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starter battery

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
Kevin Windrem answered ·

3 Answers

Cyrix CT and engine starting in parallel
I have a cyrix CT 120A relay between the starter battery and the service battery which is a victronenergy agm deep cycle 110 ah.
Obviously the cyrix does a start with the batteries in parallel most of the time, that is, if the batteries are in solar charge or if the batteries are fully charged.
In your opinion is it harmful to the agm victronenergy?
I believe it is absolutely not harmful, as during start-up, the smartshuunt only marks 30A of absorption on the agm for less than 1 second.
I think This is because the resistance of the positive cable in series between the batteries and starter motor means that 80% of the starting power is supplied by the starter battery.In fact starter battery have a much more short and more thick cable, that cause a lot less drop voltage and supply more amps to the motor. But some peaple say me that's is no good.... 
In fact, the total absorption for starting is about 120A and are divided as follows: 30A on the agm services and 90A on the starter battery.
Furthermore, the data sheet of the agm victron says that it tolerates inrush currents of 500 CCA at - 18 degrees, and absorption of 880 amperes for 5 seconds.
So 30 amps 2/3 times a day for less than 1 second shouldn't hurt.
What do you think?
However, I have equipped the cyrix with a switch on the negative of the coil to exclude it during start-up.

francesco asked

0 Answers

Charge starting battery: BMV 712 relay vs MPPT SmartSolar Load Output

I have an older PWM charge controller which will charge both the House and Starting batteries. I am getting more solar panels and want to upgrade to MPPT, but MPPT charge controllers generally do not support 2 battery banks.

  • Assume I start with a single MPPT SmartSolar or BlueSolar controller

What would be the best solution?

  1. I could use the Load Output and wire that directly to the starting battery, and set a rule for the Load output to turn on the load when the house battery is between X and Y volts. Pros: doesn't require more equipment. Cons: the bigger MPPT controllers don't have the Load output at all, so I'd have to stay with the lower capacity models.
  2. I could get a BMV 712, and use its relay output to control a relay which connects the House and Starting batteries, and use a similar voltage-based rule (On between X and Y volts)
  3. Some other Victron product - battery isolator or combiner or...?


xmd asked
xmd commented ·

2 Answers

Starter battery voltage monitoring with isolated systems

Hi there,

I currently use the aux input on my BMV-712 and the Cerbo GX/VRM to monitor the start battery voltage in my boat. Being an aluminium boat I am making a few changes to the system to ensure that electrical systems are isolated from the hulls and that the start battery system is fully isolated from the house battery system. This means that the aux input on the shunt won't be able to read the start battery voltage any more, as they won't have a common ground.

What other ways can I get the start battery voltage into the cerbo GX and VRM for monitoring purposes?

A little more detail on the system if it helps:

- 2 x 25.6V 200AH Smart Lithium

- BMV-712

- Multiplus 5k

- 4 x MPPT 100/20

- Cerbo GX

- Orion 24/12-70 for running 12V house loads

- Swapping the Orion 12/24-20 for a Orion TR Smart Isolated 12/24-15 for charging the house from the start batteries

If only the Orion TR Smart could do communications over BT or VEDirect this would be easy.

justmurph asked
frank-schultealbert commented ·

2 Answers

Use of cytrix to join different kinds of battery for starting and potential winch use.


I am fitting out my vehicle for a remote expedition and will probably use Victron but have some questions.

The house batteries will be Lifepo4 (24 volt) and the battery to start the truck will be 24v (lead acid or AGM) I want the solar to charge the start battery once the house batteries are replenished and also want to be able to join the two battery banks together in an emergency to either start the vehicle if the starter battery is flat or to run the 24v winch if it's needed.

Is this possible and will the different battery chemistry cause issues.

hopeless-wanderer asked

0 Answers

Use a Orion TR Smart to charge a Lifepo4 via the leisure batteries

Hi in my MAN TGE Van I would like to use the Orion TR Smart to charge my new Lifepo4 battery through the alternator/leisure battery. So far this is a common setup. What I'm missing is a solution for shore charging. Is ist ok to connect the shore charger to the starter battery and then the load the Lifepo4 battery through the Orion TR Smart?

Best Kirsten

kstyler asked
Stefanie commented ·

3 Answers

Minimum starting battery size with Smart 12/12 -30A charger and lithium battery in sailboat.

20 hp Yanmar w/ 60 amp alternator. 125 amp hr lithium house battery What is the minimum size AGM starting battery required in a two battery system. Is 20 amp hr too small ?

don-hudak asked
Stefanie answered ·

1 Answer

MultiPlus Trickle Charging in combination with Orion Tr Smart


we have a standard MultiPlus 24V installation with Lithium batteries (24V) in a truck camper (very similar to the Victron van install, but 24V). To charge while driving, we are using an Orion Tr Smart autodetecting if the engine is running. So far, everything works fine.

Now, I was wondering, if I can use the trickle charge output of the MultiPlus to charge the starter batteries during longer phases of not driving? We are using a cooling box in the drivers cab, that I can't directly connect to the house batteries...

- Is the trickle charge output a proper charger with settings for the starter battery type?

- Would the Orion Tr Smart detect trickle charging as an engine start, due to the increase in voltage? Am I creating a loop this way?

- What would be an alternative?

Thank's so much for you input!

kiko asked
jelle commented ·

1 Answer

Orion DC-DC draining starter battery?

I installed an isolated Orion DC/DC Smart charger in our Sprinter a while back and we started having issues with the starter battery not too long after (van wouldn’t start). We switched the battery yesterday to exclude that it wasn’t holding charge and checked the voltage of the new one. In the evening it was showing 12.78 V. This morning (ca. 16 hours later) it was at 12.4 V. I’m wondering whether the Orion’s bluetooth/blinking led account for that drop, and if it makes sense to add a switch and turn the Orion off when not using/running the van for longer periods of time. NB: the VictronConnect app indicates that the Orion turns off when the engine does, so it doesn’t seem to be an issue of setting the right shut off voltage. Any help/advice much appreciated!

coenjo asked
raywells1 commented ·

2 Answers

Charging Starter and Bow thrust battery from Leisure battery system what size Orion Tr

Hi All , I am living off Grid on a Narrowboat and have a big solar system that supplies pretty much all my power needs 95% of the year and I have back up Gen for the rest . I dont therefore Run my Engine much so except We do move the boat every 2 weeks briefly for service . This means the Starter and Bow thrust batteries get used a little but dont get a proper recharge so are sitting in PSOC most of the time sulphating . I would like therefore to syphon some power from my Solar system ( I have plenty to spare ) into the starter and bow thruster batteries until they are topped off . Currently they are Sealed LA batteries but when replaced will prob be AGM so I dont want to overcharge them . Is Orion Tr good for this ? and if so what size is best for 2 x 100Ah Sealed LA or AGM batteries , they wont be high DOD so prob dont need a very high current . Also what is difference between Isolated and non Isolated and which is best for this application ?

In addition what does the smart bluetooth tell me ? will it tell me SOC of the starter and thruster battery or will I need a Smart Shunt for that ?

Sorry for all the Questions

Simon Phillips asked

0 Answers

170 Ah AGM Supercycle as starter

Hello, I have a Victron AGM Supercycle 170 Ah battery that i am moving from my house battery as i got lithium. Can I use it as a starter battery for my Yanmar 4JHE. The specs say it has 600 CCA which is super low for a battery that big.


seahaul asked
alan answered ·

2 Answers

Best way to jumpstart a Sprinter with Victron LiFePO4 batteries and a smart alternator

Hey there, I am trying to figure out the best way to add a feature to a sprinter van where I can jumpstart my starting battery off of my lithium coach battery set. I was thinking of some sort of momentary switch on the dash that could be held to act as the jump start in the event of starter battery depletion - but only that.

I have been trying to work in a cyrix-lt-cr but it seems like it has a 30 second hold, and only engages at certain voltage levels?

The big concern I have is with the smart alternators and ensuring the ability to isolate the lithium batteries from it so I don't overcharge the lithium or burn out the diodes in the alternator. I currenty use a DC/DC buckboost charger to modulate the charging current to a safe level, but short of installing a second buckboost I'm not sure how best to configure a jump start feature safely

David Heckley asked
llubi answered ·

2 Answers

BCD 802 battery combiner cranking current

Good morning,

The boat has 2 Yanmar 220hp engines, each with their own AGM starter battery. We also have a Fischer Panda 5000i NEO generator. Due to lack of space, we are cranking the generator through one of the engine's starter batteries. The problem is that if while the generator is running the engine starts, the generator control panel shuts down (due to battery undervoltage) and the generetor itself also shuts down.

To prevent this, I was thinking that I could install a BCD 802 battery combiner (80A continuous current), so that the current to start the generator could be drawn from both engine batteries. However, Fischer Panda infomed that the cranking of the generator could reach 200A max, so the question is whether the BCD 802 can support this cranking current.

Thank you for your attention,


fgarcia asked

0 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
kyleolmstead commented ·

1 Answer

connecting smartsolar directly to starter battery?

I plan on setting up some solar panels only for charging the starter battery and nothing else. I don't have room for a secondary battery in my situation. Can this be done? I assume the smart solar is smart enough to keep from over charging the battery and that the alternator and current draw when starting the vehicle won't cause problems. Or do I need more equipment? I was thinking perhaps a smart battery sense but other than that I should be fine?

sqenixs asked
sqenixs edited ·

0 Answers

How to monitor the starter battery with my BMV-712? Wiring seems very complicated for my installation.

0 CB_Midkiff asked · Dec 10 at 4:27 PM

I have a housebank, which is charged by a Smart Solar MMPT 100/50 and connected and supervised by a BMV-712 via shunt. In addition I have a starter battery which is not connected at all to this house system. However I would like to monitor the starter battery also via the auxiliary input of the BMV-712.

Fig. 3 of the BMV-712 wiring diagram


Issue is now that the starter battery is about 5m away from the housebank and a cable connection for high loads would be quite complicated. From the BMV-712 manual I did see that normally I would have to connect the minus of the starter battery also to the shunt via a very thick load cable and an additional thin plus cable to the B2 port of the shunt.

Is there an easier way to connect and monitor the the starter battery via BMV-712?

Would it be possible to use the Smart Battery Sense device and connect it via bluetooth with the BMV-712 as an auxiliary input for monitoring the starter battery?

tuco asked
Guy Venuti answered ·

4 Answers

HELP - Leaking starter batteries / rotten egg smell - Travelling across Africa - Stuck

Hello Community,

Hope someone can guide me :-)

We are in a professionally built expedition truck with Victron systems. Over the last two days we have been smelling rotten eggs. I started with the toilet but ended up at the starter batteries :-(

Both starter batteries are leaking (2 x 12v series).

Q1 Is it usual for both starter batteries to fail together or is this symptomatic of an external issue ( overcharging issue or something else)?

We are parked up (Corona 19) with a shore supply feeding a Pheonix Multiplus that charges our leisure batteries and starter via a Cyrix-i 12/24-120 bidirectional voltage sensitive relay. A Victron MPPT solar charger is a second charging source (added a month ago to replace a PWM unit).

About two days ago the inverter displayed a Bulk Protection alarm. And I reset it. I didn't know what this was, but the community has told me that it means the max bulk charging time of 10 hours was exceeded. I suppose this is associated with my problem.

I noticed yesterday that my MPPT was generating 17A, but the BMV indicated only a few amps charging the onboard leisure batteries and I wondered where the rest was going as I had not much load switched on. I guess it was going into the started batteries.

Q2 Can anyone through some light on what is going on? Have the batteries failed as a result of a system issue or of their own accord and just need replacing?

Many thanks in advance to responders.



Multiplus & MPPT have identical charge settings (bar current limit):

Vab = 28.8v

Vfl = 27.6v

Current limits are 45A and 30A respectively.

Voltage across starter battery terminals (chargers off): 24.8v

Voltage across leisure batteries (from BMV) (chargers off): 25.5v

Voltage across starter battery terminals (MP charger on): 27.6v and climbing slowly

Voltage across leisure batteries (from BMV) (MP chargers on): 27.7 and climbing slowly


The starter batteries are fully sealed maintenance free units.

The leisure batteries are Victron AGM 220AH (2 in series for 24v)


Starter batteries last replaced in May 2016.


System Diagram

1 = Starter Battries

6 = Cyrix-i 12/24-120

9 = BMV 602s shunt

8 = Leisure batteries

11 = Inverter 24/3000/70 Phoenix MultiPlus



I measured the voltage across each of my series 12v starter batteries: 13.35v and 11.25v.

The latter seems low given they have been on charge for 24hrs +.

Does this mean that the starter battery voltage is low overall 24.6 and this would mean battery voltage does not reach Vab and stays in bulk or just make absorbtion and draws lots of current. This causing both batteries to overcharge and leak?

Have I answered my own question? I don't want to rush out and buy two new starter batteries until I understand the problem. They cost $$$.



As suggested by respondents, I charged the under-voltage battery overnight on a 12V charger. This morning the on charge voltage was 12.1v and this fell back to 11.4v within 20 mins after being taken off charge.

The other battery was at 13.06V this morning.

Q1 I guess this means this battery is toast and needs to be replaced?

Q2 I intend to replace the pair (they are 4 years old) - any reason not to?


I replaced my starter batteries and everything is fine. I have ordered two battery balancers, one for my starters and one for my house batteries.

Thank you all respondents for helping me out.


davidq asked
davidq edited ·

4 Answers

Voltages for regular (non-deep discharge) car battery


I just bought a small SmartMPPT 75/15. It works well, but I notice it is preset for " Victron deep cycle" and I have a "regular" (probably AGM) 65Ah VW car battery. I understand from this post that charge voltages do not vary much, but I worry about the discharge load cut-off.

Any advise on the settings, all of them, but mostly the discharge voltage?


cybermaus asked
snoobler answered ·

1 Answer

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
Justin Cook - Bay Marine Supply USA answered ·

4 Answers

How do i connect easy solar multiplus to starter battery?

Section 4.4.1 in the manual states “The Multiplus compact has a connection (+) for charging a starter battery. For connection see appendix 1”

My questions are;

Where is apppendix 1? (Not visible in appendix A)

Never mind appendix 1, where is the connection?!

All other questions on this forum seem to be advised to buy yet more victron products- a cryx - but if the manual is correct this is not necessary and is simply victron trying to sell more needless products.

If I just connect the two banks with a jump lead they will equalise, could I simply hard wire this with correctly rated cable? but is this bad practice or unsafe when using a sterling Alternator to battery charger which prioritises starter battery thus negating the priority charge process. The cryx or a cheaper simple relay would get around this, but given the functionality built in to the multiplus already I woukd like to take advantage of that. And avoids having to connect the banks.

Thanks in advance!


will-bunce asked
will-bunce answered ·

3 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
dazey77 edited ·

2 Answers

Is it possible to add my old starter battery to my household bank

Hi everyone,

I'm currently converting a campervan and after some issues with the engine not starting in one go, I'm about to replace the starter battery. I think the main problem was the battery not always being able to supply the high power demand.

I've got two solar panel arrays with two MPPT controllers. Linked to two lead acid batteries in my main bank. The starter battery is also lead acid. I was wondering if it's possible to reuse the starter battery with the two others. The Ah are different and so are the manufacturers. The starter battery is 100Ah and the other two 190Ah.

I've read some conflicting answers online and hope someone can give a definitive answer.

Thanks for the great products Victron!

ricksouth asked
dazey77 answered ·

1 Answer

How to properly protect starter batteries

we have an old Mercedes Benz NG 1428 truck with a 16.000ccm engine. I do not exactly know, how much current is drawn at the start fo the engine. The cables are 100mm2. I think it could reach as much as 1000A for a very short period of time.

The vehicle draws some current even having everything turned off. I would like to protect the starter batteries from going low. I woud also like to remotly (Bluetooth) controll the connection of the starter batteries to the system als well as reading the voltage.

What would be the proper devices to do this. I think I understood, that a Battery Protect is not the way to go, as current would flow in both directions while starting the engine and then loading the batteries from the alternator. Right?

Is there an alternative? Cyrix?

Regards, Kilian

kiko asked
jwfrary answered ·

1 Answer

How to charge starter battery with lifepo4, 800va multiplus, smart mppt

I'm trying to buy a new setup for a campervan which will have a lifepo4 leisure battery and a lead acid starter. I need to be able to charge the starter battery from solar and mains hook up but I've noticed that the 800 multiplus only has a 1a feed to the starter which isn't enough and I can't see any way to connect the solar controller up to both at the same time. I'm going to use an Orion smart to charge the lifepo4 battery, is one possible solution to buy a second Orion to charge the starter from the lifepo4 circuit once it is charged?


mistadave asked
emarges answered ·

1 Answer

Using SmartShunt 500A with starter battery on car

Forgive me for being a novice here, but I'm trying to find an easy to install, safe Amp and volt meter to monitor the battery on my car that has an intermittent draw. I need to have something permanently installed that will give me the voltage on the battery as well as the amp draw so I can see 1) if the draw is active so I can trace it, and 2) how long I have before the battery dies. The battery is under the passenger seat, so it is basically impossible to check this with a handheld meter without taking the seat out. Thus the advantage of the bluetooth permanent install here. Can the bluetooth SmartShunt be installed on the starter battery or just a house battery on an RV, or does it even make a difference? And, it looks like I can get all the data I need from this device, am I missing something? Any help would be very much appreciated.

ben-frobig asked
ben-frobig commented ·

2 Answers

CYRIX-LI charge and BMV 712 settings for overcharge protection

I have a 200Ah lithium battery bank connected to my starter battery/alternator via a Cyrix-Li Charge 230A controlled by the BMV 712-Smart.

It's currently configured to only connect when the starter battery is over 14.1V (indicating that the engine is on) and to cut off when the starter drops below 13.7 (when the engine turns off). I'd like to add another condition that my lithium battery bank must be below 95% to protect against overcharging. Not having luck with the state of charge. Anyone have guidance?

Desired Logic:

ENGINE ON, BANK < 95% = Closed Circuit (aka charging)

ENGINE ON, BANK > 95% = Open Circuit (aka not charging)

ENGINE OFF, BANK < 95% = Open (aka not charging)

ENGINE OFF, BANK > 95% = Open (aka not charging)

evolutionyst asked
evolutionyst edited ·

0 Answers

How does the start assist on Cyrix ct? I have a problem
hello, I purchased the cyrix ct 120A relay.
I already had a similar relay from another brand, not bidirectional but unidirectional.
I installed the Cyrix as shown in the diagram: 86 chassis, 30 start battery, 87 service battery, 85 start assist, on the positive service battery with switch.
But there is a problem: acting on the start assist, the cyrix should close for 30 seconds and then open.
instead it is always closed. and the only way to open it is to disconnect the negative contact 86.
Did it arrive defective or am I doing something wrong?

buongiorno,ho acquistato il relè cyrix ct 120A.
Avevo gia un rele simile di altra marca, non bidirezionale ma monodirezionale.
L ho installato come da schema: 86 telaio, 30 start battery,87 service battery, 85 start assist sul positivo service battery con interruttore.
Ma c'è un problema: agendo sullo start assist, il cyrix dovrebbe chiudersi per 30 secondi e poi aprirsi.
invece  resta chiuso sempre. e l unico modo per aprirlo é staccare il contatto negativo 86.
Mi è arrivato difettoso oppure sbaglio qualcosa?

francesco asked
francesco answered ·

3 Answers

Lifepo4 house bank and AGM starter with 12/3000 multiplus

I have created 2-12.8v 300 ah LiFePo4 batteries to be wired in parallel to the Multiplus on my sailboat. I have an AGM starter battery. If I setup the charging for my LiFePo4, the float is higher than I want for the starter battery. (14.3 absorption and 13.6 float). I would like to charge the starter battery with the Multiplus. What voltages does the Multiplus use on the trickle charge output? Is it even possible to properly maintain an AGM starter battery, when the charging profile is setup for LiFePo4?

ericbjr1 asked
Justin Cook - Bay Marine Supply USA answered ·

1 Answer

Calculating Starting Battery Size

Hi All,

I have a requirement to supply 3 battery banks to start 4 engines.

Engine 1: 24VDC, 2 x 7.5kW Starters (330ah Victron AGM Battery Bank, Skylla TG 100Amp Charger)

Engine 2: 24VDC, 1 x 6kw Starter (330ah Victron AGM Battery Bank, Skylla TG 100Amp Charger)

Engine 3: 24VDC, 1 x 5.5kw Starter (165ah Victron AGM Battery Bank, Skylla TG 50Amp Charger)

Engine 4: 24VDC, 1 x 5kw Starter (90ah Victron AGM Battery Bank, Skylla TG 35Amp Charger)

I have purchased batteries to suit those recommended by the engine supplier however I need to prove that the batteries are large enough to cope with the starting currents of each engine.

Each engine needs to be able to crank for maximum of 10 seconds for 6 start attempts.

How do I calculate this?

I also need to prove the batteries can be recharged in less than 6 hours.

I calculated the charger size with the following formula:

ah of battery * 40% charger losses / charger current

Many Thanks,


marineuk asked
ripper edited ·

1 Answer

Lithium and starter constantly in parallel when on shore power

Hi, I've recently installed a lithium bank and use a cyrix li ct to connect them for solar and alternator chargin via the starter battery. This system works great when unplugged - cyrix kicks in when there is enough solar or alternator charge and disconnects when not. However, when I'm connected to shore power and charging the lithiums with the muliplus the cyrix (rightly so) remains engaged. Just wonder if there is any damage that can be caused to either starter or lithiums doing this? If so I will just put a simple switch in the wire from the charge disconnect circuit and turn off the cyrix when on shore power.

stocksy asked
Justin Cook - Bay Marine Supply USA answered ·

1 Answer

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