Thanks in advance.
Virtually all controllers use PWM so if it doesn't say it it MPPT then it will not be . MPPT costs money so if you have found the bargain of the century it will not be MPPT. Flux
When you go a bit more refined you need to hold volts at a certain level for the absorbtion phase then you reduce the level to float.
To maintain a precise voltage you can use a linear regulator, that is very precise, but dissipates a lot of heat in the control device.
The battery thinks it is at constant voltage if you switch the charge on and off at a fairly high frequency. The various PWM schemes just alter the on/off ratio to keep a constant mean voltage on the battery. The control element is on or off and dissipates little power compared with a linear device.
The next stage of complexity is to include an inductor in the dc path and a freewheel diode to maintain conduction when the switch is off. This now becomes a buck converter and supplies a smooth dc to the battery rather than a series of chopped pulses. This costs money and is rarely used as there is some evidence that batteries don't mind the chopped waveform and in fact it may be beneficial.
This is ok as long as the panel matches the battery fairly well. Most panels are designed to produce peak power just above fully charged battery volts. With a low battery or in the winter when the panels are cold, the voltage difference is greater than the ideal and matching the voltage will increase power transfer.
This is where your buck converter comes into its own, it acts much as a dc transformer and can transform a source with high voltage into one of lower voltage and higher current.
If this is arranged so that the panel works at its maximum power point then you have a maximum power point converter. Conditions are constantly changing and to be able to keep at this maximum power point you need a circuit to track that point, hence MPPT.
So what this means in real life is that a PWM controller will be on/off but at a fairly high frequency but will just chop the current.
A MPPT controller will switch at an even higher frequency, again PWM but the charge current will be fairly smooth dc as it will use the inductor and diode for energy recovery during the off periods. It will also have a clever circuit to load the solar cell to maximum power point and it will transfer this power to the demanded battery volts set by the charge algorythm.
Sorry this has got long winded but you wouldn't accept the simple answer that PWM doesn't mean MPPT. Flux[ Parent ]
Can you recommend a charge controller then? Either a decent non-MPPT controller or a decent but realativly cheap MPPT controller. Can you also post somewhere I can buy them, website etc. (Im in the UK so I need it to be shipped there).
After X-Mas I plan to upgrade my batteries from 17.2Ah to 66Ah (2x33Ah) so I need as much power as I can get from my 60w array into the batteries.
Thanks in advance.http://www.repowered.co.uk - My Renewable Energy site. msn[at]m3ezw.co.uk - my msn if you want a chat.[ Parent ]
If you are at 12v with just a small set up I really don't think you will see any benefit from MPPT. It comes into its real value with higher voltage panels.
To gain real benefit at 12v the converter needs to be up in the 95% efficiency range and that costs real money and for little reward, I can't help feeling that the extra money could be better spent on more panels.
Have a look at Wind & Sun uk for controllers. Flux[ Parent ]
BadmoonI just wanna have some fun, maybe learn something new every day and make some friends in the process.[ Parent ]
