Topics

Isolated or not isolated dc-to-dc converter


ERH
 

This seeks installation follow-up assessments from those who installed an isolated or non-isolated dc-to-dc converter in their Navion or View so I and others can assess the risks and advantages   of installing either unit.


Don Phillipe
 

Good luck on this topic ... When I've asked for information along these lines before, most contact me offline with their own story via my personal email address.    Public comments remain missing here I believe because there's a bit of bullying going on to the point that  many will no longer speak out while fearing the headstrong will attempt to squash their experiences as invalid if it conflicts with theirs.   Otherwise It might simply be the fear of Karma driving the shyness, where those who are direct-charging from the alternator may be afraid their luck will change if they make any public statements regarding their success.

When I personally tried tracking down information in this area before, I started over on Sprinter-Source and found exactly what you see here, no one much wants to talk publicly about any direct connection to the alternator.  And again to attempt explaining it, I'm also guessing that most have done it to save money and have elected to simply "see what happens on hope nothing burns out and they may not be too keen on some of the pain that comes along with sharing.

Otherwise try reading this guy's blog for entertainment if you don't any takers.   On his page 10 he provides a great description of how the Sprinter alternator performs so that might be something you are interested in.     I'll tell you now there are people on the road using direct connect to alternator with no repercussions and it's a real shame they are too afraid to speak up.   On the blog, pay special attention to page 10 of his 12 page report.  He's keeping a 400aH lithium setup charged with a direct alternator connection.    In the meantime maybe anyone else doing it will grow a se..... I mean, become brave enough to share their experience with us.

https://windinmyface.com/Sprinter-Electrical.html   (if your read only one page, check out pp 10)
--
Don - 2006 Navion J


David J
 

I did not install a dc/dc converter, isolated or not so I cannot report on this experience. But hopefully my opinion is useful, as an engineer who has designed and produced many power supply systems over the years. I can say that there is no difference in this case. It is not possible to implement an isolated converter if you share a common chassis ground connection.

Mostly I agree with Don that a dc/dc converter is not desirable or required, *if* you have engineered the system properly. It is not a matter of saving money, the goal is to keep the system simple. Something not installed can't fail.


Cal
 

Regarding Don's comment: " When I personally tried tracking down information in this area before, I started over on Sprinter-Source and found exactly what you see here, no one much wants to talk publicly about any direct connection to the alternator."

Can you provide the Sprinter-Source link you are referring to?  Did you post your question?  There are hundreds of threads referencing dc/dc converters.  There's a wealth of info there.

As to the OP question, unless your house battery is isolated from chassis and you want to keep it that way, there's no reason to use an isolated dc/dc.  The two Renogy dc/dc's I'm using (in separate vehicles) have isolated outputs.  My setups don't require isolation and therefore the grounds are tied together.

Calbiker

On Thu, Oct 8, 2020 at 10:50 PM David J <dlj04@...> wrote:
I did not install a dc/dc converter, isolated or not so I cannot report on this experience. But hopefully my opinion is useful, as an engineer who has designed and produced many power supply systems over the years. I can say that there is no difference in this case. It is not possible to implement an isolated converter if you share a common chassis ground connection.

Mostly I agree with Don that a dc/dc converter is not desirable or required, *if* you have engineered the system properly. It is not a matter of saving money, the goal is to keep the system simple. Something not installed can't fail.


Christophe P.
 

Ive had a 300ah lithium battery pack for like 3.5 years and use solar as main charging but occasionally use alternator without dc dc converter. I don’t think you need one unless if you wanna fully charge your battery.
The alternator will only produce a certain amount of amps depending on the temperature and the rpm. There’s a chart on sprinter source as well showing that chart.
Since the alternator voltage is around 14.2v you’ll be able to charge to 95-98% with it without a converter or inverter charger.

Christophe


Don Phillipe
 

Short passage of thoughts:  Why not just hook it up and see what happens, using a battery monitor to see how fast you charge, if you are overloading, and to what percentage SOC you reach in how much time?   It will be easier to add a DC2DC charger later if you can't reach your goals than to realize you made a mistake and then try to get your investment back by later selling the device on eBay.

Long passage of thoughts:  My take is that social media is only very slightly beneficial to the world, while in reality it's nothing but a bunch of opinions floating around and the biggest dog or most popular one or at minimum the one that wins the last dog fight is declared an expert and everyone follows in blind faith (and thus why my constant bad jokes about Insta Pots or recliners to replace dining tables always go over most people's heads)  And not to avoid addressing the link to Sprinter Source for this or that but that seems irrelevant in the same way I am about to describe.  

The only group who would logically know what is going on in this area and to any great extent would seem a professional outfitting company and even with them you have a little bias in that the main way they make money is selling you equipment and installing it.   Then you get into the Youtube "influencers" or "experts" who get paid to sway popular opinion and how much you can really attribute to truth in what they have to offer if money doesn't come from that.   The world's a vast conglomeration of disinformation these days and likely it's always been that way but simply more noticeable today.   (I'm reminded most of this while watching movies dated in the 60's with greased back hair "hi-fi stereo salesmen" and the line of BS they unloaded on the heavy pocketed consumer public back in the 60's-80's and even remembering the age of "monster cable" and gold plated end hi-fi cables that were from China and so impure that solder wouldn't stick to them, leaving the consumer burred in cracking sounds, leaving even some people as they are today, ready to fight when someone make's the point of the foolishness of a particular market-driven over-investment purchase.  No one it seems likes it pointed out that their ego got them in trouble or a scheming salesman played them for a sucker.)

Still to prove my theory, you'd have to ask if anyone here is a retired success story in the outfitting business, someone who has seen and understands it all and who also understands this to the level of being noted an "expert" and even then how they'd be an expert for absolutely everyone's needs.  I'd also wonder why anyone successful in this area would be wasting their time here and offering up their expertise when they can instead be charging hundreds of dollars per hour for consulting and even installing all this stuff as an outfitter.    Such may be the case in the example seen in the WindInMyFace blog and to me I hold a lot of respect for his research and in particular his sharing from outfitter https://automotivedesignsandfab.com/ as noted in some of his references like noted in the link I provide to his alternator info below.

Nevertheless, presenters here seem well informed on what they have personally drummed up as solution and how it operates, so each of those scenarios with their narratives and equipment they've chosen and results as published seems a logical building block in making a decision of what might also work best for you.   The easy route seems to seek a mentor on the same budget and go with their strategy if you don't feel comfortable weighing all the data and forming a conclusion.  In contrast, I'm quite frankly starting to bore myself on this topic but for the interim plan I'm personally going to continue listening here while learning as much as possible.  I do hold high the ton of info  supplied from the WindInMyFace blog from someone who seems to have many good thoughts on the best way to construct these portable power plants.

I probably just hook my initial lilthium setup direct to the alternator via the conventional boost solenoid and after an initial fire prevention check, then keep weighing my needs for change as I gain experience over time, the same as I have done with my lead/acid setup.  So in short I'll just hook it up and see what happens and go from there, keeping an eye peeled on the battery monitor, checking amps delivered over time and SOC attained and make any adjustments from there.  The only thing I believe I need to do then is select a battery type and that may very well be Lithtronics rather than Battle Born.   As an unfounded guess that the 50% upmark over current market price of $ vs aH output, and while observing that people happily pay $1000 per 100aH with BB, this means that is a lot of that price seems to be funding an insurance policy (warranty) as well as fueling the massive marketing push to make BB the first words to roll off the lips of near everyone who's interested in the technology, which oddly sours me right off the bat, but I'm always the odd duck.

Reference to blog of good info and this particular page 10 noting the Sprinter alternator:
https://windinmyface.com/Sprinter-Alternator-Primary.html
--
Don - 2006 Navion J


David Harper
 

Whatever my thoughts on the matter of dc-to-dc converters, I would not risk the humiliation of admitting that I was a sucker to the ad man, or worse yet, a youtube "expert". Truly my only real mistake was buying a View in the first place.

DHH

2008 VJ

On Oct 9, 2020, at 11:59 AM, Christophe P. via groups.io <pqt_chris=yahoo.com@groups.io> wrote:

Ive had a 300ah lithium battery pack for like 3.5 years and use solar as main charging but occasionally use alternator without dc dc converter. I don’t think you need one unless if you wanna fully charge your battery.
The alternator will only produce a certain amount of amps depending on the temperature and the rpm. There’s a chart on sprinter source as well showing that chart.
Since the alternator voltage is around 14.2v you’ll be able to charge to 95-98% with it without a converter or inverter charger.

Christophe





rb3232 atgmail
 

FWIW. I decided to go with this for alternator charging the house 280ah battery  


2007 170 Sprinter 3500
2018 170 Sprinter 2500

6sp2

On Oct 10, 2020, at 02:12, Cal <calbiker@...> wrote:


Regarding Don's comment: " When I personally tried tracking down information in this area before, I started over on Sprinter-Source and found exactly what you see here, no one much wants to talk publicly about any direct connection to the alternator."

Can you provide the Sprinter-Source link you are referring to?  Did you post your question?  There are hundreds of threads referencing dc/dc converters.  There's a wealth of info there.

As to the OP question, unless your house battery is isolated from chassis and you want to keep it that way, there's no reason to use an isolated dc/dc.  The two Renogy dc/dc's I'm using (in separate vehicles) have isolated outputs.  My setups don't require isolation and therefore the grounds are tied together.

Calbiker

On Thu, Oct 8, 2020 at 10:50 PM David J <dlj04@...> wrote:
I did not install a dc/dc converter, isolated or not so I cannot report on this experience. But hopefully my opinion is useful, as an engineer who has designed and produced many power supply systems over the years. I can say that there is no difference in this case. It is not possible to implement an isolated converter if you share a common chassis ground connection.

Mostly I agree with Don that a dc/dc converter is not desirable or required, *if* you have engineered the system properly. It is not a matter of saving money, the goal is to keep the system simple. Something not installed can't fail.


silkear
 
Edited

ok, this is a FWIW post... I am going on 7yrs with 200Ahr of LFP4 batteries and never had an issue with the 180A alternator fully recharging the batteries... now saying that, I monitor the actual output of the alternator with a Hall-effect meter mounted in the cab... I noticed after a round of cold cloudy day running my Espar, comp refirg, and assorted loads, that brought the batteries down to about 20%, that I was drawing around 145amps after starting... of course this dropped down to about 110amps after getting on the road, bottoming out at 40-ish amps while driving 65mph for a few hours... needless to say the batteries got topped off... but if I had started out with the a/c running, that fan can draw up to 25 amps, and it is outside the monitored alternator circuit... so I could be pushing the limits, and cause a failure...

now that is all background for the dc-to-dc converter... after the experience with the loading and due to the age of the rv, I decided to install one of the MasterVolt Charge Mate Pro 40 Charge Divider units and limited the draw on the alternator... and it does a fine job... if I am on a 4 to 5 hour drive it will usually bring the batteries up to  "full"... I also have 350W of solar , so this helps...

to  sum it up, I would go with either the MasterVolt Charge Mate Pro 40 Charge Divider, or the MasterVolt Charge Mate Pro 90 Charge Divider (if you have the 220A alternator) vs. a dc-to-dc converter...

as i said just FWIW, based on my experiences...

John
(Silkear)
08NiQCL
Albuq, NM


ERH
 

John,  Thank you for your feedback experience and data.  Your input helped decide to go with a non-isolated dc to dc converter.  I'm about low risk...I'm an old guy who has experienced low risk failures in business, life, and equipment.  I looked up your recommended MasterVolt charger...nice one. However Im  already in the Victron equipment system (Victron 712 and Victron Multi 12v 3000 watt inverter/charger) so I went with the Victron non-isolated dc to dc converter.   The isolated converter requires additional wiring run; since the House and Chassis already share a common ground, an isolated is unnecessary.
Thanks, Earl  


ERH
 

Don, Thanks for your feedback!    I did look up the blog (pg 10 and others) and was helpful and was impressed with the detail.  I do think I would be fine without a dc to dc converter, but  for $220, I can come close to eliminating chassis alternator equipment failure.  I'm an old guy who requires low risk solutions...not as nimble as I was even 5yrs ago. 
Thanks, Earl  


ERH
 

David J.
Thank you for your engineering expertise feedback.  I went with the Victron Orion non-isolated dc to dc converter.  I ordered from Battle Born (Dragonfly Inc) and also asked why the isolated converter requires a separate ground (I know you know this, but I didn't).  Their rep said because the converter isolates uses a transformer so one must separate the grounds to call the system "isolated."
Thanks,
Earl  


ERH
 

rb3232,  Thank you for your input.  I did consider this isolator; but, went with the Victron non-isolated dc to dc converter.  Thanks, Earl