This guide covers the settings, wiring and failure modes of the JK-PB2A16S-20P V19 BMS in a 16S LiFePO4 home storage pack. All specification figures come from Jikong's official document V19.0.1. Download the PDF →
Written for customers of our 48V 16S DIY Battery Box, but the settings apply to any pack using this board. If something here contradicts your cell manufacturer's datasheet, follow the datasheet.
Change this before your first charge
The factory charge low-temperature protection is −20 °C. Set it to 0 °C.
That −20 °C default is a generic value spanning three chemistries — the same board runs LiFePO4, ternary lithium and LTO. For LiFePO4 it is dangerous. Charging below 0 °C drives lithium plating on the anode: permanent capacity loss, and in the worst case an internal short. The damage is cumulative and invisible until the pack has visibly lost range.
If your pack lives in an unheated garage or outbuilding anywhere north of the Alps, this one setting is the difference between a pack that lasts a decade and one that quietly dies over two winters.
Factory defaults vs. recommended settings
Left column is what the BMS ships with, per specification section 4.2. Right column is what we recommend for 280–320Ah LiFePO4 cells in a cycling home storage pack.
| Parameter | Factory | Recommended | Why |
|---|---|---|---|
| Charge low-temp protection | −20 °C | 0 °C | See above. Change this first. |
| Charge low-temp recovery | −10 °C | 5 °C | Hysteresis above the cut-off, so it doesn't chatter at the threshold. |
| Cell overcharge voltage | 3.60 V | 3.55 V | 3.65 V is the cell ceiling. Backing off costs almost no usable capacity and meaningfully extends cycle life. |
| Overcharge recovery | 3.54 V | 3.40 V | Prevents rapid re-trigger cycling at the top of charge. |
| Cell undervoltage protection | 2.60 V | 2.80 V | The flat part of the LiFePO4 curve ends well above 2.6 V. Stopping at 2.8 V leaves almost all capacity available and keeps you off the cliff. |
| Undervoltage recovery | 2.65 V | 3.00 V | Requires real recharge before discharge resumes. |
| Automatic shutdown voltage | 2.50 V | 2.50 V | Leave as is. |
| SOC 100% voltage | 3.50 V | 3.45 V | Aligns reported SOC with a real absorption endpoint. |
| SOC 0% voltage | 2.60 V | 2.90 V | Makes reported SOC match usable energy rather than theoretical. |
| Balance start voltage | 3.00 V | 3.40 V | Balancing in the flat region is guesswork. Above 3.4 V, voltage actually tracks state of charge. |
| Balance trigger delta | 10 mV | 10 mV | Leave as is. Well matched to the board's ±3 mV acquisition accuracy. |
| Charge overcurrent | — | 100–150 A | Set to your charge source, not the board maximum. |
| Discharge overcurrent | — | 200 A | Or your cable rating, if lower. |
| Discharge overcurrent delay | 300 s | 300 s | Worth knowing: an overcurrent condition persists five minutes before cut-off. Size your cable to survive that, not just to carry rated current. |
| Charge over-temperature | 70 °C | 55 °C | 70 °C is a board limit, not a cell limit. |
| Discharge over-temperature | 70 °C | 60 °C | Same reasoning. |
| MOSFET over-temperature | 100 °C | 100 °C | Leave as is. This one protects the board. |
Settings are applied in the JK BMS app over Bluetooth (Android 7 or later, or iOS) or on the 4.3" display. Set the battery type to LiFePO4 first, then the cell count and capacity, then work down this table.
The five problems we get asked about most
1. "The BMS is dead out of the box"
It almost certainly isn't. The board has no power switch and ships unactivated. It is designed for charge activation: connect a charger at roughly 2 V above pack voltage and it wakes. It also wakes from the display button or the button on the interface board. This is by a wide margin our most common false alarm.
2. "It tripped short-circuit protection when I connected the inverter"
Normal, and documented by Jikong. Inverters have large input capacitors; the inrush on first connection can exceed the short-circuit threshold. First confirm there is genuinely no short in the external wiring, then increase the short-circuit protection delay from its 5 µs default. The same applies on the charge side with some chargers.
3. "It went to sleep and I can't find it"
Intelligent sleep activates after 26 consecutive hours with both charge and discharge current below 1 A, dropping consumption from 1100 mW to 12 mW. Wake it with the button or a charger. You can disable sleep entirely in the app's BMS control page — worth doing on a grid-tied pack that may idle for long periods.
4. "Charging is stuck at about 10 A"
That is the charge current-limiting function working as designed: after a charge overcurrent event it holds charge current near 10 A to protect the pack. Find out why the overcurrent happened rather than disabling the feature. Usually the configured continuous charge current is set below what the charge source actually delivers.
5. "One cell channel reads zero but the cell is fine"
Check pin 3 of connector P8 — it is a reserved pin, not a cell tap. Count your harness positions against the wiring diagram before assuming a hardware fault. On V19 the sense connectors are colour-coded, which makes offset insertion much harder, but not impossible.
Running packs in parallel
The board supports 16 packs on the RS485-2 bus — roughly 229 kWh at 314Ah per pack.
Each BMS gets a unique address from 0 to 15, set on the 4-position DIP switch. Address 0 is the master; 1 through 15 are slaves. Packs daisy-chain RJ45 to RJ45 on RS485-2. A USB-to-RS485 cable from the master reaches Jikong's PC monitoring software, which polls every pack onto one screen. The master's L6 LED blinks; each slave's L6 LED starts blinking once it has successfully linked to the master — a quick way to confirm the bus is healthy without opening the software.
Before you parallel anything:
- Check your inverter's supported pack count. Many hybrid inverters cap at 6, 10 or 16 regardless of what the BMS allows, and that number is usually the real limit.
- Bring all packs to within 0.5 V of each other before the first parallel connection, or inrush between packs will trip breakers.
- Use equal-length cables from each pack to the busbar so current shares evenly.
- Set the DIP addresses before powering up, not after.
