U1-12RJ Valence LFP 12V 40Ah 512Wh Battery with BMS

(1 customer review)



A beginner friendly 12V battery with over voltage, under voltage, temperature, and overcurrent protection built in. Easy to series together for higher voltage applications.

Price per kWh: $160/kWh

Shipping: Free Ground

Warranty: 6 Months, Extendable

These batteries were removed from Medical Carts at the end of their service life. All bad(red blinking, or low voltage) modules are recycled. Only green blinking modules are retained for Refurbishment. All acceptable modules are capacity tested and charged to keep the voltage from dropping too low during storage. These modules have the Valance warranty sticker over the BMS cover intact, none of them are opened or reset.


  • Voltage (nominal) 12.8 V
  • Capacity @ C/5, 23 °C 40 Ah
  • Energy 576 Wh
  • Discharge Cont./Peak (30 sec) 30 A / 80 A
  • Discharge Cutoff Voltage 10 V
  • Recommended Charge Voltage 20 A
  • Charge Float Voltage Range 13.8 - 14.6 V
  • Discharge Temperature -10 °C to 45 °C
  • Charge Temperature 0 °C to 45 °C
  • Self Discharge @ 25 °C < 2% per month
  • Terminal Hardware M6 x 1.0
  • Terminal Torque 12.4 Nm 110 in-lbs
  • Plastic Case Flame Retardant
  • IP Rating IP56


  • Thousands of cycles, 80% DOD
  • Create systems 12 - 48 V
  • Series connection up to four batteries(48 V)
  • Automatic cell monitoring & balancing
  • Temperature monitoring of cells
  • Rugged mechanical design
  • built in overcharge, over-discharge and short circuit conditions
  • Maintenance-free
  • saftey profile of lithium iron phosphate battery chemistry

Height: 183 mm 7.20”
Width: 131 mm 5.16”
Length: 197 mm 7.76”
Weight: 6.4 kg 14.1 lbs

Usability Details

The battery includes charging and discharging protection, MOSFETs inside will cut-off the power if more then 30A is applied for longer than 30 seconds. It will also disconnect the battery if it is being overcharged, and will not power a load if it is being over discharged. Separately controlled MOSFETs will only prevent one or the other at a time, so you can still charge it is it is too low, but you will not be able to discharge it, and vise versa. Charge will disconnect if any cell reaches 3.9V, and reconnect when the voltage drops to 3.7V. Discharge will disconnect when any cell reaches 2.45V, but it will still charge. This battery is a ready to go solution for any application with a continuous load of under 30 A.

LED indicator guide

  • Green Quick (0.5s): Idle, all good.
  • Green Long (1s): Charging or discharging, all good.
  • Yellow(looks like red and green): Charge level less than %20SoC recharge immediately, or battery is near thermal limit and is close to overheating.
  • Red: Low Charge level or issue with the battery or BMS. See Low Voltage Recharge instructions.
  • No Light: Battery charge depleted to %0 and BMS shut off. See Low Voltage Recharge instructions.

Low Voltage Recharge instructions:

You will need a power supply with adjustable voltage and current in order to properly recharge the battery. Other charges may work, but it is no guarantee because the battery BMS will fight it. It is not recommended to hook up a charged 12V to the battery terminals, it will cause the BMS to shut off from an overcurrent fault and will diminish the life of the batteries significantly if charged with a lot of current while at a low charge level. Apply a charge of around 2A at 14V. The BMS will flash RED/GREEN for a few seconds and begin to allow a small charge of current through. After the cells reach a voltage above 2.7V, the charge limit will be removed and light turns green.  Allow the voltage to rise to 11V before increasing the current. If it does not begin charging after 1 min of the power supply being hooked up, it might have a cell or BMS issue.

BMS will automatically balance the cells within one module during the top of the charge. Will not balance between modules when hooked up in series, only in parallel. If wiring these modules in series, please see the balancer we have listed to keep your batteries balanced. You would need the 12V version, one for every module you have in series.

Price Chart

Prices varied by kWh of modules.

Valence U1-12RJ Price/kWh 160
Ah kWh Price/Module
30 0.384 61.44
31 0.397 63.49
32 0.41 65.54
33 0.422 67.58
34 0.435 69.63
35 0.448 71.68
Valence U1-12RJ Price/kWh 190
Ah kWh Price/Module
36 0.461 87.55
37 0.474 89.98
38 0.486 92.42
39 0.499 94.85
40 0.512 97.28
Shipping: Free - the cost of shipping to you is included with your purchase.
Additional information
Amp. hour

30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41

1 review for U1-12RJ Valence LFP 12V 40Ah 512Wh Battery with BMS

  1. Joshua H (verified owner)

    Great batteries. Planning on buying more.

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