Too many choices (1 Viewer)

[GKD]

I’m looking to put approx 350 watt of panels on the roof to a hymer 704. Probably in 3 panels. The m/h has an ELB 29 with 2 x 95ah leisure batteries.
1 where is the best place to source panels. Is it true that the more cells they have, the better quality?
2. the max length of cable between panel and ELB is approx 7 m. The rest shorter depending where I put the panels. What size cables ?. Also is it better to join the cables on the roof in a busbar and then a single cable to the ELB (cable size?)or 3 cables to the ELB assuming they are arranged in series.
3. I want to charge leisure and vehicle battery. Do I use the Schaudt LMR1218 controller or is there a better option. The vehicle control panel doesn’t have ability to show Solar charge - should I use something else that is compatible with the chosen controller assuming it’s not a Schaudt.
4. I’m hoping to put the controller about 1m from the batteries. What size cable.

sorry from so many questions but there seems endless choice.

There seems to be many options for fixing to the roof. Metal brackets seem to be the better choice and many saying the mastic is good enough. The roof is protected with fibre glass - does that make a difference . I don’t want to screw down if can be avoided.

 

[MisterB]

The Solar Wire Size Calculator

solarwiresizecalculator.com

I have fitted 5 solar panels and 3 satellite dishes on different motorhomes just using sikaflex and the big plastic (?) corner brackets, no screws or bolts and never had an issue

Don't go too fancy on your panels, the important bit is what are the dimensions you have so you can get them into the space on your roof.

You can join the cables on the roof using 'Y' connectors and just bring down one set of cables through the roof gland. I would def consider installing some sort of breaker in an accessible location so you can isolate the panels.

Take your time and work through it. It's not difficult, biggest worry on your first installation is drilling through the roof for the cables! Try to bring them through a cupboard that goes up to the ceiling if possible.

 

[TrudeandDall]

I have recently installed one 280w panel from Craig Solar running via a Votronic MPPT 350 controler. The Votronic charges the leisure batteries (2 X 95ah) at up to 21amp, plus up to 1amp to the starter battery and it will handle what you propose. It is old school in terms of Bluetooth, but I fitted the optional analogue display, which gives me all of the solar and battery info that I need, without reaching for a phone... The Votronic is very effective at taking just what it needs from the panel. Roadpro are Votronic agents and you can get a funsters discount from them. Service is also excellent .
It's early days yet for me in solar production terms, but even in April conditions, my batteries have always been at full charge and well on top of the 90lt compressor fridge and load from our 600 PSW inverter for charging our two Ebikes.
I was lucky that my van was pre wired to just below the roof with 6mm2 cable. So rather than fitting a junction box where the solar cable enters, I used a DC isolation switch as a junction box and isolator in one! This switch is the same as your house uses on the mains incomer and is very neat in a cupboard. Also mine was less than £10 for a quality Brit made switch from eBay.

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[TrudeandDall]

Here's the isolation switch that I used.

 

[autorouter]

Is it true that the more cells they have, the better quality?

No, they are just aimed at different markets. Small panels with say 9 x 4 = 36 cells are used for small installations like road signs, night lighting etc, with 12V battery storage. Large panels with 10 x 6 = 60 cells or more are aimed at domestic solar arrays, with storage batteries of 24V or 48V. Motorhomes can use either type, depending on the power requirement, provided a suitable solar controller is used. More cells = higher voltage, larger area = more power.

 

[autorouter]

Also is it better to join the cables on the roof in a busbar and then a single cable to the ELB (cable size?)or 3 cables to the ELB assuming they are arranged in series.

The connectors used for solar panels, called MC4, are weatherproof and can be joined in various configurations on the roof. Series or parallel, your choice, you can get 2-to-1 or 3-to-1 MC4 adapters. So you only need one pair of wires through the roof to the controller.

To size the wires, work out about how many amps will flow, then, knowing the length, use a voltage drop calculator to calculate how thick it needs to be to keep the voltage drop below about 3%.

Voltage Drop Calculator | 12 Volt Planet

Use our Voltage Drop Calculator to select the correct Cable for your campervan, motorhome or boat wiring application. Auto and Marine Electrical Components from 12 Volt Planet - Cable Size Calculator

www.12voltplanet.co.uk

Parallel connection means more amps for the same power, so thicker wires. However most motorhome panels are connected in parallel to avoid shading problems. In series, a small patch of shade on one panel affects the whole lot, but in parallel it only affects the one panel.

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[Guigsy]

If you haven't done so already, install a shunt. I was surprised by how little power I'm actually using. The voltage drop I was seeing on my battery through the day was because it was tired, not because I using that many Amp hours.

 

[autorouter]

2. the max length of cable between panel and ELB is approx 7 m. The rest shorter depending where I put the panels. What size cables ?. Also is it better to join the cables on the roof in a busbar and then a single cable to the ELB (cable size?)or 3 cables to the ELB assuming they are arranged in series.

These EBLs were made in a time when 100W of solar was a massive installation. It's not really designed to take more than about 250W through the front panel connectors, and the LRM1218 is limited, to about 250W I think. For 350W of panel it would be better going directly to the battery, not through the EBL. Unfortunately you lose the state of charge (SOC) accounting which needs everything to go through the shunt inside the EBL, but the voltages should still be accurate. You can either just live with that, or fit a battery monitor on the battery.

There are several good solar controllers. MPPT types are better than PWM, and collect a bit more in less than perfect conditions. Victron, Votronic and Renogy are good brands. Votronic do a 'Duo' type that has a trickle charge output for a second battery like the starter battery.