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Old Apr 12, 2010, 11:38 AM
KC
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Originally Posted by Von Trippenhopf View Post
...The BiCha is far closer to ideal, just ridiculously expensive.

Cheers anyway.

What price range are you looking for?

KC
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Old Apr 12, 2010, 04:22 PM
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Originally Posted by bz1mcr View Post
You can't charg 30-100 mAh batteries at 400 mAh. That's the problem. We need a charger that will not over current small batteries. we need an adjustable output of about 30-200 mAh.
Ye,the esky has an output of .8 , could you not just open the charger and solder in a resister in there or something ? i have been useing these chargers for 4 years and they work great,i have three of them now.
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Old Apr 12, 2010, 04:53 PM
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Originally Posted by KC View Post
What price range are you looking for?

KC
Good question, I guess it depends on what is available.

I already have a selection of chargers, including some intelligent ones.

None go below 100Ma though.

I'd like to charge 60-70mAh cells at 1c or below, preferably.

How much is it worth spendng to extend the life of a $2 lipo ?
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Old Apr 12, 2010, 06:38 PM
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Ok, one other option. And as you already realize, there aren't that many out there.

Mod a Parkzone stock charger. The resistor value can be change to your desired output. PZ chargers could be had for less than $15 from the Indoor and Micro Model F/S forum.

e.g.

Make (or buy) a parallel harness for parallel charging multiple small lipos. Connectors. Far left, $1.40 for 10 pcs. (+sh).

I'll show you my set up if your are interested.

KC
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Old Apr 12, 2010, 10:32 PM
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Originally Posted by KC View Post
Ok, one other option. And as you already realize, there aren't that many out there.

Mod a Parkzone stock charger. The resistor value can be change to your desired output. PZ chargers could be had for less than $15 from the Indoor and Micro Model F/S forum.

e.g.

Make (or buy) a parallel harness for parallel charging multiple small lipos. Connectors. Far left, $1.40 for 10 pcs. (+sh).

I'll show you my set up if your are interested.

KC
Hi KC,

I think that may be the best way to go, I've got 3 or 4 of those chargers lying around, I'll substitute a larger resistor and aim for lower current.

With luck I'll be able to add a charge lead and throw the plastic box away, then power it from my power supply.

I've already got serial and parallel charge leads I made for eflite style lipos, is this what you are talking about ?

Here's one of my serial charge leads:
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Old Apr 13, 2010, 05:29 AM
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I've already got serial and parallel charge leads I made for eflite style lipos, is this what you are talking about ?
Yes. Your serial charging harness looks very nice, but with the single cell chargers that we are talking about can not charge serially. But because of the current adjustable pot on the charger, parallel charging is ideal.

There are a lot of info spread out in the forums about how these single cell chargers are modded, so most, if not all of what I did to mine isn't original at all. It's just a collection of different ideas.

KC
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Old Apr 13, 2010, 05:42 AM
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Originally Posted by KC View Post
Yes. Your serial charging harness looks very nice, but with the single cell chargers that we are talking about can not charge serially. But because of the current adjustable pot on the charger, parallel charging is ideal.

There are a lot of info spread out in the forums about how these single cell chargers are modded, so most, if not all of what I did to mine isn't original at all. It's just a collection of different ideas.

KC
I'm not quite sure what's going on with that charger ?

"RS switched power jack on front of the charger is used to set the charging current with the serial harness, then removed. The switched power jack allows normal charging without the serial harness."

Are you saying that you turn the current down when charging 1 cell - then turn it up for 2P (parallel) charging ?

If it's a serial charging harness where are you getting 8+ volts from ?
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Old Apr 13, 2010, 06:30 AM
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If it's a serial charging harness where are you getting 8+ volts from ?
The serial harness is for the DMM to read the charging current going into the parallel charging harness. Current can only be measured in series with the circuit.

I'm not sure about the 8+ volts you are refering to? The AC adapter (external power source) is 6 volt input.

Quote:
Are you saying that you turn the current down when charging 1 cell - then turn it up for 2P (parallel) charging ?
Yes. In stock form, the charge rate can be adjusted with the pot from about 180mA to about 350mA.

So for example, if I wanted to charge three 70mAh lipos, I would turn the pot till I see 210mA on the DMM to charge the 3 70mAh lipos in parallel at 1C.

If one 70mah lipo is needed to be charged at 1C, then the resistor mod I mentioned previously would be needed to bring down the lowest charge rate to 70mA.


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Old Apr 13, 2010, 05:59 PM
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This might be exactly what your looking for? Falcon Li Poly Charger from here http://www.falconmodels.uk.com/acata...Equipment.html about half-way down the page (13 GB Pounds)

I'm looking for something similar but for 2 LiFePO4 batteries in parallel. It doesn't need to be a high current output charger as it will remain connected to the batteries for a large portion of the time & the current draw of the device using them is small.

It may be possible to modify this charger - I have asked the suppliers.

Another requirement I have is just to take down the voltage of a full battery charge from 3.7V to 3.3V before usage in the audio circuit (more reliable operating voltage). I'm told once connected to a load, the batteries drop to this voltage level fairly quickly - I would like to automate this.

Anybody got suggestions for this & a cheap 3.2V charger (either stock or I'll modify one)? I can also DIY if there's a schematic to follw.
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Old Apr 13, 2010, 06:08 PM
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Another requirement I have is just to take down the voltage of a full battery charge from 3.7V to 3.3V before usage in the audio circuit (more reliable operating voltage). I'm told once connected to a load, the batteries drop to this voltage level fairly quickly - I would like to automate this.

Anybody got suggestions for this & a cheap 3.2V charger (either stock or I'll modify one)? I can also DIY if there's a schematic to follw.
A charged lipo is about 4.2v and yes, the voltage can drop quickly - usually when discharged at 20C !!

Buy a Turnigy Accucell 6 ($24) they happily charge Li-Fe cells.

I have to ask why you are using 2 LiFePO4 batteries in parallel ?

If they are going to be subject to constant trickle charging and very little draw, you'd be better off using 5 x nimh or nicad cells.

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Old Apr 13, 2010, 06:23 PM
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A charged lipo is about 4.2v and yes, the voltage can drop quickly - usually when discharged at 20C !!
Thanks for the reply - I'm using liFePO4 NOT lipo so 3.7V max not 4.2V. Any idea how quickly this comes down to 3.3/3.2V? What load/time needed?

Quote:
Buy a Turnigy Accucell 6 ($24) they happily charge Li-Fe cells.
I saw these but I'm not sure they can remain permanently connected to the battery? I would prefer a board that can be mounted inside an existing box so no user intervention or display needed.

Quote:
I have to ask why you are using 2 LiFePO4 batteries in parallel ?
The batteries are being used individually but being charged in parallel.

Quote:
If they are going to be subject to constant trickle charging and very little draw, you'd be better off using 5 x nimh or nicad cells.

Need/want to use the LiFePO4 for their specific characteristics
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Old Apr 13, 2010, 06:33 PM
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KC,

You say that the LED works normally when using a 6V external supply. I'm amazed at this as there is a tap off the battery pack specifically for the LED. The positive lead of the LED is only connected to the battery tapping point and would be open circuit with no batteries; therefore not working.

Did you rewire anything to get the LED working?
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Old Apr 13, 2010, 07:25 PM
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Did you rewire anything to get the LED working?
Nothing fancy. I have 4 NiMh's in the charger with the 6V adapter's + and - soldered directly onto the charger's + and - terminals. The rechargeables allow the LED to work normally and also act as a buffer for the unregulated AC adapter.

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Old Apr 13, 2010, 07:46 PM
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Originally Posted by jkeny View Post
Thanks for the reply - I'm using liFePO4 NOT lipo so 3.7V max not 4.2V. Any idea how quickly this comes down to 3.3/3.2V? What load/time needed?

I saw these but I'm not sure they can remain permanently connected to the battery? I would prefer a board that can be mounted inside an existing box so no user intervention or display needed.

The batteries are being used individually but being charged in parallel.

Need/want to use the LiFePO4 for their specific characteristics
Can't help you with the voltage drop on liFePO4 however if they are being trickle charged and subject to a drain at the same time they might never reach max volts.

I don't know enough about liFePO4 to comment on whether it's possible or advisable to connect them permanently to a charger.

It almost sounds like you'd be better off leaving the cells out of the design.

Which specific characteristics are you refering to ?
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Old Apr 13, 2010, 11:18 PM
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thx for your great advice, i learn much, you did a great thing here!
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