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02-22-2018, 10:48 PM
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#21
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Bus Geek
Join Date: Sep 2017
Location: Owasso, OK
Posts: 2,627
Year: 1999
Coachwork: Thomas
Chassis: Saf-T-Liner MVP ER
Engine: Cummins 6CTA8.3 Mechanical MD3060
Rated Cap: 46 Coach Seats, 40 foot
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02-22-2018, 10:48 PM
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#22
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Skoolie
Join Date: Aug 2017
Location: Phoenix, AZ
Posts: 228
Year: 1997
Coachwork: Blue Bird
Chassis: AARE 3903
Engine: Cummins 8.3L 12v
Rated Cap: 78
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Patron Saint of my workshop:
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02-22-2018, 10:49 PM
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#23
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Skoolie
Join Date: Aug 2017
Location: Phoenix, AZ
Posts: 228
Year: 1997
Coachwork: Blue Bird
Chassis: AARE 3903
Engine: Cummins 8.3L 12v
Rated Cap: 78
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Who knew the hard part would be figuring out how to get the bus up to 88 mph.
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02-22-2018, 11:07 PM
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#24
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Skoolie
Join Date: Aug 2017
Location: Phoenix, AZ
Posts: 228
Year: 1997
Coachwork: Blue Bird
Chassis: AARE 3903
Engine: Cummins 8.3L 12v
Rated Cap: 78
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Here’s the thread on my electrical plans for our Skoolie if you’re interested:
http://www.skoolie.net/forums/f49/so...ins-19206.html
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02-23-2018, 03:53 AM
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#25
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Bus Nut
Join Date: Dec 2017
Location: Southern Maryland
Posts: 505
Year: 1986
Coachwork: Gillig
Chassis: Phantom
Engine: CAT 3208
Rated Cap: 87, says Gillig...
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Quote:
Originally Posted by miscrms
When you connect cells in parallel, then put those into a single series string you only need to monitor / balance each set of parallel cells in the string once. The cells connected in parallel by definition have to all be at the same voltage.
Juan is using 7 sets of 7 modules in parallel. Each Leaf module contains 2s2p cells, with a center tap available for monitoring / balancing. So he only needs 15 lines to the BMS for the 14 “cells” in series. I’m doing 8 sets of 6 in parallel (60v nominal) so I’ll need 17 lines to the BMS for the 16 cells. If I had configured the other way, with 6 separate strings of 8 modules in series I would have to have something like 86 wires to the BMS to monitor balance all 96 cells independently, 14 x 6 internal taps plus the parallel top and bottom connections. If there is even such a thing as a single BMS that can handle 96 cells in multiple strings. More likely I’d need separate 16s bms for each string. Most BMSes require every cell tap to be higher in voltage than the one below it. Putting the lower voltage higher up the chain to start the next string will at best confuse it, and usually blow something up by putting -48v across a device that’s meant for something like 0-5v of a single cell.
Hope that all makes sense.
Still in testing on the bench, but here’s the setup going into my Skoolie.
And a look at the bus bar arrangement and temporary BMS taps. When my Batrium comes in the monitor boards will mount directly to each block of parallel modules.
Rob
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Rob,
While I appreciate your input, please remember that the Volt battery is different; the sucker is electrical, BUT it takes a nuclear reaction to generate the 1.21 gigawatts to make it work...
I was curious as to how Juan could have all those cells but need to monitor so few, and thanks to your explanation I get it, thank you. The Gen 2 Volt battery pack comes with 7 "battery packs" (some 12 cell and some 16) but all the cells in those packs are WELDED in series.
Once I re-configure the pack there will be 8 "48-ish" V batteries. Each Volt cell contains 2 cells in parallel, but again the battery modules are all WELDED in series. So the final 48V configuration will be 2P12S8P.
I don't see how I will not need to monitor all 96 of those cells... Am I right?
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02-24-2018, 04:41 PM
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#26
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Skoolie
Join Date: Aug 2017
Location: Phoenix, AZ
Posts: 228
Year: 1997
Coachwork: Blue Bird
Chassis: AARE 3903
Engine: Cummins 8.3L 12v
Rated Cap: 78
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That sounds right. There’s a lot to like about the Volt cells, but this seems to be the main down side. There may be a way to reconfigure them into parallel blocks, but it looks challenging. What is the cell interconnect, is there a bus bar under there or is it some kind of flex board?
Any ideas on what you would use for a BMS? Seems like a challenging configuration. Brute force of using a separate BMS for each string could get very expensive. Batrium might be able to handle multiple strings on one BMS, but the number of mon boards you’d need would also be $$.
Rob
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02-25-2018, 12:27 PM
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#27
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Bus Nut
Join Date: Dec 2017
Location: Southern Maryland
Posts: 505
Year: 1986
Coachwork: Gillig
Chassis: Phantom
Engine: CAT 3208
Rated Cap: 87, says Gillig...
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Quote:
Originally Posted by miscrms
That sounds right. There’s a lot to like about the Volt cells, but this seems to be the main down side. There may be a way to reconfigure them into parallel blocks, but it looks challenging. What is the cell interconnect, is there a bus bar under there or is it some kind of flex board?
Any ideas on what you would use for a BMS? Seems like a challenging configuration. Brute force of using a separate BMS for each string could get very expensive. Batrium might be able to handle multiple strings on one BMS, but the number of mon boards you’d need would also be $$.
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I may have found a solution. RedWing Lithium BMS is designed specifically Volt batteries. I looks like it even uses the OEM Volt BMS connectors on the packs. I have emailed the seller and am awaiting his response. Based on my research it looks like the seller developed this BMS solution for his own Volt batteries: documented here.
There is a fantastic video on the Gen 2 Chevy Volt battery pack. It is over two hours long but if you jump to ~22:30 minutes into the video he does a review of the individual battery cells and how they are put together.
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02-25-2018, 11:27 PM
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#28
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Skoolie
Join Date: Aug 2017
Location: Phoenix, AZ
Posts: 228
Year: 1997
Coachwork: Blue Bird
Chassis: AARE 3903
Engine: Cummins 8.3L 12v
Rated Cap: 78
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2017 Chevy Volt Battery Pack
That’s very interesting, seems like a good strategy. Basically it just seems like they are using a heavy duty enough wiring harness for the BMS taps that you are essentially tying all the cells at each level of the string in parallel, then monitoring / balancing the single combination. As long as the cells start out fairly well balanced so the initial self balancing current doesn’t overwhelm the harness wiring, which they should be, this should work pretty well. Similarly you’d want to be sure all your cells are of very similar capacity to minimize active current through the harness wiring while in use, but with packs all from the same car the capacity should be well matched.
For that matter you could employ the same idea and use any 12s capable BMS, but there is something to be said for having ready made harnesses available. It’s a clever idea. You still need to tap into every cell, but the BMS requirements are much simplified.
Just keep in mind 12s will be a bit low in voltage for a 48v pack. A lead acid pack would be about 52v fully charged, and not cross 48v until it’s getting empty unless it’s sagging under load. A 12s pack will be around 48-49v when fully charged, and getting down to 42v or less empty. So you’ll just need to make sure whatever equipment you are hooking it up to can tolerate that voltage range.
Rob
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02-26-2018, 02:46 PM
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#29
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Bus Nut
Join Date: Dec 2017
Location: Southern Maryland
Posts: 505
Year: 1986
Coachwork: Gillig
Chassis: Phantom
Engine: CAT 3208
Rated Cap: 87, says Gillig...
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Quote:
Originally Posted by miscrms
That’s very interesting, seems like a good strategy. Basically it just seems like they are using a heavy duty enough wiring harness for the BMS taps that you are essentially tying all the cells at each level of the string in parallel, then monitoring / balancing the single combination. As long as the cells start out fairly well balanced so the initial self balancing current doesn’t overwhelm the harness wiring, which they should be, this should work pretty well. Similarly you’d want to be sure all your cells are of very similar capacity to minimize active current through the harness wiring while in use, but with packs all from the same car the capacity should be well matched.
For that matter you could employ the same idea and use any 12s capable BMS, but there is something to be said for having ready made harnesses available. It’s a clever idea. You still need to tap into every cell, but the BMS requirements are much simplified.
Just keep in mind 12s will be a bit low in voltage for a 48v pack. A lead acid pack would be about 52v fully charged, and not cross 48v until it’s getting empty unless it’s sagging under load. A 12s pack will be around 48-49v when fully charged, and getting down to 42v or less empty. So you’ll just need to make sure whatever equipment you are hooking it up to can tolerate that voltage range.
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Rob, you are the man. I appreciate your feedback on this project; there are not many folks I can turn to that truly "get it". I did get an email from Kelvin at Bobolink Solar. I sent him a novel with my concept for modifying his harness for the new Volt packs. I even included this diagram... Tell me if it makes sense to you.
Regarding the diagram, assume the following:
1) I am capable of cutting the three bus bars
2) OEM BMS ICBs are left intact
3) I am capable of installing six new terminals, three for the "new" 12S module (formerly 16S) positives, and three for the orphan set negatives
4) All BMS wires EXCEPT the group negative for the composite 12S battery could be in the re-pinned RedWing yellow harness
I am in Tokyo thru Sat for work, but I will be calling him next week to discuss. FWIW before I left for Tokyo I checked all 96 cells and everyone was a beautiful rock solid 4.06V.
Also I appreciate your comment on the 48V being not quite 48V and will be taking that into consideration when I finally source the rest of my gear.
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02-26-2018, 03:06 PM
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#30
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Bus Nut
Join Date: Dec 2017
Location: Southern Maryland
Posts: 505
Year: 1986
Coachwork: Gillig
Chassis: Phantom
Engine: CAT 3208
Rated Cap: 87, says Gillig...
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To those who don't get it... I'l give you a hint; it's the Fetzer valve.
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02-26-2018, 03:11 PM
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#31
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Bus Geek
Join Date: Dec 2015
Location: pa
Posts: 2,501
Year: 98
Coachwork: 1. Corbeil & 2. Thomas
Chassis: 1 ford 1998 e350 4x4 7.3 2 mercedes 2004
Engine: 7.3 powerstroke & MBE906
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Happy to see that you are getting it together. As this cells in parallel is what I was asking / suggesting to you a bunch of posts ago .
Good luck,
Later J
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02-26-2018, 07:48 PM
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#32
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Bus Nut
Join Date: Dec 2017
Location: Southern Maryland
Posts: 505
Year: 1986
Coachwork: Gillig
Chassis: Phantom
Engine: CAT 3208
Rated Cap: 87, says Gillig...
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Quote:
Originally Posted by joeblack5
Happy to see that you are getting it together. As this cells in parallel is what I was asking / suggesting to you a bunch of posts ago[emoji3].
Good luck,
Later J
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J, thank you for your help and your patience here in this thread. A few weeks ago I knew literally nothing about these battery packs.
I am working hard to get smarter and will document it all here. Hopefully this thread will help make it easy for the next guy...
I heard someone say lead acid versus lithium is like horse versus car.
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02-26-2018, 08:19 PM
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#33
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Bus Geek
Join Date: Feb 2016
Location: Willamina, Oregon
Posts: 6,409
Coachwork: 97 Bluebird TC1000 5.9
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Well there certainly is a learning curve to using a horse.
__________________
Robin
Nobody's Business
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02-26-2018, 08:54 PM
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#34
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Bus Nut
Join Date: Dec 2017
Location: Southern Maryland
Posts: 505
Year: 1986
Coachwork: Gillig
Chassis: Phantom
Engine: CAT 3208
Rated Cap: 87, says Gillig...
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Quote:
Originally Posted by Robin97396
Well there certainly is a learning curve to using a horse.
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I thought that comment might draw you out, but I think you get the point.
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02-26-2018, 10:26 PM
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#35
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Bus Geek
Join Date: Feb 2016
Location: Willamina, Oregon
Posts: 6,409
Coachwork: 97 Bluebird TC1000 5.9
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Yes, point taken. I do get the metaphore just fine. I still say it's easier to drive a car than ride a horse.
The electrical still goes over my head though. Sounds like a great idea but I'm pretty certain I'd electrocute myself. I like the idea of a large battery pack.
__________________
Robin
Nobody's Business
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02-27-2018, 12:57 PM
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#36
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Skoolie
Join Date: Aug 2017
Location: Phoenix, AZ
Posts: 228
Year: 1997
Coachwork: Blue Bird
Chassis: AARE 3903
Engine: Cummins 8.3L 12v
Rated Cap: 78
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It’s not a bad metaphor IMHO. Lead acid actually has a lot of quirks, but there’s a lot of infrastructure in place to support it and we’re more or less “use to it.” Li-ion introduces a whole new set of quirks and challenges, and there is a lot less infrastructure there to support it. But once it’s up and running well it should be much higher performance with a lot less oversight and maintenance required.
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03-09-2018, 04:53 AM
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#37
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Bus Nut
Join Date: Dec 2017
Location: Southern Maryland
Posts: 505
Year: 1986
Coachwork: Gillig
Chassis: Phantom
Engine: CAT 3208
Rated Cap: 87, says Gillig...
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Okay... While I wait to sort out the BMS solution, I am trying to put together the other main parts of the of the electrical system. I am considering the following components and welcome feedback from our solar/electric SMEs (subject matter experts):
1) Panels - I am considering 8ea of these LG320N1C-G4. They are 320W each, about 40" wide an about 65" long. I would be mounting them per the illustration below. The black squares represent the roof hatches and the red square is where the wood stove will be; BTW could someone please let me know if my images are showing up? I would use a 2S4P configuration producing 67V 37A.
The Charge Controller:I am considering this: VICTRON ENERGY BLUESOLAR MPPT 150/70-TR (12/24/36/48V-70A)
or similar.
The Inverter: Maybe this AIMS Power 6000W 48 VDC to 120 VAC Pure Sine Wave Inverter
The goal is to rarely need a generator (within reason) and keep the Volt batteries happy.
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03-10-2018, 12:03 PM
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#38
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Skoolie
Join Date: Aug 2017
Location: Phoenix, AZ
Posts: 228
Year: 1997
Coachwork: Blue Bird
Chassis: AARE 3903
Engine: Cummins 8.3L 12v
Rated Cap: 78
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Sounds pretty good. I would just be careful about the position of your chimney. You don’t really want anything above the level of your panels that is going to create shade on the panels.
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03-10-2018, 12:14 PM
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#39
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Skoolie
Join Date: Aug 2017
Location: Phoenix, AZ
Posts: 228
Year: 1997
Coachwork: Blue Bird
Chassis: AARE 3903
Engine: Cummins 8.3L 12v
Rated Cap: 78
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Also I’d look at the voltage matching between the panels and the controller. 2s is ~60v Vmp which sounds kind of low for a 48v battery. At 4s Voc is too high for the controller, 3s seems about ideal with those panels? If you want 8 panels you might try to find ones that will fit in under 150v at 4s, or a controller with a higher vmax rating.
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03-11-2018, 07:09 AM
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#40
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Bus Nut
Join Date: Dec 2017
Location: Southern Maryland
Posts: 505
Year: 1986
Coachwork: Gillig
Chassis: Phantom
Engine: CAT 3208
Rated Cap: 87, says Gillig...
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Quote:
Originally Posted by miscrms
Sounds pretty good. I would just be careful about the position of your chimney. You don’t really want anything above the level of your panels that is going to create shade on the panels.
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Good point, I will have to watch out for that.
Quote:
Originally Posted by miscrms
Also I’d look at the voltage matching between the panels and the controller. 2s is ~60v Vmp which sounds kind of low for a 48v battery. At 4s Voc is too high for the controller, 3s seems about ideal with those panels? If you want 8 panels you might try to find ones that will fit in under 150v at 4s, or a controller with a higher vmax rating.
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The deal on the LG panels fell thru. However I found a great deal on these 280W Hyundai panels, and I bought 8 of them (before I read your post, and they only had 8 anyway). About the voltage matching, Vmpp on these panels is 31.7V, Impp is 8.8A, and Voc is 38.5V so:
2S4P = 63.4V and 35.2A (73Voc)
4S2P = 126.8V and 17.6A (154Voc)
In terms of a panel group Vmpp, what would be considered the threshold for keeping 48V lithiums happy? If the 2S4P configuration is not going to cut it, I guess I will have to go with the 4S2P config and a different charge controller?
The Victron MPPT 250/60-TR has built-in Bluetooth so I wouldn't need the $50 dongle, making the price difference only ~$50. Thanks again for your help Rob.
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