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Author Topic: 7.2V 2000mah 6S AA NiMh Pack - On Smart Charger  (Read 835 times)

Richard Houston

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7.2V 2000mah 6S AA NiMh Pack - On Smart Charger
« on: June 09, 2019, 05:31:24 AM »

I went out and bought a smart charger and I am trying to figure out the system, I have the battery charging on Auto and NIMH at 1A but i'm trying to figure out where to set the DeltaV amount at and also what voltage will show roughly when the pack is Full while charging it, right now the charger is showing me the pack is currently at 8.72v while on charge.


So my ultimate need to know is the end voltage while its charging so that I wont le the charger cross that level.
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malcolmfrary

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Re: 7.2V 2000mah 6S AA NiMh Pack - On Smart Charger
« Reply #1 on: June 09, 2019, 09:06:52 AM »

I went out and bought a smart charger and I am trying to figure out the system, I have the battery charging on Auto and NIMH at 1A but i'm trying to figure out where to set the DeltaV amount at and also what voltage will show roughly when the pack is Full while charging it, right now the charger is showing me the pack is currently at 8.72v while on charge.


So my ultimate need to know is the end voltage while its charging so that I wont le the charger cross that level.
Smart chargers that I have seen usually either ask how many cells are involved, or sometimes tell you.  8.72 is pretty fully charged, and I wouldn't try to go beyond that slamming 1A into a 2500mAH battery, but you will probably have noticed the battery getting noticeably warm if the charger hasn't calmed itself down.
To quote from Wikipedia -
Quote
For Nickel-cadmium and NiMH batteries, the voltage across the battery increases slowly during the charging process, until the battery is fully charged. After that, the voltage decreases, which indicates to an intelligent charger that the battery is fully charged. Such chargers are often labeled as a ΔV, "delta-V," or sometimes "delta peak", charger, indicating that they monitor the voltage change.
The problem is, the magnitude of "delta-V" can become very small or even non-existent if (very) high capacity rechargeable batteries are recharged. This can cause even an intelligent battery charger to not sense that the batteries are actually already fully charged, and to continue charging. Overcharging of the batteries will result in some cases. However, many so called intelligent chargers employ a combination of cut off systems, which are intended to prevent overcharging in the vast majority of cases.
A typical intelligent charger fast-charges a battery up to about 85% of its maximum capacity in less than an hour, then switches to trickle charging, which takes several hours to top off the battery to its full capacity.
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imsinking

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Re: 7.2V 2000mah 6S AA NiMh Pack - On Smart Charger
« Reply #2 on: June 09, 2019, 10:20:48 AM »

A good smart charger will set all these your asking about automatically, the GENUINE ones that is . . .there's a load of counterfeit chargers around of popular makes , I use an imax B6 (a genuine one will have a code that you can check on the RC site) turnigy are good too BUT if your paying less than 30 for one it may be a fake , same applies to most smart chargers .
You set your own charge rate, in your case 1amp for the first few charges , then up to 1.5amp from then on , don't charge at the full rate of your cell pack it'll shorten pack life considerably , invest in a heat sensor lead (a good charger will have a port for it) 8.4v -8.6v will be fully charged, you cant go by the miliamp figure displayed as there is probably remaining charge in the pack, its not wise to fully discharge a pack .
A pack will warm up as its charging , BUT (need a heat sensor here) the cells can short out internally & temperatures run amok , I speak from experience here  O0  threw the pack out into the yard & it smoked for quite a while . . .
Bill
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Richard Houston

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Re: 7.2V 2000mah 6S AA NiMh Pack - On Smart Charger
« Reply #3 on: June 09, 2019, 12:54:04 PM »

Charger is a HTRC AC/DC100


But for NIMH you have to set the DeltaV manually but the charger does count the cells for you yes but that DeltaV guestimate is a pain. by default it starts the DeltaV at 4 but that is way too low otherwise like I said above the charge stops around about 30% in
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malcolmfrary

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Re: 7.2V 2000mah 6S AA NiMh Pack - On Smart Charger
« Reply #4 on: June 10, 2019, 09:34:18 AM »

Charger is a HTRC AC/DC100


But for NIMH you have to set the DeltaV manually but the charger does count the cells for you yes but that DeltaV guestimate is a pain. by default it starts the DeltaV at 4 but that is way too low otherwise like I said above the charge stops around about 30% in
In the event that the instructions have been auto-translated and printed without being proof-read, I would go he empirical way.  Trickle charge a pack until you are sure that it is full, measure the voltage, set the smart charger's Delta to that.  It should duplicate the performance ever after if it remembers details like that, otherwise "external memory" is needed.  Write it on a piece of paper and sellotape it to a suitable surcface.
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Richard Houston

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Re: 7.2V 2000mah 6S AA NiMh Pack - On Smart Charger
« Reply #5 on: June 11, 2019, 05:13:59 PM »

So no takers on the DeltaV setting for a 2000mah 7.2v 6S NIMH pack

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DaveM

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Re: 7.2V 2000mah 6S AA NiMh Pack - On Smart Charger
« Reply #6 on: June 11, 2019, 05:34:00 PM »

9.0v absolute maximum.

Don't charge at less than about C/3 which, in your case, is 650mA. NiMH cells don't like slow charging; I'd suggest 1.5A as a norm.

DaveM
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Richard Houston

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Re: 7.2V 2000mah 6S AA NiMh Pack - On Smart Charger
« Reply #7 on: June 11, 2019, 05:40:49 PM »

9.0v absolute maximum.

Don't charge at less than about C/3 which, in your case, is 650mA. NiMH cells don't like slow charging; I'd suggest 1.5A as a norm.

DaveM


Nice answer but this is not the DeltaV thats the charging voltage your talking about
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DaveM

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Re: 7.2V 2000mah 6S AA NiMh Pack - On Smart Charger
« Reply #8 on: June 11, 2019, 07:35:12 PM »

Then I'm truly sorry for having misunderstood your question - or at least misinterpreted the comments which followed. My understanding of Dv is the "dip" in the pack voltage which indicates to a smart charger that charging is complete (Delta being the conventional mathematical symbol for change), but I suspected from your subsequent comments that you actually meant the terminal voltage itself. The "charging voltage" is irrelevant.

Unlike NiCads, NiMH packs don't have a significant Dv. In fact some packs don't exhibit a detectible dip in voltage when they are fully charged, therefore to rely on it can result in a pack being overcharged - with significant damage.

I hold to my reply about the terminal pack voltage and charge rates. I'm sorry if I have wasted your time and I do so hope you receive a satisfactory answer from someone.

DM
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Richard Houston

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Re: 7.2V 2000mah 6S AA NiMh Pack - On Smart Charger
« Reply #9 on: June 30, 2019, 05:39:50 AM »

Tell me this does a Fully charged AA cell show as 1.55v because if they do then would'nt 6S in AA be while charging at 1.5A show fully charged when the output voltage hits 9.3v on the charger ??


these are brand new NiMh 6S pack 7.2v and I want them fully charged but not over charged
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malcolmfrary

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Re: 7.2V 2000mah 6S AA NiMh Pack - On Smart Charger
« Reply #10 on: June 30, 2019, 08:19:49 AM »

Any NiMH cell showing more than 1.5 volts can be considered overcharged.  If the charger is connected, its probably the charger voltage being measured.
Useful info here - http://www.greenbatteries.com/nimh-battery-faq/
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