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InterBlog · 08-13-2017, 04:42 PM

Quote:

Originally Posted by LB_3

...

As for IB's distressing sight of pumping 100 Amps into the battery, it's expected and safe. I didn't necessarily plan to charge from the generator and alternator at the same time but I did size the wiring and heat sink to handle the BMS's rated capacity of 100 charging Amps. ....

Here's the take-away on this point:

If you didn't think to ask the question in advance, then DON'T make assumptions about the answer, especially when dealing with lithium. You know what they say about "assume".

It never occurred to me to ask, or to try to look up what the answer might be. I had an unconscious assumption that, whatever it was, there wouldn't be a scenario in which we would be in danger of breaching it.

But of course three-way simultaneous charging had never occurred to me, so I took the only logical instantaneous action and killed the engine. Better safe than sorry.

TayaraTravel · 08-14-2017, 06:46 AM

Quote:

Originally Posted by LB_3

I'm hoping to add hyperlinks to the PowerPoint with specs and product manuals. But that's down the road a bit and I wish I had a web friendly way to share that and get away from the PowerPoint documents.

I use Google Slides extensively, in place of PowerPoint. It is part of the Google Docs / Google Drive suite of web apps. It like a slimmed down PowerPoint, with all the features you really use.

Here are some value propositions:
* Cloud based, accessible from any device with a browser
* One-button "publish to web" function allows readers to always have access to the latest version, while you control the master copy.
* Easy "download to PDF" function allows creation of a PDF snapshot.
* Export/Import to PowerPoint format (if you must)
* Free

Here is an example: http://bit.ly/hia-msr

I also use Google Docs and Google Sheets in place of Word and Excel.

FlyFishinRVr · 09-01-2017, 02:25 PM

So, I've been having an interesting exchange with a fellow over on the Airstream Facebook group regarding Lithium battery upgrades. He says that his installer isn't putting any current limiter inline with a 400Ah Lithium bank, and he confirmed with AM Solar that they too do not current limit the alternator output in their Lithium installs.

I know you guys and amirm have done a lot of research into this and both of you, I believe, current limit the line going to the Lithiums to the tune of 50A if I remember correctly (using a Sterling battery-to-battery charger).

Given what we know about Lithiums (i.e. they work hard and play hard, and can provide and draw well over 100A to/from a 400Ah bank), it seems either you guys are overly conservative (an approach I like btw), or these other guys are being pretty reckless with the health and welfare of the stock Sprinter alternator.

Can some kind soul please guide me to the light of knowledge on this, because I'm now confusalated.....

InterBlog · 09-01-2017, 06:06 PM

LB_3 notes that we wanted to stay well below the rated capacity of the alternator because alternators don't inherently limit their current and battery charging can represent a very long duration load. Additionally, the alternator puts out 14.2 v and ideally lithiums like 14.6... the Sterling chargers we use bump the voltage up to 14.6 and also limit the current to 60 amps in our case and 120 amps in Amirm's case (he has a different style of BMS). The current-limiting protects the alternator.

Interblog notes that the only other data point I have on this issue is the case of off-grid Sprinter Class B owner journalist Brent Rose, who burned out two alternators inside of a year. I suspect that AM Solar did his upfit but I don't have that info in front of me now. I had an email exchange with him after the second incident and I don't believe that he was using a Sterling. I don't know if he ever had one installed, but it was dawning on him that the loss of two alternators pointed to some issue that required resolution.

amirm · 09-01-2017, 08:37 PM

There are two functions that need to be provided here:

1. Charge limiting.

2. Isolation.

Without #2, the Lithium battery which has higher voltage will proceed to keep charging your chassis battery. You need a one-way valve from alternator to lithium bank, and not the reverse (lithium back to chassis battery).

The type of chargers IB/LB and I use, perform both functions. You can opt to just get #2 but for a bit more money, you can have both.

Back to #1, how much charge is pulled out of the alternator is a function of wiring. If there is enough impedance there, then the voltage drop across it will act as a limiter.

I had measured over 100 amps with the old setup so I knew that with Lithium's low internal impedance, it could suck potentially a lot more than this and I did not want to chance getting stranded with a blown alternator.

So I guess the answer is a bit of both

. Being conservative and solving the isolation problem.

FlyFishinRVr · 09-01-2017, 08:37 PM

Quote:

Originally Posted by InterBlog

LB_3 notes that we wanted to stay well below the rated capacity of the alternator because alternators don't inherently limit their current

That's what I thought too.

Do we know for sure that the alternator in the Sprinter has no overcurrent protection, or is this a supposition based on evidence from people like Brent who seem to be able to fry these things at will? And even if it did have some protection, I assume its response would be to shut down....which is bad, especially when it's generating the juice needed to run the vehicle's electronics.

None of this sounds good. So I wonder why a relatively big and well-thought-of outfit like AM Solar would be so cavalier with their installs? It seems they are creating a situation that, sooner or later, is bound to fail, in a very expensive fashion.....

Hey Lew Farber, our all-knowing and all-seeing 3-eyed raven (yeah, I made a GoT reference, sue me), what do you do in your installs? Do you current limit between alternator and Lithium bank, and if so, with what? TY!

EDIT: @amirm, thanks for the info. It appears we posted at the same time. Unfortunately, your answer only adds to the "WTH?!?!" with respect to AM Solar (and others) doing nothing other than running some (likely undersized) cable from the alternator back to a very expensive bank of Lithium batteries they just sold and "hoping for the best".

InterBlog · 09-02-2017, 05:19 AM

200 AH lithium batteries, 3,000 w inverter, 320 w solar - I just looked it up, and that's what AM Solar put on Brent Rose's 2006 Vista Cruiser (T1N Sprinter). You can read about it at connectedstates.com. I started following him because he was the very first T1N owner I knew of who got lithium.

He was very lucky that neither of his alternator failures resulted in catastrophe. The first one happened in the absolute middle of nowhere. The second one happened in Los Angeles during rush hour traffic. Both times the rig simply stopped working in the middle of the road, dead as a door knob. Especially in the LA case, he could have gotten smashed up.

toskeysam · 09-02-2017, 06:51 AM

Not sure about "current limiting", but Lewster did my lithium battery, inverter, PV panel upgrade....tied the chassis alternator in via a disconnect switch so it's not on unless I want it on. The most I recall seeing it carry was 45-48 amps and then tapering off to essentially zero.

FlyFishinRVr · 09-02-2017, 10:49 AM

Quote:

Originally Posted by InterBlog

200 AH lithium batteries, 3,000 w inverter, 320 w solar - I just looked it up, and that's what AM Solar put on Brent Rose's 2006 Vista Cruiser (T1N Sprinter). You can read about it at connectedstates.com. I started following him because he was the very first T1N owner I knew of who got lithium.

He was very lucky that neither of his alternator failures resulted in catastrophe. The first one happened in the absolute middle of nowhere. The second one happened in Los Angeles during rush hour traffic. Both times the rig simply stopped working in the middle of the road, dead as a door knob. Especially in the LA case, he could have gotten smashed up.

IB do you know what the capacity of his alternator is/was? That level of detail isn't on his web site or video. The gent that I'm discussing this with on FB indicated that his installer and AM Solar would only do this type of install on rigs with 200A alternators, not the smaller 80A alternators, so I'm assuming it's 200A, but we all know what happens when we assume things....

InterBlog · 09-02-2017, 05:51 PM

I believe I asked him at the time, but I don't recall receiving a response.

mineralfarme · 09-02-2017, 10:48 PM

I've been a little concerned about this alternator overload question too. I have 640 amp hours of victron lithium batteries on a 2016 Airstream. I have a 220 amp alternator. It is connected to the batteries with a cable that's fused at 150 amps and I haven't blown the fuse yet but I have seen over a hundred amps flowing from the alternator to the batteries. Everything seems to be working fine I've been told that these modern alternators are self-limiting far as current so that they don't burn themselves up. Not sure how they do it though.

FlyFishinRVr · 09-03-2017, 01:08 AM

Quote:

Originally Posted by mineralfarme

I've been a little concerned about this alternator overload question too. I have 640 amp hours of victron lithium batteries on a 2016 Airstream. I have a 220 amp alternator. It is connected to the batteries with a cable that's fused at 150 amps and I haven't blown the fuse yet but I have seen over a hundred amps flowing from the alternator to the batteries. Everything seems to be working fine I've been told that these modern alternators are self-limiting far as current so that they don't burn themselves up. Not sure how they do it though.

What gauge wire are you running from the alternator back to the Lithiums? I wonder if it's small enough that you're self-limited due to wire resistance.

amirm · 09-03-2017, 10:45 AM

Quote:

Originally Posted by mineralfarme

I've been a little concerned about this alternator overload question too. I have 640 amp hours of victron lithium batteries on a 2016 Airstream. I have a 220 amp alternator. It is connected to the batteries with a cable that's fused at 150 amps and I haven't blown the fuse yet but I have seen over a hundred amps flowing from the alternator to the batteries. Everything seems to be working fine I've been told that these modern alternators are self-limiting far as current so that they don't burn themselves up. Not sure how they do it though.

That's good to know. Since the stock AGM setup also pulls over 100 amps and there are no reports of premature alternator damage, it gives me hope that this setup works as well too.

When I did my conversion, my AI was very new and I sure did not want to turn it into a brick by experimenting.

Your experience gives me hope that it might work without having a charger in between.

What is the system for stopping back charge of the chassis battery from lithiums? Is the Victron isolator in there?

mineralfarme · 09-03-2017, 10:20 PM

Yes, I have the Victron isolator. I think the wire is a 1-0... I can't remember right now.

InterBlog · 09-16-2017, 09:32 AM

At one point on our trip up north, my husband chortled, "I just logged into Air Forums after being offline for the better part of two weeks, and seven of the top nine threads are about electrical issues!"

We got back yesterday, after 5,901 miles and in my case, just shy of a month on the road and off-grid for the entire month (for my conventionally-employed husband it was about 2 weeks as he flew up to join me). I'm in the process of writing a blog post describing what it is to be a *non-retired* person, a working person, not a person of leisure and infinite free time, living off-grid in a van for that duration. I assure you, it's not the nirvana that gets paraded around on Instagram, but for the moment, let me say this much:

Go big or go home, literally. It's so challenging trying to live a life on the road -- which is very different from having a vacation on the road -- that you just can't be messing with all kinds of crap going wrong, especially electrical crap. You'll never get anywhere - you'll spend all of your time chasing your tail. No trip is ever perfect, but what was perfect on this trip was the functioning of our power generation and management systems. It was completely touchless. The van and all its appliances functioned seamlessly for a month, off-grid, with no need for intervention or thought or conscious conservation of any kind. The power was always there, the batteries were maintained automatically, and I / we did whatever we wanted with not a thought to batteries or state of charge or anything else. Every electrical calculation and consideration vanished into the background, mercifully.

So the message is, if you're going to make the decision to do the off-grid thing, the boondocking thing, then DO IT RIGHT. Spend the money. Buy EVERYTHING. Buy lithium and buy solar in addition to an "under-hood generator" (souped-up alternator) because you'd be surprised at how much a good set of panels will contribute to the system. We spent most of our time at 45 degrees north latitude in the month of September and we probably only had about 20% of the daylight hours manifesting with full unobstructed sun, and still, the panels sustained the system on days when we didn't run the van's engine -- and remember, we installed a hungry DC fridge right before we left Houston. Even if you can live without panels, why would you? Having them removes your need to expend mental overhead on maintaining the system. It makes for one less thing to think about within a larger process that is otherwise guaranteed to produce mentally exhausting moments on a regular basis.

Full analysis pending in a blog post.

Boxster1971 · 09-16-2017, 10:47 AM

Great advice from InterBlog. Adding 400 watts of solar with a good controller was best thing I've ever done to my Interstate.

toskeysam · 09-16-2017, 01:35 PM

I'll second that observation. 400 watts of solar, MPPT controller and I've only plugged in once in the last 7 months. 480 ahrs of battery capacity doesn't hurt either.