Synchronous buck converter - step down

[COAR]

I'd like to use my ebike battery as a power bank. From some research it sounds like I need a buck converter, particularly of the synchronous variety. I'd be stepping 52v down to 12v to power a variety of devices that don't have huge energy needs (12v fridge, laptops, phones).

I found the product below on amazon which seems to fit what I'm looking for. It's only 12 bucks and reviews (all 50 of them) are generally positive. Sounds like the output voltage is adjusted with a screw ("clockwise big") and then presumably checked with a multimeter.

https://www.amazon.com/Diymore-Synchronous-Converter-Step-Down-Module/dp/B072BN43P8?th=1

Has anyone used this by chance, or have a specific product to recommend that would accomplish a similar task?

 

[JackFlorey]

I'd like to use my ebike battery as a power bank. From some research it sounds like I need a buck converter, particularly of the synchronous variety.

You don't need it to be synchronous, and indeed a synchronous converter comes with some disadvantages (like under certain conditions, it will try to backfeed the high voltage battery.) However, off the shelf buck converters work well for the application you list above. For 12 bucks, I'd give it a try. I've used Meanwell DC/DC's with good results, and if you really want a small, flexible high efficiency converter, it's hard to beat the Vicor line - but they are pricey.

Be aware that that converter lists "up to 94%" efficiency - which means you will ordinarily see 80-90%. Make sure you take that into account in terms of airflow and energy needed.

 

[john61ct]

With cheap Chinese, assume the ampacity listed is a fantasy, maybe triple what you should use it for without adding heroic cooling / heatsinking.

A small portable DC fridge running 24*7 might use 30+ Ah per day, a gaming laptop much more

so do your energy budget first.

A pair of lead GCs at 200Ah (100 usable) can be under $200 and cared for properly last 6-8 years cycled daily.

Your li-ion battery pack is tiny, more expensive, short lived so much more expensive per cycle.

 

[flippy]

even a good compressor based fridge will pull 4~5 amps, and well into the dozens if it does not have soft start.

no way that thing will survive that. you need something proper like the SD series from meanwell.

 

[COAR]

The fridge (Alpicool C30) has pretty low power usage, it only pulls <30 watts peak (i.e when the compressor kicks on). Charging laptops (basic HPs for work) and phones would be the secondary use and not a strict requirement. It's really just to power the fridge for half a day while we're hiking or at campsite without the car running (to avoid draining the car's 12v). I have a Goalzero Yeti 500x (10.8v, 46.8 ah) which I'd like to return if I can replicate the functionality with the ebike battery.

I considered lead batteries before I bought the Goalzero but didn't really want 100 lbs of them.

 

[john61ct]

So cheap order three different ones and report back here.

But I stand by the battery pack issues, at least measure your actual draw per hour peak vs average for each load device with a coulomb counter

and ballpark your "half a day" energy budget more precisely