Solar panel calculations

[SimonM]

I now have my new Hymer parked outside albeit without any solar panels fitted as the dealer wanted far too much when asked. They also indicated that ‘only’ 115w panels will fit. (bs)

After a question on the owners club it is feasible that a lot more can fit, although mine does have a large number of holes already in the roof making it a tad crowded. I realise it is possible to go across, eg a vent, higher but I don’t want to exceed 3.00m.

As memsahib has put a prohibition on me climbing ladders these days I’ve had to resort to a head out of a couple of skylights to give me approximate dimensions. These seem to indicate the following size of panels is possible.

1 off 700 x 1700
1 off 700 x 1300
1 off 700 x 1200 ( I was very cramped and it maybe feasible to squeeze 1250)

I‘ve looked online at Victron panels and have deduced the following sizes in Mono (is this what we would generally fit?)

1 x 668 x 1485 = 175w. @19.4v
1 x 668 x 1250 = 140w. @ 19.4v
1 x 668 x 1015 = 115w @ 19.0v A proper measurement and maybe I can squeeze a 140w

this would give me a total of 430w (or possible 455w) I would be more than happy with just 315w - but let’s see what can be done. I’m sure there’s also room for a 50w and another 115w, but let’s not go overboard for now.

now, what allowance is necessary for the additional width/length of mounting brackets?

I’ve attempted to guesstimate the size of MPPT controller required using the Victron site, and hope I’ve put the correct numbers in the calculator. The 430w suggests a 100-30 unit and 455w a 100-50. would the odd voltage of 19.0 indicated for the 115w be an issue? Should I just go for the 100-50 anyway?

Finally, I have no intention of doing any of this myself and will entrust it to professionals, but it’s very close to Christmas break and I’d like to get an idea of what is possible before troubling anyone.

here’s an aerial view of the roof, with the @%€£ radio aerial taking up some valuable roof space. I’ve decided we will not be fitting a satellite dish this time.

 

[wildebus]

I now have my new Hymer parked outside albeit without any solar panels fitted as the dealer wanted far too much when asked. They also indicated that ‘only’ 115w panels will fit. (bs)

After a question on the owners club it is feasible that a lot more can fit, although mine does have a large number of holes already in the roof making it a tad crowded. I realise it is possible to go across, eg a vent, higher but I don’t want to exceed 3.00m.

As memsahib has put a prohibition on me climbing ladders these days I’ve had to resort to a head out of a couple of skylights to give me approximate dimensions. These seem to indicate the following size of panels is possible.

1 off 700 x 1700
1 off 700 x 1300
1 off 700 x 1200 ( I was very cramped and it maybe feasible to squeeze 1250)

I‘ve looked online at Victron panels and have deduced the following sizes in Mono (is this what we would generally fit?)

1 x 668 x 1485 = 175w. @19.4v
1 x 668 x 1250 = 140w. @ 19.4v
1 x 668 x 1015 = 115w @ 19.0v A proper measurement and maybe I can squeeze a 140w

Redo your numbers, multiplying the current for the 175W and the 140W panels by 19.0V rather than 19.4V for the max wattage when all 3 panels are joined in parallel.

this would give me a total of 430w (or possible 455w) I would be more than happy with just 315w - but let’s see what can be done. I’m sure there’s also room for a 50w and another 115w, but let’s not go overboard for now.

I can't find the layout diagram I did, but I did a setup in 2021 for someone who bought a brand-new Hymer A-class, 3.5t shortish one, so pretty compact one. Managed to get 600W of Panels squeezed it
In order to save weight and not reduce the payload too much (also swapped over the two batteries for Lithiums), went for 6 x 100W Sunpower semi-flexible panels dotted about the roof. It was a tight fit that included sliding the panel edges under the vents for example, but more is possible than you might think
They might have been these one but can't be sure. I didn't supply them, just found them and pointed the customer where he could buy them from (was Bimble Solar I think?)

now, what allowance is necessary for the additional width/length of mounting brackets?

I’ve attempted to guesstimate the size of MPPT controller required using the Victron site, and hope I’ve put the correct numbers in the calculator. The 430w suggests a 100-30 unit and 455w a 100-50. would the odd voltage of 19.0 indicated for the 115w be an issue? Should I just go for the 100-50 anyway?

What batteries have you got? I doubt if the Victron Calculator tells you this, but the actual maximum wattage of a Controller is a bit lower with Lithium Batteries than it is with Lead Acid (for example, the 100/30 used with Lithium will not give you more than about 426W rather than the quoted 440W).

Right now Victron are having a massive push on Solar Controllers. I would go for the MPPT 100/50 if I were you rather than the 100/30 given the current pricing to give you that extra flexibility.

Finally, I have no intention of doing any of this myself and will entrust it to professionals, but it’s very close to Christmas break and I’d like to get an idea of what is possible before troubling anyone.

here’s an aerial view of the roof, with the @%€£ radio aerial taking up some valuable roof space. I’ve decided we will not be fitting a satellite dish this time. View attachment 126170

 

[trevskoda]

Biggest this lot do, or you could divide solar in two and fit 2 smaller units.

 

[wildebus]

Biggest this lot do, or you could divide solar in two and fit 2 smaller units.View attachment 126171

the current price of the Victrons, that Votronic is too expensive (as well as not being as good - double whammy!)

 

[SimonM]

I had a Votronic in the Burstner and it was extremely useful as it was able to charge the starter battery at the same time as the 4 leisure batteries.

I am undecided whether to have one panel and separate mppt to charge the starter battery only.

the leisure battery system has 2x95ah AGM batteries and a 150ah Lithium all tied together somehow, one person I spoke to a while ago called it a Frankenstein system and isn’t impressed with it.

 

[wildebus]

I had a Votronic in the Burstner and it was extremely useful as it was able to charge the starter battery at the same time as the 4 leisure batteries.

Won't charge the starter battery when on EHU - but I guess if you have an EBL PDU, you get a bit of an SB charge from that.

I am undecided whether to have one panel and separate mppt to charge the starter battery only.

inefficient use of the limited roof space IMO.

the leisure battery system has 2x95ah AGM batteries and a 150ah Lithium all tied together somehow, one person I spoke to a while ago called it a Frankenstein system and isn’t impressed with it.

That is the Hymer Hybrid system? expensive but is pretty good (nearly as good as my Hybrid system ).

 

[SimonM]

We almost never go to sites and use EHU, and so I will be doing whatever I can for self sufficiency off grid. I’ll bear in mind the ‘inefficient use’ remark as it’s quite valid really.

So what will be necessary to ensure the starter battery is getting juice when we are simply using solar?

 

[wildebus]

We almost never go to sites and use EHU, and so I will be doing whatever I can for self sufficiency off grid. I’ll bear in mind the ‘inefficient use’ remark as it’s quite valid really.

So what will be necessary to ensure the starter battery is getting juice when we are simply using solar?

2 real options ....
1) solar controller with dual outputs. Only valid option is Votronic. there are other 'duo' type controllers but they are PWM and low-power and the SB outout is very low
2) SB trickle charger. few genuinely work as they are meant to at the voltages Lithium works with. The only lithium-compatible options I know of is the AMT12-2 from Ablemail in the UK or the Amp-L-Start in the US (totally different products even though there is some packaging similarity)

The DC-DC trickle chargers are handier than the 'Duo' Solar controllers for many as they work with both Solar OR EHU.
I prefer them to the 'Duos' regardless myself as I don't think the Votronics are as good as the Victrons, but Victron don't do a 'Duo' type device.

Here is a good explanation of the American Amp-L-Start which is applicable to any DC-DC Trickle Charger in terms of operation. (It is worth watching to get an idea inprinciple of how these type of devices are installed actually)

A difference between the Amp-L-Start and the AMT12-2 is the Ablemail can be configured to work with Lithium; with Lead; and you can chose if you want it active with LB charging only, or even if no LB charging active (flexibility is a key feature of the AMT-12 - there are 8 different selectable programs, plus an infinite choice via the optional Bluetooth connection, plus a switched override)

 

[trevskoda]

the current price of the Victrons, that Votronic is too expensive (as well as not being as good - double whammy!)

Mine works well, price of course maters.

 

[trevskoda]

2 real options ....
1) solar controller with dual outputs. Only valid option is Votronic. there are other 'duo' type controllers but they are PWM and low-power and the SB outout is very low
2) SB trickle charger. few genuinely work as they are meant to at the voltages Lithium works with. The only lithium-compatible options I know of is the AMT12-2 from Ablemail in the UK or the Amp-L-Start in the US (totally different products even though there is some packaging similarity)

The DC-DC trickle chargers are handier than the 'Duo' Solar controllers for many as they work with both Solar OR EHU.
I prefer them to the 'Duos' regardless myself as I don't think the Votronics are as good as the Victrons, but Victron don't do a 'Duo' type device.

Here is a good explanation of the American Amp-L-Start which is applicable to any DC-DC Trickle Charger in terms of operation. (It is worth watching to get an idea inprinciple of how these type of devices are installed actually)

A difference between the Amp-L-Start and the AMT12-2 is the Ablemail can be configured to work with Lithium; with Lead; and you can chose if you want it active with LB charging only, or even if no LB charging active (flexibility is a key feature of the AMT-12 - there are 8 different selectable programs, plus an infinite choice via the optional Bluetooth connection, plus a switched override)

You could also use one small solar and a regulator to the s battery, 30/50w would do, then use what w bus says and connect the other panels to les batts.

 

[Trotter]

Lee had a similar problem fitting panels to a cluttered roof. Might be worth dropping him a PM, if he doesn't contribute.

 

[alwaysared]

The 700mm part is the toughest call but panel wise here's a couple of options for you, these Victron 140 watt panels x 3 = 420 watts @ £102.00 each = £306.00 or these 120 watt panels x 3 = 360 watts @ £60.00 each = £180.00 this assuming you want rigid panels, there are flexible options but the cost of the best ones is eye watering.

Regards,
Del

 

[wildebus]

The 700mm part is the toughest call but panel wise here's a couple of options for you, these Victron 140 watt panels x 3 = 420 watts @ £102.00 each = £306.00 or these 120 watt panels x 3 = 360 watts @ £60.00 each = £180.00 this assuming you want rigid panels, there are flexible options but the cost of the best ones is eye watering.

Regards,
Del

Both the Victron Panels and Victron Solar Controllers have plummetted in price in the last couple of weeks and have become amazing value for money. (apparently they are on a bit of a price war with Renogy?). They are very good panels.

 

[SimonM]

Both the Victron Panels and Victron Solar Controllers have plummetted in price in the last couple of weeks and have become amazing value for money. (apparently they are on a bit of a price war with Renogy?). They are very good panels.

Will those price war savings be reflected in the ‘fitted’ price when I get a chance to go looking at fitment I wonder?

 

[wildebus]

Will those price war savings be reflected in the ‘fitted’ price when I get a chance to go looking at fitment I wonder?

well, it is Victron who are reducing the prices to the distributors, so you should see some benefit. I don't know how long this price cut will be (I bought the last ones just too early )

 

[1 Cup]

Right now Victron are having a massive push on Solar Controllers

Ive
seen them tumble but have they lost / removed Bluetooth still looking for 1 for 4x 260wat panels .

(Eos Solar) 70amp 150/70-TR BlueSolar by Victron MPPT | eBay

BlueSolar range, which uses the latest ultrafast MPPT technology to maximise energy harvest whilst maintaining optimal battery health. 150/70-TR BlueSolar by Victron MPPT 70amp. Ultrafast MPPT Technology.

www.ebay.co.uk

(Xmas Treat ) 60amp 150/60-Tr SmartSolar by Victron with Bluetooth | eBay

Victron SmartSolar – 60 amp MPPT 150/60-Tr Bluetooth. Solar range which uses the latest ultrafast MPPT technology to maximize energy harvest whilst maintaining optimal battery health. They also have great communication options for remote system monitoring.150/60 TR Smartsolar.

www.ebay.co.uk

 

[wildebus]

I don't know what you mean by they have 'lost Bluetooth'? If you get the model with bluetooth, you get Bluetooth. They are discounting both heavily right now.

For clarity to anyone not familiar with the naming of ....
"Bluesolar" does NOT have Bluetooth
"Smartsolar" HAS Bluetooth

In Victron world, "Smart" means Bluetooth connectivity, "Blue" is a reference to Victrons colour, so when someone says "I've gone blue", they are saying they have bought Victron.

But like all rules, there are always exceptions.... the IP22 Charger can be bought as a "BluePower" model (no Bluetooth), or a "BlueSmart" version (with Bluetooth).

 

[1 Cup]

"Bluesolar" does NOT have Bluetooth

150/70 blue Will the cerbo or invertor do the setting with the leads I just brought ?.
Or for 1040 watts will the 150/60 smart do the job as that one has Bluetooth and I can set and save a storage setting file
TIA

 

[DTF]

Victron sell a Bluetooth dongle to give their “Bluesolar” units this access. It would add around £35 to the overall cost.

 

[Chrisinchip]

A cautionary note:

There was mention early on about dual output solar controllers. For completeness, you may find such an MPPT controller by Solar Technology International under PV Logic branding. (PV Logic Controllers). It has a serious design issue whereby the Battery 1 and Battery 2 cannot share the same earth (negative circuit). Fuses blow if this is ignored either when the controller switches its focus from one battery to the other, or when the engine stops/starts. The manufacturer's answer is to recommend use of only one battery output with a form of split charge relay system. Nuts. (Can you tell the first hand experience - my van came fitted with this make, which otherwise does a good job)

Also, there is the problem of supporting different battery profiles. I searched for a manufacturer that could handle PROPERLY a lead acid variant vehicle battery and a Lithium leisure battery and in the end relegated it to the too-difficult pile. No success even for handling different Lead Acid profiles across the two outputs.

My solution now for keeping the Vehicle battery happy when the van isn't used so much is either to periodically plug it in and switch the EHU to charge the Vehicle/Starter battery OR, because I can if the cupboard isn't too rammed with the boss' clothes, swap over the fuses so the controller charges the SB instead of the LB for a couple of weeks after switching the controller to the correct charging profile.