12v Charging

[Colinkilner]

I wondered if anyone can advise. Have a wonderful Watermota engine set up which whilst has its pitfalls is giving good reliable service. I have two battery banks one 24v to start engine etc the other 12v which powers those essentials we have these days. Have relied on charging the 12v bank from a charger which comes on when plugged into shore power and a 24v/12v reducer. However we have now added a fridge unit and so wondered if we were able to take a tapping from the 24v alternator output. reduce it and charge the 12 v bank ??? Or am I dreaming ? Wanted to stay away from wind generators and large solar panels but ? Any opinions ? Thanks.

 

[rogersimms]

I bought this little gadget from Adverc that when my 24 volt bank is being charged from what ever source it will then charge my one twelve volt battery. I believe it was for lorry drivers who carry a 12 volt battery for tv's etc and need to charge it from their 24 volt system. I dont know how big a battery bank it will charge but they are worth a call

 

[VicS]

Sterling do a 24volt to 12volt 30amp charger. BB241230 not cheap though!

 

[William_H]

The 24 to 12v reducer or converter is the way to go. This switches the 24v at high speed and then uses a transformer to convert down to 12v. They are fairly efficient at about 85% so you can get far more current out at12v than you put in at 24v. Same power less inefficiencies. It sounds like you have one already. It should state the current o/p capacity which hopefully will service the 12v fridge.The converter should give a regulated 13.75 to 14v which should be good enough to keep the 12v battery charged though they are designed to be used without a battery simply as a 12v supply. If it has enough current capability get rid of the 12v battery.

I would suggest a voltage sensing relay to switch the fridge on when engine is charging at 24v (28V) and off when not charging to save batteries. If you keep the 12v battery you need VSR to sense 24v but be able to switch both the 12v and 24v. Or fit another relay off the engine electrics circuit to switch fridge supply.

I hope this makes sense olewill

 

[Colinkilner]

Thanks for all your comments chaps. Sounds as if the best/cheapest thing to do is to rig my 24v -12v reducer rated at 4A from the 24v bank to the 12v one and either switch it on manually or find a way of it turning itself on when the engine is going as I guess if it on all of the time it could worst case drain the pants out of the 24v engine starting bank ??