How far can you discharge NiMh & other NiMh ?'s

How far can you discharge NiMh & other NiMh ?\'s

a particular voltage? T
Till the LED wont light up any more?

and what is the voltage when charged completly fresh of the charger , then after a little while, then after a week or two (my new 8 pack had 1.3V off the shlef so they cant be to bad about self discharging?

and is this a decent charger ? Radio shack PN #23-345 it folds up like a clam shell and can charge Ni cad or NiMh with a flip of a switch and even do AAA's.
http://www.radioshack.com/product.asp?catalog%5Fname=CTLG&category%5Fname=CTLG%5F009%5F012%5F000%5F000&product%5Fid=23%2D345

It says 5 hours so I imagine it's a timered one. (it puts out 360 mAh at 2.8 V per chanel (I think that would be 1.4 to each battry) by my calculations it would take a min of 7 hours to charge the 2300 from completely dead (prolly longer considering the charging loss's).
I got it for a set of NiMh that came with a digital camera that were 1600mAh. now I have the pack of 8 Energizer 2300's

thanks

Re: How far can you discharge NiMh & other NiMh ?\'

Can't comment on the charger, but if you want the most life out of your cells, change your thinking to recharging early in the discharge cycle rather than how far down you can get the cells to go. Hence the concept of topping off your cells. Use them down only when you have too.

A good smart charger is at least as important as quality cells. If it won't completely charge them, or overcharges them, or overheats them then you'll shorten their life or not be able to take advantage of their capacity. A cheaper charger that isn't up to snuff won't save you - it'll cost you.

Re: How far can you discharge NiMh & other NiMh ?\'

so frequent topping off is good? thats good cause that how I like to run my flash light, any way it'll never will leave me with dead batteries.

I swap my 123's out and into my X-5T when ever I think I am about half way through them in the scorpions or sure fires.

Re: How far can you discharge NiMh & other NiMh ?\'

It's not a smart charger. I wouldn't use it. The 2300s that you just got are some of the best cells on the market (Sanyos). That charger will either undercharge them or overcharge them.

Do a search on this forum for the Charger Shootout and read up on it. If you're gonna use rechargeables then it's worth it to get a good charger. Another very important feature to look for in a smart charger is the ability to charge individual cells, not banks of two.

Their are several good chargers out there. My favorite is the Maha 401 at about $40 and it comes with a lifetime guarantee.

Re: How far can you discharge NiMh & other NiMh ?\'

It's good to top them off IN A SMART CHARGER. The smart charger senses when the cell is full and shuts down to a trickle charge or shuts off. A dumb one is timer based - it'll charge for whatever the timer is set up for. So it depends on what state of charge the cell is at, the charging rate, and how long the timer is for. The chance of getting your cells completely full or not overcharging them is, well - you'd have as good a chance at winning the lottery.

Re: How far can you discharge NiMh & other NiMh ?\'

thanks for th eseach terms... I've been looking for charger recomendation but found none "Charger Shootout" should work alot better.

Re: How far can you discharge NiMh & other NiMh ?\'

Ah heck that was an easy choics the Maha 401 it is I found one for $35

I was going to pay the same fo rth eradio shack smart charger but was leary cause it said it discharges the cell fully each time

Re: How far can you discharge NiMh & other NiMh ?\'

You won't be disappointed in the 401. One more personal tip. When you use the Maha on high setting, use a small fan. Maha recommends using the low setting unless you need the high setting because it is hotter than the low. Lower temps mean your cells last longer. I like to charge mine and be done, so by using a fan I can have both - low temp and fast charge. I usually top off a bunch of cells at the same time. Sometimes mine are pretty full when I charge them, so it only takes 10 - 20 minutes for them to cycle.

Don't worry about "wasting" a charge cycle. The partial charge cycle doesn't "count" as a full cycle. If you're only charging 20%, it'll take 4-5 of those to make one full cycle. Even if it wasn't, if you charged them every day and only got 500 cycles, they'd still last you almost a year and half. Every three days and it's over 4 years. See the point? They will last much longer being topped off often on a good charger rather than deep discharge or a "bad" charger.

Re: How far can you discharge NiMh & other NiMh ?\'

Charger comparison is here:
http://www.crypto.com/chargers/

Re: How far can you discharge NiMh & other NiMh ?\'

Hello SKYWLKR,

To answer your initial question, NiMh cells can handle discharge down to 0.9 volts. Most people stop at 1.0 volts.

Fresh off the charger they are at 1.4+ volts. They quickly (within a few hours) drop to their rated voltage of 1.25 volts.

The self discharge rate varies with temperature, but at room temperature with new cells, you will end up with 50% capacity after 70 days and 25% capacity after 139 days.

These figures are based on a 1% per day discharge rate. My cells in actual use discharge at a rate less than that.

The Maha charger that you ordered is a good charger. I ended up with a Vanson BC-1HU which is also a good charger.

Tom

Re: How far can you discharge NiMh & other NiMh ?\'

I like the vanson being able to charge Cs and D's...

but most of my D and C lights sit for a long time unused. so alkalines stay in them...

I did find the vanson for $25 is the Maha a better charger? it costs more and it only does a class batts.

So I guess the Maha is still agood choice. maybe get the Vanson with D package later...

Re: How far can you discharge NiMh & other NiMh ?\'

Hello SKYWLKR,

I got the Vanson because I use NiMh C and D cells a lot, as well as AA's.

The only negative I have heard with the Maha has to do with overheating the cells during fast charges. I believe a lot of people here use the Maha with no problems.

Tom

Re: How far can you discharge NiMh & other NiMh ?\'

Yes you can discharge a NiMH down to .9 volts, and perhaps lower, without damaging it. The problem is that most devices you power with batteries use several cells in series. Unless you monitor the voltage of each cell, it's very easy to discharge the weakest cell down to zero volts, or even lower (reverse polarity).

Once the cells are broken in, and you use the same set of cells in a device, and charge them as a set, the cells should have about the same capacity, and should discharge down to around 1 volt simultaneously, although I would stop at 1.1 volts, just to be sure.

But newly purchased cells are a problem. Until they have been broken in by a few charge/discharge cycles, they will fool a smart charger that charges each cell independently, and cause the charger to think they are charged prematurely. Most smart chargers detect end of charge by sensing a drop in voltage. New cells often have a voltage drop long before they are charged completely.

The charger thinks they are charged, and switches to trickle mode. Unless you are there to watch how long each cell charges, or measure the voltage of each cell under load, you will probably have a wide variation in the amount of charge put in the various cells.

In this case it is easy to put a cell with 10% charge in series with a cell that has a 90% charge. When you turn on the device, the weaker cell can quickly have it's voltage drop to zero, or less, and be damaged.

That's why I always analyze new cells in my CCrane charger, and run the cells through a few charge/discharge cycles if necessary to equalize the charge in every cell.

Re: How far can you discharge NiMh & other NiMh ?\'

[ QUOTE ]
SKYWLKR said:
Ah heck that was an easy choics the Maha 401 it is I found one for $35

I was going to pay the same fo rth eradio shack smart charger but was leary cause it said it discharges the cell fully each time

[/ QUOTE ]

I have the Maha 201 and am considering replacing it (Buddy's kid put an alkaline in the charger, things didn't end well). Does anyone with the 401 miss the conditioning circuit? I do have to remind myself that the 201 has always done the job for me and there is no real reason to go for the 401.

-Fernando

Re: How far can you discharge NiMh & other NiM

I still have the 204 and never use it. In fact, my 204 is brand new. It was bad and Maha replaced it. While I was speaking with their techs about the problem and getting it repaired/replaced, I asked about the 401.

I was told that even on fast charge, the 401 will keep the cells cooler than on the 204. They claim that their "unique FLEX NEGATIVE PULSE algorithm" eliminates the need for discharging. They convinced me that the 401 was really a major step up from the 204.

What I couldn't do without now is the 4 independant channels as opposed to the 2 & 2.

As I said earlier, I prefer to use fast charge on mine, so just to be on the safe side, I use a fan and the cells get barely warm to the touch. Another little known fact, is that the 401 comes with a lifetime warranty.

Re: How far can you discharge NiMh & other NiM

I don't think it is really necessary to recondition NiMH batteries. I tried it about every tenth charge with some of mine & couldn't tell any capacity change from my control group. I gave up after about 50 cycles (4 reconditions?) using them in my radio. That makes a good test platform since the radio cuts off at 1.1v per cell and I normally run a set down about once a week. Perhaps an abused set would benefit, and I have found it to help NiCads to some extent, done occasionally. My CCrane charger, which which also does larger batteries, will do this if I do want it however. I want another 401 & I gave my 204 to my brother. I think the Vanson BU1-HC (or whatever it is) also does conditioning tho, and it is only $25 if you need it

Re: How far can you discharge NiMh & other

I agree. Most of what I've read indicates that deep discharge actually has a negative effect on the life of NiMHs.

Re: How far can you discharge NiMh & other

sooo...my BB400 drops out of regulation at...1.6v?

sooo...my rechargeables would be draind to 0.8v each?

uh, oh. will i kill the bats?

Bob

Re: How far can you discharge NiMh & other

Hello Bob,

Yes. I believe you will have fewer cycles by doing a deep discharge. If you continue to use your light down to the end of the battery cycle, you would be better off with NiCd batteries. They are more robust than NiMh in deep discharge conditions.

It seems to me that the batteries are good for so many mAh of use. If you have 2300 mAh AA batteries that are good for 500 cycles, you end up with 1150000 mAh of capacity. It seems like you can use it up with short frequent charges or longer less frequent charges, but in the end, you have a limited amount and each time you are using some of it up.

I am not sure that the math works out exactly like that, but it is close.

Tom

Re: How far can you discharge NiMh & other

http://www.batteryuniversity.com/

Full scoop on battery science, care, maintainence. Bottom line: Nimhs like top-off charging and by-and-large don't need to be conditioned often. Really good site.