Charger Questions

[Crom]

Hi,

Just wanna say that this is a nice new look to the forums.

I’m planning on building a stand-alone charger for my bit, and I need to know what current and voltages and how long it takes to peak charge my bit.

Currently I only have a stock bit, but information on dual batt and NiMH batt data would be nice as well

Thanks 🙂

[GT-ahh]

with my dual NiCd i use four AAs in series 6v and charge for 90 sec – 120 sec…

[Crom]

GT-ahh, do you use a charger port from the Tx or did you rig up something else?

[DaveF]

QFM have a schematic for a charger, but it really depends on what batteries you have in there. Call Battery World in Aus and tell them what batteries you have to charge, and ask what’s specs for a charger to use to recharge them at the fastest rate. Then you’ll know for sure.

[Crom]

Calling Battery World… Thats a great idea… Didn’t even think of doing that… was just doing a lot of net searching on NiCad & NiMH batts… big headache…

I’ve seen the charger on QFM, but I wanted to build it without sacrificing my controller. Also I was thinking of desiging a timing circuit with variable timing. (Variable resistor, capacitor and a couple of transistors?) Perhaps also with variable current and voltage (this might be harder to do.)

[GT-ahh]

i removed and attached the charger port to a 4battery holder..

[Crom]

Okay, that won’t work for me cause I wanna keep my controller intact.

I was thinking that if I measured the dimensions properly, and got it it right, I could use some sort of screws in a bit of plastic to provide an electrical contact to the bit.

I don’t think that I need the side clips if I do this properly, because the screws are not springy and the only reason you need to have the side clips is because the Tx charger prongs are springy.

[GT-ahh]

yeah i was thinking of making one with 2 small nails stuck in a piece of board then the bit just rests on the nails…maybe someone could incorporate one of thes in a pit lane. Then endurance races would be all the more possible…

[Crom]

I read about someone thinking of doing that, but also by modding their bit (adding blobs of solder on the bit so that the contacts protrude out) and have some sort of rails to supply charge.

Was wondering if any one had a K.I.T. kit? Are the chargers compatible?

[Lazboy]

from what i understand kit chargers are compatable and from what i read on these board that there is some kind of SUPER kit charger ( stand alone sold sep) but i have never seen one

[Craz]

Do any clones have a charger port that fit a
Char-G, or does anyone wanna sell me a cheap remote with the charger port intact.

Thanx

[Admin]

Ok have to echo Croms question, I need to know what current and voltages and how long it takes to peak charge my bit.

PRabbit build a AC Charger and I would like to use his idea but be able to charge several cars at a time and also charge normal bits, NiMH bits and Dual Bits. My biggest question for you EEs out there is how does the voltage affect the charge. the bits are 1.2v and 2.4v but the controlers are 3v (reality about 2.1 or lower). I have a variable voltage DC Charger which does 1.5-12V at 300mAh I also have 2 other at 4.5v 800mAh and 6v at 600mAh which one would work and for which car?

[micro_Amps]

K.I.T (Bit) racer chargers are not really compatible, the pins are different. Char-g pins are side by side and KIT pins are one in front of the other. The KIT racer charger could probably be chopped up modded, but you would probably have more luck with the nail idea

[micro_Amps]

These are my thoughts on charging Bits.
Any DC power supply or battery pack can charge a Bit’s battery so long as its voltage is above the voltage of the battery you are going to charge, within reason. The standard bit for example charges at 2.8v @ 300mA for 45 seconds. You could charge the same battery at 1.6 volts (and much lower current) but it would take 16 hours. Alternatively, you could charge the same 1.2v battery at 5v (at approx 600mA) in half the time but this will heat up the battery and kill it quite quickly. The more you heat a rechargeable battery whilst charging, the fewer amount of recharges it will take. The ideal is low current, longer time charging but this is not the best for us, so a compromise must be reached.The way tomy designed the charger is not the absolute best for the battery, but it does a good enough job for a toy application.
If you take the charging figures from the original cell, you can expand it in to figures for 2 or 3 cells, eg
1 cell (1.2V NiCd) charged at 3v takes 45 secs (or lets say 1 minute.)
2 cells (2.4V NiCd) charged at 6V will take 1 min
3 cells (3.6V NiCd) charged at 9V will take 1 min the charging current should be the same in these 3 cases, all at about 300-400mA ,which is high for a standard application, but quick and that is what matters most to us.
But alot of us are using NiMH cells with a 150mAH rating and our rule of thumb has been to double charge (ie 2 X 45 secs) to charge these.
So going on that theory–
1 cell (1.2V NiMH)charged at 3v takes 90 secs (although 2 min makes for a better charge)
2 cells (2.4V NiMH) charges at 6V takes 90 secs
3 cells (3.6V NiMH) charges at 9V takes 90 secs
Again the charging current should be the same in the above 3 cases
NiMH cells ‘should’ be charged at lower currents than NiCds but it doesnt matter here.
So you can see a pattern of ‘multiples’ emerging that can be used as a guide to how to set up a custom charger. It is not necessarily the way a Nicad purist would do it, but then we arent sending shuttles to the moon here we are just trying to shove some electrons into a toy.If you wanted to charge quicker than above you could increase the charging voltage and shorten the time but if you go too high with charging voltage the cell will heat up, hiss and die.
So a dc power pack or charger (or a battery pack) with a voltage rating as above and a minimum current rating of about 500mA should do the trick.
You could build a multi charging station with 3V,6V and 9V selectable for 1,2,& 3 cell Bits and have a timer switch for 1 min or 2 mins depending on whether you have NiCd or NiMH cells in your car. That would cover all combinations of Bit charging, you would just need to mount the whole lot in a box or something.

[Impreza]

Hey guys, the K.I.T charger isn’t compatible with the bits. And almost all of the clone chargers will accomidate the bits as well. So buying a cheap clone and hacking apart the controller to use for your bit is the best idea, imo. I think Crom’s idea with the rails would be very cool in principal. GT-ahh are you thinking of doing a mini LeMans like race:)(the car mods alone would be very cool). Thanks for the info micro Amps.

[Crom]

micro_Amps: Thanks for the rules of thumb! Although I do have a question. I have heard that TOMY’s design does not fully charge the stock battery. And that double charging actually is better for the stock battery because it brings it closer to a “peak” charge. (Qualitatively, a double charged stock battery seems to be “zippier” than normal and lasts for almost 10 mins.)

So my question is: Does doubling the rule of thumb values provide a closer peak charge? If not, how do we determine a peak charge? (Without owning a really expensive battery recharger?)

[Crom]

Impreza: I can’t take all the credit for that rails charging idea, like I said I saw something that was on the web with that idea. So its not all my idea.

However, to extend that idea a little. You know how a bit will still work while charging? (You press forward while the bit is charging and the wheels turn?) Does anyone know whether doing things like running a bit while charging will hurt the battery?

Images of having a bit roll into the pit (rails charger of the correct lenght) and roll straight out fully charged without stopping are dancing in my brain.

[micro_Amps]

Crom a double charged battery is ‘zippier’ because it has been held at a higher voltage (or charged) for twice as long and once disconnected the output voltage is higher too and can push out more current because of this slightly higher voltage. In answer to your question, yes doubling these time figures will make for a better charge and therefore longer run time but how long do you want to waitfor it to charge. The best compromise for us is probably to do the NiMh battery mod and charge it for 2 mins at a time and get 15-20 mins run time out of it. You could double charge that too if you dont mind the wait.
Double charging is worthwhile but just takes too long. Its a pity the battery is not removable and we could keep 1 or 2 on charge and put them in on a pit stop. One thing we could do tho, if you had an extra charger setup you could leave a car on charge, but it would need to have a mini on/off switch installed somewhere on the car to turn the radio receiver off when charging.
In order to determine ‘peak’ charge you would need a ‘smart’ or ‘switch mode’ charger which determines the batteries ability to accept current and charges accordingly. NiCds develop a memory, NiMHs not so much but a smart charger would sense charging current and charges the correct ammount. The way to fill a battery cell properly is to charge at 10 to 15% higher voltage than the cell voltage, monitor the current when cell is first connected to the charger, when charging current drops to about 1/10 of the original charging current the battery is ‘fully’charged. This may take hours tho, depending on the cell’s capacity (mAH) and is getting too technical for our situation. We use a charge voltage many times higher than the cell we are charging that is why it charges so quickly but it is detrimental to the cells ‘health’ but so what,… its quick.
But yes, double charging will store more power into a single cell (and give a longer run time) but because the charge voltage is so much higher than the cell voltage it will lead to an earlier demise for the cell being charged.

[micro_Amps]

Running a car whist on the charger will only result in less charge ending up in the battery. The controller charger can deliver more current than the motor uses whilst running, it wont make any difference to the battery. The battery will just be under charged

[Impreza]

Sorry about that Croms, but it still is a great idea whoever thought of it. I wonder, does anyone have one of those (for lack of a better term) cheap slot car tracks that run on batteries instead of being pluged into the wall. What voltage are they set up for? and could it be modified to do the job we want it to, ie were the batteries on the track or the speed controller? You could loop wire underneath the track piece to complete the circuit and build up the pit lane on both sides of the plate to keep it flush with the racing surface. Mod the car bottom, maybe add a on off switch on the plate to save bats and presto??? I guess you would have to slightly raise the rails on the plate as well.

Impreza :smiley16:

[Crom]

Thanks for the extremely detailed notes on batteries micro Amps!

I guess that I was thinking too big for what I’d be able to accomplish. I think I’ll be able to come up with a timing circuit for my charger.

Just a thought… (more like another brain fart) IIRC As long as the battery isn’t generating heat it is still capable of storing charge.

If I pull a spare NiCad from a K.I.T. set and do some experimenting, say set a 1 minute charge, then start playing with voltages and currents to see which would just make the battery warm, then back off an arbitary amount on the voltage and current, and then I’d be close enough to peak charge… right?

If I could secure a few NiMH and do the same thing? When I have the money and time to invest in this…

[Crom]

Impreza, sounds like quite a bit of work involved… I was actually thinking something along the lines of using some non insulated wire strung across two nails or screws as each rail and just adjust the height of both rails above the track surface. This added to the solder contact blobs on the car would allow you to drive on, drive off. But gotta be careful of stray pieces of metal shorting the wires this way tho.

[micro_Amps]

Crom, some answers to your questions……
If the battery being charged is not generating any heat then it is being charged VERY gently (and slowly). All NiCds and NiMHs generate heat when being quick charged. The Tomy controller starts to heat a standard N50AAA battery when you do a “double” charge. The heating is unavoidable in quick charging. So the answer to your first question is yes (when quick charging) if it is still cool it is not charged.

A spare KIT battery is the original N50AAA NiCd. You wouldnt have to worry about controlling the charging current, the charging voltage determines this.The higher the charging voltage, the higher the current being forced into the battery. You are right tho, if you charge at a certain voltage for 1 min and the battery is VERY hot then this voltage is probably too high (warm is ok tho) At 3V charging the N50AAA will start to warm after about 90 to 120 secs. So I would think that charging at about 5V could charge the battery (and warm it) in about 1 min, but I’m guessing.
The NiMH will take longer to charge because of its increased capacity, so if you want to charge it fully in the same 1 minute time you would up the charging voltage(which ups the current), maybe 7V, again I’m guessing but you see (I hope)what I’m getting at……
more volts = less time to charge but more heat!! (and lots of heat is bad)so a compromise must be reached.
Having said all this, the hotter you go in charging, the less life span your battery will have but they can be charged quite quickly if your not concerned about longevity. Also be careful, this battery is charged in the car which is PLASTIC and prone to MELTING, you get my drift. Also if you are charging and warming the battery, the battery will hold a little heat from the previous charge, which may accumulate and again you end up with a molten BCG. I have seen large NiCd packs charged so quickly they hiss and when charged you can barely touch them, they go like stink, they just dont last very long.

Let me know how you go, I’m planning on doing some “ideal charging figures” of my own for the various configurations of NiCd and NiMH cells. PM me or post the results or both.

P.S. Impreza, love the slot car track charging idea. Drive on when not quite fully flat, wait a minute or two, and zoom away…excellent.
You would probably need guide rails on both sides to direct the car to exactly the right spot over the charging rails. Oh, and dont park on the rails for too long, you’ll melt

PPS Sorry about the huge posts, I rabbit on a bit.

[Impreza]

micro Amps, yes and yes. You could mod. the corner guide rails (plastic ones that usually come with the slot car tracks) to bring your car in straight. Or if the charging rails are slightly elevated they may guide you car in, just make sure the tyres are on either side of the rails when you drive in;) An on off switch on the charging plate would be the best to avoid any pit fires:)

Thanks for all the charging info.

Impreza :smiley16:

[Crom]

micro Amps: You are a fount of knowledge. Thank you for all your help. (btw, I’ve heard that story about the poor guy who charged his bit for 5+ mins at 3 volts and melted his bit.)

I probably won’t be able to get around to doing some experiments for a while… I’m back at work already so getting the time to do this is an issue…

Impreza, that pit is starting to sound really good… if only I had the time and skills.

[Impreza]

I hear you Crom:( Maybe eom (end of month). I think I would try the pit lane on a clone first… Just in case, lol.

Impreza :smiley16:

[jamiekulhanek]

Microamps….finally somebody who has the same idea as me…..i rigges up a constant current charger (just an LM317 and a 5W 5.6 ohm resistor) and it works great, takes 15-20 mins to charge, but it gives you great runtime. 20 mins sounds alot, but it really isnt, you chuck it on, do something else for a few mins and voila!
I hate the idea of battery-battery chargers, and you physicall cannot charge a battery in 45 secs.

The world is mine

[jamiekulhanek]

A peak charger wont like charging your bit, because the Rx is always on. This constantly draws current from the battery, and the peak charger senses this and is convinced that the battery is faulty.

The world is mine

[jamiekulhanek]

Le Mans….id love a 24 hr bcg race, it would be so interesting to see what happens, and if any of the cars finish.

The world is mine

[micro_Amps]

Jamie, Yes, Yes and Yes. Your last three posts are spot on.
LM317K is perfect for small battery charging. With a pot instead of resister charge time (voltage) can be varied.
Re peak charger: you could install a micro on/off sw to take the Rx out of circuit, but 1.2v 50-150mAH is too tiny to worry about peak charging. I see you also share my dislike of batt-batt charging.
24 Hr race (LOL) Id like to see how many drivers finish, the cars would probably go the distance.
Has anyone ever done distance trials anywhere in the world???:DuA

[Impreza]

I would like to know what the longest continuous run on a bit is.. (modified of course)?

24 hours:shock:I think a scaled down car deserves a scaled down Le Mans:) Since they are scaling down the drag strip what would the time on a proprotionally (roughly) scaled down Le Mans be???

If I could get the charging plate working I have a couple of digital lap counters:)

Impreza :smiley16:

[Shypo]

if you did have a charging plate in ur BCG trrack then a 24 race could quite be possible, extremely tireing and hard on the thumbs:shock: but it would be heaps of fun

—-
Go Fast, Be Free with Low CC

Undisputed Post Pimp

[aesch]

LOL Make sure you have a pit lane, and use it to pull in and charge the bit, change the gearing, etc. 😀

That way, you can “run out of petrol” and have a better pit strategy than the other guy (or girl as the case may be)

Aesch 😀

[Barrelll]

if only, if only, someone will do it no doubt lol 😀

[micro_Amps]

Quote:

24 hoursI think a scaled down car deserves a scaled down Le Mans:) Since they are scaling down the drag strip what would the time on a proprotionally (roughly) scaled down Le Mans be???

If lemans is 24 hrs, then 24 hrs x 60 mins = 1440 minutes in total (full scale)
If our cars are roughly 1/64 scale, then 1440/64 = 22.5 minutes. We would be able to do the race time in one charge on a 150mAH battery. But I suppose the object is the furthest distance isnt it. So the modified cars would probably run 3.5 or 3.8 motors, high gears, and would need two, maybe three charges to finish.
I get carried away with things when I get sleepy
uA

[Impreza]

We could run different classes as they do in the real race, even limit motors and bats. Or run unmodified?? In the end it is a distance thing. Have to look up roughly how long the track at le mans is?

22.5 minutes, hmm! Since the bit isn’t completely to scale, maybe we could up it to an even 24 minutes at le mans? or should we stick to 22.5?

Impreza :smiley16:

[micro_Amps]

I was only using 1/64th as a guesstimate.
Exactly what scale are BCGs anyway:question:uA

[jamiekulhanek]

I still think it should be a 24 hour long race, just with a 1/64 LM circuit.

I tried to make a charger using a voltage regulator stage (LM317) feeding into a constant current charger (LM317) but I couldnt get the thing to work. The idea was so it would charge the cell and sop and keep it topped up at the end of the charging cycle.

I dont really like adding a switch to my bit, because it is convenient how it discharges the cell to eliminate memory effect.

The world is mine

[Impreza]

I guess I will look online to see the size of the Le mans circuit. Will post once I find it.

Impreza :smiley16:

[Impreza]

Found it, I think. The track distance at Le mans in 2002 was a revised? 8.482-mile track or ~13.65 km. 1/64th scale would then make it 213m:shock:. May have to mod that distance a little,lol. Anyway here is a link to what the actual track looks like. http://www.racecar.co.uk/lemans2001/trackguide/track.htm

Impreza :smiley16:

[micro_Amps]

213 meters, thats fantastic:D you would have to find a basketball or tennis complex with several courts side by side, and do some major range extending mods to your controller:smiley2:
uA

[micro_Amps]

Quote:

I tried to make a charger using a voltage regulator stage (LM317) feeding into a constant current charger (LM317) but I couldnt get the thing to work. The idea was so it would charge the cell and sop and keep it topped up at the end of the charging cycle.

Might be easier to have a timer on the first stage of charging, and after say..2 mins timer clicks over to open circuit the pot and puts higher resistance resistor into circuit to drop charging current to a trickle current.
uA

[jamiekulhanek]

Quote:

213 meters, thats fantastic:D you would have to find a basketball or tennis complex with several courts side by side, and do some major range extending mods to your controller:smiley2:
uA

hehe or you could just get ALOT of exercise.

24 hours at about 5km/h, thats 120km, wonder if they would last the distance. Also can there be a back up motor, spare tyre set or anything?

The world is mine

[Barrelll]

yep youd diffinetly need to pit in if a bit of water creeps onto the track :clown:

27MHZ 3.5 Honda Accord (Custom Exhaust and F1 Wing)
35MHZ 1.0 Battery Modded Castrol Supra
45MHZ 2.2 Custom Painted Yellow and Black WRX
57MHZ 2.6 Booster Trueno
Mini Z Blue WRX (Lights, Gold alloys, Exhaust)
Mini Z Castrol Supra + all mods (Coming)

[micro_Amps]

You would need to pit for toilet breaks, or could you have a multi driver team and alternate the driving.
This is getting outa control 😯

[Impreza]

he he he, you gotta love when a idea takes off. I wonder if you could get in the Guinness book of records for the worlds smallest endurance race:p

Impreza :smiley16:

[ykev]

Quote:

I have a question and hope someone can help me. I bought the 120mAH from QFM. I got a very good run time of more than 20 min at the first time of double chargeing for 90 sec.

However, the running time reduce to 7 to 8 min subsequenctly after the new battery being used, let say from the second double charge.

Can any bit-char experienced car owner give me some idea? Is the battery they sell defective? I actually got 2 batteries from QFM, and both of them happened the same case.

/quote]

[dgs73]

does double charging have any long term neg. effects on either the batt. or charger?? Sounds like a good idea… Will try that after work
tonight. Better get myself a couple of cheap copies to mess with

[aesch]

I actually found a 3AA box with cover and switch @ Dick Smiths over the weekend for under 2 dollars.

Am thinking of getting it and try and find a faulty controller, remove the charging base from it and mount it on the cover of this thing.

With 3AAs, it should charge more rapidly. Only thing is that it wont have a timer, so I’ll need to work out how long I should charge it for and rig up a timer.

I’m pretty sure I’ve read about it somewhere but can’t seem to find it again though

Aesch 🙂

[DaveF]

Check with Dick Smith for a cheap timing circuit that can run on the same voltage.

I’ve seen very simple timers in old electronic magazines, so someone with some sparky nouse might be able to help you (ie, not me. i don’t know wnough about it).

---

DaveF! 👿
My track – http://community.webshots.com/album/58669595eliwuK

[Crom]

Quote:

Check with Dick Smith for a cheap timing circuit that can run on the same voltage.

I’ve seen very simple timers in old electronic magazines, so someone with some sparky nouse might be able to help you (ie, not me. i don’t know wnough about it).

At the moment, I’m trying to design a charger that has a timer. My main problem is trying to make it like the controller’s charger. So that it turns on when you plop the car on it, and then turns off after a set period of time.

Only I wanted to be able to choose the voltages it charges at and the time it charges for… :p I’m still working on it…

---

The impossible just takes a little longer

[Barrelll]

keep us updated crom 🙂

27MHZ 3.5 Honda Accord (Custom Exhaust and F1 Wing)
35MHZ 1.0 Battery Modded Castrol Supra
45MHZ 2.2 Custom Painted Yellow and Black WRX
57MHZ 2.6 Booster Trueno
Mini Z Blue WRX (Lights, Gold alloys, Exhaust)
Mini Z Castrol Supra + all mods (Coming)

[Impreza]

For a crude solution maybe you could mod a kit racer charger, but you would have to pick the car up off the track? If you do this watch out for that **** copper timing spring, it tends to pop out when you open the charger up:angry: It maybe a starting point??

Impreza :smiley16:

[PandaBear]

Nah, stay clear from the KIT handset, its useless.

You can get simple circuits in a kit from DSE etc, just simple 555-based timers that will on/off a relay at the end of your set period.

Simpler circuits would be like the one in the BCG TX, its a “bucket with hole in it” idea. Basic and not very accurate, but close enough.

[Impreza]

Sorry Crom, looks like I came full circle on that one:clown:. The Kit racer charging app. isn’t compatible with the bits but if you needed the timing function of the kit racer charger you could try swapping the whole plastic (mounting) piece with the bit plastic (mounting) piece?

Impreza :smiley16:

[Crom]

Quote:

Sorry Crom, looks like I came full circle on that one. The Kit racer charging app. isn’t compatible with the bits but if you needed the timing function of the kit racer charger you could try swapping the whole plastic (mounting) piece with the bit plastic (mounting) piece?

Quote:

Nah, stay clear from the KIT handset, its useless.

Heh, no worries Impreza… I went on the same wild goose chase as well.. I don’t really want to chop up my controller for a mounting piece, so I looked at the KIT charger…The contacts are spaced the correct distance apart… but there’s that stupid piece of plastic in the way… I could sand it down, but I think its easier if I just use two screws or nails for contacts and go that way.

Quote:

You can get simple circuits in a kit from DSE etc, just simple 555-based timers that will on/off a relay at the end of your set period.

Yup, that was what I was thinking of, with maybe a potentiometer or a switchable bank of resistors, to control the timing, and another switchable bank of resistors to vary the charging voltage.

[edit]
I forgot to mention… I’m thinking of using a 9V DC Power adaptor or even a variable DC power pack from DSE. So that I can run it from the mains, and have like a backup 9V alky in the box with all the electronics…
[/edit]

Quote:

Simpler circuits would be like the one in the BCG TX, its a “bucket with hole in it” idea. Basic and not very accurate, but close enough.

Bucket with a hole? I don’t even understand how it works… :dead: And thats with the schematic of QFM :p

Thanks for the input guys!

---

The impossible just takes a little longer

Edited by – Crom on 23 January 2003 15:09:04

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