So new Merc is wired direct from Vehicle battery to leisure side on +ve with NO VSR or anything else in the way (AAGGGH!!)
Is it best to get one of these:
www.onboardenergydirect.co.uk/shop/Victron-Cyrix-12-24V-230A-Intelligent-Battery-Combiner-CYRIX_12_24V_230.html#SID=200
OR could I use one of these, which would have more options in terms of monitoring
www.onboardenergydirect.co.uk/shop/Victron-Smart-Battery-Protect-BP-220-Amp.html#SID=314
??
TIA
Funilly enough,I have both of those items
OK, one bit is very simple ..... the Victron Battery Protect devices are an absolute no-no for fitting in that setup. They don't make it clear enough in their information until you read the manual in detail, but the Battery Protect should only ever be used in a uni-directional configuration. There is nothing that physically stops the current going in the opposite way, but it will likely catastrophically damage the unit.
Where you
would use the BP is in a circuit from the battery to the Loads, and you had the charging device on a seperate leg coming into the battery (so not via the BP). Or to control Lithium Battery Charging (turn the BP on and off via a temp controller say).
Anyways, you said on another post that
"... The cable running from +ve vehicle side to +ve Leisure side is pretty hefty 10mm by the looks ..." and there is no cable protection (e.g. Fuses)?
If that is the case, what I think you need is a complete Split-Charge kit with fuses, holders, PROPER cable and a VSR/Battery Combiner (for example, one of these ....
https://wildebus.com/store/index.php?route=product/product&path=79_85&product_id=110 )
10mm Cable - if you are referring to 10mm2 - is totally inadequate for a VSR Split-Charge. If it is 10mm diameter, then it will probably (educated guess here) be a 16mm2 cable, in which case you could keep that cable (still add fuses!!!) and use a VSR, or preferably a Battery Combiner such as this unit -
https://www.onboardenergydirect.co....20a-intelligent-battery-combiner.html#SID=200
That would be the one I would recommend rather than the 230A unit you linked to as it is very unlikely you would ever be able to delivery over 100A from the Alternator or have a battery setup that would take that much. For that reason, the 230A Victron model is overkill as well as being over twice the price.
If you were to fit the 230A unit for a particular reason, you should also upgrade the cable from the proposed 16mm2 to 25mm2, 35mm2 or even 50mm2 if a longer run (say batteries at the back of the van).