pullinteef

iTrader: (4)

After having great success with my Zippy-H "20C-30C" saddle packs (converted from two 3S 1500mah packs) that cost $20 each, I decided to order another pair for the day when the first ones finally need to be replaced. I built the first pack last september and have used nothing else in my B44 since then. I estimate over 200 cycles (of 1500-2000 mah then back to full). I only ever used it to the cutoff maybe twice, and the charger put back 4400. So these packs are underrated if that much was used before the cutoff. I'm still using the original pack, but I can finally feel less punch towards the end of a 10 minute race (hard driving on a mainly 1/8 scale track). Looking at hobbycity.com I could no longer find the original packs I used, but I thought they replaced them with these: http://www.hobbycity.com/hobbycity/s...idProduct=9273

Now they are only $10.95 each plus shipping!!

Got them today along with a few other packs for the e-1/8, decided to take a few pics along the way. It takes about an hour if you're quick, 30-60 mins more if you take your time.
WARNING: Do not do this unless you are very comfortable with soldering (quickly) and li-pos in general. I'd feel awful if somebody did something really bad trying to do this when they shouldn't.

Here's the packs. They are not the same ones I got last time, but it appears they will work. Good news is they are actually easier to separate than last time. Bad news is I don't know if they will have the same excellent performance.



First, if you want to try to re-use the shrink wrap that they come in (I don't have any extra right now, will have to get some) carefully cut the end off the connector side of the pack and slide the cells out leaving a shell.



Remove the power wires and balancer wires


Carefully and as quickly as possible so as not to heat up the cells, remove the bulk of the solder from the board. I found that using an x-acto to pry up the tab while its molten worked the best, but it would usually take 2 or 3 attempts to get it completely free. Let the tabs cool down in between attempts or jump back and forth between the two packs while waiting for stuff to cool. Also, be very gentle with the tabs as they are the aluminum ones that have a solderable tab crimped onto them. If you break the aluminum one, it is a serious pain to connect to anything.



Always tape over areas that can short out with a slipped tool



When you get the tabs free, use a credit card to slowly push down between the cells to separate the sticky tape (was pretty easy with these packs, first ones were much harder)



And then you have three cells



Line up all the pos and neg tabs to connect in parallel



The old packs had longer tabs that I was able to connect, these tabs were too short so I used a little 13g wire tinned.



Interestingly, the label says these packs are matched, and true enough, each cell has a handwritten label that appears to have some capacity testing on it (2 cycles? not sure how they normally match li-po cells)



Anyways, do this for both packs



Wire up your power wires and balance connector:


This was a "quick and dirty" job today, I might go back and clean it up a bit. But tape up the connections really well:


Put some strapping tape over the masking tape:



Slide the original shrinkwrap shells back on or just re-shrink with your own:



Fit is perfect:



They are really small and light, so you'll probably need to add at least some weight (I had made some brass plates and stuck them to the bottom of the older pack):



That's it. I'll report back when I test them out. BTW, They were perfectly balanced even after doing this, (Both packs had the same voltage before I started) Hopefully the "matched packs" mixing won't be an issue.



Again, don't do this unless you are really good at soldering because it is not a really easy job. Way too easy to short out cells or overheat them.

NICK2765

iTrader: (23)

Thats pretty cool

sideways88

iTrader: (34)

very nice. i think i might just do this so i can have some extra packs for my b44. i did not really want to spend 100$ on another 5100mah 35c reedy pack. lol.

20 SMOKE

iTrader: (103)

i toke my maxamps 6,000mah and they were stamped 3200,it was a 2c2p pack and i think they under rate packs to protect the customer from damage during charging

Darrel Smeltzer

WHAT KIND OF SODER DID YOU USE

Choda Boy

Nothing like a good hack to get the creative juices flowing. Verry verry nice!!! Thanks for the guide.

BTY have you ever thought about posting this at hack a day or instructables? there would be a lot of hobbiest liking this.

Keep up the good work

tmail55

iTrader: (61)

I had, until this thread, two WinForce ($29.90 for two shipped on ebay from Hong Kong) 4000 2cell lipo's, that I used a y-connector to make a 8000.

Took about 45 minutes to get them apart and back together.

I thought my 4000 3cell was mean!!!!

This is something else!!!

Though NOT ROAR legal, my local track doesn't hold ROAR races, LET RACE!!!!!!

===

THANKS!! for the warning AND the other safety tips / how-to's for being safe!!

WARNING: Do not do this unless you are very comfortable with soldering (quickly) and li-pos in general. I'd feel awful if somebody did something really bad trying to do this when they shouldn't.

schurcr

iTrader: (6)

Something to think about .... your track may not hold ROAR races ..... but if your track is a ROAR track and they depend on ROAR insurance they're taking a risk allowing non hard case packs. If something were to happen their ROAR insurance may not cover their liability. Hate to see a track close because of something like that.

In an off road vehicle you have to worry more about soft packs being damage from hard landings causing the chassis to flex enough that the soft packs bend and short internally. Seen it happen when a 4wd cased a triple real hard. Lost his pack, esc, and ended up having to replace the chassis.

pullinteef

iTrader: (4)

Oops, left out a small, but potentially important step. After you separate the cells, remove the orange tape and black sticky bars here:



Then carefully fold the corners in and the end up over the folded in corners (did that make any sense?) to shorten the cells as much as possible. Otherwise it might be a tight fit on the B44. You can see the folded ends here. Again be real gentle so as not to break off any of the tabs, they are pretty fragile.

rearviewmirror

iTrader: (17)

Excellent write-up!

A reminder for those who are new to batteries, the electricity contained in these batteries can severely hurt you due to the high discharge rate of lipo. Please do not attempt unless you are very comfortable working with live electrical equipment.

....oh.. about the ROAR approval... Who cares!

Have fun racing, those packs look good.

tmail55

iTrader: (61)

When I raced Nitro off-road I was a ROAR member. AND if my local track went to ROAR membership to race I would be a member again. One of the local tracks has a ROAR membership rule to race there and they are having a problem getting racers to show up.

Some racers don't see the need of ROAR membership or a personal transponder, above the club level!

I have six off-road, two oval and three on-road tracks within a 90 minute drive from my house.

===

I do have a ROAR Approved lipo for racing.

jk racing

iTrader: (20)

Wouldn't you want 2 balance plugs? One for each saddle?

calrosse

I don't think you would. It's not two batteries it is one battery i think you would only need one balance plug. JMO>>>

kufman

iTrader: (6)

Nope, each side of the saddle is 3 cells in parallel so they look like 1 cell to the charger. The two halves are in series so the charger only needs to see "+" "-" and center tap (which happens to be the same point as the jumper wire).

mrmike1294

Outstanding intructable. You did a great job...