# 3V to 20V DC - DC boost converter help

I am sorry if this question has been asked before, I couldn't find exactly what I'm looking for.

TL, DR: I'm looking for a way to boost 3V to 20V that:

• Works from a single cell lithium ion battery
• Is lightweight (UAV application)
• Can power a 45W load at 20V
• Is not super expensive
• Doesn't require buying additional batteries
• Doesn't consume power directly from the drone's flight battery

The long explanation: I have a specific piece of equipment that needs to be carried on a drone and is powered by 20V at something like 2.2A. I couldn't figure out a way to achieve that without a boost converter or a 6 cell lithium battery. The thing is, I have a lot of 6 cell, 5000mAh LiPo battery packs laying around, but they are prohibitively heavy (around 900g) and since each flight only lasts for around 10 minutes, I don't need that much energy storage. So, I thought it would be a good idea to disassemble the packs and use a single cell for each flight, which would give me 3.7V, 5000mAh while only weighing 1/6 of the whole pack. Then I bought a cheap 3-35V 80W boost converter, only to find out that it could deliver a maximum of 7W in this scenario, turns out the "80W" rating is assuming an input voltage of 20V and an output of 24V, which is not what I want. I have considered buying smaller lithium cells and building my own 6 cell pack, but that would get expensive really fast, and would also mean I can't use the batteries I already have. So, I would like to ask if there is another way to accomplish what I trying to, given all those restrictions.

• 3V in to 20V out at 2.2A should yield a peak of 17.47A in the inductor. I would probably go dual-phase (LTC3897-2) for the battery's sake. But I wouldn't expect your single battery cells to like >17A draw, or to last 10min (but I've no idea what you have). – Zekhariah May 10 at 14:05
• @Zekhariah: LiPo batteries for model aviation use are available for loads of up to 40 * (capacity/hours). He's going to be running at something like 4 * (capacity/hours), so he's fine in that regard. – TimWescott May 10 at 14:32
• The answer is yes, but you may have to design & build your own boost converter. That's not a trivial job, and it'll be heavy -- and the lighter you make it, the less trivial the design job will be. – TimWescott May 10 at 14:38
• Zekhariah, I'm sorry, I forgot to specify the battery. As @TimWescott pointed out, it is rated at 20C, and thus should be able to handle 100A peak. Running at 4C should give me around 15 minutes, with enough margin for converter losses. I know it is not a trivial job, especially for someone with so little background in the subject like me, but if I were to pursue that route, where should I start researching? Is there a boost converter design guide book or something? – caiotbc May 10 at 16:18
• You may want to look at the smps reference at schmidt-walter-schaltnetzteile.de/smps_e/smps_e.html – scorpdaddy May 10 at 16:30