Ok. I have read thru all the posts about alternators and dual battery setups.

My situation is I need additional 12Volt power for my offroad nighttime activities,
I have 2 spotlights and 2 PIAA 520 lite kits out front. With the truck running I have no problems with everything running at once even under extended 4x4 multi hour beach trips. So this tells me that my Alternator is handeling my load just fine.

My problem is that I goto remote locations often and sometimes I have been known to turn on the truck lightbar to deal with something and then run the truck dead cause I am busy doing whatever.

So I have decided that I want to mount an additional battery in my toolbox in my bed and have my lightbar and spotlights run off that battery and issolate the battery for starting the truck. At a later date I might want to make the factory car stero run of the second battery but now a big deal.

So if I get a relay the will allow me to break the second battery away from the normal system I should be good to go, at least that's what I thought.

Real Question: I have read a couple people talk about having to upgrade their alternator to deal with the load of 2 batteries. This seems silly to me but I wanted to toss this out there. Is my 130 Amp alternator going to be able to charge a dead battery? I just dont know why it would not and once I started my car one battery would be fine and the other would need a charge.

Anyone have any sugestions on good Battery Isolators/relays? I allready have my battery mounting figured out.

Thanks!

 

the more work an Alt. has to do the quicker it will wear out. charging a battery with the Alt. is hard on it and the battery, unless the battery is a deep cycle.

if you connect the battery's in parallel then they will not drain as quick a just one. you wont need any relays and you'll double the cranking power but still only have 12 volts

 

Get an optima yellow top. I had the same problem with my nav with all the crap I have added, and the autolamp staying on for just afew minutes would drain it. Added theyellow top, and no more problems

 

Connecting the alternator to a dead battery cause very high current flow.
An alternator is rated in max amps and max wattages but that does not mean it can handle full output for longer periods of time with out risk of overheating and stack loss.
Why not consider a small gas generator to power 120v spots or floods and get around all the problems. Total cost should be about the same.
Works for me at nite in the race pits and for everyone else.

 

Well I use my truck for Hunting and Fishing. Hunting at night for Hog's in texas is legal and sometimes means that I have to turn on the lights, shoot and run.

Also fishing on the beach here in texas, At night when I get a hit my glow sticks go flying and I flip on the lights and go running for my pole.

Basically I have ran my battery down on mutiple occasions.

So I allready have a yellow top, believe me it helped but this is not the bottomless pit of battery power.

I have a 12 volt DEEP cycle battery mounted in my bed box allready, and this is nice for running the spots that plug into that battery and will do so for a LONG time, i would just like a way to charge that battery when it's drained. This is never a problem for single and double night stays with the low load on that battery.

So perhaps what I need to do it run the 2 batteries in parrell, but I want some failsafe to stop the battery drain at a certian level. perhaps one of theos voltage cutout switches I have heard of that seprate the two batteries after a certian voltage is hit to save the system?

I understand the higher load on the alternator= higher wear, but if I am only draining 1 battery, then there is really only one 1 battery chargeing.

As for the Generator, we use one when fishing sometimes, hunting this is not an option, but really I am trying to fix an ongoing problem I have when I need to flip on the lights and run, i am not about to lose another shark cause I try and let out a extra 100 yards of line so I can get back to my truck and turn off the lights..

Thanks a bucnh guys...

 

Go with a heavy duty alt, and let the engine idle. We do it with our work vehicles all the time. Some up to 8 - 10 hours at a time. These trucks can handle it. The fuel injection is much better at maintaining a good idle that will not hurt the engine. But I understand you may not want the noise of the engine idleing while hunting.

 

I understand what your doing now and the requirments you have.
As it is now your tying to go against normal laws of electricty as far as battery capacity, charging ability and current draw go.
The fire and rescue trucks all have big-big alternators and batteries to run there light.
Special boom trucks often have an idle raise feature built into the PCM program for operating hydraulic pumps and higher alternator current outputs.
I would try researching these areas, aftermarket service companies as well as low current hi voltage/brighness lighting like HID.
The trick were looking at is raising the efficiency of the lighting and reducing the drain requirments as well as increasing the current capability of the charge system.
Hope you have some spare money.
Good luck.

 

I guess I dont understand the problem. If I have two batteries that are seprated when the truck is off and I run down the second battery with the lights, then start up on the first battert, then connect the batteries again I will really only be charging the one battery that is down, and topping off the primary a bit from starting the truck. I am thinking that a super duty Alternator makes no sense in this situation. it's only a real 220 Watt light draw here we are talking about. 4x55watt. If I had a winch or hydrolics and the like going i could understand, or if i drew 2 batteries to their knees. But really, just running one down should not require a huge ordeal right?

And I do have the 130 Amp Alternator. No aftermarket stereo or anything
but the lights.

thanks

 

They are just saying that the chargeing of the AUX battery from a fully discharged state is a LOT more work for the alternator than its usual mode of topping of the primary, post-crank. It will handle it, but it will likely shorten its lifespan somewhat. I say go for it, and make sure you use at least 4AWG cable to connect the AUX batt to your charging system and chassis ground. Also consider upgrading the OEM engine block to frame ground link, as this will likely become a weak spot in the circuit.

If you are putting the AUX batt inside your toolbox, or some sort of enclosure, you will have to vent it or utilize an AGM type of battery that is OK for non vented installations.

Good Luck.

 

OK, so charging a dead battery is more "work" for the alternator, but why should that shorten its life? The construction, conductors, and internal parts are sized for the current. Is the "shortened life" based on something real, or is it a myth?

I could see that an overload would damage something in the windings or in the regulator, but other than that, I don't know of any basis for a claim of shorter life for the alternator.

High-rate charging of the battery is another story, though - you need to look at the charge rate requirements for the particular type and brand of battery you have. Keeping charging cable size down could actually help limit the current - you might not want to use #4 cable. You would want to use a disconnect or a battery isolator, or you'll end up with two dead batteries.

 

Today I have two of these.
http://www.power-solutions.com/batte...d/121/387.html
UPS 12-475FR

They are daisy chained and provide a TON of power backup. This and a yellow
top and I am doing allright. I have charged them at home the last couple times and decided I dont need two of these, i only need one but would like to run my truck lights off of them.

I totally understand what you all mean by use is wear, for sure. I am thinking I am going to go for it, in the off chance that I happen to charge this battery from dead once or twice a year I'll keep in mind that I am useing a resource.

The enging ground is not something I am aware of. do you have a link? I have
4awg wire ran allready and actually double up when I did it thinking I would run two batt's back there. Now I guess if I get some fuseable links I got a backup jumper circuit if the relay/isolator fails or something. i did it up all nice thinking I was going to get a undercoat for christmas, dident, got a rifle. not bad. ;-)

Anyway thanks a bunch guys. Gonna get some amp loads with the lights on
here soon and see what ragne i am really in.

Brian

 

Here are two answers that can be banked on as accurate.
1. Running one battery down, then starting the truck with the other,
then hooking the batteries togather causes the flat battery to take current from the other battery until they both arrive at the same lower voltage. With the alternator conducting the charging 'show' after that happens is to charging wide open until the batteries charge state rises and begins to taper off like normal but the current is high and the time longer. This is where the problem can arise.
2. Yes the alternators have a rating but as I had said up the line here, they are not built to run at that level for "extended" periods of time without possibility of damage no more than a capable person can run holding 100 lbs of sand for very long without getting pretty hot and tired.
Ask an alternator shop about this, if in doubt.
Many replacement alternators have a notice with them 'not' to attempt to charge a flat battery after installation but make sure the battery has a reasonable charge in it before starting the engine by jump start methods.
Many people replace an alternator, go round and round still with a problem only to find the replacment alternator is bad and blame the store they got it from after 'they' lost it.
The impedence (resistance) of a dead battery is nearly zero and is why the charge current becomes so high. It acts nearly as a dead short to the charge circuit.
Not following these electrical principles only results in failure in the field after it was thought the application was solved for by spending for more eguipment that failed anyway.
What goes on in these circumstances cannot be defeated or gotten around.
Good luck. I'm not trying to sell anything but what is real.

 

Ok. So that makes a lot more sense now....


So if I get a heavy duty alternator with 2 output's do i then get around the issue of the two batteries evening out if one is dead?

Thanks a bunch, I am starting to see the light here....

 

IMO, your biggest problem is handleing a battery that has been deeply discharged.
I would be looking at charging it at a lower rate until the charge level gets up to a state the altenator can work on without really high currents for an extended time interval. There are ways to do this.
Battery plate material plays a part in how this is handled.
A good 'standard type' battery recovers at a pretty quick rate.
So a lower charge rate to bring the battery up, so regular charging can be allowed without risk.
These other hi capacity batteries have fibeglass matt structures for plate material that gives a long crank time but this also results in a longer charge time. Again a function of the plate material.
You can see how involved this gets by knowing these little things.
I would consult a speciality shop on your application to see what they can come up with to help develope a hardware alteration, battery type and procedure to keep you out of field trouble.
Good luck.

 

That's just what I did. Went to the RV shop across the street. They have come up with a idea.

Basically I take my lights and make it so i can select where they are powered from. I have a switch that uses a 2 position relay, position 1 get me power for that acessory bar from the primary battery, position 2 get me power from the backup and then there is off where both are off. This is the best solution so far that I have come up with, but does not address my wanting to charge that battery but with 134 Amp Hours I think I have enough juice for everything I am going to encounter in the near future baring Nucalar war and some post apoaliptic enviroment.....

Thanks a bunch everyone!