Silver Dream Machine - aka campervan mk2

[richbee]

I've also ordered renogy dc-dc / mppt combined charger
https://uk.renogy.com/dcc50s-12v-50a-dc ... w-version/

And a 2kw renogy inverter
https://uk.renogy.com/2000w-12v-pure-si ... -function/

The inverter & dc-dc charger have arrived today
The inverter comes with 2 sets (2 + and 2 - cables) of what I believe are 20mm2 cables to connect to the battery, with terminal crimps labelled as '100A'.
The paperwork is a bit vague, but for me, 1 set of 20mm2 cables is not enough for 2kW at 12V. At 12V it takes 166A (with no losses) - the battery should always be over 12V,so gives a little margin.
25mm2 cables are rated at 170A.

I wonder if it is intended to use both sets of cables in parallel, to reach a reasonable safety margin? Is that sensible?

I was originally planning for 35mm2 (240A) cables to be on the safe side - cables will be less than 1m long to avoid voltage drop issues.

What do you guys reckon?

[Stinsy]

I've also ordered renogy dc-dc / mppt combined charger
https://uk.renogy.com/dcc50s-12v-50a-dc ... w-version/

And a 2kw renogy inverter
https://uk.renogy.com/2000w-12v-pure-si ... -function/

The inverter & dc-dc charger have arrived today
The inverter comes with 2 sets (2 + and 2 - cables) of what I believe are 20mm2 cables to connect to the battery, with terminal crimps labelled as '100A'.
The paperwork is a bit vague, but for me, 1 set of 20mm2 cables is not enough for 2kW at 12V. At 12V it takes 166A (with no losses) - the battery should always be over 12V,so gives a little margin.
25mm2 cables are rated at 170A.

I wonder if it is intended to use both sets of cables in parallel, to reach a reasonable safety margin? Is that sensible?

I was originally planning for 35mm2 (240A) cables to be on the safe side - cables will be less than 1m long to avoid voltage drop issues.

What do you guys reckon?

Don’t focus on what the cables are “rated” at. This doesn’t take into account length, cable max current ratings are not usually “continuous”, and cable manufacturers are often happy with a 70-80℃ surface temp which will burn people and damage nearby materials.

Generally speaking you want a voltage drop of less than 1% on the DC side of a battery inverter. However you also need to consider how you’re using the batteries. Are you charging them from the mains at 2kW or 200W? Are you using a 1.8kW kettle for 5mins or are you drawing large amounts of power for long durations?

You should be aware that you’re operating at power levels for which 12V isn’t really appropriate. I get the reasoning, 2x Voltages (12VDC and 220VAC) is plenty, you get to have the starter and leisure sides connected and separated as appropriate/desirable. The point is that you need to understand the compromises in your system design and mitigate their consequences.

Long story short, 35mm²and <1m each way is borderline, 50mm² is more sensible.

Additionally, beware of cable fraud. It is unfortunately rampant. I pretty much guarantee that any cable you buy from eBay or Amazon will be one size smaller than advertised…

[richbee]

I've also ordered renogy dc-dc / mppt combined charger
https://uk.renogy.com/dcc50s-12v-50a-dc ... w-version/

And a 2kw renogy inverter
https://uk.renogy.com/2000w-12v-pure-si ... -function/

The inverter & dc-dc charger have arrived today
The inverter comes with 2 sets (2 + and 2 - cables) of what I believe are 20mm2 cables to connect to the battery, with terminal crimps labelled as '100A'.
The paperwork is a bit vague, but for me, 1 set of 20mm2 cables is not enough for 2kW at 12V. At 12V it takes 166A (with no losses) - the battery should always be over 12V,so gives a little margin.
25mm2 cables are rated at 170A.

I wonder if it is intended to use both sets of cables in parallel, to reach a reasonable safety margin? Is that sensible?

I was originally planning for 35mm2 (240A) cables to be on the safe side - cables will be less than 1m long to avoid voltage drop issues.

What do you guys reckon?

Don’t focus on what the cables are “rated” at. This doesn’t take into account length, cable max current ratings are not usually “continuous”, and cable manufacturers are often happy with a 70-80℃ surface temp which will burn people and damage nearby materials.

Generally speaking you want a voltage drop of less than 1% on the DC side of a battery inverter. However you also need to consider how you’re using the batteries. Are you charging them from the mains at 2kW or 200W? Are you using a 1.8kW kettle for 5mins or are you drawing large amounts of power for long durations?

You should be aware that you’re operating at power levels for which 12V isn’t really appropriate. I get the reasoning, 2x Voltages (12VDC and 220VAC) is plenty, you get to have the starter and leisure sides connected and separated as appropriate/desirable. The point is that you need to understand the compromises in your system design and mitigate their consequences.

Long story short, 35mm²and <1m each way is borderline, 50mm² is more sensible.

Additionally, beware of cable fraud. It is unfortunately rampant. I pretty much guarantee that any cable you buy from eBay or Amazon will be one size smaller than advertised…

Thanks Stinsy,
The planned usage is mostly short term like a 1500W kettle or a 1500w induction hob. With potentially an 800w water heater element, which would run for longer periods of time (with only 1 being used at a time).

The battery is being charged by a 50A dc-dc charger with built in mppt and ~400w of solar.

I have heard about cable size fraud, so was aiming to buy important cables from reputable sources & build in some slack at each stage.
Once I know the actual cable length, I'll work out the voltage drop

[Stinsy]

The inverter & dc-dc charger have arrived today
The inverter comes with 2 sets (2 + and 2 - cables) of what I believe are 20mm2 cables to connect to the battery, with terminal crimps labelled as '100A'.
The paperwork is a bit vague, but for me, 1 set of 20mm2 cables is not enough for 2kW at 12V. At 12V it takes 166A (with no losses) - the battery should always be over 12V,so gives a little margin.
25mm2 cables are rated at 170A.

I wonder if it is intended to use both sets of cables in parallel, to reach a reasonable safety margin? Is that sensible?

I was originally planning for 35mm2 (240A) cables to be on the safe side - cables will be less than 1m long to avoid voltage drop issues.

What do you guys reckon?

Don’t focus on what the cables are “rated” at. This doesn’t take into account length, cable max current ratings are not usually “continuous”, and cable manufacturers are often happy with a 70-80℃ surface temp which will burn people and damage nearby materials.

Generally speaking you want a voltage drop of less than 1% on the DC side of a battery inverter. However you also need to consider how you’re using the batteries. Are you charging them from the mains at 2kW or 200W? Are you using a 1.8kW kettle for 5mins or are you drawing large amounts of power for long durations?

You should be aware that you’re operating at power levels for which 12V isn’t really appropriate. I get the reasoning, 2x Voltages (12VDC and 220VAC) is plenty, you get to have the starter and leisure sides connected and separated as appropriate/desirable. The point is that you need to understand the compromises in your system design and mitigate their consequences.

Long story short, 35mm²and <1m each way is borderline, 50mm² is more sensible.

Additionally, beware of cable fraud. It is unfortunately rampant. I pretty much guarantee that any cable you buy from eBay or Amazon will be one size smaller than advertised…

Thanks Stinsy,
The planned usage is mostly short term like a 1500W kettle or a 1500w induction hob. With potentially an 800w water heater element, which would run for longer periods of time (with only 1 being used at a time).

The battery is being charged by a 50A dc-dc charger with built in mppt and ~400w of solar.

I have heard about cable size fraud, so was aiming to buy important cables from reputable sources & build in some slack at each stage.
Once I know the actual cable length, I'll work out the voltage drop

I’d be surprised if that 2kW inverter is rated for a 1500W induction hob. Usually you have to divide the big number by 4 to find the inductive load capacity of an inverter…

EDIT: I downloaded a PDF of the "Manual Book" for that inverter to see what size inductive loads it was rated for. Interestingly none is quoted. However it does say this:



Which isn't particularly helpful.

[Joeboy]

My wee travel kettle pulls 700W and makes two mugs. The induction hob only pulls a few hundred Watts.

So far the 1kW inverter has done it all. Just a thought for how much do you REALLY need?

Which is of course different from what we want.

It's not cheap to step from 1kW to 2kW in a van. Make sure you need it first. Personally I'd be running 35mm sq of a good quality and be happy that the 2kW inverter will likely push 1.2kW continuous.

[richbee]

Thanks guys - I love all the help & knowledge on this forum

I'm hoping the 1500W kettle (which I've just bought) should work OK, and it's only on for 5 minutes at a time.
For the induction hob, going to a smaller inverter wouldn't help in terms of running induction loads, but it would make appropriate wiring from the battery easier.
The 2kw inverter has already arrived, so I need to make it work somehow.

I think I will try the induction hob in the house and see if it modulates down, or if it pulses at full power to achieve the lower settings. If it pulses at full power I might have to try it on the inverter and monitor the current usage, with plan B to buy a lower power version to make sure it doesn't cause problems.

[richbee]

Not quite at the electrics fitting stage yet - still insulating the floor & planning where the bed, bathroom, bike storage drawer, electrics cabinet, water tanks etc etc are going

[Joeboy]

Not quite at the electrics fitting stage yet - still insulating the floor & planning where the bed, bathroom, bike storage drawer, electrics cabinet, water tanks etc etc are going

That looks like a great project, well played! What is the current tech at for foil insulation?

Not aerogel I assume?

[Joeboy]

I am cooking a gallon of pasta sauce in the van.



Classic FM is on and I've just run the fridge up too.



Weather is again hit&miss but when the sun breaks through the panels have topped the battery back up nicely. The extra panel power makes a huge difference to what we can do. I know it is obvious but having come from a 100W panel on the last van to nearly 400W of bifacial it really is an eye opener!



When it's dull we are still seeing 100W incoming. Heading to France in a few weeks so I'm getting into the wee bits that need done. Not much really, qualifies as pottering.

[richbee]

Not quite at the electrics fitting stage yet - still insulating the floor & planning where the bed, bathroom, bike storage drawer, electrics cabinet, water tanks etc etc are going

That looks like a great project, well played! What is the current tech at for foil insulation?

Not aerogel I assume?

I not going for anything very high tech, just the sticky backed 'rubber' with foil coating - 5mm or 10mm varieties depending where, and then the B&Q recycled plastic stuff in the door, wall & other cavities.
It's a mixture of budget constraints and height constraints - the van is 1.93m at the highest point, and I'm 1.89m - so trying to maintain being able to stand up, even if my hair brushes the carpet lining.

The biggest height issue seems to be having the bike garage under the bed - as I'm tall, my bikes are tall to the saddle, even with front wheel removed - then I also want to be able to just about sit up in bed - a couple of friends have suggested I should chop a few inches off my legs - would make life much easier