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Kinda defeats the purpose then, you can't draw power for a load and charge at the same time. What's wrong with "you can't get there from here?". I could devise such a circuit with multiple multi-pole switches but you still couldn't support a load and charge at the same time. If you're happy with a shortened battery life, just tap the grounded battery and be done with it. I don't care if you have to keep replacing batteries, it's not my money you're spending.You need isolation switches to make this work.
Hold on there, cowboy.Actually, my last little bit wasn't directed at you Rebel. Simply offering that it can be done with some "isolation switches" doesn't help but further let people think it CAN be done on the cheap. Saying that, I've seen some people get away with $30.00 converters and to me, that seems cheaper that your proposed wiring with the busses, had that worked out.
To me there is nothing wrong with being frugal with your money, I'm of Scottish decent after all. I like simple clean and a good value. I'm just glad I didn't have to pay for that expensive converter in my truck, it came in it. If I hadn't found the new 100 A equalizer for cheap, I'd have gone with the convertor +battery, or at last resort the 2nd dedicated 12v alternator. My 12v demands are rather small, had they been large, the equalizer or alt would have been my first choice.
???WOW, swapping batteries every month, that's nice and elegant, convenient too. What if we need to tap off 20-50 A? How about a winch at 200-500A. You might not make it a month before killing the batteries, if you used the truck often. Please design this circuit where you can add isolation switches and make it work to provide 12v power for useful loads and properly charge the batteries without imbalance.
C'mon Sparky, educate us.
Hi Stuart - I don't understand how upset you seem to be over this. You are reading a lot into the simple comment I posted that that schematic would not work and the only way that schematic could come close to working is with isolator switches.It's not just about MONEY! Using switches to isolate a battery allows for a TEMPORARY use, period. While providing 12V power, the isolated battery's aren't being charged. We are taking about a cost effective method of getting a 12v supply for accessories in a vehicle with a 24V system, it could be a radio or a winch or anything in between. Using a bunch of cheap switches would require you to activate them in an exact sequence or you fry stuff. Even using a series parallel switch, while possible, will cost you $150-200 and is only rated for intermittent duty.
You are missing on what kills the batteries when you imbalance them, it isn't the load itself but your 28v charging system. It undercharges the battery that has been tapped for 12V and OVERCHARGES the battery that isn't. A 5A CB radio won't cause a SERIOUS overcharge but even it, over time, will shorten battery life. I've seen this happen. It will even happen if you have one battery that is new and one that is slightly used previously. Don't you wonder why you don't just replace one battery in a 24v system but MUST replace them in matched pairs (same exact specs and brand), preferably from the same lot number? The answer is simple, they will become further imbalanced even if you swap them from time to time.
In the above situation you mention with 4-12v batteries, you could take 2 equal
batteries out of the 24V loop, discharge them in parallel and bring them back into a series-parallel situation, theoretically keeping the batteries in balance. The current would flow to the batteries in the lower charged state in the parallel part of the series-parallel configuration. STILL, you can't charge them AND draw power off them at the same time.
So what don't you still understand?
Peace.OK, fine I got a bit pissy. If you understand all that YOU SEEM TO, why did you tell him he could fix it with some switches? You really can't, and you appear to understand that. Beyond those very light loads, just a couple of amps, it does kill batteries. Do you have any idea how many people have had battery problems doing this? Can we just nip this whole thing in the bud now?
Many years ago some guys on the early internet posted information regarding certain military vehicles that was either marginally true or totally UNTRUE and became gospel. I'd perfer we kept our information reliable as possible. I'd hate to see a guy spend lots of time and effort going down a dead end to only find himself with a burning truck, you know this can happen with the current available with 2-4 12V batteries.
I still don't understand the crap about the money. I told him a $30.00 converter would probably be cheaper than the wiring he was planning and your switches, which won't work as desired. I still think an equalizer (extra battery(s) optional) or second alternator + battery would be better, but for those on a budget a cheaper converter will probably do (also better with another battery, even a motorcycle dry cell). I certainly won't try to talk anyone into an EXPENSIVE converter like the failed one I have! You don't always get what you pay for, but you have to pay for what you get.
Goodnight