David's diode schematic
Here's a simple schematic of a diode setup I use to prevent a bad battery from draining the good one(s). I use four in my work truck, but this shows only two. As you say, "only good for what it's worth".
Love the site. Learned a bunch, and still learning. Keep up the great work.
By all means, feel free to distribute the schematic and information as you please.
You can use this circuit with any number of batteries, until you reach the point where your wires melt. Yes, just add another diode pair for each battery. My work truck charges from an external charger and a multi-battery isolator to the alternator, and am soon to add solar panels, all paralleled up.
I used some diodes I had laying around my lab. I can't remember if they are 50 or 80 amp rating each. It doesn't matter too much, as long as you're at least double the expected current draw. They aren't expensive, about $4 (US) I think. The heavy diodes are always the stud mount type and care must be taken in mounting to avoid shorting out the whole system. I used a couple of Bud aluminum chassis boxes. Wiring the 8 ga. wire can be a bit of a nuisance just because it's so stiff. For an RV, 10 ga. would probably do fine.
I used a shareware program called "SchematiCad". You can download it free from SJMTech. It's $20 (US) for registration, which allows file saving and printing. Not the greatest program in the world, but it doesn't cost $1,000 like much of the electronic software. I haven't registered my copy, yet, so I copied the schematic to the ClipBoard and pasted it to the email.
If you have any further questions, please don't hesitate to contact me. I'm glad I was able to contribute something that might be useful.
Many thanks to David for these plans!