Lithium/lead ebike batteries...voltage Q

You know I’ve got a Wayscral, Basy 315…Norauto ebike.
An early …rock bottom of the range, lead battery, bedstead iron frame, heavyweight.

I read that someone has discovered that the lead battery, 24 volts, has exactly the same fitting as a newer model, which uses an exactly the same shape LITHIUM battery, but that is more volts. 36. I know if I ask Norauto if its OK to swap the lead battery for a lithium higher voltage battery…they are sure to say no…but all I’ve read so far, online, is that a higher voltage battery, could cause the motor to overheat.
But then what?
I know that its possible to change, from lead to lithium…but…

  • how serious would the bigger voltage be?*
    I mean…what happens?
    Will it catch fire? Or will it just wear out the motor, faster?
    Or not work at all?
    The comment was made by someone who, like me, had an ancient model, and had already decided to fit the lithium battery, without the smallest concern and much delight, as of course a lithium battery is a fraction of the weight of the lead one.
    I have to take a spare battery for long trips, so the weight of the whole rig, is about the same as a tank.
    Perhaps someone knows about this stuff…:grinning:? Thank you for reading this question!!!

Without knowing the full details it’s tricky but I would hazard a guess it will fry the motor windings.

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Thank you John!I’ve read a bit more, since my post,
I’m afraid that must be a likely outcome.
Better wait…:disappointed_relieved:

It may be possible to re wire the 36v cell battery to 24v it depends how the connections are made. The voltage is dependent on how the cells/packs are wired, 36v may be the total of all the cells whereas connecting some in parallel would limit the total voltage to 24v but give you extra longer running.

John, I have considered a build your own battery kit, before. There are easy diy YouTube vids, so I guess it can’t be too difficult, however the cost of a ready made lithium battery, even a cheap one, would make my meddling expensive, as a fail. Im Tempted to have a go, but better try to get the right thing at the right price. I’m just very happy that ebike battery makers, are at last producing cheaper lithium batteries for cheap bikes. About 130 e. Thank you for thinking about it! For me, it will be a magnificent upgrade, from the 2, monster lead batteries, per trip, that I use at present, down to 3kg, from 11 kg plus. and perhaps 40 kms, instead of 25.

Completely understand.

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And make it potentially dangerous to use, not to mention impossible to charge,

36v is 10 lithium cells in series - you could get 24v (or 25.2) with 7 - but pairing up just some in parallel would mean those cells discharging at half the rate - eventually they would wind up trying to reverse-charge the other cells in the pack, which is bad news.

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Build this one in an hour.!!


OK for ebikes with trailers, I suppose…

Agreed Paul, I didn’t know the makeup of the battery, clearly you do but i did say may.

No idea actually, but I do know that the standard voltage of a Lithium ion cell and that batteries with high numbers of cells usually need careful “charge balancing” to make sure that individual cells are not reverse charged during discharge - taking a battery designed with 10 cells in series and re-wiring it with some in parallel and some in series is a recipe for disaster.

LiFePO4 is usually regarded as a better chemistry to replace lead-acid.

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LiFePO4…ah, fireproof?
Much less likely to set your bike on fire/explode. There are some very clear DIY instructions, making a DIY bike battery look very appealing.
This one especially, “Most garage-builders who decide to assemble their own battery pack usually have a lot of experience. However, pack-building continues to be a frequent source of questions from new ebikers, so I decided to put together an article to cover the basics”.

Has anyone out there attempted DIY ebike battery building?. It looks, not difficult, perhaps, easy…

Hi Paul, trying to avoid the subject really as not physically involved but just out of interest looking at Youtube.
I doubt that the 36v battery is just 7 cells as it’s capacities would be short lived powering the bike. So more cells would be used and that may allow a re configuring to what I alluded to. On this vid there are 21 cells used via a small BMS to keep everything within tolerance. 3 in parallel making 7 in series for the 24v.

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Yeah, I glanced at the article that Jeanette linked to and realised we were talking about quite large battery packs - certainly larger than I thought after the 1st post.

Originally it was your comment “36v may be the total of all the cells whereas connecting some in parallel would limit the total voltage to 24v” that worried me - in particular the “some in parallel” for reasons stated above.

You can use series/parallel combinations as long as everything is “balanced” - in which case you would use a multiple of 7 cells (as you said 21) to get 24v. 36v would be some multiple of 10 cells.

So, yes, if your 36v pack were 70 cells arranged as 7x10 (parallel x series) you could re-wire it as 10x7 to get 24v - but you’d still need to change the battery management system to charge it safely.

It’s vaguely interesting as, at some point, I want to stick a solar panel on the roof of the shed as there’s no light in there (and no electricity).

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Never having attempted to make a battery before, I haven’t come to any final decisions about which is the best way to proceed…if I find a ready made battery at the right price, as is possible…its likely I will buy it, However, having anyone look over the kind of battery pack building vids on offer, and the kind of comments you two have made, tells me that it could be a project that is, as most of the instructions claim, within the ability of a not particularly battery minded person. The bits and the tools required, are quite easy to obtain, and although I doubt I could do it “in an hour”, I do not want to attempt anything more complicated than a 24 v bike battery, at present, so feel quite confident.
I know much larger projects are possible. And using solar power to recharge. that has appeal! I use my ebike for almost all travel.
Either to local villages, or to connections, bus and train. Tomorrow, for the first short part of a vital trip to Paris. Links to the big French bike trail network, are close by.
Savings for me, in working out an effective battery build, are likely to be big! Thank you, John and Paul, for your input! If you had said it was rubbish or dangerous or undoable, for any reason, I would probably have given up on the idea.

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Jeanette, if you do have a go at making your own battery pack pls read up on basic low voltage electrics & battery safety and again on battery safety! Only buy good quality batteries all the same manufacturer & type don’t mix & match. Make sure the batteries have no damage at all to the protective coverings if they have any damage or you damage them, you could be building yourself a small bomb or at least a nasty incendiary devise. Be very careful.

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Me too, although I have power it’s to demonstrate yet further how economic pool ownership can be. Unfortunately I have some proper work to do before playing :smile:

Wozza, thank you. I’ve read a bit…(LiFePO4 Paul suggested) . experience teaches more! I had a shiny fast car from Telford auction once…with seriously amateurish wiring. Somewhere on the M4, everything lit up at once, and nothing would switch off. Terrifying, didn’t think I would be able to switch off the engine. But it stopped on a lay by, with everything flashing, till the cops came.
I was sure it would ignite/explode, and kill someone. Very careful now.

DIY building battery kits, getting easier!
Just found this kit, don’t know if its OK to add the link.

VRUZEND – Battery building made simple!

|141x427

No more spot welding… and no more soldering either!

Just snap together the VRUZEND bricks and then bolt together your connections. It’s really that simple!

Lithium battery packs for everything from electric bicycles and skateboards to home energy storage and electric vehicles are crazy-expensive, right?!

Why is that? It’s because making lithium battery packs used to require special tools and highly skilled workers to use them. But not anymore!

VRUZEND lithium battery building kits were designed to solve that problem. The plastic end caps slip tightly over the end of the most common lithium battery cell format, the 18650 cell. They can be snapped together like Lego™ bricks to create any size battery