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m102404 · March 18th, 2009, 13:49

It's lunch time and I'm bored....so here's my brain dump on LiPo batteries. I hope it's all correct (or at least correct enough for the layman...I'm not a chemistry/electrical engineer).

LiPo's are just another part/piece of an AEG. Any part will fail if not setup and used correctly. Some will fail catastrophically, others will just quietly give out. LiPo has a bad stigma attached to it. That comes from directly from the "user base". Lots of people don't know much about "regular" batteries...but don't really care if they mis-treat them because they won't burn down their house (they may leave a nasty mess to clean up off the workbench

...but they won't burst into flames and gas you to death).

So combine the un-informed with rumours and you get a bad rap for something that works great (at least from what I've seen).

You do need to:
1. Pay attention to your batteries while they're charging. This is not hard and doesn't ruin your whole evening...but it's still more than what some people are prepared to do.
2. Take care with handling your batteries. I'm really horrid with this. ALL of my NiCad/NiMh battery wrappers are near totaled from ripping them out and shoving them in AEGs....I toss them into storage boxes, gear bags and whatever without a care in the world. From what I've gathered, LiPo packaging is soft and keeps the "bad stuff" from getting out...so I take care with mine and they're pristine (they're only 2 weeks old

....so we'll see).
3. Use a good charger, either a balancing circuit or a charger that has one in it, don't charge at more than 1C (as said, divide your mAh rating by 1000...so a 1100mAh pack's 1C rating is 1.1A)...you won't hurt anything by charging at a lower rate. I used to swear by the "dummy's" smart charger...green=good, red=charging, low setting for minis, high setting for larges...but honestly, it took about 10min to figure out my new charger and now all I do is set the capacity and battery type (2 buttons, 2-3 button pushes) and it beeps annoyingly when it's done.
4. Check your battery's voltage before a game (to make sure you didn't grab the dead one), perhaps during a break and after the game. Get into habit of topping off your LiPo before a game and it'll probably remove part of this. I bought a little display that plugs into the balancing tap to check the individual cell voltage and the total pack voltage...takes about 10sec and cost about $20 from a hobby store. Even my little LiPo will shoot several thousands of rounds without the voltage dropping anywhere close to the "flat-line" of 3v per cell....so getting through an all-day game should be a non-issue.
5. At more than 9.6v (my LiPo's are 11.1v)...I'm running a MOSFET to reduce the voltage going through the AEG switch assembly. I've fixed more than enough stuff and seen plenty of burned out switches.
6. Somewhat unlike "regular" batteries...you need to take care with the C rating of a given LiPo pack. Two packs can look the same, both be 11.1v but they'll behave dramatically different if one has a 15C rating and the other is a 25C rating. I'm not sure if the mAh rating is directly tied to the C rating....but I do know that you need a very precise and excellent setup to run a 25-30C LiPo!

7. There are two common measurements (i.e. the numbers are often displayed on the pack for dummies like me)...burst and continuous rating. A LiPo packs burst rate is quite often much higher than it's continous rating...which makes sense. A given packs C rating (i.e. 12C or 20C) can give you a good indication of how good or bad it's going to be in your AEG. My LiPo is a 11.1V 1100mAh 15C battery. Now a 9.6v 1400mAh mini (2/3A cell) battery works pretty good in it. A large 8.4v 3200mAh (sub-c) works really nice in it. So initially you'd think that "OMG...11.1V is going to shred your mechbox...". But not really. Or maybe you'd think, "So what...the 1400mAh or 3200mAh batteries have more capacity and they'll be better"...well, sort of, but not really. Then you're left with this C rating for the LiPo. 15C means that it can put out 15 x it's 1C rating (even I got that). The 1C rating of this pack is 1.1A...so this pack can put out 16.5A (probably it's burst rating...this pack doesn't have the burst/cont ratings marked on it). I suspect that my motor and setup can draw closer to 20A...so even with a scary LiPo (oooh, ahhh) and 11.1v (oh no!)...it performs about the same as the 9.6v 1400mAh mini or a freshly charged 8.4v 3200mAh large battery (give or take 10rpm). I'm pretty sure the 9.6V large nicad get's the mechbox going faster than with the LiPo...it's in a different AEG and I haven't tried it.

But...hook up a 11.1v 2200 25C LiPo to the same setup....and the ROF hits the roof and you have to do a full reset of your Trigger Master MOSFET

(which got confused switching between such different batteries, but survived and ran like a champ after a complete reset).

Anyways...lunch it over, got to go.

Tys

March 18th, 2009, 13:49	#13
m102404 Tys Trader rating Join Date: Apr 2006 Location: Toronto	It's lunch time and I'm bored....so here's my brain dump on LiPo batteries. I hope it's all correct (or at least correct enough for the layman...I'm not a chemistry/electrical engineer). LiPo's are just another part/piece of an AEG. Any part will fail if not setup and used correctly. Some will fail catastrophically, others will just quietly give out. LiPo has a bad stigma attached to it. That comes from directly from the "user base". Lots of people don't know much about "regular" batteries...but don't really care if they mis-treat them because they won't burn down their house (they may leave a nasty mess to clean up off the workbench ...but they won't burst into flames and gas you to death). So combine the un-informed with rumours and you get a bad rap for something that works great (at least from what I've seen). You do need to: 1. Pay attention to your batteries while they're charging. This is not hard and doesn't ruin your whole evening...but it's still more than what some people are prepared to do. 2. Take care with handling your batteries. I'm really horrid with this. ALL of my NiCad/NiMh battery wrappers are near totaled from ripping them out and shoving them in AEGs....I toss them into storage boxes, gear bags and whatever without a care in the world. From what I've gathered, LiPo packaging is soft and keeps the "bad stuff" from getting out...so I take care with mine and they're pristine (they're only 2 weeks old ....so we'll see). 3. Use a good charger, either a balancing circuit or a charger that has one in it, don't charge at more than 1C (as said, divide your mAh rating by 1000...so a 1100mAh pack's 1C rating is 1.1A)...you won't hurt anything by charging at a lower rate. I used to swear by the "dummy's" smart charger...green=good, red=charging, low setting for minis, high setting for larges...but honestly, it took about 10min to figure out my new charger and now all I do is set the capacity and battery type (2 buttons, 2-3 button pushes) and it beeps annoyingly when it's done. 4. Check your battery's voltage before a game (to make sure you didn't grab the dead one), perhaps during a break and after the game. Get into habit of topping off your LiPo before a game and it'll probably remove part of this. I bought a little display that plugs into the balancing tap to check the individual cell voltage and the total pack voltage...takes about 10sec and cost about $20 from a hobby store. Even my little LiPo will shoot several thousands of rounds without the voltage dropping anywhere close to the "flat-line" of 3v per cell....so getting through an all-day game should be a non-issue. 5. At more than 9.6v (my LiPo's are 11.1v)...I'm running a MOSFET to reduce the voltage going through the AEG switch assembly. I've fixed more than enough stuff and seen plenty of burned out switches. 6. Somewhat unlike "regular" batteries...you need to take care with the C rating of a given LiPo pack. Two packs can look the same, both be 11.1v but they'll behave dramatically different if one has a 15C rating and the other is a 25C rating. I'm not sure if the mAh rating is directly tied to the C rating....but I do know that you need a very precise and excellent setup to run a 25-30C LiPo! 7. There are two common measurements (i.e. the numbers are often displayed on the pack for dummies like me)...burst and continuous rating. A LiPo packs burst rate is quite often much higher than it's continous rating...which makes sense. A given packs C rating (i.e. 12C or 20C) can give you a good indication of how good or bad it's going to be in your AEG. My LiPo is a 11.1V 1100mAh 15C battery. Now a 9.6v 1400mAh mini (2/3A cell) battery works pretty good in it. A large 8.4v 3200mAh (sub-c) works really nice in it. So initially you'd think that "OMG...11.1V is going to shred your mechbox...". But not really. Or maybe you'd think, "So what...the 1400mAh or 3200mAh batteries have more capacity and they'll be better"...well, sort of, but not really. Then you're left with this C rating for the LiPo. 15C means that it can put out 15 x it's 1C rating (even I got that). The 1C rating of this pack is 1.1A...so this pack can put out 16.5A (probably it's burst rating...this pack doesn't have the burst/cont ratings marked on it). I suspect that my motor and setup can draw closer to 20A...so even with a scary LiPo (oooh, ahhh) and 11.1v (oh no!)...it performs about the same as the 9.6v 1400mAh mini or a freshly charged 8.4v 3200mAh large battery (give or take 10rpm). I'm pretty sure the 9.6V large nicad get's the mechbox going faster than with the LiPo...it's in a different AEG and I haven't tried it. But...hook up a 11.1v 2200 25C LiPo to the same setup....and the ROF hits the roof and you have to do a full reset of your Trigger Master MOSFET (which got confused switching between such different batteries, but survived and ran like a champ after a complete reset). Anyways...lunch it over, got to go. Tys Last edited by m102404; March 18th, 2009 at 13:55..