E-Flight Power Sources Ask questions or read about power sources as they specifically relate to e-flight including Lithium-ion, Li-Poly, Nimh and Nicad battery packs.

Charger Question

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Old 03-04-2005, 02:26 AM
  #1
bemyself
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Default Charger Question

Hi all,
I just bought a Tahmazo digital charger and discharger and has absolutely no idea on the setting for the charging and discharging for my battery pack. My question is that if the charger states that it had features like :
1. Fully adjustable charge current is 0.1A - 3A ( 100 mA step )
2. Fully adjustable discharge is 10mA - 500 mA (10 mA step )
How am I going to set my Fast charge rate AND Trickle charge rate if I have the following batteries pack:
1. pack of 4 NiCd at 1.2v each x 4 = 4.8 V at 700mAh each
2. pack of 4 NiMh at 1.2v each x 4 =4.8V at 2300mAh each
3. pack of 2 Lipoly at 3.6v each x2 = 7.2v at 830mAh each
And please let me know the discharge for the above also. And finally, what's a Cycle Mode?
Your help into this matter is greatly appreciated.
Thanks
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Old 03-29-2005, 10:08 AM
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Default RE: Charger Question

Yeah, The instruction booklet isn't much help.
First select Battery type with the left button.
Then select charge rate required with the next button.
You can use up to 1C so for a 700mAh battery pack charge at up to 0.7A and for a 2300mAh battery pack charge at up to 2.3A.
To commence charging hold the right hand button down for 3 seconds. Charging commences after a short test.
I discharge the cells by using them in the aircraft so I've never used the discharge function and I still haven't figured out what cycle mode is.
To trickle charge just set a low charge rate - when the battery pack is charged the charger ceases charging and you get an END CHG indication.
Hope some of this is of value.
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Old 04-04-2005, 08:07 AM
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Default RE: Charger Question

From what I know about the Tahmazo charger T10 which I am using is that.... Cycle charging is only for the NiCad and NiMh. For both these type of batteries, you can set the Cycle to move from D->C (i.e Discharge to Charge). You can also set the number of times you want to cycle the pack. So if you set it at 2 or 3 then it will cycle through the Discharging to Charging Process 2 to 3 times respective.

E.g. D->C 2 means you will DISCHARGE... CHARGE... DISCHARGE... CHARGE and then it will End.

I have not been able to set it to trickle / peak charge automatically though. I can only guess it (top-up) will have to be done manually.

ps. You can also discharge a lipo or charge a lipo with the charger but it will not cycle. So if you want to cycle a lipo... it'll have to be done manually. I.e. set to discharge then when it ends... set to charge & vice versa.
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Old 04-25-2005, 11:21 AM
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Default RE: Charger Question

I apologise for not able to thank Adriantan and crwtar for their valuable information. Both information are well explained. However on charging my LIPOLY which is a 2 cell 8.4volts, 1500mah, I found the following error on the screen which read" Check the batt, Low Voltage"
I tried charging again with the parameter set at 1.6A while setting the voltage at 10.8volts and again after a minute or so it starts to beep again showing the same error on the screen. I'd read thru the instruction manual and it does not states a charging voltage pack of 8.4volts. They only can charge at 3.6, 3.7,7.2,7.4,10.8 and 11.1 Volts pack.
Please can anyone ( especially adriantan and crwtar )advise what I should do or any information which might help.
thanks alot
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Old 04-26-2005, 02:42 AM
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Default RE: Charger Question

bemyself.... From your original post, you mentioned that you had a pack of 2 Lipoly at 3.6v each x2 = 7.2v at 830mAh each. That would mean each pack is a 7.2v @ 830mah. You should charge at 10/C but if you charge at 1C then you should set it at 0.8 instead of 1.6. At 1.6 that would mean you're charging your Lipo at 2C which is dangerous as it might explode or something.

As for the voltage, I do not recall seeing any LIPO packs which are 8.4volts. It should be 7.2 as you have mentioned. Each LIPO cell is normally 3.7 or 3.6volts depending which is why you get them in multiples of 2 or 3 depending on the number of cells you put together.

E.g.
3.6v cell x 1 = 3.6v
3.6v cell x 2 = 7.2v
3.6v cell x 3 = 10.8v

3.7v cell x 1 = 3.7v
3.7v cell x 2 = 7.4v
3.7v cell x 3 = 11.1v

That is why you see charge voltages on the charger set at 3.6, 3.7, 7.2, 7.4, 10.8, 11.1
Notice there isn't a 8.4v setting. For a 2 cell 8.4, it would mean that each cell is 4.2v
4.2vs per cell is actually the voltage reading upon FULLY CHARGE. Yes it's funny why a 3.6 or 3.7v pack will actually read 4.2 upon being fully charged. It's just how things are My 11.1v packs actually charge up to 12.6vs (4.2 x 3)

MY CONCLUSION & SUGGESTION is thus.

1) You have a LIPO Pack which is 7.2v @ 830mah (mah does not multiply by 2 unless in parallel)
2) Charge at 0.8a as max. should take 1 hr or so.
3) Better still... charge at 0.1 which would take 10 hrs or so. (but most ppl can't wait anyway haha)
4) Your CHARGED UP voltage on the pack should read 8.4v (YES, the voltage is actually at 8.4V instead of 7.2V after charging).

If you charge at 10.8, it will definately not work because your pack is not of that voltage. Forcing it to do so will most probably result in an explosion Don't you feel lucky that the charger actually stopped you from blowing thailand away ?
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Old 04-26-2005, 04:17 AM
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Default RE: Charger Question

Dear Adriantan,
The pack actually reads 8.4volts and my eyes are not playing trick. I now start to wonder why is there a 8.4 volts 1500mah available on the market. I actually bought this pack at S'pore hobby.
Can you advise how I'm going to charge this batt?
The original 2 packs of 7.2V of 830mah were ordered from my local supplier but was told that the stock will not arrive in 3 months. So bought from S'pore instead. sorry for confusing you.
Regards,
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Old 04-26-2005, 09:15 PM
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Default RE: Charger Question

bemyself, make sure the pack is LIPO and not NiMH or NiCD. If it is LIPO then perhaps the "printing" or "labelling" could be wrong. If you are sure it is right then you should write to Singapore Hobby to check with them. Either that or just give them a call to clarify. They should be able to help you.

If you are unable to locate them then I would suggest you try charging at 7.4v. You will find at the end of the charge that the battery will read 8.4v

Good Luck.
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Old 04-27-2005, 12:18 AM
  #8
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Default RE: Charger Question

Dear Adriantan,
Just as what you thought! I believe it should be a printing error. Yesterday night, I tried charging at 7.4V with 1200mah and it seems to work. However after charging, the battery status shows a charge of 7.96Volts.
Moreover, while charging, the screen on the T10 shows the charging rate of the amp reducing instead of increasing. Is it normal? Other than this, i believe everything seems fine.
Thanks once again
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Old 04-27-2005, 02:11 AM
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Default RE: Charger Question

Hi Guys,

Thankfully came across this, is it so that the tahmazo can also charge the 12v lead acid batt? if so what would the operation be like i.e selection.

Thinking of buying a tahmazo


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Old 04-27-2005, 05:47 AM
  #10
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Default RE: Charger Question

I think that the Tahmazo can charge lead batteries but not sure on the 12Volts acid. Maybe Adriantan can give you a better answer
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Old 04-27-2005, 07:42 AM
  #11
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Default RE: Charger Question

Yes the Tahmazo should be able to charge Lead Batteries. Under Pb Charge Mode, you can charge batteries from 2 to 12 volts at 100 to 3000ma (100ma steps) or discharge from 10-500ma (10ma steps). Well that's for the T10 model that I have. Perhaps the higher range models like the T26 can do even more? Not sure. You should check their specs.

As for the charge rates (and also discharge rates) for all modes... yes it will initially increase to the set level (very quickly) and then decrease(usually slowly) as the battery nears the max capacity. I assume this is so that the battery is fully packed as the charging process goes along. As for end charge rate being below 8.4v it's ok... it's probably the condition of the battery. I have a new 15C 11.1v pack which does not maximise at 12.6 but rather only at 12.25v but the battery's performance is superb on my shogun. It was power on demand.

The Tahmazo is one of the better chargers I have at the moment. No regrets buying it. Support from them is also great. All I had to do was drop them an email and they replied prompty. It charges every type of batteries I have... which ranges from NiCd to NiMH to Lion to lipo to PB(lead) batteries.

The only thing is that it gets pretty hot when you use it to discharge at a high rate. Best to keep a fan or aircond blowing at it when you discharge a battery with it.
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Old 04-28-2005, 12:14 AM
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Default RE: Charger Question

Thanks Adriantan.
Why need to ask Tahmazo where I can get a faster answer from you
Cheers,
Bemyself
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Old 04-28-2005, 09:03 AM
  #13
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Default RE: Charger Question

bemyself, thanks for the compliments but I'm sure if you shoot me with more technical questions, I will not be able to provide you with an expert answer. Anyway just for your information I charged my 15C 11.1v pack again at a higher rate at 0.5A instead of 0.2 and I am actually getting a reading of 12.6volts now which is correct. I wonder why I had a reading of 12.25v the first time I charged it. Perhaps it's coz I conditioned the battery already ? Or perhaps it's a "bug" in the chargers which can't pack as much in the cells at the lower charge rates. In anycase I think I will stick at 0.5A charge rate which is about 2.5/C. The cells seem to charge ok at that rate though I only manage to get approx 100 cycles from my old LIPO packs. Now I just have to figure out whether its caused by (1) charge rate (2) bad quality pack (sorry don't know the brand of the cells), or (3) discharging at too high C thus resulting in overheated pack.
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Old 04-30-2005, 12:21 AM
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Default RE: Charger Question

Hi Adriantan,
Just curious on the 15c issue. My LIPO do not have any information on how many C. It just comes with the info that states that the battery is 7.4Volts 1500mah.
Moreover, when we charge, we usually set the charging rate to the rate that is closet to our battery spec. Let's say in my case where my battery is 1500mah, I'll set my charging rate at 1.5A ( because 1500mah is equal to 1.5amp)
But as for your case you charge at a rate of 0.5A which means your battery pack is only 500mah?
Forgive me if i got it all wrong but really appreciate if you can explain this charging theory to me.
Thanks,
Bemyself
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Old 05-01-2005, 10:29 PM
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Default RE: Charger Question

bemyself. Some batteries do not have the C discharge capabilities labelled on the battery. You should check with the vendor how many C (rate of discharge) that it is able to handle. The higher the better it is in being able to supply the required current to the entire setup.

As for charging, the C is the rate of charge we're talking about. To charge at 10/C for a 1500mah battery means you should charge at 0.15 or rather 0.1 or 0.2A (since there isn't a 0.15 inbetween value). Most people push the battery up to 1C which means you can charge at 1.5A. I however charge at 0.5A which means its 3/C. A general rule of thumb would be: 1C will take an hour to charge, 10/C will take 10 hours to charge and 3/C will take 3 hours to charge. These are rough estimates. Normally the LIPO pack will still have some juice left in the packs so it will not take longer than the stated times but rather shorter. Hope that makes sense
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Old 05-02-2005, 05:30 AM
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Default RE: Charger Question

Adriantan,
Thanks for the information but who determine the C? You say that if it's a 1500mah and have it charge at 0.5A, then it's 3C which aprrox will take 3 hourswhere 1C will approx 1 hour. So the number of hours to charge depends on the C rate? Is this where fast charging or trickle charging plays a part? Sorry to sound so stupid but I'm really new to electric.
In fact I had not even a chance to fly yet. ( both glow and electric) No instructors available. What a joke!!! Waiting for 6 months and still waiting[]
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Old 05-02-2005, 08:28 AM
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Default RE: Charger Question

bemyself. When in doubt...ask. Nothing wrong with that so don't worry.

Ok... the DISCHARGE C capabilities of a battery (10C, 15C, 20C etc) is determined by the manufacturer & quality of the battery.

The CHARGE C Rate (10/C, 9/C, 8/C..... up to 1C) is determined by the owner of the battery (i.e. you). If you want to charge it quick then u go 1C. If you want your battery to last longer or slow charge it then you do 10/C

The CHARGE & DISCHARGE Cs are not related in anyway.
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Old 05-03-2005, 12:17 AM
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Default RE: Charger Question

Hi Adriantan,
Thanks alot. That's precisely what i need to know. After talking to you, it seems that I'd much improved on the batteries issues. It seems that there are only 2 of us in this thread.
Thanks anyway.
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Old 05-03-2005, 09:09 PM
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Default RE: Charger Question

There are only 2 of us because you ask all the questions while I try to answer them all.
So there's practically nothing else for others to do but to read and verify what I have said.
I haven't been flamed yet for providing the wrong info so I guess I'm on the right track too.
Like I said.. I ain't no electrical engineer [8D]... just someone who wants to fly his chopper.

bemyself... what do you use the batteries for? car, heli, plane?
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Old 05-05-2005, 01:13 AM
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Default RE: Charger Question

Adriantan,
Maybe you are right. I ask and you answer
The battery are meant for my plane( E-starter GWS). Actually I started on glow but since I can't find any instructor, I switch to electric thinking it might be easier learning by myself but that does not seems to be the case. Can't take off on the first flight and crash on the second flight. The crash is not that serious so for the time being, put the electric on hold.[]
Adriantan, one more thing i'm not sure regarding the charging of NIMH. If the batteries is 4.8Volts ( 4 batteries) of 2300mah, How am I going to charge on the T10? Can I use the same theory as the LIPO that you advised? that is charge at a rate of maybe 0.4A which will take about 6 hours. Please advise
Thanks,
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Old 05-06-2005, 10:25 PM
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Default RE: Charger Question

bemyself,

To charge NiCD and NiMH on the T-10, you just have to set the charge rate and the charger will do the rest. You do not have to tell it how many mAh the battery is nor do you have to tell it how many volts your pack is. People normally slow charge their NiCD or NiMH batteries for 16 hours (e.g the charge adapters that comes with radios & etc have that kind of rate). I suppose that promotes longer life in the cells. So yes like LIPOS or any other batteries, it's best to charge at a slow rate. However if you are pressed for time, you can do a faster charge and I believe 0.4A (i.e. 6 hrs) won't damage the cells that much either.

I'm not sure but I think you shouldn't charge more then 1C for NiCD or NiMH cells as they tend to heat up during charging at such rates. Perhaps somebody could confirm this for us.

p.s. good luck with learning how to fly. GWS makes nice cheap planes. If you crash one, it's easy to just pick up another one so I think it's good for the learning curve. Don't stop there. Keep on at it and you'll get it soon. Of course it's best to have an instructor there next to you to help keep you out of trouble. If you don't then... perhaps you need a simulator. Good Luck ! Let us know when you've done your first successful solo flight.

p.p.s if you can see my icon/avatar... that's me with my GWS Mustang. Nice looking electric plane.. a bit twitchy though.. but that's how I like it. You can practically toss that thing around the sky. What I need is a brushless in there. It lacks a bit of power.
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Old 05-07-2005, 12:09 AM
  #22
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Default RE: Charger Question

Adriantan,
Thanks for the encouragement. I'd packed up my E- starter for the time being and concentrated on the glow trainer. For your information, I'd found a few good samaritans that are willing to teach me how to fly on the trainer and in fact, on my first flight, I'd managed to do some basic manouvers on my own( thanks to my realflight G2).
Anyway, thanks for all your information you had provided and will keep you update if there's any progress.
Regards,
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Old 05-08-2005, 09:35 AM
  #23
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Default RE: Charger Question

Hi Guys,

Seems that only a few of you guys can help as you are using the tahmazo..

Found and unused adapter in my house, it states

input 220-230v ~ 50/60hz 23w
o/p : DC12 = 1.1A

Can i mod this to power the tahmazo?

All the best,
Nick

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Old 05-08-2005, 10:26 AM
  #24
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Default RE: Charger Question

Hi nickf,
I'm not so sure on the adaptor, but I use the computer power supply to power up my Tahmazo. I believe you can get an electrician to help you. You may also get a 12Volts dry cell to power up this charger. S'pore Hobby carry this cell. You can check it out. (or Adriantan can help you out)
By the way, where do you fly in S'pore? I go to S'pore occassionally so maybe I can get you to teach me how to fly
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Old 05-09-2005, 10:06 PM
  #25
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Default RE: Charger Question

nickf, you can use the power supply if the voltage is regulated. For the tahmazo I believe you need a regulated power supply source and not one of those chargers for charging lead cells (i.e. car or motorbike batteries). I have been told by hobbists to use a power supply from a PC to power such chargers. They are pretty cheap to construct and they are REGULATED power supply units. I'm not too sure if your power supply will work but no harm trying to modify it if it is just lying around doing nothing. I did try a few and they didn't work with the tahmazo t-10. I wrote to support and they themselves advised me to use a PC's power supply. So bemyself is correct.... the PC power supply is the way to go.
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