Slickest way to charge portable packs?

[hour]

First post, thanks for having me

I've built a few 12v portable lifepo4 packs ranging from 320wh-2.2kwh but it's time to start playing around in 3.7v land and making the most of my new spot welder(s).

The problem with my existing lifepo4 portables is that I could never figure out a safe and reliable way to charge them. I've then defaulted to buying Victron 75/15's and increased the enclosure sizes to accommodate. While this has given me the ability to set custom params (3.45v per cell is what I charge to) and the ability to charge from solar, 24v bricks/PSUs, and even USB-C PD @ 20v with trigger/spoof/decoy devices, they add bulk and are over $100 a pop.

I'd like to make the most of the increased energy density in the new builds by keeping things as compact as possible. Glorified power banks used for running my macbook. No fuse box, cig sockets, switches, gizmos. I'll also be fine without the ability to charge these from solar.

Slickest way I can envision: bidirectional USB-C PD. 60 watts would be fine and it seems standard for many of the power banks and "solar generators" available. The problem is I can't find boards that do this, still, despite no-name brands flooding the market with their products ranging from 3S to 4S configurations, some in lifepo4 too. I figured these generic companies would be using generic stuff easily obtained from aliexpress. Doesn't seem to be the case.

The second slickest way would be a 2.1x5.5mm panel mount jack that runs to a buck converter. Plug in a 24v brick, or my 20v PD decoy/spoof/trigger and let it go to town. I just worry over reviews (on dozens of buck converters) stating that they notice a blip where input voltage is passed straight through. And also overcharging, something I don't have to worry about with the MPPTs. They hit absorption and then quit since my float is set low.

If anyone has any leads on the bidirectional PD thing or has an idea of how to accomplish this, I'm all ears and would greatly appreciate the lead.

Thanks!

 

[jonyjoe505]

I use buck converters to charge my 3s li-ion and 4s lifepo4 small battery packs. I use any 18 volt or higher laptop charger to power the buck converter. I would avoid using the 5.5mm mount jacks unless they are heavy duty that can handle 3 or more amps, I had some of the cheaper ones get real warm, so I avoid using them.
But on the buck converters make sure and use a fan they can get hot if using at high amps. Buck converters work extremely well and will give your battery a good charge. I also added a small led volt/amp meter to the buck converter so I can easily adjust the volt/amp output and see charging status in realtime. Adding a led volt/amp meter (5 dollars) makes life so much easier when using the buck converter.
I used 3 different type of buck converters and never had any problems with them overcharging. Only problem I ever had was a boost converter that shorted out from overheating and blew my main fuse. Because of that situation I always add an extra fuse (even if the buck converter already has a fuse). Some boost/buck converters don't have built-in fuses, I would avoid those.
On youtube there are many reviews on common buck converters that are sold, you can see them in action as far as how much power they can really handle.


This is one of the buck converters I built, I don't charge at more then 6 amps for my small 10ah lifepo4.

 

[hour]

I use buck converters to charge my 3s li-ion and 4s lifepo4 small battery packs.

Sweet, good to know it's an option. With a 20-24v input I'm pretty content with the charge rate even if the packs can handle a lot more, going through 2.1x5.5mm "10 amp" jacks run @ 5 amps. I'll probably do the power pole pivot though as I've done so many times before. I'm just a sucker for a tidy connection.

Buck converter and fan will certainly fit more neatly in the box than an mppt.

Thanks!