Second Battery just for Starter?

[Dwon]

I want a simple dual battery setup that I haven't seen discussed here so I'm throwing out my question (I apologize if it has been covered elsewhere on the mud forum but I haven't found it). I want my current main Optima Yellow top to stay my main battery and power everything in my rig except the starter and I want to add a second starter battery to just power the starter. My first Optima Yellow lasted 6 years powering everything in my rig just fine, but there were a couple sketchy occasions out in the middle of nowhere when starting was strained after several days of sitting in one place without running the engine (powering hot water shower pump, charging phones, computers etc). I got us going but we were starting to sweat.

It seems like it would be a lot easier to just leave the main battery hooked up to everything except the starter and have a new little starter battery connect just to the starter. All the dual battery setups I see on here require fancy isolators etc., rewiring winches, lights, etc. and don't seem to pertain to what I want. My yellow top has done a great job powering my winch, lights, hot water shower pump, etc. I'm just worried about starting off that battery.

I do know that a deep cell is not the best choice for powering the starter but is great for powering electronics when the car is off because it can be completely depleted and charge back up with no ill effect on it. Starter batteries are designed for starting but will not tolerate being completely depleted. So my setup seems to make sense to me with my limited understanding of 100 series electrical requirements.

So here's my question.
Would it be as easy as I'm thinking to simply plop in a cheap little new starter battery and connect it directly to the alternator and starter independently of the main battery all together, so it could charge and start the rig on its own? Would there need to be a cheap isolator in there to prevent the main battery from draining the starter battery?

 

[TeCKis300]

I'd completely agree with you and do believe most dual battery setups are way more complicated than necessary.

The issue to me is not really the reserve capacity, but more a need for a guaranteed start. Not saying that reserve capacity is not important, but in my mind it's secondary. No matter how much reserve I have, I will always be tempted to deplete it. On the flip side, even with little reserve, if I can start the car, I'm safe.

My plan (which closely resembled yours) is this once I get around to it in priority order. It addresses the two issues discussed above without over complicated with dual wiring circuits for accessories etc.

1) Guaranteed Start - addition of a secondary small battery. This is tied into the main electrical circuit by a battery isolator solenoid. When the car turns off, the solenoid decouples this start battery from the electrical system so I always have it in reserve to start the car. When the car is on, the solenoid ties it into the main system to be charged/maintained. A manual 'jump' switch (or just jumper cable) allows it to make for a guaranteed start in case I deplete the main battery.

2) Extend Reserve Capacity - Upgrade main battery from the stock size to increase usable capacity.

 

[Sandroad]

If all you need is a guaranteed start, how about just carrying one of the portable emergency jump starters? They're only about $100 and are easily charged up via a 12 vdc outlet. They'll start the vehicle if the main battery gets too low. Seems like that gets as simple as possible. One example:

http://www.duracellpower.com/battery-chargers/jump-starters/instant-jump-start-system.aspx

 

[Sandroad]

And to answer the OP question, you can't just drop in a second battery connected to the alternator w/o using an isolator if you want each battery charged/used independently

 

[Dwon]

If all you need is a guaranteed start, how about just carrying one of the portable emergency jump starters? They're only about $100 and are easily charged up via a 12 vdc outlet. They'll start the vehicle if the main battery gets too low. Seems like that gets as simple as possible. One example:

http://www.duracellpower.com/battery-chargers/jump-starters/instant-jump-start-system.aspx

I've seen those, but they're bigger than a small starter battery. Might as well buy a car battery and use my existing jumper cables. At least the battery will fit under the hood. While I'm going that route I don't see why not just hook it up to the alternator via an isolator. All for under $100 ($50 battery, $15 cables, $15 isolator) and I don't have to pack it inside the cabin. ??? I don't know. Still up in the air.

 

[Hedgepig]

Along with your battery idea you could also look at how you consume and manage the power that you do have. For example if you use an inverter then you might consider replacing it with 12V chargers, devices etc. Inverters are very inefficient (particularly on low draw). I personally prefer a battery management system that warns/shuts off when battery voltage is low and allows me to parallel 2 batteries to start the engine/winch if I need to. Have you got the right alarm/switch point on your fridge. Personally I run the engine for a short while each day or two to recharge. What about solar panels on your rack and a charge controller?

 

[KlausVanWinkle]

I don't see the point in only hooking up the second battery to the starter. You'd still be SOL if the other battery was dead since you need voltage to run everything else.

I've thought about simplifying my next dual battery system. What I'd recommend is leaving everything hooked up to your oem battery. Do the T-maxx system install like I did. An auto system is going to be more reliable than you remembering to flip a switch. The whole point is to minimize the chances for human error. And just don't run anything off the aux battery. Then, if the primary dies, you can jump it with your aux. The aux is always protected when the car is off. You have dual battery power for winching, compressors etc. If worst came to worst, you could just swap the aux battery with the primary batter.

https://forum.ih8mud.com/threads/t-max-dual-battery-install.607791/#post7820405

You can simplify my install further by just running the supplied 8g wire between the positive terminals of both batteries.

 

[TeCKis300]

If all you need is a guaranteed start, how about just carrying one of the portable emergency jump starters? They're only about $100 and are easily charged up via a 12 vdc outlet. They'll start the vehicle if the main battery gets too low. Seems like that gets as simple as possible. One example:

http://www.duracellpower.com/battery-chargers/jump-starters/instant-jump-start-system.aspx

Not a bad idea. Though having a second underhood battery for starting gives a bit more assurance than a portable jump station. For the case when the main/primary battery goes dead and decides to fail and no longer hold charge, that second battery will start the car and keep it running to get you home.