Motorhome Solar + 24V LiFePO4

[Demosthien]

After scouring through various posts and reading quite a few blogs etc I've decided to switch my original plan for a system with lead batteries for a LiFePO4 setup instead.

Background: This system is for a motorhome we're building. I've got enough space on the roof for two solar panels (parallel) but might be able to get a second pair (a total of two parallel pairs) up there with a bit of ingenuity. Because of the size of the truck the cabling needs to cover some decent distances and the truck battery is 24V. So, to help with potentially installing a battery-to-battery charger later and to avoid having to run heavier cable than necessary, we're sticking with a 24V system throughout with 12V converters at "Node" points whenever they're needed.

I'd greatly appreciate any feedback people can give me on the layout (link below). I've also got a couple of specific questions too.

1. Should the Inverter be located after the Victron BP220, as it is in the diagram, or should I seperate its MCB from the group and put it on its own positive (out from the load shunt)?
   
2. Is the 230VAC battery charger's positive situated correctly with regard to the charge shunt (via the MCB block and the charge busbar)? I have seen some layouts place the battery charger positive after the charge shunt.
   
3. I've read that using a Class "T" fuse off the battery is the safest option, is this correct? What would be an appropriate fuse to use here?
   
4. I recall the SBMS0 doesn't like anything to disconnect the positive line before the shunts so that means fusing the negative as shown is the way to go?
   
5. What would be the effect of grounding this setup to the chassis? Should that happen from the negative busbar or from another point on the system?
   
6. Do I need to consider grounding the 230VAC in any way? It should ground via the earth cable whoever we're connected to shore power, but then the generator won't be so I guess I have to look at how that will work? I suspect inverters have their own special ways of dealing with grounding which will be explained in the manual.
   

https://drive.google.com/file/d/1So9xevUCDrUTswlG_chj2vjZikzAJv8Y/view?usp=sharing

[Dacian Todea]

1. Since is just an 1200W inverter you may get away with connecting to the BP220 but ideally you will want that directly connected.

2. The charge shunt is not correctly connected should be in series with the battery shunt and so after the battery shunt see diagram at page 3 in the SBMS0 manual.

3. You can not have a single fuse completely disconnecting the battery from both charge sources and loads.  So suggestions is to have them on positive side after the current shunts one for Loads and one for charge sources else if that one single fuse where to get damaged the Loads and sources will remain connected together and without a battery is very likely some will get damaged.

4. Your shunt will be next to the battery likely in an electrical box followed by fuses and or breakers thus since in that box there is no negative you can not have a short inside the box before the fuses or breakers.

5. As you do not seem to charge from alternator is your choice if you want to have the negative of the 24V connected to battery or just leave that isolated.

6. Generator as well as you motorhome are not referenced to GND so no ground protection is needed. When connecting to grid power you can either use an isolation transformer keeping the entire system isolated or you will need to have th grid earth ground connected to your vehicle (but I do not know what the rules are there). 

  

[Demosthien]

Thanks for the reply Dacian! I've made some changes to the layout (PDF attached), as per your feedback, and have a couple of questions/comments (in blue below) to follow up from your previous reply.

Thanks again for your help!

On Thursday, 25 June 2020 02:26:14 UTC+1, Dacian Todea wrote:

1. Since is just an 1200W inverter you may get away with connecting to the BP220 but ideally you will want that directly connected.

I've now adjusted the Inverter feed so that it comes off the load positive before the BP220.

 

2. The charge shunt is not correctly connected should be in series with the battery shunt and so after the battery shunt see diagram at page 3 in the SBMS0 manual.

The two shunts and the positive line for the load have now been adjusted in accordance with the diagram in the SBMS0 manual.

 

3. You can not have a single fuse completely disconnecting the battery from both charge sources and loads.  So suggestions is to have them on positive side after the current shunts one for Loads and one for charge sources else if that one single fuse where to get damaged the Loads and sources will remain connected together and without a battery is very likely some will get damaged.

I'm not 100% sure what you mean here, sorry.

I've got MCBs on the DC load wires which should handle any over-current/short-circuit issues for those wires but there is no over-current/short-circuit protection between the battery and those MCBs. As you noted in #4 below there is a very limited possibility of a short-circuit/over-current here because of how short the wires are, but that doesn't mean it can't happen. I might be wrong but, without adding a fuse to either the negative or positive (close to the battery) then there is no protection for those wires (As noted in the link below at the section on Over-Current Protection). at the section on Over-Current Protection). at the section on Over-Current Protection).

For example, in the diagrams that Dhowman created he has used MRBF fuses directly on the negative terminal of his battery and then has a DPST rotary switch immediately after (but only disconnecting two negative wires from the battery).

https://marinehowto.com/lifepo4-batteries-on-boats/

 

4. Your shunt will be next to the battery likely in an electrical box followed by fuses and or breakers thus since in that box there is no negative you can not have a short inside the box before the fuses or breakers.

You're correct, much of the setup will be located within a small closet/box approx 1m x 0.5m so the wire runs will be very short and there is a very small chance of a short before the MCBs... But (as noted in #3 above) it is still possible, hence my concern as I don't want a sudden catastrophic discharge. If I'm over-thinking this then pease let me know.

5. As you do not seem to charge from alternator is your choice if you want to have the negative of the 24V connected to battery or just leave that isolated.

There will be no alternator charging, only the solar, mains "shore" supply, and the generator. The "house" electrics are currently completely seperate from the "truck" electrics. At some stage I *might* look at installing a battery-to-battery charger to allow the truck or house battery to be used to charge each other, but that is currently just an option for future consideration.

I assume that if I chassis ground the house electrics from the negative busbar then the truck and house will no longer be fully isolated (because the truck is already chassis grounded), but that should have no affect on either electrical system.

 

6. Generator as well as you motorhome are not referenced to GND so no ground protection is needed. When connecting to grid power you can either use an isolation transformer keeping the entire system isolated or you will need to have the grid earth ground connected to your vehicle (but I do not know what the rules are there).

The generator is not referenced and wont need to be grounded? Good, that's what I thought.

I'm in the UK so mains shore power has it's own earth (three pin plugs/sockets - live/neutral/earth) which is connected to the battery charger via the "230VAC Magic Switch Box" (which is essentially just the MCBs/RCCBs and a rotary switch (make/break/make) for selecting the shore or generator feed and a couple of LEDs to give visual indications of which source is live). I'll be posting the layout of the "230VAC Magic Switch Box" for critique once I've got the DC side of things sorted.

[Demosthien]

Oh, one last thing I forgot to mention in the above reply was about the 230VAC battery charger... I'm looking at the Victron Phoenix Smart IP43, it charges LIFePO4 batteries and has a remote function (High/Low) which I assume would be controllable by the SBMS0 in the same way that many other Victron products seem to be?

If it is controllable, what would it need to be connected to on the SBMS0? EXTIO4 so it is turned off with the same signal as the DSSR20s?

[Dacian Todea]

1,2 OK

3. If for some reason that single fuse on negative gets open circuit you can be in a situation where chargers open circuit voltage as high as the panel open circuit voltage maybe 38V or more will end up on the Load's (inverter and all other DC loads as the battery is out of the circuit and so voltage can no longer be maintained). So you should have separate paths and breaker's for Loads and chargers.

Best way (simple way) to do that is to not have any fuse on the negative and have a main fuse on the load side immediately after the battery shunt (Load shunt) and another one on the charge shunt before that rotary switch.

If the current shunts are next to be battery in an electrical box including the two fuses one for loads one for chargers then no matter where you have a short one of this will open the circuit so there will never be a condition where loads and chargers are connected together without a battery.

4. The idea as mentioned at point 3 is that you make it impossible for a short to happen by enclosing the shunts and fuses in a box thus the short can only happen outside the box as inside the box there will be no negative wire just positive.

Yes I think the Smart IP43 can be controlled by the same signal as DSSR20.  You will have EXT IO4+ connected to battery+ through a resistor and then EXT IO4- will connect to both the H remote signal on the IP43 and the batt signal on the DSSR20 

  

[Demosthien]

On Saturday, 27 June 2020 21:05:20 UTC+1, Dacian Todea wrote:

1,2 OK

👍

 

3. If for some reason that single fuse on negative gets open circuit you can be in a situation where chargers open circuit voltage as high as the panel open circuit voltage maybe 38V or more will end up on the Load's (inverter and all other DC loads as the battery is out of the circuit and so voltage can no longer be maintained). So you should have separate paths and breaker's for Loads and chargers.

As an alternative to the option below... How would I keep the paths etc seperate? Would you need to connect the charge side positive to a different battery terminal to the one where the load side positive is connected (I figure this would cause all sorts of issues of unbalancing the battery cells so not the best option)? How else would the paths etc be kept seperate?

 

Best way (simple way) to do that is to not have any fuse on the negative and have a main fuse on the load side immediately after the battery shunt (Load shunt) and another one on the charge shunt before that rotary switch.

If the current shunts are next to be battery in an electrical box including the two fuses one for loads one for chargers then no matter where you have a short one of this will open the circuit so there will never be a condition where loads and chargers are connected together without a battery.

OK... So remove the negative terminal fuse and add positive fuses where the arrows are pointing in my dodgy picture below? 

 

4. The idea as mentioned at point 3 is that you make it impossible for a short to happen by enclosing the shunts and fuses in a box thus the short can only happen outside the box as inside the box there will be no negative wire just positive.

👍

 

Yes I think the Smart IP43 can be controlled by the same signal as DSSR20.  You will have EXT IO4+ connected to battery+ through a resistor and then EXT IO4- will connect to both the H remote signal on the IP43 and the batt signal on the DSSR20 

Great.

Thanks again for the support!

[Demosthien]

Hang on a second!! I think I made a mistake earlier.

On Sunday, 28 June 2020 15:35:35 UTC+1, Demosthien wrote:

OK... So remove the negative terminal fuse and add positive fuses where the arrows are pointing in my dodgy picture below? 

This is wrong isn't it! The fuse nearest the load shunt isn't going to work properly. If that fuse blows then the problem you suggested earlier (see below), where the panel's open circuit voltage would then end up on all of the loads, would still occur!

 

3. If for some reason that single fuse on negative gets open circuit you can be in a situation where chargers open circuit voltage as high as the panel open circuit voltage maybe 38V or more will end up on the Load's (inverter and all other DC loads as the battery is out of the circuit and so voltage can no longer be maintained). So you should have separate paths and breaker's for Loads and chargers.

So I should move this fuse further along the load positive past the junction? See attached PDF update.

[Dacian Todea]

Yes the last diagram looks correct.

[Demosthien]

Alllllllrighty then!!

It's time to start buying some more hardware. 👍

Finger's crossed when I build it nothing catches fire. 😳

[Dacian Todea]

It will be hard to work with finger's crossed so I suggest against doing that :)

[Demosthien]

Good advice... I will follow it! 😂

[Demosthien]

Thinking a bit more about the DSSR20 and the 230VAC battery charger, and wondering if the ON/OFF signal to the battery charger would be adversely affected if I were to insert a DEXT16 into the EXTIO4 line?

I reckon there are two good reasons for adding a DEXT16;

1. Future proofing... I may at some stage decide to try out diversion heating so might get the DSSR20/Diversion in the first instance so they're already in place.
2. Cable management... The DEXT16 will help to keep the cabling tidier when trying to control all these different devices.

[Dacian Todea]

Not sure what model that charger is and what sort of remote ON/OFF it requires.

[Demosthien]

Sorry! It's the one I linked earlier, the Victron Phoenix Smart IP43 Charger... Here's the spec pdf.

[Demosthien]

The manual states;

4.11. Remote on-off There are three ways to switch on the device:
1. Short the L and H pins (factory default)
2. Pull the H pin to a high level (e.g. the battery plus)
3. Pull the L pin to a low level (e.g. the battery minus)

I assume just doing the opposite of either 2 or 3 and it should turn off? So, unless the DEXT16 does something to the SBMS0 signal on EXTIO4, there should be no issue?

[Dacian Todea]

Sorry, Yes I remember and that will work just fine together with DSSR20's as you will be using just the H connection from the remote port.

[Plamen]

Just looked at that charger manual, it says 210-250V AC Input and 290-355V DC Input. Couldn't find more info on that. If DC Input is used, is it supplied by the same line as AC?

[Dacian Todea]

Plamen,

As any AC to DC charger you have a bridge rectifier and then a DC to DC converter so all of them could work on high DC voltage as the input. It is just a matter of the bridge rectifier to be sized so that it can handle the DC as only half the bridge will be used with DC vs AC.

[Plamen]

   Thanks Dacian!

[Demosthien]

I'm curious about the way the Solar+DSSR20 charging will work with a mains battery charger (see attached diagram, ignore the specs noted as they're not correct).

Let's say hypothetically the modules are supplying up to ~45VDC + 30A and the battery charger is supplying ~28VDC + 25A at the same time. In the diagram the modules and the charger are all feeding into a single busbar which then supplies the battery.

How does the voltage mismatch between ~45VDC and ~28VDC affect the actual battery charging? Do the panels get dragged down to the ~28VDC the charger is supplying or do the panels pull the charger up to their potential?

Would it be a better layout to have a switch to select which of the two charge supplies should be active or is it ok for them both to supply at the same time?

In reality I suspect the panels will not be supplying that ~45VDC amount at all but will probably actually end up closer to the ~28VDC the charger is supplying but I'm curious.

[Dacian Todea]

On that busbar you will always have battery voltage whatever that will be maybe around 27V

Chargers either PV panels or AC/DC chargers are constant current sources so they will put out the current but voltage will be equal with battery voltage.

So yes both the PV panels and the charger is dragged down to 27V or whatever the battery voltage is at that point.

Your battery is large enough 280Ah if I remember correctly to handle both the PV and AC/DC charing at the same time about 60A max.

[Demosthien]

Great. Thanks for the explanation Dacian. I hadn't considered the battery voltage, but that certainly makes sense to me now.

[Renatazbyszek]

What about fuse/breaker for inverter, is not shown?

[Demosthien]

I've been working on the diagram a bit and have made a few changes but the current design is still pretty much as it is there.

However, in the V3.0 diagram linked above; the inverter is protected by a DC-MCB (miniature circuit breaker), in that diagram it has no Amp rating yet but it will be 100A. You can see it in the bank located above the Load Busbar (the inverter one is seperate from the rest). The feed for the inverter will travel through the primary load cable and fuse (which will both be more than capable of handling the inverter load plus all the other DC loads). After that the cable will split and go to both the Inverter's DC-MCB and the Victron BatteryProtect (from the BatteryProtect he cable feeds the other DC-MCBs).

[Barry Timm]

n't recall seeing the make/model of the inverter, but am curious why you don't go with a single Victron Inverter-charger instead of the dedicated inverter and separate DC charger? Victron makes it very easy to manage both loads and charging separately. Any specific reason to go with two units?

[Demosthien]

The inverter is a 24V 800W Phoenix.

The charger is a 24V Phoenix Smart IP43.

There are a couple of reasons for keeping the inverter and charger seperate...

1. Damage Control: If one goes "puff" the other isn't out of commission until we get a repair/replacement.

2. Price/Capacity: The inverter and charger we want/need were cheaper separately than as a combined unit.

3. Future: Should we decide to upgrade our inverter capacity in the future we aren't forced to buy another combined unit, we can just upgrade the inverter.

[Rob Duncan]

Demosthien - Since I have done this 24V conversion may I offer these reasons otherwise to use a Victron Multiplus inveter/charger:

1. Moochdocking often has limited shore power availability, often with a 15A breaker. The Multiplus provides a "assist" mode where you can program the inverter/charger to limit consumption to an arbitrary value, say 10A. Thus only 10Ax120V = 1200W will be provided via shore power to avoid tripping any breakers. If your total coach power needs exceed this value, say a 1500kW air conditioner plus 200W of other loads = 1,700W, then the 500W difference will be taken from your batteries via the Multiplus inverter section.
2. Automatic change-over - wire all AC loads to the Multiplus and change-over is automatically done whenever shore power is applied.
3. Customer support - assuming you purchase from a Victron dealer, their support has proven excellent. If a local supplier, even better.
4. Integration - you will need other components, 24-12V converter for DC loads, 12-24V chassis alternator charging, etc. All are available from Victron, and they plug and play well together. Most have BlueTooth i/f. I found the their integrated CCGX controller with WiFi support very useful. I can use Victron's Portal website portal to check on anything from anywhere.

I am using two SBMS0 to balance, control, and monitor my dual 24V Tesla S battery installation. Works great.

[Demosthien]

All good reasons to use a combiner option and I appreciate your feedback... However, aside from the fact we've already got our products, there are some reasons why your arguments don't really apply to our situation so keeping a seperate/inverter charger setup is a better option for us.

On Thursday, 1 October 2020 18:38:50 UTC+1, Rob Duncan wrote:

Demosthien - Since I have done this 24V conversion may I offer these reasons otherwise to use a Victron Multiplus inveter/charger:

1. Moochdocking often has limited shore power availability, often with a 15A breaker. The Multiplus provides a "assist" mode where you can program the inverter/charger to limit consumption to an arbitrary value, say 10A. Thus only 10Ax120V = 1200W will be provided via shore power to avoid tripping any breakers. If your total coach power needs exceed this value, say a 1500kW air conditioner plus 200W of other loads = 1,700W, then the 500W difference will be taken from your batteries via the Multiplus inverter section.

Our inverter usage will be very limited (there will definitely be no air conditioner!!) and not that it really makes a huge difference but as we're in the UK/EU will be at 230VAC not 120VAC. Powering a freezer/fridge conversion which surges at around 800W when activated and idles under 10W (IIRC), the oven light runs on 230VAC as does it's igniter, and then we might very rarely use any other mains powered devices. Over 90% of the loads on our vehicle use 12/24VDC or lower (like USB). Should we have a need to use shore power for anything more, likely limited to the occasional power tool usage, we have a generator which will be used rather than drawing from the batteries. The generator might not be as efficient as using the battery/inverter but it is more convenient and doesn't limit me to working right next to the truck.

If we ever encounter the unlikely situation where we are hitting the inverter's upper ceiling then we'll consider upgrading it to solve the issue.

1. Automatic change-over - wire all AC loads to the Multiplus and change-over is automatically done whenever shore power is applied.

Not really a major concern. Our system is not going to be have shore power connected directly to the sockets. All 230VAC sockets are only connected to the inverter, they will remain isolated from the shore power which makes automatic changeover redundant. There are good arguments in favour of not isolating the sockets this way but as we don't really need a lot of 230VAC none of those arguments are convincing. Also, we don't mind physically turning a switch to change power.

 

1. Customer support - assuming you purchase from a Victron dealer, their support has proven excellent. If a local supplier, even better.

Yes, our Victron gear is purchased from quality suppliers with good aftercare and Victron itself has the same... But that doesn't really count for much when we're in the backwoods of Romania/Poland/Finland/Russia or even Wales/Scotland with no communication coverage and a long drive to get anywhere we can get help. If our Inverter craps out, we lose 230VAC but can still charge our battery off the generator if we're in a tight spot. Alternatively, if our charger craps out we still have 230VAC. Either of those problems by themselves can be put to one side and dealt with at leisure. But if we have a combined unit we don't have a single problem, we now have two and that means the need to get it fixed is far more pressing.

 

1. Integration - you will need other components, 24-12V converter for DC loads, 12-24V chassis alternator charging, etc. All are available from Victron, and they plug and play well together. Most have BlueTooth i/f. I found the their integrated CCGX controller with WiFi support very useful. I can use Victron's Portal website portal to check on anything from anywhere.

We don't need as many extra components as you might think.

Most of our loads are selected because they can either run of 24VDC directly or they can themselves convert it down to their required voltage. We do still have to use some boost/buck devices, but where necessary we can easily wire them in and we can pick up reliable ones for pennies from the likes of AliExpress (I have boxes of them kicking around already from tinkering projects). I wouldn't pay Victron prices for such things as I don't see the benefit.

We don't need a 12-24V alternator charger as our truck operates a 24V system natively. When/If we eventually get around to setting up charging from the truck alternator/batteries it's not that complicated. But, we've got no firm plans to do so at this stage as we've planned for the vehicle to rely on solar as much as possible.

We looked at all the assorted Victron doohickeys and it is all super impressive and my GAS (Gear Acquisition Syndrome) was immediately triggered. We cannot justify the extra expense for things that have capabilities that, whilst certainly cool, we just don't actually need. The SBMS0 will tell me 90-100% of what we need to know about consumption and generation when we're near the truck. If we really want to know what is happening when we're away I'm sure there are multiple ways to grab the data from the SBMS0, dump it into a database from which infographics can be generated and then served to a webpage for upload to a host site somewhere. ¯\_(ツ)_/¯ 

[Demosthien]

It's been some time since I last posted any form of update on my build, and due to circumstances there wasn't a great deal to report anyway... But I thought I might go ahead and report what I've been doing, and if anyone has any advice or suggestions then I'm all ears.

I received 8x 3.2V 280Ah LiFePO4 cells from Shenzhen Xuba (via Alibaba) just before Xmas 2020 (and happily before Brexit). The service was great and the price was nothing to complain about so they get a "+++++ Double Plus Good +++++ Super A1 AliBaba-er +++++" rating from me. ;-) Prior to sending, Shenzhen Xuba sent photos of the cells being packaged and a video of the cells being voltage tested with all coming up ~3.29V. On arrival I unpacked them and tested them all and all of them were ~3.28V. I then had to pack them all away so they sat in their box for a while, at least until the beginning of 2021. I tested them again when I got them out of their short(ish) storage and they all again came back with ~3.8V.

I have since been back on the project and have actually been working on the main power distribution layout, or Node Zero as I call it.

Attached at the bottom of this post is a PDF schematic of my layout, it's pretty close to what I had previously posted in this thread but there have been some refinements made as I play around in the real world, rather than on e-paper. I have also added a photo of the cells during their second lot of voltage testing, after they were stored for a while.

Below is also a photo of the current state of Node Zero, I think most of it is pretty self explanatory (when viewed in conjunction with the schematic). I was in touch with my local scrap merchants and they had been keeping an eye out for good quality copper bars that I could use for busbars. They have come through for me as a large industrial unit was being upgraded and the electricians dropped all the old distribution boxes off for scrapping!! This meant I got my pick of a heap of lovely copper busbars, some of it was brand new offcuts from the upgrade and some was older stuff from the previous install. The two bars I have are 20mmx5mm (most of what you see) and 25mmx7mm (I only used this for the Load Busbar mainly for the extra surface area contact for the terminals). For comparison, I looked up 20mmx5mm copper busbar on a couple of local supplier websites and it ranged around £60/m... I got mine for the cost of the copper at market price, which meant at that time I got ~5m for ~£30. The bonus is that when I'm done I can take all my off-cuts back and they'll buy it back off me. Sweet!

I bent (sadly many of the items like the fuse holder and shunt etc have different heights) and drilled holes in the 20mmx5mm bars to suit the layout and this has meant I've avoided using cable on a lot of these main connections. I will be tinning all these bars using a method from another thread (I think described by Plamen?) and also covering them with heatshrink (gonna have to cut out holes so the bolts/terminals have good contact though) to avoid shorts. I'm a bit sad these bars are probably too thick to use as busbars on the cells as I'd go ahead and use them for that as well if I could (on a static build I'd do so, but I don't think it's a good idea on a motorhome). Anyway, aside from the negative busbar (which I'll probably use the 25mmx7mm for), all the rest of the connections will be cable.

Of course, there's currently a cable shortage around here due to Covid. It seems Covid caused the cost of copper and scrap in general to skyrocket and, according to one cable supplier and the scrap merchants, there has been a number of very large purchases of brand new cable for the explicit purpose of stripping the insulation in order to sell the copper for scrap! Apparently this is because the cable was all made before the copper price went so high so it is being sold at prices that match copper prices from over a year ago. Every day is a learning day! Happily I managed to get some 6mm2 cable before the market went crazy so It wont be long now and I'll be securing everything down to the backboard and I can start the larger cabling component. Once I've got this lot secured I can then get on with building the battery storage box (which will sit in that cross-hatched area at the bottom) and start testing the Electrodacus components.

[Dacian Todea]

This seems to look good tho you may need a fuse after the PV current shunt before that disconnect switch or at least you will need to protect that side of the circuit maybe cover with a plexiglas or something isolated.

I doubt new cables are less expensive than raw copper. Is almost like saying that since lumber prices here tripled it is worth demolishing a house just to recover the lumber :)

[Demosthien]

I have plans to make a perspex cover for the whole shunt/fuse assembly (the "T" fuse holder itself actually comes with a cover but it requires the connectors to enter/exit straight out rather than to the sides), but I can look at adding an additional fuse between shunt and switch (I had planned one there in an earlier version). Would the charge MCBs contribute toward the protection at that lower location on the circuit at all or are they too far away to matter? The charge MCBs in the image are going to be replaced with Langir which are non-polarised.

I thought the same about the cabling/copper thing but I've now had about three different businesses tell me that they've had people doing it. I still don't get it myself as I reckon you'd need to have a whole lot of cable to be able to make any profit and even then it'd be tiny.

[Dacian Todea]

The MCB's can protect the circuit but only if short happens after them that is why I mentioned that you will need to protect the charge bussbar and if you do so then you can get away with not needing a fuse there.

Seems price of copper was highest in around 2011 so now is not even the highest historical price and there is absolutely no way cables will cost less than raw materials. Usually cables will cost multiples of the raw materials not just a few % extra.

But maybe there were some highly discounted cables as the specific type of cable was not needed or had some manufacturing defect.