I want to know maximum card (SD and SDHC) that can be used with Canon Power A550 Camera.

Your camera only can use SD cards. The SDHC is a newer generation of SD cards, that need a different protocol you access the files. The newest version is the SDXC version.
SD cards never exceed 4 Gbyte. The SDHC never are bigger than 32 GD and the SDXC are over 32 GByte.
When you try to buy a SD card, the biggest you will find will be 2 GByte. I own 2 SD cards that have 4 GByte, but even I can't find them on the net any more.
The cards are from Platinum. But I even can't guaranty you the 4Gbyte will work in your camera.

Some firms used to bring out new firmware, as soon as the SDHC cards came out. I succeeded to update my TomTom to SDHC and the old thing now even accepts 16 GByte cards. But Canon did not offer an upgrade for the V550, so you stay stuck to the normal SD cards.

SD cards max out at 2GB. The S2 will not work with higher-capacity SDHC cards.

I suggest you to use a 1GB SD card. Even 2GB might be supported. Don't use SDHC cards. They are incompatible with older cameras.

SD cards max out at 2GB. The SX100IS can also use SDHC cards, which max out at 32GB.

Your fix is a very simple one. Your camera is only compatible with SD cards, and you're trying to use it with an SDHC card.

SDHC is a later technical development of the SD to allow larger capacity. Your camera was designed and made when SDHC development was still just a vague idea for the future. 512MB was all that your camera was guaranteed to work with as they were the largest capacity cards then available. You may wish to look at the user manual for yourself, page 170.

SD cards are available up to 4GB in theory, but in practice almost no SD device can go above 2GB, According to the MyMemory website your camera will accept 2GB SD cards (see details), but from experience even if it works you may find that the camera operation becomes very sluggish when the card gets more than half full. You are also likely to find that at the maximum capacity your camera is very choosy about which brands it will work with reliably. Staying at or below 1GB should ensure the maximum usability.

There is no way to update your camera to the newer standard as the SDHC card requires different internal hardware and firmware.

I hope that you've found my solution to have comprehensively answered your question, please take a moment to rate my answer.

Your camera will accept a maximum SD card capacity of 2GB. It simply isn't capable of handling anything of a larger capacity and in particular is incompatible with the more technically advanced SDHC cards.

Your fix is to either replace your camera with a later model or to stick to using SD cards with a maximum 2GB capacity.

Your camera will accept a maximum SD card capacity of 2GB. It simply isn't capable of handling anything of a larger capacity and in particular is incompatible with the more technically advanced SDHC cards.

Your fix is to either replace your camera with a later model or to stick to using SD cards with a maximum 2GB capacity.

Unfortunately, no. If it's a 4GB card, it is an SDHC card, which uses a different protocol than the 'standard' SD card. The maximum capacity of the SD protocol is 2GB, which is what the A530 is compatible with. (The SDHC protocol came out after the A530 was introduced.)

Your camera is not compatible with SDHC type cards. No 4gb cards for you. It looks like 2gb (non SDHC) cards are the biggest you can use.

Check to see if your 16GB card is an SDHC card. If it is, your camera is not compatible with SDHC. (The SDHC protocol was developed after the SD300 came out in 2004).