# How can I get 12V 1A charging voltage from USB?

• karabiner98k
In summary, the powerbank is not powerful enough to provide the current required to charge the battery. The OP will have to find a way to step up the voltage or find a different powerbank.
karabiner98k
Hello everyone,
Recently, I bought a R/C Helicopter which has a 7.4V 850mAh Lipo battery.
I enjoy flying it in the field but I have a problem charging its batteries after each flight. I have no access to any car battery or 220V wall socket.

I bought a Lipo charger for it which needs at least 10V 800mA to charge the battery.

I have a 5000mAh powerbank. How can I get 10-12V from it to charge my batteries in the field?

Are you sure the powerbank is capable of delivering an almost 1 A current?

russ_watters
Sorry, I wasn't clear.

It is power that matters, so if it is a 5V powerbank, at 5V and 1.5 A it can deliver around 7.5 W, you need around 10V*800 mA = 8W. Can be not enough.

russ_watters and davenn
Borek said:
Sorry, I wasn't clear.

It is power that matters, so if it is a 5V powerbank, at 5V and 1.5 A it can deliver around 7.5 W, you need around 10V*800 mA = 8W. Can be not enough.
I need a solution to step-up my powerbank voltage and reduce its current.

karabiner98k said:
I need a solution to step-up my powerbank voltage and reduce its current.

I understand what you are looking for, but from what you wrote so far it is not clear whether the powerbank is powerful enough to deliver what you need. While to some extent you can use a switcher to convert between voltages and currents, there are physical limitations to how much can be done. One of them is that the power on output can't be higher than the input power (actually it is always lower).

davenn
So, you want to say I need powerbank with 5.0 2A (10W) to be able to get 10V 0.8A (8W) from it?

10 W sounds like a minimum. I would look for something even stronger.

davenn
Borek said:
Sorry, I wasn't clear.

It is power that matters, so if it is a 5V powerbank, at 5V and 1.5 A it can deliver around 7.5 W, you need around 10V*800 mA = 8W. Can be not enough.

Thanks Borek
and I wasn't thinking clearly whilst a thumping headache was in progress
I wasn't fully considering the power requirements

EDIT

the converters I linked to will do the job ... but it is still dependant on if the LiPO can handle the required current
The OP said the powerbank was a 5000mAh battery, so technically that's 1 Amp for 5 hrs or 5A for 1 hr
at the two extremes. So unless it has some current limiting device in it, it should be able to supply 2A or so for a couple of hours
karabiner98k said:
https://www.ebay.com.au/sch/i.html?_nkw=dc+dc+boost+converter

What is this? How can I connect my powerbank to it?

you are going to have to do some electronics construction to make up appropriate cables
If you are unable to do that, then you will have to find some one who lives near your to do it for you

You are highly unlikely to find something "off the shelf" that is plug and play
DIY construction will be a requirementDave

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davenn said:
The OP said the powerbank was a 5000mAh battery, so technically that's 1 Amp for 5 hrs or 5A for 1 hr
at the two extremes. So unless it has some current limiting device in it, it should be able to supply 2A or so for a couple of hours

There is another problem here as well. We still don't know what kind of powerbank OP uses, but they are typically built for powering small devices though USB plugs/cables. That's not a connection that was designed to sustain this kind of currents for long.

All RC people I know have either enough batteries to fly their models without charging them during a day, or they use car batteries as energy source. One guy even has a gasoline powered portable generator, but it was not bought for charging batteries but tools he uses in a field in his job. Still, he has enough power to share it with everyone on the airstrip

davenn
I suspect your power bank only had a USB port on it. I think that will limit the output current to something like 0.2A unless the boost converter talks nicely to it using the right usb protocol.

I think it might be easier to buy a 12V lead acid battery. Keep it on a float charger between flying sessions.

Asymptotic and sophiecentaur
CWatters said:
I suspect your power bank only had a USB port on it. I think that will limit the output current to something like 0.2A unless the boost converter talks nicely to it using the right usb protocol.

I think it might be easier to buy a 12V lead acid battery. Keep it on a float charger between flying sessions.
There are many people who need a portable 12V those things are available all over the place. A 14Ah lead acid battery will only cost around £30 (or less) and that should suit you. If you don't like making up connections and 'boxing things up', there are complete solutions available. (I haven't personally searched for them but my Astronomy group posts often discuss them.
If you are a flying enthusiast then why not look at Flying website forums and see what people do there? Starting from a 5V source is not really the best solution - although you already happen to have one.

donpacino
My helicopter is not a super big model and doesn't require a 6S 14.8V 5000mAh battery to run!

It requires a 2S 7.4V 850mAh which can be charged by stepping up the USB port of my powerbank.
It is not logical to buy a 12V lead acid battery to charge a 2S battery!

Someone told me to buy this:
https://www.ebay.com/i/352205262076?chn=ps&fl=a

He said I can connect my powerbank to it through Micro USB port (input) and regulates the voltage by turning that screw (It is a potentiometer).

Input = 2V-24V
Output = 5V-28V
Output Current = 2A (Max) - (1A Recommended)

What does it mean by 2A Max?
Can I reduce it to 1A?

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karabiner98k said:
My powerbank is capable of delivering 5V 1.5A current.
I need a 10-12V 0.8A for charging my battery.

It's not possible to convert 5V at 1.5A to 10V at 0.8A.

If the charger draws 0.8A at 10V from the dc-dc converter then the dc-dc converter will try and draw at least 1.6A from the 5V power bank. That assumes the dc-dc converter is 100% efficient which it won't be. If it's 80% efficient (?) Then it will try and draw 1.6A*100/80=2A. That's more than the maximum you say your power bank can deliver (1.5A).

I can't predict what the power bank will do. It might work. It might fail in a puff of smoke. It might switch itself off. It might work for awhile then fail.

CWatters said:
It's not possible to convert 5V at 1.5A to 10V at 0.8A.
I have another powerbank which has 5.0V 2A output ports. What about it? Can it do the job?

5V 2A = 10W
10V 0.8A = 8W

That's much more likely to work. I think the dc-dc converter might get warm/hot but they are cheap enough that you could get more than one and experiment.

The only thing I want to do is to make a 10V 0.8mA (or 0.7) adapter by using USB port.

Output Current = 2A (Max) - (1A Recommended)
What does it mean?

If the current is not adjustable how can I use 1A or 2A?

karabiner98k said:
What does it mean by 2A Max?
Can I reduce it to 1A?

It means your charger must not draw more than 2A from the dc-dc converter. You say it draws 0.8A so that should be ok.

You don't need to reduce the current. Just check your charger doesn't draw too much from the dc-dc converter.

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This is my charger:

Output = 800mA
Does it mean that it draws 800mA from my power source?

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karabiner98k said:
Does it mean that it draws 800mA from my power source?

No. It draws as much as it needs. Note it requires at least 10 V on the input side, not 5 V that you have in your powerbank.

karabiner98k said:
Output Current = 2A (Max) - (1A Recommended)
What does it mean?

If the current is not adjustable how can I use 1A or 2A?
Electrical devices draw whatever amperage they require. Power supplies provide whatever amperage is drawn or die trying, unless they have an amperage regulator, which USB power supplies do.

donpacino
karabiner98k said:
This is my charger:

Output = 800mA
Does it mean that it draws 800mA from my power source?
Either that's a typo/bad English confusing ma for mah or it's just what type of battery it is designed for and has no relation to actual output amperage.

There is a decent chance the USB+ converter won't even run it, but even if it does it will take a long time to charge(at least an hour)...

...speaking of which, how long does it usually take?

russ_watters said:
...speaking of which, how long does it usually take?

Standard when charging LiPos is to use "1C" current - "C" meaning same current as the capacity of the battery (so if it is a 2200 mAh battery, you will charge it with 2.2 A),

russ_watters
Borek said:
No. It draws as much as it needs. Note it requires at least 10 V on the input side, not 5 V that you have in your powerbank.
That's why I want to buy this:
russ_watters said:
Either that's a typo/bad English confusing ma for mah or it's just what type of battery it is designed for and has no relation to actual output amperage.

Yes, that's a typo or bad English! Chinese!
It means Output Charging Current = 800mA (0.8A)

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karabiner98k said:
This is my charger:

Output = 800mA
Does it mean that it draws 800mA from my power source?
No it means it delivers 800mA (0.8A) to the cells being charged.

Data here

http://www.alsrobot.com/index.php?route=product/product&product_id=797

says the input current could be as high as 1000mA (1A) which is more than the 0.8A I've used in previous calculations. I don't think even your 2A power bank will work.

Still think a small 12V battery is a better bet.

karabiner98k said:
That's why I want to buy this:

Yep. Brain fart.

karabiner98k said:
It is not logical to buy a 12V lead acid battery to charge a 2S battery!
12V batteries are available in all sorts of capacities. A Voltage converter from your existing USB Power block is, in my opinion, no more logical. How many times do you need to recharge your helicopter battery 'in the field' per day? A (cheap) 5000mAh 12 volt battery will give you around twice as many charges as your 5000mAh power bank.
Only if you are doing this on a shoestring would the DC voltage converter solution be worth doing.
The current capacity of your 5V wires could also be an issue, as was mentioned previously and could result in a significantly longer recharge time than charging from 12V with lower current drain. But that would depend on how you actually plan to your flight programme. How long can you fly on one charge?
Can you swap lipo batteries conveniently, to give less delay?

-

Do you fly a lot ? If so i'd try one of these. Cant beat the price.

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sophiecentaur
sophiecentaur said:
12V batteries are available in all sorts of capacities.
They are certainly much more expensive. Could you please show me the picture of one of them?

The original factory charger charges my battery in 1 hour 15 mins (wall socket adapter), so I have no problem if charging the battery with the converter takes an hour or so.
1 hour delay between flights is good for the helicopter too because the motors have time to cool down.

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karabiner98k said:
1 hour delay between flights is good for the helicopter too because the motors have time to cool down.

You've made that up, haven't you? No need to wait that long, several minutes that you will spend just replacing the battery with a spare is perfectly enough. Make it 15 if you want to be super cautious.

Heat is usually not a problem with motors, but with regulators (ESC, Electronic Speed Controller, thing that runs the motor, in your model probably combined with UBEC - Ultimate Battery Eliminator Circuit - as that is the cheapest option these days). I have seen several models bursting in flames - it was always regulator that was source of problems. Motors reach their maximum temperature in several minutes and they don't get any hotter then, they are often designed in such a way they force air flow just by working. ESC/UBEC are more problematic, as unless they are by design placed in a position with a forced air flow they get hotter and hotter all the time.

To paraphrase an old saying: you are looking for a solution that is cheap, working and reliable - but you can pick only two at the same time.

sophiecentaur
karabiner98k said:
They are certainly much more expensive. Could you please show me the picture of one of them?

The original factory charger charges my battery in 1 hour 15 mins (wall socket adapter), so I have no problem if charging the battery with the converter takes an hour or so.
1 hour delay between flights is good for the helicopter too because the motors have time to cool down.
Look on eBay for lead acid battery and you will find many 12V examples. I saw a Yusa 12V 7Ah at £14.69. Search yourself and find what's available in your area. A charger (motorcycle application) can be obtained for about the same cost. Buy some thicker wires than you initially think you need and you are in business.
If I were out in the field, I would find waiting one whole hour for my next flight could be a real pain in the butt at times. The problem is that the 'USB' power source is not really 'Universal' as its name suggests. There's often a mismatch between the requirements and the capabilities although, give them credit, they do allow many peripherals to work seamlessly. But a model helicopter is in no way a Computer Peripheral and something has to suffer if it's treated as one.
I do sympathise if you are finding this all more expensive than you planned. Your solution to this may well be a bit of cheap DIY but you run the risk of needing to do it all 'properly' later on and finding you need to spend even more money. What if you decide to get a bigger and better aircraft, for instance. In that case your present marginal solution could be inadequate,

sophiecentaur said:
If I were out in the field, I would find waiting one whole hour for my next flight could be a real pain in the butt at times.
It's not a problem because I have two other helicopters to fly in the mean time.

Well, for three drones: maybe first you should sum up all the Ah you wanna' burn in a day and check if your powerbanks meets the demand?
I think it would answer some questions you forgot to ask so far...

Borek and sophiecentaur

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