Basic Battery charging help for a beginner please

[bigbadad]

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

[Kopite]

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?

[bigred5765]

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

[jim76]

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.

[bigbadad]

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.

[jim76]

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!

[bigbadad]

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?

[jim76]

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.

[Medders]

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

[bigbadad]

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

[jim76]

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.

[bigbadad]

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?

[JCJC]

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 ?

[bigbadad]

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.

[Rich D]

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.

[Rich D]

As Medders says charge time should be around 40 mins ish

[Rich D]

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.

[bigbadad]

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

[JCJC]

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?

[bigbadad]

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