Aux battery setup questions????

I've been enjoying my Taco a lot without further modifications, but with the addition of the camper top, I've found lighting in the bed to be an issue. Since my truck is an SR5, it doesn't have the cargo light, cargo light relay, or switch, so adding the bed lights would run me about $205 plus tax and shipping from Toyota Parts. I also enjoy hanging out with my buddies at the hunting lease and the campground and wish I had more exterior lighting around the bed of the truck. Therefore, I have been looking into another option that would include some exterior lights as well as USB plugs to charge speaker, phone, etc.
I'm not an electrical guy so I would like some input from you more knowledgeable folks about the setup I'm thinking about doing. I don't want to drain my starter battery, so an auxiliary battery is the way I'm leaning.

These are the lights I'm looking at:

$14 Shangyuan Interior Marine Strip Lights, 6 LED Utility Courtesy Light, White 12V Boat Lights, 6PCS

$14 Shangyuan Interior Marine Strip Lights, 6 Led Utility Marine Led Strip, White Led Courtesy Light, 12v Led Marine Interior Lights, Boat Interior Led Lights, 6PCS
Amazon.com : Shangyuan Interior Marine Strip Lights, 6 Led Utility Marine Led Strip, White Led Courtesy Light, 12v Led Marine Interior Lights, Boat Interior Led Lights, 6PCS : Sports & Outdoors . I'm thinking two in the camper top, one on each side of the camper top, and two at the back. That way I have basic lights all around the back of the truck and in the bed under the topper.
- The are 120 lumens each, so for six of them I'm calculating about 3 amps max.

This is the switch panel I looking at:

$21 Upgrade Blue 5 Gang Marine Boat Rocker Switch Panel Circuit Breakers, Waterproof Switch Panel with 15A Inline Fuse for Truck RV, Digital Voltmeter USB Charger Port DC 12 Volt Power Outlet Socket

$22 Upgrade Blue 5 Gang Marine Boat Rocker Switch Panel Circuit Breakers, Waterproof Switch Panel with 15A Inline Fuse for Truck RV, Digital Voltmeter USB Charger Port DC 12 Volt Power Outlet Socket
Amazon.com: Upgrade Blue 5 Gang Marine Boat Rocker Switch Panel Circuit Breakers, Waterproof Switch Panel with 15A Inline Fuse for Truck RV, Digital Voltmeter USB Charger Port DC 12 Volt Power Outlet Socket : Sports & Outdoors . It has two 2.1 amp USB ports and 5 switches, rated at 15 amps each. I would use the USB chargers for phones, bluetooth speakers, or flashlights. I was going to wire the lights in pairs to three of the switches and have two spare switches (I can't find a fused 3 switch panel with USB ports)

Here is where I need the help! 3 amps for the lights and 5 amps for the USB ports, so a maximum total of 8 amps. I doubt I will ever have all 6 lights on and have devices charging in both USB ports, but it's a possibility. I expect that I would have 4 lights on maximum with one device charging; so about 4 amps. If I understand correctly, that would drain my auxiliary battery at either 8 Ah max, or 4 Ah if I'm right about my usage.

Based on the above Ah calculation, I'm thinking about using this battery:

$44 UPLUS 12V 20Ah Deep Cycle AGM Battery, LP12-20 Rechargeable SLA Batteries, Replace for EXP12200, HR22-12, BP20-12, F19-12B, UB12200, FM12200, 6fm20, ML22-12, ML18-12, EXP12180, DJW12-20Z

$45 UPLUS LP12-20 12 Volt 20Ah Deep Cycle AGM Battery, DJW12-20Z SLA Battery Rechargeable Batteries, Replace for EXP12200, HR22-12, BP20-12, F19-12B, UB12200, FM12200, 6fm20, ML22-12, ML18-12, EXP12180
Amazon.com: UPLUS LP12-20 12 Volt 20Ah Deep Cycle AGM Battery, DJW12-20Z SLA Battery Rechargeable Batteries, Replace for EXP12200, HR22-12, BP20-12, F19-12B, UB12200, FM12200, 6fm20, ML22-12, ML18-12, EXP12180 : Health & Household which a 20 Ah battery. I'm thinking that should give me about 2.5 hours of runtime with my average load of 4 Ah.
PLEASE give some input as to whether or not I'm about right on this.

I looked up the specs of the battery at the manufacturer's website and it states the max. charging current at 0.3C. Some googling tells me that the charging current is C x Ah, so my battery would pull about 6 amps while charging (0.3 x 20 = 6). Based on this, my plan is to mount the battery in my windoor tool box and run 10 awg wire to it from my battery isolator which I plan to mount under the hood, near the starter battery.
- Battery Isolator:

TEENO 12V 50Amp ATV UTV Smart Dual Battery Isolator,Voltage Sensitive Relay for RV Boat Watercraft, Snowmobile Cruiser/Touring

$23 TEENO 12V 50Amp ATV UTV Smart Dual Battery Isolator,Voltage Sensitive Relay for RV Boat Watercraft, Snowmobile Cruiser/Touring
Amazon.com: TEENO 12V 50Amp ATV UTV Smart Dual Battery Isolator,Voltage Sensitive Relay for RV Boat Watercraft, Snowmobile Cruiser/Touring : Automotive
- Wire:

$32 10 Gauge Marine Wire 10 AWG Duplex Marine Grade Wire,20ft Tinned Copper Electrical Cable for Boat/Automotive/RV/Camper/Trailer Outdoor Use

$35 10 Gauge Marine Wire,20ft 10 AWG Duplex Marine Grade Wire Tinned Copper Boat Cable,Marine Electrical Wire for Boat/Marine/Automotive etc Outdoors Wiring
Amazon.com: 10 Gauge Marine Wire,20ft 10 AWG Duplex Marine Grade Wire Tinned Copper Boat Cable,Marine Electrical Wire for Boat/Marine/Automotive etc Outdoors Wiring : Sports & Outdoors
- I was also going to fuse the wire going from the starter battery to the isolator and the wire going from the isolator to the auxiliary battery with 50 amp fuses.

I don't want to burn up my truck so I want to make sure I'm sizing everything correctly. Please let me know if you think I'm on the right track.
Total cost for this project would be about $ 160.00.

This is where I plan to mount the auxiliary battery.



This is where I plan to mount the switch panel.


Any input would be appreciated.

 

Huh… that’s interesting . You have a 2020 access cab right ? On lower left switch panel of the steering wheel…. What do you have for switches . I have. 2020 sr5 and the switch is there . You have to pop the blank covers off in bed and there is already wires for the bed lights . It’s just covers with a little blank plug thingy.
If you are running wires for lights and extra accessories, make sure you draw up a basic idea of what you what/need so you can plan ahead . Or at least when you build your little electrical
Area you have ways to add in things later . try to keep everything in one location so any electrical work can be done from one spot . I just finished building a panel
For my alucab set up.
It’s fed from a breaker and fuse in the engine bay, and has a hard shut off for the canopy power

 

I don't have a switch at all at the lower left switch panel of the steering wheel. I read up on adding the bed lights on another post, so I checked on the switch, lights, and relay. I don't have the switch, relay or lights. I do have the connectors at the bed and behind the switch panel for the lights and switch to plug into though.
The inline fuses I'm planning on using have manual open and reset switches so I figured I didn't need another shut off. My plan is to put everything in my windoor tool box with the exception of the isolator and fuses, which will be in under the hood.

 

Oh strange …
You know, if you don’t have the bed lights, I personally wouldn’t get the own switch and such . I’d just run your own wiring to a little switch panel , and run a light where you’d think would fit your needs best

 

i’d use a 30amp fuse for 10awg isolator wiring.. plus when are you going to ever use 50amps? lol that’s overkill for charging a small 40ah pack or powering some lights. Keep in mind with distance you get voltage drop and higher amperage. You measure distance of wire runs power and return, so positive and negative. I have a 2awg although overkill on the wiring I wanted to be sure i have full 30amp charging for house battery plus another 30 amps for air comp and whatever 12v accessories i may want to run off that line. If anything go overkill on wire and smaller fuses that way the wire doesn’t become the fuse.