Li-Po battery

[Gravman]

Can anyone please explain a little about the Li-Po battery? I have seen a number of different numbers (rating?) and they also have letters,tied to them. They all seem to come with a Dean's connector,not sure why. They need a special charger I am told and they sould always be charged in a fire-proof box. Never charge indoors? Just what makes them so much better than the Ni-Cads? If there is a 101 on Li-Po's I would be glad to attend that class. :)

Grav

[sidneyw]

Battery Education - :)

http://www.commonsenserc.com/page.php?page=battery_education.html

Most airplane and helicopter RC pilots are using lipo because of the power it provides close to or better than nitro or gas.

I use Lipo and brushless outrunner motor on my newly built PT109.

[imgumby]

Fireproof box ?? Only if you can see the pack while charging....non-flammable environment might be a better statement
Most "Battery 101" I've read rightfully insist on never leaving the packs unattended while charging so you can see any problems as they arise (overcharging a pack and it starts to get hot or puff comes to mind) and take care of it before you end up with a flaming mess...same goes for the Lipo Sacks (Sorry Mark W) which may contain a fire... but what's better...seeing the pack start to go south so you can safely stop the charge or wait for the inevitable inside a safe/sack you can't see through??

I ALWAYS charge mine where I work on stuff so I can keep a close eye on them...mostly indoors

FYI..newer lipo cell chemistry's claim to be less flammable in case of abuse...Lipos are not the only flammable battery cell....nixx cells can catch fire and explode as well if abused

Good Luck
imgumby

[jaguar75]

Lipo batteries have been blown out of proportions since the Youtube.com movies of the laptop on fire.The Sony batteries were defective with metal shavings inside the casing causing short-circuits.
Everyone likes to see catastrophes and condemn the products like arm-chair research scientists that most people are.
My lipo batteries hardly warmup during charging and I have a temp sensor that can be used with the charger but only used it once.You can also store the batteries for 18 months with very little loss of charge.They are very compact and lightweight and are wired together with an individual battery balancer plug that can be plugged into a seperate balancer or the multi type battery charger.ThunderPowerRc chargers and batteries are some of the best.I am using these in my Infinity-54 sailboat and Ace radio and will be using them in my submarine build next.http://www.thunderpowerrc.com/
I have blown up a ni-cad battery.Sounded like a bomb!

[PatricMichigan]

My limited knowledge of LiPos seems to indicate that the fire problems have been pretty much eliminated. Having said that- you can make one burn by charging incorrectly. Such as not using a charger designed for LiPos or having a fault with the charger.
My case was a problem with how the balance connector board was wired with my charger: the balance tap plugged in but it was for a different brand of battery and ended up puffing one cell. Nothing scary happened but I was right there while it was charging and stopped it as soon as I saw what was happening.
I'm not sure that I'll use them in a scale boat- but their small size would be helpful on occasion. The majority of the models I build end up needing ballast anyways so it wouldn't really make sense to use a LiPo and add lead.
There is a lot of information in the 'batteries and chargers' section here. http://www.rcgroups.com/batteries-and-chargers-129/
Patric

[boater_dave]

Like any other system, LiPo's have their place. They have great power density, meaning more power for the same weight, or much lighter weight for the same power. They also have much greater capacity for delivering amps. Plus, as jaguar75 mentioned, you can charge them up far in advance of need, unlike NiCad or NiMH. Of course, they are more expensive, too. The price is coming down fast, so it won't be longe before they see much wider use.
I used a tiny LiPo on my conversion of the Revell Swift (http://www.rcgroups.com/forums/showthread.php?t=832333&highlight=swift) because the smallest NiMH pack was still too heavy.

Dave

[Shaun Hendricks]

The LiFe battery's are now out and becoming more popular. They have a slightly lower energy density than LiPo's but they can't explode and don't catestrophically melt down. They also are totally environmentally friendly. Look to see these batteries take over on the medium performance side of the hobby.

LiPo is a dangerous chemistry. Anyone who minimizes that has never had one go nuclear on them. I have after crashing my little flying wing. The LiPo popped out and hit a rock, puncturing it. It immediately heated up and smoked. Lucky it was a small puncture. Had it broke open it would've flamed to temperatures capable of melting steel if they'd stay that high long enough. The chemistry does not mix well with air from what I understand.

I keep all my batteries charging in a custom metal container. Some folks use cinderblocks with ceramic tiles underneath them. That works. The actual issue isn't an 'explosion' per se, they don't really explode but do send jets of rapidly expanding (toxic) gas out from wherever the package breeches. So whatever charging setup you use must be able to contain the heat and jet for at least a few seconds and then be able to evacuate the gas rapidly, so you can't use a sealed container. You can leave them unattended to charge if you have the proper charger with thermal protection. Slow charging them with a heat sensor cut off is the best way to go. My LiPo's don't even get above room temperature at the charge rate my Triton charges them at. Longer = Better. Short (rapid charge) = Risky.

Take a look at my charging box:

http://static.rcgroups.com/gallery/data/500/43646DCP00599-med.JPG

The Triton is in the tool tray that slides in over the PC power supply that feeds it 12v. The posts are 12V and the bottom one is 5v powering the muffin fan on the near side of the box. Note the bulkhead they are mounted to which separates the power supply from the charging area but there is a 1" gap to let air (and gases) flow around the bulkhead so they can be exhausted by the power supply fan. Air flows through the box (cooling everything) as it is drawn in by one fan and out by the other. No battery could blow the box apart as it is not 'sealed' and I only leave the latches on the top while charging, not down 'tight'.

[boater_dave]

What a great idea for a charging station! I happen to have a red metal toolbox just sitting in my shop. Right next to an old PC power supply, as I recall.
I agree with the comment that the chemistry shouldn't be taken for granted, but that goes with any high capacity batteries (NiCad and NiMH included). Energy is energy.
Many years ago I was looking over the shoulders of a group of fellow club guys trying to debug someones boat. It was big, maybe 5 or 6 feet long and powered with a small car battery (liquid acid type). His wiring left a little to be desired and at one point draped a wire accross both battery terminals. The light gauge wire immediately got super hot and all the insulation melted and dropped off the conductor. Thankfully, someone was able to yank the wire off the terminals before anything caught on fire.
I guess the moral is, no matter what you have in your boat, you should be aware of it's potential and take steps to be safe.

Dave

[Shaun Hendricks]

There are more pictures of the charging box here:

http://www.rcgroups.com/gallery/showgallery.php?cat=500&ppuser=43646

It's just a brand new $20 standard tool box modified for the purpose. I cut the top tray in half, riveted the end back on the shorter side and reused the middle part as the bulkhead. I cut some holes out for the power supply fan and plug as well as the intake fan. Installed a free spare power supply and some brass screws with appropriate spacers to play power posts.

The whole box cost me about $30 to make. The charger... not so cheap. :D ;)

[boater_dave]

I have the same Triton charger. Plus I usually cary a pair of MRC Super Brains to charge the basic stuff. I have been carrying everything in a big stackable plastic toolbox. It has three compartments so I can store tx's, chargers, batteries, tools, etc and bring only the sections I need for the day. They all stack the same way.

Dave

PS: sorry to hi-jack. I'll stop now.

[Shaun Hendricks]

I wouldn't call it a hi-jack, LiPo's do need some safety precautions to be used safely. The charging container issue isn't really an optional one if you actually intend to be safe with them.

[jaguar75]

MIT just added an extra ingredient to the lithium iron phosphate battery making process and it will now charge to 100% in less than 10 minutes.They should be in your DeWalt,Milwaukee and Bosch cordless tools by this time next year.You will be able to reconfigure them to your own needs.They also have over 1,000 charge cycles for very long life.Looks like your next new car could be battery electric driving from coast to coast.