Battery Health
LFP is different. In a good way.
VoltPak uses lithium iron phosphate (LFP) cells - a chemistry built for longevity, not energy density. Here's what that means in practice, and how to get the most out of it.
To 80% capacity. That's roughly 10 years of daily use before meaningful degradation. Most lithium-ion products rate 500–1,000 cycles.
Unlike NMC, LFP doesn't benefit from partial cycling. Charge to 100% and discharge fully - the chemistry handles it.
Store between –10 °C and 30 °C long-term. If storing more than 3 months, charge to 50% first.
Best practices
Do I need to avoid charging to 100%?
No. LFP chemistry is designed to tolerate full charges without the calendar degradation NMC sees at 100%. Charge to full whenever you want.
How often should I cycle the battery?
At least once every 3 months if it's sitting in storage. Letting LFP sit fully depleted for extended periods can cause cell imbalance that's hard to reverse.
What does the BMS actually do?
It monitors all 8 cell groups individually - voltage, temperature, and state of charge. It balances cells passively during charge, disconnects the pack if any cell exceeds safe limits, and reports everything to the display over UART. You can see cell-level data in the system info screen.
The capacity reading seems lower than rated. Is something wrong?
Not necessarily. Displayed capacity is a firmware estimate based on coulomb counting, recalibrated on each full charge-discharge cycle. A new pack may read slightly under rated capacity for the first 5–10 cycles before the estimate stabilises.
Can I read raw cell data myself?
Yes. The BMS exposes a UART interface at 115,200 baud (3.3 V logic) - connector and pinout in the technical manual. It outputs a JSON-formatted status packet every 2 seconds with per-cell voltage, temperature, and SOC. The protocol is documented in the hardware ZIP.
When is a cell actually at end of life?
Warranty replacement threshold is 70% capacity retention. In practice, LFP cells tend to hit this point and then plateau - capacity doesn't continue falling sharply. Most packs remain usable well past the warranty threshold, just with reduced runtime.
Voltage reference
| State | Per-cell voltage | Pack voltage (8S) | Notes |
|---|---|---|---|
| 100% - fully charged | 3.65 V | 29.2 V | BMS top-balance target |
| 80% - typical resting | 3.30 V | 26.4 V | Normal daily resting voltage |
| 50% - storage voltage | 3.20 V | 25.6 V | Ideal for long-term storage |
| 20% - low warning | 3.10 V | 24.8 V | BMS activates low-SOC warning |
| 0% - cutoff | 2.80 V | 22.4 V | BMS disconnects pack at this point |
| < 2.50 V - over-discharged | < 2.50 V | < 20.0 V | Contact support - cell may be damaged |
Cell voltage readable via BMS UART or the system info screen on the touchscreen display.