Ready-made JK-BMS presets for LiFePO4, NMC and LTO

Nine tested starting points for JK-BMS: three levels for each of LiFePO4, NMC and LTO. Each one is built from cell datasheets, the JK manuals and long-term ageing research, and can be written to your BMS over Bluetooth or applied to a .jkcfg file in the editor.

Connect your BMS Read over Bluetooth in Chrome or Edge, or open a .jkcfg file. Nothing is uploaded.

Hard, medium or gentle?

Lithium cells age faster when they sit near full charge, go deep into empty, get hot, get charged in the cold or run high currents. The three levels trade capacity for life by moving each of these limits.

Hard

Full window rated by the cell maker

Usable capacity
Cell life

Uses the voltage, temperature and current limits from the cell datasheet, with a small safety margin. You get all the capacity the cells are rated for, at the cost of faster ageing.

Best for: Backup systems that are rarely cycled, or packs where every amp-hour counts.

Medium

Softer everyday window

Usable capacity
Cell life

Trims the top and bottom of the charge window and lowers the currents and temperature limits. You lose a few percent of capacity and gain noticeably longer life.

Best for: Solar and home storage that cycles every day. A good default for most people.

Gentle

Maximum cycle life

Usable capacity
Cell life

Keeps the cells in the middle of their charge range, limits the currents to a fraction of the rating and stops charging well away from heat and cold.

Best for: Oversized packs, buffer and UPS use, or anyone who would rather keep the cells for as long as possible.

LiFePO4 (LFP) presets

LFP has a very flat voltage curve between about 3.2 and 3.35 V, so the top of charge matters most: it is where balancing and the SOC reset happen. Datasheets such as EVE LF280K allow 2.5 to 3.65 V, 1C and charging from 0 °C, but at 0 to 10 °C only a small fraction of the current is allowed.

Parameter (per cell)	Hard	Medium	Gentle
Cell OVP / recovery	3.65 / 3.45 V	3.60 / 3.40 V	3.55 / 3.35 V
Charge voltage RCV / float RFV	3.55 / 3.40 V	3.50 / 3.37 V	3.45 / 3.35 V
SOC-100% voltage	3.50 V	3.45 V	3.41 V
Cell UVP / recovery	2.50 / 2.70 V	2.80 / 3.00 V	2.95 / 3.10 V
Power-off voltage	2.45 V	2.70 V	2.85 V
SOC-0% voltage	2.60 V	2.90 V	3.05 V
Balance start / trigger	3.40 / 0.01 V	3.40 / 0.01 V	3.40 / 0.005 V
Charge over-temperature / recovery	55 / 50 °C	50 / 45 °C	45 / 40 °C
Discharge over-temperature / recovery	60 / 55 °C	55 / 50 °C	50 / 45 °C
Charge low-temperature / recovery	2 / 5 °C	5 / 8 °C	10 / 13 °C
Discharge low-temperature / recovery	-20 / -15 °C	-15 / -10 °C	-10 / -5 °C
Max charge / discharge current	1.0C / 1.0C	0.5C / 0.7C	0.3C / 0.5C

Voltages are per cell; multiply by the number of cells in series for the pack. Currents are C-rates: 0.5C on a 280 Ah pack is 140 A. The editor caps them at the BMS rating.

Tips for this chemistry

Do not start balancing below 3.40 V: on the flat part of the curve the balancer cannot tell which cell is really higher.
Keep SOC-100% at least 0.04 V below RCV so the BMS reliably resets its state of charge to 100%.
With the gentle preset, charge to 3.50 V now and then so the pack can top-balance.
JK cannot reduce the current in the cold, which is why the medium and gentle presets block charging below 5 and 10 °C. Use heating if the pack lives outdoors.

Sources

NMC / NCA (Li-ion) presets

NMC and NCA cells are rated to 4.2 V, but each 0.1 V less at the top roughly doubles the number of cycles. Their voltage slopes steadily with charge, so the balancer works over a wide range. Cells like the LG M50 allow only 0.3C charging below 25 °C.

Parameter (per cell)	Hard	Medium	Gentle
Cell OVP / recovery	4.20 / 4.05 V	4.15 / 4.00 V	4.10 / 3.90 V
Charge voltage RCV / float RFV	4.15 / 4.05 V	4.10 / 4.00 V	4.00 / 3.90 V
SOC-100% voltage	4.10 V	4.05 V	3.95 V
Cell UVP / recovery	2.80 / 3.10 V	3.00 / 3.20 V	3.20 / 3.40 V
Power-off voltage	2.70 V	2.90 V	3.10 V
SOC-0% voltage	2.90 V	3.10 V	3.30 V
Balance start / trigger	3.90 / 0.01 V	3.90 / 0.01 V	3.90 / 0.01 V
Charge over-temperature / recovery	45 / 40 °C	43 / 38 °C	40 / 35 °C
Discharge over-temperature / recovery	60 / 55 °C	55 / 50 °C	50 / 45 °C
Charge low-temperature / recovery	3 / 8 °C	5 / 10 °C	10 / 15 °C
Discharge low-temperature / recovery	-20 / -15 °C	-15 / -10 °C	-10 / -5 °C
Max charge / discharge current	0.7C / 1.0C	0.5C / 0.7C	0.3C / 0.5C

Voltages are per cell; multiply by the number of cells in series for the pack. Currents are C-rates: 0.5C on a 280 Ah pack is 140 A. The editor caps them at the BMS rating.

Tips for this chemistry

Avoid float charging: holding NMC near full shortens its life. Consider disabling float mode or keeping RFV close to the resting voltage.
Charge temperature limits are tighter than for LFP: most cells stop at 45 °C.
Check the continuous rating of your cells: 18650 and 21700 packs are often limited by the cell, not the BMS.

Sources

LTO (lithium titanate) presets

LTO works between about 1.5 and 2.8 V, lasts tens of thousands of cycles and can be charged in deep frost. Limits differ between makers: Yinlong cells allow up to 2.9 V, Toshiba SCiB only 2.7 V.

Parameter (per cell)	Hard	Medium	Gentle
Cell OVP / recovery	2.80 / 2.60 V	2.70 / 2.50 V	2.60 / 2.40 V
Charge voltage RCV / float RFV	2.70 / 2.60 V	2.60 / 2.50 V	2.50 / 2.40 V
SOC-100% voltage	2.65 V	2.55 V	2.45 V
Cell UVP / recovery	1.70 / 1.95 V	1.80 / 2.00 V	1.90 / 2.05 V
Power-off voltage	1.60 V	1.70 V	1.80 V
SOC-0% voltage	1.80 V	1.90 V	2.00 V
Balance start / trigger	2.45 / 0.01 V	2.40 / 0.01 V	2.40 / 0.01 V
Charge over-temperature / recovery	55 / 50 °C	50 / 45 °C	45 / 40 °C
Discharge over-temperature / recovery	60 / 55 °C	55 / 50 °C	50 / 45 °C
Charge low-temperature / recovery	-25 / -20 °C	-15 / -10 °C	-5 / 0 °C
Discharge low-temperature / recovery	-35 / -30 °C	-30 / -25 °C	-30 / -25 °C
Max charge / discharge current	3.0C / 3.0C	2.0C / 2.0C	1.0C / 1.0C

Voltages are per cell; multiply by the number of cells in series for the pack. Currents are C-rates: 0.5C on a 280 Ah pack is 140 A. The editor caps them at the BMS rating.

Tips for this chemistry

The hard preset (OVP 2.80 V) suits Yinlong-type cells only. For Toshiba SCiB use the medium preset.
Charging below zero is fine for LTO, but slower in the cold: keep the currents moderate in winter.
LTO cells handle high C-rates; the BMS rating is usually the real current limit.

Sources

What a preset does not change

Some settings depend on your hardware and installation, not on how hard you use the cells. The presets leave them alone:

Over-current and short-circuit delays and recovery: they depend on the inverter inrush and the wiring.
MOS over-temperature: it protects the BMS itself, not the cells.
Heating thresholds, smart sleep, communication, device name and wire resistances.
RCV and RFV times and the float mode switch: they depend on how your inverter charges.

Check before you upload

Presets are a sensible starting point, not a guarantee. Compare the values with the datasheet of your cells, the current rating of your BMS and the limits of your inverter or charger before writing them to the BMS.

Questions about JK-BMS presets

What are good JK-BMS settings for LiFePO4?

For daily solar cycling the medium preset is a good start: OVP 3.60 V, charge voltage 3.50 V, float 3.37 V, UVP 2.80 V, balancing from 3.40 V, charging allowed from 5 °C and currents of 0.5C charge and 0.7C discharge.

Does a lower charge voltage really make LiFePO4 last longer?

Yes. Most ageing happens while cells sit at a high state of charge and high temperature. Charging to 3.45 to 3.50 V per cell gives almost the same capacity as 3.65 V, because the LFP curve rises steeply only at the very end.

Why not charge LiFePO4 or NMC below 0 °C?

In the cold, lithium can plate on the anode instead of entering it. This loses capacity permanently and can cause internal shorts. Datasheets allow only tiny currents near 0 °C, and JK cannot reduce the current by temperature, so the presets stop charging a few degrees above zero.

Hard or gentle: which should I pick for a solar system?

If the pack is cycled every day, pick medium or gentle: the few percent of capacity you give up return as years of extra life. Hard makes sense for backup batteries that rarely cycle, or when the pack is too small and you need every amp-hour.

Can I use these presets with any JK BMS?

They work on JK BMS boards with the JK02 protocol and firmware 19, over Bluetooth or through a .jkcfg file. The editor changes only the selected settings, and when connected it leaves out settings your model does not have.