DC/DC Converter/Charger and Cell Log 8 Breakout Module

I’ve been working on the idea of a DC-DC charger for a long time now, however I could never settle on a feature set to design the PCB around.  As the project gets closer to actual completion I decided to just keep it simple.  The PCB is more of a breakout board for the Synqor DC/DC converter modules and allows them to be securely mounted with nice terminals and simple connections.

The PCB is designed to hold 8 converters in two groups.  This allows them to be put in series or parallel depending on the intended use.  Putting them in series makes an 8 cell 25A LiFePO4 charger that is adjustable from 3.3-3.65v. Putting them in parallel makes a 50A 12-15V dc/dc converter with an input range of 36-75 OR 72-150v.  Using 1 1/2 boards (12 converters) makes a 75A dc/dc converter with a 108-225v input range.  I will be using this configuration for my first battery pack in the car (56 series LiFePO4 cells)  I will also be using a 50 or 100A version of this module to charge the 12v modules that will go in to the main battery pack.

I still wanted to be able to plug in a Cell Log 8 for quick testing or monitoring so the plug is included, but does not take up the same kind of board space as the old design.

There is a trim pot and test points to set the voltage on each channel.  For less accurate results the Cell Log 8 can be referenced to set the voltage of each channel very quickly.  These Synqor modules don’t have a heat sink, but the still need cooling, I will be designing a fan mount for a 120mm fan to be directly mounted to the PCB, the fan will be powered by the same 12v signal that turns on the board.

 

The main reason the Cell Log 8’s were removed from permanent mounting on the PCB is because of a 2nd PCB I had in the works.  This is simply a Cell Log 8 Breakout Module that allows up to 4 cell logs to be mounted to a PCB with real terminals for connecting wires, as well as the required relays and connections for using the alarms and turning the Cell Logs on and off.

The design is simple and all traces were routed by hand for direct routing and minimum use of vias.

The stock alarm wire that comes with the Cell Logs is shortened and plugged into a connector on the bottom of the PCB.

The PCB layout is simple and compact, with sturdy terminals for all connections.

I’m in the process of testing both boards right now, but as you see below everything is working as it should, the charger boards are adjusted to ~3.5v and the cell logs are reading all channels.

For testing since I don’t have a 32S battery pack assembled yet I simply used 32 channels worth of the DC/DC charger (4 compact boards).

This is actually better than using a battery pack for testing since I can vary the voltage of each cell to test the various alarms and make sure everything is working as it should.

Once I get the warning lights or buzzer hooked up to the alarms I’ll do a short video showing the 3 different alarm states that can be used with the cell logs and how that can be useful on your dashboard to see what cell group is tripping the alarm.  With this type of set up you could use one Logging Cell Log 8 and the remaining can be the less expensive Monitoring only Cell Log 8’s.  If an alarm was triggered you will be able to tell what group the alarm came from and move the Logger to that location.

 

Once I’m finished testing both of these boards will be available for sale in the store.  The Cell Log 8 will be available in a populated form with all connectors and relays, but without the Cell Log 8’s. The DC/DC converter board will be available with the relay, pots and connectors but without the DC/DC converter modules.  I will be supplying a list of compatible dc/dc converters that would work with this board.

 

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