Inspired by Christophe Huberts system which you can read all about here http://www.diyesskit.com/p/what-is-it.html
Brief specs of the first stage of the system:-
* 5KW LifePO4 battery pack
* 10A ~ 100A LifePO4 battery charger (adjustable constant current)
* 2 x 600W output Grid Tie inverters
* 100A solid state relays for the battery charger and battery* 40A solid state relays for the AC input to the charger, AC output of the inverters and DC input of the inverters
* 100A current shunt
* 2 x AC induction current sensors
* Raspberry PI micro computer controller
* 4 x 16 character display for the PI
* 32 digital I/O board for the PI
* 8 analogue input, 8 analogue output board for the PI
Some pictures:-
The 5KW LifePO4 battery pack
(it has 16 x 3.2V 200Ah flat pack cells in it in a 2P8S configuration for 5120W capacity, each cell is 2.5Kg, making the total weight 40Kg - not exactly nice and light)
The two 600W Grid Tie inverters
All the SS relays
The 24V, 100A battery charger
The charger is in bits as I want to check it over very thoroughly before using it. Two reasons for doing this, it was bought from China, and from past experience their QC isn't as comprehensive as we are used too, and secondly the journey from China to the UK may well have shaken things loose or caused some solder joints to crack - as you can see the components aren't exactly small and if they are jarred, the solder joints can easily crack.
Checking it over carefully now can make the difference between it going bang when I plug it in and it becoming a $600 paperweight, and it lasting for years.
After a quick check of the components in it (things like capacitors rated to 105 degrees C rather than 115, or 125, the additional thick wire soldered to the high current tracks on the PCB), leads me to believe that even though it may be able to charge at 100A, it will extend it's life a lot if I use it to, say, 75A maximum.
A variable current LiPo charger was chosen as I can drive the charge current control directly from the PI controller, which will allow me to exactly match the power taken by the charger to the excess power generated by the solar panels. The alternative was to have 'x' smaller (say 10A) chargers and turn more and more of them on or off as the excess power from the solar panels allowed. The latter would work fine but cannot perfectly match the solar excess power to the power going into the battery. Deciding to go with this type of charger is a bit of a gamble though, they aren't cheap and I hope the efficiency of the charger and the extra charge I can get into the battery on a dull day will be worth it. Time will tell.
After I've checked over the charger I have a couple more bits to get (better crimp connectors, 200A fuses, more cable), finish the initial version of the controller code, finish making the buss bars and decide how to lay everything out and find a heavy duty box to put everything in.
Richard
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