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Why is my BMV712 smart displaying incorrect low voltage of 'AUX' / starter battery ?

I returned from a weeks holiday, only to be awoken hours after falling asleep by a low voltage alarm.

Having disabled the alarm, a today checked the voltage directly on the starter battery terminals and found it to be fully charged, (13v) as it was still receiving a trickle charge from solar.

connections all seem secure and tight at battery and on shunt, could it be a faulty RJ45?

I have fairly recently replaced the pcb board on the shunt after water came in to contact with the shunt and shorted it, however the new pcb installed and everything has been working fine for a few months, and bo there has not been further water ingress.

any help greatly appreciated.


will-bunce asked
Martin Keogh answered ·

5 Answers

MultiPlus-II: charge separate starter battery?

Can the MultiPlus-II charge a separate (different type) starter battery, or I should plug it into a separate trickle charger?

I noticed that the MultiPlus had a separate starter battery connection but it no longer seems to be there in the MultiPlus-II.

On a completely different topic (which I should make differently), I wonder if the MultiPlus-II can switch between charging the batteries when they are low and using them with the inverter when they are high. Would I need additional devices to control it to do that? (Cerbo GX and VE.Bus Smart dongle?)

trougnouf asked
klim8skeptic commented ·

6 Answers

BMV and starter motor Installation guidlines


I can't find any exampl wiring for a system where the 'service' batteries may get called on to run the sterter motor in the event of the starter battery going flat.

I am re-wiring my boat and have an old BMV and a large starter battery and bank of 4 service batteries. I have a change over switch to allow me to power the starter motor either from the starter battery, or, in the event of a flat battery from, the service battery bank. Will the Smart Shunt handle starter motor currents? This is a 5l diesel engine, so quite large starter currents, I don't have any figures for the starter current draw.

Any suggestions welcome.

regards, Granby

granby asked
xavier-64 answered ·

0 Answers

Lithium Starter Battery


I've received some equipment to upgrade my boats electrical system. However the company have sent me the wrong battery (100ah drop-in lithium) - should be 100ah Victron smart.

Anyway, they are going to do a swap out, but I was thinking if it would be possible to use it as my starter battery and maybe run a few other things from it - deck wash, nav lights...

My system will have 4x 100ah Victron Lithium batteries for the house bank. This is connected to a 12/3000/120 multiplus.

The solar MPPT and Alternator are connected to a 85ah agm battery and that connects to a cyrix li-ct in order to charge the house bank when charge is available.

What I'm thinking is to do the same with the MPPT, but run it through a Battery protect and have the ignition wire for the balmar external regulator also go through a small battery protect - both will be connected to the BMS charge disconnect that I have routed through my BMV 712 relay and set to disconnect at 14.2v.

Main concern is that currently when the Cyrix disconnects when solar charge is occurring the starter gets a quick dose of around 15volts before the MPPT reduces current.

Will the BP catch this quick enough in order to stop it getting to a lithium starter battery?

I don't think the same will occur with the alternator as once the regulator ignition wire goes out the stop off current should be instant, but say if you think I'm wrong.

Hope you can clear this up and maybe give alternatives I haven't thought of.



stocksy asked
xavier-64 commented ·

7 Answers

Orion on alternator without starter battery

Hi everyone !
I am writing to you to know if some people have already connected an isolated Orion tr smart to a vehicle alternator without a starter battery? and if it worked and charged proprely?
I explain the vehicle contains 2 alternators, the second alternator was mounted specifically to take advantage of charging a large auxiliary lithium park (mechanical assembly + belt, no electrical wiring).
The excitation of the alternator is given by the starter battery.
I have a problem concerning the output voltage of the alternator which is 8.7V at no load (belt tightened everything is ok). The wiring is quite classical (+ and - input on + and - alternator). The negatives, alternator housing, are well connected to the truck chassis, R=1 ohm. Then I tried to connect to the input of the Orion and there my multimeter shows me 32 V DC (and the Victron application too)!
I wonder if the alternator has a defect because according to me the alternator is supposed to provide a stable voltage and therefore the Orion should work quite normally. I wanted to know if some people have already done this type of assembly with an isolated Orion on an alternator without starting battery and if it worked.
I would like to specify that this is not the first Orion I have installed.
Thank you all for your help.
Sorry for my english i'm not native.

mathiasotf asked

0 Answers

SmartShunt 500a Aux Starter low

I have the Aux port wired to my generator battery 12vdc starter battery and it was reading correctly. I ran an update and now the voltage is readin 4.5 V ish. The battery is still reading 12.6v at the smart shunt when I use my voltage meter and is fully charged. I assume the update might have cause it to reset something to an incorrect voltage setting but I can’t find anything. Both main and aux batteries are 12v and I verified wiring per diagram from other posts.

hayloftllc asked
derrick thomas answered ·

3 Answers

Cyrix-ct start assist with drained battery


I have a boat with 1 Engine, 1 Starter battery and 1 auxiliary battery.

I would like to use the Cyrix-ct-230 to automatically charge the aux battery once the starter battery has been charged. With the added benefit of having a start assist switch from the aux battery in case the starter battery has been drained.

My question: How would the Cyrix react if I use start assist to combine a full aux battery with a completely drained (or dead) starter battery? Would the Cyrix refuse to connect? I'm concerned that the drained/dead starter battery would drain the aux battery.

kemp-arve asked

0 Answers

Correct trickle charging method for starter

Hi all - I am very confused about the above topic and was hoping for some input. I have a Citroen Relay 17 reg (which has a smart alternator) which I'm converting to a campervan. I don't use it everyday, and I've been suprised how quickly the starter battery runs down (the immobiliser in particular is apparently a thirsty one). I'm planning out my electrics, but keep reading conflicting info about the best way to keep the starter battery topped up. My starter battery is not a Victron, but the original battery and for economy sake I don't want to change it yet as it's fine.

One method is to not even link the starter battery to the rest of the camper at all, and just use an external trickle charger when needed, however to me this seems like a nuisance. Some people also seem to just disconnect the battery for longer spells and keep the van turned over otherwise, but this is apparently not the best for the battery (not sure how true this is - can only find anecdotal info).

If I design my system to trickle charge the leisure battery then I'm confused between whether I should do this fromthe victron dc-dc charger as I have been told it causes problems when using an MMPT solar charger and a multiplus (which i have already purchased - i have 2 solar panels). Others have said I can just use a cyrix while others a cyrix and a dc-dc charger.

Keeping the starter battery topped up is my priority - having the alternator charge the leisure batteries is just a bonus as I've probably overshot on my leisure battery capacity and my solar panels, and I will be mostly on site where i have shore power, so should never (in theory) need to rely on my alternator to give me a boost. But I want to eliminate the risk of my starter going flat, and reduce the maintenance needed when not inuse.

I'm really starting to tear my hair out on this one - really would appreciate some advice or links! Thanks all

Dylan Tucker asked
kevgermany commented ·

2 Answers

Charging vehicle battery from DC to DC charger with MMPT Smart Solar

Hi all - I have a Citroen Relay that I've started the conversion process on. One thing I'm noticing is how quickly these van batteries drain when not in use due to the immiboliser and other gadgetry. I was hoping to come up with a way to have the vehicle battery at least trickly charged so this problem was mitigated. I so far have 2 leisure agm's and have started to piece together the components for a system, with 2 solar panels, an MMPT charger and a multiplus (all victron). I was considering a DC-DC charger too, but have started reading that it can be hard to get that working with an MMPT charger but have little other info on that side of things. Is that true and are there solid workarounds? I'm less worried about needing more power for the leisure batteries as if anything have probably overshot, but I really do want some sort of way to keep the starter battery topped up while sitting on the drive.

Thanks so much

Dylan Tucker asked
Sarah answered ·

1 Answer

What's happened to my starter battery widget in VRM?

I've been monitoring starter battery voltage in VRM for many months but suddenly it's gone, both as a graph on its own and as part of a custom widget.

I think there was a mandatory firmware upgrade to the BMS this week when I Bluetoothed into it - could that have lost it??

markj asked
snoobler answered ·

2 Answers

Blue Smart IP67 short circuit protection and thruster motor


I have bow thruster motor, which is 12V and ~500Amps and a dedicated lead acid battery for this bow thruster. I am going to use Blue smart IP67 12V/25A to charge this battery.

Is it safe and okay to leave blue smart connected to battery, when bow thruster is in use?

Or it is must to disconnect positive wire from battery, when motor is in use?

Blue smart states that it has short circuit protection, but does this protection is fast enough to disconnect charger from battery, when high power bow thruster motor is in use?

vilius-jakas asked

0 Answers

Trickle charger from leisure battery


I am looking for a trickle charger to maintain my starter battery charged from my solar panel.

I wonder why Victron do not provide such product, like AMT12
It is really an issue for me and unfortunately, since brexit, I can't buy AMT12 from France...

@victron guys, do you plan to add suh product?


anayrat asked
kevgermany commented ·

7 Answers

Multiplus 12/800/35 to trickle charge Lead Acid starter battery.

Is it ok to use the 1A trickle charge output of the Multiplus to charge a lead acid starter battery when the main batteries house batteries are Lifepo4?

sweyn asked
pwfarnell answered ·

1 Answer

Show Starter Battery Voltage on GX Touch


we have a Cerbo GX with GX Touch 50 installed on our boat and are desperately looking for a setting to display the voltage of the starter battery. We have a Smart Shunt 500 in the system and can only display the voltage of the starter battery via Bluetooth. Is there also a way to display the voltage in the system overview on the Touch 50?

savannah asked
maika answered ·

6 Answers

Argo which terminal for Alternator sense?

Hi, I've installed Argo FET split charger to charge my starter and 2 (separate) LFP banks. The Balmar MC614 Regulator states to place the Alternator voltage sense wire onto the largest bank if using a split charger, so in my case that would be the 400ah LFP bank.

Just a little concerned that this will potentially expose my starter to too much current and force it into a high voltage state.

I did think that using the MC614 Batt temp sensor on the starter battery might help. Other option would be to place the sense wire onto the starter battery, but then would that not prevent the LFP banks from charging?

Hope someone with a better understanding of this can help.



stocksy asked
jwfrary answered ·

3 Answers

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