DC-DC Charger cable size (1 Viewer)

[kingoftheroad]

Hi
I'm finally at the point of getting around to purchasing, then fitting a Victron 50 DC/DC charger and have a question on the cable size please. The distance between starter batt and the charger will be about 5m, I was going to purchase 25mm and scale it down to 16mm at the fuse holder, for easier fitting into the victrons terminal, does this sound ok?

 

[oldiesontour]

25 mm is very excessive for 50amp over 2m would check an online cable size calculator my guess 10mm plenty

 

[kingoftheroad]

25 mm is very excessive for 50amp over 2m would check an online cable size calculator my guess 10mm plenty

Hi thanks for reply.
The guys on here a while back, recommend 16mm was about the right spec, but this changes, depending on the distance hence why I thought 25mm, with it being a 5m length

 

[oldiesontour]

Hi thanks for reply.
The guys on here a while back, recommend 16mm was about the right spec, but this changes, depending on the distance hence why I thought 25mm, with it being a 5m length

Sorry got it in my head as 2 m at 5m you will need 25 mm.Could you not move the controller nearer the starter battery ? How far is the lb from the controller?

 

[G7UXG]

12 Volt Planet’s voltage drop calculator suggests a voltage drop of about 0.4 volts for a 5 metre cable run of 25mm cable, and about 0.6 volts for 16mm cable.

Voltage Drop Calculator | 12 Volt Planet

Use our Voltage Drop Calculator to select the correct Cable for your campervan, motorhome or boat wiring application. Auto and Marine Electrical Components from 12 Volt Planet - Cable Size Calculator

www.12voltplanet.co.uk

I’d guess either would be OK because I think the B2B charger will deal with the voltage drop and still deliver the correct voltage to charge your batteries anyway (dependent upon battery type and B2B settings). That’s what they’re designed to do, even if the input voltage varies, as with a Smart alternator.

Personally, I’d stick to 25mm to future proof any future B2B upgrade. I used 25mm for an 8 metre run on a 45 amp B2B and it works fine.

^{_{Subscribers  do not see these advertisements}}

 

[rod_vw]

It's recommended that the B2B is located close to the leisure battery if that's any help to you.

 

[kingoftheroad]

12 Volt Planet’s voltage drop calculator suggests a voltage drop of about 0.4 volts for a 5 metre cable run of 25mm cable, and about 0.6 volts for 16mm cable.

Voltage Drop Calculator | 12 Volt Planet

Use our Voltage Drop Calculator to select the correct Cable for your campervan, motorhome or boat wiring application. Auto and Marine Electrical Components from 12 Volt Planet - Cable Size Calculator

www.12voltplanet.co.uk

I’d guess either would be OK because I think the B2B charger will deal with the voltage drop and still deliver the correct voltage to charge your batteries anyway (dependent upon battery type and B2B settings). That’s what they’re designed to do, even if the input voltage varies, as with a Smart alternator.

Personally, I’d stick to 25mm to future proof any future B2B upgrade. I used 25mm for an 8 metre run on a 45 amp B2B and it works fine.

Great, will go with the 25mm, thanks for the info.

 

[kingoftheroad]

It's recommended that the B2B is located close to the leisure battery if that's any help to you.

Hi
No didn't know, thought it could go anywhere. However, I was putting it the bedbox, which so happens to be above the battery, but thanks fo the heads up.

 

[G7UXG]

Perhaps stating the obvious, but make sure it’s appropriately fused very close to the vehicle battery. Mine is fused in the vehicle battery compartment I also added a fuse at the B2B end.

 

[Lenny HB]

I used 25mm² for a 7m run anything over 0a out 4m I would stick with 25m².

^{_{Subscribers  do not see these advertisements}}

 

[kingoftheroad]

Perhaps stating the obvious, but make sure it’s appropriately fused very close to the vehicle battery. Mine is fused in the vehicle battery compartment I also added a fuse at the B2B end.

Hi
Thanks, yes I had info on the fuse, from my postings in February, Lenny B gave me the info on this

 

[DBK]

It's recommended that the B2B is located close to the leisure battery if that's any help to you.

From a theoretical point of view that seems wrong. The highest current will be in the cables coming from the vehicle battery. The cables going from the B2B to the leisure batteries will be carrying a slightly lower current because the voltage will be higher.

I think the reason why B2Bs are usually closer to the leisure batteries is just because that's usually the easiest place to find the space to install the B2B.

But I think this is just a technical point. If the cables are properly sized for their length all will be fine. My B2B is at least 5m from the cab battery.

 

[kingoftheroad]

I used 25mm² for a 7m run anything over 0a out 4m I would stick with 25m².

Thanks Lenny, 25mm it is then.
I'd read somewhere that it was quite difficult getting 25mm cable into the terminal of new XS 50 Victron, hence, I intended to scale down to 16mm between the fuse holder and the leisure battery which will only be a distance of about 400mm, would you agree?

 

[G7UXG]

From a theoretical point of view that seems wrong. The highest current will be in the cables coming from the vehicle battery. The cables going from the B2B to the leisure batteries will be carrying a slightly lower current because the voltage will be higher.

I’d guess the reason it is recommended to be close to the leisure batteries is perhaps because if the B2B is putting out 14.2 volts (for example) and that’s what the batteries need to be properly charged, a short cable run between the B2B and the leisure batteries would result in minimal voltage drop at high current, so the batteries get the voltage they need. Voltage drop between the vehicle battery and the B2B is less important. My Votronic B2B will accept an input voltage in the range 10.5 - 16.5 volts (or so the spec sheet says) and put out the appropriate stabilised voltage to the leisure batteries.

 

[Lenny HB]

Thanks Lenny, 25mm it is then.
I'd read somewhere that it was quite difficult getting 25mm cable into the terminal of new XS 50 Victron, hence, I intended to scale down to 16mm between the fuse holder and the leisure battery which will only be a distance of about 400mm, would you agree?

That will be fine.
I used copper tube pins to connect 25mm² to the B2B, I had to file about a mm of each side of the pin to fit the B2B.

High Quality Non Insulated Copper Tube Cable Blade Pin Terminals - Heavy Duty | eBay

Heat Shrink Tubing. Cable Clip. High Quality Non Insulated Copper Tube Cable Blade. Heat Shrink. Manufactured from high quality tinned copper. Material: Copper. Cable Size mm². Cable Sizes.

www.ebay.co.uk

^{_{Subscribers  do not see these advertisements}}

 

[Lenny HB]

I’d guess the reason it is recommended to be close to the leisure batteries is perhaps because if the B2B is putting out 14.2 volts (for example) and that’s what the batteries need to be properly charged, a short cable run between the B2B and the leisure batteries would result in minimal voltage drop at high current, so the batteries get the voltage they need. Voltage drop between the vehicle battery and the B2B is less important. My Votronic B2B will accept an input voltage in the range 10.5 - 16.5 volts (or so the spec sheet says) and put out the appropriate stabilised voltage to the leisure batteries.

In practice it comes down to the layout of the van electrics
In my van the batteries are central but the distribution unit & charger is in the garage so the B2B conbects to my busbar in the garage via 7m of 25mn², then the bus bars connect the batteries via 4m of 70mm² cable. Only practical way to do it in my van.

 

[kingoftheroad]

That will be fine.
I used copper tube pins to connect 25mm² to the B2B, I had to file about a mm of each side of the pin to fit the B2B.

High Quality Non Insulated Copper Tube Cable Blade Pin Terminals - Heavy Duty | eBay

Heat Shrink Tubing. Cable Clip. High Quality Non Insulated Copper Tube Cable Blade. Heat Shrink. Manufactured from high quality tinned copper. Material: Copper. Cable Size mm². Cable Sizes.

www.ebay.co.uk

Spot on, I also made notes, of your advice/recommendations (my post in February), when you advised changing the 50amp maxi blade holder, etc, so thanks again

That will be fine.
I used copper tube pins to connect 25mm² to the B2B, I had to file about a mm of each side of the pin to fit the B2B.

High Quality Non Insulated Copper Tube Cable Blade Pin Terminals - Heavy Duty | eBay

Heat Shrink Tubing. Cable Clip. High Quality Non Insulated Copper Tube Cable Blade. Heat Shrink. Manufactured from high quality tinned copper. Material: Copper. Cable Size mm². Cable Sizes.

www.ebay.co.uk

 

[rod_vw]

From a theoretical point of view that seems wrong. The highest current will be in the cables coming from the vehicle battery. The cables going from the B2B to the leisure batteries will be carrying a slightly lower current because the voltage will be higher.

I think the reason why B2Bs are usually closer to the leisure batteries is just because that's usually the easiest place to find the space to install the B2B.

But I think this is just a technical point. If the cables are properly sized for their length all will be fine. My B2B is at least 5m from the cab battery.

Victron installation instructions for the Orion TR Smart state on page 7 that it should be located close to the battery.

My personal thought that the reason for this is so that the Orion can monitor the leisure battery voltage with a minimum of volt drop in the interconnecting cable thus being able to control the charge regime more accurately.

 

[G7UXG]

My personal thought that the reason for this is so that the Orion can monitor the leisure battery voltage with a minimum of volt drop in the interconnecting cable thus being able to control the charge regime more accurately.

I think with the Votronic units, if the cable run from B2B to leisure batteries is long, and so there’s a significant voltage drop, a monitoring wire can be separately connected from leisure battery +ve to a terminal on the B2B so that it monitors the voltage at the leisure battery and compensates accordingly to ensure the batteries receive the correct voltage.

 

[RogerIvy]

Victron recommend 16mm for cable runs less than 5m
And 25mm over 5m

I’d go for 25 and use pins.

Close to the leisure battery. If there is voltage drop over the cable from the starter battery the charger can compensate for it. If the run from the charger to the leisure battery is long the charger can’t compensate for loss.

^{_{Subscribers  do not see these advertisements}}

 

[royw]

16 works fine, installed a couple on 16mmat 5.1 and 5.3 meters worked perfectly well 25mm is overkill, quality cable and your fine.

 

[kingoftheroad]

Victron recommend 16mm for cable runs less than 5m
And 25mm over 5m

I’d go for 25 and use pins.

Close to the leisure battery. If there is voltage drop over the cable from the starter battery the charger can compensate for it. If the run from the charger to the leisure battery is long the charger can’t compensate for loss.

Hi RogerIvy:
The charger will be about 700mm from the battery, so should be ok then, I've just ordered some pins off Ebay, that Lenny HB recommended and just placed my order for the charger, from your website (thankyou for the funster discount)

 

[RogerIvy]

Hi RogerIvy:
The charger will be about 700mm from the battery, so should be ok then, I've just ordered some pins off Ebay, that Lenny HB recommended and just placed my order for the charger, from your website (thankyou for the funster discount)

Cool thanks, let me know if you need any help.

BTW while you re installing the DC-DC you might consider a Battery Master at the same time. Easy to insert the BM wires into the pin before you crimp.

 

[kingoftheroad]

Cool thanks, let me know if you need any help.

BTW while you re installing the DC-DC you might consider a Battery Master at the same time. Easy to insert the BM wires into the pin before you crimp.

Thanks, I appreciate the offer of help/advice, re Battery Master, got that fitted same time as battery, so ok there.