Help finding 14s 50.4v lifepo4 bms

I looked around at several bms systems on eBay, none of which really fit the bill. All are either completely overkill for my system or have info barely in English, with no wiring diagram is sight.
Want to find a simplistic reliable bms meant for charging only, to build my battery the right way the first time. preferably easy to connect and one that others here have used/ or have experience with. I will be running 14s3p a123 cells. Charging maximum/rated current around 7.5a would be preferred for 1c charging rate of cells. Trying to spend around $60-70, seeing as I need a fairly simple bms with no real ‘bells and whistles’ Other than charging. I don’t plan on charging up to 3.6v for time sake and piece of mind. so would like to find one with variable voltage cutoff, say, change it to 3.5 or even 3.4v, but that seems like asking too much from one of these without it being a crazy ‘smart bms’ with all that Bluetooth and jazz.

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Didn’t want to post in battery builders cause gets lost in frequent back and forth between others.

Promising Listings:

Kinda decked out, and well priced at 66$ at the cheapest with Bluetooth and app capabilities, but is large and has poor diagrams.

This is awsome! Cheap, easy to use, and follow diagram with layout for discharge bypass… and I believe I’ve seen it’s type before on the forum… this is #1 for sure right now… maybe if I can find It’s smaller version… image

New bms found by @b264

I can see why you want to do this, but based off what I’ve heard by other members who use these cells in their builds, the pack will sag to 3.3v per cell, and stay there until the pack is almost entirely discharged.

Here’s a discharge graph along with quotes from other members:

(Click this one to read the thread, it makes more sense that way.)

Honestly I would just charge it normally. I think you won’t see much of a difference in time spent charging or riding. Not to mention these cells are already rated for a hella long lifetime, extending it probably makes too small of a change to notice.


Lifepo4 tend to have low capacity so often you have no choice, but if you’re not using the whole pack, I say charge it to 90% or below (no balancing), and do 100% once a month or so.

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One of LiFePO4’s biggest strengths relative to li-ion is how long they last. Just charge them full to 3.65V/cell and use the crap out of them. They’ll easily outlast any li-ion pack that you’re being real gentle with.

If you’re going to be easy on a pack, be easy on a lithium-ion pack


Yeah but you can get 2000 cycles instead of 1000 cycles if you charge to 90% :slight_smile:

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Thanks for all the info! Didn’t know they behaved like that under load, good to know. Does that mean you can run higher voltages safely, or would you still not push past the 50v (12s liion voltages?)

Unless you have a motor controller and supporting hardware than can handle it, no.

99% of VESCs \ VESC clones on the market, unless stated otherwise, are 60V max.

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Actually, LiFePO4 is much better than that

Discharging 100% of capacity, 2,000–7,000 cycles (staying above 80% of rated capactiy)
Discharging 10% of capacity, >10,000 cycles (staying above 80% of rated capactiy)

source1 / source2

Compare that to lipo (low hundreds) or li-ion (high hundreds or low thousands) and it’s clear

And if you’ll notice in source 2 they were charging to 4.0V in the cycle testing instead of 3.65V :flushed:

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That’s what I thought happened, but no biggie, I can live with 1000 cycles, or just learn to unplug my board a earlier. I’ll have to look into that for sure

So I’m going to have this board kicking till I’m 40?? My god. There rated for 1000 at full cycle from what I remember from their data sheet (in a 1p setup)

Nvm it’s 4000 cycles!

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Well I’m already past 40 but I just use the crap out of them anytime I want, the LiFePO4 boards.

I only use li-ion when I need the range they offer, which isn’t most trips.

I really think LiFePO4 is under-respresented in this community, and it’s definitely because Range Anxiety is a real thing.


Range anxiety?? Who wouldn’t want to ride longer?

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If you’re going to a store that’s 3.5mi away and your vehicle has an 8 mile range, you should be fine.

But it makes people scared.

There’s reason for that, you need to ride conservatively, you can’t just be mashing the throttle when the light turns green, going full-speed up long hills, et cetera, when you’re pushing max range. It causes mental anxiety.

But once you get used to it, it’s no big deal.

The easiest way to deal with range anxiety is to realize that $10 will get you home in a Lyft at any time, even though in real life you’ll almost never need to do that.


Ohhh like worried about ‘running out of gas’ during your trip
Makes sence

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I think I would just push the board as hard as possible, map/track a path close to my house in gps later, and get a true estimated range rather than some calculators estimates.

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But I can’t do that without having a working bms. So do you guys think this one is a good choice, and do you know others who have used this brand/type before?

I also need some advice on how to wire up so that the bms only charges, and doesn’t interfere with my discharge cycles, as well as where to throw some fuses

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