Molicel P42A cell discussion

[kook]

good talk and discussion Mooch… always great to have another mind(s) to bounce ideas and thoughts off of… as a community we all gain!!

thanks again

[jack.luis]

Go hang out at Kung Fu Tea on St. Marks street if you want to see them do this live.

[aletheuo]

Hi Mooch, Your reviews are a sort of gospel around here, so it’s awesome to address the legend directly.

I’m probably getting off topic here, but your experience with chargers stood out.

Do you always charge to ‘full’ voltage?

I’m probably splitting hairs and straddling the fence on using a fraction of a battery’s capacity in hovering around nominal voltage vs accelerating aging (cathode oxidization? dendrite formation?) at fully charged/discharged levels. Will both options end up giving negligible differences in total mAh passed through the cell?

The other half of that is that, unless you’re counting coulombs, it seems charging to less than full creates an unknown of how ‘full’ the battery is. LiFePo4 chemistry comes to mind with its flat discharge curve, and (I think?) any charging will spike the voltage by a couple hundredths/tenths of volts. Maybe that would level itself out over the course of a week. Maybe backup power UPS system can live with that characteristic, but that timeframe is a bit impractical otherwise.

[glyphiks]

@bwahl602

BMS only wired for discharge

I think you mean only wired for charge

[Flasher]

@Athrx

or bms will shut down and both turn green

That’s the feature I prefer on my llt BMS. I can forget the charger cus the BMS cuts it off at 4.21 per cell and only turns it back on when balancing causes them to go under 4.15

[b264]

@bwahl602

Most of us use a BMS only wired for discharge (no over discharge protection)

To be clear, Bill is referring to something like this

@b264

BMS bypassed with loopkey and discharging with lights/accessories circuit

@Battery_Mooch

1. When you say “parallel charging” you’re talking about paralleling the chargers, not the packs? That’s a verrrrrrry bad idea for many chargers and I strongly advise against it. But, having said that, there might be ways to do it universally with some additional components on the charger outputs.

So much depends on the particular charger and its circuit though.

Which chargers did you successfully do it with?

@murdomeek

a lot of people in the electric unicycle community does this. Just a straight parallel wire splitter into their wheel
Seems to work just fine for them

I have done this a lot with the MDA 4A float chargers as sold by Evolve, Metroboard, enertion, etc…

@Battery_Mooch

Using any two different chargers or the same model of a specific charger?

I’ve done both. Though anecdotal evidence proves nothing… …it’s highly dependent upon the specific charger’s circuit as you noted above. I also had a 10A fuse on each charge port separately.

@murdomeek

Mind you that they only do this occasionally on long distance group rides. They just charge regularly at home if they don’t need to be fast.

And yeah, this, I rarely do it. Only if I need a full battery in a jiffy

@Battery_Mooch

Conductor current limits have to take the insulation temp rating into account along with what’s acceptable for power losses. You can run a wire right up to its fusing current level and it will still work. But operating a wire at just below the melting point of copper is typically not a great thing to do. This all means that 18AWG wire could be rated at 2A for voltage-drop sensitive applications all the way up to 20A or even higher for pulsed applications where power losses aren’t an issue and silicone or Teflon insulation is used. Let’s talk…maybe there’s some testing I can do with a bunch of 12” lengths of different wire and some nickel strip.

We would love to hear more about this

Conductor Current Ratings [SRO]

I’d like to make an easy-to-find list of current ratings for esk8 use. If anyone has edits, corrections, experience, or thinks it can be better, please describe what you think should be changed. Popular esk8 sizes in bold. [current_capacity] This chart is labeled for continuous and not instantaneous. You can pretty much double every number for instantaneous, for a couple seconds or less. search keywords: wire, AWG, size, nickel, current, ampacity, hot, melt, battery, amps, amp,…

[Battery_Mooch]

@aletheuo

I’m probably getting off topic here, but your experience with chargers stood out.

Do you always charge to ‘full’ voltage?

I do but I don’t really care too much about the effect of charging fully on cycle life as I usually want the longest run time before needing to recharge. If you are not otherwise stressing the cells you can gain a significant increase in cycle life by charging to a lower voltage, e.g., 4.10V or 4.05V for standard li-ion cells. But you will lose up to 10%-15% of your capacity doing this. There is always a frakkin’ tradeoff.

@aletheuo

I’m probably splitting hairs and straddling the fence on using a fraction of a battery’s capacity in hovering around nominal voltage vs accelerating aging (cathode oxidization? dendrite formation?) at fully charged/discharged levels. Will both options end up giving negligible differences in total mAh passed through the cell?

Staying within, let’s say, a 20%-80% SOC range will significantly increase cycle life but you will lose a LOT of run time.

@aletheuo

The other half of that is that, unless you’re counting coulombs, it seems charging to less than full creates an unknown of how ‘full’ the battery is. LiFePo4 chemistry comes to mind with its flat discharge curve, and (I think?) any charging will spike the voltage by a couple hundredths/tenths of volts. Maybe that would level itself out over the course of a week. Maybe backup power UPS system can live with that characteristic, but that timeframe is a bit impractical otherwise.

Yup, charging to a lower voltage would reduce the available capacity and you’ll have to do a couple of tests to measure the actual capacity available.

[Battery_Mooch]

@b264

I have done this a lot with the MDA 4A float chargers as sold by Evolve, Metroboard, enertion, etc…

Thanks for the model number!

[kook]

@Battery_Mooch

Let’s talk…maybe there’s some testing I can do with a bunch of 12” lengths of different wire and some nickel strip.

as @b264 mentioned above… sciencing materials commonly used for P-Grouping, and series connections, would always gather a huge following just as your battery testing has…

I’d really like to encourage this science!

[aletheuo]

@Battery_Mooch

Staying within, let’s say, a 20%-80% SOC range will significantly increase cycle life but you will lose a LOT of run time.

Building bigger and bigger batteries so I can use less of them!

I like 4.10V as a compromise so I’m just falling off the initial voltage cliff. Any lower and I’m driving myself paranoid checking individual P-group voltages a lot more frequently, since I’m not (/shouldn’t be) hitting the BMS’s triggers until a group decides to fall on its face.

@Battery_Mooch

There is always a frakkin’ tradeoff.

You said it

[eBoosted]

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

[whaddys]

Shit, @eBoosted in the house? This place is lit

[Battery_Mooch]

@eBoosted

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.

[Darkie02]

@Battery_Mooch

Thanks for the model number!

@SimosMCmuffin found a EBike company useing 4 x Mean well HLG240 Built in to the bike for charging

[Battery_Mooch]

@Darkie02

@SimosMCmuffin found a EBike company useing 4 x Mean well HLG240 Built in to the bike for charging

Thanks.
Directly paralleled?

[bwahl602]

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.

[ducktaperules]

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.

[Titoxd1000]

@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

[Battery_Mooch]

@Titoxd1000

@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.

[SimosMCmuffin]

@Darkie02

@SimosMCmuffin found a EBike company useing 4 x Mean well HLG240 Built in to the bike for charging

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?)

How Its Made Electric Motorcycles