Battery Isolators

[bcroe]

I keep reading about these RV battery isolators. One version used a couple
really big diodes from the alternator plus output, to the 2 batteries. It wastes a
lot of power by adding a diode drop, and might mess up the voltage regulator.
Another really smart one uses fancy electronics to reduce the diode loss. And
one uses a solenoid that must be operated at the right times, without fail or welding.

This may be an old idea, but it seems to me there is a better way. The (3 phase)
alternator already has 3 diodes to ground adequate to handle its capacity, and 3
more from the same windings to the positive output. WHY NOT just add 3 more
diodes from the windings, to the second battery positive? This is as efficient as
no isolator, and foolproof. The regulator would still work as before, the batteries
will eventually reach close to the same final voltage.

Some alts already have external winding terminals available. The more difficult case
is going inside and tying to the original 3 winding-diode junctions. Bruce Roe

[Sunking]

You are looking at old Isolator Technology Bruce. The newer Isolators take the voltage regulation out of the Alternator to the Isolator. That allows then for you to select the appropriate voltage for each battery port. Then some of the new Isolators made to fit any vehicle use Switch Mode Buck/Boost regulators to achieve the same voltage control to the battery.

[bcroe]

You are looking at old Isolator Technology Bruce. The newer Isolators take the voltage regulation out of the Alternator to the Isolator. That allows then for you to select the appropriate voltage for each battery port. Then some of the new Isolators made to fit any vehicle use Switch Mode Buck/Boost regulators to achieve the same voltage control to the battery.

Perhaps you could point out a model or 2 of that type? That sounds like a lot of complexity; its not obvious to me
what the advantages would be. The the isolators I compared to are on the market today, results of a very short
search. Bruce Roe

[Sunking]

Perhaps you could point out a model or 2 of that type? That sounds like a lot of complexity; its not obvious to me
what the advantages would be. The the isolators I compared to are on the market today, results of a very short
search. Bruce Roe

Bruce it is not complicated moving the Voltage Regulator out of the alternator. It is a 2 or 3 wire plug you unplug from the alternator and plug into the Isolator Marine market has been doing it for a couple of decades. Auto sector has just been slow to change.

With new vehicles even makes it easier on some manufactures because the VR is already external to the alternator, so the Diode models still work because the voltage loss is seen at the battery by the VR and raises the alternator voltage. Universally today SAE has set the voltage to 14.2 volts because 14.2 volts works well with FLA. AGM, and LiFeP04. Look under the hood of most new vehicles today and you will see an AGM battery.

OK I will throw you a couple of bones.

Sure Power sold by ASE. You have to match Group Number to auto manufacture.
Intervolt is another one.

There are at least a dozen more out there.

[bcroe]

I snooped around some of those devices, but they all seem to take a standard alternator + out and find
ways to send it through MORE devices to 2 batteries, without allowing feed across current. That means
more voltage drop and more wiring, and more failure modes. For now I'm sticking with the idea of just
adding a second set of 3 + rectifiers from the alt to the second battery. Could even be another alt type
diode block put in the alt if it will fit, the total heat generated doesn't increase, just shifts to the lower
voltage battery ckt.

Every alt I've seen from 1976 to 2001 has the voltage regulator inside, using either a sense wire or
connected to the main output terminal. That is just fine; since my scheme doesn't add any voltage
drop, the original reg can stay the way it is. There have been some alts with the DIODES mounted
externally; that just makes it easier to do this.

Guess I should be drawing a picture. Bruce Roe

[bcroe]

Here is a quick sketch for the simple, efficient add on battery isolator. I'd try to just mount another power diode set
on the alt; can use the same heat sink since total losses are not increased. Bruce Roe BatIsolate.jpg

[SWFLA]

Once the SLI battery is charged, you will have a trickle charger.

[bcroe]

Once the SLI battery is charged, you will have a trickle charger.

Would you explain please. Bruce Roe

[SWFLA]

since the regulator is sensing your main battery as soon as it's charged up its going to cut the amps way back. the regular controls the current to the rotor and thus how much of a magnetic field it creates. Blue Sea Systems has a wide variety of ACRs or BEP. They are very reliable. Just sold my last 14v/50a - 28v/140a dual voltage alternator.

[SWFLA]

Mastervolt Battery Mate - a little more expensive but top-notch. And losing a small amount of voltage and probably be a good thing.

[bcroe]

since the regulator is sensing your main battery as soon as it's charged up its going to cut
the amps way back. the regular controls the current to the rotor and thus how much of a magnetic field it creates. Blue
Sea Systems has a wide variety of ACRs or BEP.

That Mastervolt Battery Mate seems to be a pretty sophisticated stuff, for those who need that. I was looking to replace
the "2 big diodes" isolators that are being sold today for simpler systems. They work, and I think mine works the same,
something like this.

The battery with the lowest state of charge will pull the alternator winding voltage down to within a couple diode drops.
Current will flow there. If the other battery is in a higher state, it will get little current. Its voltage will drop some from
receiving full current at full charge, and the regulator will keep current coming regardless of which battery
its connected to.

After a while the alt will pull up the lower battery till its about the same state of charge as the other battery. From that
point they will both take current and rise together till neither needs much current and the reg shuts down. An alt reg
isn't going to "latch" into different states and leave one battery not finished. Bruce Roe

[misty607]

very new to all of this and will be the first to admit I am lost! I have a bus that I gutted and am at the point to add my battery bank. My plan is to install a continuous solenoid system and add solar in the future (when funds allow lol) I'm trying to find out if I need, if it exists, or what type of battery regulator would be best. I have 2 100ah deep cell, and a windy nation 2000w inverter. My only needs are to power a small fridge, a microwave, and a small portable air conditioner as the air system was ripped out of the bus prior to purchase. I have a blue print as to how it will be hooked up but it wont let me post it here. Any help would be much appreciated. (in laymen terms please as i said I'm just learning all of this)

[Sunking]

since the regulator is sensing your main battery as soon as it's charged up its going to cut the amps way back.

That is complete nonsense. Ohms Law is what regulates the current. When the battery voltage and alternator voltage are equal, there is NO CURRENT. Simple Ohms Law.