Question about boost convertor and how i would achieve a powerbank - Page 1
Forum section: electronics / projects

author: Bobthecooldad
author_rank: Contributor
timestamp: March 29, 2016, 09:55:50 pm
content: I want to create a power bank like this one but for the uk's 240v (http://www.amazon.com/ChargeTech-Portable-18000mAh-MacBook-ChargeAll/dp/B00MVDV9AO). my idea was to use a boost convertor to make the 5v power and follow this (http://www.instructables.com/id/Convert-Your-Old-Laptop-Battery-Into-a-Power-Bank/?ALLSTEPS) to make it however i like the idea of the plug. I wont put high amp plugs in, more for a portable laptop charger. Couldnt find boost convertors to get near 240V.If i have to add more batterys to be able to have enough current/voltage i dont mind changing the circuit

author: jeroen79
author_rank: Frequent Contributor
timestamp: March 30, 2016, 12:58:12 am
content: QuoteFor 240VACyou do not need a DC-DC boost converter but an inverter. (to convert the batteries' DC to AC)Depending on which inverter you choose you may need an intermediate DC-DC converter to boost the batteries' voltage to a higher voltage, like 12V.And before buying components you should first set somespecifications (beyond 'no high amp plugs').What voltages do you need?How much current must each supply?Any other functions?How long should the powerpack last?Then you can determine which components are needed.Keep in mind that each conversion will have losses.And be carefull about a component's specifications, especially with cheap chinese stuff.

author: Bobthecooldad
author_rank: Contributor
timestamp: March 30, 2016, 05:42:58 pm
content: i want to run a 5v phone charger off a usb (probably using a dedicated boost convertor)240vthe charger uses 2.58 so 3A is more than safebe able to recharge the batterys off micro usb(laptop uses a 42wh battery) it has a 8000mah battery so double if possible as i already have a 10,000mah battery

author: Zbig
author_rank: Frequent Contributor
timestamp: March 30, 2016, 07:02:25 pm
content: If you mean what I think you mean, that doesn't make any kind of sense. Could you please rephrase what exactly you're after, using actual English sentences?

author: jeroen79
author_rank: Frequent Contributor
timestamp: March 31, 2016, 03:46:28 am
content: This is what I think he means:Does your laptop charger draw 2,58A from the mains?Or does the laptop draw 2,58A from the charger? At what voltage?How much current do you want to draw from the USB ports?You will have to calculate how much current will flow through each part.When you are stepping voltages up or down the currents going in and out will change inversely proportinal to the voltage change.To supply 2,5A at 19V from a 3,7V battery you need more than 12,8A from your battery.The same goes for the batterycapacity.To charge a 10Ah laptopbattery at 19V from a 3,7V battery you will more than 51Ah in the batterypack.And the conversion will be less than 100% efficient so the current drawn will be higher to account for the power lost in the conversion.Further things to consider:-Phones and tablets will only draw <500mA unless cleared for more through the USB datalines. Android and iDevices do this in different ways.-You charger should be limited in how much current it draws from it's source. USB may only provide 500mA unless cleared for more.-Ensure that the circuit is powered off when the battery gets too low.-Instead of an inverter consider using a DC-DC converter to charge the laptop. That may take out one or two conversion steps.-Think about how you will arrange you batteries. All parallel to give 3,7V? In series to give a higher voltage?-Maybe add a 12V lighter socket.