dakrat

just a quick question.

when i unstrap my pack every run, the battery label keeps sticking to the tape and i ended up tearing the label. i was thinking of wrapping each cell with a cell wrap. is this a good idea? what about the temperature?

Korey Harbke

iTrader: (13)

I try not too. I think of it as another blanket for the cell and doesnt let heat escape as easy. This can be a good thing in really cold conditions, but I dont feel it's worth the risk. Try using clear finger nail polish or something over the labels. It's a hard covering that doesnt wrap aroudn the entire cell.

-Korey

beerbarron

I tested a monster stock armature and found no measurable change in the resistance at 65, 125, 145, and 188 degrees. Maybee I need a more accurate meter.

I am curios what the average capacity the latest batch of IB38's are getting? Mine are 405-413 and I read that Hara was using 490 is that right?

koabich

I never used to wrap my cells but if I ,after running them once, they often looked beat up. And it does stink if you kep ripping the labels off. I have heard that the wrap is just another barrier to keep heat in the cells. Well, I played with this theory by cycling 2 similar packs on a GFX charger at 35 amps and with each cycle I could tell which had the wrap and which did not going by the temp of the cells alone. Granted, it ws just 2 packs and not a large enough sample to draw a conclusion but it was good enough for me .

On the race track, I also never noticed a difference. All I can say is that I now wrap all my cells and will never look back.

Plus, if you resell your old packs to help finance you new packs, I guarantee, if you have 2 identical packs but one had the wrap and one doesn't, you will sell the wrapped pack every time and for a higher price for the simple fact that the pack looks brand new! Would you rather buy a pack that is in good condition or one where the factory shrink wrap and matchers labels are ripped off?

dakrat

i agree with you. numbers sell! period! i just got these 1.211v and dont wanna loose the label lol! heres what i just did, i carefully peeled the label, there are two wraps around the cell, remove the second wrap, stick the label back on then wrap with cell. buwala! although the second wrap was a little thinner than the one i replace with. still better than having three wraps right?

beerbarron

This one time at band camp I ripped all the shrink wrap off of my cells and reassembled the pack with none. . . That was a bad move. It seems that the shrink wrap insulates one cell from the other. When I charged the pack it got really hot and stayed hot for a long time even after it was off the charger. It seems that the shrinkwrap keeps cells from shorting out. Now I wrap each cell before I assemble a new pack. I'll even double wrap the font cell in case of a collision.

dodgeguy

iTrader: (208)

You will see the voltage drop under load. Using your meter the way you are will not show you what you are looking for. You would have to set your meter up to measure a volyage drop.

beerbarron

I am not sure if my meter will do that. I'll check later on today.

PitCrew

The increase in resistance on the windings when the motor is hot is going to be negligable. The reason a motor "fades" is from heat in the magnets. They lose strenght when they get hot. Also, the magnets get hot just from them having to "work" against the emf of the coil. If you take to magnets in opposing orientation, and move them across eachother, you will heat those magnets up.

Lets say for instance, you had two batteries that both charged to 3900 mah (as both the IB's and GP's will do) so the capacity is the same. If one pack produces more voltage through the motor, then that battery will dump sooner. Its as simple as that.

If you heat up the motor artificially, or by running it for an extended period of time, you are weakening the magnetic field of the magnets, so the motor is not going to produce the power it did when it was cool. However, given there is no brush wear or comm wear in this scenario, then the effeciency of the hot motor will be higher than that of a cool motor. Less magnet in the motor equates to increased effeciency due to reduced reverse electro-motive force.

PitCrew

In your example the hot motor has more resistance, therefor there would be less voltage drop....

what are you getting at then?

Danny/SMC

iTrader: (2)

Your IBs are matched at 35 amps which means they are 473-482 at 30 amps. Hara uses Orion packs and Oscar maybe able to tell you why but Orion numbers aren't the same as what the US matchers produce. They have higher voltage and capacity numbers on the labels but they claim they use 30 amps. Two years ago I tested one of there packs and the runtime on a GFX was off by 40 seconds and the voltage by .015. Based from what we have seen GP3700 should be 435-460.

PitCrew

Doesn't Orion use the Lavco system?

I heard once that the discharge on the Lavco is not linear. THeir "RDS" discharge is an increasing and decreasing discharge load. This would give higher run-time and average voltages as compared to a linear discharge, if their max discharge load was 30 amps.

Their "RDS" is Race Discharge Simulation. So, the above idea is based on the description and what I have heard...

Team Duratrax

Interesting stuff. I need to know something Danny.

.5mv = 30mv, but I noticed that the SMC site states that .5mv = 50mv Is this mainly because you use a Turbocharger? Why such a big leap in mv?

Hyper1

Less magnet in the motor equates to increased effeciency due to reduced reverse electro-motive force.[/QUOTE]

What you're talking about here is EMF & CEMF not reverse EMF.

EddieO

iTrader: (6)

Orion uses a modified TurboMatcher system now from what I remember reading by Rick.....nobody uses the lavco anymore that I am aware of....

Later EddieO