I want to charge Li-Ion battery 3Wh using a supercapacitors bank (6 in series and then connected in parallel, total 12 caps, Maxwell 2.7V 310F). First, I charge supercapacitors bank and then it charges battery. Problem is that the charging time is extremely limited, only few seconds. Battery is used for IoT device and cannot be removed or replaced. Device will be installed in isolated area, no power supply accessible, only quick charging few times a year (The device will be mostly in sleeping mode). If the voltage is limited should I use a huge charging current instead?

I would like to hear any idea. Also would like to know, which balancing is most suitable for that.

At the current stage, you can consider any power source you want.

 

Welcome to AAC!

What you propose isn't advisable. Battery shouldn't be charged at greater than 1C or overcharged.

Read this http://batteryuniversity.com/learn/article/charging_lithium_ion_batteries

 

Thank you for replying and sorry if my question was not clear enough, but I meant charging of supercapacitors with big current.

 

You mentioned charging a battery 3 times...

Depending on the battery, you might get a 10C discharge rate. Use current limiting to protect batteries.

 

I want to charge Li-Ion battery 3Wh using a supercapacitors bank (6 in series and then connected in parallel, total 12 caps, Maxwell 2.7V 310F). First, I charge supercapacitors bank and then it charges battery. Problem is that the charging time is extremely limited, only few seconds. Battery is used for IoT device and cannot be removed or replaced. Device will be installed in isolated area, no power supply accessible, only quick charging few times a year (The device will be mostly in sleeping mode). If the voltage is limited should I use a huge charging current instead?

I would like to hear any idea. Also would like to know, which balancing is most suitable for that.

Will the capacitors hold a meaningful charge compared to the battery? What would be the battery capacity rated in Farads? Will the capacitors hold a charge for a long time?













At the current stage, you can consider any power source you want.

 

I am thinking now of using string of 10 ultracaps connected in series 500F each, so it will be supecapacitors bank 50F with 27V and Energy stored E=50*25*25/(2*3600) = 4.3 Wh, so it is able to cover all the losses during energy transfering from ultracaps bank to battery (incl buck/boost DC/DC convertor). Supercapacitors bank will be discharging immediately after charging process is done (as soon as external power source is removed-> the relay closes the circuit).
I also came up with idea, that I can charge supercapacitors only to 80% instead of 100%, and it will be 2-3 times faster, that is why I want to increase total capacitance.
So far as the charge will not be kept for a long time in capacitors, which method of charging balancing will be most appropriate?
Is it possible to charge caps with the current that only their internal resistance allows? or I need to put additional resistors anyway?
Thank you, would be happy to discuss.

 

... so it is able to cover all the losses during energy transfering from ultracaps bank to battery (incl buck/boost DC/DC convertor).

I'm sorry, I mist have missed the part where you have an external energy source besides the caps and the batteries to cover your losses.

 

Using a 27 volt supply for charging and assuming total resistance at 1 ohm it would take 7.5 hours to reach approx 18 volts, then about another 24 hours to reach above 26 volts. (Assuming the caps can stand initial currents of 27 amps)

If the caps could take 270 amps of curent you could do it in a reasonable time with 270 volts.

 

I am thinking now of using string of 10 ultracaps connected in series 500F each, so it will be supecapacitors bank 50F with 27V and Energy stored E=50*25*25/(2*3600) = 4.3 Wh, so it is able to cover all the losses during energy transfering from ultracaps bank to battery (incl buck/boost DC/DC convertor). Supercapacitors bank will be discharging immediately after charging process is done (as soon as external power source is removed-> the relay closes the circuit).
I also came up with idea, that I can charge supercapacitors only to 80% instead of 100%, and it will be 2-3 times faster, that is why I want to increase total capacitance.
So far as the charge will not be kept for a long time in capacitors, which method of charging balancing will be most appropriate?
Is it possible to charge caps with the current that only their internal resistance allows? or I need to put additional resistors anyway?
Thank you, would be happy to discuss.

I don't get it. If you have room for all those caps why not just use a bigger battery?