All-battery li-po's on sale

[greasypants]

Specials and Promotions

15% off Any of 350 Lithium Polymer (Li-Po) Battery Packs

with code: lipospecial
all-battery.com

 

[Reid Welch]

I think I'd pass on house-branded volatile lipos, now that we know that fire-safety lipos are available from Kokam, and even the small maker, Wanma (through BatterySpace).

I would want to see full technical data on any cells I buy, data produced by the cell manufacturer.

I ordered a BatterySpace-assembled pack earlier this week. 37v/8ah 5C.

Now, if I could afford the premium price of Kokams, and were Kokam packs readily available, that's the premium safety/performance way to go.
Cheaper in the long run to use the best, in this case.
Besides, the buyer of Kokam or other -certified safer- lipos, may save his/her property from conflagration.

 

[patrick_mahoney]

Thanks for the link to the all-battery lipoly sale, greasy.


Reid, I'm not convinced about the supposed safety of Kokam packs versus other lithium polymer batteries. I have a couple of Kokam 20C packs and they perform to spec, but they seem similar in all respects (except price) to other less-name-brand packs that I have from other places - like http://www.maxamps.com . I'm not saying that the Kokam guys are lying - but that I have a spec sheet for my lithium ion cells that shows that they are not going to explode either... and yet I know Xyster is using the same cells and has had several rupture.

I tend to trust A123's, and emoli's for non-combustion capabilities, but I haven't heard the RCGroups guys - or anyone else - raving about how the Kokam's don't ever have problems, and until I do, I'll remain unconvinced.

 

[patrick_mahoney]

Duplicate post - I was on a bad connection at the time. Down in your neck of the wood, Reid - in Sarasota for a few weeks enjoying the beaches.

 

[Reid Welch]

Why I lean: The big maker Kokam -states- no fire, no flame.

A mere RC user stated just yesterday in this thread:

I can fix it

Join Date: Mar 2005
Location: blue springs missouri
Posts: 42

I've gone to kokam batteries myself for the same reasons that Leonard stated but I am not exclusive yet to kokam, I havent phased out all my old batteries yet but when they go I will probably replace them with kokams.

I recently disposed of a bunch of packs that were bad from abuse etc.
I got to do destructive testing in my back yard. most of the non-kokam packs were scary, with piercing they shot sparks
hot enough to melt aluminum and spewed lots of smoke, even packs that would not charge still could have started fires.

The kokam cells wouldn't do anything if they had no charge, the ones that would charge still didn't do much.
A hole clean through just made the pack warm. a knife stabbed into the pack would just spark a little and puff a little smoke; my cigar smoked more when set in an ashtray. even packs bent over and flattened didn't do anything. shorted across the terminals just got whatever used to short hot until the battery went dead some puffed and got warm but no dangerous results. I tried real hard to get something to happen and couldn't. and these were packs already abused.

I'm not saying that you couldn't cause a fire with the kokams but I think that the chances are better that your wires on your speed control or charger have a greater chance of melting and shorting before the kokams do something bad. (you could still ruin the pack, they haven't made them totally idiot proof yet)

Jason

 

[Ypedal]

One thing i like with the kokams is that you can expect cells to be well matched, both in capacity and discharge rate. Just like BS packs vs Ebike.ca packs.. you usually get what you pay for.

 

[Reid Welch]

What's lacking in either? I bet Justin matches them up with more care, eh?
What's to match in Lipo cells, though? I would think that cells of a production run will be all pretty close. Terminal voltage is the charge voltage. No need to match there. Discharge is always halted before any cell falls so low as 2.75V. Margin for conservation there.


But I'm not expecting gold for the price paid for the BatterySpace pack.
I got it because it's the only purpose-built ebike lipoly pack assembled in NA that I knew about. I did not know of Kokams at the time of ordering.

I've been very pleased with the BS 14.4V NiMh bottle battery light.
I like the charger too.

So far, my luck with BS has been fine.

Justin will be selling lithium packs again in the future.
I look forward to that day. He has earned our loyalty as supporters of his quality service.

 

[xyster]

A mere RC user stated just yesterday in this thread:

Could be a company shill who wrote that glowing report. I'd listen to Patrick Mahoney -- Mahoney knows his Li-poly's, and that's no baloney

One thing i like with the kokams is that you can expect cells to be well matched, both in capacity and discharge rate.

According to batteryuniversity.com, unlike nickel batteries, lithium role off the assembly line closely matched -- something to do with the nature of the manufacturing process. Haven't tested it myself. My 20, 15-cell subpacks all drain at the same rate, but of course any differences are being averaged across those 15 cells.

Discharge is always halted before any cell falls so low as 2.75V. Margin for conservation there.

Trust me Reid, halt it at 3.7v (resting) not 2.75v. I know what all the company graphs say, but measurements by the RC guys (and my experience with ruptured canned cells) says differently. At 3.7V resting, only 11% is left anyway...and that can go fast, producing enough heat to ruin your day. Just take a hand off the throttle for a second, and cease and desist the e-assist if the pack voltage is below 37.0 (at that point some cells will likely be ~3.68v anyway).

 

[Reid Welch]

Hi all.

1) First, I should have =thanked= greasypants for the heads-up. I forgot my manners, sorry! Thank you, guy!

2) I'm not convinced of anything, either. But I don't see claims of fire resitant lipos from but two makers so far. Patrick cites a third.
I do see a great deal of respect (and regrets of the higher prices) paid to Kokam.

3) These things need good management, regardless of the make

4) That quoted text could be by a shill, but it sure rings true. He came back a while later and added, goofily:

Oops! I don't know how many of you caught that, but warhawk80 is my brother Wesley, we share a laptop downstairs when we don't want to go upstairs to our own computers and I did not realize that he was still logged onto rcgroups when I posted the above under his name by accident.

so don't get confused the next time warhawk80 signs Wesley instead of Jason to a post......... (it's ok, some of our friends cant keep us straight either and we don't look alike).

Jason

And no-one in the group is coming forth with denials's of the guy's veracity; and there are many Kokam, and -all brand- of Lipo users; I have yet to see any boasts of other so-called brands (some are second-party labled) being explosion resistant.

Xyster, I quoted that number not because I plan to use it, but because it is stated by the makers as the bottom line of the discharge; I know from reading now that at 3.7V, there's not much more to dig out but to shorten the cycle life past that.

Anywho, thanks for forgiving my agressive posting style if you can.
I surely don't want to be seen as a SHILL for Kokam....

now, BS? I'll push BS.

What? I always have? Hmmm! :lol:

 

[Ypedal]

I'm not writing from experience either, YET...

The BS packs may very well end up being just fine !!!.. only one way to know and we are about to find out from you now are'nt we !

My biggest fear is that it may potentially end up like what Bob McCree had with poor construction jobs and what not.... hopefully not. For the price.. you could get double the capacity of a kokam priced pack..

Personally.. me.. myself.. i would order bare cells.. test them .. and make the pack on my own. If such a thing is not possible for you then having BS do the job is fine. :wink:

Once i recover financially from my crystalyte shipment we can compare results from your BS pack.. and the Thunder power pack i plan to build.

 

[Reid Welch]

Yes, I think they'll do a good job for my order.
They know that we're all watching.

The lipo pack is a new product for them too.
This particular assembly will get their best attention.

They are on it now
http://forums.batteryspace.com/forums/viewtopic.php?t=8315

 

[Ypedal]

http://www.maxamps.com/products.php?cat=44




12000mah Capacity
7.4 Volts
44mm X 137mm X 38mm
20C Constant(240 amps)
30C Sustained(360 amps)
50C Burst(600 amps)
545 grams

Hm.. lets see... 10 of these at 212 cad$ = 2120 $ + shipping.

545 grams x 10 = 5450g = 5.5 kg = 12 lbs -- For 12 AH !

2 x Ballancing units at 60 $ each = 120 $ cad
http://www.maxamps.com/proddetail.php?prod=LBA10


Charger = 250 $ canadian
http://www.maxamps.com/proddetail.php?prod=TP1010C
( At this point.. what the hell.. may as well get the good one ! 8) )

So.. that's 250 + 120 + 2120 = 2500 $ + shipping, duties, and brokerage.



But.. daym.. this rig would power a Blade !!!

 

[Reid Welch]

...I have a couple of Kokam 20C packs and they perform to spec, but they seem similar in all respects (except price) to other less-name-brand packs that I have from other places - like http://www.maxamps.com . I'm not saying that the Kokam guys are lying - but that I have a spec sheet for my lithium ion cells that shows that they are not going to explode either... and yet I know Xyster is using the same cells and has had several rupture.

Pardon me for excerpting the main points.
We're most focused on pouch cells in this thread: which ones are liable to vent with fire if abused or failed.
Xyster isn't using pouch cells, but ventable, gentle, li-ion cans.
And to my mind, the explosion of a pouch cell is only possible if it is -contained-, as in the particular upcoming order of ten stacked lipoly cells in an ABS caddy box,
all covered over with HD shrink = a predicted " bang when/if it goes
(all ten cells at once, possibly, all that fuel at once.)

v. a soft pop and hissss in the case of a single cell laying on some surface.

A stacked pack, bound up together is apt to go off in a big way,
as Blakesley's ammo box-awry test proved. WHUMP.
The sheer volume of energy of that big pack he set off on purpose...
was, however, less than my e-bike pack will contain

________________________

Found this older document at FMS, a Kokam distributor.
It was last updated July 2005. Filter and weigh everything we read:


Snippet:

What Can Burn in a Battery?
Yet, with all the above, you must be aware that Li batteries can catch fire under extenuating
circumstances.
Metals will burn if subjected to intense heat that ignites them. Li is a metal. You have only to see
and hear the roar of the solid rocket boosters in a shuttle launch to see what a half million or so pounds of
finely powdered aluminum does when you ignite it with a 250 pound pack of igniter material that is like a
bomb going off. It is the finely powdered Li in the cell that creates the real heat. Yes, the electrolyte that
is an organic material burns about like paper but does not contribute much.
The Kokam HDR cells can sustain up to 18.5 V over charge without igniting (Vs 6.5V) . This
feature, in conjunction with the FMA cell balancing chargers, means that Li Po batteries are now very
much safer. All that is tucked in the new cells with a miniscule increase in weight. That feature is well
worth the tiny increase in weight because the cells are still about 1/5 the weight of an equivalent Ni Cd. As
seen earlier, the performance of Kokam HDR cells is superior to all others.

http://www.fmadirect.com/support_docs/item_1197.pdf

 

[Reid Welch]

I'm not writing from experience either, YET...

The BS packs may very well end up being just fine !!!.. only one way to know and we are about to find out from you now are'nt we !

My biggest fear is that it may potentially end up like what Bob McCree had with poor construction jobs and what not.... hopefully not. For the price.. you could get double the capacity of a kokam priced pack..

Hi Buzzz, I did not know that BS made disappointing quality packs.
I'm not up on this stuff. What was wrong with Bob's pack?
Bad pack construction can be a bomb in waiting.

Personally.. me.. myself.. i would order bare cells.. test them .. and make the pack on my own. If such a thing is not possible for you then having BS do the job is fine. :wink:

Well, I would much prefer that route myself. Note their price for ten of the cells in question plus the PCM, is about the same as the cost for the pack all put together by them. I'd definitely like to see the construction of the upcoming BS pack. Have requested them to send me photos of the construction. Barring that, I'll be cutting off the shrink wrap for a look-see after the warranty period has expired.

Once i recover financially from my crystalyte shipment we can compare results from your BS pack.. and the Thunder power pack i plan to build.

I'd like that. I bet you'll build a much bigger pack.
Mine is just a basic one, sufficient in size... to get me greedier yet, ha ha.