Why Choose the JBD BMS?
The JBD BMS is well known in the industry for its high standard of quality, and is commonly used on medical equipment. The ease of installation, reliability, and low cost make these units a first choice for many DIY builders. Some systems demand large amounts of current, and while the JBD is not a particularly high current model (100A ~ 200A), multiple units can easily be connected in parallel for increased current handling capacity. The low cost also makes it easy to include monitoring on every cell in a system, paralleling on the pack level instead of cell level. This configuration allows you to see a problem with a cell and isolate a section of a pack while continuing operation, so a repair can be made long before a cascading failure occurs. Monitoring and programming this BMS is very easy courtesy of Bluetooth connectivity and/or a USB cable to connect to a PC. The JBD has two temperature probes, both providing user configurable low and high-temp charging protection.
Which variation of BMS do I need?
Currently we offer three versions of the JBD units; the 4s150A, the 8s100A, and the 16s100A versions.
Since each cell in a LFP (LiFePO4) pack has a nominal voltage around 3 Volts, you need 4 cells in order to make a 12 Volt battery, 8 cells to make 24 Volts, and 16 cells to make 48 Volt packs. These cells would be connected in a series connection, so that the voltage level is increased with each cell. Let’s say you plan to use 4 cells to make a 12 Volt pack; you would need a 4s model of BMS in order to match the 4s configuration of the battery pack. An 8s BMS is not backward compatible with a 4s pack, just like a 4s BMS is not compatible with a 8s battery pack.
If you had 8 cells, but you still wanted to build a 12V pack, you have two options to choose from. The cells could be connected in parallel groups of two cells, then connected in series and managed by one single BMS, but the drawback to this is the loss of individual cell monitoring. The second option is to build two 12 Volt battery packs, each with their own BMS – then connect the two packs in parallel. There is no theoretical limit as to how many BMS units can be put in parallel, but good practice would be to have larger battery cells to increase capacity, decreasing the number of individual components that may lead to a system failure.
What Current Rating Is Appropriate For Me?
This depends on your application entirely. The current rating of a BMS is how many amps of current the BMS can continuously handle. If for example, you are building a battery for an RV, and you only plan to run light-duty applications such as your lights, fans, fridge & furnace, then even a 50A BMS would likely be sufficient. The BMS current rating needs to be larger than the worst-scenario maximum current draw of all the loads, otherwise the overload protection in the BMS will trip, shutting everything down. It is always acceptable to use a BMS that is oversized. In the application noted above, using a 50A or 150A BMS would perform equally.
Let’s say however, you decide to add a 2000 Watt 12 Volt to 120V inverter to your RV to power appliances such as a microwave or coffee pot – This inverter at full load would draw approximately 200 amps on the 12V input. Neither a 50 Amp or 150 Amp BMS is sufficient. Now, it is required to parallel multiple BMS units for increased current capacity, or select a larger BMS unit. Good engineering practice is to only utilize 75% of the BMS’s continuous current rating when connecting in parallel, to prevent one BMS from cutting out prematurely due to real-world differences in wire resistance and length. In other words, 2 of the 150 Amp BMS units connected in parallel should only be considered equivalent to a 225 Amp BMS.
Accessories For The BMS
While other vendors may not include the same, every JBD BMS unit from CurrentConnected includes the main balance harness, a Bluetooth Dongle with Connection Cable, as well as a USB monitoring/programming cable assembly for connecting to a PC.
Since our JBD BMS units utilize screw terminals for the main power connections instead of random wires soldered into the circuit board, heavy-gauge wiring will be needed to connect the B- terminals to Cell #1 negative as well as C-/P- to your load & charger. Please refer to our wiring guide for further reference of wire selection and connection details.
Note To Customer:
Before shipping, every BMS is tested for full functionality and quality assurance. We also pre-program for optimal LiFePO4 parameters as well as preform a voltage & current calibration. If you would like the BMS pre-programmed for the capacity of your cells, please specify the size (Ah) of your batteries in the order notes. We will input this data during the testing & quality assurance process so that you have a “turn-key” system right out of the box.