Could you check my B2B 12v setup diagram please (1 Viewer)

[caddy camper]

hello there
I'm just about to wire up my 12v set up in a micro build vw caddy (not smart alternator)
i have a renogy 20A B2B charger and renogy 100ah lithium smart battery
6 way fuse box running small 15l alpicool compressor fridge a 2kw diesel heater 4 led downlights a couple of usb sockets and a 600w inverter mainly for laptop and charging cordless drill.
would someone be good enough to run over my diagram please as a little knowledge can be a dangerous thing specially with electrics lol
just a couple of questions please
i feel like the 600w inverter should have a fuse but all the tutorials show the inverter connoted directly to the battery with no fuse is this correct ?
is the 50A circuit breaker for the fuse box of appropriate size?
I'm not sure if i need a battery isolator switch? i've put one in the diagram just before the positive input of the B2B.
Could i use the 30A circuit breaker next to the starter battery as the battery isolator switch as well as a fuse?
if so could i then move the 30A breaker to the B2B input? (it's currently going 8" from starter battery) the length of cable from the starter battery to the B2B charger is around 2.5m (under passenger seat)
i know or think that isn't ideal if the fuse did break there would be 2m of live cable going to the starter battery although it is routed under trim notsure.com haha
many thanks james

 

[monzer]

I've found autorouter a great help when it comes to things like this.

 

[Lenny HB]

Basicly OK.
You need to take the negative connection on the input of the B2B direct to the starter batter not via the chassis.
A lot of the DC circuit breakers have a rep for not being that reliable I would use midi fuses.
You need to fuse the output of the leisure battery and a fuse at the battery for the inverter.

More efficient to use a 12v charger for the laptop or if using a inverter make sure you get a good quality pure sine wave one.

 

[Itsmcb]

I used one of these for fusing the feeds from my battery recently.

MEGA - MIDI fuse distribution box (CLOSED BACK) ALT/FH260158 -1-54

function passpara(){return '&id 771203&itembgcolor 0xFFFFFF&bordercolor 0x000000&storewindowbgcolor 0xb8d6b6&toptextcolor

www.altecautomotive.co.uk

 

[Itsmcb]

PS it does come with a cover which i have put in (after the photo)

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[two]

"Fuse ?" between the batteries is unnecessary, unless they are far apart, when that should be "fuses" (one at each end).

 

[Lenny HB]

"Fuse ?" between the batteries is unnecessary, unless they are far apart, when that should be "fuses" (one at each end).

He has only got one leisure battery, there should always be one fitted in the starter battery feed to the leisure circuit.

 

[autorouter]

The B2B wiring diagram looks OK, the circuit breakers should go very near the battery that the wire is connected to, not near the B2B. The B2B can be connected permanently to the starter and leisure batteries, the battery isolator is not necessary. The two circuit breakers will isolate the B2B if that is required. The D+ wire ensures that the B2B is only charging when the engine is running and the alternator is producing power.

You are right about the fuse for the inverter. All wires from a power source like a battery need a fuse or circuit breaker near the battery - this includes the inverter positive. 600W/12V = 50A, so a fuse of about 70A would be about right.

50A is fine for the breaker to the fusebox. Commonly they are 30 to 50A.

Wire thickness is usually specified by the cross-sectional area (CSA) in millimetres squared (mm2). Normally it should be thick enough that the voltage drop is 3% or less. There are voltage drop calculators online, such as this one. If the voltage drop is 3% or less, it will be easily able to handle the amps in terms of safety and heating effect.

Cable Size Calculator - Cable sizing and selection | 12 Volt Planet

Cable Size Calculator - Read our guide to selecting cable of the correct type and size for your automotive, marine or leisure wiring application. Auto and Marine Electrical Components from 12 Volt Planet

www.12voltplanet.co.uk

For example, for a 600W inverter (ie 50A) with 1 metre wires, 10mm2 has a 1.5% voltage drop. For 2 metres it would be 3% which is just OK.

 

[two]

He has only got one leisure battery, there should always be one fitted in the starter battery feed to the leisure circuit.

Didn't read the diagram correctly. Assumed the inverter to be a second battery. So just one fuse.

 

[caddy camper]

Basicly OK.
You need to take the negative connection on the input of the B2B direct to the starter batter not via the chassis.
A lot of the DC circuit breakers have a rep for not being that reliable I would use midi fuses.
You need to fuse the output of the leisure battery and a fuse at the battery for the inverter.

More efficient to use a 12v charger for the laptop or if using a inverter make sure you get a good quality pure sine wave one.

thanks Lenny is it essential for the negative input of the B2B to connect to the - starter battery? i did phone 2 split charge companies' to confirm i could take that connection to the chassis when i ordered the cable, the B2B wiring kits they supply only has 1m earth cable but i can order some more cable if essential.

i've bought circuit breakers now lol but i will definitely pick up a couple of midi fuses as spares/back up

ah brilliant thanks i've just googled them i didnt even know they existed yeah i was given a TBS electronics pure sine wave inverter its looks like it built like a tank haha

The B2B wiring diagram looks OK, the circuit breakers should go very near the battery that the wire is connected to, not near the B2B. The B2B can be connected permanently to the starter and leisure batteries, the battery isolator is not necessary. The two circuit breakers will isolate the B2B if that is required. The D+ wire ensures that the B2B is only charging when the engine is running and the alternator is producing power.

You are right about the fuse for the inverter. All wires from a power source like a battery need a fuse or circuit breaker near the battery - this includes the inverter positive. 600W/12V = 50A, so a fuse of about 70A would be about right.

50A is fine for the breaker to the fusebox. Commonly they are 30 to 50A.

Wire thickness is usually specified by the cross-sectional area (CSA) in millimetres squared (mm2). Normally it should be thick enough that the voltage drop is 3% or less. There are voltage drop calculators online, such as this one. If the voltage drop is 3% or less, it will be easily able to handle the amps in terms of safety and heating effect.

Cable Size Calculator - Cable sizing and selection | 12 Volt Planet

Cable Size Calculator - Read our guide to selecting cable of the correct type and size for your automotive, marine or leisure wiring application. Auto and Marine Electrical Components from 12 Volt Planet

www.12voltplanet.co.uk

For example, for a 600W inverter (ie 50A) with 1 metre wires, 10mm2 has a 1.5% voltage drop. For 2 metres it would be 3% which is just OK.

thanks Autorouter
i will keep the circuit breaker 8" from the starter battery and not bother with the battery isolator
great stuff i'll grab a 70A fuse for the inverter
i've gone with 10mm2 70A (8 AWG) highflex cable which is in line with renogys specifications i think lol length of cable from starter battery to B2B 2.5m

the inverter comes pre wired with pos and neg cable looks to be 10mm2 its a TBS 600w pure sine wave
many thanks james

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[Lenny HB]

thanks Lenny is it essential for the negative input of the B2B to connect to the - starter battery?

All the B2B's I've come across always recommend a direct connection, that's the reason I suggested it.

 

[caddy camper]

thanks Lenny appreciate your input i thought the chassis was a common ground so it would be the same as connecting the B2B negative input to the starter battery no difference either way round.but im not 100% sure now
i may order some more cable with the fuses

 

[gerry mcg]

i feel like the 600w inverter should have a fuse but all the tutorials show the inverter connoted directly to the battery with no fuse is this correct ?

im not going to argue fitting a fuse is not a good idea, however Victron themselves suggest a fuse is not an absolute necessity for their lower powered inverters (12/250W - 48/1200W) with short (<1.5m cable runs). (i have the 500W inverter)

The purpose of the fuse is to protect the cable from overheating, not the inverter from blowing
their Phoenix Inverter 250VA - 1200VA manual https://www.victronenergy.com/inverters/phoenix-inverter-vedirect-250va-800va#manual says

 

[68c]

I've found autorouter a great help when it comes to things like this.

Clicked on 'Autorouter', expecting to find an online aid to drawing circuits....

 

[caddy camper]

thanks for that greery mcg
it made me check the data sheet for my inverter i found this diagram showing a fuse fitted but no mention of what size but think i will stick with a 70a fuse to be on the safe side

I'm still unsure about the input of the negative to the B2B charger .
i was planning as per diagram grounding the negative input from the B2B to the chassis with the fuse box and leisure battery negative looking at the renogy manual it does show the negative coming from the battery direct to the B2B.

the chassis is a common ground so anything connected to the chassis would be like connecting to the starter battery.
is that correct?
it would save me buying more cable and i could fit it this weeked
many thanks james

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[gerry mcg]

Votronic don’t require a ground cable between the -ive terminal of the Leisure battery and the -ive terminal of the starter , but it is advises where there is a well insulated chassis.
It worked without, but for safety, following various recommendations from Lenny HB and others, ive run a 16mm2 cable between the -ive terminal of the Leisure battery and the -ive terminal of the starter as per diagram, and with table clarification

 

[caddy camper]

thanks gerry much appreciated
there is a factory earth point where im fitting the charger and battery behind the passenger seat i was going to use.
so it would only be needed to run a negative cable from the starter battery if i had a insulated chassis?
i'm not sure what a insulated chassis is lol
i've emailed renogy for clarification too
cheers james

 

[Johnen]

I thought that the negative going back to the starter battery was because a lot of B2B use was on boats which don’t have a common chassis earth.
if you connect the negative back to the starter battery that doubles the distance to be used in voltage drop calculations. I have just connected my negative to the body of the van, keeping the cable length as short as possible.
all fuses should be fitted as close the the battery as possible.
just a thought why is there an earth on the fuse box?

 

[Wagoneer]

The weakest link in the EARTH system is usually between the alternator/engine block to chassis. This link is normally made using a flexible braided earth connection between engine and chassis (within the engine bay). This braided cable can sometime corrode from the inside and cause starting problems and reduced alternator output. I've replaced this with a short battery cable from Halfords.

Suggest, at this stage, you assume the earthing points to the common chassis are ok.

You can test the earthing system once you've done the final install by temporarily connecting between earthing points with a starter battery jumpstart lead (with crocodile clips either end). Any variation in amps/volts between starter negative and hab negative OR starter negative and Engine block, with engine running, would indicate a probable earthing problem.

 

[caddy camper]

just a thought why is there an earth on the fuse box?

thanks for the input John
i thought it would need to be earthed as all the appliances earths go there

The weakest link in the EARTH system is usually between the alternator/engine block to chassis. This link is normally made using a flexible braided earth connection between engine and chassis (within the engine bay). This braided cable can sometime corrode from the inside and cause starting problems and reduced alternator output. I've replaced this with a short battery cable from Halfords.

Suggest, at this stage, you assume the earthing points to the common chassis are ok.

You can test the earthing system once you've done the final install by temporarily connecting between earthing points with a starter battery jumpstart lead (with crocodile clips either end). Any variation in amps/volts between starter negative and hab negative OR starter negative and Engine block, with engine running, would indicate a probable earthing problem.

thanks wagoneer that makes sense i will do these checks
cheers james

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[autorouter]

it would only be needed to run a negative cable from the starter battery if i had a insulated chassis?
i'm not sure what a insulated chassis is

Vehicles generally do not have insulated chassis. It's standard in a vehicle for the alternator negative to be the alternator body, which is connected to the engine by a solid bolt or two. There is a thick electrical connection from engine to chassis. The battery negative is connected to the chassis. To save on wiring, negatives are connected to the chassis, and the currents return to the battery through the chassis.

The chassis is quite a low resistance return path, but it has its limits. If you had a large inverter pulling say 200A, it would be wired with a thick dedicated negative wire all the way back to the battery, because that high current might be large enough to cause a voltage drop along the chassis.

Devices that pull 50A or more could perhaps benefit from a separate negative wire back to the battery, or it might be OK to run it via the chassis, it's debatable. In a motorhome, the bodywork is made of thin aluminium, fibreglass, foam etc and it's not so easy to find a convenient chassis connection. That's often why separate negative wires are used in motorhomes.

 

[caddy camper]

thanks for taking the time to explain that Autorouter its much appreciated and for everyone's input sorry if im like a dog with a bone but really helps to fully understand it .

i managed to get started today got the positive cable run and fused at the battery made a board for everything to sit on behind the passenger seat and made some nifty brackets to bolt it down from the seat base

i'm still waiting for my renogy battery to be shipped its due next week but i have built a DIY lifepo4 battery that i was going to use so i can test everything it was supposed to be 105ah but the Chinese seller had been eating Lie Pie's as they only tested 76ah 1 cell drops voltage while the other 3 have 20% left i will make a portable power station out of it.

its now in a battery box
cheap and fun to build if you can find a trusted seller for the cells
thanks again its really appreciated for all your help
cheers james

 

[caddy camper]

hello again
i'm just wiring up my board the 50A circuit breaker (black & yellow) the terminals are marked battery side and load side.
The 30A circuit breaker i have (black and red) has no indications of battery and load side is there a correct way to wire the 30A breaker or does it not matter which what round it is?
many thanks james

 

[caddy camper]

Thanks for all your help
Just finished the install and it's working perfectly a constant 19.9A going in to the battery.

I have a android head unit that reads the starter battery voltage its usually 14.50V when engine running with the B2B on its dropping to 14.15V.
I'm not sure if that's working the alternator to hard but I would say it's not to bad lol.
Not the final position of everything as the renogy battery is smaller but wanted to test it working with my DIY battery

Is there a terminal cover for a mate bolt type connector?
Many thanks James