battery checker

[ericrw]

How do you check the batteries in a Spectrum DX6i and the DX5e for remaining capacity. They are all individual AA size ( 4 in DX6i & 8 in DX5e).   I've got a Battery Checker, which I can use on my batteries that are in a pack but how do I check the individual ones.   There is no indication on either Spectrum T/X, other than a low capacity alarm .   Is there some other type of battery checker on the market that I could obtain ?    The reason for this query is that I have just endeavoured to discharge my DX6i, on my Sigma Charger; not knowing how much capacity was left in the T/X after flying this morning.   On connecting the two together, the display indicated that it was already in the discharged state.(The End).   I assume not low enough, to sound the low capacity warning.     Eric.

[Bruce Richards]

My Dx6i shows the battery voltage on the front screen. This gives a a good hint as to the state of the batteries.

[Garry Pollard]

So does mine. I fail to understand why you are discharging dry cells, I just use it until the indecator on the front screen shows low and then change the batteries. Sorry, unless I am missing something I cannot understand the problem

Garry

[Frank Skilbeck]

Eric, when you tried to do a discharge on the rechargables you've fitted in your Spektrum Tx you do realise that Spektrum and JR use the reverse polarity to Futaba. It you were using a futaba Tx charging jack you would need to reverse the plugs on the charger.

[ericrw]

Garry, I thought it was necessary to discharge the batteries in my T/X as I had only used it that morning for a very short time and yes it was showing 5.5v on the screen, And as I was not going to use it for quite a while I thought it was advisable to discharge for storage purposes.   But as I stated in my thread, the Sigma indicated that it was in a discharged state by flashing "The End" sraight away.    So believing it was in a discharged state, I attempted to charge it to "storage" voltage.    On charging however, it only took 146mah and it was "Full".       I'm using Eneloop batteries rechargeables.     As I'm quite ignorant of electrics; am I right in believing the Charging/discharging for storage reasons is the same procedure as I do for my Lipos.

 Frank,  Yes I'm aware of the polarity difference.

[Tim Mackey]

Normally I charge my packs with 0.5C. I set my delta peak to 3mV for NiMH and to 4mV for NiCd. If you suffer premature charge terminations, increase this value. I would not recommend slow charging ( .05 - .1C rate ) as the normal method for nickel metal hydride cells. This is fine to use for the initial forming charge of a new pack, and should be at the rate calculated above  X 1.2 as there will be inefficiencies in any charge cycle, and you ideally need to pump in around 120% of stated capacity to ensure fully forming. Try this alternative calculation method for the first forming charge. If your battery is 1000mAh and your charger is fixed at 120mA then (1000/120) X 1.2 = 10 hours.

Normally, forming, or slow charging of NiCD is done at .1C and NiMHs even lower at around .05C . However NiMH cells are NOT best charged at 1/10C and leaving them on charge at this rate for long periods will harm them.  NiMH do NOT tolerate slow charging well at all, and will likely overheat and get pushed past their designed maximum charge level of around 1.6V each cell. The only sensible and safe way to charge them is with a proper NiMH capable smart charger, at around .5 - 1C rate and let the charger use either temperature sensing ( if so equipped ) or NDV ( negative delta voltage ) peak detect systems or both, to correctly determine when to stop charging. NDV is notoriously difficult to implement at charge rates below .5C. In an ideal world you should use a dedicated NiMH charge algorithm, with sensitive ( approx 4mv is usually about right ) NDV and remember,  trickle charge rates for NiMH should be lower than those of NiCD at around .05C.

Slow charging NiMH cells causes crystallisation on the plates, and leads to increased "memory" effect and shorter life. As with nearly all batteries,they are best kept at a low temperature before a final charge in ambient temperature just prior to use.