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Old 12-03-2001, 05:24 AM   #1
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Default Charger power supply question

Though I'd ask you electric racers, since this is your speciality.

I need a AC power supply for an Apex Sigma Plus charger.

It's required input is 11v-15v DC but does not say what input Amps is required.

Will a AC Adaptor which gives out [b]12v DC @ 1.5amps/b] be good enough????

Note : that I will never be charging anything past 1AMP anyway.

Thanks.
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Old 12-03-2001, 06:38 AM   #2
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Default Re: Charger power supply question

If you don't need anything over 1 amp, 1,5 amps will do (I'm chargin 6,5 amps with a 7 amps supply on my Apex Sigma Plus). If you are charging 8 cells (TX batt), then you'll need 15 volt.

Ensure that the AC Adapter is regulated; Normally those adapters deliver much more than 12 volt, when un-loaded. That can easily damage your Apex.
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Old 12-03-2001, 11:02 AM   #3
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Default Depends

It all depends on what you want to charge at. Let's look at some examples. If you're charging 6 cells, it can reach up to 9.5 volts at times when it peaks. If you're charging at 5 amps, multiply the two, 9.5V x 5A = 47.5 watts. But you have to include what the charger consumes, approximately 5% of 47.5 watts. So, the charger can consume 47.5 w + 2.375 w = 49.875 watts. Now for all practical purposes, we'll assume the powersupply provides 12V when loaded. So, divide 49.875 watts by 12V gives 4.15625 amps. So, you would need a power supply that can provide 4.15625 amps. If you have a power supply that provides less current that this, you can reverse the process to determine how high you can charge the pack with it. If it provides 2amps max, multiply 12V by 2amps, which is 24watts. Divide 24w by 1.05, which is 22.86W. (1.05 accounts for 5% loss at the charger). So, divide 22.86w by 9.5V. which gives you 2.5amps. So you can charge a pack at 2.5 amps safely. Manufacturers rate their power supplies very conservatively, so you'll be safe at this level. Hope this helps.
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Old 12-04-2001, 08:53 AM   #4
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Nice math..too bad it doesn't seem to work out right, but that's another story.... Most charger manufacturers will tell you that you should use a 12v. P/S rated at 1 amp higher than the highest charge voltage allowed by the charger.... But I say at allow at least 2 amps higher, you P/S will run cooler. And make sure your reading the continuous amps, not peak amps. My Novak Rhino can charge at up to 10 amps, so I bought a 12 amp/14 amp max P/S.


10 amp
+
2 amp
=
12 amp

See simple math and it works no matter how many times you retry it...LOL

But I also say but the best P/S you can afford... Check out

bill's 2way radio
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Old 12-04-2001, 09:16 AM   #5
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Default Actually

Actually, it does work out this way. However, the temperature of the power supply nor the charger has been taken into account since we can't really know for sure. My calculations were based on real life experiment. Every power supply operates at different temperature. Just because one might be hotter than others does not indicate that one is being strained. Chargers themselves do not consume much power at all. When it comes to power supplies, you can't just look at the current rating, you have to look at the power rating. The batteries themselves are not being charged at 12VDC, so power is where you have to pay attention to most of the time. And your comment about peak versus continuous current supports my theory all the more. All in all at the end, it works.

Last edited by Yuchol; 12-04-2001 at 09:19 AM.
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Old 12-04-2001, 09:37 AM   #6
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NovaRossi- Providing the supply is regulated I think the answer is YES!!!!!
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Old 12-04-2001, 11:55 AM   #7
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Pretty theoretical.... It's much more simple and effective to read the manual !!!

www.apexhk.com

Nicad voltage range:

4,8-10,8 volt for input voltage over DC 13,5 volt.
4,8-9,6 volt for input voltage under DC 13,5 volt.

These voltages are nominated, NOT peak voltage. So 9,6 volt corresponds to 8 cells.

And hereby, I correct myself, when I claimed that charging 8 TX cells requires 15 volt.
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Old 12-04-2001, 09:18 PM   #8
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Yucho-- Chargers aren't amp boosters, so you cannot charge at 5 amps with a 4 amp power supply, you can set it at 5 amps, but the most you will get will be like 3.75 amps (assuming the charger uses .25 amps for it's self). Also if you would use a 4 amp P/S most likely you WILL be asking more of it than the manufacturer recommends and there is a reason why equiptment has a rating, even though it is concervative (sp?). I believe that they know just a little bit more about what they build than we do.

Also remember chargers are built to run on 12v, so just because the pack peaks at 9.5 volts means nothing. Maybe at 12v your math works, but at 9.5v it does not.
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Old 12-05-2001, 05:38 AM   #9
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Default

Wow - Im now officially more confused

The reason is I purchased the Apex Charger from the US. It comes with a 110v Power Supply (as well as 12v) . We use 220v here in Australia.

Coverters here (110v--->240v) cost about 3 times more then a simple power adaptor)
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Old 12-05-2001, 10:21 AM   #10
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Default That's not always true

That's not always true. Charger has many characteristics of a power supply. If your theory is correct, all the transformers in this world would not function. If your theory is correct, so many countries wouldn't be using 240V service. The higher the voltage, the less current you need. What you're saying basically is that if the input of the transformer is rated at 12V, 2 amps, you cannot get more than 2 amps out of the transformer if you're operating at 9.5V. Doesn't this contradict the theory of transformer?
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Old 12-06-2001, 03:36 AM   #11
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Default depends on power

Just my $0.02, we should look at the power P=V*I. It rather depends on the power output of the DC supply (not input). However, some low end charger cannot provide charge voltage higher than the DC supply voltage (eg. Apex Sigma +).
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Old 12-06-2001, 10:49 PM   #12
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Default Re: Charger power supply question

Quote:
Originally posted by Novarossi
.................Note : that I will never be charging anything past 1AMP anyway.

Thanks.
Aren't you using stick packs for a starterbox? Hope you aren't going to charge those at less than 1amp. It'll take forever. Doesn't someone like Integy or Sigma sell a fairly cheap and small power supply called Nuclear 7 or something like that that pumps out 7 amps?

How much is a converter down under?
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Old 12-07-2001, 01:27 AM   #13
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Default Re: Re: Charger power supply question

Quote:
Originally posted by Sydewynder


Aren't you using stick packs for a starterbox? Hope you aren't going to charge those at less than 1amp. It'll take forever. Doesn't someone like Integy or Sigma sell a fairly cheap and small power supply called Nuclear 7 or something like that that pumps out 7 amps?

How much is a converter down under?
Converter here is over $100AUS
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Old 12-07-2001, 02:28 AM   #14
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Default Re: Re: Charger power supply question

Quote:
Originally posted by Sydewynder
Doesn't someone like Integy or Sigma sell a fairly cheap and small power supply called Nuclear 7 or something like that that pumps out 7 amps?
I live in Denmark, and around here the Sigma Plus comes with the Nuclear for 220 volt mains.

If that is interesting, try contact APex at www.apexhk.com.
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Old 12-07-2001, 08:31 AM   #15
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Default Side Note: DIY DC Power Supply

Slight OT: if you'd like to build a power supply, here's a page I found. Gonna build one of these babies soon. Hopefully.

http://www.rason.org/Projects/powsupply/powsupply.htm

If 10A ain't enough for ya, get a few more 2N3055 power transistors and wire 'em up in parallel to Q2 and Q3. Do not forget the .1 ohm resistors..... "Emitter Ballast Resistors"...
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