Van Bitz Battery master (1 Viewer)

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Feb 14, 2021
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19 month year 18000 miles UK, Ireland, France, Spain, Germany, Italy. Campsites and off Grid.
A little question about how this operates. So as I understand, it delivers a trickle (1 map) to the starter battery when it detects that the Leisure is a certain voltage above the starter.

My question is, is it detecting the true voltage of the battery or, when the sun is shining strongly (as it is now) and the Leisure is receiving a 13.5 volt or more charge from the solar?, will the Battery master interpret this as a the Leisure actual battery state and possible also charge the Starter? Hence charge the Starter could receive charge even though it is above the actual state of the Leisure?
 

eddie

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Oct 4, 2007
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I designed it to measure the voltage at the point it's connected

That was when ever the leisure battery is receiving a charge, the engine battery will potentially benefit

If the connection point is weak IE down skinny wires with the associated problems with voltage drop, the engine battery will not benefit as quickly or efficiently

The split charge relay 'should' always be installed with a decent gauge wires so the recommended connection point for ease of installation/efficiently

But I'm retired and drinking wine in Spain
 
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OP
VXman
Feb 14, 2021
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I'm not sure about the skinny wires bit as it is connected through my EBL119 and directly to the starter only 6 inches away so not much wiring to speak of.
 
Apr 27, 2016
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The only thing the BatteryMaster, or anything else, can actually detect is the battery terminal voltage. You can see the 'true voltage' of a battery (ie the 'resting voltage') when disconnected from loads and chargers for several hours, but most of the time all you can do is measure the terminal voltage.

In some ways you could say the resting voltage is irrelevant most of the time, especially when being charged. But technically it's the voltage generated internally by the battery, from the chemical process that gives the amps current flow its energy. Its posh name is the electromotive force, or 'emf'.

The opposite process, where the amps current flow loses its energy (in a light, motor or heater) is called potential difference, or 'pd'. But usually emf and pd are both just called voltage.

If you want to force amps back into a battery, in the reverse direction, you need to apply a voltage equal to the battery emf, plus a bit more. That's why you need to apply 13.5 to 14.5V to a 12V battery to charge it.
 
Apr 27, 2016
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when the sun is shining strongly (as it is now) and the Leisure is receiving a 13.5 volt or more charge from the solar?, will the Battery master interpret this as a the Leisure actual battery state and possible also charge the Starter? Hence charge the Starter could receive charge even though it is above the actual state of the Leisure?
To answer the second part of the question, the answer is yes, the starter could be receiving a trickle charge from the BatteryMaster even if it is nearly full, when the leisure battery is quite low but is being actively charged by the solar or mains charger.

That's quite a likely scenario, because with no hookup, the leisure batteries might be quite empty in the morning, but the starter battery could be still nearly full from the drive to the site the day before. So when the sun comes up, the leisure batteries will be charging at the solar charger's full power, and the starter battery will be taking a tiny amount to keep it topped up.

But it's only a small trickle charge - only about one amp if it's very flat, and much less if it's nearly full. So nothing to worry about, really.

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Jan 22, 2013
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So my Victron solar charger is showing 13.7volts on the two load terminals this morning,
Can this feed be used to trickle charge the starter battery that’s at 12.6 volts or is there potentially a problem?
 
OP
OP
VXman
Feb 14, 2021
3,979
8,707
Milton Keynes, UK
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79,219
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Burstner Lyseo 727G
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19 month year 18000 miles UK, Ireland, France, Spain, Germany, Italy. Campsites and off Grid.
So my Victron solar charger is showing 13.7volts on the two load terminals this morning,
Can this feed be used to trickle charge the starter battery that’s at 12.6 volts or is there potentially a problem?

Good question. I will look forward to other responses. I've often wondered what the load terminals are for.
 
Apr 27, 2016
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So my Victron solar charger is showing 13.7volts on the two load terminals this morning,
Can this feed be used to trickle charge the starter battery that’s at 12.6 volts or is there potentially a problem?
That would work fine, I think. The load terminals usually don't provide much power, enough to run a light maybe, but the BatteryMaster doesn't draw much power so it should be fine. You can do this if you don't want to connect the BatteryMaster direct to the leisure battery terminals, but I can't see any advantage of using the load terminals.
 

Two on Tour

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The load terminals usually don't provide much power, enough to run a light maybe

From the Victron SmartSolar MPPT 75/10 to 100/20 manual,

3.8.1. Physical load output
The DC loads in the system can be connected to the load output terminals. The solar charger controls the load output and
disconnects the loads if the battery voltage drops too low, safeguarding the battery against too-deep discharges.
The disconnect voltage of the load output and the battery management algorithm can be configured via a jumper in the VE.Direct
port or via the VictronConnect app. For more information refer to the Load output settings [22] chapter.
The current rating of the load output is 15A or 20A (depending on the MPPT model) and is short-circuit proof.

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Apr 9, 2022
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From the Victron SmartSolar MPPT 75/10 to 100/20 manual,

3.8.1. Physical load output
The DC loads in the system can be connected to the load output terminals. The solar charger controls the load output and
disconnects the loads if the battery voltage drops too low, safeguarding the battery against too-deep discharges.
The disconnect voltage of the load output and the battery management algorithm can be configured via a jumper in the VE.Direct
port or via the VictronConnect app. For more information refer to the Load output settings [22] chapter.
The current rating of the load output is 15A or 20A (depending on the MPPT model) and is short-circuit proof.
It's a handy feature - and can be "programmed" in different ways - when I read the manual on how to use/set it up, I wondered if I needed a BM/Ablemail at all!
 

68c

Oct 22, 2019
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Never thought of using the Load Output to top up the starter battery. Sounds luke good idea, can anyone shed any more light on this?
 
Feb 24, 2013
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Am I missing something here, 10 years ago we had a single solar panel fitted, didn’t think it was overly special but it diverts some charge to vehicle battery, I think all the time then more when habitation battery is full

We don’t need (or I don’t appear to need) other devices to do this 🤔
 
Aug 1, 2021
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Never thought of using the Load Output to top up the starter battery. Sounds luke good idea, can anyone shed any more light on this?
Yes, using the load output from a Victron solar controller to charge the hab battery is interesting. Presumably, a diode would need to be incorporated so that current only flowed to the hab battery, and not from the hab battery back to the controller?
 

Two on Tour

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It's a handy feature - and can be "programmed" in different ways - when I read the manual on how to use/set it up, I wondered if I needed a BM/Ablemail at all!

Never thought of using the Load Output to top up the starter battery. Sounds luke good idea, can anyone shed any more light on this?

I'm not sure that using the Victron MPPT load terminals is a viable option to top up the starter battery as I can see no option to control the amps that would be delivered to the starter battery and as such, the starter battery would possibly suck the full 20 amps that my 100/20 Victron solar charge controllers can supply until both the starter and hab batteries have equalised their voltages, and you would of course have to install cable capable of taking the 20 amps to your starter battery.
autorouter, can you please pass comment on this.

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eddie

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Oct 4, 2007
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Never thought of using the Load Output to top up the starter battery. Sounds luke good idea, can anyone shed any more light on this?
Well the Battery Master doesn’t require sun to keep the engine battery topped up, short grey days in December, January and February often produce little solar yield, often when due to bad weather the van is used least.

The same as if the van is under cover storage, or normally parked in the shade of a building for example

In those periods the Van Bitz Battery Master will ‘share’ the quiescent parasitic drain on the engine battery, with the Leisure battery, ensuring you can start the motorhome when you need to

Of course if solar is present and you get a nice sunny day, the solar will replenish the leisure battery somewhat, to further extend the period you can leave the van.

Connecting the engine battery to a connector designed to run bits and bobs once the leisure battery if full, runs two risks, one, what happens in the Winter months when the Leisure battery never reaches the fully charged threshold, and more importantly how do you ensure the engine battery will not exceed the rated output of the solar regulator? Obviously different regulators have different values

Overall it’s not worth it, better if your too mean to give Jim sixty odd quid for a Battery Master, change the regulator to one with dual battery output, they are normally rubbish, but will do a little bit for both Engine and Leisure batteries

A Jack of all trade senario around thirty quid
 

Tombola

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I use the load terminals to heat our secondary hot water tank I installed in our van to make use of the solar that was being wasted when our leisure battery is full.
Prefect timed post David and Sally as I was going to ask this today......so, the pos and neg terminals coming out of the victron mppt to the batteries could also in fact be used to run a couple 12v LEDs to light the cabinet it's situated in...?
 
Apr 9, 2022
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Well the Battery Master doesn’t require sun to keep the engine battery topped up, short grey days in December, January and February often produce little solar yield, often when due to bad weather the van is used least.

The same as if the van is under cover storage, or normally parked in the shade of a building for example

In those periods the Van Bitz Battery Master will ‘share’ the quiescent parasitic drain on the engine battery, with the Leisure battery, ensuring you can start the motorhome when you need to

Of course if solar is present and you get a nice sunny day, the solar will replenish the leisure battery somewhat, to further extend the period you can leave the van.

Connecting the engine battery to a connector designed to run bits and bobs once the leisure battery if full, runs two risks, one, what happens in the Winter months when the Leisure battery never reaches the fully charged threshold, and more importantly how do you ensure the engine battery will not exceed the rated output of the solar regulator? Obviously different regulators have different values

Overall it’s not worth it, better if your too mean to give Jim sixty odd quid for a Battery Master, change the regulator to one with dual battery output, they are normally rubbish, but will do a little bit for both Engine and Leisure batteries

A Jack of all trade senario around thirty quid
It was all those concerns that I had, so didn't use the load output directly.....
 

eddie

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the cabinet where my MPPT gubbins are is dark, easier than running back to bus bars/fuses 6 feet away.
But you have leisure battery wires there, next to the load terminals and the light will work in the dark, not
just when the Leisure battery is fully charged (y):cool:
 

Two on Tour

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Prefect timed post David and Sally as I was going to ask this today......so, the pos and neg terminals coming out of the victron mppt to the batteries could also in fact be used to run a couple 12v LEDs to light the cabinet it's situated in...?

The Victron MPPT load terminals can be programmed to be "Always on" which is effectively a direct link to your hab battery regardless of solar input.
On the bigger Victron MPPT's you only get a output to fire a relay to use to switch on and off loads.
 
Last edited:

Tombola

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But you have leisure battery wires there, next to the load terminals and the light will work in the dark, not
just when the Leisure battery is fully charged (y):cool:
ahhh, i see, i did think about tapping onto the leisure battery wires a few inches down, but thought easier just sticking them in the same terminals on the MPPt, but you are saying the MPPT will disrupt the flow.

cheers
 

eddie

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ahhh, i see, i did think about tapping onto the leisure battery wires a few inches down, but thought easier just sticking them in the same terminals on the MPPt, but you are saying the MPPT will disrupt the flow.

cheers
Well technically if the wire gauge was poor, the MPPT could potentially see a slight voltage drop, which would improve your solar yield anyway as it would up the charging voltage

However, if your running a cupboard light how long would the light be on?

However, there are many ways to skin a cat, personally I prefer the simplest most efficacious way 👍🏻
 

Tombola

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Nov 21, 2020
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Well technically if the wire gauge was poor, the MPPT could potentially see a slight voltage drop, which would improve your solar yield anyway as it would up the charging voltage

However, if your running a cupboard light how long would the light be on?

However, there are many ways to skin a cat, personally I prefer the simplest most efficacious way 👍🏻
of course, and Ive learned a bit of something

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funflair

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Am I missing something here, 10 years ago we had a single solar panel fitted, didn’t think it was overly special but it diverts some charge to vehicle battery, I think all the time then more when habitation battery is full

We don’t need (or I don’t appear to need) other devices to do this 🤔
I would suggest NO you don't need anything extra as it must be working OK for you, you obviously have a solar regulator that has the second output for the starter (they all don't), if you didn't the Battery Master option would most likely be the easiest. When we had the Flair we had the Votronic regulators with the second output but these only work when there is some sun on the solar panels so shed storage (without hook up) was a problem, Battery Master and EFOY was the solution (y) With the Morelo I changed the solar regs that had a second output to Victron which didn't so again I reverted to Battery Master to to trickle charge the starter battery, again of course in the shed the second output from the original solar regs would not have worked anyway but the BM trickle charges from our healthy amount of Lithium in the garage.
 
Dec 19, 2020
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I've got the load on my Epever MPPT feeding a couple of USBs at the side of my dash. These run the Speedo display & SatNav and is switched on at the MT50 display
 
Apr 27, 2016
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In theory you could just connect the starter battery directly to the leisure battery, and the solar controller would keep them both charged. That's fine as long as the solar output is more than any loads on the batteries.

That has a number of obvious problems. When the starter motor is running it takes a massive current, maybe a few hundred amps. Starter batteries are designed to take that for a few seconds, but leisure batteries aren't, so you'd want it disconnected during engine starting. If the leisure battery goes flat, the starter battery is flat too, and you can't start the engine. The leisure battery might need a slightly different charge voltage, or a longer time in absorb mode. So just directly connecting the two batteries together is not a good idea. A bit of electronics is needed on the link between the batteries.

A simple diode would work to some extent, but a diode has a voltage drop of 0.5V to 0.8V depending on the technology. But it stops any back-flow from starter battery to leisure battery. Add something to restrict the maximum current to about 1 amp, and that is more or less what a BatteryMaster is.

There is similar electronics inside a dual output solar controller, so that there is no direct metallic pathway between the batteries through the controller.

I don't know exactly how the load terminals are connected to the leisure battery, but I suspect it's just a fuse and a relay, in other words a direct metallic connection. There's timers and dusk/dawn sensing etc, but I don't think there's any control electronics. So connecting the starter battery to the load output would bring back all those previously solved problems with the starter motor overload and flattening the starter battery.

However you could connect a battery maintainer like a BatteryMaster to the load output, but that would be no different to connecting it to the leisure battery. Unless you had some need to switch it on and off with a timer.
 
Apr 9, 2024
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Timberland Endeavour
Well the Battery Master doesn’t require sun to keep the engine battery topped up, short grey days in December, January and February often produce little solar yield, often when due to bad weather the van is used least.

The same as if the van is under cover storage, or normally parked in the shade of a building for example

In those periods the Van Bitz Battery Master will ‘share’ the quiescent parasitic drain on the engine battery, with the Leisure battery, ensuring you can start the motorhome when you need to

Of course if solar is present and you get a nice sunny day, the solar will replenish the leisure battery somewhat, to further extend the period you can leave the van.

Connecting the engine battery to a connector designed to run bits and bobs once the leisure battery if full, runs two risks, one, what happens in the Winter months when the Leisure battery never reaches the fully charged threshold, and more importantly how do you ensure the engine battery will not exceed the rated output of the solar regulator? Obviously different regulators have different values

Overall it’s not worth it, better if your too mean to give Jim sixty odd quid for a Battery Master, change the regulator to one with dual battery output, they are normally rubbish, but will do a little bit for both Engine and Leisure batteries

A Jack of all trade senario around thirty quid
Hi Eddie, sorry to disturb you, but could you have a look at my post Sargent B2B please and give me. some advice.
Thanks, Dave

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