Vamo v3 on NiMH

[Giant Squid]

I attempted to build the mod shown here:
http://www.e-cigarette-forum.com/fo...5-vamo-pcb-nimh-batteries-2.html#post10287866

My attempt used a v3 PCB.

There's no startup LED flash on the v3, so current draw is lower and it's not so easy to fool it into thinking it's on a single lithium cell with a dropper resistor. I use a LD1117 3.3V regulator instead, and then jumper it out of the circuit once it's ready. It sees the full 5.4V of the freshly charged cells, but there must be an additional high voltage check because it errors with "HHHHHHHH" on screen when I try to fire.

I can't leave the regulator in because it's only rated for 0.8A. I tried it anyway and it errored with "Short" on a 2.2ohm coil.

It works fine with 3xNiMH cells, but that's annoying because the 3.2V cutoff will mean I can't fully discharge them and I prefer using even numbers of cells where possible. The ideal solution would be to hack the firmware somehow to set custom high/low voltage cutoffs.

 

[pianman6954]

Have you considered using a different regulator? madvapes has LDO regulators I think up to 5A, a variable regulator could let you dial in 4.2 volts. I tried something similar with the lm317 but the DO of that thing is nearly 2V above the reference voltage. As much as it sucks 3 cells isn't too terrible for NiMh as they have a very flat discharge curve and are pretty much done at less than 1.2V per cell. Your bigger challenge may be the higher internal resistance causing parasitic loss. Been trying to get my hands on one of these boards will let you know if I come up with any breakthroughs.

 

[WarHawk-AVG]

I attempted to build the mod shown here:
http://www.e-cigarette-forum.com/fo...5-vamo-pcb-nimh-batteries-2.html#post10287866

My attempt used a v3 PCB.

There's no startup LED flash on the v3, so current draw is lower and it's not so easy to fool it into thinking it's on a single lithium cell with a dropper resistor. I use a LD1117 3.3V regulator instead, and then jumper it out of the circuit once it's ready. It sees the full 5.4V of the freshly charged cells, but there must be an additional high voltage check because it errors with "HHHHHHHH" on screen when I try to fire.

I can't leave the regulator in because it's only rated for 0.8A. I tried it anyway and it errored with "Short" on a 2.2ohm coil.

It works fine with 3xNiMH cells, but that's annoying because the 3.2V cutoff will mean I can't fully discharge them and I prefer using even numbers of cells where possible. The ideal solution would be to hack the firmware somehow to set custom high/low voltage cutoffs.

question for OP

Could you use a regulator like this and stack the IC regulators for 3.6vdc at 3A?
http://www.e-cigarette-forum.com/fo...8-variable-voltage-question.html#post10470964

Hope this helps

oh and subscribed

 

[Kellycat]

question for OP

Could you use a regulator like this and stack the IC regulators for 3.6vdc at 3A?
http://www.e-cigarette-forum.com/fo...8-variable-voltage-question.html#post10470964

Hope this helps

Stacking regulators isn't generally advisable, for a variety of reasons, including the fact they're not all perfectly identical, and as such won't split the load evenly as expected. I.e. you may draw one amp through one regulator, and only half an amp through the second. While that's a pretty extreme example, the same principle applies. Better off getting a single high-amp buck regulator, they're readily available on Digikey and Mouser, maybe $5-$10 for something that can suck down 6A or higher without blowing out.. I was actually looking into them the other night so I have a good idea of what's out there, can even get a 6A buck/boost chip that'll let you run 2 NiHM cells and boost the voltage to something the Vamo PCB will recognize natively. I just can't see much point of a boost circuit though, better to use four batteries and a buck converter as they're far cheaper and generally have higher amp limits.

 

[Relayer1974]

I attempted to build the mod shown here:
http://www.e-cigarette-forum.com/fo...5-vamo-pcb-nimh-batteries-2.html#post10287866

My attempt used a v3 PCB.

There's no startup LED flash on the v3, so current draw is lower and it's not so easy to fool it into thinking it's on a single lithium cell with a dropper resistor. I use a LD1117 3.3V regulator instead, and then jumper it out of the circuit once it's ready. It sees the full 5.4V of the freshly charged cells, but there must be an additional high voltage check because it errors with "HHHHHHHH" on screen when I try to fire.

I can't leave the regulator in because it's only rated for 0.8A. I tried it anyway and it errored with "Short" on a 2.2ohm coil.

It works fine with 3xNiMH cells, but that's annoying because the 3.2V cutoff will mean I can't fully discharge them and I prefer using even numbers of cells where possible. The ideal solution would be to hack the firmware somehow to set custom high/low voltage cutoffs.

Where did you get your PCB?

This may be a silly question, but does the "HHHHHHH" error happen on a legitimate low voltage condition as well as when it has 5.4V connected?

 

[Giant Squid]

Where did you get your PCB?

This may be a silly question, but does the "HHHHHHH" error happen on a legitimate low voltage condition as well as when it has 5.4V connected?

I got the PCB from StealthVape.co.uk

The low voltage error message is "Low V". This kicks in at approx 3.2V or 6.4V, depending on if it thinks it has 1 or 2 lithium cells. I assume there's a "HHHHHHHH" high voltage threshold for the 2 lithium cell setup too but I'm not going to risk damage to find out.

For now I'm running it on 3 NiMH cells. I'll look into getting a suitable buck converter.

 

[Baditude]

I'm trying to understand why one would feel the need to do this?

 

[Giant Squid]

NiMH is safer, cheaper, widely available and more tolerant of abuse. The only advantage of lithium is portability, and that's not important to me.

I already have a high quality NiMH charger and I don't want yet another charger cluttering my room so I can use lithiums.

 

[Relayer1974]

I'm trying to understand why one would feel the need to do this?

Because we can.

 

[Relayer1974]

I got the PCB from StealthVape.co.uk

The low voltage error message is "Low V". This kicks in at approx 3.2V or 6.4V, depending on if it thinks it has 1 or 2 lithium cells. I assume there's a "HHHHHHHH" high voltage threshold for the 2 lithium cell setup too but I'm not going to risk damage to find out.

For now I'm running it on 3 NiMH cells. I'll look into getting a suitable buck converter.

You could try running an OKR-T/6 in there, though it needs 1.5V above its setting as an input, so you might be cutting it close. I would get one and do some bench testing, but the price plus overseas shipping is a bit steep for me. I know the V2 can handle at least 9V from when I benched and scoped it. I barely see the logic in making a "High V" warning, but I suppose those boards are meant to be as dummy-proof as possible.

 

[Giant Squid]

I think the high voltage warning was left over from development. The meaning of "HHHHHHHH" is not obvious and it will never show up in normal use.