Window trickle charger? Permenantly installed in fuse box?

care_mentor_288 · March 2

Sometimes I travel for a 2-3+ weeks at a time and in the past the battery died. I've been able to leave the car plugged into a trickle charger in an underground garage.

Now, I've got to park outside when I'm gone. The problem is, my family might need to borrow my car while I'm gone and they can't be bothered plugging and unplugging things.

So, I'd like to install a solar panel permanently in the window. Maybe something like this? https://www.amazon.com/gp/product/B07DFD3RMS/

I read on a random truck forum that I might be able to plug it into the fuse box somewhere and not have to run a wire to the battery directly.

1) Any advice on where to plug it into the fuse box?

2) Any advice on where to install it? (maybe up by the passenger sun visor?)

Maybe something like this:

Dean2 · March 4

This thread should help a lot. You want to connect to the battery or the jump posts, preferably NOT in the fuse box.

care_mentor_288 · March 18

On 3/4/2024 at 7:15 AM, Dean2 said:

This thread should help a lot. You want to connect to the battery or the jump posts, preferably NOT in the fuse box.

Thank you @Dean2!

I am looking to permanently install a solar trickle charger, probably where the passenger visor is on the front windshield. It feels like it would be a lot harder to run through the firewall to the battery instead of to the fuse box. It won't be much draw.

Any advice on where to run it or where to connect it?

Thank you!

care_mentor_288 · May 9

So, I'm one step closer to installing the trickle charger.

Currently, I'm planning on tapping into one of the fuses in the driver's side internal fuse panel.

Is there a problem with tapping into the main PWR fuse?

Listed as fuse 32 here: https://www.startmycar.com/us/lexus/rx-400h/info/fusebox/2007

And listed as fuse 79 here: https://www.clublexus.com/forums/rx-2nd-gen-2004-2009/949043-windows-not-working-at-all-where-is-the-fuse.html

My thought is to use suction cups or double-sided tape to connect the trickle solar charger to the window where the passenger sun visor goes. Then run the wire across the top of the window to the top of the drivers' side, then down the pillar and to the fuse box. Then connect to a part of the fuse panel that is always hot.

Q: Any disastrous consequences?

Q: Any better fuses or locations to tie into?

care_mentor_288 · May 9

Ohhhh Even better idea! I could mount it to the sun visor and tap into the visor light for power!

Good idea? Terrible idea?

care_mentor_288 · May 13

I'm thinking I'll add a fuse tap to the existing fuse.

Important: After watching a long youtube video (below) if the solar pannel doesn't get enough sun then the charge controller will slowly drain the battery.

Important: Fuse tap allows this all to be fused. However, fuse tap orientation matters, if it's hooked up backwards then both fuses are in series, not parallel.

Connector types:
- Fuse Tap
- SAE 2-pin connector (also called SAE Connector Bullet or SAE Quick disconnect)

Thought:
A normally open relay could stop the parasitic draw. These are also sometimes called Voltage Sensitive Relays
Could add a VSR Voltage Sensitive Relay to disconnect solar charge controller when there is no power coming from the solar panel. This might help with parasitic draw. This might be a bad idea because the relay could take a fair amount of the solar power to close... https://diysolarforum.com/threads/relay-to-shut-off-solar-panel.15331/
Maybe a latching relay would work: https://diysolarforum.com/threads/relays-nc-vs-no-or-other-solution.2267/

Seems like Harbor Freight has Thunderbolt Solar products that will help/make this easy:
- Simple solar charge controller: THUNDERBOLT SOLAR 100 Watt Solar Charge Regulator SKU(s)
96728, 94048 $20 https://www.harborfreight.com/7-amp-solar-charge-regulator-96728.html
- Kit to help with wiring: $14 THUNDERBOLT SOLAR Solar Power Connection Cable Kit SKU 59171 https://www.harborfreight.com/solar-power-connection-cable-kit-59171.html
- Small solar panel, could get 2: $15 THUNDERBOLT SOLAR 1.5 Watt Solar Battery Maintainer SKU(s)
64251, 44768, 68692, 62449 https://www.harborfreight.com/15-watt-solar-battery-maintainer-64251.html
- Hub if I want multiple panels $18: THUNDERBOLT SOLAR 400 Watt Universal Solar Connector SKU 68689 https://www.harborfreight.com/400-watt-universal-solar-connector-68689.html

Key thoughts and notes:
1. Need to make sure there is enough sun otherwise it's all a waste and will drain the battery FASTER
2. Use a charge controller
3. Use a fuse tap

To prep, I'd need to find:
- Best fuse spot to use
- A good spot to connect a ground wire near the fuse block

So wiring would go like this:

Inside the car Fuse Panel -> Always on fuse (find with multimeter)
Insert fuse tap to split power
10amp fuse for this part of the tap (original fuse for original fused connection)
Cut the solar extension kit's SAE 2-pin extension cable and wire positive to the fuse tap and negative to the car ground so one end goes to fuse tap the other end has an SAE 2-pin adapter on it
Possibly: Put a normally open 12V relay or Voltage Sensitive Relay in line to disconnect charge controller unless panel gets power. This would then be wired to the universal hub
Connect SAE 2-pin to the charge controller's battery side
Connect the SAE 2-pin charge controller's solar side to the solar panel universal connector hub (skip this if only using 1 panel and no relay/VSR from step 5
Connect solar panel to universal hub
Important: Technically, if you're using more than 1 solar panel you should install a 1-way diode between the solar panel and the hub. This would stop backflow of power into the other solar panels which could cause a fire if one is faulty and the other(s) are cranking out a lot of power

Do this at your own risk, these are just my ideas.

Fuse tap:

image.png.e1c274cde87a70c520d8f878b98b879d.png