Chris Collins

Tools · rc

LiPo manager

Keep a register of your LiPo packs — cells, capacity, C rating, chemistry, age, cycles, and internal resistance over time on a chart — with a quick log after each charge or flight, warnings for rising IR, out-of-balance cells, old and puffed packs, calculators for charge current and time, storage voltage, parallel charging and airline watt-hour limits, and QR labels that open a pack's record.

Added

Works with

How to use it

A notebook for the batteries in the shed. Each pack gets a record: what it is, when you bought it, how many times it has been charged, and the internal resistance (IR) of each cell each time you measure it. The IR trend is the best sign of a pack’s health that a hobby charger gives you, and it is easy to lose track of across a dozen packs that look the same.

How to use it

  1. + Add pack and fill it in: a name, the label or number you’ve written on it, cells, capacity, C rating, chemistry (LiPo, LiHV, Li-ion or LiFePO₄) and when you bought it.

  2. After a session, open the pack and log it: Charged (adds a cycle), Flew, Stored or IR check. Type the cell voltages and the IR per cell as the charger shows them, separated by spaces. Take IR readings the same way each time — charged, at room temperature — so they compare.

  3. The pack’s warnings and the IR chart update as you go:

    • average IR up by more than 30% since the first reading (60% shows as serious; the threshold is on the Data tab),

    • one cell’s IR well above the others (more than 3 mΩ and 50% apart),

    • cells more than 0.05 V apart (0.1 V serious), or a cell logged below the chemistry’s minimum,

    • older than three years, or more cycles than the chemistry usually lasts (LiPo about 300, LiHV 250, Li-ion 500, LiFePO₄ 2000),

    • puffed or damaged.

  4. Labels → Label maker sends a label for each selected pack (or every pack in service) to the Label maker: the name, its cells, capacity and watt-hours, purchase month and id, and a QR code. Scanning the code opens this page at that pack’s record. The register lives in the browser that made it, so scan with the phone you keep it on — or export it and import it there.

Calculators

  • Charge current and time — 1C and 2C for the pack, the voltage it charges to, the charger power it needs at the end of charge, and the time: constant current to about 80%, then the constant-voltage tail, counted at half the current. Real chargers come within about 15%.

  • Storage — from the resting voltage per cell, how many mAh to take out (or put in) to reach storage voltage (3.85 V a cell for LiPo and LiHV, 3.7 V for Li-ion, 3.3 V for LiFePO₄), and how long that takes. The state of charge comes from a typical resting-voltage curve for each chemistry, so it is approximate; LiFePO₄'s curve is so flat that voltage tells you little.

  • Parallel charging check — all packs the same cell count and chemistry, resting voltages within 0.1 V a cell of each other (it suggests letting them settle at 0.05 V), and the total current at your C rate against the charger’s current and power limits.

  • Flying with packs — watt-hours (cells × nominal voltage × Ah) against the IATA rules most airlines use: up to 100 Wh in carry-on, 100–160 Wh with the airline’s approval and at most two spares, over 160 Wh not at all. Spares never go in checked bags. Airlines can be stricter; check before you travel.

Related tools: RC power setup (what a pack does with a motor and prop), battery pack builder (building Li-ion packs from cells), and battery life and power budgets.

Browser support

Any current browser. Label printing needs the Label maker’s printer support (Chrome or Edge).

Privacy

The register is kept in your browser’s local storage and never leaves it. Export JSON writes a file on your computer; import reads one. A pack’s QR code holds only a link with the pack’s id, not its data.

Runs entirely in your browser; nothing you type leaves this page.