[Guide] DC-DC Charger (for leisure battery) -- How I Done It --

[Grim Reaper]

Shunt? What is the rating of the shunt? 300A?
Again, what is the maximum theoretical drain you could take out of the batteries with everything turned on? Likely to be influenced most by the inverter as these start to take HUGE current draw when you get over say 700 watts, The cable size needed for a 3000W inverter was so big I couldn't fit it in the gap I had available, even just going from passenger to driver seat base, so I opted for a smaller inverter and resigned myself to be only able to run the microwave when on hook up.

 

[Epic-Rob]

It's all a question of sizing appropriate to the expected current drain/feed over the cable.
What size is your DC-DC charger? 40A? Then a cable rated for 50A (over whatever length you need to feed it) and a fuse rated 50A to protect the cable from ever getting that much current fed down it would be acceptable.
What rating is your inverter? what is the maximum expected drain from your leisure batteries required to run the inverter at its maximum load? It should be in the specs somewhere. 100A? then you'd need to rate the cables from your leisure batteries to the inverter at say 120A and fuse it accordingly, not forgetting that the negative cable needs to be the same rating or actually higher because you may have the inverter running flat out and all the lights/chargers/water pumps/televisions etc etc on at the same time.
Always fuse nearest the source of the current feed, and rate the fuse to protect the cable not the item that is draining through it (eg if you installed a 50A cable for a 50A drain and fused it at 50A, the chances are you would keep blowing the fuse every time you pulled max current), so rate the cable above the drain, and fuse the cable accordingly.
Nothing wrong with installing 100A cable, and fusing it at 60 or 80A for a 50A device.

I am not very power hungry. i am probly well over what i actually need but i went this way with 2 batteries as on my last van the one 100Ah AGM and 120w solar couldnt keep up with the small 12v compressor fridge (and this is in NZ where we actualy get to see the sun ;-) ) so i put a 25amp DCDC on that setup

This time i just thought i would start with more storage capacity (2x 100Ah Lithium) my DCDC is 25amp along with 160W solar, the inverter is only 350w as i will only use it to charge an Ebike battery.

i wont be running TV, coffee makers etc

so really we will have fridge on (Dometic CRX50) led lights, water pump, and usb chargers for phones etc that will pretty much be it. oh i do have a diesel heater fitted under van as well

 

[Grim Reaper]

Yeah, I've been looking through the specs for the NDS 25A charger, would you say you have 16mm2 cable (the NDS manual says the terminals are for up to 16mm2 conductors.) for the Starter to charger link? That should be fine for the expected current draw, fuse at 50A or lower if you can get something around 35-40A fuse.
Use the 16mm2 for the charger to battery cables as well, and I'd say it would be fine for the battery to inverter cables if the distance isn't too far, negative cables as well in this size. In fact, so long as you're not running them more than 2 or 3 metres, 16mm2 cable will do for everything you have there.
I'd recommend the midi fuse holders over those blade type ones with covers on them, seen a few of them melt because of poor connections inside the plastic where you can't see them.

All Trade Direct 1 X Strip Link & Midi Fuse Holder For Striplink & Midi Fuses Fuseholder Fits All : Amazon.co.uk: Automotive

Buy All Trade Direct 1 X Strip Link & Midi Fuse Holder For Striplink & Midi Fuses Fuseholder Fits All at Amazon UK. Free delivery on eligible orders.

www.amazon.co.uk

And I'd change to some decent crimp fittings rather than the yellow terminals you are currently using.
Like these https://www.amazon.co.uk/ELECTRAPIC...minal+Crimp+Connectors&qid=1640805501&sr=8-36
with heat shrink over them as insulation.

 

[Epic-Rob]

Ok so this would be my proposal of layout
DCDC charger and shunt cant move from under drivers seat without pulling half van apart to lengthen some wires.

Thinking that its best to run power through the battery bank i would take the Dcdc feed into LB2 under passenger seat.
would take the shunt off NEG term on LB1 and earth to a seat base bolt in the floor, also take DCDC neg to same point.
Leisure fuses and inverter to be taken off LB1 pos

but that just gets me thinking is LB2 sat on its own at the end? because the neg and pos terminals are connected and the feed out is from LB1 will even power be put into both batteries?

How i had it before with the earth coming off LB2, whilst it defeated the shunt it gave a power flow through of both batteries.
How To: Connect two batteries in parallel – Part 2 2nd to last diagram

 

[Dellmassive]

@Epic-Rob - I've created a new Thread for your build. - Epic-Robs - Lithium Leisure Build -

please move over to this thread for your build as its very specific to you and starting to swamp this thread.

this thread is for Generic DC-DC builds.


+++

so can we all jump over the there for furure replies.


Epic-Robs - Lithium Leisure Build -

@Epic-Rob

@Grim Reaper

@Dellmassive

 

[Soundz]

Dell ..................@Dellmassive.....................are you yet aware of the new Dc to Dc chargers from sterling power :

Battery to Battery Chargers

Market leaders in power distribution for off-grid purposes. Providing class leading AC/DC and DC/DC chargers, highly customisable charge options and high performance lithium batteries. Sterling aims to be an accessible performance brand.

sterling-power.com

The sheer amps I find staggering.

Dell as an aside I don't have a shiny new T6 just an old T5 built in 2006.....so kinda feel awkward posting here. I'm slowly plodding through a conversion which will be based around a Li Fe PO4 battery and a load of victron gear. Probably roamers new 230 AH seatbase I've me 'eart set on 200AH that's for sure

I just wanted to say thank you for all the threads and effort and nouce you have shared,i've learnt so damn much reading your threads and taken so much inspiration from the builds

cheers matey

Have a wonderful; new year

stu

 

[Grim Reaper]

While LiFePo batteries will take huge amounts of charging current, the only problem I can see is that you'd have to rate all the cables from starter through to leisure battery to take the amount of current that the DC/DC charger could take, so 120A over the, say 3 metres between engine bay and under seat area (or further if the charger is located under kitchen units in a camper) would need 35 to 50mm2 conductors, the cost and ability to terminate that size cable onto the respective parts of the system would be the limiting factor, you'd have to size any connectors and cut off switches accordingly.

 

[Sim60]

While LiFePo batteries will take huge amounts of charging current, the only problem I can see is that you'd have to rate all the cables from starter through to leisure battery to take the amount of current that the DC/DC charger could take, so 120A over the, say 3 metres between engine bay and under seat area (or further if the charger is located under kitchen units in a camper) would need 35 to 50mm2 conductors, the cost and ability to terminate that size cable onto the respective parts of the system would be the limiting factor, you'd have to size any connectors and cut off switches accordingly.

You'd also need the uprated Alternator as well wouldn't you - I thought the standard T6 alternator was 140A max - I wouldn't want to take 120A from that for any period. Even the 70A sterling DC-DC sounds challenging

Simon

 

[Dellmassive]

Dell ..................@Dellmassive.....................are you yet aware of the new Dc to Dc chargers from sterling power :

Battery to Battery Chargers

Market leaders in power distribution for off-grid purposes. Providing class leading AC/DC and DC/DC chargers, highly customisable charge options and high performance lithium batteries. Sterling aims to be an accessible performance brand.

sterling-power.com

The sheer amps I find staggering.

Dell as an aside I don't have a shiny new T6 just an old T5 built in 2006.....so kinda feel awkward posting here. I'm slowly plodding through a conversion which will be based around a Li Fe PO4 battery and a load of victron gear. Probably roamers new 230 AH seatbase I've me 'eart set on 200AH that's for sure

I just wanted to say thank you for all the threads and effort and nouce you have shared,i've learnt so damn much reading your threads and taken so much inspiration from the builds

cheers matey

Have a wonderful; new year

stu

Thank you Stu @Soundz - that means a lot and makes all the effort worth while.

Dell ..................@Dellmassive.....................are you yet aware of the new Dc to Dc chargers from sterling power :

Battery to Battery Chargers

Market leaders in power distribution for off-grid purposes. Providing class leading AC/DC and DC/DC chargers, highly customisable charge options and high performance lithium batteries. Sterling aims to be an accessible performance brand.

sterling-power.com

The sheer amps I find staggering.

Dell as an aside I don't have a shiny new T6 just an old T5 built in 2006.....so kinda feel awkward posting here. I'm slowly plodding through a conversion which will be based around a Li Fe PO4 battery and a load of victron gear. Probably roamers new 230 AH seatbase I've me 'eart set on 200AH that's for sure

I just wanted to say thank you for all the threads and effort and nouce you have shared,i've learnt so damn much reading your threads and taken so much inspiration from the builds

cheers matey

Have a wonderful; new year

stu

Thanks for the kind words and link Stu, @Soundz

gotta say 70A and 120A is a big jump from the current 50A offerings. ( like Redarc bcdc1250d 50A )

120A will defiantly be a Alternator killer for most. ( i have the uprated T6 alternator, its supposed to be 180A but its listed as 2000W in VCDS?)

and as @Grim Reaper points out you need some beefy gauge cable all the way through.

....

it reminds me of my old BMW 520D, the AGM battery was in the boot tucked away . . . the car had a massive Bus-Bar type cable running up to the engine bay (was run under the car along with brake lines) via a jumper starter point, down to the starter with a second fat cable from the starter to the alternator. - it needed to be that thick to stop the huge volt drop when pulling 200+ Amps

+++

edit:

just seen in the Sterling docs that its advised to get a DC-DC charger rated to 70% max of the Alternator output.

.



.





.

 

[Dellmassive]

thanks to @Soundz for the heads up . . .

Sterling power release 70A & 120A DC-DC chargers . . .

Battery to Battery Chargers

Market leaders in power distribution for off-grid purposes. Providing class leading AC/DC and DC/DC chargers, highly customisable charge options and high performance lithium batteries. Sterling aims to be an accessible performance brand.

sterling-power.com

this is the BB1270 70A unit. - £450 - - https://cdn.shopify.com/s/files/1/0658/7343/files/BB1270_manual.pdf?v=1635868907







BB1270
Input voltage range 9V-16V
Rated output power 60A at 13.8V
Rated input current 70A
Quiescent current 10mA
Efficiency rating 92%-94%

Self recovering protections: under voltage protection
input over voltage protection
output over voltage protection
over current protection
charge over temperature

Operational Temperature -20 Deg C -> 60 DegC

Approval CE | UKCA
E-Marking
Cooling method Thermostatically Controlled
Variable low speed fan

Dimensions 200mm x 130mm x 56mm
Weight 1.0Kg



+++++++++++++++++++



and the BB12120. 120A - £600 - https://cdn.shopify.com/s/files/1/0658/7343/files/BB12120_manual.pdf?v=1635345051






BB12120
Input voltage range 9V-16V
Rated output power 110A at 13.8V
Rated input current 120A
Quiescent current 10mA
Efficiency rating 92%-94%

Self recovering protections: under voltage protection
input over voltage protection
output over voltage protection
over current protection
charge over temperature

Operational Temperature -20 Deg C -> 60 DegC

Approval CE | UKCA
E-Marking
Cooling method Thermostatically Controlled
Variable low speed fan

Dimensions 270mm x 130mm x 73mm
Weight 1.8Kg


++++++++++++++++


....

https://cdn.shopify.com/s/files/1/0658/7343/files/Battery_AMPS.pdf?v=1631881108

.

 

[Dellmassive]

additional info . .

VCDS screenshot from the other day looking at Battery Regulation monitor and power.

061 - Battery Reg / measure block group - 026

shows Alternator outputting 75.6A with a reserve of 100.0A - so adds up to 180A (ish)


it also states 2000w which is around 167A at 12v . . . . ( w=v*a )





..

a short while later . . . starter battery accepting charge and SOC increasing cuasing a drop in demand from the ALT`.

at this point 60.4A from ALT` leaving 108.0A in reserve. . . . . .




.

 

[Dellmassive]

NEW Product.

NDS Tripple charger . . .

NDS Power Service Gold 30-M Triple Charger 30A DC-DC, 20A Mains, 250W Solar

The NDS PowerService Gold 30-M is a complete 12V charging system for campervans & motorhomes, with a 30A DC-DC charger, 20A mains charger & 250W solar controller.

www.12voltplanet.co.uk

looks interesting for a Tripple - maybe a cheap option?

though its PWM solar - not MPPT (250w / 28voc max)
its 30A DC-DC charger
its 20A EHU charger
it says 90Ah or larger AGM
it says smaller for Lithium ( so ok for a 100Ah+ lifepo4)



The NDS Power Service Gold 30-M is an all-in-one triple charger for your leisure battery. This compact unit can manage multiple charging sources thanks to its combination of a 30A battery-to-battery (DC-DC) charger, a 20A mains-powered charger and a 250W PWM solar controller, enabling you to charge from your vehicle's alternator whilst on the move, from an AC mains hook-up whilst on site, or from solar panels whilst off-grid. This saves space, cabling and installation time when compared with fitting three separate pieces of equipment.

The Power Service Gold-30M optimises the charging of your 12 volt battery from multiple sources and can be fitted to vehicles with either standard or Euro 6 'smart' alternators. It can be used with all lead-acid batteries and lithium batteries and has dedicated, selectable charging profiles for each type.

Important - only to be used with solar panels that have an Open-Circuit Voltage (VOC) of 28V or less. Greater voltages may damage the unit and will void the warranty.

Suitable for 12V nominal voltage systems.

Features

• 30A DC-DC charger compatible with all alternator types (standard, Euro 5, Euro 6 +)
• 20A wide input voltage range (90-264V AC) mains charger
• PWM solar controller with 250W max. panel capacity
• 5-stage charging
• Fast and deep charging of leisure batteries
• Can be used with all lead-acid (flooded, sealed, AGM, gel etc.) and lithium batteries
• Selectable (via jumper) multi-stage charging profiles
• Auxiliary connection for existing systems (CBE, Sargent, Schaudt, Nordelettronica etc.)
• Engine and leisure batteries are kept separated to prevent accidental discharge
• Protection against over-temp, short circuit, reverse polarity, over-current, over-voltage, low-temp (lithium only)
• LED status indicators and audible warning
• User-replaceable fuses
• Supplied with 2-pin Euro to IEC power lead

Further info

Recommended minimum lead-acid battery capacity is 90Ah (smaller capacity lithium batteries may be used).

 

[Soundz]

As above lads not really researched the sterllngs, but the thoughts raised were mine also.....ha ha Del I've really read far far too many of your threads, i'm ponderously slow,jeez over a year making some units for the bus and still clocking the hours. so I've been trying to bang the leccy stuff in for more than a while now. Not there yet but trying to really get my head around it all

My first thought with the sterling was what kinda of alternator would be needed ( obviously with an old bus is that even possible ? ) ha and yeah like the reeper states cables are next.... then connections........mind my slow approach kinda do it once do it right work hard then go play hard : all the Massive threads alot of Will Prowse leans me towards maxing cable sizes. Me I'd rather just spend a bit extra and over spec if poss

I've a victron orion 12 12 30 which will be plumbed with 16mm2 which victron say is the max it can take............... hence not really studying the new sterlings

I'm a simple lad I think of leccy like water flowing through pipes.......if ya have too much pressure and too small a pipe things burst it's a simple laymens way of visualizing the flow of electrons. once ya can see it in your head it sort of makes skimping of cable sizes somewhere one doesn't want to go

Again thanks for the help Del, your posts have been enabling mate simple as!!


Forgive my first post an all wanted to say Ta but not ask for anymore than has already been given........... as I say t6 land is really out of reach and although i've lurked for eons it feels awkward posting........................... but a camper that'll work for our largely humble needs and give us a few of the comforts of home leccy wise seems ever more doable

Ta

stu

 

[bytejunkie]

another awesome thread from Dell, thanks.

am i right in thinking that this device in the picture linked below is not a DC-DC charger as my early T6 180bhp TDI should have?

Vehicle was bought as the converters old demo vehicle and electric have never been fully trustworthy for me. worked out recently that it didnt have a Stop/Start rated battery, so replaced that, but have suspected that this charging relay device isnt right since i started reading this thread.

New item by Matt Short

 

[Grim Reaper]

Further info

Recommended minimum lead-acid battery capacity is 90Ah (smaller capacity lithium batteries may be used).

Recommended MINIMUM is 90Ah, so larger would be OK.

 

[Grim Reaper]

another awesome thread from Dell, thanks.

am i right in thinking that this device in the picture linked below is not a DC-DC charger as my early T6 180bhp TDI should have?

Vehicle was bought as the converters old demo vehicle and electric have never been fully trustworthy for me. worked out recently that it didnt have a Stop/Start rated battery, so replaced that, but have suspected that this charging relay device isnt right since i started reading this thread.

New item by Matt Short

No, that looks like a split charge relay, meant for simple, normal alternator vehicles, it’s not a DC/DC charger.

Mega Van Mats

www.megavanmats.com

 

[bytejunkie]

Recommended MINIMUM is 90Ah, so larger would be OK.

thanks. the auto factor told me it needed to be over 770 cca (cold cranking amps), it was 440. so off came the 60 quid from euro car parts lion battery, on went the 180 yuasa replacement. will go source a DC-DC charger now. thnaks for replies.

 

[Dellmassive]

Recommended MINIMUM is 90Ah, so larger would be OK.

Thanks @Grim Reaper for the correction....

I've adjusted above post accordingly.

 

[Dellmassive]

another awesome thread from Dell, thanks.

am i right in thinking that this device in the picture linked below is not a DC-DC charger as my early T6 180bhp TDI should have?

Vehicle was bought as the converters old demo vehicle and electric have never been fully trustworthy for me. worked out recently that it didnt have a Stop/Start rated battery, so replaced that, but have suspected that this charging relay device isnt right since i started reading this thread.

New item by Matt Short

That's a VSR... It's ok for traditional Alternator setups.

But no good for stop start vans with the smart alternator.

As @Grim Reaper pointed out, you should look into replacing that with a DC-DC charger.

And good news that you have swapped out your starter battery.... Start stop vans should be using AGM style SLA battery.... Or the cheaper EFB+.

 

[Grim Reaper]

thanks. the auto factor told me it needed to be over 770 cca (cold cranking amps), it was 440. so off came the 60 quid from euro car parts lion battery, on went the 180 yuasa replacement. will go source a DC-DC charger now. thnaks for replies.

I'm Confused? Auto Factor said Starter battery needed to be over 770A or leisure battery? Both wrong by the way.
Starter battery on a Stop/Start van needs to be EFB or AGM, no specifics on the Cold Cranking Amps (though more is generally better)
Leisure battery would never be used in this way (usual drain on a leisure battery is small current drain over long period rather than short burst of high current drain like a starter requires) so CCA is irrelevent, Ah is the indicator on leisure batteries (higher figure = longer drain time), as is the chemistry, fatter lead plates are desired, AGM leisure or LiFePo4 even more so.
The 90Ah quoted above is a suggestion for the Leisure battery, I reckon because of the output current of the DC/DC charger and anything smaller than 90Ah would risk killing it with charge current.
If you have a Stop/Start van then you need an EFB or AGM as these are the ones that will accept the dump of current that the smart alternator pushes into the battery on occasion, if they've sold you a regular lead acid battery then take it back, mis-selling stuff pi$$es me off.