Hilti Battery charger issue

Steve2381

Senior Member
Hey all
My 22v Hilti battery charger has died, and they want epic money for a new one :mad:

I tested it last night, and it has 20+v going to the battery on 2 terminals, but there are 3x other terminals returning from the battery (I tried 3 different batteries) and I don't know what these are.
I assume one might be temp?
Its not charging the battery, so the other connections must affect that.

The charger shows no signs of life. The led does not illuminate at all (its usually on in some state or another), and the fuseable parts of the charger seem to be fine. I have traced AC power as far as I could... so not sure how to proceed with checking further.

Any assistance gratfully received!
 

Steve2381

Senior Member
OK. An hour spent tracing the basics of the circuit out, and its dead. Also FAR too complicated to consider a repair.
The 22v at the pcb terminals is the backfeed from the battery (yes... I am that stupid). Traced the mains side psu through the rectifier and that seems fine, so its something to do with the madly complicated sensing circuit I think.

Bin time
 

Janne

Senior Member
If you post pictures of the unit, chances are some of us armchair electronic engineers can give out suggestions. It's quite possible, that the problem is something simple like a blown switch mode controller IC.
 

Steve2381

Senior Member
Incoming power is fine as far as the output of the bridge rectifier diodes.... that is about as far as I know how to trace it.
Incoming and 6.3A battery fuse are fine.

I think this is too complicated for a fix
 

eclectic

Moderator
Just MY opinion, but....

How much IS a new charger, with warranty? £80 ish?

How much is your time worth? .......

e
 

fernando_g

Senior Member
A hard-epoxy covered hybrid circuit (HC101), and no obvious damage (burnt out or exploded components, no dark-brown board areas)....
I'm with Eclectic, you might have to bite the bullet and purchase a new one.
 

Janne

Senior Member
I think It's quite unlikely that the hybrid circuit would be at fault here. Since your charger seems completely dead, I would guess the most likely cause of failure are those big startup/control supply resistors on the primary side. Or the switch mode controller IC itself. When the primary resistors burn open they don't always leavy any visible signs on them in my experience.
But of course there are at least a dozed of other possibilities to cause the problem, and if you're never worked with SMPS's you could be in for a steep learning curve.
Spending time to figure it out and attempt a repair is not likely to be profitable, but everyone needs a good tinkering project every now and then :)
 

fernando_g

Senior Member
".....everyone needs a good tinkering project every now and then."

Well, from that point of view, and if you have time to spare, I would suggest the following, which can be accomplished with only a DMM:

-Check every resistor, power and SMT devices. Fortunately the SMT ones are large enough to have a printed legend. The larger power ones could be "fail-safe" devices, which open like a fuse before leaving burn marks.
-Check all capacitors for shorts. Ceramic chip caps if the board has been mechanically stressed, will fail into a low impedance. Google capacitor flex crack.
-Check the diodes, and to some extent the transistors.

Good luck!
 

techElder

Well-known member
Not to be left out on the everyone has one bandwagon ...

After having spent a lifetime in the "repair" business, I have found that more than 50% of the time the problem will be mechanical in nature. e.g. loose contacts, overheated pcb traces and cold soldered connections, etc.

Use a plastic probe and methodically poke/prod your way around the live board until something happens.

You have nothing to lose at this point.
 

Steve2381

Senior Member
It nothing obvious. No loose connections. No dry joints.
Its simply annoying. I don't like Hilti equipment, as I have had a lot of problems with them. However, without a charger the tools are useless and they have a few years in them yet.
Just grinds that I have to waste a further £80 on a charger for tools that when dead, I won't replace.
 

inglewoodpete

Senior Member
Why not roll your own charger?
NOT a good idea.

Most battery-powered tools now have lithium batteries which will often explode when over charged. It's not something to be taken lightly.

The reason that the Hilti charger costs GBP80 is that they were probably designed, if not also manufactured, in the western hemisphere to western safety standards with western labour rates. They are made that way so that the tools and batteries can be mistreated safely by tradesmen.

A 5 watt resistor will not cut it.
 

tmfkam

Senior Member
This Hilti charger is complicated for a reason
The reason that the Hilti charger costs GBP80 is that they were probably designed, if not also manufactured, in the western hemisphere to western safety standards with western labour rates. They are made that way so that the tools and batteries can be mistreated safely by tradesmen.
The reason for the complication and expense is that the Hilti charger is built to charge the battery at a super fast rate, minimising the down time to the user, and maximising the longevity of the battery pack.

Charging using a very simple charger as I suggest will not be fast. At a 125mA charge, an 8Ah battery would take ~64h to charge. If working on a site with a flat battery, you might not want to wait this long before drilling your next hole.

If you don't want to spend £80 and the original can't be repaired, my suggested charger might allow the tools to continue to be used until the batteries no longer accept charge and then it would be time to throw both the tools and the batteries out.

If you don't want to risk my suggested charger, it might be time to get your £80 ready.
 

srnet

Senior Member
In my opinion, a 5W resistor would 'cut it'. I did also suggest that the resistor values should be altered to suit the battery voltage and capacity as required.
I would not want to try it, and I would recommend no-one else does either.

If these are indeed Lithium cells; as you continue to put charge in the cell voltage will continue to rise, Lithium cells do not self limit on voltage.

So assuming the 22v is 6 Lithium cells, by my calculation the cell voltage could rise to circa 5.6V per cell.

The very important and key safety factor for Lithium chargers is that the have a voltage limit, 4.1v (per cell) for Lithium Ion, 4.2V for Lithium Polymer. Let them go much above that and you have a bomb, been there and seen it happen.
 
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Actionman

New member
Hi, I am a bit late to the party but this might help anyone with this problem.
I bought a cheap Hilti drill with a dead charger. Opening the charger and carefully checking the board I could not find any fault.
Almost ready to give up I looked again and found one of the leads for L3 was adrift and whole inductor had broken free of the glue holding it.
Did the repair and is now working fine.
 

Attachments

Actionman

New member
Not to be left out on the everyone has one bandwagon ...

After having spent a lifetime in the "repair" business, I have found that more than 50% of the time the problem will be mechanical in nature. e.g. loose contacts, overheated pcb traces and cold soldered connections, etc.

Use a plastic probe and methodically poke/prod your way around the live board until something happens.

You have nothing to lose at this point.
Thanks techElder, your post prompted me to keep going. The charger was just about to hit the bin!!
 

johnlong

Senior Member
Hi
Are your batteries totally flat I ask this because I have over the years alot of
problems with makita li ion batteries due to the way the batteries monitor connected
to one cell if that cell falls below a certain level the control board will not allow the charger to
charge the battery. Can you get hold of another hilti battery too see if that will charge if its a good
known battery it the charger if it does it the batteries. The makers do specifiy not too total drain
the batteries before recharge 20% left is what the chappy at makita told me
do a non branded replacement charger for £65 as aposs to the £240 for a hilti
 

Actionman

New member
Hi
Are your batteries totally flat I ask this because I have over the years alot of
problems with makita li ion batteries
The battery is fine. It was the charger that was faulty with a broken wire and loose component.
I have repaired the fault and the battery charges correctly now.
 
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