Hi guys,

I've got some INR batteries here and i would like to charge them with with a generator. The question is: What kind of voltage do i need to charge it up? AC? DC? or a pulse? And what's the best way to make it efficient? The generator's voltage varies, so the current will never be constant. WIll that also be a big problem?

I've got a buck-boost converter to make the voltage into 4.2V to charge it up. I choosed 4.2V, because the voltage of the INR battery varies between 2.5V and 4.2V. The generator doesn't generate much power, so I don't have to worry about the current.

The INR battery specs:
Voltage: 3,7V
Max discharge current: 15A
Capacity: 3000mAh
Brand: Samsung

 

Li-ion batteries explode or catch fire if mistreated. So there must be some circuit to control the charge and discharge.

 

Have a read of this, then buy either a control IC specially intended for lithium battery management, or a ready-made dedicated charger.

 

I've got my own protection design. I only wanted to know what kind of voltage i needed and if it's smart to use a changeable current. What would happen if the current varies between 0.1C-1C? Looking at the link I've read that it's adviced to charge the battery with 0.5C-1.0C. I don't see anything about AC and DC voltages, so i assume I only need DC voltage?

 

I've got my own protection design. I only wanted to know what kind of voltage i needed and if it's smart to use a changeable current. What would happen if the current varies between 0.1C-1C? Looking at the link I've read that it's adviced to charge the battery with 0.5C-1.0C. I don't see anything about AC and DC voltages, so i assume I only need DC voltage?

Well I've never seen an AC battery!

 

Well I've never seen an AC battery!

https://www.cclcomponents.com/enphase-energy-storage-system-2x-1-2kw-ac-battery

 

I've got my own protection design. I only wanted to know what kind of voltage i needed and if it's smart to use a changeable current. What would happen if the current varies between 0.1C-1C? Looking at the link I've read that it's adviced to charge the battery with 0.5C-1.0C. I don't see anything about AC and DC voltages, so i assume I only need DC voltage?

Why do you think your own design is better than the recomended charger?
From your questions, it looks to me that you don't have the expertize to roll your own design. It would go a lot better if you would take the advice given and not just do it your way. Or maybe you really want to destroy batteries and maybe start a fire or injure someone with exploding batteries.

 

Could you upload your protection circuit?
So many helpers here that they can do some more help to check or improve your own design for you and that is better than just by your own.

 

I've got my own protection design. I only wanted to know what kind of voltage i needed and if it's smart to use a changeable current. What would happen if the current varies between 0.1C-1C? Looking at the link I've read that it's adviced to charge the battery with 0.5C-1.0C. I don't see anything about AC and DC voltages, so i assume I only need DC voltage?

Asking whether AC or DC tells me all the Darwin award needs is a signature!

other's have suggested you do a bit of reading - I think you should too.

 

I have to design a big system for my internship. And a part of that is charging the batteries with a generator. I'm using the atmega328p to control the other circuits of my system and I will also use it to measure the voltage of each battery. I've got a power mosfet connected to the battery as a safety switch. I've designed my own current limiter and if the output current goes above 2A the mosfet switch will be turned off, so there won't be any current. The mosfet switch will also be used whenever each battery decreases below 3,1V or gets above 4,0V. I got this protection, because the INR batteries doesn't contain protection circuits in the packet. INR batteries are supposed to be a lot safer than ICR batteries.

Most battery protection circuits cuts the connection if the battery gets below 2,5V or above 4,2V. So I've choosen 3,1V and 4,0V as limit, it's also better for my other circuits.

Based on the charging information, I know the battery needs to be charged with 0.1C when the voltage is between 2,5V and 3V, 0.5C-C between 3V and 4,2V.

The charging system exists of a buck-boost converter, which makes the output 8,4V (two batteries in series) if the generator generates at least 6V.

I hope this explanation is better.
So yeah, basicly my question has been answered, but I've got another question..

How do adapters with a current limiter work?
I've got a current limiter circuit with a mosfet and if the current that flows through it is above 2A, the voltage will decrease which means the current will be limited at 2A. Do the adapters work like this as well? Or are there systems where u can limit the current at 2A and keep the voltage stable.

 

Or are there systems where u can limit the current at 2A and keep the voltage stable.

Oh yeah, you just adjust the resistance of the load.

 

Oh yeah, you just adjust the resistance of the load.

The battery is the LOAD in this case.
I want to charge it with 8,4V and 2A max.
I don't think i can change the resistance of the load this way.

 

The battery is the LOAD in this case.
I want to charge it with 8,4V and 2A max.
I don't think i can change the resistance of the load this way.

Exactly. The relationship between the current and voltage is determined by the battery not the charger.

The charger can apply a constant voltage to the battery and the battery will decide how much current it draws or the charger can supply a constant current to the battery and the battery will determine the voltage.

 

Thanks for the reply. How am i supposed to change the resistance of the battery or load? I've thought about this before but didn't know how to do it.

The resistance of my INR battery is 50m ohms. If I charge that battery up with a voltage of 8.4V a huge amount of current will flow to it.

 

Did you read through the link given in post #3?

 

Thanks for the reply. How am i supposed to change the resistance of the battery or load? I've thought about this before but didn't know how to do it.

You change the "resistance" in the charging circuit.

The resistance of my INR battery is 50m ohms. If I charge that battery up with a voltage of 8.4V a huge amount of current will flow to it.

True.
That's why you add a current-limit circuit.
You design the circuit so the battery charges at the desired constant-current until it reaches the maximum voltage and then it changes to a constant-voltage charge (or you stop the charge).

 

You design the circuit so the battery charges at the desired constant-current until it reaches the maximum voltage and then it changes to a constant-voltage charge (or you stop the charge).

You design the circuit so the battery charges at the desired constant-current until it reaches the maximum voltage and then it changes to a constant-voltage charge and the current begins to fall. When the current has fallen to a low value you stop the charge.

 

Well I've never seen an AC battery!

I have, you can buy them here lol


Car, Boat, Motorcycle, and RV Batteries | ACDelco

 

Thanks for the reply. How am i supposed to change the resistance of the battery or load? I've thought about this before but didn't know how to do it.

The resistance of my INR battery is 50m ohms. If I charge that battery up with a voltage of 8.4V a huge amount of current will flow to it.

You don't change the resistance of the battery, you use a deadicated charging chip, this does all the work for you.

https://www.digikey.co.uk/en/articl...igner-guide-fast-lithium-ion-battery-charging

If you're going to re-design the charging method, then buy yourself a fire extinguisher! !

 

If you're going to re-design the charging method, then buy yourself a fire extinguisher! !

And some safety goggles.
Even the professionals get it wrong sometimes. Can you do better than them?
http://abc7news.com/travel/battery-fire-on-plane-points-to-danger-in-the-sky/3020423/
https://www.cbsnews.com/news/lithium-battery-fire-risk-samsung-galaxy-note-7/
e.t.c.