I have a 12 volt cordless trimmer in which the adapter used for recharging is lost. I have an adapter for a cordless drill which fits into the slot for the 12 volt trimmer, but the adapter and drill are powered by 9 volts. Will the 9 volt adapter recharge the 12 volt trimmer, or is there major damage forthcoming from even attempting this?
There’s a lot more than simply matching voltage. Polarity is another very important factor. Although the 9 V adaptor may work if the polarity is correct, you need to be sure that is the case. If the trimmer regulates the 12 V down to 1.5 or 3 V or thereabouts, it might be ok. Be absolutely certain that the polarity is correct or you WILL destroy your batteries and possibly the trimmer too!.
Really the very best thing to do is to obtain a replacement supply from the manufacturer.
No, it won’t charge the higher voltage battery.
Is this a serious question?
Peace,
mangeorge
Well, the simplicity of the idea is shot. Thanks for the advice, I’ll look for a replacement.
You also stand a good chance of destroying the AC adapter and possibly causing a fire.
You have to match the voltage exactly, have at least as much current supplying capability, and as was mentioned, also match up the polarity and the plug on the end.
Or you could take a lesson from Homer Simpson and go to your neighbor and tell him that since he no longer has a trimmer, he doesn’t need that old adaptor/charger in his garage.
Bravic, it seems you do not know enough about the subject so the answer is to buy a replacement which is guaranteed to work and don’t play with things you don’t understand well. Having said that, the scare warnings in the previous posts are somewhat overexagerated so I will explain for the technically knowledgeable.
I have quite a bit of experience with these simple chargers and power supplies which consist of a transformer, rectifier and sometimes capacitor. The polarity warnings are valid but it is quite simple to chack for the correct polarity. In these units which are not regulated the voltage varies quite a bit from no load to full load and the only way to know what you have is to actually measure the characteristics of the unit. In my experience most units output more voltage than their nominal value at their rated amps and they all output more voltage at lower amps. The nominal output voltage is only an indication and the only way to know what you have is to measure but to measure correctly you need am oscilloscope as a voltmeter will read average values only. In my experience the peak output of the transformer (and the no-load output voltage if there is a capacitor) is between 1.4 and 2.0 times the nominal output voltage. Due to the resistance of the transformer winding (designed that way) this voltage drops quite fast with load and at nominal output should be equal to the nominal output voltage but, more often than not, is higher. For example, my cell phone battery is 3.6 volts. The charger says 3.6 volts but with no load outputs 10 volts. When it is connected to the battery it outputs about 250 mA so the equivalent circuit is a 10 volt ideal power supply with a 25 ohm internal resistance. This will withstand shortcircuit for short periods without overheating and will charge batteries of higher than 3.6 volts (but will charge them at a slwer rate). Also, if connected to a batteryhigher than about 9 volts, nothing will happen. It will not charge it but no damage will occur to charger or battery.
Taking the preceding into account I can say that, provided you get the polarity right, you can quite safely connect the 9 volt charger to the 12 volt battery and chances are that it will recharge it but will take longer. At this rate the charger is working under less load and so will heat less than when connected to a 9 volt battery. In any case, the only way to know what is actually happening is to measure it.
Another important issue when dealing with electronic appliances is voltage ripple. Batteries don’t care too much about ripple but an audio amplifier or other electronic circuits can have probolems with ripple. Again, testing with a scope is the only sure way to know.