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House battery for accessories

Posted By: 94chevyG20

House battery for accessories - March 29th 2018 6:06 am

I was looking through the van trying to figure out how I could use a house battery to power the vans accessories. The van has a intellitec battery guard and from what I read this is used to cut power so the starting battery doesn't go dead. Would it be possible to run a line from the house battery to the intellitic and power the accessories that way? Currently there is a hot wire from the starting battery to the intellitic and it appears the rest of the wires on the intellitic go to the inside of the van.
Posted By: wrcsixeight

Re: House battery for accessories - March 29th 2018 6:27 pm

Not familiar with the intelltec system, but I am not really fond of low voltage cut offs. They have a small parasitic load, and if/when they do disconnect, based on voltage, the battery capacity remaining at that voltage/state of charge still might not be enough to crank the starter depending on the health of the battery.

There are a thousand products and methods for having an additional battery for house loads and not draining engine battery. I think in many cases where the owners think this is necessary, they could get away with simply carrying a fully charged jumper pack. When their engine battery dies from repetitive deep cycling, replace it with the biggest marine battery which will fit, as these are more tolerant of deeper cycles, even though the internals are closer to a starting battery than a true deep cycle battery, despite the sticker's claims.

All lead acid batteries always want to be kept fully charged, and cool. Due to the voltage regulation imposed upon alternator, the vehicle's charging system will almost never return a discharged battery to 100% full.

So those that regularly use their battery with the engine off, should have a plug in charging source applied regularly, and promptly, after any significant discharge.

The alternator might be capable of 130 amps when cold and spinning fast, but the battery dictates how much amperage it wants at the voltage reaching the battery terminals. Only when well discharged can a battery accept large amperages.

It basically takes 4 hours minimum to get a battery from 80% charged to 100% charged, it ideal voltages. Getting to 80% charged from 50% or less can be done quickly with high amperage, but the source has to be seeking and holding voltages in the mid 14's.

No vehicle allows ideal voltages for prompt and full battery charging.

Except mine:) I have modified my voltage regulation and can choose whatever voltage I want at the spin of a dial on my dashboard. I use only one battery, a group 27 Northstar AGM, for house and engine loads, though I can carry 2 addtional group 27's. It is 53 months old and has ~750 deep cycles on it.
Posted By: 94chevyG20

Re: House battery for accessories - March 30th 2018 12:18 am

Was trying to find an easy way to hook up accessory lighting tv etc on my two agm batteries that I have. I already have an isolator just need to take these things out of my old van.
Posted By: wrcsixeight

Re: House battery for accessories - March 30th 2018 6:23 pm

Get a new fuse block and a bussbar such as these and hook all circuits you want on the house battery, to the house battery.;psc=1&refRID=KX0FD1F72GDS3M5JV6HD;psc=1&refRID=WBX1SM281RGYJZ0D8RTQ

Note thatthe house battery should be fused to protect the cable running to isolator/alternator. ABYC code is within 7 inches of battery terminal.

I like these blue seas fuse which ft to battery posts, if the extra height clearance is available;psc=1&refRID=WS3N2QPGMDVNG5PXGHDE
Posted By: 94chevyG20

Re: House battery for accessories - March 31st 2018 12:11 am

I have the second fuseblock that you linked in my other van. Are the fuses for the house accessories somewhere inside the van ? I think I'll have to buy a repair manual or something to find where they all are.
Posted By: frscke1

Re: House battery for accessories - March 31st 2018 12:23 am

Behind the driver seat is a wood panel on the wall is where alot of the conversion co put the fuse box so I have found tearing into them in the yard.
Posted By: 94chevyG20

Re: House battery for accessories - April 03rd 2018 2:11 am

So here is that intellitic device. Would I be able to attach the positive line from the house batteries to where the positive line is going to the starting battery right now and power house accessories that way?

Here is fuse panel that I found behind the drivers seat. How exactly would I go about wiring that to my house batteries?

Thanks for help.

Attached picture IMG_20180402_184618.jpg
Attached picture IMG_20180402_184948.jpg
Posted By: wrcsixeight

Re: House battery for accessories - April 04th 2018 3:10 am

If that were a simple 'DUMB' solenoid of the two fatter studs one would goto the Engine battery, and the other would goto the House battery. The two smaller connectors would activate the electromagnet which would open or close the contacts connecting or separating the two larger wires.

One of the smaller wires would be ground, one would be 12v switched by the ignition.

I am not sure how that intellitec product works.

The secondary fuse box in the back are kind of PITA's as some wires are always live, and some are only switched on with the ignition. YOu will need to spend some time with a digital multimeter, determine which circuits are which by pulling the fuses and turning on accessories on and off. It will be a bit of a puzzle, to figure out which circuits you want to move to the house battery.

I recently just moved only the rear interior lighting on a 95 g20 conversion van to a new fuse block I installed and it elicited quite a few curses.

Posted By: islander

Re: House battery for accessories - July 09th 2018 5:31 pm

I'm a little late to this thread, but I was an automation tech for years and have spent quite a bit of time rewiring my old dodge. Here is a rough diagram of how you're going to want to wire the second battery:

[Linked Image]

The negetive wire comes from your car battery, goes to the intellec, then comes out the other side and goes to your second battery. the positive wire should be connected directly.

Then, as others described, one of the two little terminals goes to ground and the other goes to accessory power - something that is only energized when the car is running. With this system, both batteries will be in use while the car is operational which allows the alternator to charge up both batteries. When the van is off, only your secondary battery will be used to run the accessories.

You'll probably want to use a fairly heavy gauge wire for the main power leads to your secondary battery. You'll also want to make sure that the two batteries you use are fairly close in specification.

The main issue with a system like this is that the batteries can be come un-balanced, which can put strain on your existing electrical system. This is because your alternator is designed to vary the output depending on how much power is needed. If your existing battery is fully charged and you aren't running much in terms of accessories, the output is low. But when your battery is quite drained, the voltage can get as high as 14.5 volts in order to give the battery a full and complete charge.

When you have two batteries wired up like this, the alternator is measuring both of them as if they were a single battery. If you've been running the stereo all night and your house battery is quite drained, the alternator will try to charge it up quickly. But this can cause an overcharge condition with your main battery and drastically reduce it's expected life.

If the wires you use are too small, or the capacity of the second battery you install is drastically different from the one used to start your van, this can also cause huge problems.
Posted By: wrcsixeight

Re: House battery for accessories - July 09th 2018 6:55 pm

You are giving the alternator's voltage regulator, which controls the output of the alternator, far too much credit in terms of what it is trying to do, and how it decides.

Perhaps a few modern vehicles measure the field current sent to alternator to control how much amperage it makes to seek the desired voltage, and a few might also have have a Hall effect sensor on a battery cable seeing just how mucch amperage is entering or exiting the battery, ,but no vehicle previous to the mid 2000s consider the variables into how long to seek and maintain a specific voltage.

Having the engine battery and house battery being similar make model and design is also not accurate.

With the engine running each battery will acccept whatever amput of amperage it wants at the voltage reaching the battery terminals. The depleted house battery at 13.8v might accept 12 amps,m the fully charged startng battery might accept 0.6 amps. They take what they want at the voltage allowed by the vehicle and the wiring to and from the batteries from alternator, incvluding the usually well undersized ground path.

What one does NOT want to occur is leaving the dissimilar batteries in parallel( connected together) with NO charging source present.

Voltage is electrical pressure and batteries accept whatever they want at the pressure reaching the battery terminals, upto the maximum output of the charging source.

Problem with house batteries and the alternator as the only charging source is it takes no less than 3.5 hours, at 14.5 volts, to get an 80% charged battery to 100%. Yet one can discharge a 100% charged battery to 80% in a few minutes of blasting their well amplified stereo.

Since No vehicle allows 14.5v for that amount of time, the actual time reqired to return a depleted battery to full takes mucch much longer, and every human out there seems to think that the alternator is somehow able to defy physics and instantly and fully charge the battery.

When a lead acid battery lives less than fully charged its lifespan is dramatically reduced. If one wants respectable lifespan from a house battery it must be regularly fully charged or be allowed to live at a high average state of charge.

If a House battery is deeply cycled eacch night then recharging it to 98% is good, ,but only half as good as recharging to a true 100%, and this last 2% can require 2 more hours being held at 14.5v or 10 more hours at 13.8v.

No one is going to drive that long just to get a 98% charged battery to 100%, and manipulating the vehicles voltage to seek and hold high 14v range is not easy to accomplish. Most will drop to the 13.8v range once hot, no matter if the house battery is still well drained andable to accept huge amperages. In fact most of this voltage dropping is related to the heat the alternator, or voltage regulator if not within the alternator, is subjected to, and the more output the alternator makes the hotter it gets and lowers the system voltage sought. So it is more likely the depleted house battery asking for everything the alternator can make will have it lower the voltage sought and greatly slow the actual recharging of the depleted house battery.

The care and feeding of lead acid batteries is grossly misunderstood by most, and there is much incorrect folklore out there concerning this topic.

Having a house battery charged by the alternator when driving is not rocket science, but when one cannot control the voltage sought by the alternator, then the house battery is at the whim of the voltage reaching its battery terminals, and 99% of the time this is not ideal for quickly nor fully recharging of the battery.

When one gets tired of trying to warranty prematurely sulfated house batteries, or has that warranty denied, one then learns how to better treat the battery so it does not prematurely fail.

This basically requires alternate charging sources applied to take the battery from whatever the alternator left it at when the engine was shut off, to much closer to 100%. Solar or a plug in charger.

Also, most 'smart' chargers these days are also poor at actually fully charging a well depleted battery. These too, for fear of overcharging a slightly depleted battery, will not allow the mid 14 volt range to be held for long enough. they will drop to float/maintenance voltages well before the battery is full, and flash the green light.

Most smart chargers will drop out of the 14.5v range to the 13.2 to 13.6v range, in the 92 to 95% charged range. If the battery is sulfated, then it really really wanted the 100% recharge, and a sulfated battery needs significantly more time than a healthy battery to get from 95% to 100% state of charge.

But Lead acid batteries are only rented. The length of the rental contract is directly related to how well they are recharged. How well they are recharged is determined by the voltage the charging source is seeking, and how long it holds that higher voltage. Even the best marketed smart chargers, get this wrong, and this is verifiable with a hydrometer on a flooded battery with removable caps, or wqith an ammeter on an AGM battery when it is held at 14.5ish volts.

Almost NO vehicle out there will seek and hold the mid 14 volt range when the battery is less than 100% fully charged. Except mine, as I have bypassed the insane voltage regulator inside my engine computer, and hooked up an external adjustable unit with a dial on my dashboard, next to my digital ammeters and voltmeters, and I choose 14.7v whenever the battery is not fully charged, and 13.6v when it is. Pretty rare that i dial it down to 13.6v, and I have 200 watts of solar on the roof and a plug in charging source capable of 40 amps output at anywhere from 13.12 to 19.23volts.

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