Battery help

[Rob (IL)]

I

 

[Critterhunter]

Think 3 cell lipo. I run one in my GT and it's lighter than ANY battery technology on the market. Only problem is it doesn't come in standard AA batteries so I had to wire a small plug inside my GT AA holder, but I can still move that out of the way to run regular AAs if I ever wanted to do that again. Lipos charge in under 1 under and that's perfectly healthy for them unlike nimhs or nicads that that fast is pushing them. Even a lower capacity lipo will have longer run times than a higher capacity nimh or nicad due to lipos holding the voltage high until the very end of the discharge. They also don't self discharge on the shelf like nimhs/nicads, so a year later it's still ready for action. They require special chargers and you should make sure your low battery alarm on your detector kicks in above 9V, because a lipo should never be drained below 3V per cell or 9V total for a 3 cell series pack.

 

[TerraDigger]

"They also don't self discharge on the shelf like nimhs/nicads, so a year later it's still ready for action."

Critter,

Actually, LiPO batteries do self discharge. At a rate of approximately 2-5% a month depending on mfg. The newer generation low self discharge NiMH batteries do not suffer from excessive self-discharge. Example, my 9.6v Powerex NiMH 230mAH high capacity batteries will retain 85% of charge after 1 yr's storage. Sanyo LSD NiMH also have about same self-discharge rate. These Powerex NiMH will fast charge in 2 hours without detrimental side effects when charged by the Powerex charger made for these types of batteries. Just like LiPO batteries that need to use a specific charger.

 

[Rob (IL)]

So would this combo (charger and pack) be a good choice. Weight is the major factor when working with an overweight, poorly balanced detector. My aim is lower weight and better balance using the usual Whites rods for the conversion.

 

[pecor]

Hello Guys, Li-fe battery's are alot safer, Use them if you can. Here is a site I use for my RC plane battery's {Just make sure to us the USA warehouse} for fast shipping. Jay http://www.hobbyking.com/hobbyking/store/__86__85__LiPo_LiFe_NiMH_Battery-Li_Poly_All_brands_.html

 

[Larry (IL)]

If you are going to use White's rods, you might as well use an empty White's case with the battery terminals still intact and you could then use a White's battery holder for the Li Ion's like they did for the AW-2200 pack. You could silkscreen on the side of the case................... White'sLab ........

 

[Rob (IL)]

[size=large]Exactly.[/size] The pack I showed should fit.

 

[Critterhunter]

"They also don't self discharge on the shelf like nimhs/nicads, so a year later it's still ready for action."

Critter,

Actually, LiPO batteries do self discharge. At a rate of approximately 2-5% a month depending on mfg. The newer generation low self discharge NiMH batteries do not suffer from excessive self-discharge. Example, my 9.6v Powerex NiMH 230mAH high capacity batteries will retain 85% of charge after 1 yr's storage. Sanyo LSD NiMH also have about same self-discharge rate. These Powerex NiMH will fast charge in 2 hours without detrimental side effects when charged by the Powerex charger made for these types of batteries. Just like LiPO batteries that need to use a specific charger.

I've never read anywhere that Lipos self discharge. If they did that would be a problem for factories who make and store them because if a lipo cell drops below 3V it's probably going to ruin it. I put my lipos to sleep at a sleep storage voltage level (my charger does it automatically) when storing them for months inside my refrigerator (it's healthier for them). In fact, I just pulled out some plane RC lipos that I had sleeping for almost two years and checked the voltage on them and it's exactly what they were charged or drained to by my charger when I first put them to sleep.

 

[TerraDigger]

Try this link. It's a LiPO battery manufacturer's webpage. I tend to give alot of creedence to what a mfg state's about a product they manufacture. There a numerous sites one can go to that state LiPO batteries do self discharge.

http://www.powerstream.com/li-pol.htm

 

[Critterhunter]

Regardless of if that's true or not, you're talking miniscule amounts of discharge and that's why it's not even considered an issue or talked about in the RC crowd. Never heard anybody voice any kinds of concerns about storage discharge on lipos, while it's often discussed about nimhs. At that supposed discharge rate that would take years to even show in terms of less run time when pulling it off the shelf at 2 to 5% discharge. If my math is right (just woke up and am a bit fuzzy) at 5% that's roughly two years to reach 100% discharge. Don't see how that's possible, because at RC stores I frequent lipos often sit for quite a while on the shelf before they are sold, and a lipo charger will refuse to charge them if the cell voltage has dropped below 3V per cell as that's a built in safety feature on just about all lipo chargers. I know, because I've lost a few electric RC planes in trees that took me a few days to get down. Since the RX was still active they ran the voltage down below 3V per cell, so I had to force feed them via a nimh mode for a few minutes until they voltage was high enough for the lipo charging program to recognize and allow. Lipo technology has got better in terms of tolerance for abuse like this and often can survive a below 3V cell discharge if treated gently to bring it back to life.

As said, I just checked my RC packs that have been resting at the proper sleep voltage for about two years and they are the exact same voltage they were when I put them in my refrigerator. Long term lipo storage is best done in a refrigerator as it slows the aging process, and storing them at the proper sleep voltage keeps them from losing capacity over time as well.

From what I've read on nimhs that are supposed to have long term storage ability they often have less cycle life than normal nimhs and do not hold their charge as well as advertised. I wager a lipo will hold that capacity much longer due to just the share fact about how nimhs cells are constructed versus lipo technology. Also, if you read the specs on the cycle life of nimhs that are supposed to have high C rate capacity for fast charging every one I've ever checked had listed roughly half the cycle life of a normal nimh. In other words, they aren't doing any better at holding up to those vigors as any other good quality nimh will. Regular nimh cells can withstand high charge rates of 1C or more without any real issues, but over time it will in fact shorten their cycle life and lower their capacity. In short, "high charge able" nimhs aren't handling these issues any better than a regular nimh from what I've read by those in the RC crowd who make it a passion to test these sorts of things. Fast charge ability is more of a marketing gimmick then any actual advancements in nimh technology for the most part.

Another bonus about lipos is they are lighter than anything on the market in terms of weight, and that includes lithium ion cells as those are often housed in metal jackets just like a normal cell. That's just one of the reasons why lipos are the most popular battery used in the RC electric plane crowd. Another is that nimhs steadily drop their voltage during discharge, while lipos hold their voltage much higher until the very end of the cycle, providing high prop thrust for the entire plane flight, or providing other devices with more power during the discharge cycle that aren't governed via a voltage regulator. A 1C charge rate (1 hour on a dead pack) for lipos is perfectly healthy and normal, while nimhs and nicads are being pushed somewhat at that high of C and can generate a lot of heat which slowly destroys the capacity of the cells.

 

[stasys]

Battery and charger is OK dont worry , but personally I would buy larger capacity batteries. I use heavy 12V led in the bag.