Jump to content
Oblivious

Another dumb doubt by Oblivious: Lipo storage and the iMax B6.

Recommended Posts

Hi TC.

Just received the iMax B6 charger/discharger and two Venom 2S 4000mAh Lipo batteries --> To be honest quite dissapointed: ultra fast ship (normal being Lipos) but not really really "hard case" and payed 30€ on "hello-surprise-taxes"!! :angry:

Anyway. The issue is that I wanted to put both of them trough this "storage control program" of the charger (to be sure they´re ok until I can fully charge them for use). On that program I can select the batt type (7,4v 2S in my case) but only a range from 0.1 to 1A. I´ve read that Lipos must be stored at 50% of their capacity and 1A would be 25%. From what I´ve read in the charger´s manual those 0.1-1A are for the battery pack´s current, so... Is there anyone with an iMax B6 (or with similar software) to shed some light on this point?

It may be a silly question but that´s me :).

Share this post


Link to post
Share on other sites

The rate its showing is the dicharge rate, so at 1amp it would take 4 hours to fully discharge, Same as charge rate, at 1c which would be 4amps to charge would take 1 hour to fully charge a flat battery, but as there rarely going to be flat it never seems to take very long. If your going to be using your batteries every few weeks or so i wouldn't put them in storage mode.

  • Like 1

Share this post


Link to post
Share on other sites

Just be aware that a fully charged LiPo is actually 8.4v (peak voltage). The 7.4v is the 'nominal' voltage and just so happens to also be the storage voltage. The minimum a LiPo should ever go down to safely is around 6.4v (although some people say a little lower is OK. As you can see you're working within a 2v window (6.4v - 8.4v) with 7.4v being smack bang in the middle.

If you have a multimeter just measure what voltage the packs are at now, if it's in the region of 7.4v then you don't need to touch them until you want to use them, then simply do a balance charge at 4.0A when you want to use them and you'll be set!

  • Like 1

Share this post


Link to post
Share on other sites

Thank you guys. Much clearer now. I understood from the manual that those 0.1-1A had something to do with the battery itself, not with the discharge rate but what tamiya monkey says makes much more sense to me. I just thought that the discharge rate was set on the "discharge mode" (which I´ve read is not really good to use with Lipos). I understand from what you say that the storage mode has a different discharge rate (no matter what you set for the discharge mode, which can not exceed 1C according to the manual).

Steve U30, to measure the voltage I´ll have to connect them to the charger and stop it right after reading the figures since I have no multimeter (the charger gives you the lecture for the voltage and current on real time when you use any of the charge, discharge or storage mode. I guess I´ll have to put them in storage mode for a few seconds in order to know how they are.

Thank you again for the tips.

Share this post


Link to post
Share on other sites

Yep, I did mean to say that the charger will probably tell you too. No harm in starting a charge and seeing what voltage they're at.

  • Like 1

Share this post


Link to post
Share on other sites

Remember that Lipos must never go below 3.7v per cell for longevity.

Fully charged they go to 4.2v per cell, so you have half a volt variation per cell between fully charged and fully discharged.

I have that charger and "Storage" takes them to 3.8v per cell.

Don't worry about current (amps)....think of your readings in "volts per cell".....Discharged is 3.7v per cell (never below this for longevity)

Fully charged is 4.2v per cell, and storage is 3.8v per cell.

My Lipos hibernate in the winter....with 3.8v per cell in them.

I always charge mine at 1C and they are 3300mah packs.....so that is 3.3 amps charge rate.

They discharge at 60C if you wish.....but I never take more than 20C out of them....which is a massive 66 amps!

  • Like 1

Share this post


Link to post
Share on other sites

Thank you HornetRacer. I´ll keep that in mind. But if 3,7v is the lowest limit it means that I should set the ESC´s cut-off in 7,4v, which is the nominal voltage, right? Why then the average cut-off is lower than that? I´ve seen ESCs with 6v cut-off!! Edit: I know you´re talking in terms of longevity (and I didn´t know that 3,7v limit, thanks) but 3v/cell limit sound crazy to me now.

Besides, I´ve read they don´t need to be discharged. Maybe is good to do it in case you stop running them before the cut-off?

Thanks again for the info.

Share this post


Link to post
Share on other sites

3.7 is too conservative, unless you're talking resting voltage (without load).

Under load, minimum of 3.0-3.4/cell is the norm for cutoff detection devices.

After all if there wasn't any load, your voltage wouldn't drain anymore would it? :)

Lately I'm finding older packs drop more volts under load than when they were newer.

In round cell era, the boffins called it growing internal resistance - perhaps same holds true now.

  • Like 1

Share this post


Link to post
Share on other sites

3.7v per cell is for longevity.

You can go lower....but your Lipos won't last long!

I fly electric aircraft and my voltmeter shows me the volt per cell after a flying session.......the battery manufacturer recommends 3.7v per cell as the lower limit....which I adhere to.

Obviously this is 3.7v per cell without load as it is the reading that is measured when the model is stationary!

If you want your lipos to last.....don't take them too low!!!......3.5v per cell would be my limit!!!

Share this post


Link to post
Share on other sites

I have been using LiPos for years for both racing and bashing. All my LVC are set at 3.2. I have never had an issue with any packs at this setting and get about 100-150 runs out of a pack before they start to go bad due to their IR increasing.

  • Like 1

Share this post


Link to post
Share on other sites

Well I have a return of 800 cycles (on my aircraft Lipos) using a minimum of 3.7v per cell, and this is also in accordance with the guidance literature issued with the batteries I buy.

4-max.co.uk offers good advice on Lipos, and the owner of the site also uses 3.7v per cell as his minimum.

As I have already said you can go lower, but looking at my cycles of 800 compared to Theibault's 100-150.....then this seems to agree with the literature!

Share this post


Link to post
Share on other sites

I fly electric aircraft and my voltmeter shows me the volt per cell after a flying session.......the battery manufacturer recommends 3.7v per cell as the lower limit....which I adhere to.

Obviously this is 3.7v per cell without load as it is the reading that is measured when the model is stationary!

If you want your lipos to last.....don't take them too low!!!......3.5v per cell would be my limit!!!

so when does your LVC actually *trigger* ??

mine set to 3.2V/cell usually triggers on acceleration =MAX LOAD so the voltage does dip,

then recovers to 8.0ish by time it's driven back to be ankles

I have been using LiPos for years for both racing and bashing. All my LVC are set at 3.2. I have never had an issue with any packs at this setting and get about 100-150 runs out of a pack before they start to go bad due to their IR increasing.

ah thanks for confirming suspicion that IR does rise with age :)

Share this post


Link to post
Share on other sites

Well I have a return of 800 cycles (on my aircraft Lipos) using a minimum of 3.7v per cell, and this is also in accordance with the guidance literature issued with the batteries I buy.

4-max.co.uk offers good advice on Lipos, and the owner of the site also uses 3.7v per cell as his minimum.

As I have already said you can go lower, but looking at my cycles of 800 compared to Theibault's 100-150.....then this seems to agree with the literature!

how much capacity do you get out of your flight packs? vs their rated capacity

for car packs mine are around the 4000mAh size, when I benchtest I draw

about 3500mAh by which they're down to about 3.8V/c without load.

They usually hover around 8.2-8.3v/pack for the first 2000-2500mAh

before dropping more rapidly under 8.0V.

Share this post


Link to post
Share on other sites

I use 3300mah packs for my electric flying.....

I charge at 1C so 3.3.amps charge rate....and this takes me 40 minutes to charge, but I have 25% left in them after a flying session, and this is about 3.7v per cell on the voltage reading on my meter.

This consumption constitutes 7 minutes of flying......

3300 x 0.75 = 2475mah used, 825mah remaining in the pack (assuming I am using all 3300mah capacity)

Share this post


Link to post
Share on other sites

Not too bad then, that's pretty consistent with my #s.

Currently I'm looking for a charger than I can program to cutoff at around 8.10V... not always bang hard into 8.4V.

I'm of belief that the "8.4V" cutoff is not gospel but should actually differ with ambient temperature.

Haven't found anything suitable yet.

Have been going around charting the charge profiles for consumer electronics,

I find all of them cutoff at 4.05-4.08V/c... must be something in that.

They certainly don't go to 4.20V.

Share this post


Link to post
Share on other sites

Well my cells have 4.2v per cell in them when fully charged (obviously without load)

My charger the IMAX B6 shows a 3 cell pack cuts off at 12.6V ....which is 4.2v per cell.

This is consistent with all my packs and the battery literature.

Share this post


Link to post
Share on other sites

yeah all my RC chargers knock them hard to 4.2... which I'm starting to think is not a good idea for when I'm not racing

but if I turn it off manually prematurely... the balancing doesn't happen. :(

I'd rather have them start balancing when it's 4.10

Share this post


Link to post
Share on other sites

According to my literature it is the minimum voltage that does the damage.....ie the lower you take them.......recommending 3.7v as the lower limit.

4.2v is the setting on the charger for the maximum volts per cell.....and this is in agreement with the literature. BUT they don't say anything about taking them up to 4.2v per cell as being dangerous or reduces the life of the cells......it is the minimum that gets mentioned again and again.

Share this post


Link to post
Share on other sites

There is a difference between airplane/heli use and cars. Flight tends to put a lot more stress on a battery. I'm sure I could get many more charge cycles out of my packs, but when you are racing, if your battery starts to drop off, it makes all the difference to how you will finish. They get retired from race duty and become basher packs. Batteries are by their very nature a use and discard perishable in the hobby. With how cheap good LiPos have become, I get rid of them when the IR starts to consistently get in the 30's. Replacing batteries every year or so is no big deal and the last thing I'd want is for one to go up and take out one of my cars with it.

Share this post


Link to post
Share on other sites

I don't doubt you... but I seldom run my RC packs down to cutoff anyway. Can't remember when's the last time I did!

But if you read into lipo chemistry & its ideal charge profile... that "4.2V" does depend on temperature of cell.

More importantly... I sometimes use RC charger to top up the lipos on my other gizmos, eg cameras

and the nonRC packs that have been charged to 4.2V are noticeably bloated vs identical packs

which have only been in camera's original charger. I usually go 0.5C for charge rate to match.

Camera would cutoff at same level on all its batteries regardless, I'd expect.

No difference in handling & storage either.

Which leaves only the charge cutoff as differentiator...

Share this post


Link to post
Share on other sites

Amazing how such a dumb doubt ended up in a very interesting debate!! But I need to read more about electricity to follow you guys (and improve my English :lol:).

So many doubts with words right now that I won´t bother you. Anyhow, the batteries are currently 7,6v with no current (storage from factory I guess). So it´s Ok according to what I read here.

Thank you guys for making this thread so rich (at least for me). :)

Share this post


Link to post
Share on other sites

sorry nobody mentioned earlier, if you have one of those pocketsized chargers

don't bother using discharge function. They often only can disperse 1-5W

so they'll take forever... if you want to store a fully charged pack

just run it in your car for 2mins instead :)

Also you should own one (or more) of these gizmo;-

6589.jpg

tells you voltage of pack & each cell, plugs into balance lead.

Easier than using voltmeter out in the field.

Share this post


Link to post
Share on other sites

Thanks for the tip WillyChang. It´s just that I read in a Spanish forum that it was good to strore them at half of their capacity. But I see here it doesn`t really matter. And actually I don´t know now how full or empty my batts are (I´m silly, the charger only shows the supplied capacity).

Looking out there for the tester you told me I found this chinese one (it also reads the remaining capacity, and that´s what strikes me):

http://www.ebay.es/itm/LCD-Battery-Capacity-Checker-Tester-for-2-6S-LiPo-LiFe-Li-ion-NiMH-Nicd-Akku-/201024548374?pt=AU_Toys_Hobbies_Radio_Controlled_Vehicles&hash=item2ecdff2e16&_uhb=1

What do you think of it at first glance? Looks good enough for me: pretty simple.

Considering the price I think I could try it.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×
×
  • Create New...