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The article doesn't say what a "smart alternator" is or does so no way to know if the PM has a smart alternator. If you can define "smart alternator" we can tell you if the PM has one :)

But, you certainly do not need a battery to battery (B2B) charger to charge a house battery with the PM's alternator. A B2B charger would be great and is a superior choice to alternator charging but not certainly not critical.
 

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But it is a good way to get rid of bunches of money either way. A simple solenoid is sufficient and in some ways smarter than either of those because it can be controlled by a human brain!
 

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But it is a good way to get rid of bunches of money either way. A simple solenoid is sufficient and in some ways smarter than either of those because it can be controlled by a human brain!



Lol here we go again! ;):D what you fail to mention is also that why yes they do cost more than a simple switch or battery doctor is they also includes multi stage charging which allows it to charge at a higher voltage than the alternator puts out which like for AGM batteries is suggested to charge at 14.1-14.5 to get to full charge, mine has a built in charge controller which RD has suggest some that cost close to $200 so that eliminates the need for that purchase and it does it all automatically and makes the process easier for the DIY installers.

Now back to the original question. I personally tested my 2016 promaster alternator and found that it is not a smart alternator and the max it puts out for me was 14.1 volts. The DC/DC charger is not a necessity but I do feel it charges the battery to its max full charge and it makes solar hook up very easy and totally mindless. I have a little light on the dash that tells me the unit is working and as long as its lit I know im good to go.



For reference here is the unit I got and I have been problem free for 2 years. https://www.projecta.com.au/dual-battery-charger-idc25

part if the reason we got it was to add solar later but for our needs we found solar to not be unnecessary and have yet to hook it up. when we are out boondocking we drive the van everyday to explore and if we are staying put we are in a campground or at families house and are hooked to shore power. our DC/DC charger charges our single 100 A/H battery very quickly and meets our simple 24 hour 12v needs (lights, phone chargers, 12v tv, 12v maxx fan and 12v fridge freezer). We may get a small 5O watt panel for while the van sits but for now we just plug it in to keep the battery topped of and the inside cool in the summer with the automatic Maxx Fan.

The biggest mistake I think new van builders make is going all out on solar before even knowing if they in fact need solar. if your full time and boon dock a lot than yeah you most likely need it. but if your a weekend warrior like me with full weeks mixed in throughout the year I don't think solar is the way to go but to each there own. Part of me feels the solar thing is some sort of status symbol in the van life.
 

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I agree with all that Charger7022 wrote. The only clarification I would add is that a B2B charger will charge at higher voltage than the alternator puts out (as needed by AGM or other battery chemistries the alternator was not designed to charge) but the current will be limited by the B2B charger. For example I am regularly getting over 30 amps to my AGM camper battery directly from the alternator. That projecta charger maxes out at 25 amps, guessing they might have a version that charges at higher amperage but it will cost more. The promariner (same as sterling) B2B chargers go upto 60 amps but that will cost a bit more. I too found that I have yet to encounter a situation where I need solar since I drive the van daily and AGM batteries charge very quickly from the alternator, but Im not using coffee makers and microwaves in my van either. No doubt about it, solar is a status symbol, whether its on the roof of your home or the roof of your van. I need more battery capacity the most when winter camping in heinous weather and snowstorms and that is the time that solar will be least likely to help. On the other hand, solar is so cheap now I will probably add some to my van as a geeky "science experiment" and I think its a good doomsday/long term power outage tool to have at home.
 

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I agree with all that Charger7022 wrote. The only clarification I would add is that a B2B charger will charge at higher voltage than the alternator puts out (as needed by AGM or other battery chemistries the alternator was not designed to charge) but the current will be limited by the B2B charger. For example I am regularly getting over 30 amps to my AGM camper battery directly from the alternator. That projecta charger maxes out at 25 amps, guessing they might have a version that charges at higher amperage but it will cost more. The promariner (same as sterling) B2B chargers go upto 60 amps but that will cost a bit more. I too found that I have yet to encounter a situation where I need solar since I drive the van daily and AGM batteries charge very quickly from the alternator, but Im not using coffee makers and microwaves in my van either. No doubt about it, solar is a status symbol, whether its on the roof of your home or the roof of your van. I need more battery capacity the most when winter camping in heinous weather and snowstorms and that is the time that solar will be least likely to help. On the other hand, solar is so cheap now I will probably add some to my van as a geeky "science experiment" and I think its a good doomsday/long term power outage tool to have at home.

Spot on. yeah mine only charges at 25 amps max and now they make one that's 45 I think. but in my testing the battery I have it will only take so much even when 50% depleted and never has it drawn the max amps. if you have a larger battery bank than yeah I think you might get a higher amp draw but for 1-2 batteries I think the 25 amp is plenty and charges mine quickly.
 

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The solar is no more necessary than the alternator interconnect but we all should have both. It can charge AGM, GEL and FLA batteries properly. I’d suggest the B2B and Projecta stuff is what is what is probably not necessary. I don’t have them and for some unexplainable reason seem to be doing fine. Remember the solar, added to an existing electrically equipped van, is about $250- not a big expense, and it is Magic!
I just went through 8 days of mostly rain and interconnected to the alternator only 2 mornings. The human brain worked great (even mine!)
Save a bunch by doing the solar FIRST along with a switched solenoid and if it doesn’t work upgrade to the B2B and Progecta. You will be out $15 but I’d guess you will never need more.
 

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...Does a PM have a "smart" alternator?
I'd say no.
I read that website and I think they are referring to alternators that have external control from the engine computer - not just a simple voltage regulator like the PM. Smart alternators are becoming common in european vehicles. The idea is to reduce the alternator output when the vehicle does need it to increase efficiency. Not sure what logic schemes they are using (I can think of at least 3). Or, it can be something like the new RAM pickup mini-hybrid where the alternator does regenerative braking and returns the power back to the vehicle by switching to motor mode on acceleration. I think GM did some if these a decade ago.

The reason some B2B chargers wouldn't work well with a smart alternator is that the B2B has built-in voltage sensing like a VSR and they would discontinue charging when the voltage drops below a threshold. If you read the info on the Sterling units it clearly describes the function. If they didn't do that, the charger would be capable of completely draining your starting battery while you use your house battery.

I was looking at the CTEK D250SA recently because it combines an MPPT solar charge controller and B2B charger in one unit. Unfortunately, their online manual is a joke and they don't clearly explain how the B2B side works. It simply states the input voltage range is 11.5 - 23V. I tried to ask their tech support if it can drain the starter battery (11.5V is basically dead) and they gave me a canned response with no real explanation like "it cuts out at X voltage". It does have a smart alternator input that you can hook to ignition but I don't know if you can use this to prevent discharging your starter battery if the engine is not running. Don't feel like dropping $270 (actually not that bad for combined MPPT controller and B2B integrated together) just to find out how it works myself. I don't plan to use solar initially and I don't want to wake up to find my fridge and CPAP have drained my starter battery. Better to just have a manually controlled relay as RD suggests. However, the downside is you may not get a 100% charge in your house battery if the alternator only puts out 14.1V as other report.
 

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The solar is no more necessary than the alternator interconnect but we all should have both.
I disagree, we all should have alternator connection but solar is not for everyone. we all have different needs and for full timers boondocking a lot than yeah solar may be a must. I'm sorry I just see to many people starting their build with tons of solar cause its the "cool thing to do". I'm fully wired for solar and had every intension on putting panels on the roof from day one over 2 years ago but I am still waiting for that time when my battery (yep just one) dies and I say man I wish I had solar. haven't even found the need for a 2nd battery which I also prepped for.
 

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I have had the Sterling B2B in my 2500 2017 promaster for 6 months. https://sterling-power.com/products/2015-battery-to-battery-chargers-non-waterproof-drip-proof-ip21 .. It is the old 30 amp model which is now just about gone from the market. I would purchase the 60 amp version now. I like Sterling products because their manuals nerd out. Here are the numbers (estimates) floating in my head. The promaster alternator can put out around 100 amps at 100% duty cycle. It can charge the promaster battery in about 30 seconds after starting .. but this is a peak charging situation. The VAN starter draws about 250amps in the few seconds it is starting. There are spikes/surges from the starter motor both when turning on and turning off. Regenerative breaking is complicating this. The ECU's are beginning to fine tune when to kick the alternator off and how to handle the surge of energy coming from the brakes. The Sterling products sense alternator/regenerative braking voltages that are higher than the batteries. (batteries run lower than 13 volts, alternators and regenerative breaking run higher). Sterling kicks off when it senses anything other than the alternator steady state, 100% duty cycle situation.

All solenoids do is turn on when the voltage gets high enough, and turn off when the van is turned off. Hold in current is a lot weaker than turn on current. I don't trust them. The worst case scenario is that the auxiliary batteries are discharged, while the van is off. The promaster is turned on, the solenoid has no circuit breakers that limit current and the cold start 1000 cranking amps surge from the VAN battery to the aux batteries, causing cables to melt, damage the promaster battery, max out/damage/age the alternator, shoot up the engine RPM, gas the AUX batteries, the promaster catches on fire and I escape losing my sense of smell. (It's close to Halloween, time for a nerd horror story).

The sterling stops this by limiting it's maximum current draw to 30amps (1/3 of the steady state, 100% duty cycle of the promaster alternator). The promaster doesn't know the sterling is there! This means the batteries don't charge very quickly (I have four). Essentially the Sterling is a trickle charger .. with all of the trickle charging benefits. The drawback is slow charging. I ran a 300 watt computer with two monitors for about 4 hours a day for a week, plus some power tools this summer. It took about 4 hours of driving to recharge the batteries. My definition of recharge is that they hold 12.6 volts.

Starter batteries are designed to be fully charged 100% of the time. Just sitting they discharge through the moisture in the air. The Sterling is "on" immediately after turning on the van. So even when I drive 10 minutes, it is replenishing the batteries. The goal of my solar panels will not be to charge the batteries but to top them off continuously .. the same goal as a trickle charger.

When the promaster turns on, the Sterling powers up and inspects the batteries. It then decides what to do. It is capable of a 4 stage lithium battery charging cycle. It has 8 different charging cycles for different lead acid batteries. It defaults to the calcium starter batteries. It gradually starts charging. It stays on after the VAN is turned off to gradually stop charging. Say the Sterling is putting out 13.2 volts, 13.1 volts are reaching the batteries and the promaster is turned off. The Sterling senses the 14 or 15 volts of the alternator disappearing. It takes the 12.6 volts of the promaster battery, boosts it up to 13.2 and then over a 3 minute period gradually drops the voltage down to whatever the aux batteries are holding and then turns itself off. You can hear the sterling fan kick on when it is boosting. I love the sound. It lets me know everything is working!

A solenoid has one wire coming from the promaster battery and one wire to the aux batteries. It has a ground that has to enable the hold in current. This is usually a nearby chassis ground. The Sterling says "locate as close to the promaster battery as possible." Run both ground and power to it. This is because it wants the cables the same length. It wants to know what the promaster alternator/battery is doing as accurately as possible.

Everyone likes to talk about batteries in terms of their capacity, time to charge, how charged up are they, etc.

But the reasons batteries stop working is because people don't understand the problems of energy surging through cables and between batteries. These are the issues that determine system lifespan. With the Sterling I am in not worrying. (But I check them almost every trip, just because it is fun.) My kids have a left and have families of their own. Batteries are now my pets. I am now studying desulfation. The Sterling has a setting that puts a large voltage (15+) across the batteries in a maintenance procedure that pushes the sulfur collecting on the battery plates back into the water. Me and my batteries are going to live forever!
 

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...I agree, they are not "smart", but they do seem to charge the factory AGM starter battery OK.
I just checked mine at the Battery Dr.

Before starting:
Main (stock) Battery: 12.61 VDC
Auxiliary: 12.96

Started it, didn't rev, and tested it a few seconds later: 14.33 VDC

I agree with these simple statements... if the van battery is AGM, why wouldn't a BD (or slightly cheaper RD solenoid) charge the aux AGMs... works fine with my 2 aux AGMs


.
 

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I agree with these simple statements... if the van battery is AGM, why wouldn't a BD (or slightly cheaper RD solenoid) charge the aux AGMs... works fine with my 2 aux AGMs


.

Before I switch from battery doctor to my Projecta unit I did a little test and its reported here on the forum somewhere. with the battery fully charged with the battery doctor after some time I took voltage reading than after installing the projecta and letting it charge the battery after the same amount of time I had a slightly higher voltage reading with the projecta. It seems to be that for whatever reason I get a better charge with the Projecta than I did with the constant 14.1 volts all the time with the BD. Im no Pro so take it for what its worth but that was my findings. does the simple solenoid and BD work? yep they work and do the job
 

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I'd say no.

I was looking at the CTEK D250SA recently because it combines an MPPT solar charge controller and B2B charger in one unit. Unfortunately, their online manual is a joke and they don't clearly explain how the B2B side works. It simply states the input voltage range is 11.5 - 23V. I tried to ask their tech support if it can drain the starter battery (11.5V is basically dead) and they gave me a canned response with no real explanation like "it cuts out at X voltage". It does have a smart alternator input that you can hook to ignition but I don't know if you can use this to prevent discharging your starter battery if the engine is not running. Don't feel like dropping $270 (actually not that bad for combined MPPT controller and B2B integrated together) just to find out how it works myself. I don't plan to use solar initially and I don't want to wake up to find my fridge and CPAP have drained my starter battery. Better to just have a manually controlled relay as RD suggests. However, the downside is you may not get a 100% charge in your house battery if the alternator only puts out 14.1V as other report.
Ive been using the predecessor to this unit for several years 250DS It's an all in one unit, works as a VSR, multi stage B2B charger and MMPT solar controller. It will NOT drain your starter.
 

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If you want to geek out about battery stuff check out this website: https://marinehowto.com/
The author has a lot of very good info and experiments he has conducted on 12 volt charging systems and batteries.

A third house battery charging option that has not been presented here is charging the house batteries via a dedicated 110v charger powered by an inverter. I call this the "orton diy" method, well documented here: http://www.ortontransit.info/electric.php
 

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If you want to geek out about battery stuff check out this website: https://marinehowto.com/
The author has a lot of very good info and experiments he has conducted on 12 volt charging systems and batteries.

A third house battery charging option that has not been presented here is charging the house batteries via a dedicated 110v charger powered by an inverter. I call this the "orton diy" method, well documented here: http://www.ortontransit.info/electric.php
A lot of needless, expensive, unnecessary equipment to do what a simple relay will accomplish for most people. There have been next to NO problems with people keeping their FLA & AGM house batteries charged by solar and supplemental charging via a solenoid and the alternator other than those who have mis-wired, used undersized cables, etc.

I do it constantly as many others here also do. Why make simple things so confusing and complicated for newbies?
 

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A lot of needless, expensive, unnecessary equipment to do what a simple relay will accomplish for most people. There have been next to NO problems with people keeping their FLA & AGM house batteries charged by solar and supplemental charging via a solenoid and the alternator other than those who have mis-wired, used undersized cables, etc.

I do it constantly as many others here also do. Why make simple things so confusing and complicated for newbies?
Some of the "simple and cheaper" options I have seen proposed in the forum might work because they have far more capacity (more batteries and redundant charging) than are needed. Thats not a bad thing and batteries and solar are cheap. In my case I am trying to keep the battery capacity to a minimum for space, weight, and cost savings. Especially since batteries are a wear item and need replacing. I dont have a B2B charger or solar, dont need either, too cheap to buy and too lazy to install unless I find that really need either. I have 100 AH AGM charged via solenoid/alternator, a victron battery monitor, and promariner 20 amp 110v charger. Since I drive the van daily and have minimal electrical uses, Im finding that this is all that I need, I would not know that this is all that I need without the battery monitor. That doesn't mean I don't find this stuff interesting or want to know how it works.

For the record, newbies should ignore this thread and read RD's $700 complete electrical system thread instead. :)
 
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