Hello guys,
I want to charge my 9v 300mah ni-mh battery, One of my friend told me that it is very simple, and given below circuit. its working but not properly.......
I charged it for almost 5 hr concidering that is it fully charged.... removed charging and then checked the battery vltg, it was showing 9.5v .......Then i connect 300 ohm 5w resistor to it..... theoretically it should discharge in 10 hrs but in just 3.5 hrs it was showing 2v on my voltmeter........
so what is wrong with it...Am i done charging the way it should be?????????????
I am confused.......... 
See image below.............
Hoping someone here can help me
Am i charging it correctly??????
i also implemented the circuit given on Intelligent NiCd/NiMH Battery Charger with somewhat changes but it's suddenly showing 9v across battery... so how would i know the battery is charged or not????
First question - how did you come to the conclusion that your question should go in the "Website and Forum" section of the Arduino Forum?
Second question - why did you think of asking a battery question on a Forum about Arduino programming ?
Suggestion - have a look at the Battery University website
...R
Hello Robin2 thnx for replying ......
I m gonna use arduino for controlling the charging circuit........(i.e when charging is completed,auto stopping battery charging). thats why, once i'ii get this battery charging technique so i can use arduino ..........
(Robin2....I am new in arduino forum(Last week created accnt). So when i seen 'New Topic' option, i posted my question...If you think this is not the place for such qstns then please suggest me the right place)
Thank you........
Is this a 6-, 7-, or 8-cell 9volt battery.
Only an 8-cell 9volt battery might survive this "dumb charger".
If ONE single internal cell drops below ~1volt, you can kiss the battery goodbye.
Discharging to 2volt surely has reversed at least one cell.
Leo..
Hello wawa,
it is a single 9v battery which i am gonna charge................. do you know any circuit that i can use..........i am confused just because of two things
- Bttry voltage rises vary instantly to 9v as i connect it to this circuit............
- Now lets concider that bttry is fully charged now......Now according to calculations if i connect 300ohm, 5w load to it then as battery is 300maH,9v it should discharged in 10 hrs, but in just 2-3 hrs it shows 2v on mutimeter(load connected to bttry while measuring)............
i tried some lm317 circuits but its not working..........
If... this is a 6-cell battery (guessing, because of the 6 in the serial number), then it's a 7.2volt (nominal) battery.
Your "dumb charger", if... the 12volt is exact and regulated, will pump ~25-30mA in the battery when charging.
Charging (from flat) will take 14-16 hours, not five.
You can discharge a 6-cell battery to 6volt.
If... you have discharged the battery to 2volt, it's toast.
It will still sort of work, with limited capacity and high internal resistance, and self-drain quickly.
NiMh batteries need a dedicated intelligent charger with delta-V detection.
And over-discharge protection.
Otherwise they won't live long.
Leo..
Hmmm...K...
i have seen this article http://electronics-diy.com/electronic_schematic.php?id=813
Given that bttry vltg will reach to desired vltg when fully charge.......and my bttry vltg is 9v showing already..
(Now your may have doubt that my battry might have fully charged and why i am charging it again and wasting time......)
OK lets forget everything.......How to check whthr battery is fully charged or not(Means my method to connect load of 300ohm is correct or not) ??
I am discharging it using two 1 ohm 5w resistors parrallel across it(For faster discharging and testing)..........
You posted a picture of a low current (charge and discharge) smoke alarm battery.
You can't charge that with a 1.25A charger, or discharge it with a 0.5ohm resistor without breaking things.
Leo..
So can you suggest any circuit link that will work..........????
Since you are new, might I suggest that you also remember that the audience here is international and many do not speak English as a first language. Your "telephone" message speak is definitely not going to help you much here if you continue to "type lazy", such as "bttry vltg ".
If you must abbreviate, use common abbreviations versus making up your own. Even saying "Vbat" is a better (more common) abbreviation than the ones you have been using.
The only reliable/cheap charger for NIMH is a Current/10 constant current charge rate and even then, it won't guarantee you won't hurt the battery... you are just taking the lowest risk. So I agree that it would take 10-15 hours to charge your dead battery if using this charge rate. If using faster rate, you MUST follow fast charge algorithms or your battery is toast pretty fast.
You want to find a good site about battery charging... and then try to understand the differences between slow (safe) charge, fast charge, fastest charge and trickle charge.
If you are going to make your own arduino controlled charger... understand the goals lists here (from a battery charger website). If any of these are unclear, then this is where you need to fill in the gaps in your knowledge.
-
Soft start. If the temperature is above 40 degrees C or below zero degrees C start with a C/10 charge. If the discharged battery voltage is less than 1.0 Volts/cell start with a C/10 charge. If the discharged battery voltage is above 1.29 V/cell start with a C/10 charge.
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Option: if the discharged battery voltage is above 1.0 Volts/cell, discharge the battery to 1.0 V/cell then proceed to rapid charge.
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Rapid charge at 1 C until the temperature reaches 45 degrees C, or the dT/dt indicates full charge.
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After terminating the fast charge, slow charge at C/10 for 4 hours to ensure a full charge.
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If the voltage climbs to 1.78 V/cell without otherwise terminating, terminate.
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If the time on fast charge exceeds 1.5 hours without otherwise terminating, terminate the fast charge.
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If the battery never reaches a condition where the fast charge starts time out the slow charge after 15 hours.
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Fuel gauge, communication to the device being powered, LED indicators all possible. (There are fuel gauge IC's. See Texas Instruments, for example)
Letting it discharge to 2V will likely have damaged it further. You cannot allow rechargable batteries
to flatten like that without much compromise to their longevity and capacity.
Rechargable batteries of all sorts need to be protected from over-charge, over-discharge, over-current...
If you expect the initial capacity to last the battery's lifetime you are going to be disappointed - substantial
decrease in capacity happens over the lifetime, perhaps to 50% of original capacity even if the battery
is treated carefully and not subject to any abuses. Indeed the lifetime of a battery is usually determined
by the drop in capacity
Lead acid batteries are even more fussy and must be stored fully charged and topped up regularly, or the
capacity is permanently lost due to sulfation of the electrodes.
Any rechargeable battery type needs immediate recharging when its capacity is exhausted (for instance
your battery should have been put back on recharge by the time it got to 7V or so)
I agree all these thing theoretically guys.........Thanks for helping.
Can you suggest any circuit that will work fine???
One question didn't gone from mind that how to check my given battery is fully charged or not????
pwillard:
if you continue to "type lazy", such as "bttry vltg ".
Ok pwillard.... i will not do any this kind of mistakes keeping in mind that audience here is international