No, it not just you, I don't get it either -  running 12V batteries pancake  flat seems to be a design blind spot on a lot of equipment, especially vehicle mounted, when cutting off at 11.5V or something for loads, and rather higher for chargers would save a lot of lead from a premature trip to  the scrap man.

I reckon less than half lead acid cells  survive the full decade and a  thousand or more charge cycles they could do if managed well.

For some corner case military situations using a rechargeable to the death may make sense, but not normally, so even there could easily be a training/ warfare switch even for that.

With modern power FETs that can swing tens of amps when fully on and turn off to the nano-amp level there really is no excuse for a standing load of any kind that is even comparable to the natural ageing of the battery - which would be at most a few % of capacity per month or a shelf life of a year or more from full  to half flat. So for every amp hour of capacity, a 'dead load' of 100uA say.

10mA is nowhere near 'negligible' !!  (unless you have a spare few hundred amp hour battery capacity I guess) that's less than 1k ohm for heaven's sake !  I could run you a slow data radio link on that .Are they still using bipolar transistors ?

M.

I think it's because of all the pretty LEDs they use to indicate the battery and solar panel statuses - we're going to show you lots of LED lights to indicate that it's the middle of the night so we're running your battery flat by lighting all these lights to show you what's happening! Although from a very brief look at online forums it looks as if the LCD panel versions may have the same sort of drain.

I found it because I was testing the charging setup out on a little 1.2Ah battery and wondered why the battery had gone flat overnight with no load... 

even that's not great - LEDs that only need a mA or that flash are available. And dropping 10 out of 12V to light an LED that needs less than 2v  is not  best done by resistor.

M.

Last addition to this - just because it was rather entertaining. We used this set up (20W panel, charger with relay cutout added, 50aH LiFePO4 battery, decent 9 litre 12V fridge) while camping over the last few days. We set up last Friday morning and packed up yesterday (Weds) afternoon. Without a word of a lie, the battery ran out of juice at the moment I was disconnecting it all yesterday! A fine example that sometimes we achieve engineering excellence through brilliance, and sometimes there's a hefty dose of pure dumb luck!!! 

I will try to pick up a slightly bigger panel if I trip over one somewhere; contrary to my expectations this setup was pretty much self sustaining in full sun (excess charge in the day balancing out the night), but in typical UK camping conditions - as we had this week - it would be nice to have a bit more oomph so it can last a week.

Cheers,

Andy

if its a peltier fridge they generally use about 5 amps at 12 volts (depening on the module) , maybe your solar is better than you think  or the fridge uses less power, you would only expect 10 hours on battery alone

Hi , no it's a proper compressor fridge so much more efficient: draws 2.2A but only intermittently. I tested the setup before we left (when we had a couple of really sunny days) and it pretty much averaged no power drain from the battery over 24 hours. I was getting between 0.5 and 1 amp into the battery from the panel, depending on the angle of the sun. While we were camping it would have been much less most of the time as it was either overcast or only intermittently sunny.

On battery alone it would last 2-3 days with the fridge set to 4 degrees C provided it was cooled down first (again I'd tested that beforehand - having bought all the parts of course we then had several days of rain, but at least it gave me a chance to try that out). 

Not an advert, there are other makes available which I know are as good (my daughter is an arctic researcher who uses various makes and models to carry her frozen samples!), but this is it: https://carfridge.alpicool.com/products/alpicool-c9pt Goes down to -20C if you want, it's a whole different league to the peltier effect boxes.

I'd tried with our peltier effect coolbox a couple of years ago and that just lead to some very overheated and unpleasant milk and margarine...