Anyone tried 9v lipo batteries?

[Wartex]

Anyone tried those? http://www.batteryjunction.com/ipowerus-9v-500.html

[kaptain_zero]

I've not tried any of the 9V lithium cells... I do have a charger for them (it does NiMH and NiCad as well), but frankly, lithium 9V are expensive and I don't have any high drain devices that could make good use of them. In low drain devices they would run longer, but have shorter overall lifespan than Low Self Discharge NiMH units, though the latter are only 200mAh capacity.

I use the Tenergy LSD 9V cells, which batteryjunction sell in 2 packs for $8.99 and they are very good. That's only $4.50 each.

My DMM's all run 9V LSD NiMH and I swap them out every 6 months when I do all the other AA and AAA devices in the house which are also served by LSD NiMH cells. I only have one device that eats batteries, a remote for my set top box, and there I swap out the 2 AA cells once per month as they are dead if I go more than 5 weeks.

Regards

Christian

[Psi]

Voltage is a bit low  8.4V~6.5V

i like my 9V batteries to be 9volts

[IanB]

Although I haven't used 9 V rechargeables, the commentary I've read suggests the lithium ion ones are good and beat the NiMH ones hands down. The main problem with NiMH is that to get 9 V you need 6 to 8 cells in series, and having a bunch of NiMH cells in series is bad news. It's very difficult to keep so many cells balanced and to prevent any single cell being reversed on discharge. A reversed cell will quickly be damaged and will cause the whole battery to fail.

With lithium ion you can have just two cells in series and it's much easier to keep these in balance, not to mention the higher capacity in the same size battery.

This doesn't mean that any cheap and unbranded lithium ion 9 V battery is going to be good, however. You should make sure to buy a good branded product and matching charger.

I think the iPower ones fall under the category of "potentially good".

[kripton2035]

not *that* expensive :
http://www.dealextreme.com/p/9v-6f22-rechargeable-500mah-lithium-battery-white-100988?item=1
and here with two batteries and a charger :
http://www.dealextreme.com/p/soshine-sc-v1-500mah-9v-lithium-ion-rechargeable-batteries-with-battery-charger-123723

but yes 8.4 is too low for me... they should have included 3 lithium elements in it ...
anyway most of the time, the 9v batteries are followed by a 7805 regulator so 8.4 is enought ...

[Psi]

3 lithium cells and a small built-in switchmode supply would be nice.

9V right up until the second it runs flat would be awesome.

[muvideo]

In the last two years I've used some lifepo4 "9V" batteries for my handhelds, I measured the real
capacity of about 160mAh, the self discharge is low, the price not too high, and the voltage
most of the time is between 9 and 9.6V (3 cells, charger tops at 10.5V, deep discharge point 7.5V).
Only thing is if the meter sits unused, to recharge periodically, I check every 3-4 monthes.
I bought them on ebay but now I cannot find them anymore.
Given the "high quality" of the low cost charger I prefer the lifepo4 for these things,
less chanche to burst in flames.

Fabio.

[Zero999]

3 lithium cells and a small built-in switchmode supply would be nice.

9V right up until the second it runs flat would be awesome.

It could include other things such as overcharge/discharge and current limiting. I suppose the problem would be the standby current discharging the battery.

[amyk]

but yes 8.4 is too low for me... they should have included 3 lithium elements in it ...

3 (regular cobalt) cells would be 12.6v fully charged, which is far too high for a 9V battery. 3 phosphate ones will give 10.8v. The manufacturers would rather have people try their batteries and end up with non-working due to low voltage, but non-damaged, than damaged devices.

3 lithium cells and a small built-in switchmode supply would be nice.

9V right up until the second it runs flat would be awesome.

It could include other things such as overcharge/discharge and current limiting. I suppose the problem would be the standby current discharging the battery.

You can get 18650s with built-in protection circuits and those consume a few uA.
http://www.lygte-info.dk/info/battery%20protection%20UK.html
A 160mAh battery would be discharged in around 3.6 years at 5uA.

[RCMR]

If you want a 2S lipo then this is cheap:

http://www.hobbyking.com/hobbyking/store/%5F%5F6520%5F%5FZIPPY%5FFlightmax%5F500mAh%5F2S1P%5F15%5F25C.html

[NiHaoMike]

There was an adapter to put an AA battery and a DC/DC boost converter where a 9V normally goes. An AA battery actually stores more energy than a 9V battery, but you do have DC/DC converter losses working against you. On the upside, you could have the converter output less than 9V if the load would use less power (like if it has a linear regulator) and still operate properly.

There's also the problem of DC/DC converter standby current, but some new DC/DC boost chips have a low quiescent current, like the LT1307 at 50uA.

[BloodyCactus]

i run life packs (6.6v) for my 1/8 nitro buggy. with 9v I would need a balancer. have not tried them on my electronics...

[kaptain_zero]

I just got one of the 9V batteries from DX, same as in the link posted earlier in this thread.  I charged it up in my 9V Lithium/NiMH/Nicad charger and then used one of my iChargers to discharge and measure the capacity. Peak voltage after charge was just over 8.4V, when the battery arrived it read 7.731V on my 87V.

Setting discharge to 0.2A, I got 420mAh by the time the voltage dropped to 7.000V. Continuing on... I ended up getting 484mAh total when the internal battery protection circuit kicked in at ~6.25V At this point the battery reads as an open circuit, 87V shows 0000 when measured.  Placing the battery back into the charger, the protection circuit reset and allowed the charger to begin charging again.

So... if using these types of batteries, there are a few quirks one must be willing to accept.

1. Low voltage vs primary cells. Many devices will be quite happy to run on 6.x to 8.x, but not all.

2. If using the cell until it goes dead, be aware that it goes dead *suddenly* when the protection circuit kicks in.

3. Lithium Ion chemistry is not the best for little used devices. A fully charged Lithium cell will deteriorate faster than one that is partially charged.. So placing one of these 9V batteries, fully charged into a device that has little draw or is not used often will cause the battery to loose capacity faster due to the voltage stress.

4. Compared to NiMH, LiIon has a shorter lifespan and does not store well.

5. LiIon with it's low internal resistance can cause problems should the battery short out by contacting something conductive by accident, and this could result in a "vent with flames" event. I do not know if there is short circuit protection in the internal protection device. All that is mentioned on the battery is that one should not draw more than 0.5A in use.

6. Cell balance. This is an issue unless the internal circuit manages it. Unlike NiHM or Nicad where trickle charging is used to bring the cells into balance, trickle charging is unsafe with Lithium based cells. They should be charged until max voltage is reached and then the charger should stop charging. Some do trickle charge and this simply damages LiIon cells. Balance charging LiIon batteries is done by monitoring each cell's voltage and discharging the highest voltage cells periodically until the low cells catch up, or each cell can be charged separately through it's own dedicated circuit.

For me, too many downsides to switch to this type of cell. Yes, the capacity is nice, but most of my devices that use 9V batteries are very low drain and my 9V NiMH batteries get swapped out with freshly charged ones twice a year, January 1st and July 1st. Easy to remember and no worries if a battery chucked in a drawer shorts out against a spoon or fork. If I used things like paint ball guns or some such, that have high current demands, then perhaps LiIon, despite it's drawbacks, might be the way to go. 


Regards

Christian

[NiHaoMike]

The rechargeable lithium batteries, if they're for consumer use, should have overcurrent protection built in. However, older NiMH batteries have no protection whatsoever and will supply very large currents to short circuits. (Some newer ones have built in PTCs.)

Some devices use the very high current capability of NiMH AAs (and high current NiMHs are still made without PTCs or PTCs with a high cutoff point). Cordless soldering irons often do to get a usable power level. Some older digital cameras would pull as much as 2A from 2 AAs for the few seconds it takes to process and store the image data. (That was back when Flash memory was expensive, so a few digital cameras used hard drives.)