Slow vs. Fast Charge

[Andrew]

Does doing a slow trickle charge work better than doing a fast charge with a fast charger? What is the effect on battery life and performance of doing slow vs. fast?

I have found that fast charging works well as long as it is combines with cycling.
For example, I will fast charge 5 or 6 times, then cycle the battery.

Lawso

[Andrew]

Originally posted by Lawso
I have found that fast charging works well as long as it is combines with cycling.
For example, I will fast charge 5 or 6 times, then cycle the battery.

Lawso

By cycling, do you mean fully discharge and then recharge? Do you perform a slow charge with a wall-wart type charger at all, or just use the same high-ampere fast charger?

[rotorz]

Hi Andrew
Getting the most from your batts is a huge subject but there are some basic care rules that will definately help, but first, what type of batts are you charging and for what use?
Happy Landings

Andrew,
as Rotorz stated, there are different types of batteries out there and there are methods to look after each type.
I will assume that you are using NiCd's (they come standard with most radios).
Cycling is the best way in my opinion to look after these cells.
This can still be done with your wall charger.
First, you will need to flatten your battery. You can do this by applying a load to the battery. One common method is to wire a 6v light globe (for your 4.8v reciever battery) to the battery and leave it connected untill the battery is flat. You can then charge it with your wall charger. You will need to calculate the time required to charge by dividing the charge rate of the wall charger into the capacity of the battery. Ie, if the rate of the wall charger is 50Mah and the battery is rated at 600Mah, it will take 12 hours to fully charge the battery.
If your batteries are not new, repaeat this process a few times to condition the battery.
Once you have conditioned the battery, you only need to cycle once in a while to keep the cells happy.
I personally use a 'smart' charger which does all of this for me!

Lawso

The real problem is overcharging. When you leave a battery on a charger after it's fully charged, the charger continues to send a slow charge through it. This changes the crystal structure of the Nickelic Hydroxide (NiMH) from its beta to its gamma form. This form discharges at a lower voltage than the beta form. The result: after the beta form has fully discharged itself at six volts, the gamma form starts discharging at, say, 5.4 volts. If your Tx or Rx needs a steady 6 or 9 volts to keep operating, this "voltage depression" will shut it down. The Tx or Rx can't use the juice that's left in the battery. Engineers like to call this the "lazy effect".

Also, it is important to note that NiCd is more susceptible to overcharging than NiMH. That is why NiMH batteries are said to not have a memory problem. Lithium Ion batteries are different. They like to be topped off and do not suffer from the same charging troubles. Read a spec sheet for NiMH and it warns "do not leave on charge for more than 24 hours". Read the same label from a LiIon battery and it says "do not leave on the charger for more than 7 days".

The solution: don't overcharge your batteries. Don't "cycle" your batteries (i.e. discharge them all the way) every time you charge them. Batteries that can take a fast charge don't build up the gamma crystals as readily as the "trickle" chargers and batteries. Don't store your batteries in high temperatures and don't charge them until they feel hot. Don't ever discharge a NiCd down to zero volts. This could cause "cell reversal" and even an explosion. Use a refresher that leaves about a volt per cell when discharging. I just ordered a Hobbico Accu-Cycle Tx/Rx battery charger that does this.

crashmaster is right on the button and i was just getting to the
accu-cycle,i have two of these the accu-cycle PLUS.
they have two different models the accu-cycle wich is black,this one has a 15 hour charging time no mather what the voltage of the battery is
where as the accu-cycle plus has a built in voltage meter
that will jump to trickle as soon as your battery is full charge.
so if your pack only needs 20 minutse of charge that's what it gets instaed of a full 15 hour charge.
i leave my batterys on trickel in winter time and cycle once a month and manage to keep my packs in top shape for two years
they might still be o.k but the way i see it is ,a good pack cost about 60$ a small price to pay when a 4000$ bird relies on this completly.

steff