More Diodes and Digital Programmable Voltmeter arrive in the mail

More components arrived in the mail yestedray: Diodes and Dual Relay Programmable Voltmeter for my new DIY project : LiFePO4 Charge Controller

New DIY Project: A LiFePO4 Charge Controller

A new project I have been working on these last weeks: A LiFePO4 Charge Controller to be able to Charge LiFePO4 cells from any source: Solar, Wind, AC Charger, and Discharge into anything

Fully Automated and tunable of course to suit any numbers of cells 

Ready for high current with quality top of the line components

New dedicated website: http://www.LiFePO4ChargeController.com

New : LiFePO4 DIY ESS Technical Diagram

Just added this diagram to the newly created 'How does it Work ?' page on my DIY ESS Kit blog, after a French person requested a technical overview of the system; Good suggestion, thanks !

LiFePO4 ESS - CALB Cells Voltage Check

Here is another video of me going through the 8 CALB CA180FI cells to check their individual voltage, and it is exactly the same at 3.25V, while the ESS is on

So: no BMS, just a Bottom Balancing done once in february when I got the cells and a pack voltage kept between 3V and 3.55V times the number of cells; Now, after 4 months of use, they are still perfectly in balance at the same voltage

Watching the LiFePO4 DIY ESS Charge all day at home, from work, and back home

When my LiFePO4 DIY ESS battery pack is depleted, at 24V, the programmable voltmeter's low limit relay opens, the contactor opens, and the Grid Tie Inverter mode is shut off (low red led ON); This is what happended here

Immediately, the pack voltage goes back up and settles down around 25.4V

Now in the morning, for testing purposes, I siwthed the ESS to Forced Charge Mode, and all the chargers then are charging the battery pack

Since I can not stay all day next to it, I usually leave Karotz watch it for me and take a look remotely from time to time while away from home

08:20

At work 

10:07

11:31

16:34

it then continues and goes up pretty quickly after 27.5V to 28V where the upper limit voltage is reached and the programmable voltmeter opens its other relay, opening the charger side contactor, and terminating the charge completely

and the total Enegry used to charge fully the pack is 5kWh

DIY ESS - Watching the End of Charge Remotely with Karotz

After charging last night for several hours during off-peak hours, this morning I turned on the ESS and it went to GTI Mode during shower and breakfast

When I left home for work, and switched it to Forced Charge Mode and placed Karotz - rabbit webcam - in front of the voltmeter

The battery pack voltage climbed nicely all morning ...



until it reached the programmed charge voltage limit of 28V (3.5V per cell times 8 cells), as you can see the upper left red is ON, meaning the voltmeter relay opened and the Charge Contactor opened as well, and all the chargers stop

As a result, the pack voltage drops slowly to 26.6V (3.32V per cell times 8 cells), which is normal ...

After and hour or so, I still have the same pack voltage of 26.6V and it does not seem to move anymore at this point

Tonight, full discharge of the ESS battery pack in GTI Mode - Normal Automatic Mode -

Low Cost Coil Economyzer Test for Tyco Kilovac EV200A1ANA

I am still in search of an economizer for my new Tyco Kilovac EV200A1ANA

Last night, I tested different resistor values along with this 4700uF capacitor - I got for my Grid Tie Inverter repair previously - and found that the simple economizer described in this DIY Electric Car thread


seems to work . I could not find a resistor that works so I used this air dryer resistive wire again - alreday used on my mini bottom balancer - and cut a piece that was 10Ohms;

Closing the circuit bypassing the economizer, the relay closes and is using 3,5A

With the economizer, the contactor is closing and only 1A is going through the circuit - instead of 3,5A with no economizer -   

1A at 12V = 12W

I will have to try with 20Ohms and see if what it does ... The idea is to leave the relay closed using minimum current, thus minimum power

Last charge for my 3 LiFePO4 cells pack

As explained in my last post, it is time charge the 3 LiFePO4 cells pack again, but for the last time, because now I think I tested them enough and will put them for sell online

I do not know if I already wrote this, but I am using two 12V Mascot chargers in parallel to charge twice faster this pack, and, of course, I am carefully following the voltage using my Bottom Balancer for this as a voltmeter

A clear indication of the voltage

The two Mascot (Norvegian) chargers working together

Parallel charging and single cell voltage reading

Exercising the remaining 3 Mottcell LiFePO4 cells

After selling my Enginer Prius PHEV Kit 32 LiFePO4 Mottcell 39Ah cells, these are the only good cells left, and I am "exercising" them by Bottom Blancing them, Charging them and Discharging them

For that I use my home made small (and cheap) Bottom Balancer, one or two Lead Acid Chargers and of course watch carfully so that I do not overcharge them, and for that I use the Bottom Balancer as a voltmeter display only, leaving the load/resistor switch OFF

For Discharging I found a way to re-use the energy by wiring the 3 cells pack to a 12V car socket, and charge iPhones and iPad with it, slowly draining it; The pack is 3 x 3,2V nominal which shows 10V more or less fully charged and I will stop when it reaches 3 x 3V = 9V and will recharge from there

Eventually I will sell these 3 cells after checking that they are fine ... and they seems to be ...

Smallest & Cheapest LiFePO4 Cell Bottom Balancer

Here is a shrunk version of my original automatic bottom balancing device

Automotive relay, 3 resistive wire from an old air dryer, and 2 small switches

A red flashing LED to show when we are  in drain mode 

Some welding

Resistors and switches close up

and the final product
There is an input for a 12V power supply, I used a solar charged 12V battery for that 

Now some testing with remaining LiFePO4 cells 

Power switch ON

View from the top

Added a little extra cover on the red wire to avoid damage from the resistor heating up

From the left side

From the right side

I later on added a little piece of aluminum to dissipate the heat a little bit more

The resistors are going up to 75°C and more or less 4A are going through them :

Measured Resistance: 0.8Ohms 

Current: I = U / R = 3.2 / 0.8 = 4 Amps

It works fine and I drained one cell yesterday with it, in 2 hours I think

The total cost is close to 60 USD:

Programmable dual relay voltmeter                                             47.50

Automotive relay 12V / 30A                                                        3

Red flashing LED                                                                         5

Switches (x2)                                                                               2

Resistive wires                                                                              free

Wires and connections                                                                  3

Battery Clamps                                                                             free

Japanese fishcake board                                                               free 

                                                                                                 -------

Total                                                                                          60.5 USD