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mrjoshida
Samba Member
Joined: September 28, 2018
Posts: 7
Location: Seattle, WA
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 Posted: Thu Mar 20, 2025 12:21 pm Post subject: Switchable fuse #3 mod |
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While my long term plan is to install a proper house battery, I'm currently getting by with a portable powerstation an Anker Solix C1000. In the meantime I'm trying to figure out who best to run my lights and radio off the power station.
It seems like I should be able to do the fuse #3 mod off of the power station's 12v outlet, but I'd rather not open up the fuse box and swap the fuse for a cable every time I want to use the power station. Would it make sense to wire as power connector up to a dpdt switch that sits between the two legs of the fuse #3 connector? Has anyone rigged up such nonsense before? |
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jimf909
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Joined: April 03, 2014
Posts: 8168
Location: WA/ID
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| Posted: Thu Mar 20, 2025 12:48 pm Post subject: Re: Switchable fuse #3 mod |
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Every sort of nonsense has been rigged in these vans. 
A switch to select stater battery or power station would certainly do what you need it to do.
However, in the future, when you install your house battery to run the #3 circuit you'll wire it to the fused side of the circuit and add a fuse in the house battery circuit to protect the wiring.
If you do that now you'll avoid rewiring in the future. Instead of a switch, you'll need to pull the fuse to power the accessories off of the power station and reinsert it to power them off of the starter battery.
It's a small choice in terms of time and changes but doing the latter will minimize impact to the stock wiring.
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- Jim
| Butcher wrote: |
| This is the main fault with DIY'ers, they get together on these forums and pat themselves on their backs spreading bad information. |
Guilty as charged.
Current: 1990 Westy Camper - Bostig RG4, 2wd, manual trans w/Peloquin, NAHT high-top, 280 ah LFP battery, 160 watts solar, Flash Silver, seam rust, bondo, etc., etc.
Past: 1985 Westy Camper - 1.9 wbx, 2wd, manual trans, Merian Brown, (sold after 17 years to Northwesty who converted it to a Syncro).
Last edited by jimf909 on Thu Mar 20, 2025 12:50 pm; edited 1 time in total |
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Crooked Designer
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Joined: March 22, 2018
Posts: 576
Location: Chicago, IL
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| Posted: Thu Mar 20, 2025 12:49 pm Post subject: Re: Switchable fuse #3 mod |
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So you want to have your lights and radio (and maybe cigarette lighter, etc..) run off the portable power station sometimes? and off the house battery other times?
Any reason to install aux battery now? seems like a lot of work to wire the power station as a temporary measure. Lots of simple setups for aux battery.
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'85 Westy full camper, Subaru 2.5L, 5 speed SubiGears + 5speedbus shifter kit |
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GoEverywhere
Samba Member
Joined: December 13, 2020
Posts: 901
Location: Portland, OR
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| Posted: Thu Mar 20, 2025 3:39 pm Post subject: Re: Switchable fuse #3 mod |
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I just wired a couple of diodes into my system. If the key is on that feeds the radio and such from the engine side, and if the main breaker for my house battery is on it feeds it from that side.
No switch to forget, or cables to swap. Everything happens automatically. |
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rustyCamper
Samba Member
Joined: December 13, 2023
Posts: 55
Location: CA
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| Posted: Thu Mar 20, 2025 11:47 pm Post subject: Re: Switchable fuse #3 mod |
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| GoEverywhere wrote: |
I just wired a couple of diodes into my system. If the key is on that feeds the radio and such from the engine side, and if the main breaker for my house battery is on it feeds it from that side.
No switch to forget, or cables to swap. Everything happens automatically. |
Can you please draw an electrical diagram of this? I would love to wire up something like that but don’t understand exactly how it would work |
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GoEverywhere
Samba Member
Joined: December 13, 2020
Posts: 901
Location: Portland, OR
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| Posted: Fri Mar 21, 2025 8:24 am Post subject: Re: Switchable fuse #3 mod |
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| rustyCamper wrote: |
| GoEverywhere wrote: |
I just wired a couple of diodes into my system. If the key is on that feeds the radio and such from the engine side, and if the main breaker for my house battery is on it feeds it from that side.
No switch to forget, or cables to swap. Everything happens automatically. |
Can you please draw an electrical diagram of this? I would love to wire up something like that but don’t understand exactly how it would work |
Its very simple, diodes act essentially as one way valves. You use them to allow power in, but not to feed back to the other side of the system like this:
That way if EITHER side has power it'll feed the loads. I didn't put it in the diagram, but those should be switched as well... |
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Altoona
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Joined: November 14, 2011
Posts: 590
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| Posted: Fri Mar 21, 2025 10:30 am Post subject: Re: Switchable fuse #3 mod |
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| GoEverywhere wrote: |
I just wired a couple of diodes into my system. If the key is on that feeds the radio and such from the engine side, and if the main breaker for my house battery is on it feeds it from that side.
No switch to forget, or cables to swap. Everything happens automatically. |
Curious as to what the benefits are to this set up vs. just wiring it only to the house battery. When the car is running the engine charges the house battery (presumably) which is essentially the same thing, no? |
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GoEverywhere
Samba Member
Joined: December 13, 2020
Posts: 901
Location: Portland, OR
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| Posted: Fri Mar 21, 2025 10:34 am Post subject: Re: Switchable fuse #3 mod |
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| Altoona wrote: |
| GoEverywhere wrote: |
I just wired a couple of diodes into my system. If the key is on that feeds the radio and such from the engine side, and if the main breaker for my house battery is on it feeds it from that side.
No switch to forget, or cables to swap. Everything happens automatically. |
Curious as to what the benefits are to this set up vs. just wiring it only to the house battery. When the car is running the engine charges the house battery (presumably) which is essentially the same thing, no? |
Yes, basically. For my setup the biggest thing is I have a master switch for my house side. Everything on that side shuts off with that switch. I didn't want to lose my radio when my house breaker was off so I wanted to be able to feed it from either side. If you're not wired that way this setup makes less sense for sure. It also allows my radio to shut off with the ignition switch when my house setup is off instead of having to shut off the ignition AND the house breaker to kill the radio.
Its also useful for people who don't wire their setup for alternator charging. Not everyone goes that route for some reason. |
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rustyCamper
Samba Member
Joined: December 13, 2023
Posts: 55
Location: CA
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| Posted: Fri Mar 21, 2025 1:10 pm Post subject: Re: Switchable fuse #3 mod |
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Thank you GoEverywhere for the diagram and explanation, that is really helpful for me understanding it.
I am thinking of doing something similar with fuse 3 so when I am driving and not charginging my house battery everything would run off the starter battery, but when I am not running the engine and camping I would like to run everything off the house battery. Similar to the original poster I was considering adding a switch for this.
One question I still have about the diode setup is that wouldn't your setup still allow current to be drawn from the starter battery when the engine is off? My concern is killing the starter battery from running the things off fuse 3 when the van is parked. |
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GoEverywhere
Samba Member
Joined: December 13, 2020
Posts: 901
Location: Portland, OR
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| Posted: Fri Mar 21, 2025 1:36 pm Post subject: Re: Switchable fuse #3 mod |
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| rustyCamper wrote: |
Thank you GoEverywhere for the diagram and explanation, that is really helpful for me understanding it.
I am thinking of doing something similar with fuse 3 so when I am driving and not charginging my house battery everything would run off the starter battery, but when I am not running the engine and camping I would like to run everything off the house battery. Similar to the original poster I was considering adding a switch for this.
One question I still have about the diode setup is that wouldn't your setup still allow current to be drawn from the starter battery when the engine is off? My concern is killing the starter battery from running the things off fuse 3 when the van is parked. |
Thats why I made mention of needing switched 12v. I forgot to put it in the diagram, but neither side of mine is going DIRECTLY to the battery. My engine side is key switched, and my house side is breaker switched. So the 12v side only works when my key is on.
Sorry the diagram misses that... Got it all done and posted it and then went "Whoops, forgot the switch!" |
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fxr
Samba Member
Joined: December 07, 2014
Posts: 2646
Location: Bay area CA
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| Posted: Fri Mar 21, 2025 2:11 pm Post subject: Re: Switchable fuse #3 mod |
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| rustyCamper wrote: |
I am thinking of doing something similar with fuse 3 so when I am driving and not charginging my house battery everything would run off the starter battery, |
Why would you not be charging the house battery when driving? That seems an odd situation to be in.
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1984 1.9l EJ22 Westy Wolfsburg Edition
Vespa GTS 300 |
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rustyCamper
Samba Member
Joined: December 13, 2023
Posts: 55
Location: CA
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| Posted: Fri Mar 21, 2025 2:32 pm Post subject: Re: Switchable fuse #3 mod |
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| GoEverywhere wrote: |
Thats why I made mention of needing switched 12v. I forgot to put it in the diagram, but neither side of mine is going DIRECTLY to the battery. My engine side is key switched, and my house side is breaker switched. So the 12v side only works when my key is on.
Sorry the diagram misses that... Got it all done and posted it and then went "Whoops, forgot the switch!" |
Oh that is really cool! I did a little digging to see if I could find out how to do that but I must not be searching for it properly. Would you mind sharing the parts or how your keyed switch works?
| fxr wrote: |
| Why would you not be charging the house battery when driving? That seems an odd situation to be in. |
I have a renogy DCDC 30amp charger that charges the house batter when driving, but I don't want my battery to be constantly topped up to 100% and I also found that even if the batter is 100% the DC DC charger draws 30 amps continuously from the alternator. To reduce the load on my alternator I have a shutoff switch. I basically only charge the battery when I am going camping but otherwise I do not connect the charger.
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GoEverywhere
Samba Member
Joined: December 13, 2020
Posts: 901
Location: Portland, OR
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| Posted: Fri Mar 21, 2025 2:36 pm Post subject: Re: Switchable fuse #3 mod |
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| rustyCamper wrote: |
| GoEverywhere wrote: |
Thats why I made mention of needing switched 12v. I forgot to put it in the diagram, but neither side of mine is going DIRECTLY to the battery. My engine side is key switched, and my house side is breaker switched. So the 12v side only works when my key is on.
Sorry the diagram misses that... Got it all done and posted it and then went "Whoops, forgot the switch!" |
Oh that is really cool! I did a little digging to see if I could find out how to do that but I must not be searching for it properly. Would you mind sharing the parts or how your keyed switch works?
| fxr wrote: |
| Why would you not be charging the house battery when driving? That seems an odd situation to be in. |
I have a renogy DCDC 30amp charger that charges the house batter when driving, but I don't want my battery to be constantly topped up to 100% and I also found that even if the batter is 100% the DC DC charger draws 30 amps continuously from the alternator. To reduce the load on my alternator I have a shutoff switch. I basically only charge the battery when I am going camping but otherwise I do not connect the charger. |
The keyed switch is just the ignition switch on the column. I run the 12v from the engine side from a 12v feed thats turned off by the ignition switch. |
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fxr
Samba Member
Joined: December 07, 2014
Posts: 2646
Location: Bay area CA
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| Posted: Fri Mar 21, 2025 3:45 pm Post subject: Re: Switchable fuse #3 mod |
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| rustyCamper wrote: |
| fxr wrote: |
| Why would you not be charging the house battery when driving? That seems an odd situation to be in. |
I have a renogy DCDC 30amp charger that charges the house batter when driving, but I don't want my battery to be constantly topped up to 100% and I also found that even if the batter is 100% the DC DC charger draws 30 amps continuously from the alternator. To reduce the load on my alternator I have a shutoff switch. I basically only charge the battery when I am going camping but otherwise I do not connect the charger. |
Understood - but the BMS in the battery must be faulty - ah, you must have an ordinary lead-acid battery, so no automatic shutoff like a LiFePO4 BMS would provide. But why then use a DC-DC charger. Just for solar?
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Jim Crowther
1984 1.9l EJ22 Westy Wolfsburg Edition
Vespa GTS 300 |
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Sjwillis
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Joined: April 23, 2014
Posts: 63
Location: New Jersey
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| Posted: Fri Jul 11, 2025 3:40 pm Post subject: Re: Switchable fuse #3 mod |
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Returning to @mrjoshida ‘s original post here: I’m already doing the aux battery wired to the positive of my dash cigarette lighter and it works great but am tired of running down my aux battery and having to replace it. Yes, this is my fault for running it down. I have kids, it’s hard to remember to turn the radio off sometimes when we’re camping etc.
anyway, if i wanted to run the radio, lighter, lights etc off of my jackery or other portable power, could I wire the 12volt connection out of the jackery to the red wire running up to my dash lighter? What would i do for a ground in this case?
Thanks for any help here.
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