whats a good batt for .30 under sub ohming

[bce22]

I've purchased batteries from this eBay seller in the past with excellent results.

http://stores.ebay.com/RL-batterydepot?_trksid=p2047675.l2563

 

[Ryedan]

Talked to a guy at one of the biggest European importers for batteries. He said (he wasn't selling me anything) they are using the Sony cells and if you look up the test data for 30a Efest and compare it to the Sony ones the test data is the same. They are priced the same too, so if you don't trust what I'm saying go with the Sony ones.
He also told me to stay away from the 35a Efest batts until some solid stress testing has been done on them.

Best bang for your buck is the Sony US18650VTC4 30amp or the Efest 18650 30amp.

Thanks for the info BaDaBooM, that's good to know.

I think I would buy VTC5 now though instead of the VTC4. I think they're about a buck more, which is worth it for me.

 

[beckdg]

i'd like to see the samsung 20R batteries on that test. also, considering the prices are barely different between the different cells and you're not going to use them down to 2.5V, who cares whether they produce all their capacity? you're only interest should be what capacity you can use under the load you're going to apply down to a voltage that's usable to you. in that context, the vtc5 is obviously better than the vtc4. i did notice the comments on temperature, for which i think it's likely he was referring to the vtc5s which have been noted to heat up very quickly at higher currents.

 

[Ryedan]

i did notice the comments on temperature, for which i think it's likely he was referring to the vtc5s which have been noted to heat up very quickly at higher currents.

I thought he was referring to all the batteries at 10A and up, but I could be wrong. He didn't mention the VTC5 by name though.

 

[beckdg]

He didn't mention the VTC5 by name though.

no, but he did phrase it something like "at one point i stopped due to...". this suggests to me that there was only one time he was concerned about heat until he learned better.

check out the attachment hot.jpg at the bottom of this vtc5 page... AkkuDB

it's the only page i've noticed that on out of the batteries i've looked at. notice the temps of the vtc5 @ 20A start at room temp then quickly rise to 60°C where the discharge is terminated and the temps of the vtc4 seem to maintain room temp at the same 20A discharge according to the graph.

sony recommends operating temps of 20°C to 60°C for it's lithium ion cells as per this pdf... http://www.sony.com.cn/products/ed/battery/download.pdf

also, if you translate the page, above the attachments it says...

Careful: in a continuous discharge, this cell will get extremely hot - up to 80 ° C at 20A, up to 125 ° C at 40A

for perspective, 60°C = 140°F, 80°C = 176°F and 125°C = 257°F

THAT'S HOT STUFF!

 

[Ryedan]

THAT'S HOT STUFF!

Very true and very interesting beckdg ! It outperforms the VTC4 at 20A, but heats up significantly. That would normally make me think the amp rating was overstated, but in batteries where I've seen that done they also don't last long at the elevated discharge rate.

Food for thought for sure.

 

[beckdg]

Very true and very interesting beckdg ! It outperforms the VTC4 at 20A, but heats up significantly. That would normally make me think the amp rating was overstated, but in batteries where I've seen that done they also don't last long at the elevated discharge rate.

Food for thought for sure.

i'd say the amp rating is definitely over inflated. you can't do a continuous discharge to cutoff voltage at 66% of it's amp rating without it overheating. i doubt that cell would survive anywhere near half the 500 cycle "rating" at 20 amps full discharge let alone 30 amps. highly doubt it. though, i'm sure 40 amp bursts would hardly effect the cell for quite some time looking at how the voltage stays in those graphs. so still a very good cell for our purposes as long as it's not in the wrong hands. a hard short could be catastrophic quick with temps like that.

 

[Ryedan]

i'd say the amp rating is definitely over inflated. you can't do a continuous discharge to cutoff voltage at 66% of it's amp rating without it overheating. i doubt that cell would survive anywhere near half the 500 cycle "rating" at 20 amps full discharge let alone 30 amps. highly doubt it. though, i'm sure 40 amp bursts would hardly effect the cell for quite some time looking at how the voltage stays in those graphs. so still a very good cell for our purposes as long as it's not in the wrong hands. a hard short could be catastrophic quick with temps like that.

I don't think the VTC5 will turn out to be dangerous when it vents. It would still be great to see a hard short test done on one though.

It's battery temperature that causes a cell to vent. Straight ICR cells become unstable at around 150*C, straight IMR at around 250*C. My bet is these cells are at least as stable as IMR or Sony wouldn't be putting them out there. Then there are LiPos. My model airplane LiPos get quite warm on every flight and handle that very well for a good number of charge cycles.

There's also new technology being introduced all the time these days. In was amazed when I saw the video of a NCR18650A take a hard short for an hour and still be charged and used.

 

[sawtoothscream]

my friend uses .3 builds and uses sony vtc4. My brother and I use .4 -.7 builds and use sony batteries.

from my experience SS mods will heat up. my brass ones seem to always stay pretty cool even when the atty gets a little warm.

 

[beckdg]

I don't think the VTC5 will turn out to be dangerous when it vents. It would still be great to see a hard short test done on one though.

It's battery temperature that causes a cell to vent. Straight ICR cells become unstable at around 150*C, straight IMR at around 250*C. My bet is these cells are at least as stable as IMR or Sony wouldn't be putting them out there. Then there are LiPos. My model airplane LiPos get quite warm on every flight and handle that very well for a good number of charge cycles.

There's also new technology being introduced all the time these days. In was amazed when I saw the video of a NCR18650A take a hard short for an hour and still be charged and used.

interesting. i'd like to see one hard shorted now.

yeah, i've vented a couple lipos. even rebuilt a couple using remaining cells. my smc packs get to see some serious amp draw from my tenshock motors and fair very well. i love those packs.

i trust your understanding but i, personally don't trust battery university info. it comes from one guy specifically using it to refute what we'd all seen to be true and using some of the info blatantly out of context to make a point on a regular basis. it was amazing how many people read the info wrong and worse, how many followed this guy like blind squirrels following the scent of a nut.

 

[HazMatt]

I would like to see graphs comparing the LG 2500mAh 30a to the vtc4 and vtc5.