I could use some advice on selecting voltage for my build

[Ch00paKabrA]

Hello,

I am excited to finally have my bike together. I just finished wiring it up and bench testing it. It works great.

Here is the issue. I am running a MAC 6T in the rear with a programmable 4110 12 fet controller. Previously I had slapped it together to test everything. I have 2 programs that I have tried and both work fine. I have tried it with 14S and 10S. At 10S I have speed 3 of the 3 speed switch programed to 40% which gives me around 16mph. Full speed is 28 mph which I admit that I rarely use.

When I planned the build, I planned on 14S to get me to right around 40mph. In truth, I got close to that and realized that I just wasn't comfortable at that speed so I generally use 40% or around 20mph. I know the percentages don't really add up, It is just my observation.

Here is my question, Is there a benefit to running it at 14S rather than 10s since I am usually going much slower than either top speed? So should I just keep it at 14S or reconfigure the pack to 10S?

Thanks for the help.

'Cal

 

[motomech]

In general, I would say run the lowest Voltage that reaches the highest speed you want.
For me, it depended on what batteries and charger I already had.
It's somewhat easier to put together and charge a 10S pack as opposed to a 14S pack. You can use 14 G wire with 10S and the sparks are a lot less strong than at 14S
For another thing, there are a number of chargers to will allow you to charge 10S without breaking down your pack.
For a while I tested 10S vs 12S, and to use my 5S and 6S batteries, I ran 11S.
What batteries, and charger do you have now?

 

[23skidoo]

I thought more voltage was better before, but my bmc/Mac runs smoother on 12s than 18s. The throttle response is less twitchy. It doesn't seem to lug on hills as much, especially at low speed.

The power capacity of the motor is more based on clutch and gear life than overheating, and the higher voltage meant lower current, but higher impulses on the drivetrain.

So try to run it on both voltages as long as you can program the controller, and see what works best for your riding.

More voltage can be a way of getting more power out of low output batteries.

 

[USAEBIKECO]

From my experience 48 volt is the best voltage for an ebike.

 

[friendly1uk]

You sound a long way out from your motors efficiency zone. Maybe as low as half that possible. Meaning your power expenditure could be giving you double the torque, Or twice the range, or simply halving your carry for the same range. That would be awesome. If you only need half the battery, you make a saving that would ease the cost of a new motor. Saving vehicle weight and packaging in the process. With future battery savings possible, it could be an investment.

10s is probably the most supported voltage. I see no point going higher unless you want to go faster. If I added more cells, It would be in parallel to reduce cell C rate.

Check the motor graphs against your average speed. Pulling away often will put the biggest gap between them. The slower motor will pull away and get going, while a fast motor is stalled.

My guess.. a Mac10T might save a third in pack size. A worthy consideration.

 

[motomech]

Well yes, a 8T or 10T @v 12S would have been a more efficient system, but that doesn't mean he has to throw away the 6T
As to range VS battery capacity mentioned several posts above, I have never found there was much difference between running 10S/5000mAh vs 12S/5000 mAh. Not enough to measure anyway.

 

[Dauntless]

What would make 48v best? Is that for a specific motor? I like some of what I've seen from EvolutionGTS at 74v. (And more.) But he's building MotoGP bikes.

 

[d8veh]

I'm now changing all my bikes over from 36v to 48v. I'm not interested in going too fast. I like a notor round about 260 rpm. You can get the downtube batteries in 48v, so you can get a nice amount of power with a really neat installation and a nice handling bike.

 

[Ch00paKabrA]

I guess I left out an important piece of information. I am currently using Samsung 18650 29E cells and I have 100 Samsung 18650 25R cells waiting in the wings to built up. The plan was for a total of 200 cells configured either 14S 14P or 10S 20P. I have tried 72 volts and it is too much for the MAC.

I know that there would be a benefit of 2 36v packs that could be run in series at times but for this build, I don't see that as necessary.

Battery weight has been brought up. Would it be wiser to run the higher voltage and use the controller to limit speed because I am using so many cells or lower the voltage and increase the amps. 28mph is fine for me as a top speed as there are only one or two places where I might find it necessary. Mostly (95% of the time), I will be going in the 14 to 20 mph range as that is the max speed of my brother's ebike and we ride together often.

Thank you again and I apologize for leaving out the battery information.

 

[d8veh]

There's no definitive answer to the question. In Europe, Australia and some other countries, 48v is the maximum allowed to be legal. It's obviously safer than higher voltages. There's a much better choice of off the shelf stuff at 48v than higher. Apart from that, it's probably the more the better up to a point.

 

[Ch00paKabrA]

Based on the varied response. I think I will just leave it at 14s since the 3 speed switch is programmable I will just tune it down with that and have the speed available if/when necessary.

Thank you for the responses.

'Cal

 

[spinningmagnets]

If you can easily afford 48V, I think it is always a good thing. It makes it "possible" to use fewer amps to get the same performance (in theory). If you don't have long and steep hills, its possible you may be happy with 10S, and if you haven't purchased your next battery yet, going to 10S/37V might allow your budget to get more Amp-hours (Ah) for more range? Just a thought...

 

[Ch00paKabrA]

Thank you spinningmagnets. I am leaving it at 14s 6p for the time being. before I make a final decision regarding the battery capacity I will need to make the final battery box and see how it fits not only the bike but me. The wild plan is 2 sets of 98 cells 14s 7p each if it will fit.