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Topic: 2s charger with load support? (Read 277 times) previous topic - next topic


Aug 27, 2018, 01:46 am Last Edit: Aug 27, 2018, 02:58 am by Graylord
Hey, so I am looking to charge myself some 18650 Li-ion cells hooked up in 2s2p, but have it also support output to the device the batteries are powering, preferably with open terminals I can do as I please with, not usb.

I found these TO4056 modules wich are the perfect example of what I'm looking for. However, they only support a single cell setup. (I also read that some newer editions support simultaneous load and charging, while older versions disconnect load when charging, but these eBay ads are so vague, how do I tell them apart?)

I've tried finding a 2s supporting equivalent, b
But so far none of the ones I've found have output for loads and can only charge.

Do you know of any similar chargers that support 2s?

Alternatively, I have 2S BMS circuits, both as a separate board and a 2S2P holder with it built in, but do these typically have balancing circuitry built in, or is it just over/under charging? Seeing as the main gripe I've found for other people trying using the TO4056 in a 2s setup is the need for a separate ground lead and balancing, would a 2s BMS potentially solve this or will it conflict with the TP4056's existing protection?

If that would work, 500mA per series is going to be a bit slow, but livable. But if there's an equivalent circuit board with higher Amp support, that would be neat!


You wont find a charger that can do what you want, as its difficult to do and theres not much need.
Do you have to use the cells in series?
Can you parallel all the cells and use a boost converter to get the voltage you need.
Thats how most of the power banks work.


Aug 27, 2018, 10:58 am Last Edit: Aug 27, 2018, 11:19 pm by Graylord
I suppose I could, but it depends on whether or not a booster would be very current limiting. The most common ones I'm seeing are 2A. That's less than what I already have. Is there any reason to not use multiple step up modules in parallel (with added current mirroring) other than increased footprint?

You see, the reason I want to do this isn't just to increase capacity, but the maximum amp output, as I have a lot of motors, and teetering towards brownouts when they all run at once.

And are voltage boosters energy efficient? In my current setup I have very little wasted power due to my switching voltage regulator setup, and it would be nice to keep it that way.


Sep 13, 2018, 11:01 pm Last Edit: Sep 13, 2018, 11:07 pm by Graylord
Alright! So I finally got myself a nice high amp buck step up converter, and a 4p battery case.

But now I need a suitable charger. When looking for info on various TP4056 modules, I can't find any info on how many Amps they can handle through the ouput to load. If I am going to provide power to motors from 4p 18650s there might be rather large start-up spikes.

Should these modules still do? Or do you have other suggestions.


Sep 14, 2018, 01:37 am Last Edit: Sep 14, 2018, 01:40 am by jremington
I can't find any info on how many Amps they can handle through the ouput to load
The chip data sheet is your best source of information, and the value is clearly stated (1.2A).

Those ICs are intended for charging only.


Sep 14, 2018, 02:06 pm Last Edit: Sep 14, 2018, 02:08 pm by Graylord
That's why I'm referring to modules such as these, which have added a load output, I realize the chips themselves don't have this, so it's a feature added to the modules. But I can't find any information if they are suitable or not.

If they aren't, do you know of any chargers with output to load that would be?


Please tell us about your project, rather than about your idea of a fix to some problem.

What do you want the battery to power, at what voltage and current?


Sep 14, 2018, 09:34 pm Last Edit: Sep 14, 2018, 09:40 pm by Graylord
It's just a learn-as-I-go automated robot.
My plan is to have it run around looking for sunlight, and charge itself from said sunlight.

It currently has 2s 18650 cells at 8.4v powering dc motors, and a 5v regulated power supply for the logic and sensor circuitry. The current depends enterily on what I make it do and is very variable, and I will probably have it do more stuff in the future, so any additional wiggle room is good to have. Currently I would estimate it runs maximally at around 4Amps (with large margins) when all 4 motors are running at max speed.

I wish to charge the batteries as well as increase the runtime.



Sep 15, 2018, 08:55 am Last Edit: Sep 15, 2018, 09:01 am by Graylord
I see, but they have to be disconnected while charging, correct?
I'm hoping to charge while powering a load.
It doesn't have to be a premade setup, I can built it myself if I get pointed in the right direction.

Alternatively I can make a setup where the bot gets disconnected when charging and a charging circuit gets enabled, but then I still need a low-power system to keep an eye on how long it's been charging and switch back to the bot after awhile, needing it's own power source.

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