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370mah nimh radicalrc packs - ma taken on initial charge? Peak voltage?

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370mah nimh radicalrc packs - ma taken on initial charge? Peak voltage?

Old 01-31-2008, 04:39 PM
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somegeek
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Default 370mah nimh radicalrc packs - ma taken on initial charge? Peak voltage?

Curious how many ma a radicalrc 370mah nimh pack should take on the initial charge? My 370mAh nimh pack took 100ma and sits at 5.53V. Sound about right?

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Old 01-31-2008, 07:57 PM
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Default RE: 370mah nimh radicalrc packs - ma taken on initial charge?

You need a better charger. For trickle charging you need to limit the charge current to 1/10 the rating or 37 to 40 ma in this case. THen you let it charge initially for about 1.4 times the time or 14 hours because it's a 1/10 charge rate.

I would never let a pack charge at over 1/4C like this is with 100 ma going into it unless it was on a peak detect charger. And peak charging right off the bat generally isn't recomended.

It sounds like you may be using some generic wall wart supply rather than a proper charger. Get the right tool for the job.


5.53 for the pack voltage while being charged at 100 ma sounds about right. But don't charge it for more than 4.5 to 5 hours at that rate. When you take the pack off after an hour the pack voltage will be down around 5.1 to 5.2.
Old 01-31-2008, 08:12 PM
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Default RE: 370mah nimh radicalrc packs - ma taken on initial charge?

I'm using an MKII Hobbico Quick Field Charger - nimh mode at the lowest rate which my Watt's Up meter reads as 170mA. Peak was detected after it accepted ~95mAh of charge per my Watt's Up meter.

I had asked about this previously and folks seemed to think this initial charge at this rate would be fine. I was just thinking they'd draw more juice longer. I pulled the packs within a minute of the charger beeping indicating a full charge.

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Old 01-31-2008, 08:47 PM
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Default RE: 370mah nimh radicalrc packs - ma taken on initial charge?

Most nmh cells need several slow charge /discharge cycles befor they will accept/deliver there rated capacity, after which they will fast charge ok. I have a simple charge regulator circuite at home that I'll try to find over the weekend, will post it here. It uses a IC 3 pin voltage regulator configured as a current regulator and is verry stable . i have built a chargeing station with 4 fixed current outlets and 1 switched current outlet 17Ma-50Ma in 6 steps , its been in regular use for 8yrs without problems, I also use a Supernova charger/discharger for fast and feild chargeing.
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Old 01-31-2008, 09:17 PM
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Default RE: 370mah nimh radicalrc packs - ma taken on initial charge?


ORIGINAL: SGC

Most nmh cells need several slow charge /discharge cycles befor they will accept/deliver there rated capacity, after which they will fast charge ok. I have a simple charge regulator circuite at home that I'll try to find over the weekend, will post it here. It uses a IC 3 pin voltage regulator configured as a current regulator and is verry stable . i have built a chargeing station with 4 fixed current outlets and 1 switched current outlet 17Ma-50Ma in 6 steps , its been in regular use for 8yrs without problems, I also use a Supernova charger/discharger for fast and feild chargeing.
Stewart
Sounds like a neat project.

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Old 01-31-2008, 09:28 PM
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Default RE: 370mah nimh radicalrc packs - ma taken on initial charge?

I found an old Futaba wall wart charger that states 4.8V at 50mA for the Rx output. This would do the trick decently? Roughly 1/7C
Old 01-31-2008, 10:13 PM
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Default RE: 370mah nimh radicalrc packs - ma taken on initial charge?

1/7C is much better. I own several of these exact same Radical R/C 370mah NiMH packs and they definitely need the slow formation charging before they will take a full charge. I'd give them three cycles.

Here's a charge time calculator:

http://www.csgnetwork.com/batterychgcalc.html

At 50ma you would charge these 370mah packs for 8.87 hours, or 8hrs., 52mins.

David
Old 01-31-2008, 10:17 PM
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Default RE: 370mah nimh radicalrc packs - ma taken on initial charge?

Thanks, Raindave!

On this older charger there are three wires, red, black and white... what's the white wire for?

Edit - read it's for ground.

I hooked this up and it's putting between 40 and 50 mA into my watt's up meter. Flipping back and forth between .04 and .05 on the source. Think this will do the trick. Gonna keep an eye on it. Couple of questions...

Is a full charged nimh 1.4V per cell?

5.6volts reading on the charger for this nimh pack when I pull it off the charge?

What's a good load to put on this pack to drain it slowly so I can charge it again?

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Old 02-01-2008, 03:18 AM
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Default RE: 370mah nimh radicalrc packs - ma taken on initial charge? Peak voltage?

This is where the better chargers come in handy. My two Lipo chargers I bought over the last two years both handle NiMH and NiCd's as well as the Lipo. The neat thing is that they'll also discharge down to a safe cut off voltage and stop. Makes it easy to cycle packs like this.

Run a resistor as a load but also put the voltmeter on it and when it gets down to around 4.4 volts for the pack consider it dead. Something that draws 200 or so ma. That would be 4.8/.2 = 24 ohms. You'll want to get a 2 or 4 watt resistor as well That's almost a watt of power. A one watt resistor won't burn out but it'll get stinking hot. Hence the 2 or more watt size suggestion.
Old 02-01-2008, 10:47 AM
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Default RE: 370mah nimh radicalrc packs - ma taken on initial charge? Peak voltage?

For the most part, these packs will be charged with my Hobbico MKII charger after these initial forming charges. Leaving a pack on overnight brought the charge up to 5.72 after 10 hours. Gonna charge the other pack for 10 hours now.

Gonna stop by Radio Shack today to pickup some resistors.

Those pack cyclers sound very convenient.

Thanks for all the replies on this guys.

somegeeek
Old 02-01-2008, 12:00 PM
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Default RE: 370mah nimh radicalrc packs - ma taken on initial charge? Peak voltage?

Forgot I had a bunch of resistors in my old electronics class stuff. Connected six 1/2 watt 150Ω resistors in parallel for a measured resistance of 24.9Ω. Got my load wired up.

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Old 02-01-2008, 09:47 PM
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Default RE: 370mah nimh radicalrc packs - ma taken on initial charge? Peak voltage?

So I was discharging one of my packs and was about 200mAh through the 370mAh pack and around 4.6V and my watt's up meter was blank when I looked at it five minutes later. Pulled the load off and the watt's up meter came back on to read 4.45V for the pack. On load again with an aux battery connected to the watt's up meter(dies if the source pack V is too low) and the V read 3.4. Pull the load off and the source pack sprang back up to 4.45V.

When reading if a pack is low, should this be 1.1V per cell under load or idle?

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Old 02-01-2008, 10:04 PM
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Default RE: 370mah nimh radicalrc packs - ma taken on initial charge? Peak voltage?

Under load. It'll bounce back up just like you're finding it does.

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