Off-grid camper electric charging
Lessons learnt
Remember me getting my VW T4 ‘back to basics’ camper sorted for a 2,300+ mile road trip to the Outer Hebrides? That was an awesome road trip experience. The process of getting the camper prepped and ready for this journey allowed me to take a fresh look at different options for off-grid charging for a camper. Some of the lessons learnt I now want to apply to upgrading my split-screen camper next.
Solar solutions
I already had a good solar charging set-up sorted for my split screen camper. My design for the T4 off-grid charging system allowed this flexible solar-powered solution to also be used with both the split and the T4. This seemed a better way to go rather than buying two separate solar panels. I just needed to make up an additional connection cable for the panel to be used with the T4 as well.
I say ‘just’, it took a fair amount of research to discover the correct specialist fitment and cabling required! Turns out I needed some 2.5mm — 25A (2 core) Heavy Duty HO7-RNF Professional Grade heavy-duty rubber sheathed cable and an Amphenol Industrial Cable Mount Connector to complete the job. Of course, you probably already knew that, for me, every day is a school day! At least now whatever the vehicle I choose to travel in, I will now be able to use my solar panel with it. Who in this day and age doesn’t appreciate a bit of free electricity courtesy of the sun!
Solar power is a great way of keeping the leisure battery topped up when off-grid. The real secret is to make sure you have a decent leisure battery to use in the first place. Also, it needs to be looked after, maintained and fully charged when you arrive for a bit of off-grid camping. Kitting out the T4 proved to be an ideal opportunity to revisit some of the technology required to do this. It’s a fun challenge finding and utilising appropriate technology to work with a classic camper. Yes, I’m a bit nerdy like that!
Two of the best things I did with the T4 were to add a large capacity AGM (Absorbent glass mat) Leisure battery and link this with a CTEK D250SE 5-stage DC-DC (battery-to-battery) charger/MPPT solar charge controller. Having experienced some of the benefits this combo brought to the T4, I realised it was time to upgrade and apply some of these technologies to the split bus camper now.
Big and clever
First up with the leisure battery it’s important to get a decent Amp/hour (Ah) capacity! I decided to replace my previously struggling smaller capacity lead-acid leisure battery in the splitty. However, knowing how tight and cramped the space was for fitting the leisure battery in the rear corner of the bus engine bay, I decided to make a 3D box to check what size would actually fit! Having determined the maximum size, I then ordered a high-performance 100Ah AGM (Class A) leisure battery. This should keep me going with plenty of power for several days at a time!
Why an AGM Leisure battery?
- AGM technology is ideal for maximum endurance, more cycles, and faster charging
- The ideal choice for road trips with off-grid requirements (NCC Class A verified)
- Optimised for repeated charging and discharging
- Spill-proof internal construction for peace of mind
- Fully maintenance-free
I don’t use a lot of electrical devices when I go on a road trip. I prefer the simplicity of a more back-to-basics lifestyle on the road. However, what items I do take (like a compressor fridge, mobile devices, camera etc.), I want to reliably work when needed. I tend to not use electric hookups, preferring to rely purely on my leisure battery and a solar panel charging setup. This is why I need a reliable off-grid charging and power system.
Stay in charge
The next part of the off-grid charging conundrum is how to keep the leisure battery fully charged and maintained when out and about on a road trip. I had previously only ever heard about split charge relays or smart/intelligent Voltage Sensitive Relays (VSR). These allow the charging of a leisure battery from your vehicle’s starter battery/alternator. They are comparatively cheap and are widely used in campervans. They are a well-known and fairly well-understood technology. Plus they are relatively inexpensive.
The VSR relay connects when it senses the voltage reaches a defined voltage (say 13.7V or higher) and then disconnects when it senses the voltage drops to below a minimum voltage (say 12.8V or lower). They also maintain battery isolation when not charging, so the starter battery cannot be drained by the leisure battery use and vice-versa so you don’t end up draining your starter battery. All of this is good stuff.
However, doing some lockdown research into the subject, I discovered some interesting drawbacks to this system. I didn’t realise that a traditional split charge system using a VSR is that they will only achieve around an 80% charge state. This is not ideal if you want to arrive at your destination fully charged! This was a key aspect that I never previously knew (or understood). No wonder I had sometimes struggled off-grid on occasions in the split camper. Also probably the reason why I had gone through a couple of previous leisure batteries! To get the battery fully charged, I would have needed to plug it into a mains-powered battery charger periodically. In my circumstances, this would be an awkward thing to do.
Top tech
This is where Battery-to-battery chargers (also commonly known as DC-DC chargers) come in. Like a Voltage Sensitive Relay, they also allow you to charge an auxiliary/leisure battery from your alternator whilst driving. However, they offer several additional key benefits when compared with traditional split charge systems that utilise a VSR.
Benefits of using a Battery-To-Battery charger for auxiliary battery charging
- Batteries charge much faster when using a Battery-To-Battery charger when compared with direct alternator charging (as found in split charge systems using a Voltage Sensitive Relay (VSR), HD relays or diode isolators). This can typically be around 5x faster.
- A much deeper state of charge can be achieved because the Battery-To-Battery charger uses a multi-stage profile to maximise the depth of charge, something not possible in standard split-charge systems which will typically charge a battery to around 80% of its capacity.
- Charging will always take place when the engine is running, regardless of the alternator output voltage, because low voltages are boosted to meet the required charging profile.
- As in a split charge system, the starter and auxiliary batteries are electrically isolated when the engine is not running to ensure that one cannot discharge the other.
- The current reaching the auxiliary battery is determined by the charger rating (rather than by the maximum the alternator can produce), meaning that potentially damaging current in-rush is eliminated.
Normally they are used in more modern cars with an ECU-controlled ‘smart’ alternator (generally Euro 5/6 compliant engines onward). They are also recommended for older vehicles that want a better quality leisure battery charging system. Giving a much faster charge and higher capacity than a standard split charge system using a relay. A battery-to-battery charger is the best option for charging AGM, Gel or Lithium LiFeP04 type batteries to ensure they are charged at the correct voltage and faster up to a full capacity.
Smart charging
Having added a DC-DC charging system to the T4, it was a no-brainer for me. Time to upgrade the charging system of the splitty too! I guess the only real downside is that they are more expensive than buying a standard VSR. However, in my mind, this is easily outweighed by the longer-term advantages they offer. Having a reliable off-grid power source (leisure battery) is pretty essential to me.
Battery-to-battery chargers are fairly straightforward to install, however, in the back of the bus, with a big new AGM leisure battery to fit, this was going to be a tight squeeze! The T4 had the advantage of being a blank canvas charging system-wise. Here I opted for a 5-stage DC-DC (battery-to-battery) charger/MPPT solar charge controller combined in a single unit, the CTEK D250SE. As I already own a separate CTEK MXS 5 battery charger, I knew how good that is.
With the split camper, I already had a Victron MPPT 75/10 solar charge controller fitted. I just needed to add a DC-DC (battery-to-battery) charger element into the mix to replace the previous split charge relay setup. So in this instance for continuity, I opted to use a Victron Orion Tri Smart 12|12–18 DC/DC charger. Both Victron units have the added advantage of being ‘smart’ and have a Bluetooth app you can use to monitor and control the units. I know, there is pretty much an app for everything these days! It’s a shame that with the CTEK units this is an additional paid-for extra. It’s a surprisingly useful feature in my opinion.
Tight fit
Big shout out to the team at Resto Classics for more ongoing great service. It was always going to be a potential struggle to fit the bigger leisure battery in. The existing wiring and fuses associated with the VSR would also need to be moved and repositioned. There’s not much room in the rear corner of the bus engine bay, and the overhang of the oil bath air filter doesn’t exactly help! Glad I made a 3D mock-up of the leisure battery to check if it would fit before ordering it!
The positioning options for installing the Victron blue solar 75/10 MPPT charge controller and the new Victron Orion Tri Smart 12|12–18 DC/DC charger were pretty limited. In the end, the guys at Resto Classics came up with a very neat solution. They made a custom aluminium panel to mount the two Victron control panels on and then installed a separate 6-way fuse box to connect everything up to. Although it’s a confined space, they have made it so much neater now.
Off-grid reliability
With a new 100Ah, AGM leisure battery fitted and a new reliable means of ensuring it was kept fully charged and maintained, I’m now all sorted for some off-grid camping adventures. Both of the Victron controllers are able to be monitored and adjusted via Bluetooth on an app from your phone. A happy mix of current and classic technology!
Road trip ready
Combined with getting all this work sorted, I had booked the bus in with Resto Classics to have its annual check-over. Technically the bus no longer needs an MOT. However, keeping the bus safe and in tiptop mechanical condition is a priority for me. Resto Classics knows what to look for on an MOT, so I’d rather have everything (not just MOT areas) checked and given an overhaul if/where required.
So the bus had new rocker gaskets, adjusted valve clearances and reface adjusters, tightened fan belt, engine and gearbox oils, greased front axle and linkages, adjusted brakes etc. They also spotted that the gearshift bush needed replacing along with realigning and re-greasing the centre bush. Wow, now the gear changes are soooo much smoother. Changing gear is now like moving a hot knife through butter! It’s strange how I had obviously grown accustomed to how it had been previously! It was OK before, but now feels like a whole new gearbox was fitted!
A road trip beckons… might be time to stock up on a few road trip essentials in preparation. I’m sure there’s a VW show I’m going to soon…
