Please Help!
 

I have asked on other forums and no one is helping. Lets see how good this forum is! :sneaky:

So I am converting a PC power supply for my new iCharger 106B+.

I am using a 10w 10ohm resistor on the 5v rail currently and the voltage on the 12v is around 11.96v. The charger turns on but cuts out when I press 'START' charging.

Will a resistor with more resistance 4.7ohm 10watt bring the voltage up and regulate it better?

Any help would be great! Thanks

Anyone?

For starters 4.7ohm is LESS resistance than the 10ohm you have already. Also you have it across the 5v rail and so it won't make a difference if you change it. All that resistor is doing is applying a constant load to the PSU to keep it on. Some ATX PSU's will trip out if there is no load. It isn't regulating anything!

I don't bother with the resistor in mine. What I do is simply leave the charger connected and switch the psu on and off by the mains. The current the charger pulls at rest is enough to keep the psu alive.

Personally I think there is something else wrong within your setup? Changing that resistor certainly won't help. You could try removing it altogether as I have done?

I thought less ohms was more resistance? And everyone on vids about converting these PSu's says the resistors help regulate the power or something.

Anyway, the PSU voltage increase by about 0.2v when I connect the resistor. I need to somehow get the voltage above 12v I think but I'm not sure how without getting a resistor with more resistance?

No. More Ohms = more resistance. (Ohm is the measurement of resistance, so higher = more).

Ideally the voltage should actually stay constant, only the current should change, depending on the load (which resistors also are) you put on the unit, if I remember correctly.

I was told this on a URC thread. :/ :confused:

First of all
a 10 ohm /10w resistor is larger (more resistance) than a 4.7ohm/ 10watt resistor
Ideally the voltage is regulated by voltage regulators as well as resistors internally
for the power supply. There are other ways to regulate it, but too compicated for
me to get into here, but it is possible
Sounds as if there is something wrong internally in the regulator stage if the unit is turning off when you hit the charge button.
Depending on your skill level, I would check the output of the regulators, but from
what I've read so far, I would highly suggest to either get rid of that supply and get
a new one, or get it to someone who has a higher troubleshooting skill set than you
to play it safe.
Mike

I will admit I shorted out the two wires on the PSU switch. It made a pop sound and a flash. I had soldered 4mm bullets onto my multimeter wires because standard ends broke off. One of the bullets went black so I assumed the noise and flash was just the bullet.

There is no way in hell I'm getting a new charger as the charger I am using is an $90 one that I only received brand new today. (iCharger 106B+)

I have tried another PSU (less powerful) and it is currently running the charger and charging a 5Ah 4S at 1C without breaking a sweat.

I will try some higher ohm resistors later on the first PSU I converted as it is more powerful and has and on/off switch.

When the charger is in use the PSU 12v rail voltage drops to around 10.5v is this something a resistor on the 5V rail would fix? Or is it normal for the voltage to drop?

Thanks

I understand your pain! Money is tight!
Depending on the size and type of load you put on the power supply and how well
the supply is regulated. It is possible to get a voltage drop from it.
Im not really familiar with the type of supply your trying to use, but generally if you add
any type of resistance to the output. it will drop the voltage, which you really do not want to do if its running at 12vdc. if you have between 11-14vdc output you should be fine.
If you had a pop or ay type of flash from that supply check its fuse packs. There should be external fuses that are someplace on the panel, also with the unit unplugged, open up the supply and check to see if there are any internal fuses that may have blown. If you do not find any. there is a very distinct possibility that you blew the regulators and thats why your not getting the proper output. in which case the only way you can get the right output is by A. Replacing the supply or B. Replacing the regulators or diodes which my be blown internally. Option B is going to need some electrical troubleshooting skill, which you may or maynot possess.

When the resistance is put on the 5v rail it boosts the 12v output (by 0.2v with the 10w 10ohm)

To increase resistance should I just run 2 10w 10ohm resistors in line with each other, or run a single resistor and increase the watts or ohms?

PC supplies vary greatly, it's difficult to make broad generizations. But yes, frequently more load, including on the 5V rail, can help hold voltage up. Does require some experimentation as mentioned.

More load = less resistance, which can cause some confusion. Try a pair of resistors in parallel, not in line in series, to get lower resistance.

The charger is fine, it's the power supply. Some PC supplies don't work for charging very well, again they vary a lot. If you can try a server supply, they are much better suited to charging duty. Or sn actual bench supply, even better as they are usually at higher voltage of around 13.8V.

What would resistors in parallel look like? Do you mean just a resistor between a 5v and ground wire and then the other resistor between a different 5v wire and ground wire?

I'll experiment a lot.

What I don't get is more ohms = more resistance but less ohms = more heat?

And what this guy says basically means less ohms = more resistance right?

Correct on parallel, each resistor from the 5V to ground.

Yep, try both ways (parallel, and both in line for series) and test. See if there is a clear trend.

In general, less ohms = less resistance = more load = more current = more power dissipated = more heat.

Other way, that guy is raising the resistance, from 2 ohms to 10. Reducing the heat. Apparently with his supply that worked, voltage was enough.

Please let us know how it turns out, and what supply it is.

What I am seeing here is some confusion between terms. I have been an electrician for over 30 years, and a certified electronics tech half of those 30 years.

The terms resistance and ohms are one and the same. The terms ohms/resistance and load are different, in respect to how they work.

So here goes my quick, very basic electronics class on resistance.

Less ohms = more load
Less resistance = more load
More ohms = less load
More resistance = less load
More load = more heat

So let's add some numbers into this,

10 ohm resistor with 10 volts dc = 1 amp load at 10 watts
5 ohm resistor with 10 volts dc = 2 amp load at 20 watts

The basic ohms law formulas are power (watts) = volts times amps, amps = volts divided by resistance ( ohms) the higher the watts the more heat you will create.

Now for parallel versus series circuits.

1-{}-2 3-{}-4

If we can visualize the above as two resistors,the first having wire numbers 1&2 the second being 3&4. To connect these in series, wire numbers 2&3 would be connected together. To connect in parallel wire numbers 1&3 and 2&4 would be connected respectfully. Now let's assume each resistor is 10 ohms, in series your total resistance would be 20 ohms. In parallel your total resistance would be 5 ohms. Basically, put another way, resistance in series is all of the resistors added together, in parallel, if the resistors are equal values, it's the value of one resistor divided by 2. If you have more than two resistors, the math gets more complicated.


So what does all this mean to your power supply? In my exp. doing these conversions, as it's been said, power supplies vary greatly. If you heard a pop AND saw a flash, something internal went. With the power disconnected, open the case you may get lucky and find a blown fuse, but more than likely you will see some black stuff inside. Also, as stated, I have only had good luck with server power supplies. Using the pc supplies, in my exp. adding load to the 5v supply will bring the 12v supply up to approx. 13.7v on a good power supply. This is up to the point that the 5v supply gets overloaded. This is also due to the newer style power supplies turning on by the load on the 5v supply.

On a side note, I've had much better luck, converting xbox 360 "brick style" power supplies.

If you need more help, get back to me.

Tom

Thanks!

Who wants to hear something funny? Just blew up the second PSU about an hour ago -_-

I don't understand what happened though I didn't short anything out like I did with the first one. I turned on the PSU, then I plugged in the positive out banana lead and then when I plugged in the negative output banana lead it went bang and the PSU cut off. Man I hope my charger is ok!

Now I need a new antenna and a new PSU. So mad! I was really hoping to run the new 5S this arvo as power came back on from the cyclone.

Will two 10ohm 10 watt resistor in (series and/or in parallel) increase or decrease load compared to one 10ohm 10w resistor?

With two, it should be 5ohm which is less resistance but more load but when they are together, is it 20w or 5w or still just 10w? And does more wattage add more load?

A single 10 ohm resistor on 5V results in 0.5 amp and 2.5 watt of power dissipation.

2 in parallel reduces resistance and increases load, 5 ohm, 1 amp, 5 watt.

2 in series increases resistance and reduces load, 20 ohm, 0.25 amp, 1.25 watt.

The 10 watt on the resistor is a maximum rating, the actual power dissipated depends on the voltage applied to the resistor. In both the series and parallel cases the 2 resistors have a combined 20 watt rating, but that will occur at different voltages depending on parallel/series hookup. As mentioned earlier if ran at full rating the resistor will get quite hot, best to run well below the maximum rating.

Cool! Makes sense with the calculations next to eachother like that!

So isn't it better to have two 10w10ohm resistors in parallel to have less heat than one 10w 5ohm resistor?

PC supplies are generally designed with the assumption of having load on them when turned on. Most recommend having the charger attached before turning on the PC supply.

I connected the battery banana's once I turned on the PS with the charger connected. Which it says to do in the manual so I thought I'd try it. Charger is a ok. Just did a storage discharge fine on the first 17a PC PSU. Obviously because it requires no power.

You are on the right track, that should reduce heat of each resistor.

Drat, reading is fundamental, you did mention output. My bad.

No luck, neither power supply is gonna work :(

Back to the drawing board...

Just bought this

http://www.ebay.com.au/itm/HP-DL380-...uhb=1#viTabs_0

Will be converting with this method

http://www.ultimaterc.com/forums/sho...d.php?t=174225

Thanks for all the help, will report back in a few days, hopefully it all works out and I can run my new 5S lipo.