Uh oh, did I ruin my SMC Lipo's?

Here is something else to remember.....
If you increase your LVC from 3.0/cell to 3.2/cell it will decrease your runtime (which inturn will reduce the mAh you put back into the cell).
I don't know if a loss of 5-10 minutes runtime is the appropriate runtime loss, but some runtime loss should be expected. Keep running at 3.2 for a several charges and see if it hold steady (runtime as well as mAh replaced). If it hold about steady you should be fine...


But then again my opinions seem to be a bit off lately, so I might be way off base.

[TexasSP]

I would say that is a fair trial there. If it's consistent at 3.2v cutoff for 8-10 charges I would say everything is okay. But if you loose 100mah or more across the 8-10 charge cycles keeping the lvc the same at 3.2v then you are over stressing your packs.

[zeropointbug]

Linc, I know lipo's are not like A123's for cycle life, but you get more than 100 cycles out of them don't you?

Another example... say if you DID get 100 cycles from 80% DOD, then you can expect somewhere around 150 cycles at 60% DOD. And if you are really crazy about total calender minutes out of your pack, you can always use 10% DOD and get something like 2000 cycles from it.

Also, charging rate has alot to do with it as well, same with operating temp (big time)... so the newer cells that run cooler and can handle 5C charging are definitely going to last a good deal... if kept to running your typical load along with 1C charging.

[lincpimp]

Originally Posted by zeropointbug

Linc, I know lipo's are not like A123's for cycle life, but you get more than 100 cycles out of them don't you?

Yep, I figure you can get at least 150 cycles, but even at 100 cycles the cost savings over nitro is massive.

[Finnster]

Originally Posted by lincpimp

Thanks, ZPB! I had the DOD term on the tip of my brain, just could not think of it! I do remember reading this somewhere, and the guy had posted graphs and all kinds of other info too.

Look at it this way, if you buy a zippy lipo for 80 bucks and get 100 cycles out of it, cost is 80 cents to run it for 30-40 mins. So that is 1/2 cent a minute. Not sure what the charging will do to you electric bill, but it cannot be much?

Take nitro costing 30 bucks a gallon, and the average tanks size is 5oz and yields about 8mins runtime. So that would be 25 tanks per gallon, 1.2 dollars a tank, so about 15 cents a minute.

At 14 cents a minute difference a 200 dollar charger is covered in 1400 minutes, about half of what I posted a zippy should last. So you could buy a new charger every 50 cycles and still not have spent as much as you would have on nitro fuel for the equivalent runtime.

Not sure if that is right, seems very good for lipo... Maybe I got something wrong, although the math is pretty simple.

Big difference, huh... And if you get past 100 cycles the difference is even more.

I know I can blow out $5 of nitro pretty easy if I take the Sav out during lunchtime. Frickin truck eats more expensively than I do.

OTOH, the downside to BL is usage, if you don't run the truck very often, natural decay of the batts eats up lifespan w/o use. Unfort there are a few lipos I have for trucks I barely run anymore (little free time w/ 2 little kids now) so those batts are basically rotting away. Least nitro is a pay as you go. This is what's holding back the BL conv for the sav at this point. ~$150
for a motor and ~$200 for a couple sets of batts buys quite alot of fuel, esp at my current burn rate (1.5gal YTD.)


As far as LVC goes, I set @ 3.2 IIRC, but as soon as the batts feel a little drop in I power I kill it. Rarely hit the lvc this way. So far so good on lifespan (2-3 yrs on batts, who the F knows how many cycles that was)

[zeropointbug]

Yeah, agreed with the usage aspect... but on the same hand, the "calender life" of lipo's is at least 6 years (if maintained). A123's are 10+ years calender. So after all, it shouldn't come into play in RC, as you would most likely replace the battery before that time anyways... you know.

[zeropointbug]

BTW, does the Quark 125 have a 3.2v/cell cutoff? thanks.

[lincpimp]

Originally Posted by zeropointbug

BTW, does the Quark 125 have a 3.2v/cell cutoff? thanks.

Nope, highest is 3v per cell.

Well this is the email I got back from Bryan at SMC when I asked him about this


Bryce,

For starters, I would def. raise the cutoff on the ESC. I feel safe with mine set from the factory. I don't have the castle software to change mine, but when the truck goes into LV mode, the packs are coming out of the truck reading around 6.60 to 6.70 per each pack. As for the puffy packs...If you let them cool down and wait a while they "should" shrink back to their normal size. If they do not, there is damage done beyond repair. If you would like, you can send them in for us to test if you do indeed feel they are damaged or you no longer get maximum power and runtime from them. I know it doesn't help but we do have a 50% off the MAP price for warranty of a defective pack. $42.75 per pack for a replacement is still not cheap, but it does help a little if the consumer makes a mistake, intentionally or not. Please let me know if you would like us to check out the packs and keep me informed on the swelling issue. Did they go back down or are they staying puffed up?

Thanks,

Bryan @ SMC


Its really hard to tell if packs are puffed or not now, if not near impossible. So i'm just gonna keep running and keeping an eye on them and take this as a important Lipo lesson learned. Changed the LVC to 3.2v. Damn that Castle link is godsend for these kinda things.

[zeropointbug]

Thanks Linc, what external LVC should I use? I could also just do it by minutes of runtime and then just shut it down. But to be safe, lvc might be in order.