I have been upgrading the 12volt charging system in our VistaRV Crossover. I tend to get paranoid about how much power I actually have in the batteries and since I installed the Victron Smart Battery Meter I now know exactly what there is in them (State of Charge or SOC) and how many Amps are going in or out.

The next thing to do was to see if I could optimise the energy going in. I have an 80Watt solar panel permanently attached to the Crossover and a 120Watt folding solar panel which I use to chase the sun. There is also an Anderson connection via 6B&S cabling to the tug. The Crossover came with a 10Amp Projecta solar controller and a Projecta 10Amp 240Volt charger. So how to optimise these energy sources?

I replaced the 10Amp Projecta 240Volt charger with a Projecta 25Amp one. I felt the 10Amp charger was adequate for one battery, but too slow charging the 2x 100Ah batteries I had in the Crossover. The new one is much faster, plus it has a remote LCD display with controls. Because the main unit is inside a cupboard, I mounted the remote on the electronics panel just inside the door of the camper so I could see what was happening and change things if I want to. I went with the Projecta because it allows me to manually select the battery type and to play with the settings if I need/want to, unlike many other brands. The remote unit was also attractive as it lets me know what is going on and what phase the charging is in without having to open the cupboard.

Next I had to work out how to run the solar panels. After a lot of confusing research I bought an MPPT solar controller to look after the 120Watt folder. The controller it came with, as usual, was a cheapie attached to the solar panel… The one I bought is a Tracer 10Amp MPPT controller with a remote LCD screen so I could see what was going on. A few different people had recommended this unit. I mounted the controller right next to the batteries in the Crossover, thus minimising the voltage drop. The remote readout has a two metre cable attached so I can run this out to where I can keep an eye on it. I have attached a couple of magnets to the back of the remote so I can easily place it on the metal external panels of the Crossover where I can see it.

I removed the cheap, too light cabling the panel came with and replaced it with a 10 metre 6B&S one with Anderson plugs on both ends and attached an Anderson plug to the solar panel outputs and the controller’s inputs. That has minimised the voltage drop in the cabling. I also bought a 10 metre stainless steel cable so I can lock the solar panel to the camper when I am not around.

Next I decided to install a DC to DC charger in the Crossover to try to overcome the inevitable voltage drop caused by the roughly 10 metres of cable between the alternator in the front of the tug and the batteries in the rear of the Crossover. After my usual research process I decided upon a Ctek D250S Dual as this has an MPPT solar controller built in and so can look after the built in 80Watt solar panel as well. I removed the Projecta 10Amp solar controller which came as standard and wired the solar panel to the Ctek D250S Dual. I mounted the charger right next to the batteries, once again to reduce any voltage drop to the absolute minimum.

The D250S Dual is a multi-stage 20Amp battery charger. The 20Amp limitation loomed as the choke point in the system when charging from the tug. Hopefully the Anderson cable will be capable of delivering more than 20Amps when the batteries are at a low State of Charge, under 80%. How to solve this problem…

I had read about the Ctek SmartPass, but I could not get any really useful information as to exactly what it does. Most information sources simply say it is a really good thing, but give no pertinent details as to why! Finally I found someone at Baintech, the importers, who could give me the information I needed. There were also a few others there who, it seems, could not! I received by email, a PowerPoint file which explained what the SmartPass actually could do. After viewing the PowerPoint, I decided to order one.

The SmartPass is connected directly to the D250S Dual via two supplied copper bus bars, one to the alternator input and one to the charging output. The charging output to the batteries is then connected directly to the SmartPass as is the alternator input. The SmartPass is a very useful bit of equipment, it seems. So, what can it do? Here are some of its tricks:

1. If the batteries can accept more than the 20Amps of charging current available from the D250S Dual, the SmartPass will allow up to an extra 80Amps of current to flow to the batteries directly though the SmartPass itself. This means up to 100Amps can go into your battery bank, if that much is available and can be accepted.

2. You can connect the non-critical outputs from the batteries (up to 10Amps load) directly to a terminal on the SmartPass instead of to the camper batteries. The SmartPass will supply those loads directly from the alternator when there is current available from that source, and then revert to the batteries when it is not, i.e. if you disconnect the Anderson plug or turn off the motor. You can use up to a total of 110Amps from the alternator to charge the batteries and run the non-critical loads.

This means, for example, when the batteries are being charged by the SmartPass or the D250S Dual, the fridge load of around 4.5Amps (and any other load, up to a total of 10Amps) can be supplied by the alternator, not the charging circuits, so the full 20Amps from the D250S Dual can go to the batteries instead of roughly a quarter of the D250S Dual’s output being drained by the fridge when it is running. The batteries will charge faster because they get the full 20Amps all the time. Very smart! Also, the SmartPass will cut power to the non-critical loads if the SOC of the batteries gets too low (11.6Volts), thus saving the batteries from undue stress.

3. Both the D250S Dual and the SmartPass have thermal sensors which allow the units to reduce the charging rate if the batteries become too hot, thus stopping overcharging.

4. The SmartPass can also pulse charge your starter battery in the tug if the Anderson plug is connected and the camper batteries are fully charged and current is available from either a solar panel or an AC charger. Cute!

My next job will be to sort out and tidy up the battery compartment. I need to move the shunt to the side, out of the way. I could have used a Redarc BMS1215 which is a combination of AC, DC-DC and solar charger all in one. I decided not to as, if it should fail, you can’t charge your batteries at all as all your chargers are in one basket, so to speak. It is also very expensive at $1600 RRP. With my system I have three physically separate charging devices. Should one fail, I have still got two left and I only need to replace a $300 or $400 device, not a $1600 one.

I then decided to install a D250S Dual in the back of the tug to look after the 100Ah Gel auxiliary battery there. As the two D250S Duals also work as battery isolators, I then removed the battery isolator under the bonnet. I can now plug the folding solar panel into the D250S Dual if I need too as well. Hmm, maybe I should install a SmartPass in the back of the tug, too, then…

Will someone please tell me to stop!
 

 

thanks to David Jones for this article