Some Notes on my 2021/2022 Gen 2 Taco Upgrade (Seriously Draft)
Updated: 4 January 2022
During late-Summer 2021 we decided that it was time to start thinking about camping again. For months we had been wrestling with buying a trailer (shout out to TurtleBack Trailers as our final choice), sticking with our current RTT (Roof Top Tent) mounted on a bed rack, installed on our 2015 Gen 2 Tacoma Off-Road pickup, or going a completely different route. We walked our options for a few months and considered factors like how often we’d be camping, whether we were willing to take on monthly storage fees for a trailer (or chew up a big chunk of garage space), how many seasons we’d be likely to camp… We decided that we’d probably be best served, at least for now, by dropping a cap on the bed of the truck, sticking with our current RTT (a ruggedized Tepui Autana IV), and using my daily driver as our camping rig. We’d like to have enough “off-grid” resource to be able to regularly camp fairly far away from civilization for at least a week, and this implied some kind of power subsystem. I’m also an Amateur Radio Enthusiast (Extra Class), and having power available to support radio use, is a really good thing. We’ve also been concerned, since we moved to Colorado, that we might have to evacuate at some point. We’re not “preppers”, by any stretch, but occasionally, large chunks of Colorado catch on fire. We’d like to have sufficient resource to be able to evacuate ourselves and our cats to a safe distance if necessary without having to rely on infrastructure. How to control/manage power… Well… I could drop about 4,000+ dollars on a commercial solution, which ends up meeting most of my needs, but… I’m an Electrical Engineer. Thus begins my journey to build an complete OSHW (Open Source Hardware) focused implementation that is more flexible and maybe a little less expensive than things like and “S-Pod” or “SwitchPro” controller.
Overview
Our Gen 2 Tacoma has been my daily driver since we purchased it new in mid-2015. We fitted it with a bed rack in about 2017 and dropped a ruggedized Tepui Autana RTT on the rack. We used the setup for a single season and found that while we loved the tent, a lack of power and other amenities made camping less desirable. We’re both experienced off-grid campers, but much of our experience has been on foot. I’m also a licensed Amateur Radio Enthusiast (a “HAM”), and I’d like to start becoming more active. This requires (especially for HF hardware) a good bit of available auxiliary power. We’d also like a fridge and a semi-proper cooking arrangement. In mid-October, I purchased an RLD Designs cap for the Tacoma. Unfortunately, RLD Designs manufactures their products in South Africa. The waiting list for production and delivery puts us on a projected installation schedule around April 2022.
Once we established when the cap would be available, I started looking at lighting and auxiliary power options. To be frank, the cost of installing a set of 12VDC relays and some switches is downright ridiculous. Add to that the fact that most, if not all, of the products on the market today for remotely controlling and monitoring vehicle systems are proprietary, and inflexible. I spent a weekend looking at products like those made by “sPod” and “SwitchPros”, and came to the conclusion that if I was going to pay more than 1000USD to set up power distribution and control, I wasn’t going to settle for simply being able to control six relays with a jinky little proprietary touch screen or some mechanical switches.
Requirements
DC Power
My overall DC Power requirements include support for a minimum of one auxiliary battery. I prefer Lithium Iron Phosphate (LiFePO4) batteries, because they are (1) far more power and mass efficient than lead based batteries (2) they perform well at low temperatures (3) they can be recycled, and (4) they provide charge/discharge cycle lifetimes on the order of 2,000-5,000 cycles. They are more expensive, but only if you don’t consider the lifecycle cost of lead acid batteries. I’d like to be able to parallel up more than one battery if I decide to install an inverter later. The use of LiFePO4 battery chemistry largely eliminates installation under the hood. I’m not too upset about this to be honest. I’m putting a “house” on the bed, and like the control boxes, the cost of an auxiliary battery tray is about 200-250USD. I also find that I probably need the engine bay space that the under-hood battery solution would eat for electronics.
As of January 2022, I’ve decided that placing electronics in the engine bay is too painful (and overpriced) to consider. I did create a bunch of templates, however, for mounting plates to address the following underhood mounting locations:
- The space behind the starter battery and firewall. I was going to have to relocate my clutch fluid reservoir, so I solved that as well
- The space on TOP of the main fuse box
- The open space on the passenger side of the engine bay
I’ll be placing the template drawings and the basic build info in the public domain sometime soon. I’m tired of seeing people pay $150+ for a metal bracket. If you can use an angle grinder, a power drill and a pop rivet gun (and probably a screwdriver or allen key), you can easily make your own.
Auxiliary Battery
I’m installing a LiFePO4 battery, with a minimum capacity of 75 Wh, in the bed. I’ll need additional space for a 2nd battery to be wired in parallel. The battery will require both discharge monitoring capability, and a service disconnect. The service disconnect requirement can be met with a circuit breaker. The auxiliary battery shall be mounted in a dedicated box that is both secured against shock/vibration and that provides protection against incidental impact.
Solar Charging
I require the capability to charge the auxiliary battery from an externally deployed solar array. An MPPT charge controller is required. The connector shall be available to support outside connection to the solar array with the truck secured. The preferred connector is an externally mounted 50A (or greater) rated PowerPole connector.
Alternator Charging
I require the capability to charge the auxiliary battery from the vehicle alternator. This will require running a heavy gauge cable set to the bed. The cable shall be Ancor Tinned Marine Grade battery cable. The cables shall be protected by a proper sleeve (e.g. wireloom, or split rubber tubing). The cables shall be terminated with appropriate connectors that are both mechanically crimped and soldered. Both +12V and ground shall be run on dedicated cables. Ground termination for all aft power fixtures shall be connected to the ground cable feeding from the engine bay. No local chassis terminations will be used.
Overcurrent Protection
The alternator charging circuit and the top tier load circuit shall both be protected by a circuit breaker rated no less then 50A. The alternator charging circuit breaker shall be located just after the main battery, prior to the cable pair leading to the bed.
Battery State Monitoring
Power Generation State Monitoring
Distribution Fixtures
The after power distribution panel shall be mounted in close proximity to the battery box, and should fit within the space, forward of the wheel well on either the starboard or port side of the bed.
Physical Mounting
The aft power distribution board shall be made of marine grade plywood, and shall be secured to a Molle panel mounted via the bed rail system.
DC Power Distribution
Forward Power Distribution Requirements (Cabin to Front Bumper)
The main battery feed shall be accessible at the aft power distribution board via a bus bar rated for a minimum current of 100A. Engine bay ground shall be accessible at the aft power distribution board via a bus bar rated for a minimum current of 100A. The engine bay shall also have dedicated bus bar access for both 12VDC and Ground.
- Behind Grille Light Bar
- Ditch Lights
- UHF/VHF Radio
- Underhood lighting
Aft Power Distribution Requirements (Bed)
- 2x PowerPole (45A)
- 2x 5VDC USB (high current)
- 1x Cigarette Lighter Connector
- 1x Dedicated PowerPole Connector (45A) for fridge
Future expansion for an on-board inverter (high current PowerPole?)
Auxiliary Battery Relays Supporting…
- Connectors listed above
- Perimeter Lighting (Spots)
- Cap Interior Lighting
- Fridge Power
- Future Expansion
