12V Guru – How to Connect a Solar Blanket to Your BMPRO System – the Right Way

Thinking about installing a solar blanket? Our 12V Guru shares how to correctly connect a solar blanket to your BatteryPlus35-II-HA.

12V Guru – How to Connect a Solar Blanket to Your BMPRO System – the Right Way

Thinking about installing a solar blanket? Our 12V Guru shares how to correctly connect a solar blanket to your BatteryPlus35-II-HA.
Picture of BMPRO

Hi, I have just read the article in June’s Caravan World regarding extra solar panel connections. I have two 170-watt panels on the roof of my van, 28 amps connected to a BMPRO BatteryPlus35-II-HA allowing a total of 35 amps input. I have purchased an iTechWorld 100-watt solar blanket, therefore an additional 8.3 amps.

I have an Anderson plug connecting to the additional solar connection terminals on the BMPRO. I have the solar blanket connected directly without using the MPPT regulator, thinking that the extra solar connectors on the BatteryPlus35-II-HA does the same thing. Is this the case? If not, how do I connect the extra solar?

Cheers,

Mal

Forster NSW

12V Guru Says..

Thanks for your question Mal, as this highlights a common scenario faced by many RV owners looking to boost their off-grid power capacity: how to correctly connect a portable solar blanket to an existing BMPRO BatteryPlus35-II-HA system.

Effectively there are two options – the first is as you rightly point out. Utilise the two fixed 170-watt solar panels on the roof of the van, producing a combined 28 amps on a good day. As your total solar input is less than 350 watts, you can then wire an Anderson connector to the unused positive and negative solar connections for a solar blanket, which can add around 8.3 amps again, under ideal sunlight conditions.

If you install more solar panels on the roof of your van to go over the 350 watts, you would need to wire it differently. This is the second option, where you would parallel up the solar positive and negative to spread the load, but this is not required for your scenario.

The BMPRO BatteryPlus35-II-HA includes a built-in MPPT solar regulator capable of accepting a total solar input of up to 35 amps, so adding a solar blanket that contributes 8.3 amps is perfectly within the system’s capacity.

Solar panels to charge batteries

A very important warning: the solar panel negative output (0V) is not a common ground and cannot be grounded if connected to the BatteryPlus35-II. Grounding the negative output can result in damage to the BatteryPlus35-II and batteries. Both positive and negative must be wiring directly from the Anderson connector to the BatteryPlus35-II without grounding on the negative.

Another key to successful integration is connecting the blanket directly to the BMPRO’s unregulated solar input, not directly to a battery or with a separate external solar regulator. This is because the BatteryPlus35 already has a high-quality MPPT regulator onboard. Feeding it pre-regulated solar power can confuse the system, reduce efficiency, and potentially limit charging performance.

There’s no need for a manual selector or switching between the two — as long as both are unregulated inputs, the BMPRO will take care of the rest.

Using an Anderson-style connector is a great choice. These are reliable, robust, and well-suited for caravan environments where vibration, dust, and weather are common.

Get your caravan electrical system ready for the trip

When wiring the system, ensure:

  • Correct cable sizing: Use at least 6mm² twin-core automotive cable (or larger, depending on run length, most setups are 8 B&S) to minimise voltage drop and protection.
  • Quality terminations: Avoid flimsy or temporary connections. All joins should be crimped and, ideally, heat-shrunk or sealed against corrosion.
  • Secure mounting: A loose connection increases electrical resistance, which not only reduces charging efficiency but can generate heat and lead to longer-term issues.

While solar blankets typically aren’t as efficient per watt as fixed rooftop panels, they do have a major advantage: portability.

With a solar blanket, you can position it wherever the sun is shining best. This is especially useful in shaded campsites or during early morning and late afternoon when the angle of the sun is less optimal for roof panels. You can even move the blanket throughout the day to track the sun and maximise exposure, something roof panels simply can’t do.

Additionally, when parked under trees or awnings, a solar blanket allows you to make use of that clear patch of sunlight a few metres away, keeping your battery topped up while enjoying a cooler campsite.

Your approach is spot-on. Connect the solar blanket via an Anderson plug directly to the BMPRO’s additional solar input terminals, without using a separate MPPT controller. It’s a straightforward upgrade that offers flexibility, redundancy, and peace of mind when travelling off-grid.

Safe travels and sunny skies Mal.

Cheers,

12V Guru

2 thoughts on “12V Guru – How to Connect a Solar Blanket to Your BMPRO System – the Right Way”

  1. Jason Smith

    Hi team,
    I have a Jayco Lark 2022 with a BM PRO set up.
    100AH lithium battery.
    The fridge we have is a manual 3way set up.
    I hear mixed feedback about if this set up will maintain the fridge temp utilising the battery when off grid.
    Have a solar set up wired to BM PRO to maintain battery level.
    Hope you can help

    Reply

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