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Battery problem

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fly boy320/04/2018 21:56:23
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3143 forum posts
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Hi all, I have been given a few ni- mh Reciever batteries 4.8 v. I only have a Futaba nicad trickle charger at the moment. Will this be suitable for charging. . Thanks.

Denis Watkins20/04/2018 22:11:19
2671 forum posts
136 photos

Nimh packs should not be overheated or left overnight. They charge at 1/10th C

It sounds like the charger you have is the low output wall charger that is normally used

Martin Harris20/04/2018 22:11:34
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NiMH batteries are better charged with a "smart" charger but can be charged with a standard "wall-wart" one. The problem is that they don't like being overcharged and it's difficult to avoid it unless you have a very good idea of what has been taken out (or self-discharged).

Suitability also depends on capacity and the charge rate given by the charger. Are these fresh batteries or have they been standing after earlier use? NiMHs don't have a very long service life like good quality NiCds had.

It would be better to invest in a charger that can be set to a suitable rate and detect the fully charged state. There are many available for not too much money.

fly boy320/04/2018 22:26:30
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3143 forum posts
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Thanks Martin. I don't think they are fresh, (friend has gone electric from ic. ) Can you recommend a budget charger that charges lipos as well ? Thanks. For Dennis, yes it's only a 70 MA output.  I see HK have a charger to fit my budget lol   Lipo Balance charger ImaxB6  would this be suitable.?  Cheers

Edited By fly boy3 on 20/04/2018 22:27:28

Edited By fly boy3 on 20/04/2018 22:35:33

Mike Blandford20/04/2018 23:41:23
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What capacity are the batteries? As long as they are at least 700mAh, then a trickle charger of 70mA may be used. NiMh batteries will handle being charged at 1/10th 'C' for over 24 hours, indeed, this type of charging is needed to ensure all the cells are fully charged (balanced).

Even if a "smart" chrger is used most of the time, a trickle charge is needed occasionally to 'balance' the pack.

My NiMh batteries have lasted for many years without any problems.

Mike

Martin Harris20/04/2018 23:47:38
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7503 forum posts
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That should be fine - it will charge virtually any battery you're likely to use. More importantly, it has the capability of discharging them so that you can do an occasional check on how much they can deliver safely. Far better than finding out that a battery has degraded half way through a flight!

Denis Watkins21/04/2018 08:01:20
2671 forum posts
136 photos

Agreed with Martin

The B6 is a very versatile little charger with leads provided, and auto shut off

fly boy321/04/2018 10:54:23
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3143 forum posts
11 photos

Cheers all, does any one know if charger comes with input leads or do I order seperatly,cannot tell from picture on web site. ? Thanks

Edited By fly boy3 on 21/04/2018 10:55:12

Denis Watkins21/04/2018 13:23:20
2671 forum posts
136 photos

Yes on input lead

Crocodile clip for 12v battery supply, or onto mains unit

fly boy321/04/2018 17:40:05
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3143 forum posts
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Thanks all for your help, seems I have been mistreating my nmhs. I have learned a lesson. Smart charger on order from HK. Cheers

Mike Blandford21/04/2018 18:28:25
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351 forum posts
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Mistreating in what way?

Low current trickle charging is fine, and doesn't damage NiMh cells. For example, I just checked a datasheet for a 1100mAh AAA cell. This specifies you may charge at 45mA for a year continuously! As I mentioned above, only using a "smart" charger will lead to cell imbalance over time, so then you will need to do a trickle current charge to balance a pack.

Mike

fly boy321/04/2018 21:08:52
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3143 forum posts
11 photos

Hi Mike, most of them are 2500 mAh. I assume the mistreat ment was leaving them overnight or longer, thus overcharging them. Am I wrong ? Thanks

Denis Watkins21/04/2018 21:25:11
2671 forum posts
136 photos

Woe lads, just on unattended charging, never do it

No matter what the spec, what the sheet says, do not charge unattended, for you and your family's safety

At the field, if a NiMH is less than full then occasionally 1C charge as flying weather is scarce.

Otherwise trickle or 1/10th C charge

Mike Blandford21/04/2018 22:06:39
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351 forum posts
12 photos

I agree to not charging lipos unattended, but where are you getting information from regarding NiMhs?

Many devices have inbuilt NiMh cells that are on continuous trickle charge e.g. cordless 'phones. They don't say "don't charge overnight"!

A 2500mAh NiMh may be charged at 250mA for 24Hr, at 70mA they will be fine for months. From flat at 70mA they will take around 36 hours to fully charge.

Mike

fly boy322/04/2018 10:20:06
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3143 forum posts
11 photos

Problem on page ?

fly boy322/04/2018 10:30:19
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3143 forum posts
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Sorry boys, sorted !!!! It's called a senior moment lol

fly boy322/04/2018 12:49:11
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3143 forum posts
11 photos

I'm sure Dennis is speaking about lipos, and we all know the damage unattended charging can do. Re my 2500-2600 Nmh batts. I wonder if these are overkill ? Wondered what size is normally used by others when flying sports models such as Acrowot and Maricardo. ? Cheers

ken anderson.22/04/2018 13:24:10
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8000 forum posts
728 photos

hello FB3in the good old days last century,500-800 m/amp NiCad's were the norm ........ running 4-6 servo's/35 MHz gear.... now we are spoiled for choice....don't worry about overkill....your nmh's will be ok..

ken Anderson...ne...1....overkill dept.

fly boy322/04/2018 15:05:34
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3143 forum posts
11 photos

Thanks Ken, yes if I remember correctly when I started I think 1000mah was considered large lol. Thanks

Edited By fly boy3 on 22/04/2018 15:06:02

Denis Watkins22/04/2018 15:24:39
2671 forum posts
136 photos

As a guide at the field FB, as I do not fly my own plane all the time, the lads ask me to check theirs in the air

Assuming I get 5 x 10 minute flights from a 5 servo Cub, I put in 300ma back into my pack

As Ken said, 500ma used to last us the day

It is difficult to find 1000mah packs for sale now, but the 2200 - 2300 ma packs will suffice all day

But still check the pack regularly through the day, as a stalled servo can change all this

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