charging a nimh

[BabyKiller]

ah a post going towards helping me and including many noobs and people who could use this info but for 3v charging power using ya controla go here this should help

http://tinyrc.com/qfm/racing/mod_07.htm#26

[Namuna]

Originally posted by hogjowlz
namuna: i watched an electrical engineer test this with high grade meters and you need at least a 3rd battery to get enough power to charge dual batteries. but anyhow two batteries in the stock controller will not charge a dual battery circuit. if you have a way to do so please explain this.

Care to go into a little more detail?

1. Explain what you mean by 'power'? Since we're specifically talking about voltage, and 'power' is derived from BOTH voltage AND current...I need clarification

2. What EXACTLY was the setup that your EE friend tested?

As I said, a fully charged nimh battery will hold a bit more voltage than the rated amount (like 1.4v for a 1.2v rating, or 2.8v for a dual-cell)...So in this circumstance yes I AGREE that it would take 3 batteries to get enough 'power', IF you're using nimh batteries in the charger...But 2 fresh alkalines (which is 3.0v) WILL charge a dual-cell (IF the charger is modded to put out the FULL voltage)

You also, in another thread, make a good point...These batteries are cheap enough to really be inconsiquential when it comes to how you treat them.

But, I do disagree that you need (or should use) as much voltage as you suggest.

[hogjowlz]

well you are probably right about the voltage if you have fresh alkalines but im not gona change batteries every other day to achieve this(i havnt tested yet). but anyhow he has high grade test equipment. mostly hp(yes the printer guys) meters and a really stable power supply with big analog meters. next time im up there ill take a picture of his bench.

i dont know the numbers but he hooked the power supply up to the controller(no batteries) and simulated two batteries and nothing charged. when he upped it to the equivalant of 3 batteries it charged. i use a 4 battery charger because i already have one. it still takes two or three cycles to achieve a full charge on my dual 100mah nicd batteries. we did this on two cars with dual batts same results on both.

[Namuna]

Originally posted by hogjowlz
...you need at least 4v to charge a dual battery car. a stock controller wont do it.

...i dont know the numbers but he hooked the power supply up to the controller(no batteries) and simulated two batteries and nothing charged. when he upped it to the equivalant of 3 batteries it charged.
[/b]

Okay, where'd you get the 4v figure from? If your friend simulated 2 batts, then 3...Was he simulating alkaline batts (1.5v x 3 = 4.5v) or was he simulating nimh batts (1.2v x 3 = 3.6v)?

Either way, why would you say you need 4v...When your Electrical Engineer friend with all his equipment verified that it was either 3.6v or 4.5v?

In any case, my point ALL ALONG has been to use ONLY enough voltage to get the charge flow going (so as to NOT unnecessarily put undue strain on the pack being charged) and then you can tamper with the current setting to adjust for charge time.

[BabyKiller]

lol u got told

[Namuna]

The intent was not to 'school' hogjowlz, but rather to get proper information and details.

[hogjowlz]

im not sure what the "minimum voltage requirment" is. the power supply has dials on it so he just adjusted to 4.5v from 3v. 3v did not charge. 4.5v did charge but i imagine that you could go under that. im sure 3nicd 3.6v would work but alkaline gives you better range and life. also i dont believe that using even 6v(4aa batteries) is adverse to the battery. it takes about 3 cycles to fill dual batts even with 6v. the way you suggest doing this would take a half hour for a 5minute runtime which is degrading the whole point of these little cars.

[Namuna]

Okay, NOW you're going to get told...

The voltage is NOT what determines how long it takes to charge a battery...The current(mA) is.

You set the voltage equal to the pack rating (plus 20% since the pack charges to higher than rated voltage)...Then how much CURRENT(mA) you charge at will determine how long it will take to charge.

And exactly what do you mean when you say "it takes about 3 cycles to fill dual batts even with 6v"? 3 cycles of what? Are you running that 6v through a Bit Charger?

[hogjowlz]

i use a 4aa charger from an nkok rc boat. it has a 45second charge cycle like a bit charger. the controller my friend hooked the power supply upto was a clone controller.

i know its the amps that matter but with standard controller circuitry its pretty hard to make 2aa batteries dump at high enough rate to make a difference.

my bad if my terminology is off. i dont claim to be an engineer. i just go by what i have seen in real life. you are talking theory and i am talking real usage. weve argued this before "these are three dollar batteries"

if you have an expensive device with expensive batteries (like a 500$ rc car or pda or even your cell phone) i would listen to namuna. but sometimes theres a difference between theory and reality.


anyhow on a lighter note i tested my new rear axle mod last night. once i perfect it i will have a permanent fix for slipping axles and a large perfomance boost. i should have results for everyone to argue over by the end of the weekend and some good vids as well.

[BabyKiller]

lllooolll

[Bunta]

Hi peeps,,

just my .02,,

I tried to charge my 2 cell bit on my controller modified to provide 3v. My car barely ran,, I assumed that my batteries were not strong enough so I swapped in a new set of Duracells (not the expensive blue striped ones). My car barely ran. I would charge the car for 10 minutes,, the car barely ran.

Now who actually did successfully do the 3v controller mod,, and how large are the mah ratings of the batteries in their 2 cell modded cars? How long do they charge their cars for?

In my experience I couldn't even charge (2) 70 mah NiCd cells with the above mentioned controller mod, the car wouldn't run very long (5 sec).

Now I believe what Namuna says about the amperage being more important than voltage,,,, but please tell me what kind of AA batteries produce enough amperage to use in my controller so I can charge a modded car?

My observations support hogjowlz views on this issue,, but hey enlighten us that's what these forums are all about.

-Bunta

[BabyKiller]

well ive seen these green ones but lithium batterys such as a energizer 2 ones are disgned for high mah beacause of camrea flash but these oor regular energizer 2 batterys are good

[hogjowlz]

have you tried them? do they work?

[dieselboy]

i use a 4.5 volt 500 mA ac to dc converter and charge my dual cells for abuot 40 seconds. I only have the dual NiCd mod but i got about 6-9 minutes of runtime out of it.

[hogjowlz]

nice