So I finished my 5Vbox and I'm shopping for batteries. It takes two 14500s. What I want to know is whether it is worth investing in high drain batteries in a regulated circuit or am I just better off going for capacity? Cheers
If you are using a voltage regulator, go for capacity. At 5 volts you'll most likely be using std or high resistance so the high drain are not much of a benefit.
I know some disagree but I think you are better off paying a bit extra for the Black AW protected batteries versus the trustfire protected batteries. in terms of performance, reliability, durability
I would be going protected personally as the box has no battery management and the cells are in series, so one cell could run below dangerous levels and the box would still work (though poorly). This is the dangerous form of operation where excessive heat can be generated. Also to protect against a rarish occurrence but I have seen it happen, the regulator could go short circuit. but .. you would need some decent protected cells though, I assume a 3A output current and 14500 being what 900mAh, means a 4C discharge current. I couldn't tell you what the norm is for 14500, whether a different protection than the 18650 is used. That being the case .. IMR's are a safer type of chemistry and far more likely to just get hot than go into thermal runaway, so it may well be safer to use IMR than normals .. so my route would be to look into high discharge protected, then IMR then normal cells with a large dose of .comtion. If using IMR you need to change cells out before either hit the 2.8V mark as they could be damaged.
Well there is no simple answer .. its a personal risk decision based largely on how often you will charge and your build quality and component choices. Can't make it any clearer than .. high discharge protected, then IMR then normal cells with a large dose of .comtion. If you can mamage to recharge before the 2 cells hits about 6.4v then normal ones will do, if nothing else fails..
go cheap batterries and have your gf/wife/partner try them out when one battery is much lower discharged than the other. That way you have saved money and if the thing blows you will be ok. Win Win
Sorry Stoney. I didn't mean to be unappreciative. I do appreciate the input and undertstand why you have recommended the high drain protected first. Would you say that all ecig mods using batteries in series suffer from this problem or is it simply be.comse I'm regulating the voltage output?
any series battery system suffers from the problem unless a BMS (battery management system) is installed, this monitors the voltage on each cell and charges each cell accordingly, thats what a balance charger does in RC terms, more exxy things like electric cars and pushbikes have the chips mounted inside the packs. You are charging cells individually so thats all fine, but what if one is 900mAh and the other is degraded an only 500mAh .. it runs out of charge first, at this point the current is forced through it by the other cell and ultimately in nicad packs it actually ends up with a negative terminal voltage. In a Lithium system at 2.2V or so it will start generating a lot of heat at his point, if it makes enough heat it gets into a thermal runaway situation and can vent flames. protected cells stop this by shutting off at low voltage, IMR stop this mostly by the thermal runaway situation is removed, you can also eliminate it by ensuring a regular charge with normal cells .. probably needs a battery voltage readout, preferably under load. NiMh packs usually only have 1 or 2 cells fail due to being overdischarged, they are fairly tolerant though so no BMS is usually in place, they balance charge by overcharging, not an option with lithium.
So you have piqued my interest with the comments about battery protection. Could you elaborate as to how you build this into a mod? I took a look at RS components earlier and found some protection chips but beyond that I'm lost.
I'm still learning about batteries, the pros and cons of the various types and features... so this is all very interesting to read about. Thinking about a tube type mod in the near future. I was looking at the 4.8V NiMH on madvapes recently and wondering how well they'd do. I like the idea of 5V without stacking. What I'd really like to find out is how to make an.comto switch, seems to be limited info on that in the various forums!
4.8V NiMh is stacked .. 4 cells, even worse than usual as you can't independently charge them .. lifespan is not good from other posts on this forum about them, death within a few days/weeks. Since they are small cells they are being pushed to the limit at best, as soon as one gets lower than the others a rapid death (safe) will result and throw it away.
soz missed this earlier .. easy way is to buy protected cells. Other than that .. in a dual mod you would need to monitor the voltage of the individual cells and have a MOSFET cut off the atty current when either cell drops below the dangerous nogo zone, that seems to vary with the manufacturer, there are some (specially made) that can go down to 1.6V apparently, in general it would be 3.2V per cell though to be pretty safe. After that the cell is permanently damaged. I can attest to that having killed 2 cells with a slow discharge earlier this week, they where down to 0.8V .. neither will accept charge now, put them on a 4.2V supply and they draw 0 current.
Having nearly blown my face off (there is a picture somewhere) trying to charge batteries I would go for the protected ones.
A protection circuit...... http://www.ebay.com.com/itm/Protect...y-Pack-7-4V-8-4V-/220739355125#ht_2316wt_1037
nice one jonny, I would reckon that a bit of research on the chips involved would turn up a logic input that with a PWM signal applied might make for a nice safe and simple VV mod.
Just ordered 3 if you want one stoney. The 2 D2107s on the left of the pic are dual N ch mosfets with common drain and 23 mohm on-resistance. Cant see the p/n on the controller chip but I'm sure we could figure out how to pwm them.
heh, yeh i ordered 4 earlier jonny, yep .. FTD2017R .. data from http://pdf1.alldatasheet.com/datasheet-pdf/view/199796/SANYO/FTD2017R.html had a quick peruse this morning
