batteries with screw terminals?

DNG here. I am trying to figure out a 48 Vdc battery pack for a proposed mid-drive build. I will need to maintain the battery pack, so welded packs are simply off the table. They may be wonderful indeed, but they are not user-maintainable, and I am not rich enough for multiple packs. Also, I have zero interest in any "promising" new technologies using unobtanium and available nowhere, at any price. For me, I believe the answer will be common (possibly cylindrical) commercially-sold batteries with screw-type terminals. Advice is welcome here, of course.

By Part Number, how many batteries out there are in current wide-spread use, with screw-type terminals? It would be great if these batteries never explode or burn spontaneously, but beggars can't be choosers. :wink: I am more interested in long miles between charges, rather than some ultimate in acceleration or top speed. Thanks in advance.

The pouch EIG cells I've been using for years are screw terminal, when in their supplied holders. Bolt together in stacks with busbars in whatever configuration you make the busbars for. I'm using the C020 version, NMC, but they also make LiFePO4 if you prefer that.


The most common DIY pack cell is headway, but they overspec their cells.

There are a lot of prismatic "box" cells with screw terminals, but most of these are quite large for their capacity, becuase of the plastic box each cell is packaged in (not removable). Winston, CALB, Thundersky (often called Thundersag, because most of these cells are like the headways, and overspec'd so they sag a lot in voltage under their "rated" loads).


Outside of screw terminals, there are various compression schemes for 18650 and similar cells, though if compression is not sufficient and not even across all the cells then the connection resistances can cause imbalances between cells in a group and between groups.
There

If your pack is made from new cells and properly assembled, charged, and balanced, you shouldn't need to break it down before replacement.

LiPo is great too, and easy to reliably assemble into your pack configuration.

Other things equal, cells with screw terminals are probably a little heavier from the terminals and reinforced case.

amberwolf said:

The pouch EIG cells I've been using for years are screw terminal, when in their supplied holders. Bolt together in stacks with busbars in whatever configuration you make the busbars for. I'm using the C020 version, NMC, but they also make LiFePO4 if you prefer that.
There are a lot of prismatic "box" cells with screw terminals

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Amberwolf,

Do you have a Part Number, and a source for those EIG cells? Google thinks that I can read Chinese.
What does "prismatic" mean, concerning batteries?

Thanks,

flat tire said:

If your pack is made from new cells and properly assembled, charged, and balanced, you shouldn't need to break it down before replacement.

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Flat Tire,

Seems like I would be tossing a battery pack away, any time one cell goes bad in the pack.
I wish I could afford that approach, even once.

X2flier said:

flat tire said:

If your pack is made from new cells and properly assembled, charged, and balanced, you shouldn't need to break it down before replacement.

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Flat Tire,

Seems like I would be tossing a battery pack away, any time one cell goes bad in the pack.
I wish I could afford that approach, even once.

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The liklihood of one cell going bad under the quoted conditions is so remote that you actually can afford it (risk management = liklihood of risk * expense = ridiculously low * moderate = pretty damn low).

There are plenty of screw terminal batteries available. And many are LiFePO4. Both cylindrical and prismatic. Check the DIY EV sites and suppliers, as this is generally where they are used. They were used on ebikes at one time, I even bought a set when I started. But no one uses them on ebikes anymore as they are not as weight or space efficient, nor are they low cost. But they are maintainable as you desire, and clearly they can work.

I build LiPo packs with screw terminations, but here's the catch:

Building repairability into the pack means not gluing the cells in place inside the enclosure. This makes them less robust and more susceptible to fretting and physical damage... creating a reason to repair it

If you built modules which can be screwed together for more capacity or higher voltage, they would take up a fair bit more space.

X2flier said:

Do you have a Part Number, and a source for those EIG cells?

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Part number is EIG ELPB C020
http://www.eigbattery.com/_eng/designer/skin/02/01_03.asp
AFAICR it's a Korean company.

I don't know the source for new ones, other than EIG directly (by the palletload; some group buys have been started but I don't recall the results), but if you look around you can find people selling old Zero motorcycle packs that were made from them, and other packs of used cells. Were some in the for-sale used section here on ES; misht still be there.

The ones I have were used , unknown condition/etc when I got them, and I haven't had any issues because of that yet. (not that I use them near their limits, normally).

What does "prismatic" mean, concerning batteries?

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Usually means a plastic box style cell. Look up images for the names I posted previously for examples. Usually the screw terminals are both ont eh same end. Their cases are thickwalled and heavy because they have to help compress the cell layers inside, and usually require more external compression from the battery box to keep the cells contained (kinda like RC LiPo) so they dont' swell up and fail from gas formation inside the cell layers.

The EIG cells don't appear to act this way; they dont' have complete compression possible with their hardware; but there is containment and some compression possible, but I haven't had any troulbe with cells swelling up except for the single cell that went reverse voltage on my lighting pack when it was accidentally left on till drained past dead (wasn't completely balanced because all the cells weren't the same age/capacity/etc). (I don't use a BMS).

Alan B said:

There are plenty of screw terminal batteries available . . . And many are LiFePO4. But no one uses them on ebikes anymore as they are not as weight or space efficient . . . they are maintainable as you desire, and clearly they can work.

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Alan B,

Yeah, no doubt there are many out there; a few trusted (proven) Part Numbers and/or suppliers would be much better for me than just shooting in the dark. The lack of such (experienced) information is what holds back a lot of people who would otherwise be building ebikes.

To me, some extra expense, weight, or bulk is FAR better than throwing away an entire battery pack when one cell fails. I wish I had enough knowledge, experience (and equipment) to guarantee my total success with batteries that I never used before, but I do not. From the battery disasters that I read about, such an expectation is just not realistic here.

Thanks for the responses, certainly.

What are the amp demands of your controller. Your battery must match your demand of it. Most battery failure is due to people making over demands of the battery. Or frying it so to speak. This is the information we need to truly help you.

999zip999 said:

What are the amp demands of your controller. Your battery must match your demand of it. Most battery failure is due to people making over demands of the battery. Or frying it so to speak. This is the information we need to truly help you.

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999zip999,

That is all up in the air, for now. I hope to use a 1000W motor, but the shifter kit from Sick Bike has a 3000W motor. I have not found an equally complete mid-drive kit yet, with the (preferred) smaller motor. If I can refit that kit with a smaller motor, everything they supply should be more capable than what I need, but that would be fine by me.

I would prefer to avoid the no-returns, no-service problems of some imported gear. I like the idea of running the motive power through the bike gears, for reasonable climbing ability, with a comparatively smaller motor and battery pack. Suggestions are welcome here.

Looks like sick bikes doesn't sell those anymore. So ? A Cyclone 3000 from Luna cycle ? Or ?

999zip999 said:

Looks like sick bikes doesn't sell those anymore. So ? A Cyclone 3000 from Luna cycle ? Or ?

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999zip999,

Okay, starting over from scratch, then . . . 1000W~1500W mid-drive, complete kit . . . I'm still looking.

Thanks; you know, that SB kit would have done it for me, except for the batteries.

Alan B said:

But no one uses them on ebikes anymore as they are not as weight or space efficient, nor are they low cost.

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Some of us do.

X2flier said:

Alan B said:

There are plenty of screw terminal batteries available . . . And many are LiFePO4. But no one uses them on ebikes anymore as they are not as weight or space efficient . . . they are maintainable as you desire, and clearly they can work.

Click to expand...

Alan B,

Yeah, no doubt there are many out there; a few trusted (proven) Part Numbers and/or suppliers would be much better for me than just shooting in the dark. The lack of such (experienced) information is what holds back a lot of people who would otherwise be building ebikes.

To me, some extra expense, weight, or bulk is FAR better than throwing away an entire battery pack when one cell fails. I wish I had enough knowledge, experience (and equipment) to guarantee my total success with batteries that I never used before, but I do not. From the battery disasters that I read about, such an expectation is just not realistic here.

Thanks for the responses, certainly.

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Problem is, the suppliers I used don't carry them anymore, they are history for ebikes, mostly you'll find them in larger EVs which this forum doesn't have much of. The cylindrical cells I had were Headways (didn't recall that when writing the previous), I still have a few for 12V applications, they would never go on my ebikes now. They are heavy, large, costly and didn't handle much current, and we had at least one burst into flames here on ES. Serviceability is nice, but better to make sub-packs of 18650's like Justin did rather than accessibility for every cell. Then if a sub-pack gets a bad cell swap it out, and you can service the welded cell sub pack if you want to. But if good cells are matched before connection they generally live or die together. Single cells randomly failing is not the usual problem. what you read about is the exception, no one is writing about the majority of packs that never do anything interesting except work. Ebikes are very sensitive to pack size and weight, the smaller and lighter the better the experience. Many or most of the pack failures you read about are made from low quality cells, don't do that and the reasons for making them readily serviceable are vastly reduced. Time and again I see folks building packs from sketchy cells, trying to save a buck and getting burned.

It is your choice how to proceed, but the ebike market has moved on from the product type you are trying to use. It was popular 10 years ago.

You can bolt together pouch cells.

Alan B said:

Serviceability is nice, but better to make sub-packs of 18650's like Justin did rather than accessibility for every cell. Then if a sub-pack gets a bad cell swap it out, and you can service the welded cell sub pack if you want to.

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Alan B,

Before I guess wrong again, please tell me what is meant by "sub-packs." I gather they are modules made of single cells that can be connected together to add up to the needed Voltage/Amps, but how many cells are typical in a sub-pack, and are they welded?

A search for "Justin" here gave me about 9900 hits, so I can't say what he did, exactly.

I have no welder (nor those skills) but I'm good with silver solder. 8) Are any sub-packs available on the open market, or maybe from the basements crew? Thanks.

AFAIK he's referring to LiGo from Grin Tech http://ebikes.ca

Justin of Ebikes.ca made 10 cell sub-packs and potted them in epoxy for ruggedness and safety. So they are 36V at about 2 or 3 amp hours. If a cell fails (and they only rarely do that) you don't lose the whole pack, which would consist of a bunch of these in parallel, just the one sub-pack is affected. A typical pack would consist of 5 to 10 of these sub packs. You could make sub packs of cells in parallel instead, then a failure of a sub pack would only reduce the amp hours of that unit rather than causing a big problem, so a repair would be paralleling another cell to restore the capacity.

It is better to get good cells in the first place, then repair won't be needed.

Alan B said:

Justin of Ebikes.ca made 10 cell sub-packs and potted them in epoxy for ruggedness and safety. So they are 36V at about 2 or 3 amp hours.
It is better to get good cells in the first place, then repair won't be needed.

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Alan B,

Thanks. Are these sub-packs welded?

I agree on the quality issue. What brand names and suppliers will have such good stuff, at reasonable prices?

Thanks again.

Well, it's back up again at Sick Bike; a complete mid-drive kit, ~US$360, 36~48 Vdc, 3000W.

http://sickbikeparts.com/electric-shifter-kit-programmable-3000w/

I would welcome all best estimates of the battery pack (specs and cost) that would run this rig nicely, without any regard for great top speed, although range will be a reasonable consideration. I would be happy with a range of maybe six miles (10 km), for a good start. Exceeding those requirements is just a needless expense now, for me. I may add a second battery pack later, in parallel, to extend the range if needed. Price counts, sure, but not enough to buy soon-useless junk batteries. Decent batteries, decent price, makes for a winner to me.

It's possible that I will build my own battery packs, if nothing out there is good, and at a fair price. The bottle batteries seem to be overpriced and rather weak generally, but there may be better versions that I have not found yet. All suggestions are welcome.

If anybody has recommendations for a better mid-drive kit and maybe a less powerful motor, that would be welcome here, certainly. I do value running the motive power through the bike gears, the freewheel at the bike pedals, and the freewheel at the motor, for this kit. Those three items are minimums, to me.

Thanks in advance.

This is the kind of "maintainable" battery pack that I would favor, from both personal and economic viewpoints. It uses flat-top 18650 cells, without any terminal screws on the cell itself. I would write the installation date on each cell, as they are installed or replaced. Any comments or suggestions for a battery pack like this will be respected here, of course.

https://endless-sphere.com/forums/viewtopic.php?f=31&t=87434&start=425#p1361020

Several improvements were made, throughout that VRUZEND /ES thread.

Is that a 40 amp controller or is it more than 40 m I couldn't tell I would go 48 volt and know that kit that is snap together is only for a 1200 watt motor not 3000 watt. A high performance 3000 watt or more battery needs to have good series connections.. or get that Style battery and buy a banfang 750 watt mid Drive do not compromise on the battery with high power

999zip999 said:

Is that a 40 amp controller or is it more than 40 m I couldn't tell I would go 48 volt and know that kit that is snap together is only for a 1200 watt motor not 3000 watt. A high performance 3000 watt or more battery needs to have good series connections.. or get that Style battery and buy a banfang 750 watt mid Drive do not compromise on the battery with high power

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999zip999,

Thanks, I think I'm getting closer to good choices, now . . .

I can only report that the Sick Bike specs say 40A continuous, 100A maximum for the controller. They have a speed limiter for it, but I don't know how they achieve that trick. I would not object to a smaller (in Wattage) motor, anyway. Do you have a good source for "a banfang 750 watt mid Drive," and will it be a complete kit? Is there a 1000 Watt version?

Which "kit" is limited to 1200W? The battery assembly? I am curious about how that 1200W limit was set, if so. If I can locate a decent 1000W motor, will I be okay there? I am not really looking for holeshot acceleration, or great top speed, just a nice cruiser ride, mid-drive power through the bike gears. (I have a Yamaha FJR, for that extremely rapid stuff.)

Thanks again.