Solar Powered Trickle Charger?

[Upex]

Anyone know the sleeping current draw? Seem to recall a thread that mentioned it no so long ago, but would help a lot in knowing what panels we'd need to keep the old full for long periods

[X5Sport]

80mA springs to mind, but could be a little less.

[henrym3]

http://imgur.com/a/1pjc7

[henrym3]

That didn't quite go as planned but if you click on the link you should get some pics

[sleepyfolk]

Thanks Henry, very useful

[Upex]

Henry, did you check what voltage you get at the positive battery end of cable vs right out of the panel in same light? Ie any voltage drop experienced for your chosen installation (cable size and length or through controller).

Also, did you check if the sunroof causes a drop on current output? Wonder if it's blocking glass or not?

Assume you don't / can't open the roof when in its installed?

X5sport, thanks, I thought it was you with the numbers in the thread I couldn't re-find.

So at 80ma, assuming car not used at all, that's 24hrs x 80ma = 1,920 ma loss per day whilst sat sitting, so near as dam it 2amp, or 24watts loss per day.

Obviously this will be higher if not in sleep mode for the whole time, ie unlocking locking alarm etc.

So, assuming no further losses, a good quality panel which isn't behind blocking glass, and an efficent curcuit, then this would be easily replaced by even a small panel, I.e a 10w panel would offset the loss in 2.5 hrs of good sunlight each day, 20w would need 1hr 15m, 40w <38m, 80w a tiny <19m

If it were me, I'd spec for at least twice that loss, and I'd be looking at circa 5 hrs of day light and assume 75% efficiency to get my chosen panel size. 4amp, 84w loss,  so let's round up to 100w, better too much than not enough eh?  100w over 5hrs, 20w per hour, Mark up for efficiency and we're at 28w pannel size, so either a 25w or 30w would be my choosing for this set up depending on panel size and desired location or course, but circa £30 delivered, so a cheap insurance plan.

Obviously if you don't park outside in the sun, all this is pretty mute  )

[DJ_x5]

Sleepy - I haven't measured it but I think it must be around 400cm.sq (40cm x 10cm)

[sleepyfolk]

I think I quite fancy this panel https://www.maplin.co.uk/p/maplin-30w-f ... rger-n42en , based on our discussions so far and also my mothers motorhome is charging 2 x 90ah leisure batteries in a couple of hours with an 80w mono panel, she is obviously using a fair bit out of them with radio/TV, lights, water pump, fridge all running during the evening.
I figure a 30w that fits up there fairly easily will be ok to keep it topped up, a decent MPPT controller might help to balance the losses caused by the sunroof glass - time will tell!

[sleepyfolk]

[quote="DJ_x5"]
Sleepy - I haven't measured it but I think it must be around 400cm.sq (40cm x 10cm)
[/quote]

What wattage is it out of interest?

[Upex]

Sleepy, that's expensive. If you can wait, get one from China or Philippines etc, half the price and most of there kit is what goes into the type you looking at.

A mppt won't reduce loss due to blocking glass, there is no way round it, if the glass is blocking, you get less at the panel, simples. All you can do is have a bigger panel to cover the losses. Some glass is that restrictive that it's not worth it, but most is ok. Not a clue what they use in the sunroof etc.

40x10 is an odd size, very narrow, most are more square in form. Be interested to know what output it has.

[sleepyfolk]

Oh, I thought MPPT was supposed to give a better output for low light levels and partial shade?

[Upex]

They control it better, but there is only so much power in the light being received and nothing can change that. A decent controller will allow for better use of that light, but it's marginal really, they are more driven by more control so your handling the power better and not risking battery via peak up and downs in voltage output or reverse drainage.

Some will do better than others of course, depending on design and quality.

If you check the output of a panel in bright light, it can be quite high, and without a controller you can shove a lot more than 12v out into the system its connected to.