Looking for 24V NiMh 10Ah charger

[chazpope]

I have made a new 10AH NiMh battery but none of my two chargers would charge it - perhaps it responds differently and the chargers just would not start the charging cycle.

I would like to buy and try another one say that does something like 3A - but can't seem to find one. All I found on ebay was for Lead acid or Lithium battery or the type was not specified and when I asked does it work for NiMh I got a negative answer

Any ideas ?

In another thread I am looking for an answer why my chargers would not charge the new battery (it did once but now just flashes green and red) - but that has not produced any result so far. I guess I could try building a charger - but I would rather buy one

 

[shemozzle999]

I have just read your previous thread.

Is this your charger?

32V 1.8A charger for 24V Ni-Mh battery, Products, Ni-Mh/Ni-Cd Charger, Battery Charger Manufacturer,smart charger

If both lights are flashing you have a battery fault as has been suggested in your previous thread, see datasheet for details:

http://www.abt-power.com/upfile/201108/20110821093812C8U0sO.pdf

I would double check all the work you carried out to make the pack and if you cannot find any fault I suggest you contact them, they should be able to determine the problem if you give them all the facts stated above.

If you have access to a voltmeter check each cell if any are at the low level previously mentioned you will have to replace the bad cells for the pack to work.

 

[chazpope]

hi yes this is the charger I have - (though mine is from 2008) it flashes green and red and I already know it means 'error' the question is - what error.

This is a constant current charger and it should work even if you take out (say short) or even add another cell. There is something it does not like at start up and that's that - I know they go through some pulse to start. also this thermo couple I had came from another battery-charger combination but I thought it should not make a difference

I have tried chinese companies for support before and got a robot translation answers over and over again - but who knows this one may be different.

 

[shemozzle999]

If you dont have the NTC (negative temperature coefficient) thermistor from the original battery pack connected to the original charger it will not work.
It should be placed in close proximity to the cells and wired into the DC connector as per the original battery pack, it detects the temperature of the cells when charging and reduces its resistance the hotter it gets.
When a certain temperature is reached it will automatically controls the charger to protect the battery pack.

This charger requires a 10KOhm Beta 3950K thermistor to work properly - information taken from the charger datasheet.

You can buy them but it looks like they are only available from the USA on ebay.

You could have over cooked the cells with a 14KOhm one.

 

[chazpope]

The original pack came with this charger HP1202N2

It charged the battery once for about 3-4 hours and died? before a full charge (green) was reached.

Now there is a possibility that the two packs (and chargers) had incompatible NTC thingies - one is '10K&B=3050' the other is 'IS103AT(10K)'

what do you think ?

 

[flecc]

The Semitec 103AT4 is R = 10k, B = 3435, so still well below the correct beta. eZee used to have this one in their NiMh battery.

 

[shemozzle999]

OK, a couple of questions,

1. With the HP charger plugged into the mains but not connected to the battey, carefully measure the voltage across the positive and negative pins on the DC connector with a multimeter set on the appropriate dc voltage range. From the link you just posted is says it should give a No load voltage: 36.5V~39V pulse.

2. Do you still have the original thermistor for this charger. If you do, can you measure the resistance across the 2 wire ends at room temperature (25C) it should read 10K Ohms.

 

[chazpope]

1. there is no voltage at all - as soon as switched on I hear the relay is clicking inside and nothing comes out - the red light blinks at 2Hz . As soon as connected to battery the light frecuency increases and it fades out. I tried connecting a 10K resistor between the - and ntc wires - it made no difference. I suspect this charger is faulty but it still shows some reflexes

2. yes it is installed inside the battery - but is shows 14K (not 10K) at room temperature! I wonder if this is the problem and makes it not charge

I guess I should try the working charger with 10k resistor but that is not as easy so will do it on the weekend.

 

[shemozzle999]

The hp charger may still be ok as the light is flashing.

Lets remove the battery out of the testing at this stage and concentrate on the charger alone.

While disconnected from the mains can you safely connect that 10k resistor directly across the - negative pin and the sensor pin of the charger output plug?

It could be done by sliding some heat shrink tubing over the pins and inserting the resistor lead into the tubing, heating the tubing should give you a temporary connection.

The resistor will simulate the thermistor and be seen by the charger.

If you can, plug the charger back into the mains. Do you now get a solid red light on the charger and can you repeat the dc voltage check across the positive and negative pins on the DC connector.

 

[chazpope]

Yes like I said just above I soldered a 10K resistor between ground and ntc wire - and tried it - no change.

There is no voltage - light is blinking, then I connect ground and red to battery and click-relay goes and light goes off, disconnect - blinks again. BTW this charger normally flashes when not connected and glows solid red when charging.

I repeated this test again, same result. Now the thermistor measures 13.7K (not 10K) but then this simply corresponds to a temp of 16C so the charge should still start I reckon

 

[shemozzle999]

Did you remove the thermistor out of the circuit before you connected the resistor?

If not they would be connected in parallel and the resultant resistance nearer 5K.

If you did then there are no more tests you can make to the charger and must assume it to be faulty.

I would still be inclined to put the resistor directly across the charger plug pins as it removes any existing wiring from the test.

I always fault find from the source to the load in easy steps until I find the fault.

 

[chazpope]

yes I soldered 10K resistor onto charger plug wires and then connected the charger to the bottom of the battery (so that its thermistor does not play). I will try the other charger in a similar fashion over the weekend.

I think what is happening is that as soon as that charger starts its cycle it does some assessment of the battery behaviour (it can only be voltage at a certain current) and it decides that the battery is faulty.
and it has a different blinking mode (green/red as opposed to only red) to indicate that. I will try contacting the maker for more info.

I would also like to fix the broken HP charger but not sure if possible - a new one costs over 40 quid

 

[shemozzle999]

I wouldn't connect the other charger yet we still don't know if the battery cells are ok. It could render your second one unusable if you have not cleared the fault.

The charger socket located in the battery housing and its wiring would be my next step in my checklist.

Would I be right in thinking that the battery housing assembly is now quite old?

It might be worth removing it from the housing and reflowing all the wiring joints connected to the back of the socket and giving the socket holes a close inspection looking for tarnished connectors, they can be reburbished by cleaning their insides with a fine grade of abrasive paper.

 

[chazpope]

in the meantime I built a 1 amp dumb charger and charged the battery through the charging socket while monitoring current and thermistor resistance. that went from 18K cold to 6K when moderately warm after 10h of charging. The battery was charged and took me to work today with very little voltage drop - still to cycle home but looks like the battery itself is working ok. Now I won't recharge with this charger until empty cause it would not know when to stop - so I need to sort this out to use a proper charger that can top up from half empty

 

[shemozzle999]

Hi chazpope,

Glad you found a way of getting a charge into it.

So it looks like you need to replace the charger then.

ABT make a 2.8A version which has better charging indicators:

Ni-Mh battery charger manufacturer, Products, Ni-Mh/Ni-Cd Charger, Battery Charger Manufacturer,smart charger

It can be purchased for about $40 from:

Sell 24V/2.8A NIMH/NICD Battery Charger With fuel Gauge,Suit for:24V 3 20Ah NIMH/NICD With 20%~100% 4 LEDs battery fuel gauge-in Charger from Consumer Electronics on Aliexpress.com

 

[chazpope]

Thanks, This charger looks good but doesn't seem to have input for the thermo couple ?
so it will not take into account the T and dT/dt like the other chargers do.

I guess it will charge faster but I only charge overnight anyway so for me it does not matter.

I've been using the bike with my diy charger - no problem other than that it is inconvenient. I really want to get my Shenzen charger to charge this. I asked the chinese co that makes the other one for advice and got zilch, now I will try to as the Shenzen co what it means when it blinks red/green but I don't think I will get an answer.

 

[shemozzle999]

Yes it looks like it is a 2 wire output, you would have to transfer the plug from the old non-working charger, the unit is microprocessor driven:

http://www.abt-power.com/upfile/201109/20110919001146y1gWMj.pdf

Good luck with your inquiries - let us know how you get on.

For those who are looking for battery monitors I noticed they also make some custom parts:

Products, Battery Management System, Battery Charger Manufacturer,smart charger

 

[maarten]

hi to all,,
i have a problem to charge my new battery,

i build this 24v nimh 10 a to replace the old 24v nicd 5a,
therefore i purchased the 2,8 charger from ABT (Ni-Mh battery charger manufacturer, Products, Ni-Mh/Ni-Cd Charger, Battery Charger Manufacturer,smart charger )

now the problem is when i connect the charger to the empty battery, the charger starts charging and the indicator tells that the battery is then allready at 75% (empty) and after 10 minutes it stops charging and tells fully charged ,100% ,when i tried the battery on the bike it runs offcourse just 2 minutes,
i tried to charge several times, but no results,i put a volt and amp meter and got the following results when charging 28,5v (too low ?) and 2,8 amp
anyone any idea? ,, thanks