Cheap secondary battery setup

Hi all,

Looking to do a budget secondary battery setup so I don't have to worry about running down my battery on the ferry playing with the car stereo or watching movies on it etc.

I am thinking I will pick up something like this:

Patioer 12V 140 Amp Dual Battery Isolator & ATV UTV Wiring Cable Kit, Double Battery Chargers,Voltage Sensitive Relay - VSR

Patioer 12V 140 Amp Dual Battery Isolator & ATV UTV Wiring Cable Kit, Double Battery Chargers,Voltage Sensitive Relay - VSR

https://www.amazon.ca/dp/B08VSJVMD7/ref=cm_sw_r_apan_glt_i_B8D2C136CXS7FZMKDSAG?_encoding=UTF8&psc=1

I don't have a crazy audio setup going but have a Kenwood amp feeding my front component speakers and a powered 8" subwoofer enclosure as well as an Atoto S8 gen2 10.1 screen Android head unit. Currently I am able to run down my older Costco brand battery pretty quickly when engine is turned off.

Would I have to buy a deep cycle battery to work with this setup? I would really just like a small battery that I can fit in somewhere in the engine compartment and can give me 2-3 hours of low to medium volume listening.

Cheers

 

You would need either a deep cycle battery or a lithium battery. As far as I know I've done one of the cheapest dual battery setups for under the hood. Using a 24DC battery and

$28 MaySpare 12V 140Amp Voltage Sensitive Relay VSR Double Battery Automatic Charging Relay Dual Smart Battery

this VSR for $39.

 

160 pages of ideas for your reading pleasure:

https://www.tacomaworld.com/threads...ts-see-them-multiple-batteries-thread.295653/

 

Thanks, so which battery did you use exactly?

 

Thanks I started looking at that thread but they all looked too fancy for me

 

The wiring nightmare of a firehazard going on in the engine bay of your truck should really be looked at. OP. Dont do something like this.

 

Would something like this be a good as a secondary battery just for powering everything with engine off?

12v 20Ah LifePo4 Battery Deep Cycles with BMS Lithium Iron Phosphate for Lamp Kids Scooters Fishfinder Lawn Mower Power Wheels Solar Panels RV Household Appliances Electrical Tools Include Charger https://www.amazon.ca/dp/B09HTW799S/ref=cm_sw_r_apan_glt_i_RMBBCKKBNQCJFTB8Z2XB?_encoding=UTF8&psc=1

 

You could also just get a nice Deep cycle to replace your costco battery.

 

Yeah I would love to do that instead but don't know how long it would last with engine off and don't want to get stuck when ferry starts offloading. I have one of those battery block jump starter things but it doesn't seem to work if the battery gets drained too low.

 

That is terrifying. Don't do this OP.

Upgrading your stock battery would be a really good starting point before going dual. Why supplement a crappy battery with a second one instead of just getting a good battery?

Plus dual starting batteries won't be much better. You'll need a deep cycle regardless.

I bet you'd be fine as long as your stereo isn't pulling crazy juice. I can run a fridge for 3 days without starting my truck with my single 27f AGM.

 

Unless you somehow rewire your stereo to run specifically off your "house battery" instead of your starting battery, a lithium battery is not going to help you.

My current 66AH optima Deep Cycle gives theoretically 30-33AH of usable battery before it won't start my truck. Which is more than that 20AH of 100% usable power you'd get from the LifePo4 you mention.

 

How many amps/watts is your Kenwood amp and added subwoofer?

 

another thought, can you disable/turn off your sub when you're listening parked? that'd be a good way to reduce consumption.

 

And OP, please keep your questions coming. We aren't trying to disparage your ideas, we just want to help you come up with a workable system for you needs/situation. I'm no pro in wiring but I have a good amount of experience and love chatting about this stuff. Previously had a 3 deep cycle setup with self jump starting capabilities.

And I know others are like me! This place is full of great folks and great information.

 

Thanks for the replies. To my limited understanding using the battery isolator I quoted above I thought that everything in the truck would run off the secondary battery when the engine is off and my regular battery would pretty much become dedicated to starting the truck and would always stay at a required level to do this. I liked that part of it as I could run my stereo and if I happened to run down the secondary battery I wouldn't be stuck. Even if I buy a new better quality deep cycle battery and just replace my existing one I will always have to keep it in the back of my mind that the battery can run down.

I can turn the bass right down on the subwoofer so it's not really doing much especially if I'm sitting on the ferry my volume levels will be pretty minimal.

This is my old amp that I've had forever:

https://www.crutchfield.com/S-hasbBIQ4BTX/p_113KAC7201/Kenwood-KAC-7201.html

Subwoofer is this one:

https://rockfordfosgate.com/products/details/ps-8/

 

I think that's how an isolator works. But you would have to wire your components to only draw power from the secondary battery. You might need to get creative with some relays. Key on power for the stereo powers the relay, which closes the relay switch connected to the secondary battery.

If you want to get really hokey, there's solar powered 12v chargers. The one I bought is very weak but it was enough to give my weak battery a tiny bit of charge so it would start in the morning.

$40 Sunforce 52013 1.8-Watt Solar Battery Maintainer (Pack of 2)

https://www.amazon.com/gp/product/B001OG68Q4?ie=UTF8

Heck, go super hokey. Mount a bicycle crank to an alternator so all you have to do is pedal and listen to your music all you want. Kidding of course.

 

Walmart 24DC Battery

 

What exactly is terrifying about my setup?

 

Everything in your truck drains power from your starting battery. Adding an isolator between the starting battery and the second battery would simply charge the second battery when the vehicle is running. Once the vehicle is turned off, the second battery would be isolated, therefore doing nothing to help your starting battery, which would still have all of the loads connected to it.

The purpose of that kit is to add a second battery to run aftermarket, separate loads like a completely separate add on stereo, extra lighting, and stuff like a winch. That way those specific things dont drain your starting battery. Since you want to run the stereo that is already wired as part of your normal electrical system you simply need more capacity. A deep cycle is your best bet. A second battery could be added via an isolator that has the ability to manually connect so you could self jump start if the primary starting battery was drained too low to start your truck. I used this functionality quite a few times, as originally I had two isolated deep cycle "house" batteries and a standard starting battery. My standard battery was in pour health but I could link them together at the push of a button. When replacing the starting battery I went with another deep cycle.

Another item I want to talk about is the lithium batteries brought up. Neither the isolator nor any vehicles charging system can safely charge a lithium battery. They need different voltage and charging profile (the voltage has to change as the battery is recharged). This would require a DC to DC battery charger that specifically has the ability to charge lithium batteries. Some of these DC to DC chargers have built in isolation, but only a few of them have the ability to self jump start. They cost a lot more, too, and you really don't need that for your use case.

One thing you could do to help with your worry about running the main starting battery down would be to wire in a voltage monitor, you might even be able to just get one that plugs into a cigarette plug in your truck. As your battery is drained the voltage will slowly drop. I cant recall off top of my head what the standard accepted voltage is for still being able to start your rig, but it would be no different then how most DC fridges work. They turn themselves off automatically once the voltage drops to a certain point, so that you will still be able to start your vehicle.

Please keep your questions coming. I know this was a lot I just typed. I hope I didnt add to any confusion.

 

Sounds like you know a thing or two on the subject. I may need to pick your brain to solve a puzzle.