Doubt about Li-Ion Batteries

Thread Starter

HRN88

Joined Jul 21, 2020
24
Hi buddies, I need help understanding some basic concepts about Li-Ion batteries.
I´ve been reading about this because I need to connect 2 single cells in parallel.

I understand the folloging:
  1. Li-Ion/Polymer batteries needs a special circuit to protect them from overvoltage (when charger), undervoltage (when discharge) and short circuit current. For example this I.C DW01A perform this task (only can protect a single cell... this IC doesn't protect a cell battery)
  2. We can charge a single cell for example with this guy MC34673 and this chip only charge a single cell and doesn't protect the battery.
  3. So I can derive that for a battery powered system (single cell) I need a battery protected and a battery charger IC.

And if I connect for example two or more cells in parallel.
1. In parallel, rated voltage is the same but the current capacity is increased so, can I use the MC34673 that is for a single cell?
2. Can I connect in parallel two single cells protected with the DW01A, and then to the charger MC34673?

And what about in series
3. Can I connect in series single protected cells with the DW01A and then to a charger? in this case using this guy LT3652

Ty :)
 

dl324

Joined Mar 30, 2015
14,897
Charging batteries in series requires circuitry to measure the voltage of each cell as it's charging. Charging batteries in parallel won't work because you need to measure the voltage of each battery independently.

https://www.batteryuniversity.com has a wealth of information on batteries.
 

KeithWalker

Joined Jul 10, 2017
2,453
Hi buddies, I need help understanding some basic concepts about Li-Ion batteries.
I´ve been reading about this because I need to connect 2 single cells in parallel.

I understand the folloging:
  1. Li-Ion/Polymer batteries needs a special circuit to protect them from overvoltage (when charger), undervoltage (when discharge) and short circuit current. For example this I.C DW01A perform this task (only can protect a single cell... this IC doesn't protect a cell battery)
  2. We can charge a single cell for example with this guy MC34673 and this chip only charge a single cell and doesn't protect the battery.
  3. So I can derive that for a battery powered system (single cell) I need a battery protected and a battery charger IC.

And if I connect for example two or more cells in parallel.
1. In parallel, rated voltage is the same but the current capacity is increased so, can I use the MC34673 that is for a single cell?

ANSWER TO #1
Yes, you can charge two cells in parallel with a single MC34673. The maximum charge rate is set by a resistor value. The maximum charge current is 1,2A,.

2. Can I connect in parallel two single cells protected with the DW01A , and then to the charger MC34673?

ANSWER TO #2
Yes, you could but it would depend on the application. The charger (MC34673) protects against over voltage. Usually a converter is used after the battery to obtain the correct voltage for the circuit being driven. This will contain over current and under voltage cut off so a DW01A would only be required.if no converter is used.

And what about in series
3. Can I connect in series single protected cells with the DW01A and then to a charger? in this case using this guy LT3652

ANSWER TO #3
You could but it would be better to use a protection device for two cells. It would probably not be required, as in the answer to question 2.

Ty :)
 
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