Battery Charging

[oceanblue]

Hi! I've been working on a project and I need it to be portable.

So I have two batteries of PKCELL LP785060 it's a 3.7V 2500mAh battery.
I connected the two in series which gives me a 7.4V battery.

My question is, can I use the adafruit powerboost 1000C to charge these batteries connected in series?

Should I modify something or do something before using the powerboost 1000C? or it'll be just fine if I connected it directly on the powerboost to charge the two?

here are the links for the components:

Battery: https://www.adafruit.com/product/328
Powerboost 1000C: https://www.adafruit.com/product/2190

Thank you!​

 

[dknguyen]

No, Lithium polymer cells require special charging algorithms or else damage and fire ensue.

 

[oceanblue]

No, Lithium polymer cells require special charging algorithms or else damage and fire ensue.

Thank you for the reply. May I ask if you can help me to find a way to charge these batteries?

 

[dknguyen]

Hmmm. Seems like a 2 cell Lithium charging board is difficult to find. That's what you need. Plenty of 1 cell boards, but not two cell.

 

[rjenkinsgb]

You need either a dedicated "balance charger" or a two cell charger plus a "balance and protection" board.

When charging lithium cells in series, a balance system is vital to ensure no one cell can exceed 4.2V if any other cell is still under that and charging.
A protection unit limits the minimum and maximum overall battery voltage to prevent harm due to voltage extremes.

Look at the red PCB in this listing - it combines charge, balance and protection. Several places look to be selling identical units.
**broken link removed**

You can also get "Balance chargers" to use with any battery pack - you just add a balance charge cable to each pack then use any on the same charger, rather than fitting a balance board to each battery. A protection board is still worthwhile to prevent over discharge, which can damage the cells.

Examples:
https://www.ebay.co.uk/itm/New-IMAX...-Balance-Compact-Charger-UK-Plug/183197819322
**broken link removed**

Balance charge cables to add to battery packs are readily available and cheap, eg.
**broken link removed**

I use one of those Turnigy chargers for many different battery packs.

 

[oceanblue]

You need either a dedicated "balance charger" or a two cell charger plus a "balance and protection" board.

When charging lithium cells in series, a balance system is vital to ensure no one cell can exceed 4.2V if any other cell is still under that and charging.
A protection unit limits the minimum and maximum overall battery voltage to prevent harm due to voltage extremes.

Look at the red PCB in this listing - it combines charge, balance and protection. Several places look to be selling identical units.
**broken link removed**

You can also get "Balance chargers" to use with any battery pack - you just add a balance charge cable to each pack then use any on the same charger, rather than fitting a balance board to each battery. A protection board is still worthwhile to prevent over discharge, which can damage the cells.

Examples:
https://www.ebay.co.uk/itm/New-IMAX...-Balance-Compact-Charger-UK-Plug/183197819322
**broken link removed**

Balance charge cables to add to battery packs are readily available and cheap, eg.
**broken link removed**

I use one of those Turnigy chargers for many different battery packs.

Hi sir. Thank you for this reply, it's very informative.
However, I'm having trouble connecting all the required components.
Could you possibly help me?

2x 3.7v 2500mAh batteries connected in series which will result to two polarities, positive and negative.
If I have a protection board it will still result into two polarities positive and negative.

Then, I can use a 7.4v 2s balancing charger.. however this chargers have a female 3pin JST cables. But I only have two polarities..
how do I connect these?

Thank you!

 

[Nigel Goodwin]

You have three connections, positive, middle, and negative - the whole point of balancing is that it has to connect across every single battery. If you have three batteries in series, then you four wires and so on.

 

[audioguru]

You have selected two Li-PO batteries to produce 7.4V. But they discharge to only 6V when they MUST have a circuit to disconnect them, and they will produce 8.4V when they are fully charged by a charger designed for charging Lithium batteries.

 

[schmitt trigger]

From the EBay description:

The latest version of the improved features:
1. The use of plastic irrigation package inductance, low voltage battery charging no high-frequency noise;

What is a plastic irrigation package inductance? Google translate does not translate from Chinglish.

 

[audioguru]

The ebay seller thinks it is important for him to pee on the batteries that he sells to irrigate them, because he knows nothing about them. Maybe many people pee on them in the dumpster where he found the thrown away batteries.

 

[NsrMagazin]

What you need is this:

IC.
Datasheet.

There are also boards for 2 batteries.