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Username Post: Would like to set up accessory battery        (Topic#351237)
Posts: 150

Reg: 03-20-18
05-22-18 06:08 PM - Post#2734676    

Livin in a van. As homeless.

without breaking budget. I want to set up an accessory battery, to power lights and fans and laptop, while engine is off and not drain the primary battery.

need to keep van cool for cat, who lives with me. The side windows do not open to let heat out they trap it in, thus fans to push and suck heat.

primary battery is quick charge while the accessory battery is deep cycle.

I been reading around and I get the impression that you can use a standard alternator( I have 105 amp with no AC.) to charge a quick charge and deep cycle. specs for Van only needs 85 amp for my current setup.

This set up is for off grid use only.

I was looking at a sealed 35AH or 53AH(dyslexic) deep cycle for time being, it would fit under passenger seat

right now I would be using 12v sockets and or direct wiring to draw power.

I need to find a DC to DC converter for my laptop though.

VSR voltage sensitive relay is one of the items I was looking at but not sure if there is anything else I should get like a idiot switch for when I need to work on the van for example. For safety in case the VSR fails to disengage the accessory?

I am trying to keep the cost down the battery is going to run me 86$ alone.

The fans are a camper vent fan and a low power 10 inch dc portable fan with select high low speeds.

The primary wiring will go under the floor and come up under passenger seat. I don't know if I should run it along the steel bumper and then back to the passanger seat. (that is the path for the battery to starter wire.)

I may add a power converter at a later time but am reluctant due to power loss in the changing from DC to AC. especially since using a smaller deep cycle.

I also don't want a system that takes forever to charge the accessory battery or I will break my budget just charging the battery and repairing the engine and everything else.

Anyone else done this and how did you set it up and what was your experience?

when asking Questions its related to van I own: 1987 GMC 3/4 ton G2500 vandura, V6, No AC, standard length. 3speed trans(no overdrive).


100 CHEVY 
Dedicated Member
Posts: 6499
Loc: Helena,Missippi,U.S.A.
Reg: 12-09-04
05-23-18 06:25 AM - Post#2734729    
    In response to VanLife

I would'nt store/charge a battery inside the passenger area of the van.They emit dangerous fumes when charging and when it goes bad.
Alternators are designed to keep a battery charged.Not too good for charging dead batteries.
I use a battery isolator.It chooses which battery is lowest and directs the charge to that battery.Otherwise the batteries are not connected,so you don't discharge the engine battery,only the house battery.
Maybe consider a small solar panel for the roof?

"You gonna leave it like that?

Posts: 13

Reg: 05-23-17
05-23-18 12:03 PM - Post#2734751    
    In response to VanLife

Have you considered insulation and natural ventilation? It might be possible to get enough air flow with a couple of roof vents and some vents low down at the floor level to make a fan unnecessary. An inch of insulation throughout the interior might keep the temperature down inside enough for the natural ventilation to work. Covering the windshield and windows will keep the Sun's heat out.

Roof ventilators could be picked up cheap in an RV graveyard along with insulation. You might get lucky and find all the electrical parts for auxiliary batteries and solar power. Univer...

Finding shade in the middle of the afternoon will keep the cat happy.

Posts: 150

Reg: 03-20-18
05-23-18 02:30 PM - Post#2734765    
    In response to 100 CHEVY

sealed batteries don't discharge gasses in high enough quantity to be health hazard. they are designed to use inside closed spaces. (as long as they are not over charged) which would be extremely hard to do on a 15 volt system.

when asking Questions its related to van I own: 1987 GMC 3/4 ton G2500 vandura, V6, No AC, standard length. 3speed trans(no overdrive).

Edited by VanLife on 05-23-18 02:59 PM. Reason for edit: No reason given.

Posts: 150

Reg: 03-20-18
05-23-18 02:38 PM - Post#2734766    
    In response to Lorence

already have that. problem is that the roof gets to hot and refuses to allow heat to pass out of the roof vent. Thus have to have a fan push it out the vent. It works I hooked it up today and noticed immediate difference.

I just need to add a speed control so the fan not running full bat out of hell it drains my battery so dang fast. It ate 40% of 12AH battery in 30-40 minutes.

Then also run cab fan.

My side windows do not open trapping heat and can not insulate windows or risk breaking them from heat stress. Using heat blocking film not possible because need radiant heat in winter and can not afford to constantly put tint on and removing it.

the amount of solar panel I would need exceeds roof space also Its a PAIN to keep working with all the rattling and crud and such. This is coming from people who have done it its NOT ready for vehicle off grid application.

It would be a nightmare to deal with in winter as well.

when asking Questions its related to van I own: 1987 GMC 3/4 ton G2500 vandura, V6, No AC, standard length. 3speed trans(no overdrive).

Edited by VanLife on 05-23-18 02:43 PM. Reason for edit: No reason given.

Posts: 150

Reg: 03-20-18
05-23-18 03:03 PM - Post#2734768    
    In response to Lorence

Shade moves and it can heat up quickly with the wrong setup like side windows not opening.

I did that where I stayed with the van its inadequate to leave the van alone for the day.

I don't have access to the side pop out windows. that goes directly behind the driver seat and the side panel door.

and the long back side windows don't have vents. like a conversion.

when asking Questions its related to van I own: 1987 GMC 3/4 ton G2500 vandura, V6, No AC, standard length. 3speed trans(no overdrive).

Posts: 13

Reg: 05-23-17
05-23-18 10:29 PM - Post#2734800    
    In response to VanLife

Natural convection is a slow process but it works when air is free to move into a space as well as rising up and out through the roof vent.

If you only have a vent in the ceiling not much air will flow through it because the escaping air needs to be replaced inside the van as fast as it moves out of the vent.

Think of trying to suck air out of a bottle. You can't because all you do is create a partial vacuum. If you make a big hole in the bottom of the bottle air moves freely through it.

In a closed van with only a roof vent not much outside air can get in. As a result not much air can get out. You would need vents with the same opening size of the roof vents in the floor or in the side of the van close to the floor. This would allow fresh outside air to get in to the van as fast as it escape through the roof vent.

The fan works because it provides the power needed to suck air into the van through whatever openings exist in the body. If you opened a window with the fan running I'll bet the exhaust airflow would increase quite a bit because the fan is not working to draw air in. It only needs to work to push air out.

That's why they put cold air vents in a house with a forced air heating system. As warm air is pushed into a room through the hot air vent, cool air is drawn out of the room through the cold air vent. Without the cold air vent the hot air would slightly pressurize the room enough to prevent more of the hot air from getting into the room.

So even if natural convection would not be adequate on it's own, fresh air vents letting outside air in would allow the fan to move air more efficiently allowing you to run the fan at a slower speed.

If you were to use insulation you only insulate inside the metal roof and sides, not the windows. All you heed to do with the windows is to block the sun from coming through. A piece of cardboard will do that. Go into any parking lot in the summer and you will see those reflective panels placed inside car windshields.

You will appreciate the insulation in the winter as well. Just as it keeps heat in during the winter it keeps heat out in the summer.

Whatever you do, you got to do right for your cat. I have had cats and dogs all my life. My advice is for your cats benefit more so than yours.

Dave in VA 
Posts: 267
Dave in VA
Age: 69
Loc: SW Virginia, USA
Reg: 03-11-18
05-27-18 06:52 AM - Post#2735034    
    In response to VanLife

Deep cycle batteries aren't near as good as golf cart batteries are, amp hour wise...

"Knowledge is Good" -- Emil Faber

U S Navy MM2 1970-75 USS Canisteo AO-99, USS Miller DE-1091 (The Champagne of Ships)

1950 Styleline Deluxe 2dr, mostly stock, driver to me 3/18
2016 Equinox LTZ
2017 Silverado LTZ 6.2


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