Random toy USB charging question

[t6_tom]

Hi,

I have a limited understand of electricity and was wondering if someone could answer this.

I recently bought a radio control car of my boy, (had to get a second one for my 1 year old which I will look after till he is big enough to drive it...)

The charging setup is something I have never seen before.

It charges via usb, the instructions say that it should be charged at between 0.7a-2a (5v obvs) I was always under the impression that current is "pulled" from the power source so you can use a more powerful charger providing the voltage is correct?

Image of the battery is below, it has one wire for charging and one for providing power to the car

Here is the funny bit

• It charges at 5v , 0.7a-2a
• However the battery is 7.4v,1800mAh, 13.32wh
  • Switch on car 7.4v 45w

Is the reason for the 2a limit on the usb that the battery can draw much more than 2a at 5v, risking burning the usb charging cable?
If I used a 2 port charger which has a max output of 2.4a how close to danger am I getting?



Thanks in advance

 

[The Bear78]

That appears to be a Li-Po battery (lithium polymer)? If it is I would be cautious of trying to charge it without the correct charger. There are plenty of youtube clips showing their volatility if mishandled. They are easily ruined as well.
Ultimately Follow the instructions but most Li-Po's that I have come across have two plugs but the larger one is for both connecting to the machine (car, boat, drone etc) and for charging. The smaller is used for monitoring charging across the cell (or cells as applicable) by a dedicated charger.

Edit.
In fairness it should have three cables for 7.4v if it is a monitoring plug.

 

[The Bear78]

For example, I have a similar charger to this;


Which has the main charging points here as well as a selection of monitoring plug connectors depending on how many cells the batteries have ;

The white plug looks very much like one of these on the right.

 

[BikerPa]

A LiPo marked as 7.xV has 2 cells (Nominally 3.6v per cell) therefore will need a balance charger to make shure they charge 'evenly' hence the Molex type plug as well as the main power lead as @The Bear78 has already stated. this allows the charger to monitor each cell individually.

Multicell LiPo's require careful handling.
Have a look at this LiPo Do's & Dont's

Loads of good info/bed-time reading generally HERE

P.S. USB will be unable to supply any proper LiPo charger

 

[Eeyore.boater]

There are two 3.7 volt cells in the battery pack. Power is drawn from the pack (via the red/black lead) with the cells in series giving 7.4 volts; but are charged individually via the white connector.

 

[t6_tom]

Thanks for the quick responses.

I double checked the instructions and they definitely say it should only be charged with the supplied USB charger.

The battery type is just listed as lithium. Lol

The charging mode in the instructions is called USB balance charging cable which I think references the above responses.

This is a picture of the charger in action.

Point taken on the safety of the batteries I will only charge them when I'm present and keep them somewhere fire resistant.

Thanks

 

[t6_tom]

Sorry last one. How dodgy is it to use the correct charger but with a 2.4 amp rather than 2 amp supply?

 

[JOG]

It would help if you post a pic of the label on the charger?

 

[t6_tom]

Sorry!

 

[BikerPa]

Sorry last one. How dodgy is it to use the correct charger but with a 2.4 amp rather than 2 amp supply?

The supply current should not affect a 'proper' LiPo charger as the charger sets the output.

Or ideally you should by setting the current output yourself based on the battery you are charging.

The basic rule of thumb is charge at '1C' which for a 1800mAH pack would be 1.8A

Go above 1C charge rate & it has an effect on battery life long term. It charges faster mind, but you have to be more careful

 

[BikerPa]

Sorry!

View attachment 143611

If that charger only has the one plug connection to the LiPo battery (i.e. just the main power lead) it has no way to balance the 2 cells or monitor them.
Personally I wouldn't use it unless you buy a LiPo battery meter/balancer like this to check the cells are even balanced before you start charging it.

Overlander 8S Battery Capacity Meter

Battery Voltage Capacity Checker / Balance Discharger / Servo Tester from Overlander Compatible with 8S battery packs! ► Total pack voltage ► Total battery capacity (0-99%) ► Individual cell voltage (Lithium) ► Individual cell capacity (0-99%) (Lithium) ► Voltage difference between Lithium...

www.overlander.co.uk

 

[Dilbert]

Sorry!

View attachment 143611

I think you could be getting over complicated for a toy.

This charger appears to use a DC to DC upconverter so it can provide the 7.4V required from 5V for the 2 cell LiPo. It has 3 wires on the output that presumably connect to the 3 pole connector (white) on the battery.

OK, it is not a sophisticated professional charger, but it should provide correct cell balancing (2 cells, 3 wires) and, according to its spec, will be current limited to 2A to prevent overloading the 5V USB source.

You just need a USB charger rated at 2A or above. The charger will look after the rest.

 

[BikerPa]

I think you could be getting over complicated for a toy.

This charger appears to use a DC to DC upconverter so it can provide the 7.4V required from 5V for the 2 cell LiPo. It has 3 wires on the output that presumably connect to the 3 pole connector (white) on the battery.

OK, it is not a sophisticated professional charger, but it should provide correct cell balancing (2 cells, 3 wires) and, according to its spec, will be current limited to 2A to prevent overloading the 5V USB source.

You just need a USB charger rated at 2A or above. The charger will look after the rest.

Sadly the connection to the battery is not shown in the photo.
I’ve seen far too many dodgy cheap chargers for ‘toys’ that really are quite dangerous

 

[t6_tom]

 

[BikerPa]

View attachment 143635

Really need to see the plug/socket.
Is it connected to the white balance connector with the 3 fine wires or just the main power output lead with 2 thicker wires

If it’s connected to the white connector from the battery it is balancing so should be ok.
How well it is balancing though you can’t tell without a meter

 

[Dellmassive]

some good advice above . . .

I've got a few RC cars, (Lipo electric, Nitro & a 2stroke)

as above Lipo cells can be a bit iffy - - I've had one go up in flames after a crash.

they are also iffy when charging. . .


the normal RC battery chargers for (LIPO not NICAD) are these style . . . - https://amzn.to/3g6VEVc






and used with a fireproof charger bag. . . . - https://amzn.to/3KSX6bQ





....



But over the last few years I've noticed that smaller Amp USB chargers have started to apperar.

they obviously will only charge as fast as the PSU they connected to . . . and designed for the smaller style batterys . .


like this example:

Dilwe CX405 4CH Micro USB charger, 4 LEDs independent of 4 channels, for Mcpx / Molex / JST connector battery, for 1S 3.7V Lipo LiHV 3.8V battery for RC helicopters etc. : Amazon.co.uk: Toys & Games

Shop Dilwe CX405 4CH Micro USB charger, 4 LEDs independent of 4 channels, for Mcpx / Molex / JST connector battery, for 1S 3.7V Lipo LiHV 3.8V battery for RC helicopters etc.. Free delivery and returns on eligible orders of £20 or more.

amzn.to

and . . .

Yangers 2 Pack Li-ion rechargeable lipo battery 7.4V 1500mAh 2S 20C T plug female connector with USB charger for RC car off road truck jumper WLtoys : Amazon.co.uk: Toys & Games

Shop Yangers 2 Pack Li-ion rechargeable lipo battery 7.4V 1500mAh 2S 20C T plug female connector with USB charger for RC car off road truck jumper WLtoys. Free delivery and returns on eligible orders of £20 or more.

amzn.to

...

So follow the good advice above.

use the correct charger,

and don't leave them un attended when charging . .

store them safely when not in use . .


.

 

[Dellmassive]

FWIW . . .

heres a few pics of the RC kit . .

 

[t6_tom]

Hope this is better! Thanks for bearing with me.

So the charging element definitely has three wires.

We agree that the max input of 2a is a bit irrelevant because of the USB charger inline bit (not the wall socket) should be able to handle any normal USB current?

 

[t6_tom]

some good advice above . . .

I've got a few RC cars, (Lipo electric, Nitro & a 2stroke)

as above Lipo cells can be a bit iffy - - I've had one go up in flames after a crash.

they are also iffy when charging. . .


the normal RC battery chargers for (LIPO not NICAD) are these style . . . - https://amzn.to/3g6VEVc


View attachment 143712



and used with a fireproof charger bag. . . . - https://amzn.to/3KSX6bQ


View attachment 143713


....



But over the last few years I've noticed that smaller Amp USB chargers have started to apperar.

they obviously will only charge as fast as the PSU they connected to . . . and designed for the smaller style batterys . .


like this example:

Dilwe CX405 4CH Micro USB charger, 4 LEDs independent of 4 channels, for Mcpx / Molex / JST connector battery, for 1S 3.7V Lipo LiHV 3.8V battery for RC helicopters etc. : Amazon.co.uk: Toys & Games

Shop Dilwe CX405 4CH Micro USB charger, 4 LEDs independent of 4 channels, for Mcpx / Molex / JST connector battery, for 1S 3.7V Lipo LiHV 3.8V battery for RC helicopters etc.. Free delivery and returns on eligible orders of £20 or more.

amzn.to

View attachment 143714

and . . .

Yangers 2 Pack Li-ion rechargeable lipo battery 7.4V 1500mAh 2S 20C T plug female connector with USB charger for RC car off road truck jumper WLtoys : Amazon.co.uk: Toys & Games

Shop Yangers 2 Pack Li-ion rechargeable lipo battery 7.4V 1500mAh 2S 20C T plug female connector with USB charger for RC car off road truck jumper WLtoys. Free delivery and returns on eligible orders of £20 or more.

amzn.to

View attachment 143715




...

So follow the good advice above.

use the correct charger,

and don't leave them un attended when charging . .

store them safely when not in use . .


.

Thanks there is some great advice here especially the flameproof charging bag bit.


Might be a stupid question but what is the best method of storage. I understand it's really important to make sure the terminals can't touch anything metallic.

 

[Dilbert]

Hope this is better! Thanks for bearing with me.

So the charging element definitely has three wires.

We agree that the max input of 2a is a bit irrelevant because of the USB charger inline bit (not the wall socket) should be able to handle any normal USB current?

View attachment 143638

These USB chargers typically have a maximum charge on the output side to the battery of 1A at 7.4V. The 2A input is the maximum at 5A (lower voltage same power means more current + inverter losses).

The charger will pull a maximum of 2A from a USB charger. You should ensure the charger has an output rating of at least 2A otherwise the charger will restrict the charge.

A higher charger current rating does not mean you are putting too much in. The charger will draw what is required during the charge cycle but no more that 2A.