Charging Lipo Batteries

[rockthemonkees]

AARGH.. please welcome me to the world of Brushless and LIPO batteries after a 20 yr gap

The

IMax b6 LIPO Charger arrived today, and i have read although not totally digested the instructions yet..

I have a 7.4 2s 4000 battery to charge, can i damage it if i get the setting wrong?

do u need the extra small lead connected and why and what charge rate should i use

is the auto setting safe

sorry for the nerdie questions, but new to all this lipo lark

[Chain Driven]

I'm getting back into it as well so interested in the answer from the Pros.

Also do you need to balance charge them every time?

[rockthemonkees]

Hey Jerome, u too man excellent, one of these days we will meet up..

I am on two wheels now, bored with Optimas extra so currently restoring a Kyosho HOR !!

just finished 2nd coat of white and 1st coar met blue, most hopup parts have arrived, just wating on a few bits

then its buildtime/

these lipos should be straightforward but i need to be certain i am not gonna blow it up !!

[bromvw]

Hey Jerome, u too man excellent, one of these days we will meet up..

I am on two wheels now, bored with Optimas extra so currently restoring a Kyosho HOR !!

just finished 2nd coat of white and 1st coar met blue, most hopup parts have arrived, just wating on a few bits

then its buildtime/

these lipos should be straightforward but i need to be certain i am not gonna blow it up !!

for safety use a steel box ie a old ammo box to chage the lipo in . That way IF it sets on fire your safe . I'am no expert but as i understand it you have to balance charge lipos . i'd re read the manual before i did anything . These lipos can be dangerous if not handled correctly .

[Chain Driven]

for safety use a steel box ie a old ammo box to chage the lipo in . That way IF it sets on fire your safe . I'am no expert but as i understand it you have to balance charge lipos . i'd re read the manual before i did anything . These lipos can be dangerous if not handled correctly .

Thanks Mate, also another thing I heard about without undestanding, ESC needs to be LiPo friendly?

Is it a cut off to prevent LiPos from getting to low? Do they suffer if completely discharged?

J.

[bromvw]

Thanks Mate, also another thing I heard about without undestanding, ESC needs to be LiPo friendly?

Is it a cut off to prevent LiPos from getting to low? Do they suffer if completely discharged?

J.

this might help

http://www.rcmods.co.uk/lipo_battery_safety_tips.php

[Chain Driven]

AARGH.. please welcome me to the world of Brushless and LIPO batteries after a 20 yr gap

The

IMax b6 LIPO Charger arrived today, and i have read although not totally digested the instructions yet..

I have a 7.4 2s 4000 battery to charge, can i damage it if i get the setting wrong?

do u need the extra small lead connected and why and what charge rate should i use

is the auto setting safe

sorry for the nerdie questions, but new to all this lipo lark

Sorry, I've hacked your topic my friend.

[bromvw]

Thanks Mate, also another thing I heard about without undestanding, ESC needs to be LiPo friendly?

Is it a cut off to prevent LiPos from getting to low? Do they suffer if completely discharged?

J.

the minimum safe voltage is 2.7 volts per cell , therefore on 2s its 5.4 volts . You need a ESC with low voltage cut off and need to set it to a minimum of 6 volts to allow a safety margin . Most ESC have cut off's built in but if not you can buy them cheaply on e bay ect or a lipo alarm that sounds when the perset voltage is reached . A cut off is the safer option . To get the best out of lipos i'd buy a bottom end brushless combo ie motor and esc . For the price of a decent brushed motor you get both and its future proof

[rockthemonkees]

no u havent, keep em coming,

ok so what is the little lead with the white plug used for?

[Chain Driven]

no u havent, keep em coming,

ok so what is the little lead with the white plug used for?

Case of blind leading the blind there , but I think it's what I refered to earlier as balance charging, allows the charger to check that both cells are charged to the same level. But please correct me if I'm wrong Guys.

[bromvw]

no u havent, keep em coming,

ok so what is the little lead with the white plug used for?

thats the balance lead.

[rockthemonkees]

ok if i see it right i f plug into my fully automated lipo charger and set for 2 cells it will do it automatically, anything i should watch out for?

[speedy_w_beans]

A few thoughts on LiPos:

- You do need an ESC with LiPo cutoff (or an external cutoff on an older ESC); most ESCs with this feature will shut down once the pack voltage hits ~6.2 V. If the voltage goes any lower than that there is a risk of damaging the battery.

- It's a good idea to use a Deans plug or similar on both the battery and ESC due to the high peak currents with high kV / low turn motors. Tamiya / Molex plugs can get warm and melt if the connection isn't perfect due to wear and tear.

- The small white plug is a balancing connection; this should always be used. The charger uses the balancing connection to make sure both cells inside the pack are charged to the same voltage. If you don't balance charge the pack, then one cell could discharge before the other, damaging the cell. EDIT: Or you could also overcharge one cell relative to the other, introducing a serious safety risk.

- A good charge rate for a battery is 1C, or 1x the mAh rating of the pack. A 4000 mAh battery can be charged at 4 A.

- There are really three charge states to be aware of: 1) discharged at the 6.2V cutoff after a drive, 2) fully charged at 8.4V after a charge, and 3) a storage charge of ~7.4-7.6V. The purpose of the storage charge is minimize battery capacity degradation if you plan to store the pack for a long period of time without using it.

- As mentioned, an ammo box or a LiPo charging sack is a must for safety sake.

- Never charge unattended for any battery chemistry.

-Paul

[bromvw]

A few thoughts on LiPos:

- You do need an ESC with LiPo cutoff (or an external cutoff on an older ESC); most ESCs with this feature will shut down once the pack voltage hits ~6.2 V. If the voltage goes any lower than that there is a risk of damaging the battery.

- It's a good idea to use a Deans plug or similar on both the battery and ESC due to the high peak currents with high kV / low turn motors. Tamiya / Molex plugs can get warm and melt if the connection isn't perfect due to wear and tear.

- The small white plug is a balancing connection; this should always be used. The charger uses the balancing connection to make sure both cells inside the pack are charged to the same voltage. If you don't balance charge the pack, then one cell could discharge before the other, damaging the cell.

- A good charge rate for a battery is 1C, or 1x the mAh rating of the pack. A 4000 mAh battery can be charged at 4 A.

- There are really three charge states to be aware of: 1) discharged at the 6.2V cutoff after a drive, 2) fully charged at 8.4V after a charge, and 3) a storage charge of ~7.4-7.6V. The purpose of the storage charge is minimize battery capacity degradation if you plan to store the pack for a long period of time without using it.

- As mentioned, an ammo box or a LiPo charging sack is a must for safety sake.

- Never charge unattended for any battery chemistry.

-Paul

cheers paul that explained a lot better than i did .

[rockthemonkees]

lipo sack ordered!!

[Chain Driven]

lipo sack ordered!!

X2 !

[speedy_w_beans]

A few more thoughts:

- It can take LiPos up to a dozen cycles to reach their full capacity; then they will be relatively consistent for hundreds of cycles after that.

- If a charger supports multiple chemistry types (NiCD, NiMH, LiFE, LiPo, etc.) be extra careful to select the right chemistry; the charging algorithms are different depending on chemistry (constant current/peak voltage, constant current/constant voltage, etc.).

- Soft-case LiPos are more vulnerable to damage than hard-case LiPos; any sort of physical damage to a LiPo battery pack should be evaluated in terms of safety risk.

In terms of performance, a 2S LiPo feels like a 7-cell NiMH. The LiPo pack voltage is lower, but the internal resistance is also lower, so the voltage doesn't sag as badly under load.

-Paul

[Chain Driven]

A few more thoughts:

- It can take LiPos up to a dozen cycles to reach their full capacity; then they will be relatively consistent for hundreds of cycles after that.

- If a charger supports multiple chemistry types (NiCD, NiMH, LiFE, LiPo, etc.) be extra careful to select the right chemistry; the charging algorithms are different depending on chemistry (constant current/peak voltage, constant current/constant voltage, etc.).

- Soft-case LiPos are more vulnerable to damage than hard-case LiPos; any sort of physical damage to a LiPo battery pack should be evaluated in terms of safety risk.

In terms of performance, a 2S LiPo feels like a 7-cell NiMH. The LiPo pack voltage is lower, but the internal resistance is also lower, so the voltage doesn't sag as badly under load.

-Paul

Thanks Paul, great factual answers !

J.

[rockthemonkees]

thanks paul, so in case of performance

a stock 540 compared to a 2s 25c 4000 7.4 lipo and a 5700kv motor,what should i expect to see in differences in performance?

[94eg!]

thanks paul, so in case of performance

a stock 540 compared to a 2s 25c 4000 7.4 lipo and a 5700kv motor,what should i expect to see in differences in performance?

~200-250% more rpm (top speed) and a lot more torque as well. Just keep an eye during the first few runs that the motor and/or ESC aren't getting too hot. If you can hold your thumb on them for 5 seconds, your good. If it's only 3 seconds, your about at the limit. Anything less and your overheating so shut it down.

Does your ESC have a lipo low-voltage-cutoff?

[rockthemonkees]

yes it does have a auto cut out. so with that much more performance my gearbox may get fryed !!

one question though if it does over heat, will it damage or shut down before it melts?

and why would it overheat in the first place? because of mismatched motors maybe?

[94eg!]

yes it does have a auto cut out. so with that much more performance my gearbox may get fryed !!

one question though if it does over heat, will it damage or shut down before it melts?

and why would it overheat in the first place? because of mismatched motors maybe?

Gearbox will be fine. Just roll onto the throttle if your concerned. The torque/shock is greatest at zero rpm and when landing jumps at full throttle. Of course I'm not sure if you mentioned what vehicle this will be going into.

Heat is a byproduct of improper gearing for a specific setup and/or driving conditions. Whenever you change your motor or gearing setup, ALWAYS keep an eye on heat throughout the first run or two. You will be pretty bummed if you kill a brand new ESC or Brushless motor. The ESC will shut off if it gets too hot, but the motor has no way of defending itself. The rotor magnet will become permanently weak if it gets too hot. If you don't know much about gearing, here is your crash course:

- Smaller pinion = more torque, less top-speed and less heat

- Bigger pinion = less torque, more top-speed and more heat

Just stop occasionally durring your run and stick your thumb on the motor and ESC. If you find it getting too hot in the middle of your run, you will NEED a smaller pinion. If you can hold your thumb on the motor can all day long, then you might consider getting a larger pinion for a little more speed. Of course there is nothing wrong with running cool either.

[chevyman3]

That charger did come with the white balance cord with the white plugs on it correct. you use that as well when you are charging, it will balance charge. you should have both battery plugs hooked to the charger when charging or discharging, that charger also does storage mode witch you want to do when you will not be using your packs like a couple weeks or more. The main thing to keep in mind is OVER discharging is the lipos worse enemy and will damage it.

[speedy_w_beans]

With respect to picking the right pinion gear for a brushless motor system, this is the best tool you can have:

http://www.harborfreight.com/non-contact-p...eter-93983.html

Check the ESC and motor temperatures every five minutes initially. If you can keep the ESC's heatsink temperature and the motor's case temperature below 150F / 65C, then you're generally ok. If the temperatures start to go over 160F, the risk of demagnetizing the neodymium rotor starts to go up.

As the seasons change you may want to revisit the temperature readings again. The temperatures might look safe in the winter, but then they might be too hot in the summer.

-Paul