I need to charge a 14S LiPo from another 14S LiPo.

The easiest way would be to buy a buck-boost converter with a current limitation, but I couldn't find a single one keeping up with my specs. So I decided to go with two units: first a step-up to slightly over 57.3V (maximum voltage of the LiPos) then a current limited step down. But I also can't find a step-down for these specs neither. I'm, currently at the point where I'm thinking about the simplest way to build an efficient current limiter myself.

An IC that fits pretty much all my needs is the LT3840. It's looking good to me, but almost $9 for a single plain IC of Mouser seems a bit heavy to me. I don't plan to build more than three units but it's still a bit counter intuitive, especially when keeping in mind that I order a few of them for spare.

An alternative would be the L7987 but with its integrated switch I would need three in parallel to handle the power loss.

Please let me know if you know similar ICs or have a completely different idea. Time, or my lack thereof is in fact the main limiting factor over price.

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    \$\begingroup\$ Questions asking for recommendations for specific devices are off topic on this site. This will be closed fairly quickly, I'm afraid. \$\endgroup\$ – Hearth Mar 19 at 15:36
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    \$\begingroup\$ charge a 14S LiPo from another 14S LiPo ..... what problem are you trying to solve? \$\endgroup\$ – jsotola Mar 19 at 15:48
  • \$\begingroup\$ Those are fairly large, dangerous batteries. Be very careful with what you charge them. \$\endgroup\$ – K H Mar 20 at 1:40
  • \$\begingroup\$ Note that you are "really" trying to convert from no less than say 14 x 3V = 42V to (maybe) 58.8V (if you want 4.2V in your target cells)(or 57.3 + wiring drop etc if you want 57.4/14 = 4.1V). ie the converter at most is EFFECTIVELY boosting by about 15V so energy dissipation is lower than in isolated cases and power losses also lower. | If you used an ISOLATED 40-60V in with an ~= 0-15VDC output you can "stand" the ouput on top of the input battery and add a say linear regulator to overall have a not too bad loss system. ( \$\endgroup\$ – Russell McMahon Mar 20 at 6:03
  • \$\begingroup\$ When Vbatin < Vbatout boost converter works and when Vbatin > Vbatout linear regulate. Worst case linear reg efficiency is with full inbat and flat outbat. About 42V/58V = 72% - but usually increasingly closer to 100%. as one battery charges and other falls. \$\endgroup\$ – Russell McMahon Mar 20 at 6:05

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