Upgrading solar panel system

[fjmike]

Not wanting to hijack the other thread. I am thinking of upgrading my solar power system and would like some advise, I have read Alans excellent webpage http://www.aandncaravanservices.co.uk which gets me on the right path. My current system is a single panel of unknown make and capacity,installed by my supplying dealer 11 years ago and is probably 80 or 100W.I know technology has moved on a pace so would presume that it would be best to dump the existing panel and replace with a matched pair. I know the present regulator is best replaced with a LRM1218, would this display on my LT500 control panel?. Is my Shaudt EBL 220 up to the job of keeping two Varta LFD90s leisure and Varta engine batteries happy. I'm not sure if it makes any difference there is also an OVP01 fitted as well. Thanks in advance.

[aandncaravan]

The Schaudt Elektroblock EBL 220 is one of those units that calculates the power left in the battery by monitoring all charge going into and out of the batteries. If any power is put into or taken from the batteries that the EBL 220 doesn't know of, then incorrect function and display values will result.

 

However, when paired with the limited function LT500 display, compared to the usual DT220 display, it is probably less relevant. Therefore while you will benefit from a Schaudt compatible Solar Charger, like the Votronic MPPT range, it isn't so essential as on other EBL versions.

The Votronic is quite a bit cheaper than the Schaudt LRM1218 but the Votronic doesn't come with all the cables which make the LRM 1218 install so simple.

 

 

If you have an old Solar panel, it is likely to be delivering less power than when it was new, but how much efficiency it has lost is anyones guess?

You could load it up and see what current it delivers versus a typical new unit? If you look on eBay you will find Solar Watt meters that are only a few pounds and they will tell you how much current the existing panel delivers.

 

 

Yes the EBL 220 is up to supporting 2 x LFD90 batteries, but bear in mind you are near the limit so don't discharge the batteries below about 50%. See the battery State of Charge chart below for guidance on how far to discharge the batteries. The column of relevance to the LFD90's is the Sealed/VRLA, first column so about 12.4v should be the maximum you discharge them. Not just to prevent overloading of the charger, but optimum battery life.

 

Also try and ensure that when you are working the charger hard on the habitation batteries, it is not also working hard on the Starter battery, as a flat starter battery can draw up to a third of the charger power on this model.

 

 

 

[fjmike]

Thanks for that Alan. I know you don't install solar but do you know if the Biard solar panels are any good

http://www.ebay.co.uk/itm/Biard-100W-Watt-Black-Frame-solar-Panel-12V-Battery-Charging-Motorhome-Caravan-/401223962224?_trksid=p2385738.m4383.l4275.c10

Or am I better off spending a bit more ?. Is there any mileage in changing the control panel or is it much hassle for little gain

[aandncaravan]

You could possibly upgrade the LT500 to a DT220 but the cost would be around £330 just for the parts and I don't think there would be any real value in doing so.

 

 

No opinion on the Biard either way.

 

[plwsm2000]

Sorry I cannot help you much with the control panel, but I have a few points to mention about solar panels.

Just as a "health warning", these are based on my own research rather than practical experience as I have just gone through the process of looking at panels, controllers etc for what is my first motorhome and solar setup.

 

1) If using more than one panel, be careful to select the panels so that their output voltage at max. power (Vmp) is similar. There are two reasons for this. Firstly, the lower voltage panel can consume some current from the higher voltage panel (unless you add some blocking diodes) and secondly, even with blocking diodes, you will never get the full power output from both panel even in "perfect" conditions.

To try and explain this, compare the specs for two (deliberately mismatched) panels from Photonic Universe. A 100W (https://www.photonicuniverse.com/en/catalog/full/85-100W-Solar-Panel-Back-Contact-Solar-Cells-for-Motorhome-Caravan-Camper-Boat-Yacht.html) has a max. power at 17.8V and open circuit voltage of 20.8V whereas a 150W (https://www.photonicuniverse.com/en/catalog/full/90-150W-12V-solar-panel-with-5m-cable-for-camper--caravan--boat-made-of-high-quality-German-solar-cells.html) has a Vmp of 20.2V and Voc of 23.9V.

When connected in parallel, the solar controller will operate on the common voltage from the panels and for a MPPT controller, it will find the max power occurring around 17.8V (in this example). This is because at higher voltages, the power (current) from the 100W panel will drop faster than the increase in power from the 150W. At this voltage, the 150W panel will probably only be outputting 120W or so and you will never achieve the 250W that you thought you should be getting. There are obviously better matched panels on the Photonic Universe web site and you cannot go far wrong with selecting identical panels of similar age.

 

If you are intending to use your existing (old) panel, I would recommend you measure the open circuit voltage (Voc) and get another panel with the same open circuit voltage. Even though your panel is 11 years old and will have a reduced output power, I would expect its open circuit voltage to be similar to what it was when it was new. I think the power degradation is mainly due to its ability to provide current (not voltage).

 

2) Make sure you compare panel power ratings under the same test conditions. These usually either STC or NOCT (Standard Test Conditions or Normal Operating Cell Temperature). STC is specified at 1000W per sq. mtr, 25 degC and global air mass of 1.5. NOCT is 800W per sq. mtr, 45 degC, AM1.5G and with a wind speed of 1m/s (I assume for cooling purposes). This makes a big difference as a 150W panel specified at STC has about the same output as a 120W panel specified at NOCT. I would assume that most suppliers would quote the STC figure as it looks better on paper!

 

3) I have no experience of the Biard 100W panel in the ebay link so cannot make any recommendations either way. One comment I would make however, is that some of the "specifications" in the advert do not make a lot of sense to me as they are incomplete (i.e. is TK Pmax = -(0.5+/-0.050) in units of Watts or % and why are they mentioning NOCT? To me, they either (most likely) do not really understand what they are selling or they are trying to baffle people. Just to reiterate, I am not suggesting the product is no good.

 

4) Personally, I prefer the specs of panels that use the SunPower Maxeon Gen III solar cells (again this is based on the published specs and not through good/bad practical experience). Although I try to look at specs "with a pinch of salt", I much prefer suppliers that do publish detailed specs to those that don't. My reasons for the preference to Sun Power cells is that they have slightly better efficiency ( = smaller panel size for similar power), have slightly better temperature and low light performance compared to other monocrystalline cells and have a longer warranty. They also come out fairly well in independent reviews (http://www.mpptsolar.com/en/best-top-solar-panel-manufacturers.html) (albeit for a bigger panel but using the same cells).

[fjmike]

Thanks for the input. I have to admit that most of the specs are over my head so haven't looked too hard at them. It maybe me not looking properly but all I can find motorhome wise for Sunpower maxeon is flexible panels. Where I want to put the panels is a bit tight on width which is why I thought the Biard was good value as other outlets have them at a lot higher price. I think I will go for two new panels , the old one can go on my shed.

[fjmike]

Thanks Alan I will stick with the LT500