L-Rider Robust limited to 9 watts

[Sinister Dexter]

I have a Robust and it doesn't perform well with high resistances. I knew it must have some limitation but it's not documented anywhere. I wanted to figure out what the limit is so I know what will work well on it.

PBusardo recently reviewed the Robust and showed voltage measurements at several resistances:
1.5 ohm gets 3.7 V maximum, set it higher and you still get 3.7
2.2 ohm gets 4.5 V max
3.0 ohm gets 5.2 V max

All right but what does that tell us about the limitation? Use the numbers to calculate power with P = V^2 / R. All three loads work out to 9.1W power. The Robust doesn't have an amp limit like some devices, it has a watt limit. It can't supply more than 9.1W.

This means above 2.0 ohms, you are not going to get a quality vape. High resistance cartos/atomizers require higher voltage but the Robust won't supply these voltages because the power limit will kick in. I've tried 2.2 ohm cartos on my Robust and they are a bit too weak. They need a little more voltage than the 4.5V being supplied. However at 2.0 ohm it works great. Also, dual coil is a bad idea. 9W is barely enough for one coil, splitting it between two coils won't work.

Now I'm not saying the Robust is a bad device. I love mine, it's small and lightweight yet it has a ton of features. Just keep in mind it works best with 2.0 ohm or lower, and single coil only. I use a rebuildable atomizer with a 1.8 ohm coil and it works great.

 

[LeftCoastVaper]

If it has a watt limit it also has an amp limit (like every electrical device). Ohm's Law says I=V/R, so 4.5v/2.2 ohms = 2.04 amps. That's its limit.

 

[tc1]

If it has a watt limit it also has an amp limit (like every electrical device). Ohm's Law says I=V/R, so 4.5v/2.2 ohms = 2.04 amps. That's its limit.

Which is why I only gave it a quick look. Love the size ... hate the amp limitation.

 

[Sinister Dexter]

An amp limit is not what is holding it back in these measurements:
3.7V / 1.5 ohm = 2.5A
4.5V / 2.2 ohm = 2.0A
5.2V / 3.0 ohm = 1.7A

Notice the amp measurements are all different. If an amp limit was kicking in, all three would be the same. Obviously it does not have a 2 amp limit because at 1.5 ohm you get 2.5 A. The power always maxes out at 9.1W so it is a watt limit, not an amp limit.

If it was an amp limit, you would want to use a high resistance load, to get more power from the limited current available. P = I^2 * R, so for a particular current, increasing resistance gives you more power. But it's not an amp limit, so this doesn't work! You need low resistance devices instead.

 

[Rader2146]

It's fairly safe to say that it is not hitting any "designed" limiting parameters, whether it be amps or watts. It is a side effect of the size. Small device, small components, small capability. It certainly doesn't help that the battery is only a 14500 that is being but through the strain of a boost circuit. If the battery is only capable of producing "X" watts, then output is only going to be "X - (efficiency loss)" watts.

Small battery mods like this would really benifit from a pulsed output. A pulsed output would boost battery life and max output power. But then everyone would complain about it not being "accurate"

*IF* there is a designed amp limitation that is holding back the output power, it is on the input side of the circuit and probably around 3amps.

 

[tc1]

I know PB did a load test on the Robust in his youtube review. Had plenty of limitation and he couldn't get it to regulate voltage like it says it should. The batteries on these smaller devices just aren't up to snuff to do what the bigger mods succeed at.

 

[Sinister Dexter]

Yea, PB's review is where I got my numbers from. I don't have one of those screw-on voltmeters.

I suspect the weak link in the circuit is the input (battery side) of the buck/boost converter. If there is an amp limit coming into the converter, that would get converted to a watt limit on the output. Or thinking of it in the other direction, 9.1W of power on the load translates into 2.2A current coming out of the battery, no matter what your voltage is set to.

 

[tc1]

Honestly ... I'm not sure there is a way to get the right amount of power out of these smaller batteries without going to LiPo chemistry. And of course, if you move to LiPo you're dealing with a more volatile battery chemistry which is less immune to abuse.

 

[Izan]

My pappy always said "if it ain't an 18, it's for toys."
Size Matters!!!

I

 

[Sinister Dexter]

Yea the Robust certainly has serious limitations. Personally I think the problem is with the conversion circuit, not with the battery, but I'm only speculating, it could very well be the battery.

However, if you understand the limitations, you can work around them. PBusardo revealed issues with 2.2 ohm and 3.0 ohm cartos, but the 1.5 ohm performed fine. Based on my calculations the maximum resistance you should use is 2.0 ohm, above that and the current drops too much to heat up the coil. If PB spent most of his time at 2.2 ohms I am not surprised that he was dissatisfied. I used 2.2 ohm at first and I was also dissatisfied.

If I had known the limitations earlier I probably would not have bought it. But now that I have it I am motivated to get the most out of it. I built a 1.8 ohm coil specifically to aim for its sweet spot. I run it at 4V and it performs wonderfully.

I'm not happy that I have to coddle it like this, I wish I could just screw anything on there. But now that I have a better understanding of how the device works I just want to share that information, so everyone else can make the most of their Robust too.

 

[tc1]

Oh absolutely. Every device has down falls and limits for what you can do. Doesn't mean you can't enjoy a great vaping experience out of it (and at the end of the day, that's all that matters). You just have to understand the limitations and adjust accordingly.

That is why you won't see me hating on a device. Different strokes for different folks and frankly I think it's rather rude to tell someone what they use and/or enjoy is junk. No different than walking up to someone and telling them the car they just parked is junk ... or the clothes they are wearing look bad.

Doesn't mean I won't form my own opinion on a specific product. It just means I'm polite to those who may see it differently and don't feel a need to bash them for it.

 

[Baditude]

I wanted a out-and-about VV mod to use instead of my full size Provari. I wasn't prepared to put out another $200 + batteries for the Mini, although that's really what I wanted. I started looking into VV devices that were small, light in weight, stealth-like, and could provide a decent vape.

I looked into the eGo VV 14500: too long. I looked at the Robust: PBusardo video disappointed. Finally decided to spend the same $50 on a Smoktech VV Gripper. It meets all of the criteria I wanted. The nice LED display and 18650 battery are both pluses. If Smoktech only made these out of something more durable than shatter-resistant plastic... Anyway, PBusardo gave it a thumbs up, and so do I. It hits harder than the user set voltage, but I knew that when I ordered it and adjust accordingly. Very happy thus far.

 

[Izan]

Yea the Robust certainly has serious limitations. Personally I think the problem is with the conversion circuit, not with the battery, but I'm only speculating, it could very well be the battery.

However, if you understand the limitations, you can work around them. PBusardo revealed issues with 2.2 ohm and 3.0 ohm cartos, but the 1.5 ohm performed fine. Based on my calculations the maximum resistance you should use is 2.0 ohm, above that and the current drops too much to heat up the coil. If PB spent most of his time at 2.2 ohms I am not surprised that he was dissatisfied. I used 2.2 ohm at first and I was also dissatisfied.

If I had known the limitations earlier I probably would not have bought it. But now that I have it I am motivated to get the most out of it. I built a 1.8 ohm coil specifically to aim for its sweet spot. I run it at 4V and it performs wonderfully.

I'm not happy that I have to coddle it like this, I wish I could just screw anything on there. But now that I have a better understanding of how the device works I just want to share that information, so everyone else can make the most of their Robust too.

So, to make the most of the VV robust , only use a 1.8ohm coil at 4 Volts. Got it.

 

[tc1]

I wanted a out-and-about VV mod to use instead of my full size Provari. I wasn't prepared to put out another $200 + batteries for the Mini, although that's really what I wanted. I started looking into VV devices that were small, light in weight, stealth-like, and could provide a decent vape.

I looked into the eGo VV 14500: too long. I looked at the Robust: PBusardo video disappointed. Finally decided to spend the same $50 on a Smoktech VV Gripper. It meets all of the criteria I wanted. The nice LED display and 18650 battery are both pluses. If Smoktech only made these out of something more durable than shatter-resistant plastic... Anyway, PBusardo gave it a thumbs up, and so do I. It hits harder than the user set voltage, but I knew that when I ordered it and adjust accordingly. Very happy thus far.

View attachment 157593

Yeah, I came close to getting the Gripper ... love the screen, grip design, and battery life. The plastic and "higher than advertised" voltage is what eventually led me to hault. Might still pick one up if they ever have a good sale on them. Nice thing about that design is that if the casing DOES end up cracking ... you can easily put the innards into a tin and have yourself an altoid mod or whatever.

Someone should come out with metal or harder plastic casing for the gripper ... that would be sweet.

 

[TomCatt]

Oh absolutely. Every device has down falls and limits for what you can do. Doesn't mean you can't enjoy a great vaping experience out of it (and at the end of the day, that's all that matters). You just have to understand the limitations and adjust accordingly.

That is why you won't see me hating on a device. Different strokes for different folks and frankly I think it's rather rude to tell someone what they use and/or enjoy is junk. No different than walking up to someone and telling them the car they just parked is junk ... or the clothes they are wearing look bad.

Doesn't mean I won't form my own opinion on a specific product. It just means I'm polite to those who may see it differently and don't feel a need to bash them for it.

I'm liking my Robust. And seeing as how my all-day-vape DIY peppermint tastes best at around 6-7 watts; works perfect for me.

I haven't tested the unit for voltage-under-load (guess I'll do that tomorrow); but if it is a battery limitation, then IMRs should take care of that. ICR (LiCo - 'typical' li-ion battery chemistry) is typically rated at 2C; IMR (LiMn - 'high-drain' chemistry) I've seen listed as 8C. So a 600mAh 14500 LiMn battery should be able to deliver 4.8A.

 

[TomCatt]

Simple Voltage Testing of the L-Rider Robust with EH IMR 600mAh Battery at 4.0V

Setting	Unloaded Volts	2.2 ohm Loaded Volts	Watts	Current
3.7	3.70	3.68	6.2	1.7
4.0	4.01	3.99	7.2	1.8
4.5	4.53	4.35	8.6	2.0
5.0	5.01	4.44	9.0	2.0
5.5	5.51	4.44	9.0	2.0
		2.3 ohm Loaded Volts
5.5	5.51	4.60	9.2	2.0
		3.1 ohm Loaded Volts
3.7		3.66	4.3	1.2
4.0		3.86	4.8	1.2
4.5		4.40	6.2	1.4
5.0		4.94	7.9	1.6
5.5		5.03	8.2	1.6
6.0		5.03	8.2	1.6