Lets talk about NiMh... Stop all the hating.

[bapgood]

I agree with WattWick.

I can charge and balance Nano-Tech series lipo packs in ~15 minutes at a 5C rate. I typically don't, but that's not the point.

Things have changed considerably in the last 10 years for lithium batteries.

 

[cmacclel]

Think we might be comparing apples to oranges.

Not sure what a standard lithium cell is, but I'm thinking they're not lithium ion polymer? If you really want, I can cycle a lipo a couple times and post the data so you can figure if it's fully charged in 15 minutes or less. Just a friendly offer if you're curious. You have me questioning my beliefs anyway They do come out at 4.208v, to be exact. That I know.

Don't think any of the chemistries we use qualify as standard either. At least I had never heard of IMR batteries before vaping. On the other hand, I had never heard of anyone charging NiMHs in 15 minutes either.

By "standard" I mean cells you or anyone can purchase easily not "new" specialty cells. Nimh cells can be charged in 15 minutes but will not last as long as cells charged at 1c (1x rated capacity).

Even if you charge an AW IMR 18650 2000mah cell from empty to full at the maximum charge rate of 4.5a your looking at 27 minutes if you calculate the numbers. But since you cannot go above 4.2v when charging any lithium cell the charging time takes much longer. I would be interested in the numbers you get in charging time. I will run my own today.

 

[cmacclel]

I agree with WattWick.

I can charge and balance Nano-Tech series lipo packs in ~15 minutes at a 5C rate. I typically don't, but that's not the point.

Things have changed considerably in the last 10 years for lithium batteries.

I didn't realize we are talking about Li-Polymer cells here since 99% of mods don't use this cell.

 

[bapgood]

I didn't realize we are talking about Li-Polymer cells here since 99% of mods don't use this cell.

You stated lithium batteries. I think myself and WattWick took that as you were inferring that all lithium battery types took X amount of time to charge, which is not the case.

That is why a proper understanding of the batteries/charging/etc a person uses is critical. There is a plethora of 18650 variations out there with greatly different specifications, even in the high drain 2000mah 18650 category different manufactures have different specifications.

 

[WattWick]

I didn't realize we are talking about Li-Polymer cells here since 99% of mods don't use this cell.

Sorry about that! My main point was, as bapgood says, to clarify that there's several lithium chemistries, and that the OPs comparison might be off.... or am I just threading water again.

Edit: Should probably add that I'm currently wearing a donkey hat and sitting in a corner to repent for my claims that "any lithium cell can be charged in less than an hour".

 

[Lastlokean]

Back on topic.... NiMh.

Just did some quick testing... With any of the battery contact springs I can find at radioshack or flashlights the best I can find is ~.072 ohms and the worst I have found is ~.112 ohms. This is after testing ~50 different contacts. Also within identical springs from the same source there is huge variance.

At 2 amps each spring is between .14 and .224 volt drop.

Really helps explain why 3xaa/aaa in a cheap case suffers so bad. They have 3 springs in the case itself and 2 more springs to hold it in place. Giving a total of 5 springs. That is between .7 and 1.12 voltage drop!

^ Really helps explain why so many have thought AA/AAA don't work.

In my personal 3xaaa battery I soldered them together with copper wire. I charge the pack with my lab bench supply to provide 3.75 volts. Honestly the performance is amazing and lasts all day.

 

[bapgood]

Sorry about that! My main point was, as bapgood says, to clarify that there's several lithium chemistries, and that the OPs comparison might be off.... or am I just threading water again.

IMHO your dead on. As has been stated there are several factors to consider when comparing batteries.

A person should use whatever they find works the best for them in their comfort range.

 

[bapgood]

Lastlokean - I'm curious how many charge cycles you get out of your soldered NiMh packs?

BTW - I didn't think we were off topic, your original post was a direct comparison to lithium batteries.

 

[Lastlokean]

I have only been using them for about 2 weeks... So that is to be determined!

The biggest down side to NiMh is that using 3/4 of them in series really brings out the issues of mechanical resistance.

The puck uses 4xAA to theoretically output 4.8volts... I would guess that they are only delivering 3.6 volts maximum under load. It should be possible to deliver ~3.6 volts using just 3 batteries. We just need to get the total series resistance under .05 ohms.

 

[dr g]

I didn't realize we are talking about Li-Polymer cells here since 99% of mods don't use this cell.

FWIW lipo seems to be a fairly common solution in this subforum, we are cramming mods into all kinds of containers and lipo is a cheap and powerful option.

 

[dr g]

In my personal 3xaaa battery I soldered them together with copper wire. I charge the pack with my lab bench supply to provide 3.75 volts. Honestly the performance is amazing and lasts all day.

"Lasts all day" is not really a measure, every vaper's day is a different level of use. 2A is a relatively undemanding draw and many if not most high-capacity 18650 cells can handle that in excess of 2300mah, which is FAR beyond even the nameplate rating of AAA NiMHs.

When you speak of high amp delivery for ecigs you're looking at 5+ amps. How do 3x NiMHs fare under those loads?

 

[WattWick]

I digress, but how about NiZN batteries? In theory, those seem superior to NiMH cells. I do realize this negates the point of "readily available".

Never heard of such a thing until a couple days ago when I stumbled across them.

Nominal voltage 1.6v, 50% more energy density than NiMH. ... or that's what the ad says Any experience? Couldn't find anything conclusive by searching these boards.

 

[rolf]

right on !
that's why I am making my own ...different neg conector ..also tried using desoldering braid to bypass the spring it makes a big difference in my pug ...4 aa set up .right now building a battery pack from scratch ...fiberglass lay up.and will write about it later.
what is so amazing is that well known manufacturers tout the safty about the high resistence spring .my commercial batt pack even gets hot in the bottom !! and I don't need a hand warmer . will bypass the spring with a pt fuse soon to try. engeneering ? common sense ?>

 

[Nikkel]

I am intrigued by the 2/3A size NiMH batteries.
On paper, they look good.
1600mAh, max 10C.
Discussion here:
http://www.e-cigarette-forum.com/fo...tacked-batteries-amp-rating.html#post11634031

 

[dr g]

See post #11