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[bobk]

I’ve just been reading up on LiPo batteries in the Mayhem resources.  I can’t believe how volatile and dangerous these things are.  Loads of LiPo self destruct videos on YouTube

• Charging requires it to be sealed in a fireproof bag, better still in a steel box at the end of the garden.  Needs to be continuously watched whilst charging (even overnight?)
• Overcharge it or draw a bit too much power and it explodes like an Exocet.
• Let volts drop under safety limit and you have a fireball on board.
• Leave it charged, or part discharged, for more than a month and it’s wrecked.
• Banned for air transport from the United States, and banned for recycling.
• You can get LiPo monitor PCB’s, but these only switch LED’s from green to red.  Hard to see in a submerged submarine.

I have a boat application that specifies fitting a big LiPo battery, but Is it worth fitting a hand grenade just to get another half hour of run time or a bit more speed?  Mega concerned. 

[AlisterL]

Hi Bob,

as with all batteries one needs to be careful with LiPos. I use these for my PT-109, my sons boat and in my Turnigy 9x radio.
I charge in a fireproof bag on my bench with the rest of my stuff and I do have a monitoring board that not only changes colour but beeps should I be in danger of over discharging. None of my ESC's are LiPo job's that reduce speed when the battery voltage drops - like the new Mtroniks Tio jobs are supposed to do (never even seen one myself).

As I said above, care is needed with LiPo's but not really that much more than any other technology IMHO. Consider what happens when you over charge or over discharge both Nixx and Pb batteries - these can all be rendered, if not useless, then at least less than nominal. Ever overdischarged a NiCd pack straight from a car battery? They go bang, pop and smoke and possibly you even get flames - been there done that.
With a suitable charger I think most concerns about what happens when charging can be dismissed - my charger has a timeout on it. It stops charging anything after two hours (which is a bit annoying on a large Pb battery). One nice thing about the LiPo's is that you charge a the 'C' rating - almost always means that your battery will be fully charge in 1 hour, with no damage to the battery.

Additionally care needs to be taken to not physically damage the battery as this can disrupt the layers in the battery and cause it to malfunction too.

I have left both my bigger (3s) LiPo's for a LOT longer than 1 month while charged to storage voltage without any concern or problems whatsoever - charge up the next time and away they go.

One just needs to be careful.

For me, energy density, availability and cost outweigh any negatives.

[essex2visuvesi]

My thoughts on LiPos

Get a good quality charger from a reputable manufacturer.

When charging stay close by keep an eye on the temperature, a quick hand test wil do. Also watch the battery for swelling.  If the pack starts to swell or get hot then disconnect it.... don't wander off to the shed
Make sure you use some kind of low voltage alarm on the battery even if your ESC has a low voltage cutoff.  These only cost a few quid and can save you a fortune in overdischarged lipos
Make sure the battery is rated above the Application

I use them myself now in pretty much everything, Helis, my Futaba TX, kids Tamiya RC cars (Tho they are supervised when charging batteries and the packs are "Hard shell")

[BobbyShaftoe]

Are LiPo's really this dangerous?

In short, yes.

But that doesn't mean you shouldn't use them.  A car is dangerous if it isn't used properly but with appropriate training and understanding they become a practical transportation method.

LiPos are safe and reliable if used correctly and you can use them safely with a few very simple rules.

1) Use a balance charger to keep the pack in balance.

2) Never over discharge the pack either by over-current or over-discharge.  If you do it's likely to catch fire next time you charge it.

3) Never keep a damaged (over discharged, physically damaged) LiPo pack.

If you can discipline yourself to stick to the above LiPos are excellent power sources.

If you doubt their safety when used correctly take a look inside your laptop battery pack someday.  Laptops have used LiIon packs for many years.

Even the cost problem with LiPos isn't that bad these days.  Mass production of the chargers and batteries has resulting in the price falling and they're still much more expensive than NiMH/NiCd but within the reach of most modellers now.

[nick_75au]

99 % of those You Tube videos are deliberate mis-handling of the battery by over charging with no safety devices. Why, because it makes for "entertaining" viewing.

I've personally seen Ni-Cads explode in a club members face, and heard a few stories about lead acid batteries causing injury through mishandling as well, including a work mate nearly loosing a finger due to complacency around battery terminals .

ANY BATTERY Mis-handled has the potential to cause injury or property damage.

So my advice is to be aware of the dangers, be informed and enjoy the benefits. Provided they are handled correctly there is no reason for Li-Po to be any more dangerous than other battery chemistries.

Nick

[essex2visuvesi]

Even the cost problem with LiPos isn't that bad these days.  Mass production of the chargers and batteries has resulting in the price falling and they're still much more expensive than NiMH/NiCd but within the reach of most modellers now.

I'm not so sure that's the case now.... it was cheaper to get LiPos for the boys RC cars than it was to get the equivalent NiMh

[Subculture]

I agree lipos are incredibly cheap these days.

You read some accounts of lipos out there, and you'd be forgiven for thinking you were installing a nuclear bomb in your boat!

I agree with the main points being made about using a balancing charger and over discharging. It should also be understood that lipos contain an internal fuse that disconnects the cell should it go under voltage. This is a safety feature built in so if you run them down to far, the pack is just kaput, it shouldn't go up in smoke.

For submarines, you might want to take a look at LiFE/A123 batteries. These are lithium based but a different chemistry, and as such they have a few advantages over lipo's, far less sensitive to over discharge, tough cylindrical casing and very long cycle life.

The trade off is an initial higher upfront cost, a restricted range of suitable chargers, and a slightly lower energy density. The cell voltage is also different on these batteries, 3.2 versus 3.7. Depending on the application that can work for or against you.

Life batteries can be purchased via ebay, Hobbyking etc. Unfortunately not many people selling them here in the UK at the moment.

[john s 2]

I do agree that any battery has a potential for problems. Sadly LIPOs are worse if mistreated. The ability to discharge very high currents and explode are real. How many batteries did Sony recall? Theres  a security film of a laptop burning at a meeting on you tube. So yes used and respected all should be well. But! John.

[bobk]

You read some accounts of lipos out there, and you'd be forgiven for thinking you were installing a nuclear bomb in your boat!

Andy:  Whilst anticipating the realism of K Boat diving characteristics, I did not want to add Kursk 'risks' to the build.

Thanks everyone for the (cautious) reassurances.  I had read up on LiPo’s in the Mayhem Batteries section and became alarmed.  Mayhemers wrote this stuff !

Anything must be treated with respect and due caution, but it would be hard to implode a SLA battery short of using a club hammer or wiring it to the mains.  The same with my NiCads.  I charge them in the boat overnight, they barely get warm, and the chargers turn down to almost nothing when they reach charge.

LiPo’s sound more like fuelling a Space Shuttle by comparison.   

[Subculture]

My Dad has no problem with them (about your generation).

He doesn't like my icharger 106b with all it's fussy menus and options (excellent charger though) and opts to use some very simple little chargers which are a bit bigger than a small box of matches, similar to this one.



They charge at a fixed rate (1A), so you must only use lipos of equivalent capacity or higher unless using lipos which are designed to be charged above 1C, but apart from that you plug the batteries in, and the rest is completely automatic.

My Dad has three of these chargers, and hooks them up to a single 4A power supply, and he can charge all three of his packs at once. Piece of cake!

[cuppa]

I think a lot of the horror stories date back to the early days of modellers using lipos and using inappropriate charging equipment and/or having very little knowledge of how to use lipo cells.

These days the technology has matured and if you buy a decent charger and follow the instructions and also any instructions that come with the battery pack you will be fine.

[john s 2]

Cuppa. Sadly there are always a few who either cant be bothered or think they know better. I know of people who do misuse Lipos. Using normal chargers etc. So far so good. But. John.

[cuppa]

Cuppa. Sadly there are always a few who either cant be bothered or think they know better. I know of people who do misuse Lipos. Using normal chargers etc. So far so good. But. John.

Yes indeed. many years ago, back in the early days of 1/12th scale model car racing, I learned the hard way with nicads. I was using a 1 ohm resistor to charge a 7.2 volt pack and had the pack go bang due to leaving it unattended when I should have been monitoring the voltage. I was stunned by both the magnitude of the bang and the damage it did.

[bobk]

Thanks again everyone.  I started this thread after reading up about LiPo’s on Mayhem, having an application that requires one of these.  I guess it is a bit like Oxy Acetylene welding equipment, OK as long as you know what you are doing, have the correct equipment, that it has been maintained properly, and checked before use.

These batteries are understood to get rather warm.  My application is in a submarine where the LiPo is in a very compact pressure-tight compartment.  It should not be a high current set up, two 12V motors giving realistic (not racing) speeds.  However, if a prop becomes fouled then current may rise.
Extreme caution seems to be in order.

[Subculture]

These batteries stay as cool as a cucumber unless you're pulling quite a lot of current, then they only get mildly warm, no worse than any other battery under the same conditions.

I use them primarily for electric aeroplanes. Typically I use 3S 1000mAh packs and they're rated at 25C. The motors I use tend to draw about 10A at full throttle and about 5-6A when cruising steady. Batteries aren't even warm after a 20 minute flying slot.

[john s 2]

Bob . You have a valid point about overload. If in doubt fuse it out. John.

[nick_75au]

I forgot I had this link, its a long read but answers lots of questions about Li-po's

http://www.rchelicopterfun.com/rc-lipo-batteries.html

Nick

[bobk]

Nick:  Now that was an interesting and informative article.  Although many of my concerns appear confirmed this excellent feature gives detailed advice on how to work with LiPo's in a reasonably safe manner.  Having appreciation for the correct safeguards chargers and balancing methods certainly helps mitigate concerns.  Having ordered a fairly high spec LiPo charger was a good idea.

Although much was made of rapid charging and safe limits for that, I would have thought a much lower trickle charge would be both safer and kinder to the cells?

John:  I am fitting a fuse in the positive line for the battery.  Not sure the best rating for this, but having read the article maybe 1.5 times the "C" rating of the battery sounds reasonable.

[nick_75au]

I don't think it makes a lot of difference to the life of the cells and I believe that the way the chargers are designed it needs the fast charge to be able to measure when to stop the charge, if you trickle charge the measurement circuitry has a much smaller range to measure and can possibly miss the cutoff signal (this happened to me when charging a 200 mAH pack, the charger never saw the difference in amps so just kept going. puffed but no other effect)

My routine is to keep the battery at 3.7 volts per cell during the week or 3, then charge the morning I go boating (this takes less than 30 minutes), when I get home I set the charger to storage charge and the charger will charge or discharge the battery to the storage level depending on how much running I do.

Nick

EDIT, dreaded gateway timeout


In my opinion fuse to just over the maximum load amps, ignore the C rating for your relatively low amp draw, the batteries are capable of considerable current if shorted so the lower rated the fuse the more likely it will blow if a problem should occur.