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Van - 12v, 14kwh lifepo4. Help needed for diagram review.

Time for a little update :) I bought 16 units of the Lishen 272AH 3.2V lifepo4 batteries at the end of january, before chinese new year. They are somewhere travelling by train to europe.

So I'm now looking into the BMS aspect.
For AC charger, inverter, I was so far considering the Victron MultiPlus-II 24v/3000va/70A
24v for safety as I feel more comfortable working around lower voltage.

Looking at the specs for the inverter, I read 2400W for continuous use, 5500W peak
For the battery topology, I was thinking about 8S2P.

Is it a wise choice for my build ?

Am I correct to assume I would need
5500W/24V/0.9/2*1.3 = 165A rating per BMS ?
(Peek wattage / battery bank voltage / inverter efficiency / number of banks in parallel * safety margin)
 
Do you think you'll draw peak surge watts through your inverter? I suspect that most people don't. The max draw depends on the devices you intended to power through the inverter.

The need for a fudge factor (safety margin) depends on the BMS. Some BMS are proving to operate continuously at the rated amps. Some aren't and it has been suggested that many of the cheap BMS should be derated by as much as 50%.
 
Thanks HRKTD for the help.

As of right now, I can't think of any devices that would draw peak surge watts.
So should I then take the continuous 2400W of the inverter to size my BMS?
2400W / 24V / 0.9 / 2 * 1.5 = 83A per BMS (1 per bank)

Something like the JBD 24V 100A ?

So many models that right now, I'm in information overload ^^
What should a newbie look into?
 
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No, take the expected draw of your devices and size the BMS for that, within reason. There's nothing wrong with the calculation you came up with, except that if you're looking at quality BMS devices that are known to operate continuously at their rated output you don't need the fudge factor. If you're planning to buy cheap, unreviewed BMS devices from unreviewed sources then the fudge factor is appropriate.

The Overkill Solar BMS is known to run at it's rated amps and comes with a great warranty. It's the same as the JBD, but you don't get the warranty or customer service with the JBD.

I'm using the Overkill Solar 4s 120 amp BMS. I can't speak authoritatively about other BMS.
 
A little update on my project.

I've decided to go with a 12v system on this van build.

I bought and received:

- Victron SmartShunt 500A
- ET5410 electronic load
- Riden/Ruideng power supply unit.
- 4* 12V 150AH JBD BMS (for a 4S4P battery bank)
bms.jpeg

Next step is cell testing and battery assembly.

For now, I don't plan to buy an inverter as I can power my main 220v load (laptop) with an USB-C 12v charger.
My 220v load might get bigger in a few months up to 2kW.

What should my thinking step be for my wiring diagram ?

1) Calculate max load for each part of circuit
2) Put corresponding and measured safety features. Breaker/Switches..
3) Use appropriate wire gauge for the needed intensity.

Victron has a very interesting guide that I read a few weeks back.

I'll read it again but I would appreciate hints on the wire size I should go for testing the cells.
While the tests go through, i'll have plenty of time to get the wiring right.
 
Wire size is based on three things: amp draw, distance, voltage. Plug those three things into the calculator below and you'll have an answer to how large the wire needs to be. Keep in mind that the calculator wants the distance to be round trip. If the physical distance between two devices is 10' then plug in 20'. That covers both the positive and negative cables.

 
F.Y.I.

Harbor Freight carries #2/0 AWG cables, pair of 3' long (one red, one black) for $36. I was pretty impressed they had these and the price is decent for terminated cables (3/8" terminals).


Keep them short and 2/0 should be fine. Especially for paralleling the battery packs.
 
F.Y.I.

Harbor Freight carries #2/0 AWG cables, pair of 3' long (one red, one black) for $36. I was pretty impressed they had these and the price is decent for terminated cables (3/8" terminals).


Keep them short and 2/0 should be fine. Especially for paralleling the battery packs.
I hadn't bought anyting form there in years, but went in looking for a cheap heavy extension cord to chop up and came out with 2 sets of those inverter cables too. They have been fine.
 
Thank you guys for your hints and links.

According to this bluesea diagram and https://baymarinesupply.com//bosns_corner_wire_sizes calculator.

DC_wire_selection_chartlg.jpg


I've understood the following regarding wiring section. Please critique my understanding.
  • Car battery to DC-DC charger
    • Based on amperage and length (12V, 30A, 32 feet) I should choose either 6AWG or preferably 4AWG.
      But B2B datasheet below says max 6AWG so is 4AWG not possible?
    • Victron B2B charger's datasheet
      • DC connection : Screw terminals
      • Maximum cable cross-section 16 mm² (AWG6)
  • DC-DC charger to positive bus bar
    • 12V, 30AH max
    • 1-2 feet, 8 AWG
  • Individual battery bank to pos bus bar:
    • 12V, 150AH max (as BMS is 150AH max)
    • 1-2 feet, 1 AWG is ok but 2/0 AWG for reduced losses
 
My Victron 100/50 has the same specification on the terminals. I used 6 awg and ferrules. It was tight. I don't think I could fit 4 awg.

The DC-DC 120-12/30 is rated for 30 amps output. The input current may be higher. The spec sheet doesn't say how much higher, but if it was me I would assume 25%. Did you take that into account when using the wire gauge calculator?
 
My Victron 100/50 has the same specification on the terminals. I used 6 awg and ferrules. It was tight. I don't think I could fit 4 awg.

The DC-DC 120-12/30 is rated for 30 amps output. The input current may be higher. The spec sheet doesn't say how much higher, but if it was me I would assume 25%. Did you take that into account when using the wire gauge calculator?
50A is a good number for input current on the Victron Orion 12-12/30.
 
Regarding the size of the wiring going from the starter battery to the Victron Orion 12-12-30AH (output) B2B charger and assuming 50 as input, I get the following voltage drops for 10m/32feet.

1621684966886.png

Victron datasheets mentions 6AWG but in my case it means a 5.42% voltage drop.

I think 4AWG is much more suited. So reading a bit more, i've read about two options

- Set up a long cable run from thestarter battery with a much heavier cable, then step it down to 6AWG very close to the charger with 'power posts' terminals as suggested here : https://community.victronenergy.com...es-for-victron-energy-orion-tr-smart-121.html

- Use a 4AWG cable and trim strands at the terminal.

What do you think?
 
Is 32' the actual distance or the round trip distance? The calculator is expecting round trip distance. Just making sure.

If I fudged the input volts a bit to what you're likely to see in the real world and use 13.6 volts, and switch to a 18 amp output charger with an assumed 25 amps input while still using a 32' distance, it gets me to a 2.4% voltage drop using 6 awg.
 
32 feet is an estimated round-trip distance between the starter battery (under driver feet) and the rear left side wheel well (driver side).

I would preferably try find a solution to maintain a 30A charge from the alternator.
What do you think about running a bigger cable for most of the way and downsizing just to be able to make a connection on the B2B charger terminals? (as explained in my previous post)
 
I would preferably try find a solution to maintain a 30A charge from the alternator.
What do you think about running a bigger cable for most of the way and downsizing just to be able to make a connection on the B2B charger terminals? (as explained in my previous post)

My preference is to use the same cable for the entire run. But I did what you're talking about when it came to running cable from my common bus bars to the main distribution panel (WFCO). 2/0 (way overkill) to within 18" of the panel, then 6 awg (better than OEM) from there to the panel.
 
Hello,

I've drawn the first revision of my wiring installation.
Could you have a look and tell me if something is wrong?

Picture version +pdf in attached file.
Van - Electric wiring with multiplus rev1.png
 

Attachments

  • Van - Electric wiring with multiplus rev1.pdf
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A little update on my project.

I've decided to go with a 12v system on this van build.

I bought and received:

- Victron SmartShunt 500A
- ET5410 electronic load
- Riden/Ruideng power supply unit.
- 4* 12V 150AH JBD BMS (for a 4S4P battery bank)
View attachment 49362

Next step is cell testing and battery assembly.

For now, I don't plan to buy an inverter as I can power my main 220v load (laptop) with an USB-C 12v charger.
My 220v load might get bigger in a few months up to 2kW.

What should my thinking step be for my wiring diagram ?

1) Calculate max load for each part of circuit
2) Put corresponding and measured safety features. Breaker/Switches..
3) Use appropriate wire gauge for the needed intensity.

Victron has a very interesting guide that I read a few weeks back.

I'll read it again but I would appreciate hints on the wire size I should go for testing the cells.
While the tests go through, i'll have plenty of time to get the wiring right.

FYI, if you're going full Victron with the Cerbo or RaspberryPi with Venus OS installed for managing the system there's a driver available that, I think, should work with those BMS's https://github.com/Louisvdw/dbus-serialbattery
 
Thanks for the link. I've come across it in the past. Will try :)
 
Hello,

I've drawn the first revision of my wiring installation.
Could you have a look and tell me if something is wrong?

Picture version +pdf in attached file.
View attachment 51006
Nice system drawing my fellow Van dweller.

I got a Van for the last 5 years, and I rely on Alternator Charging more then anything else - the solar is fine - yet I'm parked in shade more often then not.

I think the 30A B2B charger is small, that takes forever to charge you battery bank. I don't know how often you want to move around - I'm charging with 100A+ and 0/1 Gauge wires into a 12V 400AH battery bank and you got ? 1000ah+ ? Divide that by 30A, (33 hours) that's more then a full day to charge from the alternator.

So in a pinch I can just start the engine and idle for 1-2 hours and got power for another day. I got a 180A Alternator - you have a 150A our - you can get away with a 80A B2B charger.
 
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