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Bench Top Power Supply




As I mentioned earlier I am a believer that if venturing into DIY LiFePO4 it should be done as a SYSTEM. Part of that system should include funds for a bench top power supply. In my opinion this tool should be a pre-requisite for DIY LFP.. Can you make do without? Sure, and I am certain Bode Miller could ski with only one leg, but why..? In the whole scheme of things they are inexpensive and they have multiple uses not just for charging or top balancing LFP.


Two of the bench top power supplies I use are made by Mastech, specifically the Mastech EX series. I own a 3030EX and a 3050EX. These are not the fanciest or the most expensive power supplies, and voltage setting is tedious due to the lack of a voltage sensing circuit, but they work and they work pretty well especially for the price.


Years ago these devices would have run four figures each but today they are very reasonably priced.. A Mastech 3020EX (30V X 20A) will run you just $219.95. It will save you $400.00 in your time fiddling with top balancing alone. You will be looking for a 0-30V and 0-10A plus model. This is my 3050EX. The EX in the Mastech line signifies these units are specifically designed for charging batteries, usually Li batteries. The dial second from the left is EX knob or the over voltage protection dial. Set this dial and the power supply will protect itself.


While the Mastech line represents a great value I tend to prefer my BK Precision Model 1900. The BK Precision 1900 is a 1-16V, 60A variable power supply with dedicated voltage sensing leads. The voltage sense leads to me are really the driving factor as you get far more accurate voltage at the terminals without worrying about voltage drop through the cables & terminals. It is a very nice piece of gear but runs close to $600.00. I bought mine from Test Equipment Depot.


Knobs and Displays:


Left Digital Display = Current Output

Right Digital Display = Voltage

Red Light = Constant Voltage Mode (power supply is limiting voltage to 13.8V)

Left Knob = Current Control Dial

Second From left Knob = Over Voltage Limit

Third From Left Knob = Constant Voltage Fine Tune Adjustment

Right Knob = Constant Voltage Coarse Tune Adjustment


As you can see in this picture with 15A of current flowing the Mastech and the Fluke are in close agreement but I still trust my Fluke a lot more than the voltage display on the power supply.


TIP: When charging LFP cells or banks with a bench top power supply PLEASE dial the current back by about 20%. This will allow the power supply to run almost indefinitely and not cause undue wear and tear on the unit. I run my 30A model at 24A and my 50A model at 40A... I often parallel them and charge at 64A when doing cycle testing....


Nothing makes top balancing easier than a bench top power supply:


#1 Charge individual cells to .05V below max top balance voltage and allow current to taper


#2 Wire cells in parallel.


#3 Charge cells to max top balance voltage and let current go to next to nothing Winston = 3.65V / CALB = 3.6V etc.


#4 Done






other sizes: small medium large original auto
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Jim Healy 08-Sep-2015 19:36
Both in terms of the elapsed time top balancing seems to require, and in terms of the space test equipment requires, what would you suggest as an alternative to bench top balancing for those who live aboard and do not have homes, let alone shops with test equipment? Thanks!
BJ 09-Jan-2015 20:06
First, very helpful article - thanks for sharing. The Mastech power supply sounded appealing but I ended up going with a single cell lithium charger instead for a few reasons: 1- less expensive 2- less chance of making a mistake/over-charing as it automatically shuts off 3- smaller, so I'll keep it onboard at all times (planning on extended cruising). Downsides, it's less useful than an adjustable power supply. I ended up with an Intelligent 10 amp charger pre-programmed for the CalB CA series. I'm 4 days into balancing an 800 amp hour bank, and not being able to apply a balancing charge 24/7 would really slow things down. (I pulled 4 cells out to test the system first which although gave me peace of mind, made more work in the end). One other comment- I have a BMS that logs lots of data 24/7 which has been extremely useful in troubleshooting and just figuring out what's going on with the bank and chargers (the OrionJR if anyone is curious).