# A little battery info. LiPO vs. NiMH



## MightyDingus (Jul 31, 2010)

I'm frequently seeing people complain about their lithium batteries crapping out after a year or 18 months or so. What they don't realize, is that this is the way LiPO (Lithium Polymer, the most common type) batteries work. The internal chemistry has a definite shelf life whether it's used or not. After 1.5-2 years, the internal chemistry breaks down and the capacity of the battery gets smaller and smaller. If you leave a LiPO battery on the shelf unused, it's capacity will diminish over time regardless. 

They also have a limited number of charge/discharge cycles they can handle. If you are using your light every night and charging every day, it won't last near a year most likely. The common thought is they are good for 100-150 charge/discharge cycles. Newer chemistries are improving on that, but there is still a limit. 

There's also a big problem with people over discharging their batteries. LiPOs literally become damaged if they go below 3volts per cell. They are not meant to be completely discharged the way a NiMH or NiCD battery can be. A decent battery pack should have a limiter that shuts the battery down before it gets below 3v per cell. Cheap Chinese battery packs don't have this, and batteries are becoming damaged and not lasting because of it. 

The more you use the battery, and the older it gets, the less and less capacity it will hold. This means it'll go from lasting 3 hours, to 2 hours, to 1 hour, etc the older/more used it gets. 

If you have a LiPO battery you use a lot, or is over a year old, it's gonna wear out. That doesn't mean the battery is going bad, that just means that that's the way LiPO is. Most people don't know this. 

I have an older HID light with a Nickel Metal Hydride (NiMH) battery that's 4 years old and has hundreds of charge/discharge cycles on it. It's also sat for over a year and a half without being used. It still has over 90% of it's charge capacity. NiMH batteries are heavier, but much more durable, and generally much cheaper to buy, and safer to charge. The largest downside is the weight due to lower energy density. I'd rather carry a 5oz NiMH battery that'll last me 4-5 years than a 2oz LiPO that might last me 2 years if I'm lucky. That's me though. I ride a 31.5 lb bike, so I'm not a weight weeny. 

LiPO is a 'fragile' chemistry. How many times have you heard of a laptop/ipod/iphone bursting into flames? It's because there's a flaw in the LiPO battery in it. 

They are great for their energy density and 'lightness', but there's a definite trade off in durability, life, and safety. 

I have nothing against LiPO at all. I use dozens of them in my RC stuff. You just need to know what you are getting into, and that a 'battery isn't a battery.'

Please feel free to chip in if you have good info. This is based on my experience and research with LiPO and NiMH batteries over the last 10 years of night riding and Radio Control planes and cars.


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## JohnJ80 (Oct 10, 2008)

MightyDingus said:


> I'm frequently seeing people complain about their lithium batteries crapping out after a year or 18 months or so. What they don't realize, is that this is the way LiPO (Lithium Polymer, the most common type) batteries work. The internal chemistry has a definite shelf life whether it's used or not. After 1.5-2 years, the internal chemistry breaks down and the capacity of the battery gets smaller and smaller. If you leave a LiPO battery on the shelf unused, it's capacity will diminish over time regardless.
> 
> They also have a limited number of charge/discharge cycles they can handle. If you are using your light every night and charging every day, it won't last near a year most likely. The common thought is they are good for 100-150 charge/discharge cycles. Newer chemistries are improving on that, but there is still a limit.
> 
> ...


Your NiMH battery is the exception rather than the rule. If they flat discharge they become damaged. I've done the same thing and they have been DOA after that.

All battery chemistries suffer from age, it's just the rate at which they decline and "dry out".

For what it's worth, I usually get 3 years out of most of my lithium rechargeables regardless of what they are for (bikes, cameras, etc..). They die from age before I hit the charge cycles limit and I tend to charge them frequently.

J.


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## zen bicycle (Mar 23, 2007)

Also Lipo batteries do not sit on the shelf very well if at full charge. If you discharge to 50% before letting them sit over the summer it will GREATLY extend their shelf life. So just don't charge them after your last ride of the season.


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## scar (Jun 2, 2005)

I am going to have to agree with JohnJ80, you should put that Ni-MH in a museum because that is a "one of a kind" for a Ni-MH. I ran Ni-MH with my halogen lights years ago and no matter how mindful I was of keeping it regularly charged and conditioned I was lucky to get a season out of them.

Almost all bike lights use Li-Ion batteries. Li-PO batteries are mostly used for RC stuff. I use/supply Li-Ion batteries with all of my LED lights and have tremendous, even surprising success with them. In fact I am still using my original packs from about 6 years ago and I use my lights about 3-5 times a week, 52 weeks a year! They key is to buy a quality Li-Ion battery from an actual battery supplier, that would mean not some "reseller" or store off of E-Bay. The early failures you read/hear about are usually from someone who has bought a cheap Chinese light or tried to find a "deal" on battery. They are cheap for a reason, they are sub par batteries.

Spend a little extra money up front on a quality Li-Ion battery from an actual battery supplier, it will pay for itself in the long run. That is my opinion on Li-Ion batteries.

On a side note, I stumbled onto the this thread in another forum about making homemade battery packs for electric bikes. Some of these packs look crazy with the amount of cells put together and being carried in a back pack. Go down to post #21 and see a demonstration on how safe Li-Ion 18650 cells are. In the first video, this guy overcharged an 18650 Li-Ion cell then crushed in vise, skewered with a screwdriver, and pounded/crushed/mangled with a heavy hammer. For video #2 he decided he even need to go farther so he took a Li-Ion 18650 cell and overcharged then hyper-charged with V & A, placed it under a heat gun and finally took a torch to it! :eekster: The tester that made the video appears to not have much common sense about him but I think he did a great job on showing the stability of Li-Ion 18650 cells. Now Li-PO I do believe are a different monster but like I said earlier, I have no experience with them, don't really care to, and have no need as Li-Ion's meet and exceed my needs.

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## Carraig042 (Nov 12, 2009)

Li-ion and li-fe are much safer then Li-po batteries. They are more stable and are able to take more abuse. If you stuck a screwdriver through a li-po battery, it would violently catch fire. I too have learned a lot about batteries through the rc hobby. One of the things I see that makes a big difference on the performance and longevity of batteries is a good charger. The cheap wall chargers that come with many light won't do near as good as a quality set-up and they do not have to battery storage option. Storage options on chargers charge the batter to 50-60 percent fill so they will last longer when not used for extended periods of time.






Brett


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## scar (Jun 2, 2005)

^^^^
Excellent point Carraig042 on the chargers also. The cheap "wall wort" chargers that are supplied with the cheap lights are terrible. Once again, spend a little extra money up front and you will be much happier.


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## abelfonseca (Dec 26, 2011)

What decent charger would you guys recommend that wont break the bank?

Cheers!


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## scar (Jun 2, 2005)

^^^^
What type of battery are you wanting to charge?

****


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## abelfonseca (Dec 26, 2011)

Hello Scar, LI ion batteries like the ones the come with the chinese cree xml clone lights.

Thanks


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## Carraig042 (Nov 12, 2009)

Something like this would work good. Really any type of charger like this one would work great. Check and compare features. ALso make sure what you get is AC and not not DC for input. A lot of nice chargers require a powerful power supply.

-Brett


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## ledoman (Apr 17, 2012)

Be aware that some copies of iMAX B6 chargers are also bad quality. At least they are not very accurate. You better go with genuine ones or better yet with ones like Turnigy. If one doesn't care about numbers stuff, charge/discharge/store, different chemistry, ... simple 2S/3S balancers might also work, but I've never tried one.
For external power supply you might use old laptop charger if fit specification. I use some old IBM stuff.

On a single cell side XTAR is good price/performance/quality brand.


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## adr8 (Oct 2, 2013)

Frequent deep discharges and heat are the main reason for Li ion batteries not lasting long. Also if you plan on storing the batteries for an extended period, only charge it to 40%.

Some good info on batteries here Battery Information Table of Contents, Basic to Advanced


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