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.

driving through the sea via a cool causeway
driving through the sea via a cool causeway

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!

golden hour solar charging
golden hour solar charging

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!

A tranquil spot to see out the night on Scalpay
A tranquil spot to see out the night on Scalpay

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 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!

New 100Ah AGM LB6110 leisure battery fitted
New 100Ah AGM LB6110 leisure battery fitted

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
heading off-grid in style
heading off-grid in style

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.

Heavy duty split charge cable kit
Heavy-duty split charge cable kit

The VSR relay connects when it senses the voltage reaches a defined level (say 13.7V or higher) and then disconnects when it senses the voltage drops to below a minimum setting (say 12.8V or lower). They also maintain battery isolation when not charging. The starter battery cannot be drained by the leisure battery use and vice-versa. This is important so you don’t end up draining your starter battery. All of this is good stuff for off-grip usage.

However, doing some lockdown research into the subject, I discovered some interesting drawbacks to a VSR-based system. I didn’t realise that a traditional split charge system using a VSR will only achieve around an 80% of the leisure battery’s maximum charge state. This was a real eye-opener to me. You want to arrive at your destination with a fully charged leisure battery!

This was a key aspect that I never previously knew (or understood). No wonder I had sometimes on occasion, struggled off-grid s in the split camper. Also probably the reason why I had ended up going through a couple of previous leisure batteries in the process! 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 or 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.

Five big benefits of Battery-To-Battery leisure battery charging

  • Speed of charge; Typically this can be around 5x faster compared to using a Voltage Sensitive Relay.
  • Provides a deeper charge state; Using a multi-stage charging profile (with bulk, absorption and float stages), the battery can be fully charged. A VSR just delivers single-stage bulk charging. This achieves only around 80% of the battery’s charge capacity.
  • Active charging; When the engine is running, the charging profile can operate. It is not alternator output voltage-dependent. Low voltages get boosted as required.
  • Electrically isolated; When the engine is not running, the leisure battery cannot drain the starter battery (and vice-versa).
  • Overload protection; The current given to the leisure battery is determined by the charger rating, not the maximum the alternator can produce.

When you look at the benefits they offer, it seemed the obvious solution for my requirements. Having already 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.

the flexible solar panels topping the leisure battery

the flexible solar panels topping the leisure batteryDC-DC chargers are normally used in more modern cars with an ECU-controlled ‘smart’ alternator (generally Euro 5/6 compliant engines onward). However, they are also recommended for older vehicles that want a better quality leisure battery charging system. They give a much faster charge and higher capacity than a standard split charge system using a relay. A battery-to-battery charger is also the best option for charging AGM, Gel or Lithium LiFeP04 type leisure batteries.

Smart charging

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.

Victron Bluesolar Smart MPPT (Maximum Power Point Tracking) charge controller, the brains of the solar power system
Victron Bluesolar Smart MPPT (Maximum Power Point Tracking) charge controller, the brains of the solar power system

With the split camper, I had previously installed a Victron MPPT 75/10 solar charge controller. 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.

Victron Orion Tri Smart 12|12–18 DC/DC charger
Victron Orion Tri Smart 12|12–18 DC/DC charger

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!

Tight fit, but Leisure battery and DC-DC charger all in!
Tight fit, but Leisure battery and DC-DC charger all in!

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!

charging geeky – monitor and control settings on an app
charging geeky – monitor and control settings on an app

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.

my old HO17 666 windscreen sticker
my old HO17 666 windscreen sticker

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!

time to stock up on some road trip goodies…
time to stock up on some road trip goodies…

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…


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