You could put a diode and contactor in line that opens when the truck isn't started.

 

Clitoris, go to your local Napa, they will have an inexpensive isolation type switch.

They should also be able to provide you with an in-line fuse. Or, you could just use a chunk of copper pipe from your scrap-pile outback by the privy.

 

A couple of things to watch out for, based on personal experience;

1) Using any kind of semiconductor in series with a battery will result in less than a full charge to said battery. All silicon diodes have 0.6 volts drop across them, regardless of current. This means that the aux battery will be charged to 0.6 volts less than the alternator produces. On a 12 volt system, 0.6 volts is huge.

2) While some automotive alternators can handle full output continuously, most of the newer ones will burn up in a fairly short time if run hard. For example, a 100 amp alternator will produce 100 amps for maybe 30 seconds, then it'll produce maybe 40 or 50 amps continuously after that. The reason is because it costs more to make one that'll produce full output for a long time, and in a stock vehicle, full output is needed only long enough to charge the stock battery.

I have a two battery setup on my 77 chevy van. It has a 61 amp alternator which will produce the full 61 amps continuously, even on a red-hot day. After a bit of experimentation, I finally settled on a simple relay with the coil powered by the ignition circuit and the contact between the two batteries. Ignition off - batteries separated. Ignition on, batteries tied together.

As a slight side benefit, the aux battery will help the main battery a bit when starting the engine. I have basic 60-0-60 ammeters on both batteries, and while cranking, the aux battery shows a discharge and the main battery shows a charge.

 

As a slight side benefit, the aux battery will help the main battery a bit when starting the engine. I have basic 60-0-60 ammeters on both batteries, and while cranking, the aux battery shows a discharge and the main battery shows a charge.

I wonder if that is an indication that the main battery is degrading and the auxiliary battery is hiding the condition?

 

My truck came with two batteries.
I recently changed them to yellow Optima.
They are supposed to be deep cycle.
Stay tuned...

 

I am sorry for your loss. Optima batteries are like BMWs cheap crap, wrapped in great advertising.

 

Well, I was using a multi-type battery system due to different uses. I was going to keep a nice lead-acid as the main due to the thinner plates and low resistance for maximum starting power. Obviously, you don't want to drain the lead acid battery as much. It's made for maximum amps high momentary power burst and not deep cycling. I don't want sulphation problems as well. The deep cycle ones i'm putting in box are for deep cycling activities and maximum draining and re-charging due to the thicker plates. I still don't want full discharge on my deep cycling as this creates stress and reduces number of full discharges and life of battery.

 

Try this.

 

The regular batteries I was buying wouldn't last if I left my inverter on over the weekend. These dont seem to have any problem with that.
Ill see if I can get more than a couple of years out of them.

 

Remember, deep cycle red tops have very thick plates and are not designed for peak power requirements of starting an engine. You should never use a deep cycle battery for starting vehicles. They are for golf carts and things like that for long slow energy requirements

 

They were yellow tops.
Are there different uses for the different colors?

 

http://www.youtube.com/watch?v=FaM7exZmzKY

 

Damn, I screwed up my colors again! Nice refresher video though. I wonder if they have a compartmental battery with thick and thin plates for starting and deep cycle??

 

Yeah, for optimas... Yellow is deep cycle, red is starting.

 

Another interesting tidbit from my friends at electronics

Depth of Discharge 100% Starter 12-15 cycles , deep 150-200 cycles

50% Starter 100-120 cycles, deep 400-500

30 % Starter 130-150 cycles, deep 1,000 or more

 

I'm looking at going glass mat from rolls-serette here. The 12V 96pd one

http://www.dcbattery.com/rollssurretteagm.html

 

Good places to look for the components for your project are the RV and boating retailers. I just bud a job at the local Camping World and I had to leave the showroom before I left all (potential) profit in their registers.

I'm looking at a similar set up to your's Cletis, but want to add a PV component t out, too.

 

If I had a 5kw system installed, It would run my house all day under direct sunlight. We have plenty.
I would only save maybe $150 per month.
Not really much ROI I would think.

 

I run a dual battery 140 amp alternator. I'm on my third alternator which has lasted 132,000 miles. When using the inverter I leave the engine running, the inverter will draw a steady 100 amps depending on what I'm using.

 

I have one of these

http://www.galls.com/cgi/CGBCSTYL?PMSTYL=VP007

 

I noticed some people saying that they have isolators installed. Can someone recommend one and post how you like it? Thanks.

 

All isolators are the same, you just need to get one that can handle the amps you are going to push through it. I think a 100A isolator doesnt cost that much at all.. maybe around $50 IIRC

 

My cousin had a huge audio system in his car at one time had dual alternators and dual batteries. Not sure if you can get that for all vehicles.

 

I have installed a few big systems in vehicles, over 5Kw RMS. Big alternator, a few batteries, a cap on each amp... it gets expensive, and you havent even bought the $3000 box with subs! Theres parts for MANY vehicles out there, you just got to have the money.

 

Another way to go is to use an ACR (Automatic Charge Relay), which is common in boating and RV use. Instead of isolating with diodes, ACR's use relays (mechanincal or electronic) to isolate, combine or recharge the appropriate batteries. They sense the presence or absense of charging current, whether from an alternator or a house charging bank.

Keep in mind that auxiliary batteries should not be wired directly as a starting battery, and should have OCP within the first foot of cable. It's also a good idea to have full-current-rated switching to manually isolate or combine battery banks.

West Marine has very good articles (their "Advisor" series) in writing and video, on the subject of batteries, charging, inverters, and house/starting banks. I've used it extensively while I was a boater and it never left me adrift.......

 

Isn't the ACR that you are speaking of the same as the isolator that has been mentioned?


On another note, why would anyone use diodes to isolate something like this?

 

what do you think those blue things with fins are? Big ass diodes potted in a heatsink.:thumbsup:

 

RVs have a device Called a battery isolator, i have one in my dodge ram it looks like this one >>> and i charge 4 deep cycles with it... no problems with draining, they can be had for like $9 on ebay... http://www.pplmotorhomes.com/parts/...tm_medium=partsshopping&utm_campaign=partsfeed&gclid=CMHNjPbG_rQCFQWonQodRVAAxQ