Are 72 Volt eBikes even Worth it?

Everything you need to know about ebikes and battery volts. We discuss the effect of high voltage 72 volt batteries on performance, power, capacity, and more.
Spoiler, I’m a huge fan of high power 72 volt ebikes. Watch the video for all the details!

Visit my Amazon page for links to my favorite gear, builds, & more!

Disclosure:
Some of the links above are affiliate links. If you purchase with my link I can earn a commission at no extra cost to you.

[jimmyjames]

Some things to keep in mind while choosing voltage are the planned power duty cycle of how you want to use the bike and the potential heat dissipation needed. If you plan for your bike to do extended periods of high output riding then you can have different voltage and hub type needs than someone who expects their high wattage use to be of more limited duration intervals. Geared hub motors have some excellent characteristics including small size. But their compactness and density make it harder for them to dissipate heat versus a direct drive hub that typically has a lot of empty air space inside and a lot of surface cooling area on the outside. In most cases I think 60v is a good maximum for geared hubs and a good minimum for direct drive. Overall efficiency is better with a geared hub. The direct drive advantage is for high speed use where the motor must survive very high wattage so higher voltage is a good choice for them. Voltage choice still mostly boils down to how much speed you want though. A 1000 watt geared hub running 60v with a 40 amp controller can go about 40 mph. But if you are happy with a few less mph you can run less voltage and either save battery weight or add amp hours. If you are working with a 750 or 500 watt motor you just need to make a realistic estimate of the bikes speed potential and select voltage and amps to match. But if you want speeds over 40 mph then I think direct drive is the way to go and 72 volts is a good choice.

[lukewalker]

There is a bit more to it. Size of the motor and controller dictate how many amps can be drawn from the battery. Batteries are not the same. Discharge amperage of the individual cells aka the capacity of the cells to discharge current aka amperage determines whether the controller and motor will be satiated with adequate current. And there is more than that. The BMS inside the battery should be sized based upon the types of cells used in the battery and their capacity to flow amperage. Generally, when spec-ing a battery, you want some 'headroom' of battery BMS amperage rating relative to the maximum amperage you have your controller set at. For example on my most recent BBSHD build which has a 30amp controller, maximum draw, you don't want to use a small maximum BMS amperage rating of 30 amps, because there is inadequate headroom due to battery sag as the battery depletes under high/prolonged load. For that reason, I chose a battery with 45amp BMS. But....using a BMS rated at an arbitrary amp rating means nothing if the cells aren't up to the task of flowing current to satisfy the controller and motor.
To coin an old metaphor, the drapes have to match the curtains if you want good ebike performance and not have your battery BMS shut the motor off because the controller and motor are drawing too many amps the BMS and battery cells can't keep up with.
In summary:
Buy a battery with known, name brand Li-Ion cells whether 18650 or 21700 cells.
Make sure your BMS amp rating covers the maximum current your controller draws with a bit to spare.

[arobertson]

I’d yet to retain much of the amps volts watts formula and it’s significance until this video. Many thanks for the clarity. So easy to get stuck in endless sphere minutiae..

[michaelsprinzeles]

After doing all the research & math years ago I've forgotten most of it. I do remember just the basics overly simplified as
Volts = top speed
Amps = acceleration
Your controller's amp draw basically determines torque so "power off the line". Voltage basically controlls the top RPM of the motor so "top speed".
If your bike seems peppier off the line I'm betting it's just because the more volts you have the longer it takes before voltage sag effects acceleration. Meaning you get full power throttle through more of your ride before it starts sagging.

[brandonrich]

Ok this video was extremely informative. Not only did I learn a ton, but I was very wrong on what I thought how the batteries worked. I clearly didn't understand that a higher voltage battery with the amp hours. Thank you.

[kevins]

I think you summed that up pretty well. Typically it seems like a lot of confusion when it comes to battery voltage, motor ratings and controller limits. I often hear people say running a motor higher than it’s rated voltage will fry it. That simply isn’t true as motors are only wound for a specific voltage for efficiency purposes and it can still work on any voltage. This has been my experience as I run 36v motors at 72v and even over 120v for a while to see how it would handle it. The only difference I can tell is the speed increase and slightly reduced efficiency. So good job on your explanation, it’s definitely needed with so many people wanting to learn about electric vehicles and battery systems.

[SuperRJ]

Best explanation I've seen yet. Thanks man.

[marthamryglod]

The only time lower voltage is worth it is when you have a limited space for batteries and you can take the same number of cells and create more parallel strands than series to get more amp hours in the same package constraints. Top speed will go down but how often do you cruise on a bicycle at 45 miles an hour

[EBikesOKC]

Very informative, I appreciate you sharing

[wolfe]

It all depends on what you want from your ebike, range or power, its pretty much as simple as that....
The same sized battery will have more range on a 48v system verses a 72v system
Its almost like comparing a 125cc to a 250cc, the 125 will go further but the 250 will get you there quicker

[slidersgliders]

I ride 136 volt EUC 👍 .
Awesome video, thanks for the information ✌️ Keep it wheel✌️

[sigmaoctantis_nz]

I wouldn't say they are more efficient or energy dense. There is a slight reduction in wire losses due to running at a higher voltage and top speed is definitely better, but you're going to need current for acceleration.
If you were to limit power output to say 500w, a higher voltage bike will draw a lower current but an equivalent size battery pack (Wh) is also going to be lower capacity (Ah) so the two will be quite comparable. The only difference is the higher voltage bike will hit a slightly higher top speed.
If you were to unlock the full amount of current from your battery pack along with the higher voltage, then you will increase power output, accelerate fast and have a high top speed bike but your battery is going to drain quite quickly. I have that exact issue with my 76v (21s) e-bike which can hit 55 mph/90 km/h but range is quite limited when riding hard.
Energy density depends purely on the type of batteries rather than the configuration, for example lithium ion is more energy dense than lead acid. I'm not even sure why a higher voltage pack would be more expensive if the cell count remains about the same, since the only difference is how they are being configured.

[the_langs]

I would love to see a video about how to build or figure out how to build a super long range bike.

[MaximRecoil]

Voltage doesn't matter at all with regard to performance. The only benefit of higher voltage systems is that you can use thinner wiring for a given level of power output (wattage), because there's less current (amperage).

For example, suppose you have a 5, 000-watt motor powered by a 12-volt battery. That's about 417 amps, and you'd need wicked thick wiring for that. Even 4/0 gauge (which is nearly a 1/2" diameter) would be too thin as it's only rated for about 250 to 300 amps, depending on the length of run.

On the other hand, with a 72-volt battery, a 5, 000-watt motor would only draw about 69 amps, so you would only need 2 gauge wire (about 1/4" diameter) for that, and you could probably get away with using 4 gauge if the run was short enough.

A downside to using higher DC voltage is that it's particularly hard on mechanical switches, which is why the voltage rating for a switch is always much lower for DC than for AC. Even 12 volts DC is hard on switches. That's because DC arcs a lot more than AC as the switch contacts are about to close (which erodes the contacts) and the higher the voltage, the bigger the arc.

Another downside is that it can shock you. 12 volts won't shock you (unless it's, e.g., on your tongue) because the dielectric strength of typical skin is higher than 12 volts. 60 to 70 volts is right around the threshold for where you can get shocked, and with the amount of power that some of these e-bike motors have, the amperage behind such a shock could be dangerous.

[jakefriesenjake]

I'm no pro, but I think that people think that if they get a 2000w hub motor that is 36v, but they only need to go a short distance and want to save money and space on the bike, that they only need a 5ah Now, it might get you your space savings, save you money and it might get you your mileage fine, but where you come up short is not being able to use the 2000w hub to its full potential. Obviously you want power if you bought the 2000w and not the 350w, so it only makes sense to buy the battery that will deliver the power! The 5ah battery won't be able to supply the power and it will heat up really fast.

Where 72v and 84v hubs are better is that they can supply more power (watts) than a 36v battery pack.

With a 36v setup, that can handle the 2000w motor, you would have to push 55.55 amps through the system. If you were at 84v, the amp draw would be only 23.8 amps. The 84v batteries could supply that power and have a healthy easier time doing it.

[Greg-mele]

Good information. Here is yet another factor. The bigger the battery the more ugliness of the bike. It is a trade off. Lately, I have been more concerned about a clean looking bike.

[bliseB]

You really need to be careful what you say.
At 6:21
You say higher voltage battery’s are more power and energy dense. That’s just wrong.

Power and energy density only depend on the Type of cells and amount of cells not the pack voltage.

Using the same cell a 10s4p (36V) has the same power and energy as a 20s2p (72V) because they both have 40 cells.
If you run the 10s with a 20kv motor and the 20s with a 10kv motor you will have pretty much identical performance and range.

[goingoutotheparty]

Amp-Hours is a measure of Capacity. Max. DISCHARGE Current Times Volts determines how powerful your bike can be. Higher Volts need less amps for same power so are more efficient.

[dcryder]

I'm torn between a 2000w 72v setup like you had or a 72v Grin Tech GMAC geared hub motor.... Which would put a bigger smile on your face? 😀

[onetailgunner]

Does marvel mistery oil act like nos in a hub motor . ? ??? Or will it oveheat the motor . I question it because it works in my rc drag cars . Just a drop or two dont blow it . But it's the only oil that can clime to the heat source. Hold the penny standing in a drop of marvel mystery oil it climes onto your fingers its attracted to heat . Why I asked questions first .