testing batt packs?

[Reckless]

anyone out there know if you can test a batt pack for it's MAH? is there some silly expensive tester I need to try and find?

I've got 4 'cheap' ancient 6 cell packs for my PT boat till the brand new 4500 packs show up (stupid international mail!) .. I'm just wondering what their current MaH rating is as they aren't labeled more then being a 7.2 'racing' pack

something in my head kinda curious as to how much more run time I'll get with the new 4500 packs

at the moment with 4 of these packs I'm getting near the same run time people with 2 of the recommended 3300 packs LOL .. about 10-15 mins WOT or near it.. then another 10 mins or so of 'half throttle' just to run the packs down

[Ghost 2501]

find a something that takes 1 amp, (light bulb, motor etc), and hook it up, turn it on and time it.

if you run for 1 hour its a 1000mah

[mfr02]

A 1 amp voltage regulator with a 5 ohm resistor rated for more than 5 watts connected acrossits out put will draw a constant 1 amp. Keep measuring the battery voltage until it has dropped to the minimum you can stand, while noting the time. The length of time in hours times the current in mA gives the mAH rating. Perhaps a resistor of 10 ohms for 1/2 amp would be kinder, but would take longer.

[Stu :)]

You can do the same thig as above if you already have decent 'smart' charger.
Set it to Discharge at one amp and go away. When it beeps come back and look at the time lapse and calculate the amp rating from there.

But the above work just as well if don't own a fancy pants charger.

Stu :)

[green-boat]

There are a number of fancy chargers out there but I like the Triton chargers. I have two of them and they will just about charge any kind of battery out there. they will tell you how much you pull out of a pack (discharge) and how much you put into one (charge). http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXMAJ0&P=ML One nice about this charger is that it will cycle your batteries up to 10 times and give you a report.

I just recently brought 2- 3000 NiMh backs back from the dead after a few cyclings.

[Shaun Hendricks]

One note about testing MAH. The inexpensive manufacturers test the packs by pulling less than 1 amp, sometimes down at .5 amp to get those high numbers. Some of the higher quality manufacturers actually test under rated load to get MAH. Those are rare though and you PAY for that. So, an inexpensive pack, under a real world load might only do about 70-80% of its rated MAH.

A pricey pack should do near the full amount under a real load.

[Reckless]

ah I think I'll just live with not knowing LOL.. the charger I've got has got a bunch of options I know nothing about .. but I don't wanna mess with anything cause well... I don't have instructions for it! LOL

I have to talk with the guy I bought it off of on Sunday anyways (came with the springer .. which I stole the current batt packs from ;) ) ... it was more a curiousity then anything .. I don't wanna buy a new charger just to confirm that I already knew the batt packs were crap LOL

as for the packs I am buying .. they aren't extremely expensive.. but they are kinda on a deal for 2 of $60 US.. plus shipping.. basically a 2 for 1 clearance thing... I think they are normally like $75 each... so I'm taking the jump now and getting 4 ;)

but yeah I have amp and volt readings/settings on my charger.. I just gotta actually find out how to set/use it properly (which I should have done over a month ago! )

[785boats]

Does your charger show the the number of Mah taken on by the battery at the end of the charge cycle? If it does, discharge the pack to no less than 0.9v per cell under load, that's 5.4v for a 6 cell pack. I use a 700 motor with an 8 x 6 aircraft prop on it. I run it full throttle until the voltmeter reads 5.4v, cut back to half throttle, wait until the voltage comes back down to 5.4v, cut back to quater throttle & when the voltage drops to 5.4v again I switch it off.
Wait for the pack to cool down (if it got warm) then charge at 1 amp.
At the end of the charge cycle read the Mah display. That should be pretty close to the rated Mah rating of the pack. If not when new, certainly what it is now.
If your charger can be set to a discharge/recharge cycle, do that. It just takes longer. My Swallow 2 charger only discharges at 1 amp.
If your packs are already half or three quaters discharged from a session at the lake it won't take so long.
Do all 4 packs the same & write down the readings to see the difference between them.
All the best.
Paul.