Formation charges are required for preparing new NiMh packs. You simply charge the pack at a current level equal to 1/10th of the pack capacity for around 12-16 hours. For example, a 1000mAh pack would be charged at 100mAh for 12-16 hours. A 2200mAh pack would be charged at 220mAh. On my Hobbico charger, I use the 250mAh setting. It's not too critical. Just try to get close.
Due to manufacturing variances, all battery cells of the same type are not truly identical. When put together in a pack and charged, some will charge faster and peak early, which will fool most modern peak detecting chargers, leaving the laggard cells in a state of partial charge. Slow charging at capacity/10 allows all the cells in a pack to get fully charged without causing a thermal crisis in the cells that have peaked early. After 2-3 charge/discharge cycles like this, the cells reach a sort of equilibrium, charging and discharging together at relatively similar rates. This is what you are trying to achieve with the initial formation charges. You want all the cells in your pack to peak at the same time, and discharge at the same rate. Once the pack is conditioned like this, you can use the peak detecting fast chargers with no problem.
Cheers,
--Jim
On May 19, 2005, at 10:12 AM, Cameron wrote:
Jim,
What is formation charges? Does this relate to NiCad, NiMH, Lithium-Ion or
Lithium Polymer batteries?
Thank you.
Cameron
-----Original Message----- From: Jim Laurel [mailto:[EMAIL PROTECTED] Sent: Thursday, May 19, 2005 12:46 PM To: Jon Stone Cc: soaring@airage.com Subject: Re: [RCSE] GreatPlanes Triton charger
Jon, Thanks for the tip on seeing total mAh! That helps.
Yes, I set the timer, which goes up to 960 minutes (or thereabouts), which translates into 16 hours - perfect cutoff for formation charges. The downsides to using the Triton for this are:
1) You have to remember to reset the delta peak, or you will fry the next pack you try to quick charge! 2) The Triton only goes down to 100mAh, so you can only do formation charges on packs of 1000mAh capacity or more. It's useless for formation charges on, for example, handlaunch packs.
I keep a Hobbico R/C Multi Charger around, which has current settings ranging from just 25mAh to 500mAh. I use it all the time for slow charging my RX packs and transmitters fitted with 2100mAh NiMh packs. Another plus is that it runs on 110VAC - very convenient! It's a very useful item at just $29.99 new from Tower. Everyone could make good use out of one of these simple inexpensive devices, IMHO. http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXL331&P=7
You can use a timer with it, but the catch is that a small design flaw in the charger allows the pack to DISCHARGE into the charger itself when power to the charger is cut off. I made a few adapters with inline rectifier diodes from Radio Shack that solves the problem.
--Jim
On May 19, 2005, at 6:06 AM, Jon Stone wrote:
Jim,
The Triton is a great charger for the money. There are a few dumb
things about the software, such as the way it erases the total mAh put
into a NiMh cell after it goes into "top-off" mode, but by and large
it
is a very good unit. And again, you can't beat the price.
You can press the right square button after the charge is done and review the Mah the charger put into the battery, before the top-off charge. Same way you can review up to 10 charge/discharge values. Have to do it before disconnecting the pack, or before pressing the left button, though.
I use it for all sorts of cells, including NiCd, NiMh, and LiPo. It can even be tricked into doing a formation charge on NiMh packs by rning the delta peak setting up really high.
Thanks for the trick about forming packs. I had not figured that one out. I had been keeping another charger around just for that feature. I assume you also set the timer to the # of hours you want to charge.
Jon
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