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 PWM5 Charge Controller is now available in my new shop - click on the shop link at the top of the page. There are two items for sale - both identical, one is priced in pounds and is intended for UK buyers, and the other is priced in US dollars and is for purchasers [...]
PWM for precise voltage control
The PWM5 uses pulse width modulation to connect and disconnect solar panel and battery 122 times a second. This allows for very precise control - battery voltage is held at the optimum level. Some charge controllers just disconnect when an upper voltage is reached.
Bulk, Saturation and Float
The PWM5 has a full [...]
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 [...]
This is the finished PWM5 Solar Charge Controller
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 [...]