Flypaper 2

No need to cycle nimh batts. Only the old nicads would retain a memory and needed cycling. I go by the voltage on the trans and pull the plug when it shows about 5.5-4 volts. A couple of weeks of hard use before charging makes it a none issue.

Jezmo

IMHO 200mA is too much to leave the battery connected after it has reached it's peak charge. Mine gets extremely hot after it has reached peak, if left plugged in, so I took the liberty of purchasing a separate battery cover and putting a charge jack on it so I can plug the battery directly in to my regular charger. Of course I kept the original battery cover just in case I need to send it in for warranty. (yes I have a spare pack for that purpose as well) I forgot to take it off charge a couple of times and it stayed on charge for two or three days. The battery compartment was very hot, so much so I was worried it might cause a fire. That is what prompted me to get the spare cover and make the charge port mod. Also, the original 2000mAh battery failed in less than six months probably because of the abuse of overcharging those times it was left on. Horizon graciously offered to replace the battery under warranty if I would send the radio in and let them determine if it was defective. If not, then the standard shop labor rate would apply and I would have to pay for the battery. Needless to say, it was cheaper to just purchase a pack than to pay for shipping and possible labor charges if they determined my 5 month old pack had been abused by forgetting to unplug the transmitter after the battery was fully charged. Now that is customer service at it's finest. A five month old radio (they had only been out that long as I received one of the first sent out on preorder) that has a charger built in and I'm supposed to believe there's something I could have done to cause the failure.

Point is, I would NOT trust the built in charger with a NiMH pack. Either pull the pack and charge with good equipment or make an adapter and install an external charge jack on the cover. Sorry for the rant at the end of the last paragraph but it frustrates me when companies take that position. Especially when it would have cost them less than 15 bucks (their cost for a new pack) to keep a happy customer that spends thousands each years on this hobby, much of it with them. Oh well I guess I have choices (there's always Tower and also the Chinese) so why complain.

garywaters

My Feedback: (1)

I just bought a NEW DX8 from Horizon Hobby a few weeks ago.

The battery voltage was 4.8V, so I plugged in the wall charger and started charging the battery..

After 4 hours and 50 min the DX8 was getting hot! I removed the battery door and the NiNH pack was 115 Deg F.   I called Horizon Hobby and they said to send it back to them... 

 

Jezmo do you know how hot yours got?

I’m sure if they replace  it,,,,,,, the new one will do the same.

I don’t want to remove the battery every time I charge it.

And now,,, How can I trust it to charge a LIPO?

COME ON HORIZON HOBBY WHAT ARE YOU THINKING????

garywaters

My Feedback: (1)

When I called HH the guy on the phone acted like he never heard of this before.

And could not tell me what the max temp should be, Just that it is to hot.

Futaba is looking better and better.

Zeeb

My Feedback: (41)

GO FOR IT!!!!

If you think Horizon has crummy CS, wait 'till you deal with Hobby Services....

garywaters

My Feedback: (1)

I'm willing to give them a chance like I did HH !!!  

AndyKunz

Gary,

115F is not too hot. You can take them up over 125 w/o a problem.

The power to the battery is limited to 200mA = 1/10C, a trickle charge. What is the voltage? Have you checked it on an external charger to see if it has peaked yet?

Andy

garywaters

My Feedback: (1)

Hi Andy

When I charge a 4.8V NiMH pack,  I’ll charge it at 1A or 1.5A and have the temp safety cut off at 100Deg F.  This should charge the battery around 85 to 90 % full.

Charging with the temp over 115 Deg F will shorten the life of the battery.

When I called HH and told him what battery temp I was getting he told me it was way too hot and I needed to send it in……I ask him to check and make sure that the battery temp of 115deg F was too hot before I send it in. I did not want to send it in for nothing.

So is the guy answering the phone at HH knowledgeable on the product?

Onlybatterypacks   com

NiMH Battery Pack Maintenance

1.) If you are having trouble charging your NiMH battery pack –trickle charge at 1/10 C (capacity) to wake them up and reach full capacity.

This also applies to packs that have been in storage.

2.) Trickle charge time listed in the chart above is for fully discharged packs.

Always let the batteries cool to room temperature before charging. Heating your NiMH battery pack up beyond 110 F degrees indicates

an overcharge condition and will lead to cell damage, loss of voltage and capacity.

3.) Nickel-Metal Hydride cells are more sensitive to heat than Nicads, so be sure not to overcharge them. Overcharging may cause the cells

to vent and loose capacity. It is recommended that you charge with a charger that has an adjustable Delta Peak detection circuit (set to

.01-.02v) eliminating the possibility of overcharging. Nickel-Metal Hydride cells will quickly get hot after the voltage starts dropping, so

keep track of the time on the charger.

Jezmo

Yes Gary mine was getting to 115 and even more if left on longer. My solution was the modification so I can use my peak charger. No more worries now and otherwise I consider it a great radio.

1004ron

Obviously the trickle charge rate is too high, based on the reports of overheating when leaving a partially discharged DX8 on charge for a few hours.

I would like to do what I did with my DX7, and that is cut the cord off the wall charger, attach a Deans plug and use my Hyperion charger set for a max current of 200ma and a time cut-off. Of course this way it will not detect a full charge and stop charging on the timer, which in my opinion is safer than the built-in charger that doesn't shut off and in most cases overcharges if left on charge too long.

garywaters

My Feedback: (1)

Up date

HH called and said that 115 Deg F when charging the DX8 with the 4.8V 2000mAh NiMH is ok..

Then I reminded him that HE stated in our first conversation, that 115Deg F was way too hot and may have damaged the DX8, and I needed to send it in.

Now 5 day’s later 115 Deg F is normal ….

Nothing,,, Drives me more than incompetence…  

 Onlybatterypacks has this on the website.

 

Always let the batteries cool to room temperature before charging. Heating your NiMH battery pack up beyond 110 F degrees indicates

an overcharge condition and will lead to cell damage, loss of voltage and capacity.

Jezmo you’re right !! for now the battery is coming out when charging.  

This winter I'll  check into converting everything over to Futaba.

Jezmo

I got tired of taking the battery out and for a couple of dollars fit this Ernst charge receptacle on my battery cover allowing me to charge, discharge or whatever makes me happy without removing the cover.

garywaters

My Feedback: (1)

Jezmo,   thank you for the picture.  When you charge the battery, does the DX8 see the volts, or just the battery ???? 

fizzwater2

My Feedback: (61)

I just charge mine and use it. I don't leave it on the charger for a long time, it's just like a standard overnight charger. C/10.. It's NOT a peak charger, auto trickle, etc.

You could also get one of those 110V timer deals used for outdoor lights, etc - just set it for however many hours you want to charge, start it, and pull it off the next day before the charge cycle starts again.

I do like the idea of the added charge jack - that way I could use my Ace digipulse with adjustable current and auto trickle. Hm. Might have to look into that.

garywaters

My Feedback: (1)

Hi Fizzwater2

The issue is the battery temp can get  115Deg F   ( over charge) or more in a few hours.
How long would you set the timer for?  

I think a good Peak charger on the battery is the way to go (( Like Jezmo has )) until HH can fix the issue ........

Or   just go with the lipo,,,,,,, and charge it out side in a lipo bag just in case it over charges!!!! 
 

fizzwater2

My Feedback: (61)

I don't trust peak charging NIMH batteries. NiCd, yes, NIMH, no. It's just me. I'm not a big fan of NIMH batteries, but I'm also not going to spend 70 bucks for the Spektrum LiPo for the DX8.

Depends on how low the voltage gets before I charge it. If it gets clear to 4.2V or so, I'd probably do ten hours. If it's still 4.8 or above, probably only 3-4 hours.

garywaters

My Feedback: (1)

Fizzwater2
will you please check the battery temp when you charge it and let us know how hot it gets ??
Thank You...

Do they all get hot or just a few????????????/

fizzwater2

My Feedback: (61)

So far I've only had to charge the radio twice.. it lasts a LONG time between charges.

I'll see if I can dig out my thermocouple probe one of these days, but don't hold your breath. I don't charge it very often, don't get that much chance to fly!

pilotpete2

If the internal charger was in fact charging at 200mA, or C/10. The cells would never get more than a little warm if left on charge for the normal 14-16 hours that a C/10 charge takes. I suspect that the charge rate is higher than what it's supposed to be.
Pete

flyallday

I checked if my battery the last time I charged - about 2 weeks ago - as I was curious if it got warm. It got slightly above room temp after a 6 hour charge. Flying twice a week, I charge once a month.

Harry

Jezmo

Just the battery. The main switch is between the battery and the internal circuitry of the DX8.

garywaters

My Feedback: (1)

[img]D:\RC stuff\DX 8\DX8 Charging[/img]

Jezmo

Gary something happened to your picture, it isn't showing up, at least not for me.

garywaters

My Feedback: (1)

Ihope this works ,,,,,

garywaters

My Feedback: (1)

FYI update,

Hi Jezmo and all.

I tested out the DX8’s charging system.

As you can see in the picture, the charging Volts, charging Amps, and battery temperature data was taken.

If the battery was charged inside the DX8, the battery temperature could get well over 115 deg F.

This high temperature can be mistaken for an over charged battery condition. 

The high battery temperature is a result of the battery being charged and the DX8’s internal charging system adding heat inside the DX8.

If you remove the battery door on the DX8 when charging, (to allow ventilation)  , the battery will not get as hot.

Gary