2. Do all of the models listed in the quotation have the over current over voltage protection?

Re: Yes , all the model with over current over voltage protection. 

  1. How would you recommend user to decide to choose over current over voltage protection, charging protocol or Led light indicator with automatic power off protection?

Re: If the clients need to charge the Apple series, please do not recommend Aseries( over-current, over-voltage protection) , and the clients need to charge all brand( tablets and mobile phones) which can choose B  series charging protocol.  Certainly, some clients request the clearly LED indicator +Automatic power-off protection, depending on the clients budgets( school or education area, you can recommend). 

  1. May I ask why the A series is not suitable for Apple products such as iPad, iPod, iPhone?

Re: Cuz the chip which without the charging protocol, some clients which require the multi-ports for mass charging and mass aging testing, they prefer to choose the cheapest one. We also resell this in the domestic market for the company, they use it for mass testing for their product. The chip without charging protocol, if you charge the Apple products, the current will be 1A, it is not enough for charging and speed is very slow. 

  1. B and D series stated in your list are suitable for all brand and devices such as apple products, drones, bluetooth speakers?

Re: B and D with charging protocol chip, so they support most brand, especially, iphone, SamSung, Huawei  etc.  each brand with their charging agreement, the usb charger should have the charging protocol chip to support the charge.  so the chip can recoganize the devices current and provide the suitable current as per the devices battery require. 

I have a client who wants to know if the charging efficiency goes down of the charging cable is longer than 12 feet?  They want to use long charging cables with the 20 plug unit.

Re: Yes, the charging cables which is longer the charging speed will be slow and time will be taken longer. Generally speaking, we recommend the clients use the orginal device’s cable ( especially the phones and tablets).

Certainly, using the longer charging cables can charge the devices, depending on the clients whether can accept the low speed charge. In addition, if the clients use the good quality charging cables which is better.