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 LiPo question....

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MarkM
Rc enthusiest
MarkM

Number of posts : 113
Registration date : 2009-05-08

LiPo question.... Empty
PostSubject: LiPo question....   LiPo question.... Icon_minitime1Mon Sep 14, 2009 10:14 pm

I bought my first LiPo this weekend - SMC 4000mah pack. Picked up a venom pro charger. I used it twice this weekend. I don't have a LVC yet but kept an eye on the voltage. When it really dipped on the second run, I measured the pack voltage - 6.2 volts or 3.1 volts per cell - it's a 2 S pack, naturally I stopped at that point. The pack read 6.4 volts on the charger tonight when I went to charge it.

I went to charge it tonight. The venom pro has a parameter called max capacity which is the maximum allowable capacity the charger will charge the battery. I had it set for 4000mah. The first two charges the charger stopped before hitting the max parameter.

Tonight it stopped at the max parameter of 4000mah - seems a little odd to me I guess. The pack seemed to charge fine and was balanced at 4.1 volts each cell. The pack is stone cold during charge.

I noticed the case seemed just a tad warped tonight...not really deformed, just a little bit, rocks back on forth on a flat surface a bit.

Maybe I'm paranoid, IDK. I have it sitting out side now in a 50MM metal ammo case - lid closed but not locked. I'll keep an eye on it.

I ran my evader with it this weekend, the 17T speed gem acted like a BL - amazing! I was getting little wheelies here and there with a 16 tooth pinion and the stock spur ;-)


I haven't run it in the VXL powered Stampede yet - can't begin to imagine what that's gonna be like :O

MM
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Micro-T Master
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Micro-T Master

Male Number of posts : 1017
Registration date : 2008-06-17

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PostSubject: Re: LiPo question....   LiPo question.... Icon_minitime1Mon Sep 14, 2009 10:50 pm

For the max capacity, not only is there a max you can set for the charger, but the battery can only be carged so much before it peaks. It sounds like you did not drian a full 4000mah of energy from the pack for the first 2 runs, but did on the 3rd run so the chargerd peaked it on the first 2 charges and only put 4000mah into it on the 3rd charge.

As for the warp in the pack, i have a pretty good bet on paranoid lol... with the way you described running and charging the pack, it is very unlikely your lipo is damaged.

I would run it anyways Wink

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rclugnut
Rc Master
rclugnut

Male Number of posts : 904
Registration date : 2008-07-10

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PostSubject: Re: LiPo question....   LiPo question.... Icon_minitime1Mon Sep 14, 2009 11:05 pm

yeah it could be the case just got a little tweaked or something i wouldn't be worried also i wouldn't set that parameter thing, my zippy 5k took 5136 the other day after hitting lvc at 6.2V, and my Ep 4200's have taken 4900mha multiple times and my ep 4600's are taking a little more than that now and are really coming alive with the use basically the # on the outside isn't near to what it'll accually put out, i don't think i've ever run a Ni pack with a voltage over 7.5v and had it go anywhere fast... and they're rated at 7.2V

you said it was a SMC right if you're worried give them a call i've read coversations that people have had with SMC support and its pretty impressive

the lug


Last edited by rclugnut on Mon Sep 14, 2009 11:26 pm; edited 1 time in total
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MarkM
Rc enthusiest
MarkM

Number of posts : 113
Registration date : 2009-05-08

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PostSubject: Re: LiPo question....   LiPo question.... Icon_minitime1Mon Sep 14, 2009 11:08 pm

Thanks Micro T Master...Yeah, the first run I'm absolutely sure it wasn't fully drained (it was new off the shelf) so I can see it peaking before hitting the limit. The second run I noticed a severe drop in power in just one or two laps on my track and thats when I quit running it and double checked the pack voltage.

I suppose you can reach the rating of the pack without peak detection - I can see how that could happen. I think I'll leave that parameter set at that value just for safety. I'm charging at 1C rate (4 amps) per the manufactures spec and will only run the 17 turn brushed motor for a few more cycles before I run the VXL or 12 T Titans to limit discharge while the pack is still so new.

But yeah, I paranoid yet ;-)
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evil3
I feel dizzy
evil3

Male Number of posts : 422
Registration date : 2008-07-10

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PostSubject: Re: LiPo question....   LiPo question.... Icon_minitime1Mon Sep 14, 2009 11:11 pm

Your pack seems to be fine, but the only way to truly know is to open the case if you can to check the cells.

I think you would be fine, as I have seen pack that have swellen and they have been charged with out issues, but the performance suffers.

As for the pace being cold durring a charge, that is normal. Li-po's when charging cool down to room temp durring a charge, so really if you wanted you can charge them up right after running them (I don't recomend that, as I like to let it stablize for 5 or so min's (i.e. I go to turn marshall, then after I get back to my pit I charge it up)).
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MarkM
Rc enthusiest
MarkM

Number of posts : 113
Registration date : 2009-05-08

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PostSubject: Re: LiPo question....   LiPo question.... Icon_minitime1Mon Sep 14, 2009 11:12 pm

Good point Lug...maybe I'll bump the limit up to 4500mah for this pack.

So what are you guys charging your packs "in"...i.e. LiPo sack, ammo can etc?

Old underwear? ;-)
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evil3
I feel dizzy
evil3

Male Number of posts : 422
Registration date : 2008-07-10

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PostSubject: Re: LiPo question....   LiPo question.... Icon_minitime1Mon Sep 14, 2009 11:28 pm

Uping the C rate isn't really good, and really isn't needed. As for the mAh limit uping that on a good charger doesn't really do anything, as the only thing that will do is allow you to use a higher c rate. being that li-po chargers charge in a CC/CV mode (no pulses) they are also made to find the peak voltage (to an extent) so with a 2s li-po it shouldn't get over 8.4v's when fully charged.


As for me I use a li-po sack to charge my pack in, mainly because they are required for racing other wise there is no need to use one as li-po packs are more then safe as long as you take care of them charge them right.

As for my settings I just set my charger (duratrax ice) to 1c of what ever the packs mAh is so with my 3400 it is charged at 3.4 A, and 4800's are charged at 4.8 A. Also with my charger you can change the amount of charge that can be put into the pack (i.e. the max before it cuts out). I think I have that set to 110%, but like I said in the first paragraph the charger won't charge the pace higher then 8.4v's as long as you are in li-po (CC/CV) mode.
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rclugnut
Rc Master
rclugnut

Male Number of posts : 904
Registration date : 2008-07-10

LiPo question.... Empty
PostSubject: Re: LiPo question....   LiPo question.... Icon_minitime1Mon Sep 14, 2009 11:37 pm

MarkM wrote:
Good point Lug...maybe I'll bump the limit up to 4500mah for this pack.

So what are you guys charging your packs "in"...i.e. LiPo sack, ammo can etc?

Old underwear? ;-)

uhh my floor, i'm baller and don't use a sack, but if you want one go to a hardware store buy some firbe glass cloth break out the needle and thread and BAM you'll be able to make a few sacks for like $15-20 depeinding on size and such...

if you can i'd let the charger just auto stop, my superbrain 977 has that same feature and i never use it after compairing the lable specs to what the charger says, i feel you'll get much more outta your packs if you let the charger find the peak as opposed to setting the peak, its like putting a 5000rpm cut-off in a F1 car... okay a little extreme but you get the idea...

the lug
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