Help! Old panasonic lafree charger failed??

[Natty Jones]

Hi, Long story short, i am an electrician who thought he could replace the 1.2v cells in my mums old giant lafree ebike battery to save her some money. as it was no longer holding charge. i did that job and was happy enough with the results and thought it was job well done however battery doesn't seem to charge, the panasonic NKJ019 recognises the battery and says its charging however it says charge complete before battery is actually fully charged. i took the pack back apart and moved the temperature probe as i believed this was the issue but the same thing happens even with probe sticking out of pack at room temp... which makes me think the charger is at fault? i have seen a person Flecc on here seems to have a good knowledge of this bike / charger and was after some advice really. i have plunged a bit of money in to all the new cells and don't really want to waste more money but also feel i have spent too much to give up now. If a new charger is required and will fix it then that's what i will do... If you have a suggestion of a replacement charger as i am struggling to find much that will charge the 20s cells. most only seem to go to 15s? Please help.

 

[Natty Jones]

Hi, Long story short, i am an electrician who thought he could replace the 1.2v cells in my mums old giant lafree ebike battery to save her some money. as it was no longer holding charge. i did that job and was happy enough with the results and thought it was job well done however battery doesn't seem to charge, the panasonic NKJ019 recognises the battery and says its charging however it says charge complete before battery is actually fully charged. i took the pack back apart and moved the temperature probe as i believed this was the issue but the same thing happens even with probe sticking out of pack at room temp... which makes me think the charger is at fault? i have seen a person Flecc on here seems to have a good knowledge of this bike / charger and was after some advice really. i have plunged a bit of money in to all the new cells and don't really want to waste more money but also feel i have spent too much to give up now. If a new charger is required and will fix it then that's what i will do... If you have a suggestion of a replacement charger as i am struggling to find much that will charge the 20s cells. most only seem to go to 15s? Please help.

Development! I used the chargers refresh function and battery has now charged to 4 bars!! (this may well actually be full as i was unable to use the existing tab that the meter was connected to, so i know this affects the readings) i obviously can't use the refresh function every time but this does at least prove the battery can be charged, and also the charger can still charge it... so don't really know where that leaves me.

 

[cyclebuddy]

I don't know anything about your bike or it's battery, but the principles remain the same for most. Others here may chime in if you share more details.

A good first step is to say what end voltage the battery is charging to/ what it should be (you're expecting it to be), and what the output voltage of the charger actually is, again against what it's rated to be.

 

[flecc]

Hi, Long story short, i am an electrician who thought he could replace the 1.2v cells in my mums old giant lafree ebike battery to save her some money. as it was no longer holding charge. i did that job and was happy enough with the results and thought it was job well done however battery doesn't seem to charge, the panasonic NKJ019 recognises the battery and says its charging however it says charge complete before battery is actually fully charged. i took the pack back apart and moved the temperature probe as i believed this was the issue but the same thing happens even with probe sticking out of pack at room temp... which makes me think the charger is at fault? i have seen a person Flecc on here seems to have a good knowledge of this bike / charger and was after some advice really. i have plunged a bit of money in to all the new cells and don't really want to waste more money but also feel i have spent too much to give up now. If a new charger is required and will fix it then that's what i will do... If you have a suggestion of a replacement charger as i am struggling to find much that will charge the 20s cells. most only seem to go to 15s? Please help.

These chargers were notoriously unreliable, Panasonic tried twice to get them right but at one point used a Taiwan company to supply them a special, no longer available.

The problem extended to recelling, not charging afterwards being very common, so much so that some recellers refused to touch them. The replacement charger I and others successfully used came from the USA so not particularly cheap, but fortunately it is still available.

This is a web link to the exact charger

These old web pages of mine are still online for you to use:

Charger

Connector

Meanwhile though, try to get it working before spending. You can try a 10k resistor in place of the NTC thermistor for example which might get the old charger to kick into action normally.

Also the built in LED metering often doesn't work well after recelling, sometimes not at all, so don't take any notice of what it says, 4 LEDs rather than 5 may well be fully charged, which should be 29.4 volts.

This advice from Powerstream may be helpful too:

Important note: Due to the erratic charge behavior of NiMH and NiCad batteries when first placed on charge there is a delay of up to 15 minutes before an accurate charge termination can be read. In worst case a battery can be taken off the charger and reattached, and charged for 15 minutes before the "charged" light comes on again. In addition, new packs should be charged and discharged several times before they "settle in" to a predictable charging condition.
.

 

[Natty Jones]

These chargers were notoriously unreliable, Panasonic tried twice to get them right but at one point used a Taiwan company to supply them a special, no longer available.

The problem extended to recelling, not charging afterwards being very common, so much so that some recellers refused to touch them. The replacement charger I and others successfully used came from the USA so not particularly cheap, but fortunately it is still available.

This is a web link to the exact charger

These old web pages of mine are still online for you to use:

Charger

Connector

Meanwhile though, try to get it working before spending. You can try a 10k resistor in place of the NTC thermistor for example which might get the old charger to kick into action normally.

Also the built in LED metering often doesn't work well after recelling, sometimes not at all, so don't take any notice of what it says, 4 LEDs rather than 5 may well be fully charged, which should be 29.4 volts.

This advice from Powerstream may be helpful too:

Important note: Due to the erratic charge behavior of NiMH and NiCad batteries when first placed on charge there is a delay of up to 15 minutes before an accurate charge termination can be read. In worst case a battery can be taken off the charger and reattached, and charged for 15 minutes before the "charged" light comes on again. In addition, new packs should be charged and discharged several times before they "settle in" to a predictable charging condition.
.

Thanks Flecc,
I knew you were the person to ask!
I tested battery last night and it was approx 27v so not actually quite full. I ran the battery down a bit last night myself with a 12km ride, will try and run it down to empty this weekend then try and re-charge it again, im hoping the "Charged and discharged several times before they "settle in" to a predictable charging condition" is at play here, and will hopefully get a full charge this time. Failing that i have got my hands on a 10k resister to try. I'm really hoping i don't need a new charger because they are £80+delivery+import... .

 

[flecc]

I'm really hoping i don't need a new charger because they are £80+delivery+import... .

Indeed, they are too expensive. Not as bad as Panasonic's replacement in 2007, a whopping £125 some 16 years ago.
.