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Well I was getting sick of just not having enough oomph from my alternator to power everything I needed in a true go anywhere Bus so I finally decided to do something about it. If you plan to add a lot of electrical load to your Bus read my story. The first step is to work out how much power you think you'll need from the alternator when everything is "turned-on". If your running a VW engined Bus it ain't too bad unless you stick on heaps of lighting and additional electric heating and that sorta stuff. The standard alternator puts out 55amps. The problem I had was the electric fan for the radiator and the fact that I wanted a dual battery setup so I could listen to some tunes while I was just sitting there and so I could keep the beer fridge running and the interior lighting on as well. The radiator fan was drawing 20amps the stereo was fused for 10amps and was only going to get bigger!! Along with all the lights I was drawing about 50-55amps so the warning light would come on when I was stopped at traffic light with the headlights on, foot on the brake and indicator going. So step one was to upgrade the alternator from the measly 40amp one to a more impressive 80amp alternator. This fixed the warning light problem straight away. Step 2 was to do something about the everything-relying-on-one-battery problem. I bought a dual battery management kit from an electronics store that was designed to be mounted under the bonnet of 4WD's. It came with a waterproof Diecast Aluminium box and everything had to be soldered together by me!! The advantage here was I'd done a few of these kit things before and it was cheap. Your looking at a massive saving over a pre-built piece of gear. Oh, and it has some nice little LED's on it to tell you exactly what's going on with the state of both batteries. The kit used two switching MOSFETs in parallel instead of relays which means you don't have to worry about relays burning out and it can cope with switching loads of 100amps, more than what I needed. So how does it work? Basically what it means is when the ignition is on and the main battery has reached a voltage of over 13.5v (That means the engine is running or the battery is exceptional) the Auxiliary battery is connected to the charging circuit and charged. If the Auxiliary battery charge is below 10v it'll get about 2amps, which is like a plug in battery charger, once it's above 10v it'll get the full charge that is available from the alternator to quickly bring it up to normal. When the ignition is off the Auxiliary battery is automatically disconnected from the main battery and you can happily run it down to flat and still have the main battery for starting your Bus and hitting that sand or mud the next morning.
To fully exploit this dual setup I ran a second power cable to a second fuse box under the dash of the Bus and moved over everything I wanted to be able to leave on when the Bus wasn't running. So now I can leave the fridge, stereo, CB radio and interior lighting on all night if I want (or at least until the Aux battery goes flat) and still have my normal starting battery to get me going in the morning. So total cost for this dual setup, with all the cabling and kit was about $100AUD, I probably could've done it cheaper but I used very thick cabling for running from the back to the front of the Bus, this cost $27AUD alone! But I know I'm getting every AMP and Volt that I can up to the front of the Bus. Oh yeah, one last thing. If your going to run a battery down to flat and then charge it up again and do this often get a deep cycle battery. Plain old starting batteries don't like this much :( I used a starting battery but it had been sitting in my driveway for 2yrs and was pretty stuffed already (and free). Now I know it all works a deep cycle battery will replace it when I find some more cash. Update I added the deepcycle battery and it's great, I had the cd player going for 10hrs while I worked on my Bug and the auxilary battery still didn't run flat. It's run flat once when I blew a fuse and the battery wasn't geting charged but it soon recovered afer the fuse was replaced. |
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