail: see swelling and damage.
- Take each pack to storage voltage with your balance charger.
- Label the date and condition if you have a lot of packs.
- Check them every few weeks. A pack that has self-discharged a lot or puffed up should not be reused.
Before you use a stored pack
Inspect it, then charge it with the balance charging routine. Do not use a pack that has sat for a long time at a very low voltage.
How long do packs last?
There is no fixed life. Packs age with use, heat, deep discharge and time. A pack that sags badly under load, loses flight time quickly, gets hotter than its siblings or puffs even slightly is telling you it is finished. Rotate packs so no single one is worked harder than the others, and label them so you can spot a weak one. Retire it rather than push it, and see disposal and recycling for what to do next.
Transport
When travelling by car, keep packs out of direct sun and hot boots. For air travel, rules are different: see flying with lithium batteries.
This is general information, not a substitute for the instructions that came with your battery and charger. If your manufacturer's advice differs, follow the manufacturer.
Frequently asked questions
What voltage should I store a LiPo at?
A typical guide is 3.8 to 3.85 V per cell for storage beyond three days.
Is it bad to leave a LiPo fully charged?
It is not recommended for longer storage. A mid charge is kinder to the cells.
Should I keep LiPos in the fridge?
We have not seen official UK guidance recommending it. Cool, dry room temperature storage away from flammable items is the usual advice.
What if the voltage has fallen very low?
Do not charge a LiPo that has dropped below about 3.0 V per cell. Retire it and dispose of it safely.