Electrical/Winch questions...

[AZShooter]

All,

I am adding a 12,000lb winch and off-road lighting to the K5 and was concerned about battery usage. We decided to add an additional battery to the left side of the engine compartment, but I had a few questions...

Has anyone done this before? Any recommendations on an additional battery tray? Does the alternator need to be upgraded? Do any other stock parts need to be upgraded? Note: Running a 350TBI.

Thank you!

 

[Fordum]

Hang on tight.
You should get lots of answers........

Just the dual battery part has several answers. I prefer the diode isolator system, but its not as popular here.
You can just hook the two in parallel, which gives you more current for the winch along with increased capacity.

But, once you have added the second battery, you might as well get some of the other benefits too.
Such as one battery to run everything, keeping the other in reserve in case the main one runs down.

 

[nvrenuf]

There was a factory option for dual batteries that utilizes a driver side battery tray. Check the for sale forum here for used trays.

 

[dremu]

The auxiliary battery tray was a factory option, so parts can be had from the junkyard, used sales, or even new. You can get them from the dealer (though not cheap ) or from various mail order outfits, e.g.

http://www.lmctruck.com/icatalog/csb/full.aspx?Page=179

You can google "battery isolators" for the bazillion options. I'm with Fordum on simpler being better; the diode isolators are pretty simple.

Mine is ridiculously simple (and was the factory option for the auxiliary battery originally): I use a solenoid to connect my batteries when the engine is on, i.e. the alternator is charging, then disconnect the auxiliary when the key is off.

You should have a higher-capacity alternator, yes. Batteries don't run forever and will need something to charge them -- said another way, the electricity to run the winch has to come from somewhere.

-- A

 

[AZShooter]

Whoa!! Thanks, guys. I wasn't even thinking about an isolator.....you probably just saved me some serious field time.

I noticed the bazillion different units, any brands that are good for longevity and heat resistance? What do you recommend on the amp ratings? 90? 120?

Thanks!

 

[dremu]

At most the isolator should be rated to carry the output of the alternator.

If you have a 100A alternator, say, if one battery is entirely dead then its leg would see that 100A. (The EE's among us are shouting madly, rightfully so, but this is loosely true.)

You might see if you can find a local, non-chain car stereo place, with the lowered iridescent salmon Hondas in front of it making horrible booming noises. These guys run auxiliary batteries for the amplifiers and are often more knowledgable/carry more stuff than the parts houses or 4WD stores.

You can also source nice flexible heavy-gauge power wire from them, or a welding supply house.

-- A

 

[AZShooter]

Dremu,

This is great advice. Thanks.

 

[Fordum]

I am going to copy this when I finish and save it on my desktop. I think I have posted it several times, and there is no sense in retyping it over and over.

I'm just going to hit the highlights. Mine was a Ford, which made it easier. I cut the main output wire coming out of the alternator.
Hooked the part coming out of the alternator to the center terminal, and the other end to one of the output terminals.
This meant, all the normal truck functions were powered by that terminal.

Then, I hooked to the second output, and ran that wire to a second battery.

I split everything up, so that the old main battery ran only the starter. All other functions were the responsibility of the second battery.

That way, I could run my big second battery down, and the main battery was hot and ready to spin the starter.

I don't remember what size the isolator was rated, but when jumping another truck, I managed to blow one of the diode.
Since I am an electronics tech, I went into it, and found a couple of marginal diodes.
I found that I could buy some the same size but rated much more current. Pressed them in and that cured it.

In general, it needs to be considerably higher amps than your alternator. Not only the one you have now. but the one you might upgrade too........

 

[MrTruck805]

I also run a big winch, and three extra sets of electrical lights. I use a marine deep discharge battery for my second battery. For the isolator I use an "automatic charge relay" - http://bluesea.com/category/2/productline/387

There is no voltage drop using an ACR as opposed to the older diode technology.

This system has worked great for me, but I'm sure you'll get a lot of good opinions from the folks here.

 

[AZShooter]

Awesome....getting a waterproof unit is tempting....

Fordum,

Are you saying that if the amp rating on the isolator is theoretically much higher than the alternator's output it'll function just fine?

Anyone have any pics of their setup?

Thank you all for your help!

 

[dremu]

Are you saying that if the amp rating on the isolator is theoretically much higher than the alternator's output it'll function just fine?

Isolators are rated at a maximum amperage, i.e. more amperage than rated and they will overheat, explode, fail, whatever. Anything less is fine.

So, yes.

-- A

 

[Fordum]

Diodes die from a couple of reasons.

Too high reverse voltage:
This usually occurs when you hook up a set of jumper cables backwards, which often gets other things too.

Too much current for the guts of the diode:
This is mostly unrelated to heat. The conductors and junction size are just too small and melt from the current.

And too much heat:
Diodes drop about .7volts per junction as the turn-on voltage. This generates heat. So, the bigger the rating of the isolator, the heavier the internal diodes, and the bigger the heat sink which keeps them cool.

So, if you have a 90 amp rated isolator, and a 90 amp alternator, then in theory all is well.
Even if the battery was dead and the alternator was putting out full current, then it should handle it since it was rated for it.

But, that design was made with certain conditions in mind. Air temp, that sort of thing.
And it was made as cheap as possible.

Its been a long time since I blew my isolator. I was always pretty sure it happened jumping off a completely dead battery.
I bypassed it until I could get a new one.
But, being an electronics engineer, I took the old one apart for fun. I don't remember the exact numbers, but the diodes were not rated as high as the isolator was.
I'm sure they figured one single diode would never see the whole output of the alternator, so it would work.

Seems like it was a 90 amp isolator with 60 amp diodes, but its been a long time.

But, 100 amp diodes were the same size, and cheaper than a new isolator. So, I just bought two and pressed them in.
Ran that truck for many years longer, never had any problems again.

So, I would oversize the isolator, and it should do fine. Just be sure to mount it as far away from heat as you can, and in a good airflow if possible.
I mounted mine on a fender under the hood on a thick aluminum plate, but that was just my normal overkill.

The relay setups do just fine, and eliminate the .7 volt drop. I personally like the solid state idea better, and there is no sudden load switching.

But lots of folks here run them and have no problems.
My only problem with some of them, is the undervoltage lockout. It would not let the alternator charge a completely dead battery, such as when you left the lights on all night.

But, I'm not sure if all of them have that, and it would be fairly simple to rig a bypass for those rare occasions.

 

[Fred_M1010]

There was a factory option for dual batteries that utilizes a driver side battery tray. Check the for sale forum here for used trays.

I think all diesels had this.
Could be good to know if you're planning a visit to a scrap yard.