Hey Mooch, you know you are the gold standard reference around this forum? You are the God of battery testing and I have always used your tests as reference even over the manufacturers everytime I’ve chosen a cells for any of my builds.
So having you here is an honor and a real pleasure, I think you have a lot to contribute, hope you stay around
Thank you for your kind words! Let me know if there is anything I can help with. 
@SimosMCmuffin found a EBike company useing 4 x Mean well HLG240 Built in to the bike for charging
Thanks.
Directly paralleled?
Great info and much appreciated. I’ll respond from the pc in a few hrs. Happy to chat about those things in more detail
I’m testing this currently with a Bluetooth BMS that reports charge current, wired for charge only. A 2amp and 3amp CCCV charger (one from an OEM board purchase and the other a yzpower model from aliexpress)
Simple y pigtail with male 5.5x2.1 barrel that splits to two female 5.5x2.1 all externally. The charge port on the board is female 5.5x2.1 and is fused
Both chargers seem to behave normally as they reach peak current, both taper their voltages appropriately as they reach that level.
I’ve seen no cycling at the top or anything. Have unplugged and replugged them individually without issues and I’ve seen no detectable increases in heat production.
BMS reports 5A at max load and as it nears peak voltage it tapers to around 1.2 amps
This is on 10S voltage. 3p 30q pack I’m testing with.
looked that way. but the meanwell is an LED cc/cv driver so not strictly designed to be a charger. It has no end of charge cut-off.
I have been using one of these for a while with positive results and rely on my BMS to detect the end of charge and disconnect charge power. not tried running 2 in parallel tho.
@Battery_Mooch good to have you here.
What are your thoughts on regen? Like for example how many amps can a cell like p42a handle for 1-3 seconds of hard braking/regen in your opinion
Also can you do testing on how some lipos stack up to lion. Like 100c lipos lmao or 10000mah powehobby lipos come to mind
The P42A is rated at 8.4A charging for 0°C-45°C cell surface temperature. Above and below that temp range the charge current rating drops to 4.2A. I suspect that just about any board will get at least some of its cells above 45°C a lot of the time.
If you accept the safety risk and accelerated cell aging you can, of course, go over these ratings. I’m not able to give you numbers though on how the cycle life is affected and when the internal damage might get bad enough to unacceptably increase the risk of the cell going into thermal runaway.
I don’t know when I will have the time but I can do some LiPo pack testing if there are a lot of requests for a particular pack. I’ll put in the time but someone will have to send me two packs for testing.
A LiPo pack using good cells and well assembled can always outperform any round cell due to the low IR of LiPo’s. Size/weight/cost may or may not favor the LiPo pack but its performance can be better if built well. But the tradeoff is the high sensitivity to temperature, charge voltage, discharge voltage, and any physical abuse of the LiPo cells.
Here’s the video in question:
Battery pack at 1:00 (97V nominal?)
BMS board at 1:30 (Based on the BMS board I’d say the pack is either 27S or 28S)
MW chargers at 4:18 (4x HLG-320H-54A , 2 in series and 2 in parallel for the voltages to make sense?)
It’s important to remember that typically (I haven’t double checked Molicel to make sure) battery manufacturers cycle life ratings are not the “full life” of the cell, rather the number of cycles it typically takes to decrease the capacity of the cell to 80% of original capacity.
I’m pretty sure we had numbers from Molicel on these being regularly burst at 45A. It was something pretty low comparatively to other similar cells, (500-600 cycles? can’t recall and just waking up) but even that was plenty of life for our application. I went into these cells fully aware of this caveat. However, it’s not a simple “this is how many cycles I’m gonna get” scenario with this type of use, even if it were, it’s still only an approximation to 80% total capacity after that use, and the decline from there to fully dead, is a whole different, and more caveat filled situation…
Very difficult for us to get real numbers on total cycle life of cells. Even with the lowest longevity chemistries and use scenarios, it’s likely a couple thousand cycles under abusive scenarios. Although plenty of cells may simply “shit the bed” at some point over a large enough sample size. More longevity focused chemistries with gentle charge/discharge scenarios, this could be in the 10s of thousand cycles.
So yeah, actual real world testing, in any objective manner, regarding the longevity of lithium cells is a lot of tricky work IMO.
What is your opinion on people using “fast charge rating x2” as brake regen value?
Cell safety points aside since i’d rather slam the brakes to save my life and risk a board on fire.
Are we mad? Is passing cell charge rating for a few moments a big no-no?
LOL…gets a little complex…from the P42A datasheet…
Assume 23°C ambient.
Rated 500 cycles at 4.2A charge and 4.2A or 10A discharge, retaining >= 80% of the capacity delivered at 10A (which is 3900mAh).
Rated 500 cycles at 4.2A charge and 20A discharge, retaining >= 70% of the capacity delivered at 10A (which is 3700mAh).
No cycle life specs for nominal charge/discharge rates.
Yeah they’re definitely making it more complex than the typical manufacturers, but I get why; as you say, they’re offering more datapoints for the OEMs. I’m in the “prefer more data than less” camp, even if it gets confusing!
Arbitrary values like “fast charge rating x2” make things easier to set up but completely ignores what the cell may or may not be able to handle well. But it probably works about the same for most decent cells.
Everything depends on your priorities and the degree of risk you want to take. To some, going over the rating at all is taboo. To others it’s no worry at all.
Even approaching the fast charge rates accelerates aging. Just a one second pulse at these higher levels can still cause aging. It’s cumulative. The longer you do it, the more often you do it, the higher the charge current level, the more damage and aging is being done.
I don’t have any data that can quantify the damage and increased risk though. Only that the more it’s done and the harder it’s done the worse the effect is on the cell.
That is a fair answer.
Personally I will take strong brakes over cell longevity any time but I am still curious as to the effect of high current / small duration pulses on some of the more popular cells in our application eg 30Q.
Yeah, Mooch is dead on here about the “arbitrary” factor. Have to consider the parallel strings in the pack and divide that by the single C charge rate to have a baseline in the first place, then look at the cell specs where available to see what’s where in terms of where this can be pushed, on top of this, temp of the pack at the specific time of pushing current into them play a role as well.
For any li-ion cell a high charge or discharge rate can plate out lithium due to the ions piling up at certain locations in the cell, reducing capacity and increasing the chance of eventually having an internal short circuit. Even short pulses can also cause problems at the places where hotspots occur (spot weld points for example). The hotspots can cause decomposition of the electrolyte and that reduces performance too.
As always, the damage is cumulative and dependent on the current level and pulse duration.
I haven’t tested the more popular cells to see which could handle short high-amp pulsing better over the long term.
From my experience so called chargers don’t have a cut off only a relay to stop packs discharging when there’s no mains and a led
My alien power system charger doesn’t cut off
Tho @ducktaperules would be worth a new topic listing the better quality ones that do.
i gather than that the P42A beats the 40T overall, but was wondering if there are any advantages that the 40T has over the P42A. i may need to get the 40T purely for the marginal size difference to fit an enclosure, but aside from size…are there any other benefits?