step-up 12V DC output from jump starter power bank to 19 V - Page 1
Forum section: electronics / projects

author: teridon
author_rank: Newbie
timestamp: April 24, 2018, 07:40:38 pm
content: I'd like to charge my laptop (ASUS UX501VW) from a power bank with a 12V/10A DC output (specificallyhttps://www.amazon.com/gp/product/B01HPCB2FW)I can't find a commercial adapter that does the job, so I figured I'd try to build one.I found this regulatorhttps://www.amazon.com/DROK-Converter-Voltage-Transformer-Constant/dp/B079CDY2R8, but it's only rated at 6A. However, I think that since the power brick that comes with the laptop is 19V/6.32A, this is probably OK. Is it?Also, I'm going to need the correct barrel adapters. I can't find official specs, but I measured them with calipers.The laptop one is.. weird? It's not a standard barrel connector -- it has a 4.5 mm outer diameter, and I think it is 2.7mm inner -- but it also has a pin running down the center! Is that still called a barrel connector?The male part on the power bank is hard to measure because I can't get the calipers in there for the inner diameter. Anyway I think the dimensions are :Power bank: 10mm L x 6.0 or 6.1 mm outer x ~ 2.1mm innerOn amazon, people say this adapter fits the power bank but there are no dimensionshttps://www.amazon.com/gp/product/B00LB4838AI looked on Digikey but couldn't find these sizes. Where else can I look?Any advice about this would be greatly appreciated.

author: boffin
author_rank: Unknown
timestamp: April 24, 2018, 09:11:14 pm
content: I have a cheap car -> laptop charger off ebay (wasn't more than 20) that has the step-up in it. You could just raid one of those for the circuit, likely a lot less bother than making your own boost converter

author: teridon
author_rank: Newbie
timestamp: April 24, 2018, 09:55:37 pm
content: That's a good point; I could buy a somewhat generic car adapter with 12v input and 19v output.However, none of the available adapter have the right barrel.I could buy another AC adapter to get the right barrel, but that's at least $33 just for the correct barrel! e.g.https://www.amazon.com/YEECHUN-Adapter-UX501VW-DS71T-UX501VW-US71T-UX501JW-DH71T-WX/dp/B072BQJBY7

author: KL27x
author_rank: Super Contributor
timestamp: April 25, 2018, 11:52:44 pm
content: Input current is 9A, max. Efficienty is 96% max.Assuming it can reach the max at the exact input/output you happen to want (buy a lottery ticket while you are at it), that gives you 5.45A output at 19V.I would personally be thrilled if I got 65% of that, sustained. About 3.5A. And I wouldn't take even odds it could do even that. Actually, looking at the board, I would bet the farm it can't. Those max ratings might even be peak/surge ratings.It's might be good enough, though. The power brick has to provide enough power to run the lappy AND charge the batteries at the same time, and the rating of the PSU doesn't tell you how much of that the laptop uses. It could peak at much less.

author: teridon
author_rank: Newbie
timestamp: May 01, 2018, 03:45:17 pm
content: Success! Though, I don't know how to measure the efficiency. [guidance appreciated here]I ended up buying 3 things (~ $55 total):https://smile.amazon.com/gp/product/B0043QYRP6( PWR+ 19V car charger ) (has the wrong barrel)https://smile.amazon.com/gp/product/B01BV29BHI(Weego 12V socket adapter)https://smile.amazon.com/gp/product/B074W43Q3G(Delippo AC adapter for the right barrel)I swapped the barrel from the AC adapter to the car adapter, and everything is hooked up and working. My laptop now charges directly from the power bank.Power bank 12v output -> Weego JSFSA 12V Socket Adaptor -> PWR+ car charger (with barrel from Delippo AC adapter) -> laptop.The barrel on the Delippo adapter is a little too long, so it sticks out from the laptop further than I would like, but it works.

author: ledtester
author_rank: Super Contributor
timestamp: May 02, 2018, 04:50:23 am
content: Quote from: teridon on May 01, 2018, 03:45:17 pmMeasuring efficiency requires four meters and some sort of load. You measure the power (volts x amps) coming out of your battery pack and also the power coming out of the converter into your load. The ratio of the converter power to the battery pack power is the efficiency (which will always be <= 1.)However, you might be more interested in run-time, which you can measure by just using your battery pack.QuoteFor the right barrel jack, if you can wait a while, just do an ebay search for "4.5 3.0mm" (i.e. the dimensions of your plug). Or search for "tip universal laptop" or something like "Female To DC Male Jack Plug For Laptop AC Power Connector Adapter".