My duel battery system. (1 Viewer)

[General Sherman]

I have had some issues with battery/s and decided to fix it once and forall. I had previously used an isolator system but did not like the lack of control with not being able to "switch" over to the back up battery in case of an emergency.

I had decided to use a Marine switch to simplify things. The obvious problem with a switch is in order for the auxilary battery to charge the switch had to be on position 2 or ALL. When on position 2, 1 wouldn't charge and when on ALL, they both charged but could drain each other depending on the shape of each battery. This system worked fine for a season or two as long as I monitored carefully as not to over charge batteries. Unfortunatley, It eventually killed two RedTops so......

I now run a combination of Marine Switch with Battery Isolator. Please take a look at the diagram attached and seee if you see any issues with the way I have it now. With the Isolator, It will charge both batteries all the time which should keep them equal and not cause any overcharging. I now can keep the switch on 1 for normal starting/driving, wire accessories to 2 and not worry about running it dead while driving and switch to 2 if 1 ever runs flat. I can also still switch to OFF when stored and keep the batteries charged with a tender.

Any comments or suggestion are appreciated.

 

[canman]

I did the exact same thing a few years back. Had to replace the isolator once, but it was a no name brand. Replaced it with a Sure Power one a couple years ago, no issues to date. I also ran another switch just for my winch as I did not want anyone playing with it, so it is always in the OFF position (under the hood) until I go off-roading.

 

[e9999]

14AWG?

 

[General Sherman]

14awg was the guage of wire used for the exite wire to post #2 on the alternator. Sorry, I pilfered a diagram from the web and modified it for my setup.

 

[ntsqd]

FWIW the Sure Powers had a significant recall. If you haven't already suggest checking that yours isn't affected. Also, I think it was Tyco who bought Sure Power, don't expect their quality to be what it used to be.

Isolators are classically diode bridges. As such they have an unavoidable voltage drop. When I ran one years ago I found that neither battery ever reached fully charged.

My preference is now for Automatic Charge Relays or Voltage Sensing Relays. They're the same thing from different mfg's. Basically a solenoid switch that closes when the starting battery gets fully charged and opens when the alternator quits charging. One of those coupled with a marine battery switch is my ideal set-up.

 

[canman]

FWIW the Sure Powers had a significant recall. If you haven't already suggest checking that yours isn't affected. Also, I think it was Tyco who bought Sure Power, don't expect their quality to be what it used to be.

Isolators are classically diode bridges. As such they have an unavoidable voltage drop. When I ran one years ago I found that neither battery ever reached fully charged.

My preference is now for Automatic Charge Relays or Voltage Sensing Relays. They're the same thing from different mfg's. Basically a solenoid switch that closes when the starting battery gets fully charged and opens when the alternator quits charging. One of those coupled with a marine battery switch is my ideal set-up.

According to the link below, the Sure Power recall was for a battery separator.

http://www.cooperindustries.com/content/public/en/bussmann/transportation/recall_info_NA.html

Also, I think the type of alternator used by Toyota can be wired in a way to compensate for the voltage drop.

https://forum.ih8mud.com/threads/battery-isolators.199574/

 

[ntsqd]

Some voltage regulators can be adjusted to compensate for the voltage drop, but not all of them. The better isolators have a voltage sensing stud on them to help with this problem. Is that stud's voltage an average of the two battery banks, or does it favor one bank over the other?

A diode isolator or simple constant duty soleniod still means that the alternator has to charge both batteries all of the time where the ACR/VSR's get the starting battery(ies) recharged first and then start charging the 'house' battery(ies). That just seems like a better overall plan to me. Compromising the charging of the mains to charge the aux's doesn't make sense to me. Get the mains charged first, then go to work on the aux battery(ies). In a long operation period it may not matter, but in successive short operation periods it may matter a great deal.

 

[roberto84]

General Sherman, this sounds like a good enough electrical circuit to both charge and discharge your batteries. I do have a few concerns however. Since you have a limited alternator output, your batteries will continuously get lesser current than they require for proper charging. Every battery comes with a specified charging current amount which is important for extending life of the battery. If you keep charging them at lower current, the life of these batteries will significantly decrease.

Regards,
Roberto J
http://blog.7pcb.com

 

[e9999]

General Sherman, this sounds like a good enough electrical circuit to both charge and discharge your batteries. I do have a few concerns however. Since you have a limited alternator output, your batteries will continuously get lesser current than they require for proper charging. Every battery comes with a specified charging current amount which is important for extending life of the battery. If you keep charging them at lower current, the life of these batteries will significantly decrease.

Regards,
Roberto J
http://blog.7pcb.com

can you provide good sources for that bit of information? I am under the impression that batteries typically do better with lower current and that higher currents are only a compromise due to time constraints.

 

[Cruiserdrew]

I think Roberto84 really meant to say voltage, not current. He is only correct because of the voltge drop in the isolator. Through a diode based isolator, the OP will be chronically undercharging his batteries, markedly prolonging charging times, and assuring batteries that are never really full.

I agree that diode based isolators should be tossed in the trash. Automatic charging relays (aka voltage sensing relays) are where it's at.