Topsy is a hybrid loco. He/she has the main drive from a large fork lift motor which has its batteries topped up from a 24v alternator driven off a small petrol engine. The petrol engine will not take the load on the alternator if the motor is pulling full amps (96A and 24v!) so I need to find a way of reducing the current in the alternator. There are two options, option one is to leave the petrol engine / alternator running all the time and reduce the field current in the alternator to reduce maximum current drawn. Option 2 is to switch the load away from the battery (e.g. to a lamp) the moment the electronic controller is opened. There are pros and cons to both. In the former, the electronic speed controller has regenerative braking, so the battery volts may rise to 36v on braking. How will this affect the alternator? Will I need any additional protection (e.g. an diode on the supply side to prevent and reverse feeding?) The second option (switch it off when under load) is the easiest, but many opportunities are lost for recharging the batteries when driving the locomotive around the circuit. Your thoughts please. Cheers Peter MODEL ENGINEERING DISCUSSION LIST. To UNSUBSCRIBE from this list, send a blank email to, modeleng-request@xxxxxxxxxxxxx with the word "unsubscribe" in the subject line.