298:1 HP motor has not running


I have purchased 298:1 HP motor and using DRV8835 motor driver and powered by 3.7v 2000mAh step up the voltage into 5v given to motor driver.The motors are not running, why? if I use 298:1 MP motor , it running.


We carry multiple products that use the DRV8835 motor driver; which DRV8835 carrier are you using?

From your description, it sounds like your motor power is coming from a step-up voltage regulator. Are you using one of our regulators? If so, which one? The HP versions of the Micro Metal Gearmotors draw more current than the MP versions. If this current draw is too much for the regulator, it might be shutting off. Could you test your HP motor by connecting the battery voltage directly to the motor leads?



The motor driver purchased from pololu.com/product/2135 .

yes, It is powering up from 5v stepup volatge regulator and purchased from pololu.com/product/798

That 5V step-up voltage regulator can only output around 200mA, which is probably not enough to run a high power Micro Metal Gearmotor for your application. Under even a light load, this motor will draw more than 200mA. If you are trying to regulate your motor power, I suggest choosing a regulator that can handle at least the stall current of your motor to be safe.


Hi Brandon!

I am using the 298:1 HP Micro metalgear motor (pololu.com/product/994)
I am currently using a 3.7v 2000mAh LiPo battery.
Could you please suggest a suitable Voltage regulator to meet the stall current of the motors mentioned above?

You can find a chart that shows some of the key specifications of the step-up regulators we carry in the “Step-Up Voltage Regulators” category on our website.

The most powerful 5V step-up regulator we have is the U3V50F5, which should work for powering that motor. We also carry a 6V version of the same regulator.


Doesn’t sound like you need a regulator, if you can tolerate a reduction in speed typically about 23% of what 5V would give you. Connect direct to the lipo, it will deliver between 3.4-4.2V, typically 3.8V-3.9V for most of its charge.

But what is your MCU running? If you are running a 5V microcontroller I don’t know if having Vin for the DRV8835 < 5V would cause a problem. You also might still need a regulator for your MCU.

Thank you , I will look at it.

And I am trying to run the 150:1 MP motor with same DRV8835 Driver Carrier powered by 5V regulator,It worked well using 3.7v lipo battery but It’s not working with 3xAAA 1.2V rechargeable batteries. Why?

My guess is your lipo is able to deliver much more current than the NiMH batteries. There are two basic reasons for this.

(1) Is the capacity of your lipo pack more? I assume the AAA batteries are ~800mAh in capacity, I cannot remember exactly what they should be. Is your lipo > 800mAh?

(2) It depends on the formulation, but if the NiMH is designed to replicate AAA alkaline batteries it might not have a very good power density. So maybe it has the same capacity as the lipo pack you had, but it cannot deliver as much current.
E.g: let’s say they are both 800mAh battery packs.
The rechargable can deliver 800mA for an hour
The lipo can deliver 800mA for an hour

The lipo can deliver 1600mA for half an hour
The rechargeable cannot deliver 1600mA for half an hour, and instead heats up when you attempt to take that much.

But I don’t know the specs. My guess is this is your problem, though. You didn’t notice it with the lipo because the lipo can have very high power density, and/or because it was simply a larger pack to start with.

The only other thing to check is whether your 3x1.2V batteries don’t have too high of a voltage. Maybe they have a full-charge of 1.45V and that is 4.35V, too high for the regulator? I don’t know, check the stats.

Both 3.7V Lipo and 3xAAA NiMH has same capacity of 1000mAh(camelion 1000mAh AAA batteries)?

Did my explanation make sense?

It’s good to know the capacity is the same, but the LiPo can still deliver more energy over a short period of time than the AAA can. Batteries cannot deliver the energy stored inside “instantaneously.”

I cannot be certain this is the issue, but it sounds very plausible.

You also haven’t really explained much in what way the AAA solution isn’t working. What do you mean by saying it isn’t working? A thorough explanation can help rule out or better understand some issues.

It was little bit confusion understanding that concept but now I am clear.I have one more doubt that you have mentioned NCP1402 has capable of drawn only 200mA, when I checked with Li-Po battery ,the current was more than 500mA in the closed circuit.How?

Hmm, I am not entirely sure what you are saying- to be honest. The first sentence I think you are saying that the 1st time I replied it was not clear what I meant by the LiPo having more power-density even if it has the same energy-density. But that you understand more now.

The NCP1402 is not something I’m directly familiar with. I understand that you have looked up a datasheet and it says something like only 200mA capable current. This means it is “1/4C” for a 800mAh battery, which is the confusing battery convention of describing the power-density. By convention I mean “the way the battery industry describes and names it”

The LiPo i am not sure what you have described. Do you mean you have taken the (+) lead and (-) and connected them together, while measuring the current. You found 500mAh?
(1) never do this again :p. It is very bad for LiPo and can cause a small fire. Especially many LiPo which is more powerful, like “20C” or more, you would have seen a big spark and many amps and a melted connector.
(2) If you only read this on a datasheet, this means you simply have a (5/8)C rated LiPo battery. If you actually connect the (+) and (-) you will have more than 500mAh, but it will probably damage the battery.

Anyway, I’ll try to respond if you have any questions I can answer. But it sounds like you have confirmed the LiPo is capable of delivering more current than the AAA, even if the LiPo and AAA have the same total energy capacity. This is likely to be a reason why it works better for your application, since motors require high peak current.

By the way, there is a way to test the idea that the AAA does not have enough power density. If you have more than 4 of the AAA, you can connect them in parralel. So something like 2-3 full sets, (8-12 batteries) would be needed. According to the quotes above maybe you will need 3 to know you have as much available power as the LiPo solution.

you will need to make a “4s3p” pack from your individual (quantity 3) 4s packs. I do not know if you have more AAA to test this out.

But when you have more of the AAA in parralel, they can deliver more current.

So one set of 4 AAA batteries maybe can only deliver 200mAh. But 2 sets can deliver 400mAh.

Kannan, could you post more details of how you measured the 500mA draw? Was that the current measured directly from the battery (before the regulator), or from the output of the regulator?

You can get a general idea of the output current at various voltage from the efficiency graphs on the NCP1402 regulator’s product page.


I measured the current with the regulator output, it showed more than 500mA current in 3.7 lipo battery but when it is in AAA batteries it gives only 200mA.

It might be able to output more current for brief periods of time, but that regulator should only be capable of a continuous output of around 200mA. Also, I agree with Tomek that it is not unusual to be able to draw much more current from a LiPo battery than a AAA battery pack. You might try measuring the voltage of the AAA battery pack while the current is being drawn to see if the it drops significantly when loaded with the motor.


Still I am not clear, if regulator has capable of drawn only 200mA output,then when I connect with Lipo battery how could I get more than 500mA but in AAA battery current not exceeds 200mA. Pls explain it.

As Tomek and I have said, we suspect that the AAA batteries cannot supply as much current as the LiPo. Keep in mind that if the 200mA you are measuring is at the output of the regulator, the battery is actually sourcing much more than that since you are stepping up the voltage. I suggest measuring the voltage of the AAA battery pack separately (before connecting it to your system); then, try connecting it to your system and measuring the current draw while the motor is trying to run. I suspect the battery voltage will drop significantly, and since the regulator will still be trying to boost that voltage up to 5V, it will try to draw even more current as the input voltage drops. However, when using the LiPo battery, the battery can probably handle the current draw much better, so the voltage probably will not drop nearly as much.



I have given AAA batteries directly to the motor ,it is working fine. Am I doing mistake by choosing NCP1402 regulator?or Regulators are not a issue here?