Current limiting; super cap charging a lithium ion battery

Question

Please advise me as to whether or not a current limiting circuit such as this one :

http://www.next.gr/circuits/Variable-Adjustable-Current-Limiter-Circuit-l23013.html

would be the ideal choice for my goal of charging 2 parallel lithium ion batteries with a string of super caps.

My circuit :

1). 7.2 vmax, 210 F super cap string >>

2). Boost convert to 8.4 volts output with a max of 5 A ouput when lithium ion batteries are at a minimum charge of 6.5 volts(i measures the output current with the battery load at 6.5 volt charge level >>

3) current limiter, limit current tfrom 5 A to maximum battery charge rate of 2.4 A ( one battery max charge rate is 1.2 A but I have two in parallel for a 2.4 A charge rate)

4). Load: (2) 8.4 Vmax lithium ion batteries in parallel.

Any advice would be appreciated. I would like to do this efficiently and without the use of resistive current limiting.

Thank you,

Tom

Answer 1

The circuit you show is effectively a resistive limiter, which you say you do not want.

You need a switching charger like the LTC1513 which will do what you want:

This won't quite meet you 2.4 A charge current requirement in the form shown above, but you could boost the current capability of the switch to meet the need.
The pulse current from your supercaps will go up as the voltage drops of course, so you may end up needing 10-15 A switch capability.