1
\$\begingroup\$

I am making a small project that has a li-ion battery for power. I need to be able to charge the battery within the circuit and am trying to find the correct amperage to charge it with. The battery is a 3200mAh li-ion cell (3.8V), and I am wondering what the maximum (safe) amperage is to charge the cell. I know (think) the optimal amperage to charge with would be 3.2A (1C), but is it safe to use 4A (1.25C) or even 5A (1.56C) without blowing anything up?

EDIT: I am using an Anker 3200mAh battery, but couldn't find a datasheet on their website (after a quick search). LINK

-Ben

\$\endgroup\$
  • 2
    \$\begingroup\$ What does the battery datasheet say? \$\endgroup\$ – Matt Young Oct 30 '16 at 3:46
  • 2
    \$\begingroup\$ Please edit your question to include the make and model of cell, and a link to a datasheet for it, if possible. If you don't have the make and model, then tell us where you got the cell and add a picture of it. \$\endgroup\$ – mkeith Oct 30 '16 at 3:46
  • \$\begingroup\$ Post edited with battery information. \$\endgroup\$ – Benjamin Owen Oct 30 '16 at 4:03
  • 2
    \$\begingroup\$ Given the lack of info, I think all one can surmise is that it is probably safe to charge in a Galaxy Note 3. Apart from that it is very hard to say. \$\endgroup\$ – mkeith Oct 30 '16 at 5:11
2
\$\begingroup\$

According to battery university the advised charge rate is between 0.5C and 1C, however certain batteries will happily charge at much higher rates. Either check the datasheet or (less reliable) check with the seller. From a little searching it seems the Galaxy Note 3 (the device that battery is designed for) charges at typically a current of approximately 1800mA.

However, bare in mind that charging cells at a higher rate generally reduces overall lifespan. If possible you're better off charging more slowly.

| improve this answer | |
\$\endgroup\$
  • \$\begingroup\$ If I were to charge at around 3A (1.9C), would I have to use a battery charger IC or can I just wire the 3A 5V directly to the battery? I would be using a USB Type-C charging block. Would this hurt the battery or would I still have to use a battery charger IC? \$\endgroup\$ – Benjamin Owen Oct 30 '16 at 15:25
  • \$\begingroup\$ @AngryCupcake Do NOT connect it to a 3A 5V supply. There's a strong chance that will start a nasty fire. Don't mess around with this battery at your experience level. Get yourself some 18650 cells with built-in protection circuits (they don't all have those, so check). They'll still have good performance and will be much more forgiving. \$\endgroup\$ – pericynthion Oct 30 '16 at 16:55
  • \$\begingroup\$ @pericynthion I meant to say 0.9C, if that changes anything. \$\endgroup\$ – Benjamin Owen Oct 30 '16 at 16:57
  • \$\begingroup\$ @AngryCupcake it doesn't, the 5V is the problem. \$\endgroup\$ – pericynthion Oct 30 '16 at 17:33
  • \$\begingroup\$ @pericynthion should I get a step down converter to take it down to 3.8V then? I have some 18650 batteries but I need the low profile of a cell phone battery. I assumed you could charge a 3.8V battery on 5V, but I may be wrong. \$\endgroup\$ – Benjamin Owen Oct 30 '16 at 17:36
1
\$\begingroup\$

It's entirely dependent on the battery and the thermal environment. 1C may be too much for some batteries (and for many, it's faster than is optimal for longevity). Others can take 5C or more.

Cellphone batteries are particularly specialized and although modern ones can charge quite quickly, they need active temperature monitoring to do so safely. Sadly, their datasheets are often not public.

| improve this answer | |
\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.