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Old Mar 19, 2011, 10:17 PM
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Hyperion 720i net charger questions

I have a Hyperion 720i net charger and have a couple of questions I am sure someone will be able to help me with. The charger has three options when charging nimh and nicad batteries. They are linear, automatic and normal. What is this and witch is the best to use?

Another question. I have 1200mah nimh 6v 5 cell reciever packs. I charge them and discharge them at 1.2A in the normal setting. I set the discharge cut off at .9v per cell. I am only getting about 700mah of charge in them and700mah out disharging them. The question is am I doing this right, is one of the other modes better ( linear or automatic ), are the batteries junk? I bought 3 of them a year ago at a hobby expo for 10 bucks and recently crashed a P-51 because I think I lost reciever power. I am using a Futaba 9ZAP with a 7chanell Futaba FASST transmitter module and 7 channel Futaba R607FS FASST reciever.

How long are nimh good for. I used to race RC cars in the late 80's and am familiar with nicads. I was using the idea of cycling them like I used to do with nicad's and with the new stuff of nowadays (the 720i charger) I can read the amount of mah you put in or dischager out of batteries. But is cycling these nimh batteries a no no???

Any help would be greatly appreciated because I don't want to loose another airplane because of a stupid reciever pack or my not knowing the correct way to charge and check the battery pack. Thanks, Monte.
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Old Mar 20, 2011, 03:48 AM
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I can't help with your charger settings.

But with your receiver packs, if they're the standard AA-size cells, I recommend charging them overnight with the standard wall-wart charger that came with your radio set, instead of 1C charging. The reason is twofold -- first, a delta-peak charger (which yours undoubtedly is when it's in NiMh mode) will stop the charge when it detects the battery voltage dropping ever so slightly, which it does when it's full. The effect is less pronounced with the smaller cells, so the charger might miss it.

Secondly, slow charging (1/10C or so) doesn't harm the cells if it's allowed to continue beyond the point where the cells are full, so it has the effect of balancing the pack by allowing any cells that were lagging behind to catch up after the first cells are full.

If you're only getting 700mAh out of the packs after you've fully charged them, it may indicate that they're at the end of their life. If it's after you've flown them, it simply means you've only used 500mAh during your flying.

But check your charger settings too: Your low cutoff should be at about 0.9v per cell; if it's higher it means your charger won't be taking full capacity out of the pack.
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Old Mar 20, 2011, 04:05 AM
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Thanks

Thanks Abenn for the input. I do have the low volt cut off set to .9v. Like I said I bought these packs 1 year ago new at a hobby expo. The 700mah I speek of is what my charger says when I cycle them.

Question, what is delta-peak? That is what my charger does, is it like it makes 3 attemps off peaking the battery until it succsefullies peak the battery 3 times when each peak is a less than the peak before and shuts off. Do you the meanings of linear, automatic and normal charge cycles?

Thanks again to your reply, Monte.
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Old Mar 20, 2011, 06:42 AM
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When a NiMh battery is fully charged it reaches a peak voltage, somewhere around 1.5v per cell, but can be as high as almost 1.6v per cell.

Because different brands and size have slightly different peak voltages (depends on condition too, I suppose), it's impossible to make the charger cutoff at a precise preset voltage, like we do with LiPos. Instead, NiMh chargers rely on the fact that after they're fully charged, if you keep on charging them, the voltage of an NiMh pack will actually drop slightly. This drop is referred to as the delta ("delta" means difference, in science-speak), and a delta-peak NiMh charger is programmed to stop the charge when it detects the peak voltage going down. On some chargers you can program how far the voltage has to drop before the charger will stop -- somewhere between 0.05 and 0.10v per cell are typical, I believe. Set the value too low and the charger may stop prematurely with a "false peak", and set it too high and it may overheat the battery due to over charging.

For my receiver and transmitter packs I only ever charge them at 1/10C, overnight, without any peak-detect. This may be what one of the charge modes is on your charger, but you'd better wait for someone who's familiar with it to confirm that.

I judge the condition of my NiMh packs partly on how much I can take out and put in, but also partly on how much they lose while sitting from one week to the next. So it might be worth cycling it again after a few days to see if you still get 700 out/700 in.

P.S. I've just found the manual for your charger on line, and here's what it says about the different charge modes for NiMh:

AUTOMATIC – Essentially ignores your setting for CURRENT, but charges at rate determined by the internal resistance of the battery pack. Especially useful when you don’t know what settings you should make due to lack of documentation.
LINEAR – Charges at whatever rate you have selected from start to finish (if the charger detects no problem with settings).
NORMAL – Charges according to your RATE setting but uses an intelligent algorithm to alter current as needed during charge.

I think it's self-explanatory. I've used an automatic setting on my 1210i charger when charging large packs, but I wasn't happy with it because it was heating my packs more than I was happy with. So I've always used the manual setting, setting it for a 1C rate. In the case of your charger, that would be the "linear", or maybe the "normal", setting.
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Old Mar 20, 2011, 07:01 AM
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How to condition , charge , cycle NiMh

http://www.hangtimes.com/rcbattery_faq.html
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Old Mar 20, 2011, 04:10 PM
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Thanks Again

Abben thank you very much for taking the time to help me I appreciate more than I can say. I read my manual several times and was just a little confused about that linear, automatic and normal charge rates. By the way I can adjust the charge and trickel rates by 50mah at a time so I am going to trickle charge it at 100mah overnight and than discharge them and see how many mah I get out of it. If it is still 700mah they are going to the trash. Also the batteries resistance is 334millaohms, does that mean anyting to you on the condition of the battery???

Thanks to Everydayflyer also. I am going to check out your link as soon as I complete this reply. Monte.
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Old Mar 21, 2011, 12:32 AM
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Wow

That was a great website with tons of info. Thanks for the link.
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Old Mar 21, 2011, 03:23 AM
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Originally Posted by TopZueg View Post
... By the way I can adjust the charge and trickel rates by 50mah at a time so I am going to trickle charge it at 100mah overnight and than discharge them and see how many mah I get out of it. ...
On a trickle charge your charger will probably show more mAh going in than really has That's because, as the first cells reach full charge and the other ones are still catching up, some of the mAh will be converted into heat (only small amounts, not enough to overheat the battery) instead of into potential energy. So, the more accurate measure will be how many mAh you can then take out.
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Old Mar 21, 2011, 11:09 AM
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I don't want to start a new thread for this so i'll throw question in here,sorry to go off topic,but it's revelant.What are the downsides of charging a Tx nimh 1500mah pack indefinatley at 50 mah,in other words it's left plugged in until we show up the following weekend,or maybe even 2 weeks?or maybe 2 months.
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Old Mar 21, 2011, 12:26 PM
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1500 / 50 = 30 or a 1/30 C charge rate so IMO not really and problems but others will disagree.

A simple solution used by some is a timer which powers the charger for 2 hours per day. Use a mechanical one and after flying for the day set it max., right after normal turn off time ,switch it on (manually)and it will charge for 24 hours then two hours per day.
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Old Mar 21, 2011, 02:46 PM
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I wouldn't disagree with everydayflyer, but I would add that in my view there's nothing to be gained by leaving it on charge for more than a day.

Sounds like you may be leaving it on charge at your flying site, in which case the suggestion of a timer to give it a couple of hours each day is a good one. If you're doing it at home, just charge it the day before you're going flying.
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Old Mar 23, 2011, 10:21 AM
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Originally Posted by everydayflyer View Post
1500 / 50 = 30 or a 1/30 C charge rate so IMO not really and problems but others will disagree.

A simple solution used by some is a timer which powers the charger for 2 hours per day. Use a mechanical one and after flying for the day set it max., right after normal turn off time ,switch it on (manually)and it will charge for 24 hours then two hours per day.
Hi Charles and Abenn,this is club equipment at the clubhouse,it's there for guest who might show up so we just leave the Tx plugged in to a wall wart type charger that puts out 50mah,when we leave nowone will go back up there to turn on or off anything until following weekend in fact it might not get used for months,it's just a cheap radio so we don't really care,but as i posted what would you guys do,wack it on the peak charger and have to wait or leave it plugged in.We've done this for 2 years and the batts have had it,so sinse i'm the one that has to buy because the others are misers(they'll buy beer),i'm wondering as leaving them to run flat by self discharge and then wacking them at 500mah might be just as bad as leaving them on trickle for god knows how long. Regards Peter
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Old Mar 23, 2011, 02:50 PM
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I would get a 7-day timer like this one http://www.amazon.co.uk/gp/product/B...2HMQP1NAD5876K (but rated for your power supply and plugs) and set it for, maybe, two hours per day.
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Old Mar 26, 2011, 03:55 AM
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Abben you hit the nail on the head with that electronic plug in timer. I have to use one of these for an alarm clock hooked to a home stero system cranked up to wake me up, I am a narcolyptic and have a hard time waking up, and it really sucks. But the electronic timer is easy to set. You can set up to four events on and 4 events off on mine m-f or 7 days a week or particular days and mine is 10 years old. If you are worried some one will leave it dead, just have them set the timer for 24 hours and then go back 2 the 2 hour per day routine. It should always be charged by the next morning for the new person coming to play. He could also tell if some one was there the day before if the charger light is on. That is if you set the normal time for charging like midnight to 2am or something. Just my 2 cents.
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Old Mar 26, 2011, 05:54 AM
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Originally Posted by TopZueg View Post
... If you are worried some one will leave it dead, just have them set the timer for 24 hours and then go back 2 the 2 hour per day routine. It should always be charged by the next morning for the new person coming to play. He could also tell if some one was there the day before if the charger light is on. That is if you set the normal time for charging like midnight to 2am or something. Just my 2 cents.
The timer in my link has a "manual override". If it's anything like my heating control unit timer, that means you can press the manual override to keep it switched on until the next programmed "off". So, the rule could be simply that anyone who uses the battery presses the manual override when they put it back on the charger, rather than fiddle around changing the timer to 24 hours for that one day, and then someone else having to change it back to 2 hours.
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