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auxiliary batteries

Posted By: 1phill

auxiliary batteries - September 09th 2010 1:27 pm

id like to have 2 batteries for a rear sound system
that operate independently for the starting battery
anyone have info and/or advise on this precedure
Posted By: relaxedvanner

Re: auxiliary batteries - October 09th 2010 6:16 pm

I know you would need an isolator and have the batteries in a sealed box vented to the outside to exhaust fumes while charging. You also require heavy gauge wire to do so . Hopefully someone with more knowledge will point you to in the right direction or a previous post that will explain more than i can.
Posted By: Starlord

Re: auxiliary batteries - October 10th 2010 2:30 am

One of the better ways is to use a manual Isolator. You can get them at a automotive stereo shop. It looks just like the old solenoids in cars except bigger. Has a hot wire in from battery, a ground wire, a remote go wire and a hot out to the batteries. Keeps the rear batteries from draining the main batteries and yet lets them charge when vehicle is running. You don't need to vent them if: A. You use Optima type batteries (I run two of the blue top marine style) or B. You get a couple of the dry cell from a automotive stereo shop. Make sure to run HEAVY duty fuses (such as the 150 amp type fuses you get at a stereo shop) at both points where you come off the battery and where the battery wire goes to the two auxilary batteries. I keep the Optimas under the rear couch/bed and that seems to work well. I used the automatic isolators like you can get at a rv shop or some auto parts stores and find that I like the manual one better (don't let the word manual through you, you don't have to do anything). Hope this helps you.
Posted By: wrcsixeight

Re: auxiliary batteries - October 10th 2010 3:57 am

The easiest way to do it is by getting some AGM batteries. Optima's are AGM batteries. Optima batteries have very high cranking amps(CCA), and are very resistant to vibration, and pretty tolerant of abuse. But for their size they do not have much capacity(AH) amp hours. An AGM battery that is rectangular will yield just as much ( if not more)cranking amps but have 25 to 35% more capacity. All AGM batteries will have a higher cranking amp rating than any flooded battery of the same size. Generally flooded batteries will have about 5% more capacity than the AGM battery of the same size

Battery abuse is when you discharge them below 50% and do not recharge them fully or promptly. True deep cycle batteries are most tolerant of this abuse. The next most tolerant batteries are the dual purpose batteries. These will say marine/ trolling/ RV/ deep cycle on them. The least tolerant of abuse are starting batteries. These should not be discharged below 80% and will not last long if cycled deeply.

In you application I would recommend Odyssey batteries. Die Hard PLATINUM batteries are the same thing for 25% less $.

Now to isolate them, the easiest way is with a Continuous Duty Solenoid. They look like this:
[Linked Image]

Get one rated for at least 100 amps continuous. The 2 bigger bolts are for the battery Hot/Positive wires. One side goes to the engine battery, the other side goes to the auxilary batteries. The 2 smaller wires are for activating the solenoid. When these see 12 volts from a switched source, it connects the 2 bigger wires together, paralleling the batteries. Ideally you want to the switched source to be something that is hot only when the engine is running, rather than just the key turned to on or Accessory.

You can just hook the negative wires of the batteries together.

Now it should be said that everybody overestimates The alternator's ability to fully recharge a battery. A 130 amp alternator can only output that in a laboratory, when cold, at high rpm. On top of this, the vehicles stock wiring is only adequate to power the vehicles accessories, and recharge a slightly depleted starting battery.

So There are a couple things you can do, the last of which is a bigger better alternator.

First, the wiring between the solenoid and the auxiliary batteries is very important. It has to be at least 6 awg cable for okay charging. The thicker the better.

This wiring does little good if the Stock charging circuit is not upgraded as well. The easiest way to do this is to run another (fused) cable directly from the alternator(+) post to the Solenoid. You want to wire it to The side of the solenoid which connects to the engine battery.

Upgrading the hot wires is no good unless the ground wires are upgraded as well. The negative is shared by the whole chassis. The engine has a pretty thick ground cable from the battery.

What you can do is run a fat cable from the auxuiliary batteries to the alternator's (-) stud, or one of the bolts that attaches the alternator to the engine.

Once you have done the above steps, you are at the limit of the alternator's capability. The limiting factors at this stage are the voltage regulator, and the alternator itself, and any poor connections in any part the charging circuit.

If at higher RPM and the batteries are under 80% charged, and the voltage does not rise to the mid 14's. Your voltage regulator is not allowing the alternator to work as hard as it can. If the alternator is internally regulated, nothing you can do.

There are many other ways to have batteries isolated from the engine battery yet still charge when the engine is running.
IMO, this is the easiest, most effective, automatic way.

I myself use a true manual switch.

[Linked Image]

I have my batteries under the floor behind my driver's seat and the switch in the cabinet above them. I need 12 feet of cable (one way) to reach the engine battery. I need 11 feet of cable to reach the battery switch from the alternator.

When I added another 2 AWG cable from the alternator to the battery switch and another between battery and ground, my charging amps at higher RPM's increased about 120%.

My 130 amp alternator is only capable of 32 amps at idle speed, when hot.

If you want your batteries to last( for years), you must think of the alternator as only able to supplement what your stereo use. Even with an upgraded charging circuit/ system, 2 depleted batteries are going to require many hours of driving with engine rpms above 1800 to fully charge them.

Since this is not usually feasible, you should have a good 3 stage automatic battery charger, and plug it in when you get home. Have a convenient way to do this and you can get 5 years or more out of your batteries, and never have them let you down during an outing. If you don't, your looking at about 2 years.
Posted By: Astro

Re: auxiliary batteries - May 31st 2011 4:15 pm

I recently installed a solenoid to isolate my batteries when the engine isn't running and it seems to work great.
the only thing I am going to change is currently it is connected to the ignition, and I am going to move it to a dedicated toggle switch.
Posted By: maples01

Re: auxiliary batteries - June 02nd 2011 8:43 am

Offered to tournament fishermen is a new state of the are deep cycle charger setup to hook up your alternator to charge the batteries, it cycles so they get no more than 5 minutes of the high amperage from the alt, keeping the plates from heating up, and allowing a few minutes to cool before re-engaging. I read about it in a fishing magazine, for tournament fishermen who'll not have access to a charger, even has a lead that plugs into the truck to charge as you're driving to the lake. It ain't cheap, it's about $300 to start, even offer them with extra banks to charge multiple batteries. Seems boaters trying to shed weight in their boats are opting for smaller, lighter batteries, and this is allowing them to keep the batteries going by charging them as they move around the lake using the engine. The article was by a boater, not dealer, he said even in the windiest conditions he's not had to leave the lake or change his fishing characteristics, as the trolling motor holds up on the well charged batteries.
No battery likes constant heavy amperage, that's why the vehicle alt has a regulator but there is a lot of demand on them, electronics in todays vehicles, multiple batteries could be hard to keep up with, without over feeding them, could be a good idea for me. Sure would answer the call for those who want deep cycle batteries but keep the weight down, go with smaller ones and allow the engine to take care of them.
Posted By: Ken_Karnage

Re: auxiliary batteries - June 08th 2011 8:00 pm

I'm in the process of setting up a similar system. I have two deep cycle gel batteries mounted under the van in a custom box. Is there a way to setup a "reverse inverter" so I can simply plug into shore power when I get home, or would It be best to do a permanent mounted charge and wire that for shore power? I'm looking for ease of use, and am still in the beginning stages of the build, so mounting anything at this point is not a big deal.
Posted By: maples01

Re: auxiliary batteries - June 09th 2011 6:50 am

You'd need something like the campers have that charges the batteries and powers from the 110 source, I'm betting it's expensive.
Posted By: River_Rat

Re: auxiliary batteries - June 09th 2011 1:12 pm

These semi tricks have two big brass studs mounted on the frame under the hood so you dont have to take the battery box off if you need to charge or jump it off. And they have nice black and red boots to cover them when not in use. Drag cars use them to. Just mount them under the van somewhere that you can get to them easy to hook your charger to. And would come in handy if you needed to jump your own van off or someone else
Posted By: wrcsixeight

Re: auxiliary batteries - June 09th 2011 1:15 pm

Ken, The product you seek is called a converter in the RV world. It is designed to power all the 12 volt appliances when plugged in as well as charge the batteries.

Progressive dynamics, Iota and Paramode are just 3 makers of converters.

A place called best converter sells them all and has good customer service.

Are your batteries really GEL batteries, or AGM? Gel batteries require specific chargers because they will be damaged by 1 overcharge. Generally alternator voltage is too high for gel batteries and that makes their use in vehicles impractical.

AGM batteries are another story, and you are good to go if these are what you own.
Posted By: Ken_Karnage

Re: auxiliary batteries - June 09th 2011 4:34 pm

I'm pretty sure they are gel, but i'd have to look at them to be sure. I asked the guys at the interstate battery dealer what I was looking for, and what I was using them for and got what they hooked me up with. I'm not much on an electrical guy, so I've been relying heavily on the advice of others....hopefully I got the right ones smile

Both the inverter, and the brass studs sound like great ideas...I might do both for the sake of convenience in the event I need one and the other is not functioning.
Posted By: frscke1

Re: auxiliary batteries - June 09th 2011 9:23 pm

Here's the original thread and alot of good ideas

[Linked Image]
[Linked Image]

this converter has a plug on it to recharge or run 120v at a camp site..
Posted By: Astro

Re: auxiliary batteries - June 13th 2011 2:32 am

made my switch for my solenoid, now to install it!

Posted By: Lee7673

Re: auxiliary batteries - June 13th 2011 2:35 am

Originally Posted by Astro
made my switch for my solenoid, not to install it!

Posted By: Boot

Re: auxiliary batteries - June 13th 2011 4:13 am

How about a schematic, Dave?
Posted By: maples01

Re: auxiliary batteries - June 13th 2011 5:22 am

My solenoid is hooked to my ignition switch, but Ive thought about putting a switch on it, but scared I'd forget to turn it off, how'd you do the buzzer addition?
Posted By: Astro

Re: auxiliary batteries - June 13th 2011 12:11 pm

I'll post a schematic as soon as I can draw it correctly! lol

the buzzer was one I picked up from radio shack, you can get one like I did that pulses, or one that has a continuous buzz, etc.
Posted By: Astro

Re: auxiliary batteries - June 13th 2011 4:11 pm

also, this is the solenoid I used,
[Linked Image]
Posted By: Astro

Re: auxiliary batteries - June 13th 2011 7:12 pm

and it's in

I plan on making a nicer mounting plate for it, this one was just the rough draft.
after the nats I am replacing the whole face piece for my overhead, and re-arranging it all, etc...
Posted By: Lordmodelbuilder

Re: auxiliary batteries - June 13th 2011 7:51 pm

Looks nice Stro! Did you just do all that so you could manually turn the solenoid on & off? Any reason for doing it like that other than not wanting to have the key on?
Also, do you have a fuse between the power source & your toggle switch? Thanks,Brad
Posted By: Astro

Re: auxiliary batteries - June 13th 2011 7:55 pm

I didn't want it on the ignition because when I hit the starter, the batteries would equalize.. not good if the 2 in the back are flat....
I wanted a little more than just a toggle to close the circuit.. so I added the little alarm to remind me to turn it off when the engine isn't running, yet I can still use it to jump the front battery if need be.

plus it looks cool, lol
Posted By: Astro

Re: auxiliary batteries - June 13th 2011 8:43 pm

of course, I get the thing all installed, and my voltage meter decides to act up.. it just keeps scrolling LO over and over... like it is stuck in it's test loop. can't get it to display voltage anymore.

bought a different one that will work better with my setup to replace it
Posted By: wrcsixeight

Re: auxiliary batteries - June 13th 2011 9:13 pm

I assume you are talking about a dash mounted voltmeter?

Did you put a regular multimeter on the aux battery terminals with the engine running.

I am actually helping a friend to install an aux battery on his '98 Astro. We welded up a battery tray big enough for a group 31 sears Die hard Platinum, and are going to weld that to the transmission support cross member.

I am trying to talk him into a manually switched solenoid, but he likes to argue just for arguements sake.
Posted By: Astro

Re: auxiliary batteries - June 18th 2011 5:16 pm

yes, it was just a simple LED voltage display. it fried somehow. no matter what I connect it to, it just runs through it's diagnostic screen over and over.

I ordered a new one, slightly nicer looking as well. hopefully it will be here this week and I can get it installed.

on a side note, if anyone wanted one of these and wasn't comfortable with the schematic, I could make it in a little box that you could mount wherever you wanted. could make it with either a pig tail, or screw terminals for where you connect power, ground, etc.
you could use this for anything, not just a solenoid.

cost would be some of the parts and shipping and a little for my time
Posted By: Astro

Re: auxiliary batteries - June 18th 2011 5:21 pm

I am thinking I may add another indicator light off of point 6 on the toggle... as a reminder to turn the system on when the engine is running. putting there puts it on ignition power, and the circuit for the light is broken when I close the circuit for the solenoid.
now I need an amber LED, lol
Posted By: gopher

Re: auxiliary batteries - June 18th 2011 5:48 pm

get a plactic battery box to hold the #2 batt and a deep cycle as the #2 it discharges a lot slower then a cranking batt duse
Posted By: CustomVan

Re: auxiliary batteries - June 18th 2011 5:58 pm

I'm going to have Dual battery kits at the NATS for around 100.00 .EVERYTHING YOU NEED (fuses at both ends, switching solonoid,battery box (large), Ground Wire , 20' of Hot wire and 5' ignition trigger wire with all necessary electricl connectors already installed where applicable) BUT the battery. Installation available at the NATS too! You gotta let me know , so i can make appointment for your install and so i bring enough kits for everyone! call 800-495-8267 (VANS)...can also ship ANYWHERE
Posted By: Astro

Re: auxiliary batteries - February 24th 2017 12:37 pm

Imageshack ate my photos, I'll have to see if I an find the schematic and repost it
Posted By: KevinWangxxx

Re: auxiliary batteries - March 27th 2017 6:24 am

Originally Posted by Ken_Karnage
I'm in the process of setting up a similar system. I have two deep cycle gel batteries mounted under the van in a custom box. Is there a way to setup a "reverse inverter" so I can simply plug into shore power when I get home, or would It be best to do a permanent mounted charge and wire that for shore power? I'm looking for ease of use, and am still in the beginning stages of the build, so mounting anything at this point is not a big deal.

yes get this, I had it in my other van and loved it I will probably order a new one.
Posted By: PatDoody

Re: auxiliary batteries - October 09th 2017 2:21 am

I just did this in my van to run a 3000watt inverter for a mini fridge and what ever else. I used a 150amp smart sensing batetery isolator from battery doctor;psc=1&refRID=5055JQJB82EC63X9CPS8 I wired it to a 150amp circuit breaker then to a 900cca marine deepcycle battery in a battery box. Needs to be deep cycle because they are used to being drained and recharged. Normal batteries wont last. I used 4awg wire to connect everything.

Test ran it this weekend and it kept the mini fridge and dewalt radio going non stop the entire time. I also ran a box fan while I was asleep no problems. I still have a 1971 45amp stock alternator too. I am gonna upgrade that to a 90 or higher amp alt and I think ill be all set.
Posted By: wrcsixeight

Re: auxiliary batteries - October 09th 2017 8:12 am

Lead acid Batteries Need to be fully charged, as often as possible, as quickly as possible after any significant diacharge.

The alternator is controlled by a voltage regulator

Voltage is electrical pressure.

A quality new Marine battery of the group 24.27/31 sizes, discharged to 50%, can, if allowed to be brought upto mid 14 volt ranges at amperages from 35 to 55 amps, can perhaps reach 80% charged in 35 to 45 minutes.

But getting from 80% to 100% charged, cannot be accomplished in less than 3.5 more hours, and that is with a new healthy battery under ideal recharging currents..

That 3.5 hours assumes that the battery is brought to and held at ~14.5 volts the entire time.

If the battery is only brought to 13.8 volts, that otherwise healthy battery will require 8 to 12 hours to get in the 95% range and 95% to 100% will take about 6 to 12 more hours. It does not matter if you have a 200 amp chromed alternator recently polished, a battery can only accept so much amperage and can only be recharged so quickly, and by quickly I mean slow.

The Best lowest resistance AGM battery, A Northstar or ODyssey AGM, discharged to 50%, cannot be recharged to full in less than 6.5 hours. Flooded marine batteries will take longer, Abused or older batteries take much longer. Ideally one should not really discharge a battery below 50% state of charge, and 50% under no load, occurs at around 12.2 volts.

100% fully charged is where the battery always wants to be. Anything less than this degrades the battery capacity, and the lower it goes and the longer it stays there the faster the battery capacity degrades, and the harder and the longer it will then take to recharge the battery to the maximum remaining capacity the battery has left.

An aging battery is like a gas tank which keeps shrinking.

To prevent that gas tank from shrinking too quickly, refill it to abslutely full as soon as possible. Do NOT rely on the alternator to do this. It is VERY poor at doing this, even if one is driving for 6.5 hours.

Or simply resign youself to replacing batteries more often and likely having them fail to power your needs when you most need them.

MOst vehicle will not hold mid 14 volt ranges for very long, which greatly slows recharging.

Those who use their batteries hard, should be able to plug the battery into a charger once they get home, if they want any sort of longevity from the battery. Those that rely only on the alternator for recharging, and use the battery hard will be dissapointed, often, in the lifespan of their battery.

The best flooded marine batteries can last about 600 to perhaps 800 deep cycles to 50% state of charge, when recharged promptly and fully after each discharge.

This same battery recharged to 80% and rarely any higher will be lucky to last 50 deep cycles in a two month span.

This is not the fault of the batttery, but the human charging it.

I would hate being a battery retailer. What other product can be destroyed through ignorance and misuse/abuse, and have the consumer demand a new one under warranty?

Gee, I drove my new car into a lake, that is covered under warranty right?

A digital Ammeter showing how many amps are flowing into a depleted battery is wise, So is a voltmeter whose leads are right on the distant battery.

I have one of these displaying amperage into/out of my battery on my dashboard:

The more amperage the battery accepts, the more discharged it is.

A single group 27 or group 31 marine battery, when near fully charged and held at 14.5ish volts will accept about one amp
If the battery is accepting 15 amps at 13.8v, it is NO where near fully charged.
A 50% charged healthy group 27 battery will easily suck up 50 amps for about 15 to 20 minutes before voltage rises to 14.5v, supposing the chrging source can produce 50 amps and is actually seeking 14.5v, and there is little voltage drop on wiring from charging source to battery, and back.

There is a lot of battery charging myths out there. These myths kill batteries and drive up the prices for all of us.

The lead acid battery wants to be full and kept cool at all times. It takes a long time under ideal conditions to fully charge a battery. The 200 amp alternator, even chromed and recently polished is not going to reduce that time, unless one is also running 150 amps of lights and stereo, but 6.5 hours from 50% to 100% cannot be reduced, no matter what.

So plug in and recharge to full when you can, as soon as you can.

I have an optimized chrging system, I can spin a dial and control the vehicle's voltage when the engine is running, I have 200 watts of solar on my roof, I have an adjustable voltage 40 amp power supply. The capability of these 3 charging sources have allowed me to achieve over 700 deep cycles over 4 years from a 90 Amp hour group 27 Northstar AGM battery, and it is my only battery for everything, and I use 35 to 65 AH of that 90AH capacity at least 3 nights a week.

I can carry 345 Ah of battery capacity, but have been using only 90AH total for over 2.5 years now, as I also know how much of the battery I am using by using an amp hour counting battery monitor.

But none of these charging sources is automatic, as automatic basically means undercharged, as automatic cannot see the variables and adjust accordingly.

One does not need to achieve charging perfection, but they shold know what perfection entails, and where to draw the line. often it is easier and cheaper to simply accept poor battery lifespan, but the cheapest weay to ensure good lifespan is by plugging the battery into a capable wall charger as soon as possible after any discharging of the battery occurred. This will also extend the life of the starting battery.

Sometimes if one plugs in as soon as they get home the surface charge on teh still well depleted battery will tick the automatic charging source into thinking the battery is already full, and it will not seek 14.5ish volts. One often has to be smarter than the smart charger and reduce battery voltage by applying loads to it before hooking up the charger and letting it do its thing.

A few restarts of the charger might be required before the battery is truly full, and an abused battery could require higher voltages than automatic chrgers will allow.

The well marketed 'desulfating pulse chargers' are largely gimmick, but do not hurt the battery.

Seek at least a 10 amp chrger for a 100 amp hour wet/flooded battery and at least a 25 amp chrger for a 100Ah AGM battery, and if one gets an Odyssey AGM battery, these Dictate 40 amps of recharging current per 100Ah of capacity when discharged to the 50% or less range.

Low and slow 'trickle charging' will tickle deeply cycled AGM batteries to death.

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