The battery builders club

How-Tos & Esk8 mechanics
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#9727

I’m looking for some battery advice. The battery will be used on my mbt.
Currently i’m using a 10s9p with 2500mah China cells salvaged from An electric scooter. The range is decent but I don’t want China cells in my life anymore…

I have 2 options that i’m considering, either a
10s9p 30q pack (27ah 135a 972wh for €270 4,32kg) or 10s7p p42a (28ah 315a 1008wh for €332,5 4,69kg)

the 30q is a cell i know and trust, the molicel i know nothing about… What would the die hard esk8 battery builders recommend?

Esc is a 200 flipsky dual fsecs (with the big caps)
Running 80 battery amps.

1 Like
#9728

If you can afford it, I would highly recommend the Molicels. The extra headroom on the Amp capabilities is going to translate into much less sag, longer range, and longer cell life.

3 Likes
#9729

I’d go for the molicels all the way

1 Like
#9730

Hello! Want to get into the battery building side of esk8, but have zero experience. Do we have a good starting point on this forum? For example, a guide to the equipment you’ll need at home and maybe a video on how to build a pack?

Want to make sure I’m doing this right and have quality parts so I don’t burn the house down :laughing:

#9731

that’s a 210 amp
(conservatively speaking pack)

that shit will get some shit done on P42As

3 Likes
#9732

start here

ask insightful questions… there are lots of peeps on here that were once in your exact same situation…

read…
read moAr…
listen and learn…

ask insightful questions

3 Likes
#9733

I guess you’re building it for yourself since that’s basically just the price of raw cells, nice to have that capability.

Number’s wise. Imo you’re overestimating a good bit, the 315A for the molicel pack is not accurate. It’s more like 210A/245A (30/35), but that’s still way higher than 80A cont. you’re pulling so no big deal. You’ll have a little more range from the wh advantage. But also you’ll have a bit more sag from the 30Q’s than you will the moli’s. You can kinda look at it like 80/135 is 60% duty of the pack vs 80/210 is 33% duty. The reduced use of the maximum capabilities will increase cell life as a slight bonus. So with that I would go with the molicels.

Slight sidebar, Is this pack for the MTB in you profile pic? Have you considered 12S? 12S6P moli vs 10S7P moli might be a worthy discussion to have, assuming you other equipment is able to handle that, new chargers and such will be an additional investment.

1 Like
#9734

Hi guys,

I’m working on a battery repair. I won’t name the builder, because its irrelevant right now, but wanted to go over what my plans are to attempt to repair this battery and see what you all think.

For starters, I had to open the build multiple times to check the P group voltages since it wouldn’t charge. On 3 occasions now, I’ve found multiple groups way out of range. I’ve now opened up the pack, and found one P group that had a cell with obvious signs of distress. It was corroded on the + terminal big time, and the shrink wrap had been compromised. Image of the compromised cell with wrap removed for posterity included. On those multiple occasions, I simply “manually rebalanced” the P groups in question.

Opening the pack I realized I wasn’t fond of many things about the pack, but I don’t want to completely disassemble/reassemble the pack for many reasons.

First, I do want to replace the balance wires and connector once my replacement BMS gets here, ordered from LiTech Power, I’m hoping it comes with the connectors and heatsink, but please let me know if you know otherwise. The balance wires will be made to be all the same length, using silicone wire, and completely replace the existing wires. I will be soldering onto the same existing pads.

Second, I plan to replace the serial connection between P groups 1 and 2 using copper plate sandwich method. I plan on spot welding a manually cut out shape, image included, of .2mm copper sheet to fold in half using nickel strip to provide resistance as described on endless sphere. I want to do this to avoid the hodge-podge of overlaying nickel strips and folds for serial connections, as they have shown to be a major cause of concern on this pack. Among many things, I don’t like that the discharge wires were coming out the skinny ends of the P-group, instead of at the very least the middle.

Third, I plan on replacing the + and - collector ends with the same described sandwich method, except here I plan to make the “solder pad” in the middle of the P-group.

Fourth, I’ve added fish paper running down the middle of the pack as there was nothing there, and I don’t want to become the Lithium Surfer.

Does anyone think that the other gajillion joints/serial connections need to be revisited anyways? At this point I feel like repairing the things I’ve pointed out are going to be good enough.

Thanks in advance everyone.

image
image3024×4032 2.58 MB

image image image image image image image

#9735

The max continues Amp values are from NKON where i get my cells. (15a for 30q and 45a for p42a)
I know these values are a little bit exaggerated lol :stuck_out_tongue:
In the past I have had some bad experiences with multiple broken vescs at 12s.
My mtb uses 190kv motors so the speed from 10s is plenty for me. Reason for 10s is purely reliability.

I must say tho that sometimes i miss the raw 12s Lipo power from my previous setup :cry:
I guess the molicel it shall be! Only problem now is sourcing some 30mm nickel.
The 25mm stuff I have laying around is a little bit to narrow.
Links are always welcome!

2 Likes
#9736

Actually you have a little bit of both here. 30Q’s are tested and safe up to 20A (though you will see significant voltage sag at that current).

p42a’s are rated by mooch to 30A/35A continuous. Obviously his tests are continuous ratinga designed for ecig use, so its a little different than esk8 where your amp draw varies widely depending on load. Realistically if you set your amp limits to 45A/cell, you are probably never going to pull enough amps to hurt the cells, especially in 7p. Just good to be aware of these things.

1 Like
#9737

I just started making a brand for my custom battery service, it will be called esk8juice and currently Im getting in to the Instagram game, so over the next few days I will be posting some soft battery porn :smiley:

If you like that than please follow me at @esk8juice :smiley:

Don’t like to advertise this directly but honestly I didn’t read much about getting an Instagram account to do any good haha
So if someone from EU knows how to market well I could make you a battery??

2 Likes
#9738

Yeah, 15A for a 30Q is standard and not exaggerated, but 45A for moli’s is a bit much.

Understandable, 12S can make some more esc’s a lot less reliable.

For cell purchasing, nkon is old reliable, but now day’s EU guys can get cells at fogstar for better prices.

I respectfully disagree with assessing 30Q as a 20A battery. Mooch does not test to an 80*C cutoff and if he did he would hit it when doing a full discharge at 20A. This point is the key. I run my 12S8P 30Q at 100A battery total. And it builds heat, I’ve seen 35-40C after a hard ride. I cannot say I fell safe running 30Q’s at 20A a piece knowing that.

3 Likes
#9739

Fair enough. I was repeating info that is often considered true in the community. I dont really know enough on the subject to weigh in on whether the group-think is true on this or not.

2 Likes
#9740

The price difference for 70cells isn’t that much and I can drive to nkon, buy my cells and get home in An hour :man_shrugging:
No shipping cost and no waiting times, guess i’m Lucky.
I also like that they let me check the manufacturing date before purchasing.
Need to be carefull with them, sometimes their cells can be 2 years or older :confused:

4 Likes
#9741

If multiple groups have been out of range I would just drop that pack and build a new one from fresh cells.

3 Likes
#9743

This! :+1:

#9744

If I’ve fish taped all my p packs, do I also need to shrink wrap them? There’s just enough space for both columns of my pack to sit in my Enclosure, and I’m not sure if it’ll fit with shrink wrap :sweat_smile:

#9745

I don’t believe you would throw an 84 cell pack in the trash because 1P-group has been 3.65V vs. 3.83V twice, and you found a faulty cell in the P-group. The second P-group was low (3.78V vs. 3.83V) when I checked it this last time, and the BMS has clearly failed.

So you guys are saying that if your BMS fails you would just toss the whole pack and start over. Right.

Then again, everyones entitled to their opinion, and I did post to get opinions. I’m not selling this battery to anyone else, I’m the one riding it, and I’m not throwing it in the trash to start over without at the very minimum trying to fix it.

1 Like
#9746

You can do what you want and you know best in which conditions the pack is.
You wrote that multiple p groups have been out of balance. For me out if balance is as minimum 0.2V differences from other p groups. Something a „normal“ (not a smart bms) can’t out balance.
If that is the case than your p groups will drift also in future because there is not only the one p group which had the optical damage somehow fucked, the other packs might have a defective cell (or cell with higher IR) as well.
With this said for me personally it wouldn’t make sense to spend a day reworking that pack just to face the same situation after 10 rides.
If the drift wasn’t that big as we thought it is, than rebuild it if you think it makes sense.

#9747

@Andy87 I do plan on reworking the pack and seeing what happens. Do you have any other suggestions other than the ones I noted to give the pack an opportunity to work properly? I may very well end up throwing the whole pack away if it continues to give me issues, but I’m going to give it a shot at least to rework it.

1 Like