Great wiring designs, Li BIM operation, alternator protection/cabling, PV-CC brkr

[VanTalk00]

Just posted a video about all this for my Promaster City build.  Note: I do Youtube videos to gather advice, 
not to attract tons of clicks. I have few subscribers, no affiliate links, no income from Youtube. What I really want is for you
to offer advice in the Youtube comments (or here).

Here is the video.

Thanks,

Jim

 

[Weight]

Post a few of your diagrams. U-Tube takes too much time.

 

[highdesertranger]

you tube also takes to much data. many members don't have the data. highdesertranger

 

[VanTalk00]

you tube also takes to much data.  many members don't have the data.   highdesertranger

I'll try to summarize some of my observations and conclusions.

First, there are some really good sources of info out there with circuit diagrams and good explanations

Nate and Steph from explorist.life  
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Isabelle and Antoine from faroutride.com
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Ken from ourkaravan.com
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Jamie and Lee Blake from Enigmatic Nomadics[/font][font=Roboto, Arial, sans-serif]

Lee Blake Solar Install with Battle Born Lithium Batteries Donation for Lyra - Van Build 2018
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However, even after absorbing all that, you still have to make some decisions on your own.  For example,
I don't have a lot of confidence in DC breakers.  AC breakers have the advantage of extinguishing the interruption arc at a current zero because the current magnitude varies sinusoidally.  You have to interrupt a DC current (no current zero) by lengthening and cooling the arc caused by any DC current interruption. I prefer a fuse that will burn in a safe way until it burns free.  Having said that, you have to be careful in avoiding switching a full DC load current with your disconnect switch.  They supposedly can handle it, but I think it would be hard on them - especially cheap ones.

I really question the need for a DC breaker in the circuit between the PV panel and the charge controller.  The short circuit current from the PV panel in my case (320W ~40 V open circuit) is around 10 amps.  You don't need a breaker or fuse to protect that cable, because no short circuit current can pass through from the low voltage side of the charge controller (according to Victron), and the short circuit current is so small.  Hence a disconnect switch is sufficient.  Even then, I will shade my panel if it looks like I might be interrupting a full load current.

The alternator circuit is also a thorny issue.  I have a 160A alternator, but I'm not comfortable charging a dead coach battery with my alternator.  I think I have enough solar that this will never be an issue, but nevertheless, I'm going to put in a small fuse (100A) until I gain some experience with how my alternator behaves in this circuit.  I'm thinking the alternator will rarely need to do anything but top off by batteries, but I guess we'll see.  So if you assume a light alternator load, and you use the Circuit Wizard to calculate cable size, you can get away with a smallish cable.  The limitation on cable size is the voltage drop you're willing to live with, since it's a fair distance from the engine battery to the coach battery (25 feet, round trip). To avoid all issues, you'd put in a substantial cable (2/0), but that's pretty heavy.  After consultation with Battle Born, they recommended 1/0.  That's plenty big and will insure proper operation of the Li BIM (Battery Isolation Manager).

Speaking of the Li BIM, there isn't much info out there on how it operates, so I got some more info from Battle Born and discuss it in the video. In essence, the BIM connects the engine and coach batteries for a time, then opens the circuit, tests the voltages on both sides, and then decides whether to close the circuit again for some more charging in one direction or the other for another length of time.  You really don't want a lot of voltage drop in the circuit confusing the BIM - especially if you're installing it in the engine compartment, as I intend to do. I've attached the BIM operation sheet I got from Battle Born.

I reference Lee Blake, who discussed the benefits of Kopr-Shield for cable terminations to avoid moisture and corrosion.  Although this stuff is expensive ($28 for 16 oz), in my mind it's better than the hassle of flux/solder.  I also reference the cable stripper they mention in their video, but they don't provide a link for.  I'm using a hammer type crimper instead of the expensive vice-type that Lee has.  Some Youtube comparison videos show it's a pretty good crimp.

Finally, I go over the aluminum box I'm building to locate and mount all the goodies.  The trick is to find a good location for the disconnects and 12 distribution fuses that are out of the way, accessible, have good ventilation, and don't require you to reach into a hot  box (electrically).  Also, I wanted a design that would allow me to extract my expensive Lithium batteries if I'm not going to be in the van for a long period of time in extreme hot or cold.

It's a lot easier to explain in a video, but I appreciate the data access problem.

Thanks,

Jim

 

[gapper2]

Jim, I have also looked at some of those really good sites and have come up with my own system.  I agree about the mechanical breakers.  I'm only using them as mainly quick disconnects from solar panels to charge controller and from charge controller to batteries.  I don't trust breakers with sensitive electronics.   Would be OK for things like a water pump, lights, and maybe a fridge.

I'm in the alternator charging portion of my build and learning new things about alternator charging.  I'm going into it with an AGM battery bank and you are using Lithium.  Both our systems are pretty much "AMP Hogs".  The sheet

 

[Doubleone]

DC circuit breakers do react much slower than fuses.  If you look at a data sheet you'll see they behave more like a thermal breaker.  It's a factor of amperage over time, more amperage equals less time before they trip.  For example, a breaker might pass 150% of rated capacity for a couple seconds before it trips, but at 200% capacity it trips in milliseconds.  The rating of a DC breaker is not a one-to-one exchange with the same amp rated fuse.  So, downsize the amperage rating of a DC breaker according to the data sheet info and intended circuit protection level.  If adding a fuse to a previous breaker application like your solar system you might need to similarly rethink the rating in the other direction.  Trailer light/brake circuits and such are much more tolerant with generic breakers, and essentially self-healing if you experience an intermittent short (at least it'll get you where you're going first).    

As for the alternator charging the dead house batteries... I'd be leery about using an under-rated fuse to limit the alternator charging.  Admittedly its a remote possibility, but consider worst case what happens when the alternator is putting 100+ amps across the circuit and the fuse suddenly opens.  That spike on disconnect could kill a very expensive alternator or other electronics on the vehicle side.  Using the vehicle alternator is less than optimal because of the duty cycle.  Still, I have a continuous duty solenoid wired for jump starting and emergency charging.  It's on a manual switch and I always let the start battery recharge for 20-30 minutes to reduce stress on the alternator before switching over to charge the house.  I rarely use it, I just have it there for emergencies and redundancy.  The best way to do that automatically would be to use a marine charge controller or a high amperage battery isolator that sequentially charges the start battery first and then the house.  I'd also suggest a slightly different fuse set up.  My house batteries are 12v parallel and individually fused at 100 amps solely for short protection.

 

[gapper2]

Gee Jim,  wish I'd known about those excellent sites before I built most of my system.   You also found better prices on those terminal fuse holders.

I agree about the dc circuit breakers.  The only places I use them are from the solar panels to the charge controller and charge controller to the battery and that's just a means of quick disconnect.

I found that the alternator charging puzzle was different than what I imagined.  I connected a dash mounted voltage and current guage and just observed for awhile.  Wide range of voltages and currents sometimes for no seemingly apparent reason.  I would be a little hesitant about putting a 100 amp fuse in the alternator circuit.  I've read over and over that disconnecting the battery while the engine is running will blow the diodes in the alternator.  And also maybe HalfShadow will chime in with his experiece on using a lithium bank with unrestricted current flow and its effect on an alternator as seen here:  https://vanlivingforum.com/showthread.php?tid=34442&page=3
I think your 160 amp alternator is probably sufficient for your described build but my small 105 amp alt won't keep my B2B charger happy.

Sounds like you're tackling your system with a little different philosophy than I am.  My philosophy is to throw as much power at my battery bank with all available sources as fast as possible and let the solar keep things topped off.  Takes much longer with lead acid technology.

Good videos, keep em coming.


I did try to research that Li-BIM 225 unit and their sure isn't much out there.  You might try directly contacting Precision Circuits Inc (the manufacturer) or Dragonfly energy who seems to have some sort of interest in the device if you need more info.  Their are other companies using that device other than Battleborn.

 

[highdesertranger]

"I'll try to summarize some of my observations and conclusions."

posting links to other links isn't explain anything. highdesertranger

 

[Minivanmotoman]

Thanks for the 400+ word, written summary of your observations and conclusions. I appreciated it.
Don't know how any can miss it.

All great stuff to learn from and to hopefully create informative dialogue.

 

[VanTalk00]

I've read over and over that disconnecting the battery while the engine is running will blow the diodes in the alternator. 

You've convinced me to back off putting in a smaller fuse.  Sounds like the greater risk is interrupting the alternator current.  When I went to the owners manual, I didn't see any fuse that could have been construed as protection between the alternator and engine battery, so maybe the manufacturer agrees.  I'll put in a large fuse anyway that I don't expect to interrupt unless there is something clearly wrong.
Thanks,
Jim

 

[B and C]

A fuse is better than a fire even if it blows the alternator. Cheaper to replace the fuse and alternator than fire damage or worse yet, your life. Just fuse for the wire size. There are charts out there.

 

[gapper2]

I believe in my van the manufacturer uses a fusible link in the wire from the alternator to the battery.  The wire is 4 awg at the  alternator and gets small about foot from the battery.  I'm assuming that's a fusible link.  

I have a 200 amp alternator on order to make my B2B charger and me happy.  I plan to add an extra cable from the alternator to the battery and terminate with a large fuse.  I will also have to upgrade the ground side (engine to body I think).  The nice thing about the B2B is it will limit the current from the alternator but I have monitors (temp sensor and V/A guage) and a manual switch to stop the charging of the house batteries from the alternator if I need to.  My Odyssey AGM house batteries will suck in as much as 100 amps from my wiring in bulk mode and I can imagine your lithiums will do more.

 

[Gr8ful]

I was going to mention using a fusable link. Be careful on the cable you buy a speaker cable is copper coated aluminum. I always use 1 size bigger & have a full 2' spool of 2/0 copper welding cable. You can get a device that limits whe amps charginging the house batteries which last a long time if taken care of. Last 6 gold car batteries lasted over 12 years & were still doing fine in a remote hunting camp I did until my son left thhe sysen on over the winter.

 

[Gr8ful]

You need a 12v vurrent limiter which can be a resister & even a light buld for small amp draws. Google & you'll find lots of options.
Also PLEASE DON'T be cheap & use wire that too small. I saw a wireing harness melt on a forklift & don't want that to happen & your insurance won't pay if you cause it to burn from shortcutting to save money. I'd rather you use the frame for the ground if you can't afford the cable size you need.