I am fairly new to RCplanes.

I have an older Piranha Digital Peak Charger. I have two NiMH 8.4 V batteries (7 cells) with 1300 mAH, and two with 1700 mAH.

I looked around on the web for charging Amperes, and found all kinds of different answers, some say 10% of battery capacity, others have much higher numbers.

So Itried charging these with 0.2 A and also with 1.2 A. I set the "delta peak" (sensitivy for detecting peak charge to 8 mV/C (milli Volt per cell).

To show the results for just one battery, here is the end charge for the battery, and for how many minutes I could afterwards run the plane at full speed. The battery had cooled down after the run.

1) 208 mA / did not run (why does it not fully charge?)
2) 210 mA / did not run (again, why does it not fully charge?)
3) 1300 mA / ran for 10:22 (ah, that is what I want)
4) 878 mA / 8:30 (why did it not fully charge)

I get similarly erratic results for the charging of the other batteries.

I know it is next to impossible to remotely diagnose this, but when you charge your batteries, do you get very consistent results? Like: charge it for n minutes up to full capacity, and then motos runs for m minutes. It always charges to full capacity.

Is my charger maybe crappy, and Ishould get a better (which?) one?

The only way to diag this is to know if the voltage drops the required amount. If it does then the charger is doing it's job and thinks the battery is full. If not then we can blame the charger or connection. Normally your thought is correct, charge for xx minutes then run for xx minutes and it always charges up to the full mark. This may be a case of :

This battery is problematic on this charger and replacing either component will give good results. If these are subC cells then you can try using 3 amps.

Are the batteries warm to the touch when they haven't charged? Try decreasing the sensitivity of the peak detection- try 12?!<div>
</div><div>Whilst im here on a related matter. Bought an eBay plane. The 4.8v nimh was at 7.2v when I checked it and dropped whilst charging! Any ideas? Cheers</div>

fun4oli what is the V of the batteries

My 4.8v started at 7.2 (itis nixx not lipo!) after charging it dropped to 6v!

strange how it started at 7.2V.
was these new, or had been stored/not used for a length of time.
4.8V is the nominal volt.6V is charged providing they are 4cell Ni**

Came in an eBay plane- presumed old. I have cycled it and it charges, mah goes up, voltage peaks at around 7 then drops to 6.8v. <div>The capacity is about right, but voltage seems high. It blew a receiver of mine so turns out eBay bargain was not such a bargain!</div>

4.8V is a 4cell pack
if it charging to 7ish that would make it a 5cell or over charged 4cell.
If it is 4cell bin the pack and buy new pack.

I know it should be 4.8v that is why I thought it strange. Have cycled it 4times, voltage peaks at 7.3v or so then drops back down to 6.7 once charged. Very strange? <div>It's a new cycle charger, when it reads say</div><div>Charge 1: 400mah</div><div>Charge 2: 440mah </div><div>Etc</div><div>
</div><div>Does that mean the pack is holding 440mah minus inefficiencies do maybe more like 350mah or is this accounted for?</div><div>Thanks</div>

when your charging your putting in what was taking out.
similar to a bottle of pop if you buy 500ml drink 100ml you can only put 100ml back in then it's full any more will over fill. Try and force it in will cause more pressure inside and will need to vent to release that pressure.
To be that high in volts they have been overcharged a few times.
The worst about anyone elses batteries you have no clue how they was treated and will end up costing more than just buying a new in packet pack.
Was you the one thinking about a power supply. i have just modded the ps3 unit. 23.5A 12V delivered to door then modded for less than £10

Yes i am- thanks for the pm. Im on iPhone most of the time and meant to get on computer to reply.<div>So thank you! How much for supply and what was the mod? Thanks</div>

I bought a sony supply for the ps3. 23.5A at 12V. won on fleebay for 99p plus 4-5 quid delivery. bought a inlet socket £2, £3 delivery to plug my printer cable in to power it.
the psu has 4mm connection on the rear, so all the hard work is done. all you need is to link two wires on the rear to trick it into being powered up like the pc psu.
there is also a 32.5 A version same mod.
heres a vid, I have pics but it really is simple
[youtube]http://www.youtube.com/watch?v=gf0jA19SeTc&list=UUADIoM6zmmL-pRNTlAsVKDQ&index=1&feature=plcp[/youtube]

@traxdemax - They are8.4 V batteries

try the peak voltage setting at 5mV per cell, see if that changes whats happening