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[richald]

I recently purchased 3 off, 3700mAh 7.2V Ni-MH race packs from Component Shop.
 
I want to charge them using a shiny new SKY IMAX B6AC charger - can anybody tell me
what the safest charging rate would be for theses packs? - I have seen 0.5A
recommended for slow charging, & up to 3.7A for a fast or faster charge - what is safe?
 
What maximum voltage should I see while the packs are charging?

Regards

Richard Alderton

[essex2visuvesi]

3.7A should be safe enough just keep an eye on the pack temperature.


Usually 1 charge NiHm's at about half the capacity so 1.8A for a 3700 pack

[richald]

Thanks for that -

I am charging a race pack now at 3.7A max,
it has been running for 40 minutes or so,
and the pack is just starting to get warm

Richard

[essex2visuvesi]

If you watch the display on the charger, you will see the Current start to drop off towards the end of the charge.

[Netleyned]

Hope it's a genuine Sky model with the hologram and checkable serial no.
The cheapos flooding the bay are a bit erratic with regard to charging current.
At least Hobby King give you the choice of a pukka one or the cheapo.

Ned

[essex2visuvesi]

I've been running a B6 for about 5 years now, still going strong

[richald]

I was tempted by a knock off one, but chickened out and bought the pukka item
with the hologram on the back - probably better since the value of your batteries
will usually outweigh the cost of the charger. I haven't checked the serial number yet!

I bought mine from Banggood - they offer the same service as Hobbyking -
to supply a real or a fake one.

Richard

[Netleyned]

No problem with the pukka ones.
As to the others it's pot luck.
Some  last and work as good as the
Real ones.
The blue esc's are a case in point
I have one in a dickie conversion and
it's going strong after three years.
Others I have seen emitted the magic smoke
on the first trip to the lake.

Just seen your post Richard.
Had a lot of gear from Bangood and no issues 

Ned

[essex2visuvesi]

I was tempted by a knock off one, but chickened out and bought the pukka item
with the hologram on the back - probably better since the value of your batteries
will usually outweigh the cost of the charger. I haven't checked the serial number yet!

I bought mine from Banggood - they offer the same service as Hobbyking -
to supply a real or a fake one.

Richard

Ah Banggood.... get some funny looks when you mention that site at work lol
Bloody good sight for electrical bits thos

[richald]

I have stopped the charging - the pack seemed to get very hot after 50 minutes.

I shall let it cool down and restart at 1.8A charge rate


Richard

[inertia]

Charging NiMH cells at the C rate (in this case 3.7A) is fine. Component Shop recommend you use a reduced rate for the first few charges of a new pack. I'd suggest 1.5A. It's when you start trying to stuff 4 or 5 times C into them that the party often kicks off. Don't worry about the pack getting warm - it's part of the process. If it gets too hot to touch then do as you have done and switch off!
You'd be looking for something like 1.4 or even 1.5v per cell in a new pack at full charge. This will rapidly drop to 1.2v as the pack discharges. Discharge shouldn't be allowed below 1.0v per cell. As a pack is used over time the fully-charged voltage will slowly drop to around 1.3v, but if you treat it properly then it's reasonable to expect 1000 discharge/recharge cycles. You'd be lucky to get 100 from a comparable LiPo.
DM

[richald]

Hail to the Chief!

Thanks Dave!

I shall stick to the 1.5A max for the early charges - hope I haven't done any lasting harm using 3.7A.

I suppose I should go and have a sit down now, and read the instructions that came with the charger
I did have a quick look but it doesn't seem to be a model of clarity when talking about NiMh batteries.

Richard

[bj]

the pack seemed to get very hot after 50 minutes.

Spend some more money and buy the temperature probe for the charger. The iMaxB6 does monitor battery temperature as well. Default limit is set at 80ºC
[/size]See
[/size]http://www.ebay.co.uk/itm/NEW-SkyRC-Temperature-Probe-Cable-Sensor-for-Imax-SkyRC-Charger-Futaba/252035673847?_trksid=p2141725.c100338.m3726&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D20150313114020%26meid%3Deb14795bb1664b23a3aa9f4f14f3c114%26pid%3D100338%26rk%3D8%26rkt%3D15%26sd%3D252035726634

[TomHugill]

Hail to the Chief!

Thanks Dave!

I shall stick to the 1.5A max for the early charges - hope I haven't done any lasting harm using 3.7A.

I suppose I should go and have a sit down now, and read the instructions that came with the charger
I did have a quick look but it doesn't seem to be a model of clarity when talking about NiMh batteries.

Richard

I wouldn't charge over 1 amp. Those imax b6 have a really iffy delta peak which always cuts out way too early if you fast charge. I found 1A to be the most that would charge my packs properly.

[grasshopper]

Don't new NimH cells give you a multiple of the C rating anymore?
In the days when we went from NiCD to NiMH  for RC cars and buggies we were charging at a higher rate typically at the maximum 5A that our chargers could supply to get the batteries charged and peaked before race heats and that was for lower capacity batteries so for the cells that I had of 2200 mAh that was just over 2C, yes they got hot but never vented

[richald]

I wouldn't charge over 1 amp. Those imax b6 have a really iffy delta peak which always cuts out way too early if you fast charge. I found 1A to be the most that would charge my packs properly.

If you look back to reply # 4 from Netleyned it seems that the iffy charging was apparently as a result of using
a cheap knock-off charger -

The cheapos flooding the bay are a bit erratic with regard to charging current.

I bought a pukka one with the 'proper' hologram on the underside so it may be that I won't encounter
the problems that you have been experiencing ?

grasshopper - Component Shop only state '35A discharge' capacity for the 3700mAh race packs I am using.

Richard

[grasshopper]

All things being equal and having a legit, reliable smart  charger, setting it to NiMh and setting the charge current I'm pretty sure you can speed up the charge time.
5 amps is only 1.35 times the capacity and the detection device should kick in and switch to trickle.

[TomHugill]

If you look back to reply # 4 from Netleyned it seems that the iffy charging was apparently as a result of using
a cheap knock-off charger -

I bought a pukka one with the 'proper' hologram on the underside so it may be that I won't encounter
the problems that you have been experiencing ?

grasshopper - Component Shop only state '35A discharge' capacity for the 3700mAh race packs I am using.

Richard

Mine is a genuine charger, friends I know with it have the same issue.

[inertia]

Mine is a genuine charger, friends I know with it have the same issue.

Sorry, but how would you distinguish a 'proper' hologram from a fake one?
If you Bly Blitish at least there's some redress in law.
Is common sense becoming an endangered species, I wonder?
DM

[RAAArtyGunner]

Sorry, but how would you distinguish a 'proper' hologram from a fake one?
If you Bly Blitish at least there's some redress in law.
Is common sense becoming an endangered species, I wonder?
DM

Good point
Also applicable to Microsoft knock offs.

 

[Netleyned]

There are no holograms on the fake BMax.
On Fake Britain last night it showed how to spot a genuine or fake CANON hologram.
Looks like there are a lot of fake Lithium Batteries out there.


Ned

[TomHugill]

Sorry, but how would you distinguish a 'proper' hologram from a fake one?
If you Bly Blitish at least there's some redress in law.
Is common sense becoming an endangered species, I wonder?
DM

Also as stated before hobbyking sell both, mine is the genuine one. I'm just trying to give the benefit of my and other experience charging NIMH with this particular charger so giving me stick about it isn't appreciated....

[richald]

Netleyned is quite right about there not being a hologram on the fake Bmax chargers.

I decided to go for the B6 because, amongst the people using chargers at my model
boat club, by far, most of them were using B6s, which has got to be a reasonable
recommendation.

Richard

[Bob K]

Personally I would always charge an NiMh, or indeed any battery, at a bit below it's recommended charging rate, and disconnect it from the charger when full.  It is kinder to the battery and helps extend active life.  I have numerous NiMh's that have been charged and used at least once a week for over a year.  The day before sailing I check the weather then charge the batteries I will need.

I can't see the point in fast charging which could damage even a genuine quality battery.  On the BBC One Show last night were some very graphic footage of simulated fast charging fake phone/camera Lithium's seized by trading standards.  ie:  Always buy from a reputable dealer. "Bargains" can come back to bite you.