Lithium battery review completed.Results soon.  By  carasdad (Read 3,672 times)

carasdad, quite a few of us use LiPo batteries in RC airplanes and RC cars et cetera. In that market they developed many special battery chargers designed to charge the LiPo (and LiFe) batteries (plus nicads, NMH and Lead Acid batteries too) that use a onboard computer to sense and monitor the batteries being charged. LiPo's have pretty much replaced Nicad batteries for those uses anymore. The LiPo battery offiers reduced weight, fast charging capability, and longer life and sometimes even a slower self discharge rate too. Another plus is one can parallel LiPo cells and or batteries to increase their capacity and current handling capability.

But due to the high energy storage capability, there is some risk should the Lipo short out for some reason. They turn into Arc welders and can spew out a lot of toxic smoke and the heat causes some of the gasses to ignite into flames similar to a blow torch. The main ways to get a LiPo to catch fire is to beat it up and short it out or puncture it somehow, another way is to overcharge it beyond its fully charged level. The puncture exposes the internal parts to air and oxygen especially which reacts with the chemicals inside causing it to start to fail. Once a Lipo has started to burn, it burns very hotly and too hot for even water to put out.

Beyond that there might be defects in production that can cause the first way to get one to fail to occur. They use a thin cathode and a thin anode material separated by a thin plastic sheet similar to Saran Wrap in thickness. They more or less take all three items and roll it up to make the cells. If during production some defects in the manufacturing process occurs then it can cause the battery to fail later on down the line. This happened a number of years ago with Sony having defective liPo batteries that had metal particle contamination in the manufacturing process. Thus when they make LiPo's they do so in extremely clean room serttings.

But with the modern LiPo chargers, they monitor the cells constantly during charge and charge up the packs reliably without as much risk from overcharging. Now some older chargers where known to have issues if there was a power failure when the pack was charged and they would try to charge the pack again. But more modern chargers have software routines programmed in to protect against it.

The cars and other vehicles that use LiPo or LiFe packs will have some sort of a sophisticated battery charger system built in that handles all the dirty work for you. With cars, using LiFe batteries is popular as the cells don't burts into flames if the battery pack integrety is compromised in an accident that manages to puncture or damage the cells.

Now I normally always balance charge my LiPos. Some guys just charge them unbalanced, but not all cells are created equal and some cells may be more weak and not charge up to peak voltage, thus balance charging deals with each cell individually so you don't wind up damaging a weaker cell in a pack.

But anyway the model airplane people have it all down to a fine art now. The rapid or fast field recharging is a popular method as with Lipos designed for high current discharge rates, the guys will fast charge at the flying field and use the pack right away so it doesn't degrade, thus they can get maximum life out of a battery pack. They all use special LiPo battery chargers for this purpose.

Now then the charge rate is governed by the C rating for a battery pack.
Specs/Terminology
Any lipo on the market is going to have several parameters that determine it's application:
- Cell count. Every lipo cell is roughly 3.7 Volts. Total amount of cells determines batteries total voltage. Ex: 2S = 7.4 Volts; 3S = 11.1 Volts etc.
- Milli Amp rating. Thing of it as lipos fuel tank. You'll see anywhere from 50Mah to 12,000Mah batteries out there. Mah amount directly affects battries form factor, so make sure to measure your battery tray before you go out and buy a 12,000Mah batt hoping to run it for 2 hrs straight.
- Discharge Rating: It's indicated with a small "c", preceded by a number. This number, along with the batteries capacity in Mah is going to determine the max amp output of your lipo. I will elaborate on this later.
- Charge Rating. Indicated with a capital "C", preceded by a number. This number combined with batteries capacity is going to determine it's maximum safe Amp/hr intake when charging.

So if we use a 2S 5,000Mah 40c 5C battery pack for example, it can be charged at up to a 25 ampere rate based on the 5C rating. Convert the 5,000ma capcity to 5 and multiply the 5 times the C rating of 5 and you get 25 amps for its max charge rate. But only do that with a good modern Lipo charger though.
Its discharge rate means it could handle up to a max of 200 amps too. This is where we take the 5,000 and mulitply that by 40 and we get 200,000 ma or 200 amperes.

Now that one fellow's idea about using a higher voltage pack is interesting as the charge voltage would never exceed the alternator's peak voltage. But I don't remember anyone using that before in anything, so I would have to think about it more. But it is a interesting idea though.

Here is some further reading if you are interested:
ref www.rcgroups.com/forums/showthread.php?t=209187

www.ultimaterc.com/forums/showthread.php?t=115264

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

www.maxamps.com/lipo-care.php

en.wikipedia.org/wiki/Lithium_polymer_battery

www.thinkrc.com/faq/proper-lipo-battery-care.php

If not, I'll ask moderators to tell you to stop attacking people, just because they have different opinions than you.
I never mention your name, I never even refer to you in my posts, yet you constantly are whining about me attacking you.
It's not the first time you do this, on the previous forum too.



You'll not have to ask any moderators to stop anything. Since you directly just said I never even refer to you in my posts that sir is just a misstatement and is not true.

When one quotes another as you have done here it is a direct referral to the member's remarks, no other way to put it.

At this point I still see the value in this thread, enough not to merit cleaning it up or locking it and issuing warnings.

Simply put like we say in the south "if you have nothing nice to say, say nothing at all" or I'll edit and lock and do what it takes to restore peace.

JR

Back to where someone stated that they had a battery pack and they used a 12v 2amp trickle charger on it. That pack may have a set of balance modules for each cell built in thaty lets you charge the cell until it peaks out and then stops the charge for that cell. With the huge car battery packs they run several strings of cells in parallel to get the coltage, current and capacity up to what is needed.

I know of a few guys that got the damaged automobile packs from some sources and they took the apart to get at the undamaged cells and built up some battery packs to use in their compeitition off road vehicles. Since the cells have their own built in circuit within each cell, one can charge them like a normal led acide car battery is charged. I think those were those big 12,000 mah cells too. I would not have minded having some of them myself either.

Now some older design car cells did not have the built in balance charge circuit, so you would have to use a charger like they use for RC models to charge the cells with. At present they don't make a advanced hobby LiPocharger that handles more than 48v in series for LiPo packs. But for replacing a scooter battery with a Lipo a three cell Lipo pack should do the trick, you just need to get a big one of around 10,000 to 12,000 mah or so for it.
Maybe parallel a couple of three cell strings together if needed to get the current capability up to what is needed if necessary.

Nice battery, I like that.
Yeah I can see it getting hot jump starting a car too. That likely exceeded its original design specs. But it did make for a interesting test though.

Starting midweek I will be selling these on Ebay. $73.00 with free shipping.My handle there is imskooly. Even after the abuse and torture I delved out to the battery...it is still good as new. Unlike other Lithium batteries that are $150+ and need a $70 charger. These work with a regular charger. If you deplete it to 10.8v or less you get that typical partial engagement of the Bendix or slow cranking. You can trickle charge for a few hours and it will be 100%...or if you are in a hurry you can charge it at 2amps for 10 minutes which will give it about % charge and your scoot will top it off after a few miles of riding.
Glenn