Brushless with 4S?

[GrimJeeper91]

I have a Wraith that is purely a multiple purpose rig. I have an array of tires and batteries that I'll through at it depending on the terrain and how much wheel speed I need. It's running stock gearing, Tekin Redline 13.5T (3500kv) brushless sensored motor and Mamba Max Pro ESC. When I'm running slower stuff I'll throw in a 2S or 3S battery. But I do like to get crazy and run 2.8 wheels with large paddles and 4S. This thing flies with the meaty paddles and 4S! After smoking my motor I found out that it's only rated up to 3S. Amazing how long it lasted with 4S and hard running. Now I need to replace my motor. Was hoping for something comparable in performance to the Redline motor I smoked but I'm not finding anything that can handle 4S that's a standard 540 size. Everything that I've found that can handle 4S is a much lower kv rating. Suggestions anyone?

 

[micro racer]

Was hoping for something comparable in performance to the Redline motor I smoked but I'm not finding anything that can handle 4S that's a standard 540 size. Everything that I've found that can handle 4S is a much lower kv rating. Suggestions anyone?

Running 4s on higher Kv motors will often put them outside their RPM limit, which is why they are only offered with a low Kv. For example, 4s or 14.8V (16.8V fully charged) will wind out your 3500 Kv motor to about 51,800 RPM (58,800 RPM) unloaded. That puts it outside Tekin's 50,000 RPM.

Usually, motors are limited more by max RPM than by input voltage. Since rock crawlers rarely wind out a motor all the way, it is entirely possible to drive a high Kv motor on a higher voltage without blowing it up. It should be noted that some motors legitimately can't handle higher voltage because of lower quality materials.

For a standard 540-sized motor, I know Holmes Hobbies has several motors that are 4s capable, though I haven't checked their range of Kv's lately.

Castle's line of Slate motors will also do 4s up to 2850Kv.

Additionally, many of Tekin's Pro4, Pro4HD, and ROC412 motors do offer a few Kv's capable of 4s or higher.

 

[Voodoobrew]

The puller pro 3500kv can run on 4s, same as the Tekin. Same 50,000rpm recommend. I have no idea how the 2 motors are different.

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[GrimJeeper91]

I think I'm going to go with either the Holmes Puller Pro BL 540 or the Tekin Roc412. I just need to decide which.

Holmes doesn't list any voltage limits for their motors on their web site so I sent them an email. Per Holmes, for the Puller Pro BL 540 standard my options are:
3S - 3500kv
4S - 2200kv & 2700kv

For the Tekin Roc412 the options are:
2S - 4600kv & 5700kv
3S - 3100kv
4S - 1800kv & 2300kv

I'd like to compare the G3 Redline motors but Tekin doesn't make it very easy to do so since hardly any spec's are posted.

Unfortunately I don't know what the spec's of my 5 year old Redline were. Regardless, I was overdriving it and probably not getting the full RPM out of it anyways (14.8v X 3500 = 51,800 RPM), particularly with my heavy rig and jumbo paddles. I'm just trying to chose a motor that is designed to handle the voltage with out losing too much top end.

Right now I'm leaning towards the Holmes 2700kv capable of handling 4S. It seems like it should be a good compromise overall.

 

[micro racer]

The puller pro 3500kv can run on 4s, same as the Tekin. Same 50,000rpm recommend. I have no idea how the 2 motors are different.

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I read a while back that it has something to do with intended use. Since the Puller will typically be run at a much lower RPM (and with significantly more drag on the motor at top-speed), the motor will see its max RPM much less frequently than in a race vehicle like a touring car or SCT.

In a technical sense, the fatigue life is a lot longer for the "crawler" motor, even though the motors are physically almost identical, and handle an equivalent amount of overall power.

 

[GrimJeeper91]

Running 4s on higher Kv motors will often put them outside their RPM limit, which is why they are only offered with a low Kv. For example, 4s or 14.8V (16.8V fully charged) will wind out your 3500 Kv motor to about 51,800 RPM (58,800 RPM) unloaded. That puts it outside Tekin's 50,000 RPM.

Usually, motors are limited more by max RPM than by input voltage. Since rock crawlers rarely wind out a motor all the way, it is entirely possible to drive a high Kv motor on a higher voltage without blowing it up. It should be noted that some motors legitimately can't handle higher voltage because of lower quality materials.

For a standard 540-sized motor, I know Holmes Hobbies has several motors that are 4s capable, though I haven't checked their range of Kv's lately.

Castle's line of Slate motors will also do 4s up to 2850Kv.

Additionally, many of Tekin's Pro4, Pro4HD, and ROC412 motors do offer a few Kv's capable of 4s or higher.

I think I've narrowed it down to either the Holmes Puller Pro BL 2700kv or the Castle Slate 2850kv. Decisions, decisions, decisions...

 

[spoo76]

Volt up and gear down while using a Holmes Hobbies motor IMO.
Crawling will be even better on 3S,
4s will get you the speed you want and be more reliable.

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