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Batteries & Chargers Discuss Li-P, Li-Ion, NiMh, Nicad battery technology and the chargers that juice 'em up!

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Old 08-09-2014, 03:22 PM   #1
Fishbonez
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Default NIMH unknown

Good morning,
I have a NIMH battery that came with a SIG Something Extra (yep a gasser shhh don't tell no one)
I am trying to charge it but I don't know what the voltage capacity or MAH or nothing is and I am afraid to over charge it.
I am using a HITEC X4 Multicharger setting on 1 amp and I am using a Futabs Br-2000 battery checker when I check it on 4.8 and 6.0 volts at 1amp load tests are good but 7.2 load test is bad. Voltage is currently 6.5 volts. I fear overcharging this battery. I am assuming it could b as disastrous as an overcharged Lipo. I just don't know. Anyone have any thoughts. I don't know if my charger will tell me that the battery is full because it will only allow me to set the amperage and not max voltage. Any help would be appreciated. I refuse to to fly the plane unless I am confident the the Rx is battery is charged
Thanks in advance

Happy flying may your crashes be limited and if they are not limited let them be cool.
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Old 08-09-2014, 04:26 PM   #2
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It appears that you have a 5 cell battery. A safe way to charge it is to use one of the old wall warts that come with many of the transmitters/receiver packages. They usually put out about 50ma or 100ma. If so, you can just connect that to your battery and leave it on for 10 to 16 hours. The battery should slightly increase in temperature when it is fully charged but; at this low rate of charge you will not damage it by overcharge. Now, to see what the capacity is, discharge it at around 200 to 300 ma and see how long it takes to drop to 0.9 volt/cell (4.5 volts if this is a 5 cell battery). The time (in hours to discharge down to 0.9 volts/cell) times the discharge current will tell you what the ampere hours capacity is. Unless you are willing to spend all the time in checking it out and if your plane has much value, maybe you should just buy a new 5 cell Nixx type battery of sufficient ampere hour capacity.
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Old 08-09-2014, 04:58 PM   #3
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Originally Posted by Fishbonez View Post
Good morning,
I have a NIMH battery that came with a SIG Something Extra (yep a gasser shhh don't tell no one)
I am trying to charge it but I don't know what the voltage capacity or MAH or nothing is and I am afraid to over charge it.
I am using a HITEC X4 Multicharger setting on 1 amp and I am using a Futabs Br-2000 battery checker when I check it on 4.8 and 6.0 volts at 1amp load tests are good but 7.2 load test is bad. Voltage is currently 6.5 volts. I fear overcharging this battery. I am assuming it could b as disastrous as an overcharged Lipo. I just don't know. Anyone have any thoughts. I don't know if my charger will tell me that the battery is full because it will only allow me to set the amperage and not max voltage. Any help would be appreciated. I refuse to to fly the plane unless I am confident the the Rx is battery is charged
Thanks in advance
Yeah, a simple wall wart charger would be the best thing to use on this type of battery. If it's "AA" sized battery pack, make certain its a 5 cell unit.

As for me, I'm not a fan of using those AA type Nih battery packs with any radio running on 2.4 Ghz, especially on the larger models with big aileron/rudder/elevator surfaces.

If your battery pack has been around awhile, it would be a good idea to cycle test it on a battery analyzer.

You might want to check out one of those LiFe battery packs for your receiver. They have plenty of capability of running just about any size servo system in your models. Their cost is similar to a new Nih pack.

Just don't leave the receiver switch on!!! That is hard on them, and can kill them.

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Old 08-09-2014, 10:40 PM   #4
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Should be easy to count cells, multiply by 1.2 for nominal, 1.4 for full.

AA NiMh (that I know of) came in as low as 1000 mah and as high as 2300 mah... Most common was 1500 mah.

Its very rare to overcharge a NiMh to the point of damage at C/10 rate. But I have had one pack burn on a common wall-wart charger. (yes, smoke, flames and stink leaving ashes and melted metal)

The peak detection chargers depend on the battery getting hot, which causes voltage to drop + internal resistance increase rapidly and that is sensed as a full battery. Above 2C charge rate this can be a bit hard on the battery.
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Old 08-09-2014, 11:47 PM   #5
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Little secret about Nickel Chemistry Batteries. The are both the hardest and easiest batteries to charge. If you want to fast charge, then it is difficult to detect when they are fully charged. Since they cannot be constant voltage charged, requires processing to determine full charge looking for a sudden change in voltage and/or temperature. .

But then there is a very easy way, takes a while, but very easy. Limit the charge to around C/20 of the battery rated AH spec. Place it on the charger and forget about it. Come around every few hours like next morning and just feel the battery. When it fells warm, it is fully charged. If you limit to C/20 there is no way to over charge the battery and vent gas. The battery will remain cool while charging. Once it is fully charged with a small current applied it will warm up a little to burn off the charge, and it will also reform dissolve some larger crystals and be reformed on the plates.

Slow charging Nickel or really any battery chemistry is the gentlest and most thorough saturating charge you can use. With the nickle chemistry you can apply C/20 pretty much indefinitely on a Nickel battery to keep it at 100%. Pretty common practice Handie Talkies used by first responders and radio operators.

Final note here, sounds like you might have a 4-cell pack. Regardless here is what you can do if you want a faster charge. Estimate the AH Capacity. 2000 mah is a great guess. Set your charger to charge at C/2. So if it is a 2000 AH battery charge at 1 amp. Keep a charge on it until the battery starts to warm up. A Nickel battery has two signatures when fully charged. 1 they will get warm when fully charged up if charged less than 1C. 2. they have a sudden rise in voltage. Just charge at C/2 and let your hands tell you when they are fully charged up. Not hot to touch, just comfortable warm.
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Old 08-12-2014, 02:24 PM   #6
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Good morning,
Hey thanks every one for the help. Is definitely a 6 volt battery and I flew the plane yesterday without a problem and recharged it now I will have to figure out the mah and how many cells it has. The unfortunate/fortunate problem I have is the person who built the plane put the battery under te fuel tank. I assume for CG purposes and its a real bear to get to and does not appear to have any writing on it that I can tell It definitely is not one of those AA battery type batteries and almost looks like a life battery but I don't wish to make any assumptions.

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Old 08-14-2014, 09:49 PM   #7
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Fish ... if it's a NiMH pack .... then what are you concerned about ?

Get your LiPo charger ... set it to NiMH and set a rate of 100mA or whatever lowest rate your charger allows ... usually you cannot adjust voltage setting on NiMH .... plug in and start charging ... let the charger do its job by cutting out at full.

Basically it detects the slight voltage drop at Delta Peak ... there are various online sites that claim NiMH has less definite peak detection as in NiCd ... but I've never seen any evidence of peak detect failure in many years of use ...

There is no need to play temp games or such ... sorry to some - but it seems that all the decades of NiXX pack use has been forgotten ... and some comments made relate actually to NiCD not NiMH.

Fish - you say 6V ........ then its DEFINITELY a 5 cell pack ... and actually NOT fully charged.... IF NiMH. But again - if it's a NiMH pack - you don't need to worry about the voltage when charging - the charger will look after that ...

I use NiMH in my gassers ... and I love 'em ... I charge via the switch harness in situ ... never worry about things like with LiPo's .... to be honest - I've yet to see any real reason in my models to ever change from them.

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Old 08-14-2014, 11:56 PM   #8
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Originally Posted by solentlife View Post
I use NiMH in my gassers ... and I love 'em ... I charge via the switch harness in situ ... never worry about things like with LiPo's .... to be honest - I've yet to see any real reason in my models to ever change from them.

Nigel

Add me to the list of folks that don't like using LiPo batteries for receiver power. There are to many reports of having to store your LiPo batteries under a storage mode. Tests that I've done on LiPo batteries, is when and if they go bad, they open up, resulting in inability to operate your receiver/servos.

If your servos are not rated for LiPo use, you've got to add a voltage regulator. These regulators are reliable, but it's just something else that COULD go wrong.

If your receiver/servos are rated for a 5 cell Nih pack, a two cell A123 or LiFe pack is a direct drop in, with almost identical voltage characteristics. And, under high currents that those giant scale high power servos pull, an "AA" type 5 cell Nih pack can't come close to an A123 or LiFe pack. About all that can kill an A123 pack, assuming the use of a balancing charger, is leaving the receiver switch on for days.

That voltage drop on a Nih pack at peak charge is much less than the old Nicad packs. That voltage drop is on the order of 0.5% less than the peak voltage. Something easily measured with the quality electronics now available.

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Old 08-15-2014, 06:29 AM   #9
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Originally Posted by solentlife View Post
Fish ... if it's a NiMH pack .... then what are you concerned about ?

Nigel
Well I have to admit all my flying time has been with the use of Lipos and you now how much info on what not to do with Lipos. So this being my first nitro plane with a NIMH in it I actually crashed because I let the battery run down so I was doing my best not to let that happen again. during the repairs I discovered the battery was not a "AA" type NIMH battery and it had no info on it whatsoever. It looked like a life battery so I just got overly concerned. Also the instructions that came with my charger were very vague to say the least when it came to talking about charging NIMH so I admit I felt like I did not know what I was doing.

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Old 08-15-2014, 02:53 PM   #10
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The NiMH program on the Hitec charger should be just fine and you shouldn't have to do too much about it.

That being said, I have a 2s LiFe (genuine A123) in one of my gassers and I can highly recommend it! Behaves like a LiPo, but supposedly safer and it has a voltage that suits non-HV servos. My other gasser has HV servos, so I'm running 2s LiPo there.

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Old 08-16-2014, 07:13 AM   #11
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Originally Posted by NJSwede View Post
The NiMH program on the Hitec charger should be just fine and you shouldn't have to do too much about it.

That being said, I have a 2s LiFe (genuine A123) in one of my gassers and I can highly recommend it! Behaves like a LiPo, but supposedly safer and it has a voltage that suits non-HV servos. My other gasser has HV servos, so I'm running 2s LiPo there.

IMHO, those aluminum shell covered A123 cells are FAR safer than LiPos in a catastrophic failure mode. Like crashing, or puncturing with a nail.

Don't try this with a LiPo battery!
https://www.youtube.com/watch?v=rb_J2QQ0k-4

As for me, four years ago, I screwed up big time, and blew out a two cell A123 battery. No fire, just a lot of carbon dust all over my workbench. Had that been a LiPo, I'd have been looking for a new home.
http://www.wattflyer.com/forums/showthread.php?t=58745

And, the use of A123 cells for big gassers and giant scale models: The two cell A123 pack is a direct drop in replacement for a five cell Sub C Nih battery pack. The voltage discharge curves at low currents are nearly identical. At high currents, over 15 Amps, the A123 cells do better than the 5 cell Sub C Nih packs. (I'm running my A123 cells for motor power, at 40 Amps max. They only get slightly warm.) The two cell A123 pack is one half the weight of a 5 cell Nih Sub C battery pack.
http://hangtimes.com/a123_batteries_for_giants_faq.html

Two years ago, a club member lost a big Bipe powered by a 50 cc gasser when the horizontal stab came off at full throttle, 10 feet off the deck. The model went straight in. The biggest part of what was left of the model was smaller than your hand. The 3200 Mah LiFe battery pack was bent at 45 degrees, and was smoking, due to internal short circuits. There was absolutely no fire. It was to hot to touch. After about 15 minutes, those internal shorts burned clear, and that battery pack still measured 6.6 Volts on its DC output!

Two years ago, I saw a big electric model with a 10S LiPo pack go in, after a midair. That LiPo pack ignited with flames, burned for 15 minutes, and NOTHING would put it out. Not even several buckets of sand.

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