I have done this with a LED monitor
and other appliances
. It saves power and is easier and neater than running the inverter
The only problem is that you are running the tv on up to 14.5v or so with the charging
sources on. Most appliances
will cope with this higher voltage without any problems, but not all.
In the end you have to take a chance. One usefull test you can do is measure the existing transformer voltage. If the appliance has an unregulated transformer it will measure about 15v dc. With this type a transformer once the load current
is applied the voltage will drop to 12v, but at least you know the appliance will accept an instantaneous higher voltage. Appliance with this type of transformer are more likely to tolerate the higher voltage from a boat
The second type of transformer is a regulated one. This will measure 12v with a multimeter and will maintain that voltage. The risk of running an appliance with this type of transformer on the boat battery
A simple trick is put a diode in series. This will drop the voltage by about 0.6v and moves it into the better range. Low voltage is generally safer, but with with flattish batteries
or other high loads the appliance could be running on on only 11v. The diode is generally safer, but I would not use it if you poor wiring
(with voltage drop already incorporated), or if running high loads like microwave at the same time as using the appliance. So a diode is a good idea, but there are no guarantees.
you can incorporate a regulation circuit, but the simple ones drop some voltage which means you can have too little volts when not charging
. More complex circuits can maintain a constant 12v, but the power savings are less and most people would simply use an inverter
if this is required.
Running directly from 12v is generally OK, but be aware you are taking a risk. I will only do it with an appliance that is cheap
enough to replace without too many regrets. A diode is safer, particulary if the transformer is regulated, without it try not to run the appliance when the battery
voltage is high.