Ryobi 4v cordless drill not charging

[spike47]

Hi
Sorry not been into electronics for quite awhile so a bit slow !.
Have a Ryobi 4v cordless drill, problem not charging, voltage at input 6.2v, voltage to battery 2.28v !, what do I have to check in between ?.

cheers
Spike

 

[Diver300]

My guess would be U1/ Q1

I suggest you trace out the circuit.

It is also possible that the charge rate is very low because the battery is so low, and that leaving it on charge will get some charge into the battery, at which point it will charge faster.

 

[spike47]

Hi
Tks for that
Spike

 

[rjenkinsgb]

If it's a lithium cell and the voltage on it has been below around 3V for more than a brief time, it may be developing internal shorts and will not then recharge.

The charge controller IC will only pass a very small current to test the cell, until it reaches its normal working range, as Diver mentions.

Trying to fast charge or force charge one that has started to fail can make it overheat or burst, hence the low current testing stage.

 

[spike47]

Hi
Can anyone id these 2 chips , U1 and Q1 on this board.

cheers

 

[Diver300]

It's really hard to identify semiconductors from the marking.

If it is the charging that has gone wrong, it can be easier to find a suitable circuit board on eBay or Aliexpress and fit that inside the appliance. You need to find something that can take the input voltage you need and charges the right number and chemistry of the batteries you are using. Then it's probably only a matter of connecting input, output and ground.

I did that with a cordless bluetooth speaker, which is still working a couple of years later.

 

[spike47]

hi
Tks for that, it just seems a simple repair to change these 2 components !.

cheers

 

[Diver300]

hi
Tks for that, it just seems a simple repair to change these 2 components !.

cheers

It would be, if you could identify and obtain them. Unfortunately, neither is easy.

 

[spike47]

It would be, if you could identify and obtain them. Unfortunately, neither is easy.

Yeh, but it is not really a very old drill !

 

[Diver300]

Yeh, but it is not really a very old drill !

Older ones might be easier to find the components for.

 

[spike47]

Older ones might be easier to find the components for.

Yeh I guess so.
cheers

 

[rjenkinsgb]

Have you tried a different battery? What is the battery voltage?

If the existing one is a lithium type that's been left flat, it may never charge again, by design.
The charge circuit could work fine with a new battery.

It looks like it may be an 18650?

 

[spike47]

Have done a schematic up to the motor, well have tried to, prob some mistakes in the drawing !., have it in Eagle format or .pdfwill attach both . cheers

ps: It won't let me upload the Eagle one !
Spike

 

[spike47]

here is the .pdf one

 

[spike47]

Here is the Eagle one !

 

[Nigel Goodwin]

As has already been mentioned, the battery is ruined - it's far too flat to allow charging. Probably because the charging 'circuit' is absolutely abysmal, and there's no protection for the battery. Once the battery has discharged too much, then it's ruined - instead of messing about with the charger, try hanging a good 18650 in place of the original battery, and see what happens.

 

[spike47]

Hi
Thanks for that, have 2 spare battery's of that size, will try tonight when back from work.

cheers
Spike

 

[spike47]

Will report back with results

 

[rjenkinsgb]

Thanks for that, have 2 spare battery's of that size, will try tonight when back from work.

If the spare batteries read at much less than around 3.3V, they are likely already wrecked and will probably also not work.

 

[spike47]

If the spare batteries read at much less than around 3.3V, they are likely already wrecked and will probably also not work.

hi
Have tried a spare batt, was showing 3.95v, but still the same.
I just did a quick test from neg lead onto board and first pin on D1 and getting 7.7v then tested the other side of D1 , no voltage !, is that supposed to be, just fit a new diode to D1 !.

cheers