Turbo-charging Motorhome Electrics

[Duckato]

@wildebus this has been an interesting read.
I am also considering Lead Carbon batteries but was put off by the data sheet for the Leoch pure LC because it stated minimum charge temperature of 0c!

For a lead acid battery that restriction surprised me.
So I went off looking at other lead carbon variants to see if they were all the same.

To date I had not found another data sheet that actually stated the charge operating temperature range however the data sheet for the Ritar says -20c~50c which is a relief and they will do me nicely.

 

[SquirrellCook]

I would have thought all batteries had an optimum charge discharge temperature range.

 

[wildebus]

Got round to finishing off a bit more of the electrics today
In post #8 I mentioned about the additional AC Outlets the EasyPlus provides and I ran the cables in readiness to cable up? Time to put that plan into action!

Firstly chopped the cable that went from the Sargent (Middle MCB) to the Truma Ultraheat and joined it to the Multiplus MCB 0 outlet. This actually makes the middle Sargent MCB redundant. If I had fitted a normal Multiplus, I would have reworked the Sargent innards to keep that breaker in place but the EasyPlus Breaker Set is actually better quality (DP rather than SP) and it also meant that it would be easier to take the system back to standard at a later time if I ever wanted to.
I then chopped the cables that went from the Sargent (End MCB) to the Truma Ultrastore and Thetford Fridge. This MCB also drives the pair of 240V lights and an extra socket I had previously added, so this is still relevant and more specific, which could be handy in practice.

In the case of the Ultraheat, I just made a direct connection as it only goes to one place and there is an Truma Control switch for that.

For the other two, I want to be able to easily choose which device has any power available. The Ultrastores mains switch is right out the way under the cooker so awkward to get to. The Fridge socket is also behind drop-down door under the fridge and a bit of a pain to get to. The fridge itself has the energy selection control panel, but I want to be able to use auto-select without neccessarily using the 240V supply (so will switch to 12V automatically when moving as you are "strongly advised" against using Gas to power the fridge when moving) and would prefer to not get on hands and knees to unplug and plug in the fridge when I want to use/not use 240V.

Therefore, first step is to make some holes in the Electrics cupboard.

And then fitted a pair of AC Fused Spurs with Switches.

The Upper AC Switch is for the Boiler. The Lower AC Switch is for the Fridge. Both Spurs are fed by the outlet of the Auto-relay switching box (see the diagram below).

What will this setup allow?
Well, there will be power to the Fused Spurs whenever the EHU is live, so I can use Hookup power for the Water and Space Heaters simply by flicking on the two switches on the Spurs. When there is no EHU live, then Inverter power to the Spurs is controlled by the Relay on the Cerbo - and I can set the Relay up so the Spurs are only connected in my chosen conditions - typically a battery State of Charge of over 80% or whatever I fancy making it (the Relay sends a +ve signal to the SSR and when active, the SSR switches on and the SC power goes to the Auto Relay).

The Truma Ultrastor works on Gas and/or Electric. When on Electric, a 850V AC Element is switched on to heat the 10L tank to 70C. On Gas, you can select the temp required between 30C and 70C. If you combine the two, it speeds up the heating process (from 15C to 70C, Gas only takes 34Mins, Electric only takes 45Mins, Gas+Electric takes 25 mins) so using potentially spare battery capacity not only saves you gas but can get you a tank of water for your shower faster Or just run the heater on Electric for an extra 20 mins and use no gas.

The Thetford Fridge is either/or when it comes to Electric or Gas. It draws around 250W for around 75% of the time so not very economical when it comes to used electricity, but depending on what is coming from the solar it could be a handy use of spare and otherwise wasted harvesting.

Having the switches makes it very easy to chose where to direct the power, and having the relay cutting the power if the battery bank drops below the set value keeps the batteries well protected.

Couple of asides ...

• The bigger Multipluses (3000VA and larger) have a AC2 outlet which is Live AC-Only, but can actually be programmed to work through the inverter so work off-grid. The EasyPluses AC-Only outlet is strictly AC-Only as it is not part of the Multipluses logic but an electromechanical switch (this is my understanding anyway looking at the manual diagrams). So the Truma Ultraheat will only operate on Electric when on EHU and cannot be bypassed (this is fine as a space heater will pretty well kill a battery bank pretty quickly if allowed to run off-grid).
  
  
• The top device is a standard dual-USB outlet. Added there as handy place to provide power to devices such as the rechargable torch and MiFi.

Little bit more socket installation probably and that should be the key 'Turbocharging' done. There is of course the Solar Array to install but no great rush on that as don't expect to get any sensible harvesting (given time of year and the fact I am parked with a tall house to the south blocking any sunlight) for at least 2 months at the least.

 

[wildebus]

Tried out the new setup overnight
Unplugged the Fridge and plugged in a little mini-oil Rad set on low.
Disconnected the EHU around 8PM and just left the system to do its thing ....

You can see the Inverter switching itself on periodically as the heater kicks on.

You might have noticed that around 3:30AM, the inverter comes on for a shorter time and and then does not come on again?
Reason for this is quite simple ... The Cerbo relay that controls the SSR mentioned in the previous post was programmed to activate when the Battery State of Charge (SOC) dropped to 80%.

This relay coming on (Closing) disconnected* the SSR, thus removing power to the Mini Heater (on the Fridge socket for this test). So the AC demand disappeared and the Inverter turned itself off.
So operated exactly as planned, which is always a nice result to get



*Just a comment. A relay coming on DISCONNECTING something may seem a strange way to use it as relays usually turn things on, not off. The reason for how this is setup is because to automate this process, I am using the Victron OS programmable feature of sending a signal to have a generator turn itself on when the batteries go low in order to recharge the batteries. So the relay activates at a low SOC to do this rather than turning off a relay at a low SOC.
The relay is fitted with both an NO and an NC connection. NO - Normally Open- gets connected when the relay is Active; NC - Normally Connected - is, well, normally connected, but gets disconnected when the relay is Active. By using the NC connection, I have the SSR connected when the Cerbo Relay is OFF (Open in above chart), and the SSR is disconnected when the Cerbo Relay turns on (shown as 'Closed' in the chart).

So now in a position to make the most of the Battery Bank in readiness for when the Solar is fitted and active.
When on EHU, the Inverter doesn't tend to get used and this Fridge and Boiler circuit will always switch to EHU automatically (via the 230V AC Auto-Relay).
When off-grid, the Inverter feeds this Fridge/Boiler circuit when the SOC is above 80%. However, when the SOC drops to 80%, the circuit is disconnected from the Inverter and will not reconnect until the SOC rises above 94%. This is so the batteries are able to receive any Solar Harvesting to get back upto a good charge state.

(Note there are other AC circuits that can use the Inverter outlet regardless of SOC, such as the Microwave and general plug-in devices such as Laptop Chargers)

It is possible to overide the programmed state of the Cerbo Relay via the Control Panel to enable the relay (and thus turn off the Inverter Supply) but not turn the relay off if the SOC has told it to be on.

I need to work out a way to override this manually to force the Cerbo relay to turn off and have the SSR go on. Using the Manual option in the Control Panel is the best way as this can incorporate a timer, but if needs must, could use a physical switch.

 

[Markd]

Very impressive - you may get some flak about designing to use a generator though it's a great idea for a 'working' van.

 

[wildebus]

Very impressive - you may get some flak about designing to use a generator though it's a great idea for a 'working' van.

The generator part is not actually using a generator, but just taking advantage of the internal programming of the Victron GX device to control Generator auto stop and start and repurposing it to control an AC circuit
The same thing can be done with the BMV-712 Relay and in a much more obvious way, but I might have other uses for that relay in my Motorhome

 

[wildebus]

Right - worked out how to do an timed override

Need to use an extra bit of kit and rejig the 12V signal wire to the SSR a bit, but should work out well I think.
Revised setup in the picture below:

The NC output of the Cerbo used to go to the +ve of the SSR but now goes to the NC of a Countdown Delay Timer Relay (lets call this the CTR)
The COM of the Countdown Timer Relay now goes to the +ve of the SSR.

This means if the Countdown Timer is not running, the SSR will be either On or Off depending on the state of the Cerbo Relay - so just as described earlier.
But while the Countdown Timer IS running, the CTR will be enabled, and instead of NC and COM connected, NO and COM will be connected. This means COM will carry a +12V level and the SSR will switch on, so regardless of the Cerbo Relay status, Power will be available on the Fridge/Boiler circuit from the Inverter (assuming EHU not live. If EHU is live, all this is irrelevent! This is about off-grid operation only).

To activate the Countdown Timer, a momentary push-to-make switch makes a connection to two pins and starts the Countdown. If the Switch is pushed again whilst the Countdown is running, the timer is disconnected and the CTR is switched off (and the SSR is controlled by the Cerbo again).
The timer I will be using is this one - https://amzn.to/3hrtILx

There are quite a few around, but most have a very limited delay duration of just a few seconds, with the odd one maging 999 Seconds (16 Minutes) and I wanted a longer countdown. The one above is the only one I could find that can be set to a decent duration - upto 99 seconds or upto 99 Minutes. A 60 or 90 minute (1 or 1.5 Hr) override will work out fine I think
I could have gone for the Chinese stock rather than Prime stock and saved about half the price but too impatient to wait a month! This should arrive tomorrow
Last unanswered question .... How much power does this use? Well, when it is running, the overhead of the timer will be noise compared to the AC power being used, but when not running and in standby, it could add up! In the text on the Amazon listing it says "... normally the module will start to work when triggered, if you need module to work immediately after power on, connect 2 terminals of trigger".
Now exactly how to do what it says is unclear, but I think it means you can wire it up so it only uses power when it is doing the countdown so when not in use, zero current overhead

 

[st3v3]

! In the text on the Amazon listing it says "... normally the module will start to work when triggered, if you need module to work immediately after power on, connect 2 terminals of trigger".
Now exactly how to do what it says is unclear, but I think it means you can wire it up so it only uses power when it is doing the countdown so when not in use, zero current overhead

I imagine it's Chinglish for changing it from delay on to delay off.

Edit, maybe not. Who knows lol

 

[Nabsim]

Very impressive - you may get some flak about designing to use a generator though it's a great idea for a 'working' van.

Not wishing to start any flak but why? I have no choice but to use a generator to keep battery topped up most of the year. Victron themselves use the generator tag I think as a lot of boats use generators as do rev's.
Saying that the setups Dave does are usually out of my budget but nice to see them

 

[wildebus]

Not wishing to start any flak but why? I have no choice but to use a generator to keep battery topped up most of the year. Victron themselves use the generator tag I think as a lot of boats use generators as do rev's.
Saying that the setups Dave does are usually out of my budget but nice to see them

I don't have any issues with Generators either.

As an aside, The Easyplus (Multiplus) tells me when I am on Hookup ("Running on Grid") -

but the other day I had the Motorhome plugged into Clarence the Campervan instead of the house (trying some stuff out and didnt want to keep tripping the House RCD) and it told me I was "Running on Generator".
Not sure what difference in the supply (national Grid supply vs Multiplus 12/3000 supply) it detected to decide that?

 

[Nabsim]

when you use a generator do you plug it in the 240 hook up point Dave? Just wondering if it would see that as a generator or mains

 

[wildebus]

when you use a generator do you plug it in the 240 hook up point Dave? Just wondering if it would see that as a generator or mains

Yup - same inlet.
Victron do a "Quattro", which is basically like a Multiplus, but one extra feature is instead of just one, it has 2 hookup inlets - one for Grid and the other for Generator, so on that model it will know which is active (handy as you can limit the current on the Generator one to avoid overloading it). Handy - but the quattro is hundreds of quid more expensive
I'm going to switch the supply and see what happens and if it tells me different. Might even connect up the Genny!

 

[wildebus]

OK, got the countdown timer module today and tried it out on the bench ...

Looks decent enough and seems to work well (on a timed test, 1 minute on the timer is 1 minute in real life down to as close as I can tell). The current draw seems to be pretty low. When the timer is counting down and the relay is on (the little green LED on in the middle of the board), the device draws between 10mA and 20mA (the granularity of the display means it alternates between 00.01 and 00.02).
When the countdown timer is reset, there is no current draw shown by the PSU. Obviously there must be as the LED display is still lit, so I am guessing it must be under 0.005A (5mA). 0.005A on a 12V system works out to be just under 1.5Ah/Day.
When a camper/motorhome is in use, 1.5Ah a day is not a great deal, but can add up of course on a system that is parked up in storage, so this would be device you might well switch off. (As a comparision, the BMV-712 with no backlight consumes 1mA).


Now the comment "... normally the module will start to work when triggered, if you need module to work immediately after power on, connect 2 terminals of trigger" would point to a way to fix power use in standby and I think I have worked out what the above means

By connecting the 2 trigger pins together permanently and connecting a switch to supply power, as soon the switch is turned on, that provides power to the unit, the countdown starts and then when the time is reached, it goes into 'standby (still with power active) and to restart the countdown you turn the switch off and back on.
That is maybe the best way to wire it up to avoid any power use when not needed?

Just need to decide where to fit the switch

 

[xsilvergs]

Not sure what difference in the supply (national Grid supply vs Multiplus 12/3000 supply) it detected to decide that?

The difference between national grid and a 'non national grid' supply can be due to the way the earth is derived.

With my Phoenix I can change the earth connection internally from the default, which is mid supply, to the neutral line.

 

[wildebus]

The difference between national grid and a 'non national grid' supply can be due to the way the earth is derived.

With my Phoenix I can change the earth connection internally from the default, which is mid supply, to the neutral line.

That would make sense as the Multiplus default is to create an earth IIRC - and the supply when it said Generator was from an unplugged (from Mains) Multiplus.

 

[wildebus]

Ready to install a LEGO box in the Motorhome now

Or more precisely, the Countdown Timer enclosed in a Lego construction ...

I find using LEGO type bricks to make enclosures very handy This unit will generate a tiny amount of heat (1/4 Watt for an hour at a time) so the holes for the cables will be plenty of ventilation.

 

[wildebus]

Installed the Countdown Delay Timer (CDT) kit now

Made a extra alteration to the design which adds an extra level of flexibility to the operation

Within the dotted line in the schematic below is the Timer and Switch I just installed.

The operation works as follows:
Delay Activate Switch is now a 3-way On/Off/On switch.

• In position 0 (Off - as shown above), the Timer (CDT) is off, which means the CTD Relay connects NC (from Cerbo) to COM (to SSR). This means the CDT is bypassed and the SSR state is solely determined by the state of the Cerbo Relay.
• In position 1 (On, switch to the left), the CDT gets power and starts its downdown. This enables the CTD Relay, which connects NO (which has a +VE signal) to COM, thus turning on the SSR. As soon as the Countdown hits zero, the CTD Relay turns off, and again the SSR is controlled by the Cerbo only.
  I have set the countdown duration to 60 minutes - so as soon as the Switch is in position 1, the SSR will be force-enabled for 60 minutes and then revert to Cerbo Control. To get another 60 minutes of timer, the Switch needs to be put back to position 0 and then position 1 again.
  To cancel the timer early, simply put the switch back to position 0 and leave there.
• In position 2 (On, switch to the right), the CDT does not get any power and so no timer is active. However the CDT Relay COM is connected to +VE directly and as the COM is routed to the SSR, the SSR will be on all the time the switch is in position 2.

So in summary, with this switch I can (in P2) force the Fridge & Boiler circuits to work like the other circuits in the Motorhomer i.e. On EHU or Inverter regardless of any Battery level; or (in P1) work for just 60 minutes regardless of Battery level; or (in P0) be controlled fully dependant on Battery level.

In terms of switch location, I fitted it in a double-CBE mount behind the Drivers Seat.
So normal MO, the switch is in 0/Central - and I just flick it to 1/Up to have a 60 minute override. I don't really expect to use 2/Down but it's there if need be.

Decided to fit a double mount as I tend to sit on the bench on this side and thought it would be handy to have an AC socket here for the laptop charger (there is an AC socket as standard in the similar location behind the Passenger Seat.

As an aside ... that white stuff in the bottom right corner? Bit of a design faux pas by Autotrail. When the Drivers seat is swivelled, once it is turned past a certain position the release lever hits the side and scrapes the veneer. I think they should have really had some kind of mechanical stop to prevent it turning too far.

 

[st3v3]

Good stuff. I'd be tempted to put a shroud on that switch to stop it getting knocked on accidently though.

 

[wildebus]

Good stuff. I'd be tempted to put a shroud on that switch to stop it getting knocked on accidently though.

I think that is a good idea
Watch this space .....

 

[st3v3]

I think that is a good idea
Watch this space .....

3d print?