charging questions

[dieselboy 0]

Hi all, I`m a noobie to this fine hobby, and thus have some questions for you fine folks(a little flattery should get my answers []lol). I have a Duratrax Pihrahna charger and a venom 3000 nimh battery which I have successfully charged once allready @ 0.5 amp, so after that I test drove it in the basement for about 10 minutes and left it for a couple of days. I hooked the battery up to the charger to top it up, and it started counting up from 0mah. So. this is my question, shouldn`t the battery still have some amps left in it? Doesn`t the charger display how much amps(mah) are left in the battery?  Please help this clueless person as I don`t want to wreck my new battery.

[rhenbelz 0]

.5 amps is too low for those packs, even as low quality as they are (Venoms=poo, sorry), you can charge at 3 amps no problem. 4 amps would probably work but don't take my word for it on those. Get some quality cells like GP3300s sometime, those are much better batteries and will charge at 5 amps with no problem. Some racers charge them at 9 amps.

Chargers can't tell how many mAh are in the pack, all the display is showing you is how many are being put in during the current charge.

 

[dieselboy 0]

Thanks for your reply rhenbelz, but to make things clearer for me, the charger has zero delta peak for the fast charge termination according to the manual. So that means that the charger will stop charging automatically when the battery is full, even if the battery was only half drained before I hooked it up, right?By the way, the "threshold" setting is set at 8mv/c as per the manuals reccommendation. Sorry if these are silly questions.[*-)]

[jozza 1]

A peak charger will stop when the battery is full, some are better at detecting peaks than others. If the battery is half full when you start charging, the charger will only top it up (so if the cells are 3000 and you've used them a bit, you can recharge them and the charger will just replace the power that you used).

NimH cells will hold their charge, but it does gradually drop if you leave them charged up, so if you haven't topped them up, then give them a recharge before using them.

You should always charge at around 3-5A or more to get the best out of the cells, recommendation of most manufacturers is to fast charge at 1/10th the capacity, so a 3300mAh cellpack should be charged at 3.3amps, but most people (including me) go a bit higher. I normally charge stick packs at 4 to 5 amps.

The best way to store cells is with a slight charge in them, you should never leave them completely flat. So if you've been running the car, and you are planning to leave the cells unused for a week, give them 5-10 minutes at 3-5A before storing them.

Hope that's of some help to you..

[dieselboy 0]

Well that makes it pretty clear to me, thanks alot jozza (and rhenbelz) for all your help. This is an awesome site and I love visiting it often, very helpful chaps and good info.

[Blacque Jacque 4]

Er......1/10th of 3300mA isn't 3.3 amps, it's 0.33 amps.[Y]

 1mAh = 1/1000 Ah. If you're charging at 3.3amps that's 1C, ie: you'll charge the pack in 1 hr (roughly)

The 1/10th C recommendation is a 10 hour trickle charge.

[jozza 1]

Er......1/10th of 3300mA isn't 3.3 amps, it's 0.33 amps.[Y]

 1mAh = 1/1000 Ah. If you're charging at 3.3amps that's 1C, ie: you'll charge the pack in 1 hr (roughly)

The 1/10th C recommendation is a 10 hour trickle charge.

Quite right, my maths isn't as good as it could be []. The amperage to charge at is the Amps rating of the pack, ie the pack capacity in milliamps/1000. That will give you the amps to set on the charger. A 3300 maH pack should be charged at about 3.3 amps, a 3700 pack at about 3.7 amps and so on.

I charge all mine (3000, 3300 and 3600) at between 3-5 amps, going for the higher value on the better quality packs.

[civilguy 1]

Ahhh, new technology!  I just picked up a Duratrax charger that is a constant 3.5 amps- so decent amount but not too fast.  Works nicely on my 3500 and 3800 packs.

Back with 1200mAh packs, we had 15 minute timed chargers that suggested 4.5 amps for charging!  The cells got toasty!! []  I still have a dozen or so 20+ year old packs that hold decent charge.  And, yes, I still charge them at 4.5 amps!!

Jeff

[Blacque Jacque 4]

Back with 1200mAh packs, we had 15 minute timed chargers that suggested 4.5 amps for charging!  The cells got toasty!! [] 

 Yep, I've still got one of those too, an old Acoms clockwork jobbie. I've invested in a decent mains & 12v -dV Intelligent charger / discharger for normal use. It'll charge my old 1200mAh packs in 30mins, then drop into trickle mode prevent overcharging.

You can actually charge modern cells at anything up to 10C, eg 35 Amps for a 3500mAh pack!!!! [] BUT, you must have a really high quality & accurate charger with a temp sensor to ensure you don't overcharge them and they'll need to be fan cooled too. At those kind of currents a race pack soon turns into a small bomb, especially NiMh, they heat up real quick just after the charge peak.

 

[WildeWillem 0]

Well guys,

Just a question that fits here. I got a new charger but have a question that i cant find in the manual. It is a Graupner Ultramat 14. I can set my delta peak from 3mV till 25mV (Milli Volts). I can set the loading charge and must set the Delta peak level. Any idea how to find out what the correct setting is?

I fond with sanyo for charging 3300 battery pack with 3A the Delta would be 10mV.

What if i want to use a lets say 1A charge. Do i still use the 10mV or do i have to change it?

Normaly if the Amps go down the voltage goes up. Dont now if this works the same way with battery's.

Thanks!

Willem

[Backlash 481]

Hi Willem,

I'm not at all familiar with your charger, but I will try to answer your question about delta peak.

What you first need to do is read your instructions and find out if that delta peak setting is per cell, or Per pack. All of the chargers that I own and have used that have an adjustable delta peak, are per cell, and I suspect that yours will be the same (but yours may be different), and it is quite important as you could overcharge your battery with the wrong settings.

To explain how Peak detection works...When a NiCd or NiMh battery pack is charging, its voltage slowly rises until it is fully charged, (when it peaks), and then the voltage starts to drop, and when the voltage starts to drop the battery starts to go into overcharge, and the cells start to get hot. When we talk about the delta peak (Delta, meaning change) we are looking at the point where the pack reaches maximum voltage (the peak), and then where it changes and the voltage starts to drop. The value you you are setting is how much the voltage drops or how far the pack goes into overcharge before it turns off.

Ideally you want to set your delta peak as LOW as possible. I usually charge my Sanyo 1700 and 2000 NiCd packs at about 8-10mV per cell cutoff. I charge my GP3300 NiMh's at about 4-6mV per cell and my 4200 NiMh's between 2-4mV per cell cutoff. The down side of setting the delta peak as low as possible is that some battery packs may false peak (ie stop charging before being fully charged) especially those that are getting old.. NiMh batteries nearly always have a lower delta peak setting then NiCd batteries do.

I do not change the delta peak if and when I adjust the charging current, but you must change it to suit the battery that you are charging.. However, I do sometimes lower the delta peak setting on a hot day so the batteries will finish charging a little early, and wont get to hot from the charge.

Goodluck.