# Battery charging

#### anditechnovire

Joined Dec 24, 2019
105
Please I have some couple of 3.6v 3Ah cylindrical li-ion battery, but since I bought them, charging it became a huge problem. I first connected a single one to a 2A infinix phone charger (made in china. According to the ratings, it capable of adjusting output current and voltage to load)thinking that if it's capable of charging a 4Ah infinix phone battery then a 3Ah shouldn't be a problem.
Until I connected the battery directly to the charger output, after some time, i measured the output voltage of both the battery and the charger, the battery was not charging and the charger decreased it output voltage from 5v to 2v and was also giving me an unusual jolt in my finger. I concluded that the charger has damage. I tried it again with a similar charger, but this time a TECNO phone charger, but the same result.
I then found another SMPS charger 12v, 1.2A. In my desperation, I ignorantly implemented a '7805' regulator ic to drop the voltage to 5v(since using a smps to regulate a smps sounds absurd). When I connected the battery, I measured the charging current, and I was so surpries to see 2A.From a 1.2A(short circuit current) SMPS.
So please where did I went wrong and how can I charge my batteries before it damage.

#### Irving

Joined Jan 30, 2016
2,531
Are they Li-ion 4.2v charge, 3.7v nominal or LiFe 3.6v charge, 3.2v nominal? In any case charging above their specified charge voltage will damage them fairly quickly (in terms of reduced charge cycles).

They need to be charged at constant current of no more than typically half their C rating (e.g. 1.5A) until they reach their charge voltage and held at that voltage until the charge current drops to typically 1/100C (e.g. 30mA).

Phone chargers have no intelligence in them, that's all in the phone - that's why they didn't work. You either need a proper Li-Ion/LiFe charger or buy one of the many USB charger boards available from eBay/Amazon for a couple of $/£. You could build your own, but it's not really worth it as most of these chips are surface mounted and it'll end up costing a lot more. Thread Starter #### anditechnovire Joined Dec 24, 2019 105 hi You should use a TP4056 for li-ion charging. Look at this link. E https://www.amazon.co.uk/AZDelivery...68K89E40JSK&psc=1&refRID=0TP653TSN68K89E40JSK I really appreciate your help, but I don't think am in the right situation to actually purchase any online shipping product now. Not just now. The location I am right now, doing that will be a long protocol or I'll just have to wait after the pandamic which will go a long way in completely discharging my battery to death. I needed something more urgent.Any kind of a hack. Thread Starter #### anditechnovire Joined Dec 24, 2019 105 Are they Li-ion 4.2v charge, 3.7v nominal or LiFe 3.6v charge, 3.2v nominal? In any case charging above their specified charge voltage will damage them fairly quickly (in terms of reduced charge cycles). They need to be charged at constant current of no more than typically half their C rating (e.g. 1.5A) until they reach their charge voltage and held at that voltage until the charge current drops to typically 1/100C (e.g. 30mA). Phone chargers have no intelligence in them, that's all in the phone - that's why they didn't work. You either need a proper Li-Ion/LiFe charger or buy one of the many USB charger boards available from eBay/Amazon for a couple of$/£. You could build your own, but it's not really worth it as most of these chips are surface mounted and it'll end up costing a lot more.
But the charger I used produced 2A output current(don't know if it actually true) which is far higher than half the battery's current which was 3A. Why can't I charge it with ease.It seems the battery try to draw excess current than the charger can produce which was then responsible for reducing the output voltage to 2v, and even exhibiting magnetostriction on the charger, which I assume it because of the extra stress given by the load.

#### Irving

Joined Jan 30, 2016
2,531
The battery will pull as much current as it can, easily could pull 10A or more (I charge LiFe packs at 50A through a special charger). Your 'charger' is just a power supply, not a constant current output device, so it goes into shutdown when the battery tries to pull more than 2A.

Do you have MOSFETs, voltage regulators etc available to you? If so, what? I can probably cobble a temporary solution together for you.

#### anditechnovire

Joined Dec 24, 2019
105
The battery will pull as much current as it can, easily could pull 10A or more (I charge LiFe packs at 50A through a special charger). Your 'charger' is just a power supply, not a constant current output device, so it goes into shutdown when the battery tries to pull more than 2A.

Do you have MOSFETs, voltage regulators etc available to you? If so, what? I can probably cobble a temporary solution together for you.
Yes I have multiple power transistors, one Mosfet (I can look for more if the case may need), and some linear regulators. I as well have some inductors in case of smps (but I don't have low voltage smps ics. Just high voltage ones like viper22A Rm6203 etc).
But please let me know more about the concept of the amount of current drawn by load.
Example, if a 4Ah battery is charged by a mains operated power supply of 2A and a solar panel of 1A. The battery will quietly receive the 1A by the solar panel, but when it comes to the power supply circuit operated from the mains, it will not accept even when it almost produces half the battery's current. It will try to damage the power supply, but it will not draw more current other than what it given from the solar panel.

#### BobTPH

Joined Jun 5, 2013
4,748
Stop what you are doing right now!

A “phone charger” is NOT a lithium battery charger. The charger is in the phone and all the little charger block does is power it with a constant 5V. You are lucky that you have not started a fire. If your “charger” was capable of 10A, your battery would likely have exploded.

Buy a lithium ion battery charger designed for the cells you have.

Bob

#### Irving

Joined Jan 30, 2016
2,531
Yes I have multiple power transistors, one Mosfet (I can look for more if the case may need), and some linear regulators. I as well have some inductors in case of smps (but I don't have low voltage smps ics. Just high voltage ones like viper22A Rm6203 etc).
But please let me know more about the concept of the amount of current drawn by load.
Example, if a 4Ah battery is charged by a mains operated power supply of 2A and a solar panel of 1A. The battery will quietly receive the 1A by the solar panel, but when it comes to the power supply circuit operated from the mains, it will not accept even when it almost produces half the battery's current. It will try to damage the power supply, but it will not draw more current other than what it given from the solar panel.
Oh dear, where to start.....

OK, let me reiterate BobTPH's warning - do not ever connect a power supply to a Li-Ion battery. You were lucky the power supply couldn't cope. To the power supply the battery, while charging, looks like a dead short. Its only because the power supply was protecting itself that nothing untoward happened. High currents cause excessive heating and thermal runaway and fire. You can only use high currents if you monitor the battery temperature internally. Otherwise you keep charging currents to to less than 1/2 battery capacity.

Now, a solar panel is a different situation. Solar panels are inherently current limiting devices. You cannot draw more from the panel than it wants to give. So if your panel wont give more than an amp thats all the battery will get... and so it will happily charge away and the voltage from the panel will increase until the battery dies from over-voltage which 'poisons' it. Too much voltage damages the internal chemistry and severely limits its future capacity - and it will cause it to gas internally and swell which could make it explode. So when its charged to 4.2v and not 10mV more it must be disconnected from the source.

Ideally go buy a proper charger.

To be continued in a follow up post... going to eat now...

#### anditechnovire

Joined Dec 24, 2019
105
Stop what you are doing right now!

A “phone charger” is NOT a lithium battery charger. The charger is in the phone and all the little charger block does is power it with a constant 5V. You are lucky that you have not started a fire. If your “charger” was capable of 10A, your battery would likely have exploded.

Buy a lithium ion battery charger designed for the cells you have.

Bob
Thank you very much for your enlightenment. So another kind of circuit is inside the phone that actually charge the battery, having everything in control. Never knew that.
My problem is that, they don't sell li-on chargers around our environment, and this kinda lockdown will not permit me to get anything online.
So I wanted to find a way to modify or actually build that same internal circuit that a phone uses.
Will that still be ok.

#### Irving

Joined Jan 30, 2016
2,531
It will, and I have a solution for you, I just need to tweak it for what you have available.

What do you have of:
opamps?
LM317 or similar adjustable voltage reg?
npn power transistors good for >=1A?
multiturn pots?
low value resistors <= 1ohm?
9 - 12v power supply?

I assume you have a selection of common R and C values.

Do you have Arduinos? (another option)

Where are you?

#### anditechnovire

Joined Dec 24, 2019
105
It will, and I have a solution for you, I just need to tweak it for what you have available.

What do you have of:
opamps?
LM317 or similar adjustable voltage reg?
npn power transistors good for >=1A?
multiturn pots?
low value resistors <= 1ohm?
9 - 12v power supply?

I assume you have a selection of common R and C values.

Do you have Arduinos? (another option)

Where are you?
Yes I have all what you've listed. But like I said, am still kinda moderately knowledgeable in electronics, so I've not yet reached the stage of digital circuit (Arduino circuit), so that is the only exception.
For adjustable voltage regulator and opamp, I have 78xx, 5v, 8v, 9v. And tl431(voltage regulator and some sort of error amp),
LM324N(the datasheet says it an opamp, but I don't know if it only used for audio signals). Much many C and R.
In short I have multiple old SMPS circuit from different sources, laptop chargers, DVD players,adapters etc. So I have all the components associated with it.