Varta's 15min Charger

[Albinoni]

I know as a fact this battery company Varta (from Germany) have a battery charger for both AA/AAA batts that can actually do a quich charge for 15 mins. Now really sure how good these chargers are or how well will a Eneloop charge in 15 mins. Also will a quick 15 min charge over a period of time ruin a NiMH battery.

Also looks like Varta as with Sanyo and Duracell have also produced the ready to use rechargeables.

http://www.en.varta-consumer.com/co...697702.html&&domain=www.en.varta-consumer.com

Some info on their chargers:

http://www.en.varta-consumer.com/co...ables.html&&&domain=www.en.varta-consumer.com

Further Questions

1. With NiMH rechargeables (eg Sanyo Eneloops) is it best I completely
drain the battery before rechargeing.

2. When charging a battery will the charger automatically switch off so that
the batts are not over charged, or once they're fully charge the charger
goes into trickle mode to keep the levels up.

3. when buying a charger, how long should the very first charge be and how
long with the 2nd, 3rd 4th etc charge.

Thanks

 

[SilverFox]

Hello Albinoni,

If you search for a thread on Cycle Testing Observations, you will understand the ramifications of 15 minute charging.

NiMh cells perform better with shallow discharges. I believe using 60 - 80% of the capacity and then charging will result in the cell having a longer cycle life. However, it is good to do a full discharge every 25 cycles or so.

The charger is supposed to terminate the charge. Keep in mind that some chargers do this better than others...

The first charge should be a 0.1C charge for 16 hours. Charges 2 - 24 should take in the range of 1 - 2 hours. The 25th charge should be a 0.1C charge for 16 hours. Charges 26 - 49 should take in the range of 1 - 2 hours. The 50th charge should be a 0.1C charge for 16 hours... and so on.

Tom

 

[Albinoni]

Hello Albinoni,

If you search for a thread on Cycle Testing Observations, you will understand the ramifications of 15 minute charging.

NiMh cells perform better with shallow discharges. I believe using 60 - 80% of the capacity and then charging will result in the cell having a longer cycle life. However, it is good to do a full discharge every 25 cycles or so.

The charger is supposed to terminate the charge. Keep in mind that some chargers do this better than others...

The first charge should be a 0.1C charge for 16 hours. Charges 2 - 24 should take in the range of 1 - 2 hours. The 25th charge should be a 0.1C charge for 16 hours. Charges 26 - 49 should take in the range of 1 - 2 hours. The 50th charge should be a 0.1C charge for 16 hours... and so on.

Tom

Thanks for the info Tom, now as I'm new to this game I'm bit confused here re NiMH batteries. When you say perform better with shallow discharges do you mean discharging a battery at a very slow rate. Here's an example I am now using Eneloops in all my 3 torches but these orches are not heavily used but more so intermitently. So it will be long time before they get flat, unless I use my torches very heavily.

Also when you say cycle eg 25 day cycle u mean after every 25 days, 35 days etc.

Also re the Eneloops on a full charge would you know how long they last before needing a recharge, say if used in a torch but only intermitently like what I do.

Forgot to ask what would you reccomend for a good charger for the Eneloops but nothing too overpriced. I've got a friend here in Australia who races remote control cars and has a charger worth almost $500 wow !!!!!.

Was looking into the Maha MHC-9000 charger but quite sure if it's ok to use with the Eneloops.

 

[Fallingwater]

There are two kinds of 15-minute chargers.
The first kind are those requiring special cells with a charge control circuit built inside them. Said circuit closely monitors the cell's condition and avoids damage.
Such chargers and their cells seem to have vanished from stores, though. I'm not sure why.

The second kind are those that can charge ordinary NiMH cells. Keep in mind, however, that such a high discharge rate can kill cells quickly. Quality cells might be able to withstand several dozen, maybe even a hundred cycles, but cheap ones can die after a single-digit number of them.

I, personally, charge them slower and put up with the waiting. Having cells ready by the time you finish your afternoon tea is good, but having cells that don't die is better.

 

[SilverFox]

Hello Albinoni,

Shallow discharge refers to the depth of discharge. An Eneloop cell has a capacity of around 2000 mAh. A full discharge would involve using all the 2000 mAh. A 80% discharge, or a shallow discharge, would involve only using 1600 mAh.

The easiest way to work with this is to do a full discharge by turning your light on and noting how long it takes for it to dim down. Now you have the 100% figure and you can go from there. If you run time was 60 minutes, 80% would be around 48 minutes.

Now you can pay attention to a "typical" week of use and figure how long you can go on 80% of your batteries capacity.

If you rely on your light for emergency use, you then have to do a little more figuring... First of all, you need to decide the length of your "typical" emergency. If that works out to, let's say, 10 minutes, then I would suggest charging after 40 minutes of use. This would insure that you always had at least 10 minutes of light available should you be caught in an "emergency" situation.

The final thing you have to consider is the self discharge rate of the cells you are using.

"Normal" NiMh cells that are "healthy," have a self discharge rate of around 0.5 - 0.7% of their remaining charge per day. This means that if you are using normal NiMh cells and don't use your light at all, the batteries will self discharge down to around 66% of their initial capacity in around 60 days. In general, higher capacity cells tend to have higher self discharge rates, so these recommendations should be taken as guidelines.

The low self discharge rate cells, such as the Eneloop cells, have a very low self discharge rate, and unless you are just storing the light, should not have much of a factor in planning a charging regime. You can search for a thread called Eneloop Self Discharge Study, or something like that, for the results of some testing on these cells.

A cycle is simply at charge/discharge cycle. Normal NiMh cells are supposed to be able to perform over 500 full charge/discharge cycles. There are a lot of outside factors that influence this including, but not limited to, charging rates, charge termination, discharge rates, depth of discharge, and storage conditions between use. The key points are charging rate (charge either at 0.1C for 16 hours, or in the range of 0.5 - 1.0C with proper charge termination), charge termination (you have to charge at a "proper" rate to insure a strong end of charge signal, and your charge termination value has to be specific for the chemistry you are using. Charging NiMh cells on a NiCd charger is not recommended.), and depth of discharge. With that said, storage conditions are also important. If you leave your light on the dash of a car in summer with the sun beating down on it, you can damage your batteries in the heat.

I use the C-9000 to charge my Eneloop cells and feel it does a great job of charging them.

Tom

 

[maqsood mehal]

Dear Silverfox. I am a new comer to the Cp forums. Since my Childhood i had great interest in cells and torchlights.Chargers are my passion too. I live in pakistan where unfortunately the La Crosse bc900 is not available.
I will be more than delighted if any of the members who own more than one bc900 or have upgraded to maha 9000, can send me one to my postal address given below,for lots and lots of good wishes.Any kind of mail will do as long as the charger is safely packed
I hope to post replies regularly in future. Thanks to the kindhearted
Maqsood mehal.
648 Raza Block, Allama Iqbal Town, Lahore.
Pakistan. 55750

 

[santza]

I have this varta 15 minute beast which has worked very well, better than I expected! I use varta Ready2Use batteries which are similar to eneloop cells. Works together great! I havent noticed ANY damage to batteries yet.

Varta "eneloops" are considerably cheaper than sanyo eneloops at least here in Finland. I think thats because of varta is kind of company that uses very little money in marketing&advertising=cheaper batteries