Sony US26650VT Li-ion Cells - Need More info

[othello]

I don't use the Sony 26650VT but the smaller 18650vt (1100mAh -> 9s2p in my truggy). Those have the same characteristics but feature a lower Amp rate due to their smaller size. First off you won't need any balancing cable. This cells do remain perfectly in balance. Charge them up to 4.1 or 4.2V per cell and you are good to go. I don't use an LVC since summer 2007. Capacity hasn't changed noticeably still 2200mAh can be charged back.

Their weakest point is a constant drop in voltage during discharging (your car gets slower and slower) and when it comes to power density A123 cells are superior, as they can deliver up to 100A per cell in a 1p config (1 A123 cell delivers up to 220W burst but may drop voltage down to 2V). At 50A the sony 26650 will drop below 3V per cell and at the end of discharge even lower so you might get up to 130-150 Watt per cell. If you don't expect lipo or A123 performance than you won't be dissapointed as those cells are very reliable and uncomplicated when it comes to handling: good bashing cell for a milder setup.

[sikeston34m]

Thanks for the input Othello. I was hoping you would join in here.

I just finished with the 1st test run. It is true that the voltage drop curve is different. I noticed that.

1st part of the run was awesome. It would jump out the hole like gangbusters. I had to watch that itchy trigger finger or it would land on it's lid from a backflip. These cells do deliver good amperage. They didn't even get warm with this setup. As the run progressed, the urge to flip or do wheelies slowly "went away".

I had my LVC set at 3.0 volts per cell. Should I lower that some? Sony says these can be discharged to 2.5 volts per cell. What got me was, these packs didn't just dump like lipo's at the end of the run. It would still go, but I could tell it was definately on the LVC, so I just stopped. I ran it hard and the run lasted 25 minutes. I'm charging them back up now, so I'll see how many mah my superbrain puts back in them. I don't feel as if 5000mah was discharged this round.

From the looks of things, these make GREAT bashing packs. They are tough. They are somewhat heavier than Lipo, but they do deliver.

[phildogg]

how do they seem price wise? comparable to A123 or lipo in price or cheaper? seemed like a quick way to get them in the maxx.lol
phil

[lincpimp]

Sounds interesting. I could make some 5s packs and put them in the old emaxx. Mine has a double tray, so the packs could be placed on their sides and stood up that way to fit. I may have procure some cells, hint hint

[sikeston34m]

Originally Posted by phildogg

how do they seem price wise? comparable to A123 or lipo in price or cheaper? seemed like a quick way to get them in the maxx.lol
phil

Much cheaper!

I'm sure I got a "deal" on these cells. Average retail is probably $7.50 or $8 bucks a cell.

In the two packs that you see, I have about $55 bucks in this setup. Cells, Connectors, shrink and everything.

4S at 5000mah. Overall, it's a good value I think.

[sikeston34m]

Originally Posted by phildogg

how do they seem price wise? comparable to A123 or lipo in price or cheaper? seemed like a quick way to get them in the maxx.lol
phil

Yeah, I cut the sidewalls out of my battery trays with a dremel tool. It's plenty strong, so I'm not worried about that.

One extra long wire tie strap to keep them from bouncing out the side while doing cartwheels. LOL (Like I mean to do that)

With the side walls of the Battery Compartment removed, A large variety of packs will fit. I can now use my larger lipo's with this setup. 4S or 6S is not a problem even with the larger Lipo's. 4 cell A123 packs will now fit fine also.

[sikeston34m]

Originally Posted by lincpimp

Sounds interesting. I could make some 5s packs and put them in the old emaxx. Mine has a double tray, so the packs could be placed on their sides and stood up that way to fit. I may have procure some cells, hint hint

Hey Linc,

Are you thinking of doing a 5S2P setup for your E maxx?

[lincpimp]

I think that they would be perfect for the 2wd emaxx that has the feigao 15l/bk9920 combo in it. I have a hacker 15l smooth can here that will most likely replace the feigao. The truck is pretty light, even with the pair 2200 5s packs. Looks a 5s pack with the 5th cell on the side would fit well. Any chance of you giving me the dimensions of the pack in mm?

[sikeston34m]

Originally Posted by lincpimp

I think that they would be perfect for the 2wd emaxx that has the feigao 15l/bk9920 combo in it. I have a hacker 15l smooth can here that will most likely replace the feigao. The truck is pretty light, even with the pair 2200 5s packs. Looks a 5s pack with the 5th cell on the side would fit well. Any chance of you giving me the dimensions of the pack in mm?

These 4S1P packs are 135mm long x 52mm wide.

[othello]

Glad to hear that you like your Sony cells. The smaller 18650vt cells 1100 or 1300mAh can be found in Bosch 36v powertool packs (20 cells) quite similar to dewalt 36V packs (10 A123 cells). To compensate for their voltage drop at the end and to give a more comparable power output to my 10s1p A123 packs i went up from 8s2p to 9s2p.

This is one of my last discharge graphs dating a few days ago.


As you have noticed there is no noticeable real end of discharge. Lipos and A123 drop their voltage heavily at the end. Those Sony cells dont. They are slowly getting weaker and weaker. At the end of my run at some amp spike they dropped down to 18.89V which represents only 2.09V per cell. I start at 37,8V and voltage comes down below 28V (-> 3.1V per cell) with no load. I usually finish driving when top speed becomes boring

[sikeston34m]

Thank you for the info Othello. Looks like you're having some pretty good fun with the cells you have.

So are you saying I shouldn't be too concerned with a LVC at all?

[othello]

I never used an lvc with my cells and they do deliver reliably since half a year (i used them as 4s4p, 8s2p and now 9s2p). But i wouldn't dump them up to the point where your car won't move any more.

[lutach]

Originally Posted by othello

Glad to hear that you like your Sony cells. The smaller 18650vt cells 1100 or 1300mAh can be found in Bosch 36v powertool packs (20 cells) quite similar to dewalt 36V packs (10 A123 cells). To compensate for their voltage drop at the end and to give a more comparable power output to my 10s1p A123 packs i went up from 8s2p to 9s2p.

This is one of my last discharge graphs dating a few days ago.


As you have noticed there is no noticeable real end of discharge. Lipos and A123 drop their voltage heavily at the end. Those Sony cells dont. They are slowly getting weaker and weaker. At the end of my run at some amp spike they dropped down to 18.89V which represents only 2.09V per cell. I start at 37,8V and voltage comes down below 28V (-> 3.1V per cell) with no load. I usually finish driving when top speed becomes boring

I have bought a few Bosch packs and I was wondering why did they add a 60A fuse. Now I see why. I have used my packs and they are really powerful for their size. I will use them more often.

[othello]

I just looked through my logfiles and i'm now at cycle 75 with my Sony cells. Still charging back 2200mAh as 9s2p. When i started using them as 4s4p i charged 4400mAh back. So no noticeable capacity drop. I guess they will have a very long life in my setup. Sikestone: With a driving time of 25min they will last even longer with your setup. I'm discharging mine now in 8 minutes. In my buggy they lasted for up 13 minutes.

@lutach
Guess i use them up to their full potential then (didn't notice the 60A fuse). I red somewhere that each cell has some kind of integrated fuse which will render those cells useless when you overwork them. If you push them too hard the fuse will trigger and the cell is at 0V ... this is not reversible.
Edit: found some pics of those cells open -> link

[lutach]

Here are a few pictures of the smaller 36V pack as well as the bigger one and the PCB that hooks up to the charger. I left the 60A fuse when I wraped the smaller pack.