All LFP is the same right? No, and not knowing the difference can lead to disappointment, or even cell abuse.
I'll go so far as to say that @Will Prowse teardown of Miady battery demonstrates this, amongst other things reserved for comment later. I thank Will for his teardowns, so not a critique of the man, just a comment about something he may have missed.
Basically there are TWO types:
1) Energy Dense LFP (designed to actually start a vehicle). Headway, A123, Shorai, K2, Kokam, etc)
2) Power Dense LFP (not designed to start a vehicle, but designed for long power draw). Most of the prismatics and cylindricals not mentioned above.
You can fake the ability with power-dense cells to start a vehicle with added capacity, but this is not recommended.
The cells used in Will's Miady test are of the second category, power-dense. Think overgrown garden solar-walkway cells. Even if you take a bms out of the equation, a limited 0.5C charge rate is a giveaway. Does that mean they are bad? No, they are just designed for a specific application - long power draws, not high energy bursts.
A chart of the difference may help understand. In past years, when EV was the thing, using large prismatics was very popular. Brands like Sinopoly, Winston, A123 pouches diy, GBS, Headway, Kokam all had differing densities, and were best suited for different applications.
Not knowing this, meant abuse if you didn't get it right. Most of us discovered it by trial and error and repetetive flaps of the open wallet.
So here's the chart. Go to the last image for a quick peek. Guess where the Miady cells fall? Wonder where most of our inexpensive modern prismatics fall?
The chart is a bit stale, but useful for demonstration.
The gist of what I'm saying is that Will's test of the Miady cells should have been much gentler. Take it easy bro when first testing those solar walkway cells out of the gate! Especially given the price, the consumer is expected to be the one doing the initial balance by more normal cycling, where the bleeder resistors have time to operate. The hammer test on these unbalanced batteries may actually have done a little bit of damage - but I have no way to prove that.
In the end, extreme examples exist of why you should know where your cells fall in this curve.
1) Trying to start a motorcycle, let alone anything else with a Miady battery is a bad idea.
2) Building a large house-bank out of Headways, or in my case once Shorai starter LFP batteries, is a total waste of money. In power-dense application, you are paying for an energy capability that you are not taking advantage of. A mismatch of application. And a bloody wallet if built to any reasonable house-bank capacity!
Moral: if you are using Miady's, please give TIME for those weedy little bleeder resistors a chance to work on those non-balanced /random-pulls from the assembly line and tack-welded, lower your cv to normal values, and don't hammer them right out of the gate. There is a reason a Miady is not a Battleborn and not priced like one up front. Don't test it like one right out of the box. A little TLC with solar walkway lights inside goes a long way.
And you are still not advised to start a vehicle with a Battleborn either. Match the power vs energy density to your application, and one won't be disappointed, or suspect of getting "B" grade cells.
They may in fact be "A" grade cells intended for their power application based upon their power-density. But as usual, keep an eye out for sharks trying to re-classify garbage from being initially designed for being energy-dense to suddenly being power-dense after abuse.
I'll go so far as to say that @Will Prowse teardown of Miady battery demonstrates this, amongst other things reserved for comment later. I thank Will for his teardowns, so not a critique of the man, just a comment about something he may have missed.
Basically there are TWO types:
1) Energy Dense LFP (designed to actually start a vehicle). Headway, A123, Shorai, K2, Kokam, etc)
2) Power Dense LFP (not designed to start a vehicle, but designed for long power draw). Most of the prismatics and cylindricals not mentioned above.
You can fake the ability with power-dense cells to start a vehicle with added capacity, but this is not recommended.
The cells used in Will's Miady test are of the second category, power-dense. Think overgrown garden solar-walkway cells. Even if you take a bms out of the equation, a limited 0.5C charge rate is a giveaway. Does that mean they are bad? No, they are just designed for a specific application - long power draws, not high energy bursts.
A chart of the difference may help understand. In past years, when EV was the thing, using large prismatics was very popular. Brands like Sinopoly, Winston, A123 pouches diy, GBS, Headway, Kokam all had differing densities, and were best suited for different applications.
Not knowing this, meant abuse if you didn't get it right. Most of us discovered it by trial and error and repetetive flaps of the open wallet.
So here's the chart. Go to the last image for a quick peek. Guess where the Miady cells fall? Wonder where most of our inexpensive modern prismatics fall?
The chart is a bit stale, but useful for demonstration.
The gist of what I'm saying is that Will's test of the Miady cells should have been much gentler. Take it easy bro when first testing those solar walkway cells out of the gate! Especially given the price, the consumer is expected to be the one doing the initial balance by more normal cycling, where the bleeder resistors have time to operate. The hammer test on these unbalanced batteries may actually have done a little bit of damage - but I have no way to prove that.
In the end, extreme examples exist of why you should know where your cells fall in this curve.
1) Trying to start a motorcycle, let alone anything else with a Miady battery is a bad idea.
2) Building a large house-bank out of Headways, or in my case once Shorai starter LFP batteries, is a total waste of money. In power-dense application, you are paying for an energy capability that you are not taking advantage of. A mismatch of application. And a bloody wallet if built to any reasonable house-bank capacity!
Moral: if you are using Miady's, please give TIME for those weedy little bleeder resistors a chance to work on those non-balanced /random-pulls from the assembly line and tack-welded, lower your cv to normal values, and don't hammer them right out of the gate. There is a reason a Miady is not a Battleborn and not priced like one up front. Don't test it like one right out of the box. A little TLC with solar walkway lights inside goes a long way.
And you are still not advised to start a vehicle with a Battleborn either. Match the power vs energy density to your application, and one won't be disappointed, or suspect of getting "B" grade cells.
They may in fact be "A" grade cells intended for their power application based upon their power-density. But as usual, keep an eye out for sharks trying to re-classify garbage from being initially designed for being energy-dense to suddenly being power-dense after abuse.
Last edited: