DIY power bank

jordan_murp

Hey, just wondering could anyone on her help me

I recently purchased a power bank from penneys for €10 and when I opened it, it's a simple circuit using and recharging a 18650 4000mAh 3.7v battery.

I have 4 other 18650 batteries and was wondering could I use the original circuit to use all 5 or would I need a step down module.

also, would the batteries have to be wired in series or parallel.

cheers,
Jordan

Johnboy1951

For the same voltage in parallel; if you want a higher voltage then a series arrangement or a combination of series and parallel.

It is likely (IMO) that the charging circuit will not be able to handle extra batteries.

You would need a charging circuit capable of handling the extra current needed to charge multiple batteries.

jordan_murp

Johnboy1951 wrote: »

For the same voltage in parallel; if you want a higher voltage then a series arrangement or a combination of series and parallel.

It is likely (IMO) that the charging circuit will not be able to handle extra batteries.

You would need a charging circuit capable of handling the extra current needed to charge multiple batteries.

if I wired them all in parallel would the charging circuit be able to handle them?? cheers

brightspark

jordan_murp wrote: »

if I wired them all in parallel would the charging circuit be able to handle them?? cheers

No way of knowing without having access to the design specs of the charger.

Pleas be careful, what you are doing is potentially a serious fire risk due to the nature of the cells involved.

Johnboy1951

jordan_murp wrote: »

if I wired them all in parallel would the charging circuit be able to handle them?? cheers

Already answered!

It is likely (IMO) that the charging circuit will not be able to handle extra batteries.

jordan_murp

would this circuit work??
the charging circuit has an LED indicator for charging progress so I'd know when one is done and flick to charge the next and so on, and the same with using the USB output, when one battery is dead, flip to the next. I could try find a guitar 5 way switch or just make my own with 2 3 way switches. any ideas??

simple sketch of circuit www [DOT] imgur [DOT] com [SLASH] LwgLYRF

cheers

Johnboy1951

If you are considering that then I suggest you make sure you use a 'break before make' switch and suppress switching spikes.

I'm not sure how you would propose to use the device then ....... one battery at a time?

How about upgrading the charger/circuit to suit what you want? ..... ability to charge and use batteries in parallel ...

jordan_murp

last post and then I'm finished lol

So I can use a DIP switch to select which battery goes through the circuit one at a time (would suit me better and would be able to charge one at a time with the LED indicator)

I would write it like this www [dot] imgur [dot] com [slash] eciJntT yes??

Johnboy1951

That should work .... but would need to be careful that only one switch was made at any time.

BTW I would have the -Ve as common rail and put +Ve through the switches ....... just a personal preference.

jordan_murp

Johnboy1951 wrote: »

That should work .... but would need to be careful that only one switch was made at any time.

BTW I would have the -Ve as common rail and put +Ve through the switches ....... just a personal preference.

Great! yeah I'll be cautious about that. I'll probably end up doing the -Ve as common and route the +Ve through the DIP

cheers for all your help John

brightspark

Have you compared the current rating of the switch to the current flow when charging?

All 18650 cells need temperature sensors.

I prefer big batteries personally rather than batteries that charge batteries...lossy.

As an aside 4000mAh = 4Ah. The portable device market have adopted mA ratings to make their products sound impressive.