2nd Alternator

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Nissi

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We have a Nissan NV200 Cargo Van we converted into an RV.
We have 3 /218amp AGM Batteries, / 4/ 105watt Solar Panels.
We like to Boondock. We are capable of charging when plugged in
to shore power, but often that is not an option in our travels.

Some modern Class B vans are using a second alternator to help
keep their house batteries charged. I love this idea!

We had thought to also mount a 2nd alternator, however, our
4.0L engine evidently does not allow room to mount the second
alternator.

My question is concerning installing an Isolator to charge the batteries
for those times when we are not getting enough solar charging capability.

Pros/Cons or any other thoughts?
Thanks :shy:
 
This has been discussed many a time on this forum. So do look for posts on the subject. With that said, It's my personal preference to use a Continuous duty solenoid and connect direct to the alternator. Meaning and this is by no means the gold standard....
Install the solenoid if possible in the engine compartment and have a switch in the drivers area to turn it on and off. Cable from alternator to solenoid and then from solenoid to battery bank.
BTW my switch is illuminated when on and has a safety cover to prevent accidentally turning on.
While driving activate the solenoid and and this will help you get those batteries back up to about 80% or so. I think we all pretty much aggree that the vehicles charging system can not really bring Large capacity batteries up to full.

MIke R
 
Sorry if this was a repeat... I missed other postings.  As I thought this was also a new practice of using the 2nd alternator.
However, evidently lots of folks have been using solenoids/isolators for a while.

I do appreciate your replies, Mike and highdesertranger !!  

Actually wondering about the advantages of the solenoid vs the isolator.  
Found info: here is one place... https://vanlivingforum.com/Thread-Battery-Separator-Isolator-vs-Solenoid?highlight=isolators
 
Been considering a second alternator too, for my E150. The AC compressor was removed by PO and replaced by a simple pulley. Be simple to replace it with a heavy duty alternator. I like the idea of a totally separate electrical system for the house power.
 
Interesting thought. How can a simple pulley work where a compressor was needed originally...?
 
Well the AC system was no longer needed, so they removed the compressor and replaced it with a simple pulley.

My AC compressor is now just a simply pully, a very heavy one whose pulley does not align to my other pulleys to my satisfaction. At some point my compressor bearing will fail, and I will need to rig up a simple pulley or rig up an alternator in its place

A secondary alternator is awesome for house batteries, as then one can use an externally regulated alternator, and then control it with a better voltage regulator Which WILL charge the battery faster and actually can fully charge it as fast as possible.

The problem with vehicles voltage regulators, is they are timid, for fear of overcharging the slightly depleted starter battery. When there are depleted house batteries to recharge this 'timid' voltage chosen is severly limiting the alternators ability to feed hungry house batteries, and how timid this is is highly dependent on the vehicle platform. Get a digital voltmeter and see for yourself. it might allow 14.5v for 15 minutes, perhaps much less, then reverts to 13.7v, and much much less amps flow into depleted batteries, but of course is still better than NO charging, but not nearly as good as charging at the acceptance limit of the depleted battery such as occurs at voltages ( electrical pressures) in the mid 14's.

The voltage regulator could be internal to the alternator, or Engine computer, or perhaps be a separate unit on the firewall, but this is less likely with a newer vehicle.

Mine was in the engine computer, and I tricked it with a 10 ohm resistor, and use an external adjustable voltage regulator whose adjustment know I relocated to my dashboard, next to my digital voltmeters(and ammeter) and now can always alternator charge as fast as possible with a battery that loves high amperage recharges.

more detailed write up here:
https://vanlivingforum.com/Thread-Your-Vehicles-voltage-regulator

While it has been repeated often, basically 'isolators' have a diode in them, to only allow electricity to flow in one direction, from alternator to house battery. this Diode drops the voltage, upto 0.7v, basically ensuring the battery not only charges much slower, but also never gets fully charged. A diode requires a large heatsink, as it is basically wasting energy in the form of heat, energy better off going into the battery rather than the atmosphere.
A simple continuous duty solenoid drops only a few hundreths of a volt at max load or so, try to get one rated for well more than 90 amps continuous. Solenoid contacts do wear out in time. Some advertise silver tungsten contacts which will last much longer and have less resistance. When solenoids fail, usually the contacts fuse together and the driver is usually unaware they now have no battery isolation when engine is off.

The Solenoid does not have to be located in engine compartment. It can be closer to house batteries. I recommend fat red cable going from alternator (+) stud to solenoid to fuse, to house battery, and to ground house battery via same thickness cable to alternator mounting bolt or to (-) stud on alternator if it exists.

The following thread has more info on why This is better than putting the engine battery inbetween alternator and house batteries.

https://vanlivingforum.com/Thread-Battery-setup-diagram-good-to-go

There are many ways to wire this up. My recommendation above of is to achieve maximum alternator recharging.

Also do not idle to recharge depleted batteries for more than about 10 minutes, the alternator can overheat and or wear out much much faster. Driving at speed flushes engine bay with cooler air, and turns the alternator fan faster. It can also produce more amperage at higher rpms.

Some Lesser AGMS say to limit current to 30% of battery capacity, so 30 amps per 100Ah of capacity. If one owns such batteries and the total capacity is such that the alternator rating exceeds that 30%, then thick short copper for maximum charging need not be sought. I feel these 30% limited AGMS can still safely be allowed to feed on more than this, but have not actually owned one and fed it higher than 30% while noting its temperature rise.

But it is a consideration those with less expensive AGMS should be aware of, and not simply ignore.
The higher$$ AGMS (Lifeline, Northstar, Odyssey) can greedily suck up everything most any charging source can supply, upto their absorption voltage, and are better off for it.
 
Nissi said:
Sorry if this was a repeat... I missed other postings.  As I thought this was also a new practice of using the 2nd alternator.
However, evidently lots of folks have been using solenoids/isolators for a while.

I do appreciate your replies, Mike and highdesertranger !!  

Actually wondering about the advantages of the solenoid vs the isolator.  
Found info:  here is one place...   https://vanlivingforum.com/Thread-Battery-Separator-Isolator-vs-Solenoid?highlight=isolators

SternWakes post in that thread answers the question. Stick with a Manual Solenoid. No voltage loss or tricks. 

MIke
 
I would say a single very powerful truck/marine alt with Ext Reg like MC-614 is better than two smaller ones for simplicity.

Focus on charging your House bank, many ways to isolate/combine to top up the Starter.

I'm leaning these days toward low-voltage cutoff the load to keep starter ready to crank, that way a big deep-cycle there could share the House loads, even if only as occasional Reserve.

Unless investing in LFP or Firefly, you'll need solar or regular overnights on shore power for bank longevity.
 
Thanks for all the replies and input...
With 400 watts of solar panels and 654ah of Odyssey AGM batteries
we are in good shape, unless...
cloudy rainy days, northern latitudes in early spring ... one does not
get the charging needed when not plugged in.  The solar panels usually
keep the banks full and charged up, but we need to do better.  

Would love to use an alternator, but, unless someone here knows how
to mount a second alternator in the 4.0L Nissan Cargo van without
getting rid of my AC, I am looking for the next best direction to proceed.
One mention I read earlier on these boards was the FET Isolator, no diode,
so the voltage drop is very minimal.

:shy:
 
Nissi said:
Interesting thought. How can a simple pulley work where a compressor was needed originally...?

Quite well. It is used to maintain proper tension on the belt. I do still need to remove the rest of the AC equipment. Did this with a car years ago, saves a lot of weight, and makes maintenance easier, providing better clearance.
No sense carrying all the useless scrap metal dead weight around.
 
the solenoids are much simpler, more reliable. if you get a good one it will give years of reliable service. I have replaced many, many failed isolators with solenoids. as far as the second alternator do a search for double pulleys. the On Board Air(engine driven air compressor) guys use these. they replace one of the pulleys on one of your existing accessory with a double pulley. this gives you an open pulley to add something to. here is an example, http://endlessonboardair.com/produc...10-209-engine-driven-1-to-1-ratio-onboard-air . don't know if anything like that is available for a Nissian. another way they do it is just find a place to mount it and get a longer serpentine belt. highdesertranger
 
Nissi said:
Why solenoid over the isolator?

The isolator contains diodes, which are essentially one-way valves for electrons.  They permit electricity to flow from the alternator to both batteries, but prevent the electricity from flowing backwards from one battery to the other.  The thing is, there are losses with diodes.  Like approximately .7 of a volt. In other words, if your alternator is putting out 13.8 volts, the diodes only permit 13.1 volts to pass through to the batteries.  The rest of it is converted to heat, which is why the isolator is built with a big aluminum heat sink.

.7 of a volt may not sound like a lot, but it is actually a pretty significant loss.  There are no losses with a solenoid. If the alternator is putting out 13.8 volts,the solenoid will pass 13.8 volts to the batteries.
 
If you kept the original alternator stock and then added a second alternator with 14.8 volt external regulator where the ac compressor use to be how would that effect fuel milage?
 
Actually, there is another more advanced isolator which uses field effect transistors instead of diodes. No voltage drop. I've used one my Peterbilt motorhome conversion for the past seven years with zero problems. Google Jamestown Distributors for more information. More expensive than a solenoid but completely "automatic" and trouble free.
 
Mobilesport said:
If you kept the original alternator stock and then added a second alternator with 14.8 volt external regulator where the ac compressor use to be how would that effect fuel milage?
The HP consumed will depend on the charge demand from the batteries.

A huge empty bank with high acceptance rate chemistry could easily eat quite a high percentage of the engine's output.

Once a bank is mostly full, tail end topping up hardly any.

If you're hauling a heavy trailer in the mountains with a marginal powertrain, risk of overheating transmission etc, would be a good idea to fit an AFD disconnect switch, or otherwise be able to scale back the alternator field current.
 
John61CT said:
Modern FET based isolators are very robust, some military-grade, little to no voltage drops, and much lower parasitic current draws than many traditional solenoids, especially important for example with low-current sources like solar.

Just saying over-generalizations, all depends on your application.

http://www.perfectswitch.com/isolators/

http://www.victronenergy.com/battery-isolators-and-combiners/argo-fet-battery-isolators

Hell Roaring makes a nice one, too.  For almost $200.  Whereas a simple solenoid is only about $15.

http://www.hellroaring.com/products.php

https://www.amazon.com/CONTINUOUS-S...7295&sr=8-2&keywords=continuous+duty+solenoid
 
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