Basic Battery charging help for a beginner please
 

Hi Guys

So i've been away from this hobby for a while (Like 15 years) and have been tempted back......but things have moved on considerably, especially in electrics! So i've got 3300mah NiMH batts and a Ripmax Pro-Peak charger but i'm dissapointed with the batteries perfomance so i wonder if i'm charging them right. They are fine to start with but the performance drops off almost immediately and they don't really last long. So what rates should I be charging and discharging them? I'm currently charging them at 5.0A and discharging them at 0.30A and 1.0V but i really have no idea what i'm doing! Any help or pointers in the right direction would be greatly appreciated. Thank you, Adam

it might be worth checking to see if you have a duff cell in the pack? Unless it's happening for all the packs your using?

i dont think you should be discharging them below 5 volts that wont help nimh cells,

charging at 5 amps is fine. discharge at a high ampage if possible, somewhere around 20A. discharge the cells to 0.9v/cell, so 5.4v for the pack. If you go below this is can damage the cells.

were they new packs or second hand? if they are second hand they they will be a bit dead as NIMH drop off quite a bit after 20 cycles or so.

Thanks Guy's. The packs are all brand new and it's happening for all the packs i've got (three). Jim the maximum i can discharge is 1.00A is this OK? 5.4V is no problem. Thanks.

you can discharge at that rate, but it will obviously take a while! The only problem with the low rates is the batteries can get "conditioned" to give out their power slowly. If you discharge them at a higher rate it conditions them to give out power in higher bursts - apparently anyway!

when you say the discharge will take a while how long do you reckon? Mine seem to be taking about 11mins which doesn't seem that long?

depends how much capacity you have left in the cells. after a typical race mine would take a while on a novak tray at 3amps, even after dropping to 1v/cell on a discharger.
guess you must run yours reasonably flat before discharging.

How long are they taking to charge, at 5 amp I would guess it should be about 40 mins ??

much less than that - at 3a they take about 19mins.

there is definitely something wrong then! Are you sure they are true 3300?

maybe they are old stock that has been sat around for ages and self discharged.

dunno?? They are Ansmann 3300 bought new a couple of weeks ago from Models in Motion, Stevenage.......how can i tell if they are true 3300?

One of me favorites - http://www.csgnetwork.com/batterychgcalc.html

Are they stick packs or side by side, can you check each cell ?

have you thought about using Lipo ?

They are stick packs like these fellas http://www.ansmann.de/cms/no_cache/r...%5Bpid%5D=2721

I've thought about Lipo but know even less about those! I bought this charger with the foresight to be able to charge Lipo but if i'm not having much sucess with HiHM i dunno...........i can't check each cell individualy.

According to that calculator ( good link :) ) About 47.5 minutes from dead flat ( which yours wouldnt be ) to fully charged allowing for 10% efficiency loss.

5A = 5000 ma


You could do with trying a different charger if every pack is the same i reckon.

As Medders says charge time should be around 40 mins ish :thumbsup:

Are the packs warm over every surface to the touch when they have "finished" charging ? Cells give up their extra energy as heat when they are close to fully charged.

Yeah after a 20 minute charge they do seem warm........might ring Ripmax tomorrow and see if they can test the charger. Godamn it - got it of the dreaded 'bay :(:)

Sure if you were to ask around in a local club meeting you would get lots of advice, help on cells/chargers, what car are you using and where do/will you run it?

I've spoken to Ripmax and they think it's because the batteries are new that is making the charger peak early. So they recommend cycling them for 5 charges at a much lower rate. So i'm charging them at 1.5A and discharging them at 1A 5.4V - what do you guys reckon?? At least it's a nice day for it :D