[kklee]

I haven't seen any postings about experiences with the new 9V Lithium Polymer rechargeable batteries, so I thought I'd post one.

I bought seven of the iPower 400mAh batteries along with two matching iPower chargers at the end of March from Thomas Distributing. They were ordered specifically for use in headphone amps. I was in the midst of building a couple of Pimetas and a Pint. A friend (Beaglepod) wanted some for his Hornet and SR-71.

I'll lead off with the good, these batteries are incredibly light, last a long time, and since they're LiPo, they don't self-discharge. The batteries have a built-in protection circuit to prevent over charging or discharging.

It all goes downhill from here on.

One of the batteries was bad from the start. It charged fine, but the protection circuit would cut out as soon as any load was placed on the battery. Thomas Distributing was outstanding in that they pomptly sent me a replacement battery without me having to send the bad one back to them.

The Hornet worked well with the LiPo, but not without a serious glitch. The capacitor in the Hornet is large enough that it trips the battery's protection circuit when turning on the Hornet. The power LED comes on and immediately goes out. We found that if you rapidly flip the power switch on/off about 20 times (not exaggerating!), it'll eventually come on and stay on.

We couldn't fit the batteries into the SR71 at all. The batteries are wider than regular batteries and the metal divider in the SR71 prevented the batteries from fitting in at all. We briefly considered de-soldering and removing the metal baffle, but decided that the SR71 was a little too expensive to butcher.

I built two Pimetas, one using 2x9V and the other using 1x9V. The 1x9V Pimeta worked well with the LiPo, no problems at all. When it came to the 2x9V Pimeta, I found that putting the LiPo batteries in series did not work well. The 2x9V Pimeta exhibited similar behaviour as the Hornet. The power LED comes on and cuts out. However, I could never get the Pimeta to stay on regardless of how much I flicked the power switch on/off. It seems that the batteries don't like being in series, probably something to do with the protection circuit. After some trial and error, I found a set of two batteries that would work in series. These worked fine for about 6 charge cycles. Then they wouldn't work together any more. I couldn't find another combination of batteries that would work in series.

I discovered that I couldn't trust the the charge lights on the charger. I found that I had to let the batteries charge overnight to get a full charge.

Another battery has now failed exactly the same way as the first bad one. This was after a few charge cycles.

One of the chargers has developed a bad charging bay. The full charge light always comes on right away or stays on even without a battery plugged in.

It may be that I had a run of bad luck with the batteries I received, but I've run out of patience with trying to use these batteries. I am very impressed with Thomas Distributing though, they have agreed to replace the batteries and bad charger with NiMH ones and credit me the price difference.

 

[jl123]

Good thread. I've been wondering about these batteries. Wonder if anyone else is having these problems. Thomas Dist. is great though. I won't buy rechargables from anyone else.

 

[splaz]

awwwww... I was expecting an explosion.

Isn't that why they have that protection circuit just out of interest ?

I think that's the case anyway, so really it's better that's causing issues than it works fine, then suddenly explodes or burns your hornet to crisp.

 

[ATAT]

kklee thanks about that, I was planning on using some LiPos, I'll probably re-think it or something. Still will probably try though, by how much is the lipo 9v bigger?

 

[kklee]

Quote:

Originally Posted by ATAT kklee thanks about that, I was planning on using some LiPos, I'll probably re-think it or something. Still will probably try though, by how much is the lipo 9v bigger?

I can't give you a precise measurement, they're on their way back to Thomas Distributing. IIRC, they're roughly 1mm wider, .5 mm thicker, and .5mm longer than a standard 9V alkaline.

The Hornet was a really tight fit, getting the battery back out required sharp fingernails and some battery wiggling. The 1x9V Pimeta was in the Serpac H65-9V case. The 2x9V Pimeta used a Bulgin 2x9V battery holder. The batteries fit in both Pimetas without any problems.

 

[kklee]

Quote:

Originally Posted by splaz awwwww... I was expecting an explosion. Isn't that why they have that protection circuit just out of interest ? I think that's the case anyway, so really it's better that's causing issues than it works fine, then suddenly explodes or burns your hornet to crisp.

I totally agree. It's just too bad that the protection circuit is too sensitive.

It wasn't my Hornet anyways

 

[amb]

I recall Ray Samuels had stated that the use of such batteries in the Hornet would void the warranty.

 

[Rescue Toaster]

I doubt the internal protection circuitry is too sensitive... it's probably just right. Lipo has very low internal resistance. Like... a 9v lipo probably has less than 100 milliohms of resistance whereas a 9v alkaline might have a couple ohms. Large high quality electrolytics like the Panny FC have impedances around 18 milliohms...

When you first switch on and until the caps charge: 9v / 0.118 ohms = 76 amps. Obviously there's inductances and a lot more resistances that creep in, but it's not hard to see that you could EASILY trip any internal protection circuitry if it reacts quickly.

Add some series resistance. Like a five ohm resistor, and then use a 3 position power switch. OFF-ON w/ resistor- ON w/resistor bypassed. And it's not like you have to stop in the middle and wait, it should only take the instant as you pass by it to charge the caps up with the resistor. Heck, if you have big caps anyway the resistor could probably be left in series all the time without impact. (If you do this and have two 9v's as dual supply with no rail splitter, put the resistor in the ground leg) Or you could use other schemes with some inductance or something. You just have to get the current down as the power supply caps charge.

 

[beaglePod]

Quote:

Originally Posted by amb I recall Ray Samuels had stated that the use of such batteries in the Hornet would void the warranty.

Charging a battery, other than a NI-MH (inside the hornet) will void the warranty.

http://www4.head-fi.org/forums/showt...um#post1658040

 

[tomb]

This is a good thread. Thank you, Rescue Toaster, for clarifying the protection circuit in the Li-Poly's.

In the Radio Control Aircraft sub-culture, people were on Li-Poly's like flies on you-know-what when they first came out. Super-high mah rates, and lighter, too. What with the new trend toward all-electric (as opposed to Methanol glow plug engines), the Li-Poly's were highly sought when they first came out.

Interestingly, one article recommends this:
"When charging Li-Poly cells you are advised to set the battery pack on an insulated surface and have a prescribed fire extinguisher nearby."

The governing body for Model Aircraft, the Academy of Model Aeronautics, put out the following safety guidelines on 12/16/05:
Quote:

[size=xx-small] Emergency Safety Alert: Lithium Battery Fires (12/16/05) Lithium batteries have become extremely popular for powering control and power systems in models because of their high energy density (capacity/weight ratio) compared to Ni-Cds or other batteries. With high energy comes increased risk in their use. The principal risk is fire, which can result from improper charging, crash damage, or shorting the batteries. All Lithium-battery vendors warn customers of this danger and recommend extreme caution in their use. However, many fires have resulted from the misuse of Li-Poly batteries, leading to the loss of models and automobiles. Other property, such as homes, garages, and workshops, have also burned. A Lithium-battery fire burns explosively at several thousand degrees and is an excellent initiator for ancillary fires. Fire is caused by contact between Lithium and oxygen in the air. It needs no other source of ignition, or fuel, to start. The following is recommended for Lithium batteries to preclude ancillary fires. 1) Store and charge in a fireproof container—never in your model. 2) Charge in a protected area that is devoid of combustibles. 3) In the event of damage from crashes, etc., carefully move the battery pack to a safe place for at least a half hour to observe. Physically damaged cells can erupt into flames. After sufficient time to ensure safety, the cells should be discarded in accordance with the instructions that come with the batteries. Never attempt to charge a cell with physical damage, regardless of how slight. 4) Always use chargers designed for the specific purpose; it’s preferable to have a fixed setting for your particular pack. Many fires occur while using selectable/adjustable chargers that are set improperly. Never attempt to charge Lithium cells with a charger that is not specifically designed for Lithium cells! Never use chargers that are specifically designed for Ni-Cd batteries. 5) Use charging systems that monitor, control, and balance the charge state of each cell in the pack. Unbalanced cells can lead to disaster if the system permits a single cell in the pack to be overcharged. This means that the charging system must provide charge cessation as each cell reaches the proper voltage. If the batteries show any sign of swelling, discontinue charging and move them to a safe place—outside. They could erupt into flames. 6) Never plug in a battery and leave it to charge unattended; serious fires have resulted from this practice. 7) Do not attempt to make your own battery packs from individual cells. Use only professionally packaged and labeled units which contain safer charging features. Lithium batteries cannot be handled and charged casually, as has been the practice for years with other types of batteries. The consequences can be serious, resulting in major property damage and/or personal harm. —AMA Safety Committee Permission for Reprinting or Posting the Emergency Safety Alert granted by The Academy of Model Aeronautics.[/size]

I would say ignore the part about "crashes", but it's a good indication of how dangerous it is to have an unbalanced battery pack.

 

[kklee]

Quote:

Originally Posted by Rescue Toaster Add some series resistance. Like a five ohm resistor, and then use a 3 position power switch. OFF-ON w/ resistor- ON w/resistor bypassed. And it's not like you have to stop in the middle and wait, it should only take the instant as you pass by it to charge the caps up with the resistor. Heck, if you have big caps anyway the resistor could probably be left in series all the time without impact. (If you do this and have two 9v's as dual supply with no rail splitter, put the resistor in the ground leg) Or you could use other schemes with some inductance or something. You just have to get the current down as the power supply caps charge.

I thought about adding a small resistor, but that wouldn't be easy to to do with manufactured amps like the Hornet and SR71 where the switches and battery contacts are integrated into the PCB.

The fact that two of the seven batteries failed pretty much soured my experience with LiPo batteries. I might try them again when some more manufacturers bring them out.

 

[threepointone]

Lithium polymer batteries seem to really need their own dedicated charging/discharging circuit for a specific application. Thanks for the report, I was considering using these in a future project--I guess I'll just stick with NiMHs, then

 

[splaz]

Thought this picture or an exploding/flaming LiPo might be of interest.

 

[ozshadow]

Any idea how standard 245 or 223 Lithium batteries react in a series ?

 

[SiBurning]

Quote:

Originally Posted by kklee I haven't seen any postings about experiences with the new 9V Lithium Polymer rechargeable batteries, so I thought I'd post one. It may be that I had a run of bad luck with the batteries

Thanks for the info.

I bought 6 iPowerUSA nimh 9V batteries and have had trouble with them. Two of them rattled when new, another rattled soon after. Two others wouldn't take a charge for a good while. Two have since died (since December). They often don't charge well. This also happens occassionally with powerex batteries, but not nearly as often. I've also heard from at least one other trustworthy person that they have quality issues. Having said all that, they do last a bit longer than the powerex (when they last at all) having 10% more juice. Bottom line for me: I'm debating getting a few more, and spending the extra buck for powerex and dealing with 10% less juice is well worth it.

By the way, keeping batteries in top shape is nearly impossible. It's much easier to do this with individual cells. The chargers for individual cells hasve conditioning circuits, but you can't do that reliably with batteries because there's no way to get the individual cells to drain consistently. One might go to 0 or negative while another is nearly fully chargerd. I might just skip the 9V batteries and rig something out of individual cells: either 3 lithiums (10.8V) or 8-10 AA/AAA (9.6-12V).

Quote:

Originally Posted by ozshadow Any idea how standard 245 or 223 Lithium batteries react in a series?

Series is always fine, but keep what I said above in mind. i.e. if you buy a premade pack with several in series, they should ideally each have their own separate charger circuit--not sure how they're made. From what I remember, you can put 2 lithiums in parallel. Not sure, so here's a reference: http://www.buchmann.ca/faq.asp