Help me build an Aux battery system

[BCgee]

Vanagon Electric Gurus, I need your engineering brains and wisdom!

Recently went nuclear and put a hightop on the Syncro (kudos to @vanlab for the scary cutting and gluing assist!) and am now contemplating how best to wire and power for future electrical needs. Sadly electric is my weakness, give me carpentry or metalworking any day...

Here's the current hypo on what I'd like the ability to power through an Aux battery set-up:
-MaxxFan (anticipated regular use throughout the year)
-Portable fridge (sparing use, seasonally)
-Small interior lights (regular use)
-Couple USB and/or 3-prong outlets (regular use)
-Espar b4 heater (future project, seasonal use only and then regularly)

Additionally, I'd like to have the ability to plug in an external, portable solar array to help recharge during irregular longer travels (I have a bunch of GoalZero arrays presently). FWIW because of Montana's harsh climate and general daily use of the van, not contemplating a permanent set-up. How would you design this type of plug-in function??

Likewise, it appears there's a relatively straight-forward manner to wire the aux system to the house battery/alternator so that, during van operation, re-charge happens automatically, and upon engine being off, aux system automatically turns "on." Would appreciate beta on the appropriate relay etc to build/buy for achieving this functionality!

In terms of location, ideally I could situate the new auxiliary battery system under the drivers' seat (presently empty). If necessary I could relocate to under the rear z-bed bench seat alongside heating elements and the subaru ECU. Not a deal breaker. Have a Weekender interior so stowing battery somewhere out of the way is key (we use the open bay a good bit for hauling family stuff and dogs).

My very rough understanding of amp hours, cycling, and anticipated draw from the above uses suggests I should be shooting for a system with around 200 amp hours capacity, ideally from one big battery (as opposed to two or more piggybacked). I have a local Costco where various golf cart batteries appear at steep discounts, but can easily be convinced to consider other options too.

Think that covers my goals, and probably exposes some holes in my logic too... What am I leaving out, and how should I begin designing this system?

Suggestions on type of batteries, relays, location(s), wiring, etc would be extremely helpful and greatly appreciated!! Photo of new hightop to spread the stoke...

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1987 SVX Syncro Hightop

[shagginwagon83]

I'd do the 2x golf cart 200ah setup you speak of, batteries under the bench seat.

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Brandon
"Jo Ann" - '83.5 Westfalia EJ22e w/Peloquin
Instagram @joannthevan

[Jd56]

Just curious why is it better to run the solar charger into the fuse panel and not just into the battery?

[shagginwagon83]

[Jd56]

It’s just my broken mind. I think power to fuse panel to device needing power not going to device holding power. Get what I mean.

[shagginwagon83]

[pnwkayaker]

Thanks to BCgee for starting this post, I'm interested in this topic since I want to redo/rebuild my aux battery system to be simpler (it's currently a hack that I can barely understand)

Thanks shagginwagon83 for the electrical diagram, couple of questions in the same vein (hopefully the OP will find them useful):

1 - why are you plugging the solar charger to the fuse panel, but you're plugging the shore power directly to the battery? Wouldn't it also make sense to go through the fuse?

2 - similar question, why is the output of the Cytrix-ct (I assume is some type of Yandina/Surepower combiner) wired directly to the aux battery with a 60 amp fuse in between? What's the fuse trying to prevent?

3 - it seems that only the "live" wire is connected to the fuse (and carried throughout the system), but how/where are you connecting all the different ground connectors from the different devices (Propex/fridge/lights, etc)? Do you just connect them to a ground block (any block) that's screwed to the chassis, or do you want to connect them all to the ground connector of the battery?

4 - Do you have any pictures of the wiring itself to the fuses and distribution blocks (perhaps comparing them against our diagram)? This is related to the above question probably.

5 - Lastly, what do you mean by "use circuit breaker instead of fuses for future diagnosis systems"? How is that different/better? Will that replace the complete fuse panel labelled "Accessories" in your digram or just the other intermediate fuses?''

Thanks in advance!
_________________
87 Syncro Westy EJ25 ("Tardis")

Seattle Meetup at Marymoor (link)
A collection of Simple Useful Mods (SUM) (link)

[SSWesty]

Need a little more detail on your use case scenarios to help figure out amp hours needed and the replenishment of said amp hours. The frig and heater will be the big consumer of amp hours.

So here are some questions about usage:
-what type of frig, compressor frig like an engel, ARB, etc. or thermal electric?
-what do you mean by sparing using the frig? Either it's on cooling food or it's not and just used for dry storage. Does sparing mean you will only use it on a smaller percentage of trips or only need it for a short duration on a trip like day 1 but not day 2?
-as for the heater, what season are we talking about here, demand in winter will be high if you are winter campers and summer time demand is typically pretty light. Do you guys like sit inside the van all day or are you out and about. If you need heat all day because you are writing a book in your van or watching for some rare animal to walk by you need more amp hours than if you just need it in the evening and morning.
-do you guys like to go and park for a few days at a time without running the engine or do you typically move around everyday. For example we may go to Yellowstone for a week but we go somewhere everyday within the park. So our battery is charged daily.

How did you get to 200 amp hours, is that usable capacity meaning with everything you need to run you calculated you need 200 amp hours? Or is your usable capacity 100 amp hours and you need 200 total amp hours so you don't run the batteries below 50%?

[shagginwagon83]

[Jd56]

Probably dumb question what’s the silver finned thing just above the fuse block.

[shagginwagon83]

Not a dumb question at all. I'm sure it has confused a lot of people.

It is a buck transformer. It takes 12v DC to 19V DC. It was a failed project that was intended to charge my laptop more efficiently.

If you have any other questions let us know!
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Brandon
"Jo Ann" - '83.5 Westfalia EJ22e w/Peloquin
Instagram @joannthevan

[BCgee]

SSWesty:

Arb fridge, “sparing use” means only during summer, and infrequently. Van is a kid commuter that also does family trips when the Wife gives a green light.

The planned Espar B4 heater use will be heavy during winter. I’m in SW Montana with regular stints of negative temps where heater will be used if not daily, regularly during 5+ months. We also ski and ice climb, so will use heater for sitting at trailheads and occasional overnighters.

Lastly, the 200ah figure is gleaned from previous research of other van setups and logistics. Not bound to it; rather, more constrained by sheer size and storage than anything else!
_________________
1987 SVX Syncro Hightop

[Jd56]

I am acquiring parts and working on details to build a small aux battery setup for a little extra power. So thanks for answering question so quick. What kind of battery’s are you using in your setup.

[Jd56]

I am acquiring parts and working on details to build a small aux battery setup for a little extra power. So thanks for answering question so quick. What kind of battery’s are you using in your setup.

[michaelbteam]

Good conversation. I am considering creating an aux power system using the Goal Zero Yeti 1400 Lithium and solar panels. Yes, this is expensive! Besides that, does anyone have input on the practicality of this idea? Thanks.

[SSWesty]

BCgee, that's helpful input about usage. The one piece missing is in the summer when you camp is how often you stay in one place without running the engine. Do you park for two nights without moving or is it typically overnight trips?

For your winter scenarios if you are just doing overnight trips it may be feasible to use one battery in the 110 amp hour range. Here are some estimated amp hour usages:
Looks like the Espar B4 is around 3.3 amps running.
Winter Day trip
-Arrive at trail head, run heater for 2 hours while gearing up and waiting for friends. 3.3 amps x 2 hours x 70% running time = ~4.6 amp hours
-Finish climb and hang out in van for 4 hours before heading home. 3.3 amps x 4 hours x 70% running time = ~9.25
-Charge a cell phone/tablet = ~2 amp hours
-2 hours of interior lights, with LEDs you get a lot of light out of 1 amp. 2 hours x 1 amp = 2 amp hours
-No frig = 0 amp hours
-Total day trip amp hour usage = 17.85 amp hours, this could be supported by a 40-50 amp hour battery under the drivers seat. The running time of the heater is the big variable which will be driven by how often the slider is opened, hightop insulation and outside temp. With good insulation and keeping the doors closed the heater may only need to run 50% of the time. So maybe in runs for 10 minutes then is off for 10 minutes before it cycles back on.

Winter Overnight trip
-Arrive campsite at Noon, run heater for 1 hour while preparing to go out for an excursion. 3.3 amps x 1 hour x 70% running time = 2.3 amp hours
-Return to van at 5:00pm and run heater at 70% until 10pm, 3.3 amps x 5 hours x 70 percent running time = 11.6 amp hours
-Lights from 5 to 10pm and you only run .75 amps worth of LED lights. .75 amps x 5 hours = 3.75 amp hours
-Charge a device = 2 amp hours
-10pm to 7am run heater at a lower temp so running time is down to 50%. 3.3 amps x 9 hours x 50% running time = 14.9 amp hours
-7am to 11am heater temp goes back up and running now 70% of the time. 3.3 amps x 4 hours x 70% = 9.25 amp hours
-7am to 9am running full lights of 1 amp. 1 amp x 2 hours = 2 amps
-11am start engine and head to the next adventure
Total Overnight trip amp hour usage = 45.8 amps which could be managed by a 100 amp battery like a deep cycle group 27 or a really good group 24 battery.

In the summer time it's probably about 30-35 amp hours per day based on 25 for the ARB and 5-10 amp hours for lights and a little heat in the evening and morning. Sometimes we only run our heater for 30 minutes on a summer morning to take the chill off. There is more daylight so you don't need much for lights.

It would be good to get the real draw on the heater when it is past it's start up phase. Some heaters draw more amps right at startup then drop down a bit, so 3.3 amps may be the startup amps and not the continuous running amps. Also the 3.3amp number is what I quickly pulled from the web which may not match your heater.

Hopefully you can see how I pieced together amp hour usage over the course of a day and it will give you enough to mock up a scenario that is closer to what you would actually do. What will get you to chasing golf cart batteries will be the spending the second or third night without running the engine or recharging by some other means. Or some other power hungry device.

I winter camp and I only have a 40 amp hour battery under the drivers seat. My amp loads aren't as high as what I mocked up above so I can do an overnight easily. Night two is where my battery gets stretched. If I get 4 years out of a $125 battery that is $31.25 per year. However if I abuse my battery on multi-night winter camping trips and only get 3 years out of my battery that would be $41.67 per year. So abusing my battery will cost me an extra $10.52 per year in battery expenses over the long haul. I think of that has a pretty small price to pay vs. trading space for a larger battery under the sink or under the rear bench seat.

[DuncanS]

SSWesty's post is the way to begin the design--Or you can just go with the 200 ah and see how it all goes. I recommend you look at the topic:
https://www.thesamba.com/vw/forum/viewtopic.php?t=717409
This is currently being run with additions and good info. Shagginwagon has good inputs and has done a nice clean instal.

Duncan

[BCgee]

Thank you Duncan, ShagginWaggon and SSWesty: good advice and tips so far.

On a very basic level; how would one design the hook-up for plugging external portable solar into the aux battery system? While Shaggin’s diagram is helpful for my logical brain, I don’t have enough knowledge of electric or components to design a hook-up, (e.g. whether it’s a simple cord that’s stowed during travels and brought/run through a window or door or something similar).

To further complicate the external portable solar hook up question, does the technology/hook-up to charge the aux battery change depending on whether one uses direct panels with cables to some sort of relay to the aux vs. if one has a GoalZero Yeti style generator? Can a GoalZero generator be used to recharge an aux battery system (seems somewhat redundant but I already have a GZ setup but it’s not van integrated 🤔)

Please keep the suggestions and advice flowing!!!
_________________
1987 SVX Syncro Hightop

[fishgo]

[quote="shagginwagon83"]

[a2wolfsburggli]