The shunt should be between the batteries and everything else before it gets to earth otherwise it can't see what's going in and out of the leisure batteries.
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[Guide] DC-DC Charger (for leisure battery) -- How I Done It --
- Thread starter Dellmassive
- Start date
Like this ... Edited to add inverter
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Your earth connection at the left hand bottom is defeating the shunt
some observations:
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A- this looks fine, but I've had issues with this style of breaker switches getting hot causing volt drop when pulling current - so keep an eye on it . . . if it starts to get hot swap out for a MIDI or MEGA fuse.
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B- is this the main chassis ground connection in yellow? - of so the green? should be both the LB1 + LB2 NEG feeds.
both battery NEGS need to got to the SHUNT, then one common GROUND from the SHUNT to the van BODY. Also the gauge of the cable needs to be the same thickness as the main POS as it will be carrying the same high current . . . so if you use 150A cable for the POS, then you need 150A cable for the NEG . . .
if 2x 150A POS then you need 1x300A for the main NEG from the shunt ( same as you have done with the main starter battery feed)
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C - where is the second battery? - each battery needs a fuse next to the POS interlink cable.
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D - Fuse should be on the POS side of the battery. (technically it could go on the NEG side, but depending on the circuit layout the power could fin an alternate route to ground so POS is always best place)
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E - the second LB2 should have a direct connection to the shunt, it can go to either the LB1 or the shunt, whatever is shortest.
yellow or blue is ok, red is not right, the shunt will not read the power correctly.
F - where is this master switch in your schematic?
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G - can you post a pic of your starter battery NEG terminal and connections
H - Inverter NEG connection needs to do direct to chassis ground, same as all you loads NEGS to chassis. . . ONLY the LB1 & LB2 NEGS to shunt - then shunt to chassis. credis to @Grim Reaper for spotting that one.
I - Fuse layout - this is where the fuses would normally be, as close to the battery POS connections as possible.
J -
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The 12v IGN trigger isnt needed for most DC-DC chargers as they will AUTO switch on when they detect 13.2v or above from the starter battery.
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what the IGN sense wire does is allow the DC-DC to stay running to a lower voltage than without the wire. . . . its not a hard ON/OFF signal.
But it will demand a drain on the alternator where a smart alternator is fitted to keep charging the leisure batteries when the van decides it doesn't need it to charge it's starter battery
Your inverter negative is in the wrong place, it defeats the shunt as well or rather any use of the inverter would not be logged on the battery monitor.
I've added that observation to the list above, well spotted.
Wouldn’t the DC-DC charger trigger the alternator regardless? Even if the starter battery was charged, the alternator wouldn’t shut down because the DC-DC would be pulling 30-40A. If the alternator did shut down, the starter battery voltage would soon drop enough to call the alternator due to the load from the DC-DC. That’s how I understand it, but I may be wrong.
Yes, thats correct . . and what i saw during testing . .
The starter battery rapidly drops in voltage causing the alternator to kick back in . . . but it will cycle on/off a lot.
without the IGN feed the DC_DC will switch off at say below 12.6v and then back on above 13.6v - causing the cycling effect.
its DC-DC charger specific on how and when they will turn on/off.
WITH the IGN feed the dc-dc will stay on to a much lower starter voltage, say 11.9v which reduces the cycling effect. . . .
without IGN feed average ( Traditional ALT) on/off : 13v - 16v
with IGN feed average (Smart ALT) on/off : 11v-16v
DC-DC on/off voltages listed here - [Guide] DC-DC Charger (for leisure battery) -- How I Done It --
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AUTO VSR feature listed here - [Guide] DC-DC Charger (for leisure battery) -- How I Done It --
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you should start you own thread @Epic-Rob . its a nice setup you have.
would be nice to keep it all in one place.
start your own build thread here:
then you can add your setup and mods going forwards . . . well help out on that thread too.
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As an aside, whilst we’re discussing battery fuses, I’m a big fan of these. I’ve used them in various boats over the years & they are a great bit of kit.
kojaycat.co.uk
Tinned Cube Fuse Battery Terminal
Tinned marine grade positive battery terminal for use with ceramic cube fuses rated from 50 amps to 300 amps.
kojaycat.co.uk
did think about it but am not very media friendlyyou should start you own thread @Epic-Rob . its a nice setup you have.
would be nice to keep it all in one place.
start your own build thread here:
then you can add your setup and mods going forwards . . . well help out on that thread too.
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Cheers for the info. I used the ign feed when I fitted my Orion, I already had one available under the passenger seat & I didn’t trust the new fangled auto sensing. I’m a binary kinda guy & I wanted to be sure that if the engine was running, the battery was charging. None of that ambiguous maybe/maybe not nonsense
@Salty Spuds - yes me too.
(but for testing i have that connection on a bullet connector so i can test DC-DC units with/without the IGN feeds)
i have the Factory T6 OEM LB, so had the fancy BCM Engine RUN feed fitted from new . . it only goes +12v live when engine RPM is detected . . .
so much better than the plane IGN feed. ( which could cause excessive starter battery drop if the IGN is left of for too long without the engine running.)
BCM engine run feed mentioned here: [Guide] DC-DC Charger (for leisure battery) -- How I Done It --
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(but for testing i have that connection on a bullet connector so i can test DC-DC units with/without the IGN feeds)
i have the Factory T6 OEM LB, so had the fancy BCM Engine RUN feed fitted from new . . it only goes +12v live when engine RPM is detected . . .
so much better than the plane IGN feed. ( which could cause excessive starter battery drop if the IGN is left of for too long without the engine running.)
BCM engine run feed mentioned here: [Guide] DC-DC Charger (for leisure battery) -- How I Done It --
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OK Q on cable size and fuses.
from Starter to DCDC i have 100A cable with the 70a fuse
Between (connecting) the 2 batteries again 100A cable with ??a fuse OR is 50amp cable with a ??a fuse.
fuses in Shunt, inverter and DCDC to POS terminal - what are you rating those at?
supply feed ok with 50A cable and appropriate fuse of not higher than cable load?
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.
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.
There's a handy rating calculator on this page, about halfway down..
You want to be aiming for under 3% drop over the length.
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
You want to be aiming for under 3% drop over the length.
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