Interesting Use For Hobby Chargers

[blackdragonx1186]

So while sitting around on the clock at work, I decided to play with my Tri-P7 work-light I built for fun. Under no load my hobby charger has about 30v on its output, to overcome batteries voltage. Well I hooked it to my lights, and got a reading of around 4.7v. I set my charger to 9 cell NIMH pack, which is 10.8 nominal, and a charge current of 2.8A. And boom, I have a fully regulated CC power supply. Only annoyance is that the charger will cut off the current for a few seconds to test the batteries voltage with no charge current.

This is also a way I can check the Vf of an led, to an accuracy of .001 volts, at any current I want.

http://i23.photobucket.com/albums/b380/blackdragonx1186/lighting/P7081997.jpg

 

[blackdragonx1186]

Over 100 views and no comments?:sigh:

 

[jamesmtl514]

first comment.
i read the article but there's nothing that I can contribute.

 

[Tekno_Cowboy]

One thing that would be a great benefit to this thread is if other people with hobby chargers would chime in. I'd love one of these for testing Vf and focusing reflectors.

 

[core]

Over 100 views and no comments?:sigh:

Well the only comment I had, but decided against using the bandwidth to ask was:

What do you mean when you say it's outputting 30V to overcome the voltage of the battery? It shouldn't be putting out any voltage until you start the cycle and _after_ it has read the voltage from whatever you've connected. Right?

And then it should only need to output it's calculated V for whatever you have selected, to "overcome" the voltage of the batter(ies). I don't see how it can measure the connected battery if there's any voltage on the leads at idle anyway.

I may have to get mine out and see if it does anything similar.

Oh, and for the nuisance current dropout when it checks on things, does yours let you configure at what relative time this occurs? You could set it to an extremely high number of minutes and probably never run into it in normal use.

 

[blackdragonx1186]

Well the only comment I had, but decided against using the bandwidth to ask was:
What do you mean when you say it's outputting 30V to overcome the voltage of the battery? It shouldn't be putting out any voltage until you start the cycle and _after_ it has read the voltage from whatever you've connected. Right?


And then it should only need to output it's calculated V for whatever you have selected, to "overcome" the voltage of the batter(ies). I don't see how it can measure the connected battery if there's any voltage on the leads at idle anyway.

I may have to get mine out and see if it does anything similar.

Oh, and for the nuisance current dropout when it checks on things, does yours let you configure at what relative time this occurs? You could set it to an extremely high number of minutes and probably never run into it in normal use.

It has multiple functions, and one of it's is basic data information. Input voltage, output, each cell's voltage, etc. For whatever reason, it shows 30+volts, until a battery is connected. Then it shows the cells voltage.

As for the dropout current, I don't have a direct option to change it. I do have 3 charge modes. Normal, which is what I was using. Linear, which from what i gather charges at the set current until the -v delta is reached. And then automatic, which charges at a rate based on the internal resistance of the cell.

If anyone likes i can make a short vid of the things I mentioned.

 

[45/70]

I've never checked mine, but since it is capable of charging 15 NiCd, or NiMH cells in series, 30 Volts sounds about right.

I'm guilty of reading your thread and not posting. :candle: I use a bench PS for determining the Vf of LEDs, so didn't really have anything to say. I guess I could have said it's a lot easier to do that way.

One thing I will add, now that I'm here, I seriously doubt that your hobby charger has anywhere near 0.001 Volt accuracy. I don't think even a $200-$300 hobby charger is that accurate. For what you're doing, it really doesn't make that much difference though. +/- 0.01 Volt or so accuracy is plenty good enough. When I'm serious about checking voltages, I use a separate meter, rather than relying on the readout on my PS.

Dave

 

[blackdragonx1186]

I was going off what it claimed as accuracy. It was close to 200 bucks when I bought it, lol. Either way, I think its pretty accurate.

 

[core]

As for the dropout current, I don't have a direct option to change it. I do have 3 charge modes. Normal, which is what I was using. Linear, which from what i gather charges at the set current until the -v delta is reached. And then automatic, which charges at a rate based on the internal resistance of the cell.

Actually I was referring to what you said earlier, which is that it cuts off current momentarily to see where things are V-wise. On the DC/AC6 clones this is by default 5 minutes, but is adjustable.

I would hope that such things are needless when in a -dV mode. Else somebody is going to have a bad day.

 

[uk_caver]

Actually I was referring to what you said earlier, which is that it cuts off current momentarily to see where things are V-wise. On the DC/AC6 clones this is by default 5 minutes, but is adjustable.

I would hope that such things are needless when in a -dV mode. Else somebody is going to have a bad day.

What is the difference between doing -dV detection using on-charge and briefly-off-charge voltage measurements?

 

[core]

What is the difference between doing -dV detection using on-charge and briefly-off-charge voltage measurements?

Well I don't want my CC/CV charger doing that. I thought the C stood for Constant?

Don't cross the streams.

(And yes I believe I said this didn't apply to -dV yes?)

 

[uk_caver]

Do the cells care if the constant current is applied with a 100% duty cycle, or merely a 99% duty cycle?

 

[core]

Do the cells care if the constant current is applied with a 100% duty cycle, or merely a 99% duty cycle?

With CC/CV, it would skew the charge. But not because of the cells. As for what the cells like, I guess that depends if they have a nipple.

 

[core]

Ok, ok:

The measurement period I mentioned above lasts for several seconds. And if you watch the voltage, you see it must be so.

With Pb you call it surface charge. I don't know what the technical name is for it LiIo but a similar manifestation exists.

You cannot measure voltage of a LiIon cell within milliseconds after removing charge voltage.

This is why hobby chargers remove current for an annoyingly long time.

This is also why you should check the gender of your cells before using them.

 

[uk_caver]

I was wondering what you meant by the 'bad day' comment.
It seemed like you were saying there's something bad about doing -dV detection during brief interruptions of charge current.

 

[core]

I was wondering what you meant by the 'bad day' comment.
It seemed like you were saying there's something bad about doing -dV detection during brief interruptions of charge current.

Oh, I see. Naw here's my statement again, and keep in mind this was in the context of shutting off after 5 minutes:

I would hope that such things are needless when in a -dV mode. Else somebody is going to have a bad day.

Meaning if your -dV charger has to do a 5min check then you're probably about to have a bad day because you've got worse problems.

Ya?