Yesterday i had two 5AA battery packs made up, $10 each I supply the batteries (2700mh) not bad? So I have a 6 volt charger, that I thought would work, I put one pack on and started it up, no problems, but when they were done, the volts read 7.24volts. So I read somewhere that this should be the case. What are your guys pack volts after charging?
Andrew
That sounds normal. I don’t have the number for my Rx packs, but my 9.6v TX pack goes up to 11.7 after charge.
A couple of points. I’m guessing your cells were NiMH. It is very important that the charger is compatible. If the charger was originally for NiCd cells, it will probably miss the peak charge of the pack and risk overcharging the cells.
Secondly, NiMh cells typically read a higher voltage fresh off the charger, but the voltage drops to expected levels after a minute or so (for our uses- you ought to see how the electric hydro types abuse their cells.:scared:) under normal load. If you test the pack after say running a 6 V flashlight bulb with it for a minute, this should be confirmed.
If your charger is a “normal” one then you might get away with it for a while but I suspect you will either get an incomplete charge from a capacity point of view or you will shorten the overall life of the cells.
A decent peak detection charger for Nimh is a must.
I used to race RC cars and learned my battery management stuff there. In that world you really have to pay attention to the amount of amperage that you get soaked into the cells as well as the peak voltage. If not you could have difficulty making it to the end of the 4 or 5 minute races.
My 5 cell packs all peak slightly differently but theh voltage is generally between 7.7V and 8.2V at peak. It settles somewhat right away and then Nimh lose a bit all the time on the shelf. One of those 7.7 packs will be in theh high 6’s by the next morning and good for most of a full day’s sailing depending on which winch you are using.
If you build new packs with fresh batteries you have to watch for false peaks. Often I find new packs showing good voltage after just a few minutes on the charger but that they have taken hardly any amps. It often takes a few attempts (some times quite a few) with the charge before the pack settles in and then takes a good long soak. Until you get that long soak you won’t get good use times from the pack.
My better Tx packs peak at something around 12.3V but they are all in the high 11V range at peak.
-Barry
here is a .DOC file that I put together to answer such a question on another forum.