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Difference between 36 and 48 volt batteries

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Difference between 36 and 48 volt batteries

Old 09-10-19, 06:55 PM
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Bigbadjohn
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Difference between 36 and 48 volt batteries

Is it just the configuration of batteries in series that's different and do I need a different controller for each
can they be used on any motor?

Last edited by Bigbadjohn; 09-10-19 at 07:07 PM.
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Old 09-10-19, 08:00 PM
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Doc_Wui
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The motors will run in general on any voltage, but your controller may not be able to run on higher or lower voltage, Some of this may be component voltage ratings. Some of it may be hard wired voltage references inside the circuits.

Some controllers are dual voltage. They determine whether it is 48V or 36V when the battery is connected, and set the correct low voltage cutoff. Most of my ebikes use dual voltage controllers. I like the flexibility to use either type of battery.

One honest thing about e-bike batteries is that they determine the amp-hour rating by adding the up the individual Ah ratings of the cells in each group, A 48V pack made up of 52 cells with 4 cells in each group (13x4) will be a 48V13Ah pack if each cell were 3.25Ah. A 36V pack made with 40 of the same cells and also 4 cells per group (10x4) will be a 36V13AH pack. Although both of these are 13Ah, packs, they are not the same, as you have to multiply that by the voltage to get the nominal watt-hour, which is 13x48 and 13x36. Clearly, there is more watt-hour capacity in a 48V pack, and that is one reason I like them.

I can also go faster with 48V, but that's not a big deal to me, since I go fast enough on 36V. Some of the performance brands sell bikes with 52V batteries (14 series groups). Most controllers that can take 48V will also take 52V. Mine will, and while I have a 52V pack, I don't need that kind of speed. I bought it just for bragging, Kind of wasted the money since I don't need it,
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Old 09-10-19, 08:24 PM
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Bigbadjohn
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So there are more batteries in a 48-volt pack and the unit has to be bigger
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Old 09-10-19, 08:51 PM
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12 V is the difference
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Old 09-10-19, 10:47 PM
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As DW said, if the amperage is equivalent, the 48V battery will have 30% more cells in series with the same number in parallel (13 X 4 for 48V, for instance; 10 X 4 for 36 V). In general, speed is roughly proportional to voltage, all other things being equal.
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Old 09-10-19, 11:39 PM
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Originally Posted by Doc_Wui View Post
I can also go faster with 48V, but that's not a big deal to me, since I go fast enough on 36V. Some of the performance brands sell bikes with 52V batteries (14 series groups). Most controllers that can take 48V will also take 52V. Mine will, and while I have a 52V pack, I don't need that kind of speed. I bought it just for bragging, Kind of wasted the money since I don't need it,
One main advantage of running a higher voltage is lower current draw. Higher current means higher heat. Heat is bad for electronics and permanent magnets.

Voltage drops as the battery discharges. An advantage of 52v versus 48v is that when the battery is at, say, 20-30% capacity the voltage drop is less, so the power drop is also less.
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Old 09-11-19, 03:18 PM
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Im not sure of your context.
Are you thinking of overvolting your current motor, or of buying a complete bike (or package) with either 36 or 48?


If the latter choosing between the two:
I chose a 36v, because it is lighter, cheaper, and because I can put out 1000 watts with my legs if I need to (or I get pissed off, lol).
48v is better for most people, because it requires less current at the same power (as numerozero said above). Heat is why ebikes fail.


If the former
If you are taking what you have now and converting it youll need a new controller. One feature of the controller is LCV cutoff at low voltage. This keeps you from destroying your battery from running it empty (although to some degree the battery BMS should help with this). Also motor speed is directly proportional to voltage. Going from 36 to 48v on a motor that spins at 20mph, will make it want to spin at ~27mph. But if you ask it to do this and it cant well something is going to overheat and you will fry your setup.



But, I do have a motor rated for 200rpm at 24volts that I run at 36 volts (300rpm). I can get away with it because I have no hills on my commute and Im not gonna bog the thing down.
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Old 09-11-19, 10:12 PM
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You don't need so many amps in a 48v system to get the same power. So the same labour is less demanding on the battery, and it runs down more efficiently.

A 15ah 48v battery is the same as a 20ah 36v battery in cell count and available power. Just configured differently. The 48v may last longer depending how it's used. It also has the ability to give higher power in short bursts, and a higher top speed, if the controller allows.
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Old 09-12-19, 04:19 AM
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Power(W) = Voltage(E) * Current(I)
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Old 09-12-19, 02:12 PM
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Another factor is the AH rating is affected by the current draw. The higher the current the less likely the battery will deliver it's rating. I've never seen an AH rating with the current draw it's rated at, so just from conjecture one might assume you are more likely to get the stated capacity on the higher voltage battery, which can deliver the same power with a lower current draw. It would be a simple matter to check the specs on the cells used in the battery assuming you know what they are. One of my eBikes is 36V because it was the bike I wanted at the right price. Which is way more important than the difference in voltage.
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