Fast charge question
 

I usually have extra pre charged batteries, or just fly another plane while the charger does its auto thing. I found myself wondering what in the heck are the fast charge rates on some of my packs if I need to know.

A week ago one of my buddies borrowed my charger and had his battery ready in about 10-15 minutes. I use the auto rate on the triton and it takes a while. I will watch the guys fly or fly one of my other planes (trainer) if I am out of pre charged packs.

Is there a general rule for fast charging nicd and nimh you guys use ?
Just for example, nimh 4.8 volt 1500mAh what rate would you charge this at the field ? Or this one nicd 9.6v 600mAh 8 cell ?

I guess what I am asking is there a formula to find the fast charge rate for a battery ?

RE: Fast charge question
 

usually a fast charge is one hour
so your charge rate is the same as your battery size.
however it will usually charge in under a hour because (i hope) you dont run the cells dry.
you could go faster but i wouldnt. if you are useing the plane that much just get a bigger pack.
it's best to slow charge your battery packs, they will last longer (in general)
but i know, we forget to charge them or run them dry at the field.

RE: Fast charge question
 

One hour for a fast charge, ten hours for when you're not in a hurry.

So 2000mah battery charges at 2 amps at the field and .2 amps at home.

RE: Fast charge question
 

Thanks guys, that is what I was wondering exactly.

I normally make a day of it when I go to the field, bring the family and all. Everyone has a good time while we are there. With the exception of events and such or training days, it is unusual for more then 3 people flying to be there at one time. So we all fly as much as we can stand :D I have been seriously considering something like the A123 batteries for anything I may build in the future for this very reason. The triton on auto has it about right for a fast charge the timer usually reads somewhere in the 45-60 minute range when the beeper goes off, I will just continue on with this at the field. At home I will put my discharged batteries on the wall warts all night after flying, then flip the timer on in the morning for a one hour a day pop. (Thanks for the idea Ken)

I cycle about once a month on the often used packs. I discharge to 1.1 volt per cell then trickle them back to tip top shape.

RE: Fast charge question
 

If you want to make your packs last, less than 1C and max .7Amps for a AA cell pack.

A 600ma pack can charge at about .4Amp but the 1500ma pack could be charger at about .7 or .8 amp without damaging the cells with a good peak charger.

If the cells are sub C or larger they can take a faster rate but try to stay less than 1C charge rate.

RE: Fast charge question
 

For what its worth, I've got a stack of fried batteries from over agressive charging. I always though that you could charge up to rate after the battery was cycled on a slow charger two or three times. The last Nimh packs I bought, had a warning on the lable Do no charge over 1000mah rate, and these packs are 2300mah packs. I about lost my first plane when I put a NImh in the transmitter and left it on the charger for a couple days. Out to the flight line and I was showing 11.2V. Two minutes into the flight the battery alarm went off, it had dropped to 8.8v. I had fried two cells by overcharging. I've got a set of 8 individual nicd AA cells for my camera, and I killed them fast charging also.

Slow and easy is the way to go. If you use one of the high capacity packs, it should last all day unless you are a dawn to dusk flyer.

Don

RE: Fast charge question
 

I will second the warning on making a habit of fast charging NiMh cells.

If you MUST do it buy a charger with a temperature probe. You have to avoid overheating these babies.

RE: Fast charge question
 

Battery manufacturers love those fast chargers, keeps them in business replacing all those burned up cells.