Hint for an low voltage isolated DC to DC converter circuit - Page 1
Forum section: electronics / projects

author: jmibk
author_rank: Regular Contributor
timestamp: May 01, 2022, 11:56:58 am
content: I'm looking forward to design an active balancer for some lithium cells.For this I'm searching for an insulated dc to dc converter, that- takes the energy from the fullest cell - so the input range is from 3.3V to 4.3V (or a wider range)- and puts the energy into the emptiest cell - so the output should be adjustable (pwm or digital input) from 2.7V to 4.3V (or a wider range)- current from input to output maybe 5 - 10 amps (the bigger the better). This current corresponds to the balancing current.Here the idea of the functionality:Does anyone have an idea for an controller chip to use for this application (most of them I google are normal boost converters without isolation or not able to handle low voltages on their input)?Thanks for reading and maybe some useful tips!

author: Marco
author_rank: Super Contributor
timestamp: May 01, 2022, 05:37:25 pm
content: Never implemented one, but aesthetically I really like the boost voltage multiplier type. No transformers, a single inductor, a single non floating transistor, bunch of capacitors and schottkys. It's just so pretty, I guess the diode drops will limit efficiency, but does it really matter? If you have to balance large amounts of power, the pack is likely screwed any way.https://www.semanticscholar.org/paper/Single-Switch-Multioutput-Charger-Using-Voltage-for-Uno-Tanaka/42909427d7b0591e22b57e1ea3c02437b9603bcdNo real controller necessary if you have a micro, just generate a square wave when the pack gets unbalanced.

author: BrianHG
author_rank: Super Contributor
timestamp: May 01, 2022, 05:47:39 pm
content: Place all the cells in parallel and create a single stage super-efficient boost converter.It can also serve as a regulation stage.No isolation needed.No buttons, switching, analysis of any sort needed.Life is much easier...With smart separate current limited output boost converters, you may selectively automatically drain for each battery compared to it's capacity. Still, no isolation needed, but more than 1 boost converter needed.Or, a current shunt on each battery feeding 1 boost converter will tell you how much each battery is contributing to the total output. Overkill on-off mosfet switch for each battery will offer battery disconnect protection if you really need it.

author: SiliconWizard
author_rank: Super Contributor
timestamp: May 01, 2022, 06:11:18 pm
content: https://www.analog.com/en/technical-articles/active-battery-cell-balancing.html

author: Marco
author_rank: Super Contributor
timestamp: May 01, 2022, 06:13:48 pm
content: Quote from: SiliconWizard on May 01, 2022, 06:11:18 pmI don't see how you'll ever be able to justify that kind of cost except for absolutely massive series-parallel packs.The multiplier one could be used with pretty much any pack, it's dirt cheap.

author: thm_w
author_rank: Super Contributor
timestamp: May 02, 2022, 09:56:13 pm
content: What is the application? Most likely its not worth the effort.You can find Julian messing with many many variations of this: