It may be possible to upgrade the specification of the PWM5 to a maximum current more than 4.8 amps. I really want to rate it for use with solar panels up to 100 watts which have a short circuit current around 6 amps.
The 4.8 amp current limit is pretty arbitrary really. It was chosen to [...]
The charge controller project has largely exited the design and test phase and entered a production oriented period of activity. However, that doesn’t mean there aren’t any design challenges still to tackle. At each stage of production there are processes that take time, and opportunities exist for the design of production aids or ‘jigs’.
One such jig [...]
Time to have another look at the battery voltage measurement circuit - and in particular the behaviour of the zener diode.
The purpose of the zener diode is to shift the relevant range of battery voltages (between 10 and 15 volts) to the 0 to 5 volt range of the PICs analogue to digital converter. About [...]
We need to model the charging process more closely to determine when to switch between saturation and float charge modes.
The purpose of the charge controller is to fill the battery with charge as quickly as possible without causing any damage.
Letting the battery voltage rise to 13.5 volts, then holding it there using PWM is fine, but the battery saturates (fills with charge) slowly. Allowing the voltage to rise initially to 14.4 volts, then dropping [...]
Continue reading about Saturation Charge and External Influences
At the moment, battery voltage measurements are not synchronised to the 122Hz PWM switching frequency. In fact, an analogue to digital conversion is carried out just as soon as the previous conversion is completed. This results in dozens of samples being taken throughout the PWM cycle.
In the current firmware version, these voltage samples are written [...]
The prototypes are ready - 3 of them, in their glossy black heatshrink covers - all looking good.
Now what’s needed is a small self-adhesive vinyl label which I can stick on the front to give the charge controller a really professional look. Fortunately, I know a bloke who’s got a machine that can both print [...]
I’m making up a small number of pre-production prototypes so I can test various configurations of multiple charge controllers. These will be:
One solar panel, two charge controllers, two batteries - this was suggested by a boat enthusiast who wants to use a single solar panel to keep two batteries (used for different purposes) topped up.
Two [...]
While I was looking for a solution to the EMC issue, I thought about turning the regular 122Hz PWM frequency into something more like white noise. The idea was to spread the spectrum of the emmited radiation so that at any one frequency, the signal would be weaker.
It didn’t work. The intended effect was minimal, [...]