DCDC low voltage issue

[Salty Spuds]

Measure the actual voltage drop, i.e. measure voltage at the start and end of the cable run whilst charging in bulk mode to see if you have a problem. If voltage drop is the issue, shifting the victron may not help - will just switch the issue from input to output…

^^^^^ wot he said

 

[t0mb0]

You could just move/swap/reconnect/rewire components until it starts working but this could be a time consuming and expensive process unless you get lucky.

I could advocate a measurement driven approach, to actually diagnose the problem which will then enable you to do a targeted fix. All this entails is simply measuring voltage at all the relevant points whilst bulk charging until you find the point at which the voltage is dropping.

 

[t0mb0]

post some new pics of the cables,

connections on dc-dc,

connection to ground,

connection to starter battery,

connection to LB,


what size cable are you using for each bit of the run.

also that ebay trip switch in engine bay is not advised ( they get very hot and add a large resistance to cable) - try swapping out for a MIDI fuse & holder. (thr proper marine grade ones are ok, just not the ebay cloans)

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Yeah, could be the trip switch. Measure voltage on each side to check if this is where it’s dropping.

 

[DXX]

12v Planet also do a tinned cable for not a great deal extra £, this will improve reliability in areas exposed to moisture and road salt.

 

[AussieMick]

A high resistance in the fuse holder is not unknown either. Put a volt meter across the fuse and see if it has a voltage reading. Should be zero if the fuse and holder are ok.

 

[Adrob]

Ok Ta. I'll get measuring when I'm back from this trip with the family. (Getting the multimeter out now might not go down well!).

Red & Black Battery/Starter/Welding Flexible PVC Cable Wire 110/170/345 Amp 16mm 25mm 35mm by MKGT® (10mm² Red, 10 Meters) https://www.amazon.co.uk/dp/B07QYN5...abc_DW7W5WFE1XFNXMMD1GPY?_encoding=UTF8&psc=1

This is the new Cable.

I've also added an earth to the body, as a trial because I couldn't get back to where the converters have earthed it all (the tiny cables off the LB).

Nite: the other big cables go to the EHU victron.

 

[Dellmassive]

the cable thickness looks ok from the above pics.

is the ground cable chassis connection good metal to metal . . ?

im still wondering about those trip/breaker fuse switches . . ? - what rating are they? 20/30/40/50/100A ?

what length are the cable runs.?

can you get a video clip of the APP again . . . or the multimeter screen? - while its running.? (post the google pics link etc)

can you swap them for 50A MIDI fuses and holders?

https://amzn.to/2Y7ZnMF

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https://amzn.to/38nkoVr

.

https://amzn.to/3jqisBS

 

[Adrob]

I've ordered the midi fuses, they arrive on Thursday. The first problem I had was definitely related to the circuit breaker, sent that one back and bought different ones.
But I fear I tried running it on bulk without a fuse and the issue was there. Can't remeber. Will measure in the week too.

Think they're 50 or 60amp can't remeber.

Some charge is def getting though, as I ran the engine earlier to give it a boost and it worked.

Thanks again

 

[oldiebut goodie]

I would check out that earth point as well - it looks as though it is the second one to be placed there - it doesn't look as though it was prepared by cleaning to bare metal first. ( I wonder why it is outside in the elements being subjected to salt spray and crap instead of internal)
If that is faulty it will cause voltage drop - people forget that you need a complete circuit not just positives.

 

[AussieMick]

I agree, that ground point looks pretty dodgy.