Is it okay to use a 52v 14s battery with a 48v ebike system (48v controller and 1000w motor)

[datree2]

Is it okay to use a 52v 14s battery with a 48v ebike system (48v controller and 1000w motor)?

im making my own battery packs out of used laptop packs.
ive made a few 48v packs but i read that these packs made from reused cell will not
have the same life expectancy as new. which makes sense. so to combat that would making
batteries at a higher voltage then extend whatever life these batteries have left?
also will using a 52v battery which fully charged goes to 58v on a 48v system blow the controller?
what if i used a battery charger that would only charge the pack up to 54.6v?

 

[e-beach]

The answer is that you have to check the specs on the capacitors and mosfets in your controller. That means opening it up and taking a look. Most of the time 48v controllers can handle 58.8v, but there are no guarantees. Sometimes one can open a side cover on the controller and see what is inside, but most of the time all the little screws on the side of the controller need to be removed so the pc board can be slid out.

 

[john61ct]

The motor no worries.

Best to buy a controller spec'd lots higher than the maximum voltage you plan to ever feed it.

If you already have a controller where you're not sure, if it's cheap then just assume it won't last long, and order a better replacement to have on hand.

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The only significant reason to even go to a higher voltage is to get a higher top speed.

Doing so will **not** somehow magically extend the useful life of bad cells comprising your pack, not sure where anyone would get such a loopy idea.

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If by "52V" you mean 14S, well over 56V is required for decent range, ideally holding CV as amps decline.

57V and stopping, CC-only would be OK.

Absolute max is 58.8V.

Of course charging the battery while disconnected from the controller means the latter won't see anything over say 56V for long, under load the pack will drop below 54V very quickly.

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I personally would never bother with used laptop packs, but if I did, capacity testing of each cell is critical, plan on starting with lots more than you think you need, then tossing a large percentage.

Excellent balancing gear, works at a wide range adjustable "start voltage", high balance charge rate, is essential.

Very conservative SoC cycling, avoiding the shoulders of the voltage curves, automated BMS HVC & LVC based on per-cell/group voltage not pack level.

I would not use solder nor welding for such a pack, periodically "atomizing" and re-testing each cell, replacing the bad ones and re-assembling, like every few months or 50 rides maybe really is the way to get good value using crappy scrap cells

so you need an assembly method that makes the dis-re- assembly process easy.

Of course then the fittings likely cost more than your cells

 

[datree2]

Ive seen that fully charging 18650 creates dentrites which cause the cells to die quicker. My thought process was since these are used cells they probably already have alot of these dentrites so best not to fully charge them in hopes they might last longer.
yea im starting to become aware that using used cells is alot more work than it seemed to be at first but i enjoy building batteries so im looking at it more as a hobby than anything atm.

my plan was to make a 14s battery.(spot welded tabs) test every cell maybe fully cycle the completed battery a few times after the initial build before putting it on the ebike in case i have any early crappers. but only use a 54.6v charger. so that the batteries only ever get to 3.9 at most. so then once its charged to 54.6 i can use it in a 48v system with no problems. the only issue i can think of is drain the battery fully.
i dont want to go below 3v on each cell soooo that means i can only bring the pack down to 42v from 54.6v
whereas if this was a normal 48v battery pack i would be able to bring it down to 39volts and still keep all the cells at or around 3v.

i dont know. honestly i have a couple 14s bms's and battery boxes that are designed for 14s, that i could make 13s but im just thinking of trying something new.

btw i am using a decent bluetooth bms so i can check temps and volts. i am aware that using these batteries are dangerous. and i check them after assembly regularly

 

[dogman dan]

In general, a 48v controller has 60v caps at least, more commonly 63v. So charging to 58v no particular problem.

That may be different for some controllers, they might have a 13s intended, and then have a Hvc at 56v or something. You won't see that on generic scooter or bike controllers though. Maybe on something from Bosch or Trek, but not on most stuff.

You might have an HVC, but it wont be below 60v I bet.