A question for Bimble (now they're on here)

[Psycloud]

After 2 years debating and watching panels come and go on the Bimble website I'm wondering again which it the best option as I want to lay panels flat rather than go for tilting brackets...

 

Option 1 - 2 x 235w Grade B panels as per the kit (http://www.bimblesolar.com/offgrid/12v/12v-470w-MPPT-schuco)

Option 2 - 2 x 170w as per http://www.bimblesolar.com/solar/individual/solar-fronteir-170w-cis

 

The 170w panels are 1257mm long and only 35mm thick as opposed to the 235w ones which are 1650mm long and 46mm thick so the 170w panels are considerably smaller.

 

My question is, given the 170w panels are far better in low light (and we seem to have more low light in this country that decent sunshine), is there going to be much difference in the overall output during the autumn/spring months?

 

The plan will be to have 4 x Trojan T105's (totalling 450 ah @ 12v).

 

Decisions decisions.

[Phil Ambrose]

Are Bimble really members?

Phil

[Beaker]

Are Bimble really members?

Phil

 

They posted in this thread:

 

http://www.canalworld.net/forums/index.php?showtopic=77202&hl=

[Alan de Enfield]

According to the Bimble-Blurb the low light panels are roughly 10% more efficient so you could say that a 170 watt = a 187 watt 'conventional' panel.

 

The biggest difference will be in the controller you use :

 

An MPPT will give you around 20%-30% more than a PWM controller. (and an MPPT is compulsory on a 170 LL panel due to the voltage.

 

If you use an MPPT on a 170w LL it will be a rough comparison with a 220 watt conventional panel with a PWM controller.

 

At least - that's how it appears to work.

 

ETA :

The 235 watt panels are bigger, but are considerably cheaper than the 170 watt panels, and, can run using a cheaper PWM controller. It comes down to a combination of how much electrickery you want, how much space you have, and how much you are prepared to pay.

Edited August 16, 2015 by Alan de Enfield

[Psycloud]

Thanks Alan. I think the 170w panels are about £10 more each which is acceptable. The larger ones will fit mushroom to mushroom but I think the smaller ones will be far more aesthetically pleasing and sit 10mm lower. We will be using them mostly for the odd week away here and there as we are marina based 95% of the time for now. In 3 years we plan to take a year out on the cut so they will be used in anger then but we do have a 2300w generator for when we're in the darkest depths of the UK

Have I got this right - roughly speaking, the 170w panels at 12v thought MPPT would be 87/12*1.95 = maximum amps (less any loss thought cables and conversion)? I'm trying to get a theoretical amps comparison and 12v for the 2 different panels.

 

Edit: The 2 main power users are the A++ rated 240v fridge and the Eberspacher.

Thanks

David

Edited August 16, 2015 by Psycloud

[Alan de Enfield]

My (somewhat limited) experience of our several year old panels, mounted flat, was that we had a 'real maximum' output of about 5 amps per 100 watts.

Difficult to estimate as the slightest cloud, tree, cleanliness of the panels,& angle of the sun made a huge difference.

The 5 amps per 100w was based on cloudless sky around midday, and clean panels.

 

We had 2 x 80w, which generally gave an average of 4-5 amps, maximum I ever saw was 7.9 amps but that was only for a few seconds.

 

I would rather estimate on the low side, rather than be disappointed when I didn't get 8 amps per 100 watts.

 

Other peoples experiences may be different.

Edited August 16, 2015 by Alan de Enfield

[bottle]

Alan's figure seem to tally with my findings,.

 

I run 400 watts (24v nominal) with tilting and turning panels and have only ever seen 16 amps once and that was for about a second,

 

Instant reading (it changes all the time) batteries are at 80% SOC, panels are giving 9 amps, voltage 27v, load 5 amps, sun bright enough to give shadows but slight cloud cover. Panels are at optimum position, tilted and facing sun.

[Tom and Bex]

We have seen 36A @ 14.4v going into our batteries a few times so 518.4w from our 500w panels! Admittedly this is unusual, but we regularly see 25A+ from our panels if the batteries are low or we are using the washing machine.

 

Thinking of getting a third panel with separate controller to help a bit over winter. Getting too used to all this quiet and free electricity now and not looking forward to getting the generator back out!

 

Tom

[Alan de Enfield]

We have seen 36A @ 14.4v going into our batteries a few times so 518.4w from our 500w panels! Admittedly this is unusual, but we regularly see 25A+ from our panels if the batteries are low or we are using the washing machine.

 

Thinking of getting a third panel with separate controller to help a bit over winter. Getting too used to all this quiet and free electricity now and not looking forward to getting the generator back out!

 

Tom

 

So that's another one getting about 5 amps per 100 watts.

[Scooby]

We also have 500 watts it's peak was around 40 amps. But usually stays above 20 on a sunny day. 5 amps per 100w I would say is a good average for a decent day of sun.

[Bimble Solar]

Hi Psycloud

 

In my opinion for your set up - the 170w low-lights. If you have to have the panels flat it will make a considerable difference, especially autumn to spring.

 

Low light is a misleading term i'm afraid - most people think it means less light, but it doesn't. It means the angle of sunlight hitting the panels can be less direct.

On our bench tests in winter we saw much more power through these panels. I tested a couple of these panels yesterday at a crappy angle in very light cloud and they gave an instant 90w (I was testing that they worked!!).

 

Averaged over the year bigger panels such as 235w or 250w will produce more power for you. However in poor conditions you will get more power from the low light panels.

 

Please note: they are over 100v panels, so must be used in parallel (had a few customers killing their controllers by running in series).

Also MPPTs are a necessity with these, most PWM controllers only handle very low voltage, plus you get up to 30% more power from MPPT controllers.

 

Here's a nice MPPT article I like from Nigel at Prism Solar in Spain for anyone new to the MPPT world...

http://www.prismsolar.co.uk/shop/files/OffGridLiving/MPPTDraft.pdf?1027279486

 

Apologies if we don't reply quickly to any comments, we are busy bunnies and would love to have the time!

Thanks David for sending me the link to this so I could reply - if only I had time to peruse the forums!!!!

info@bimblesolar.com gets us direct if anyone has any solar questions they need help with.

 

All the very best!

[dor]

 

So that's another one getting about 5 amps per 100 watts.

I had 5.4A at 13.7V last week from a 100W panel mounted flat, mid afternoon. It was a very bright clear sky. The most I have seen is 6.4A in mid summer, which is pretty good for a flat panel with standard controller. I know you can increase the effectiveness by up to 30% by angling towards the sun, but unless you track all the time what you gain when they are pointing directly at the sun you lose when the sun is the other side. Much less hassle having them flat!