Dual battery setup w/ isolator

[Dan Robinson]

With a couple of new recent additions to my car's equipment circuit, it's now drawing enough current to drain the stock battery quickly if it's left on without the engine running. So, it's time to move the circuit off of the stock battery and onto its own deep-cycle battery, with an isolator to allow the alternator to charge it.

I'm hoping several chasers have done this before and have some insight or recommendations. My issue is that I have no room for another battery under the hood, it will have to go into the passenger compartment or in the trunk. As such, it will have to be sealed, obviously.

I've done some homework and it appears the setup is very simple - just a new battery and the isolator - but I'd like the deep-cycle battery to be robust enough to keep everything running for a couple of hours minimum if needed (to keep timelapses going on the dashcams, for instance).

 

[TJKLECKNER]

I have used this setup for the past year. I have enough offline power for my cameras, phones, tablet, and laptop. Very simple to setup and relatively low cost. The hard part is running the 2/4 guage wire (through thew firewall) from the battery to the second (house) battery. Then find some metal in the interior for ground (seat bolt).

 

[nmoore125]

A few of us run this exact setup on our team. Works really well.

 

[James Hilger]

Go for it. Well worth the time. And agreed, running the power wire is the hardest part. I use 0 guage.

 

[Dan Cliche]

I have a secondary battery inside the car. I used a sealed yellow top optima. Safer then ordinary battery when used Inside the car. I got a 100 amp breakers on each positive terminal. 80 amp breaker between the battery and the inverter. I control then with an RV isolator relay. Used old boosting cable to connect the 2 batteries. Also upgraded the main battery to an oversize Optima, some Honda have undersize original bat, no more light diming when breaking!

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[Dan Robinson]

Thanks for the replies. A couple of questions:

What happens when the second battery drains completely? Will the circuit still have power? I've read some information that suggests that when the second battery gets depleted, it won't be able to power anything again until it recharges (after a period of running the engine/driving). That would mean the chasing equipment circuit would be down until the battery could recharge. I'm assuming the isolator allows only a small charging current from the alternator/stock battery side, not the full current that would be needed to power the circuit in the event the second battery is dead.

I've also run across some info that suggests that certain cars' computers may not allow enough alternator current to charge two batteries simultaneously. That is, it's only configured to provide enough juice to power the stock battery, and adding the second one might result in unpredictable charging behavior and/or damaging the charging circuit.

 

[Dan Cliche]

To answer your first question, in my case, the isolator/relay is control with the 12v/cig lighter outlet, so if the second bat gets drained, circuit still have power. When i turn the key one notch, the relay goes on, the batteries starts "equalizing" , but i won't let it stay in this state for more then a few seconds, i just start the engine and let it charge. As soon as your engine run, your electronics will have power even if your sec. bat. was dead. P.S. Some cars have the 12v outlet always ON, in this case you would have to manualy control the isolator, not the best option.

A good isolator will let pass a ton of current, so a yellow top optima is a good choice (hybrid between normal and deep cycle bat). Its support deep cycle and fast charge. Ordinary battery don't like being drain and ordinary deep cycle usually don't like fast powerful charging.

I believe some cars might ends up with prematurate alternator failure if you make it charge 2 batteries. I first installed the second battery in 2005 and never ad any problems. But i initialy made some test to make sure i was not pulling too much from my alternator. I made it charge 2 batteries with one completly drain, checked the amps out of the alternator, and it was much lower then the max output of the alt. If for some reason your 2 bats gets drain, i would suggest to unplug the isolator/relay for a few minutes when you start your engine.

I don't have fency meters like RVs, but my inverter will beep when voltage gets low, then i will start my engine to recharge. But it happens rarely, usualy when i sleep in my car and lets a small 12v fan run all night. I made some test last year to make sure my old secondary Optima was still good. I was able to let my laptop run with open screen, full brightness for 14 hours before the inverter starts buzzing. Pretty good considering my battery is a old and fairly small Optima d51r.

Another great feature of having 2 batteries, i was able to boost myself a couple times over the years. Like having my headlight on while hiking at Loveland Pass CO, or a forgoten sealing light overnight after a long chase day.

 

[Dan Robinson]

Has anyone tried using one of the dual-purpose batteries (like a YellowTop)?

 

[TJKLECKNER]

To answer your first question, in my case, the isolator/relay is control with the 12v/cig lighter outlet, so if the second bat gets drained, circuit still have power. When i turn the key one notch, the relay goes on, the batteries starts "equalizing" , but i won't let it stay in this state for more then a few seconds, i just start the engine and let it charge. As soon as your engine run, your electronics will have power even if your sec. bat. was dead. P.S. Some cars have the 12v outlet always ON, in this case you would have to manualy control the isolator, not the best option.

A good isolator will let pass a ton of current, so a yellow top optima is a good choice (hybrid between normal and deep cycle bat). Its support deep cycle and fast charge. Ordinary battery don't like being drain and ordinary deep cycle usually don't like fast powerful charging.

I believe some cars might ends up with prematurate alternator failure if you make it charge 2 batteries. I first installed the second battery in 2005 and never ad any problems. But i initialy made some test to make sure i was not pulling too much from my alternator. I made it charge 2 batteries with one completly drain, checked the amps out of the alternator, and it was much lower then the max output of the alt. If for some reason your 2 bats gets drain, i would suggest to unplug the isolator/relay for a few minutes when you start your engine.

I don't have fency meters like RVs, but my inverter will beep when voltage gets low, then i will start my engine to recharge. But it happens rarely, usualy when i sleep in my car and lets a small 12v fan run all night. I made some test last year to make sure my old secondary Optima was still good. I was able to let my laptop run with open screen, full brightness for 14 hours before the inverter starts buzzing. Pretty good considering my battery is a old and fairly small Optima d51r.

Another great feature of having 2 batteries, i was able to boost myself a couple times over the years. Like having my headlight on while hiking at Loveland Pass CO, or a forgoten sealing light overnight after a long chase day.

This is the isolator I use. Do you believe that it could cause premature alternator wear? Also note that I rarely ever fall below 12.6v (80%) on the second battery between drives.
http://www.wirthco.com/battery-volt-battery-isolator-20092-p-1186-l-en.html

 

[Dan Robinson]

Some additional info: I just used a multimeter to measure the current draw of my circuit. 3 amps without the laptop (just the dashcams and chargers), between 4 and 5 amps with the laptop running.

 

[Dan Cliche]

This is the isolator I use. Do you believe that it could cause premature alternator wear? Also note that I rarely ever fall below 12.6v (80%) on the second battery between drives.
http://www.wirthco.com/battery-volt-battery-isolator-20092-p-1186-l-en.html

Well i'm not an expert, i was sharing the experience i have with my set-up but i'm sure it's safe in most case. Like Dan said above, modern cars have protection from the computer or fuse to avoid over using or frying the alternator circuit.

My brother have a DC amp meter so i was able to test the worst case scenario (drained secondary + low main battery) and the current load was lower then my car's max alternator output.

 

[Dan Robinson]

I made the decision today to get an X2Power hybrid deep cycle/standard battery. That avoids the need to do a major rewiring job for an isolator and any unexpected future issues with the alternator. I already have a Start Guard which is a mini UPS for the power hit while cranking the engine on startup. Hopefully this will be the solution!