Votronic B2B - poor charging

[arthur49]

Renault Master base 2019 - Alternator 185A

Votronic Battery-to-battery charger VCC 1212-50.  Set to draw no more than 42A from alternator

In Belgium just now and charging whilst driving is poor.  Typically its putting 8A into batteries, whereas a typical figure was 35A.

16mm2 cables with run of approx 4m each

I've checked and done the following:-

- 2 x 100A LifePo4 SOK batteries accepting an equal charge confirmed by using mains charger (they discharge fine as well)

- all connections good; voltage drop minimal from starter to leisure batteries; nothing running "hot" (couldn't get at alternator though)

- starter battery new about 2 months ago: identical AGM stop/start fitted which charges from alternator fine

- bit of verdigris on connection to mega fuse on connection from starter battery so cleaned and "nipped up" connector

- fitted new 80A mega fuse and fuse holder

- temp sensor on B2B correctly fitted and secure

- disconnected Victron MPPT solar regulator just in case it was causing an issue ............

- current at starter battery going to leisure batteries is almost identical to current at leisure batteries

- fridge disconnected

No improvement so I suspect its the B2B that is faulty?  Or could it be the alternator?

Edited September 13 by arthur49

[Labby]

Have you checked for voltage drop on the earth cables , engine/gearbox to body and  starter battery to body ?

[arthur49]

7 minutes ago, Labby said:

Have you checked for voltage drop on the earth cables , engine/gearbox to body and  starter battery to body ?

No I haven't - at my age and with my issues if I go down flat on ground and under van I'll never get up again!😑

[Steve928]

36 minutes ago, arthur49 said:

No improvement so I suspect its the B2B that is faulty?  Or could it be the alternator?

You need to know the SOC of your batteries before you can determine if anything is amiss.

For example if the batteries were in the final 25% or so of charge the B2B would have switched from constant current into constant voltage mode under which the charge current will taper down to zero over a number of hours. For example I charged a Fogstar 105Ah up from about 30% SOC yesterday; the first 45A or so went in at the full capacity of the charger in the CC phase but then it took a further 5 hours of reducing charge under the CV phase.

[arthur49]

14 minutes ago, Steve928 said:

You need to know the SOC of your batteries before you can determine if anything is amiss.

For example if the batteries were in the final 25% or so of charge the B2B would have switched into constant voltage mode under which the charge current will taper down to zero over a number of hours. For example I charged a Fogstar 105Ah up from about 30% SOC yesterday; the first 45A or so went in at the full capacity of the charger but then it took a further 5 hours of reducing charge under the CV phase.

When we set off driving today the batteries were at approx 60% SOC - I use a Victron shunt to measure current in/out which I find more useful than the batteries' BMS.  So would normally have delivered 30A+ .............  but didn't!

[Labby]

37 minutes ago, arthur49 said:

No I haven't - at my age and with my issues if I go down flat on ground and under van I'll never get up again!😑

I do not know about the Renaults , but the engine/gearbox to body earth cable may be under the bonnet .

Or use a jump lead as a temp. earth cable to eliminate it as being a possible cause of the problem

Edited September 13 by Labby

[arthur49]

FOLLOW UP

The earth connections (and all others) are fine.  Fuses and isolator switch fine.

The voltage at B2B input is almost identical to voltage at starter battery, and rises with engine running ie negligible voltage drop

The B2B output remains erratic.

So, my conclusion is alternator is OK but B2B is faulty 

(In Germany now so can't resolve any further and Votronic have not invited me to their factory/dealer to check 😁)

Edited 2 hours ago by arthur49