A BETTER (better?) three battery set up (Opinions wanted)

Ok, listened to everyone (thanks one and all) and went back to the drawing board. I eliminated any possibility of mixing 24 and 12 volt, and got rid of the relay due to failure issues / concerns and provided for any amp load you care to use. Then, just for those that want it, I put in an optional Buck Boost Converter to run accessories (lights, radio etc.) from the deep cycle batteries regardless of them being in 12 volt or 24 volt mode.

Three Pole Double Throw switch options:

100 Amp current ($35) 100 Amp Disconnect Knife Switch 100A 3 Pole Circuit Breaker Backup Generator 3 | eBay

225 Amp current ($90) 225 Amp Disconnect Knife Switch 225A 3 Pole Circuit Breaker Backup Generator 3M | eBay

400 Amp current ($150) 400 Amp Disconnect Knife Switch 400A 3 Pole Circuit Breaker Backup Generator 3L | eBay


For the OPTIONAL 12 volt accessory convertor ($160) (8 Amps but larger are available) Buck-Boost DC/DC converters 12 volts to 12 volts, 24 volts to 24 volts, 24 volts to 19 volts, 12 volts to 6 volts. DC/DC conversion

I am selecting the UDC-1212-8 modle as it will accept an input voltage as low as 10 volts (discharged deep cells) and as high as 40 volts while maintaining a regulated 12 volts. It does not matter which mode the batteries are in (12 vs. 24) or if the batteries are being charged from the alternator. As I said this is totally optional but would be a real benefit for those that need to run accessories and NOT run down the starting battery.


With the knife switch in the shown position the house batteries are wired for 24 volt output and there is no connection to the Perko switch at all. (The fact is, if desired the Perko switch could be eliminated.)

With the knife switch "thrown" to the other position both house batteries are wired for 12 volt output and made available to the Perko switch and ALL three batteries can be used for starting and will be charged by the alternator.

If the knife switch is in neither position (off) both "house" batteries are shut off and there is no power to the Perko switch or the Trolling motor (accessories will still receive power from ONE battery). If desired a small toggle switch can be added to disconnect the Buck Booster.


Advantages:

Can charge all three batteries from engine alternator.

Can use all three batteries to start the engine.

Complete isolation of the 24 v from the 12 v systems.

Can run 12 volt accesories without draining the starting battery or "tapping" a single house battery causing uneven wear on the house batteries.



Questions, thoughts, suggestions???

Re: A BETTER (better?) three battery set up (Opinions wanted)

as much as i find this intresting i have to wonder if the price is worth the results. a additional alternator on 24v dc seems a better option. im not sure what kind of motor we are on about but im presuming inboard as most outboards could not supply the ampage to charge 3 batteries on a short run. even adding a alternator to a outboard (belt drive) may be a option.

if i was going to look for a pure electrical fix to this i would be looking at making 3 (12vdc) isolated outputs from the charging system.

Re: A BETTER (better?) three battery set up (Opinions wanted)

Need to pull the accessories off the bottom battery in the 24V bank.

I'm doing almost the same thing with a Perko Battery switch and a Marinco 12/24 receptacle and plugs. I liked the relay concept you had earlier as the switching was all automatic. The one thing I don't like about my setup is manually switching things back-forth... Plug in TM and flip batt switch to #1 to use TM, flip batt switch to #2 and plug in charging plug to charge the 24V bank. Kind of a hassle that could be eliminated with your original concept of using a relay. If you could find a relay that switched the contacts like the knife switch "all at the same time" (100% no fault) that would make things easier.

Re: A BETTER (better?) three battery set up (Opinions wanted)

Bubba1235 said:

By pulling the accessory booster from the top battery the load is shared by both house batteries in 24 volt mode and the alternator in 12 volt mode.

If you like I'll put the revised relay system up tomorrow when I get it on Photobucket.

Click to expand...

Pulling accessory power off the top battery while in 24V mode will have 24V going to the accessories, that's why I was suggesting to pull the accessory power from the bottom battery. The bottom battery will supply 12V to the accessories, in 24V mode or 12V mode. That's the way I'm running it in my boat. When I want more battery capacity for house loads (fishing lights) I parallel the 24V bank with the Marinco 12V charging plug. (I guess I shouldn't say 24V bank for my boat as it really depends on which plug is in the receptacle, could be a 24V bank or 12V bank.)

I agree that the system should be 100% fault free, but like the simplicity of using relays, no flipping switches. The switches work (or in my case plugs), but they can be a hassle.

Re: A BETTER (better?) three battery set up (Opinions wanted)

glenn property of pam said:

if i was going to look for a pure electrical fix to this i would be looking at making 3 (12vdc) isolated outputs from the charging system.

Click to expand...

MinnKota makes a 2 bank DC Alternator charger that would charge the 24V bank automatically off the alternator. But,,, it's limited to 10amps/bank. That's not much output for a depleted battery that could accept 20-25 amps for quicker charging. I think MK designed it to add "some" run time to the batteries, not to completely recharge them.

Re: A BETTER (better?) three battery set up (Opinions wanted)

Bubba1235 said:

Nope, that's the reason I used a buck booster.

Click to expand...

Buck booster eh? I read that first time through, but it didn't register to me that it was being used and in the diagram. The diagram probably needs some clarification so no one else makes the mistake I did, it wasn't clear to me that the orange box was a 12 power supply, I though it was accessories.

Re: A BETTER (better?) three battery set up (Opinions wanted)

must admit i like the switch and it can be bought in 4 pole as well which gives even further options. My boat has a 5/5/5 charger that will maintain the all 3 batteries off the alternator when its not plugged in (10 amp max transfer) but as my outboard is rated at 6 amps its has no real use.