18 volt drill power supply.

[artstv1]

I have an 18 volt drill battery charger and the transformer is open, I only have a 24 volt transformer to replace it with, Will that work with out overloading the regulator .

[stj]

Re: 18 volt drill power supply.

what is the regulator and smoothing capacitor?
pictures.

[budm]

Re: 18 volt drill power supply.

Pictures of what we are dealing with will help.

[999999999]

Re: 18 volt drill power supply.

First, it's entirely possible that the transformer's thermal fuse has blown but only due to a temporary condition. Put the transformer on a heat resistant (fire-proof) surface, put a new thermal fuse on, and test for overheating. Using it in a hot area, bits of drilled material or dust clogging inadequate vent slots in the charger casing, it happens... clean it up and drill some more vent holes if the transformer seems okay with a new fuse.

However, an 18V drill doesn't necessarily have an 18V transformer. 18V is just the nominal voltage of either 15 NiCd or NiMH cells in series, or 5 Li-Ion cells in series. The actual voltage the pack attains at full charge is closer to 21V.

Plus, transformers are typically rated for AC voltage, so if you have one rated for 24VAC, after bridge rectification it could be as high as 32V. Right off the bat you're going to want to check the smoothing capacitor to see if it's even rated that high, and get the part # marketing off the regulator and/or charger IC, assuming it has one (exact make and model drill and charger might help) and consult their datasheet(s) to see what voltage range they can accept, and how they work might be demonstrated by one or more example circuits.

Look at the example circuits and see if what's in the charger seems roughly if not exactly the same to some extent. You'd be looking at what the max voltage ratings are for any components that see the max voltage, or the heatsinking for any that drop voltage.

Now that I've written this much, I realize I'm probably wasting my time since the topic was started over 10 days ago and two prompt replies but nothing more from the original poster.

Anyway, if it's a dumb (trickle) charger then transformer voltage being right is VERY important. If it's a rapid charger then the transformer is capable of higher current and assuming you want the replacement transformer to fit in the charger casing good, going with a higher voltage than the original will tend to either be larger or lower current. Both "might" be worked around, or either might be a problem.

We're all about repairing things but have you considered picking up a used charger on an auction site or locally oriented sites like Craigslist or garage sales, pawn shops, etc?

Anyway, first thing to do is the first thing I mentioned. Get a multimeter, take the HV (AC) transformer wrapper off, cutting it if you can't peel it from the end, and measure whether the thermal fuse is open or conducting, a continuity or resistance measurement. There should be markings on it telling the model # for cross reference or the trip point temperature.

Do not use a replacement with much higher trip point temperature and rated for at least as much current, though the current on that transformer winding is going to be quite low. It's likely that most commonly available thermal fuses are capable of that much current.