I know that *some* of them don't know how to calculate AH correctly and they probably all overestimate a bit, but I already have a similar one which I know has a reasonable capacity.
Also, it will happily start a small car with a flat battery several times while only dropping one dot (out of 4) of "capacity".
I've just had two (ancient) lead acid batteries fail, leaving me only one good one. So I have to buy some replacements. As I think I said somewhere else, I'll do a temporary fix for one location using NiMH AAs when my 10 cell AA battery holder arrives.
These 12 volt LED strips sold for caravans etc have varying properties. I have one of them as a ring illuminator for macro photography, this works fine on 8 NiMHs (even as they run down). However the new ones which I've bought for the stables insist on a genuine 12 volts. Three of them won't light at all on 10 volts, one just gives a glimmer from a third of the strip.
Thanks for the suggestion; I have thought loosely about this in the past.
Bearing in mind that I only need lighting in the winter, what sort of daily watt-hours might I expect out of a 100 watt panel in the middle of winter? I have a reasonably unobstructed view to the south.
Dunno! But JOOI how far away is the nearest mains supply is it or might it be possible to string a cable across there like a phone wire size?..
Both sources and their predictions are quite accurate
Aligned south with 40 degree from horizontal tilt a 100W panel will yield somewhere around 80-100kWh per year with a monthly performance around 2 - 3kWh per month in December rising to around 12kWh per month in July
At about 60 degrees tilt you'll get better performance in winter with the sun closer to the horizon pushing that to 3-4kWh per month in midwinter with a reduction in summer to maybe 9kWh per month.
3kWh per month might be 100Wh per day but it could be a lot less as you've got to cater for multiple cloudy days, but size the loads right and even in the depths of winter with little visible sun the system will be dumping solar output (to an inbuilt resistive load) because the batteries are full.The 2nd website listed also has a calculator (4th tab) for standalone systems with a depth of discharge and load size option. The output produced has the percentage of days the battery is estimated to be empty or full in each particular month.
Ah. I'm pretty sure none of the vendors of those know how to calculate Ah correctly, and so it's 8000mAh @ 3.6v, ie 28.8Wh. That's if they didn't lie
- bigclive has a video on a '100,000mAh' version that's actually about
5200mAh.It's not implausible to fit 4x 2000mAh 18650s inside one of those packs, to
8Ah @ 3.6v is about right (though the bigclive one has pouch cells) if it's genuine.
While that needs a high peak current, it's only drawing it for a second or few. 500A is only 138mAh per second.
Another thing to check is whether you can charge and run the output at the same time. Most can't.
The raw car battery clips are usually straight off the lithium cells, so if you overdraw from there it'll kill the pack. The regulated outputs have a DC/DC converter that the pack decides to enable - either detecting a jack plug is inserted, or detecting end of charging of phones. You don't want to run into a situation where it has decided your 'phone' is now charged and it turns off the output.
Basically you have to find a use case that matches the supplied electronics, or you throw the electronics away and use the cells with your own management. The latter isn't implausible - a 3S or 4S BMS is a few pounds on ebay. Though you would probably need to know what the chemistry is to do that.
Further reading:
Theo
You can improve winter yields a bit with some white reflectors.
NT
Often when people say a car battery is flat, it isn't. Just so low it can't supply enough current for the starter. So all the jump start pack has to do is add enough current to start it. In rather the same way as those weedy jump start leads work.
" The values are shown as average irradiance measurements in kilowatt-hours, per square metre, spread over a day and averaged out over a period of each month of the year."
about 1.3 for London at optimal winter tilt
Now that is irradiance, so multiply by panel efficiency...
And losses due to frost and snow
Then compare the cost with runniing armored mains cables out to where the lights are needed
And sometimes they don't actually know the difference between a 'flat battery' and their can not starting for other reasons.
I got a knock the other morning (in the drizzle of course) by a neighbour asking if she could borrow some jump leads because her 'battery was flat and her car wouldn't start'. I grabbed my portable (Lithium) jumps start pack, hooked it onto her battery and got her to spin it over, which it seemed to do ok, but still didn't start. Then I removed the jump and asked her to try again, and it span over fairly well again on the cars own battery? I asked her if 1) it was turning over like that before I came out and 2) did it sound like it was spinning over like it does 'normally', she replied yes to both?
But not wanting to kill her battery I grabbed a spare car battery I keep for such things and some short jump leads (1m) and hooked them up and asked her to just keep it spinning over, as I'd previously hear one short instance of it trying to start. She did and after maybe about 10 seconds it slowly struggled into life.
She then added she's been on holiday for a couple of weeks and thought she might have left the lights on and that's why the battery was flat. I promised her that had she left the lights on for that period there would be no way the battery would light the interior light, let alone spin the engine over!
Funny ... she's not knocked since (a few weeks now) to say it needs a jump start again (so there is nothing wrong with the car) or thank me for helping her out in the rain. I might just buy and give her some jump leads then I can stay in the dry. ;-)
I think part of the driving test there should be more of an obligation for people to understand more generic stuff about their vehicles as some seem to think they run by magic. ;-)
Cheers, T i m
p.s. Yesterday, daughter and I stripped the passenger seat of a 3dr Polo for a friend and repaired the seat folding linkage. At his age (22) I had already completely stripped and rebuilt a seized Fiat engine (well, I was 15 for that one) and changed gearboxes and done all sorts of vehicular repairs, mods and rebuilds. All they (sometimes) manage to do these days is fit a sub in the boot. ;-(
It's a rented yard, may not be there much longer, not worth investing in a new supply. Even if one of the neighbours was prepared to let me have a feed, it's not a worthwhile option. Most convenient would need
300 metres of SWA.
Thanks for the detailed response. The winter figure would probably do for the lighting, but I still question whether it is a good investment, given that I only need power in the winter. I suppose it would let me put in CCTV, but actually I have had very little trouble in ~ 10 years (and CCTV is like advertising).
No, you don't heat stables like this!
OK its just that some years ago we had a radio system and no power for it in the end we used an old phone line no longer connected to BT stuffed IIRC 75 odd volts AC down it and then that was used to charge a battery overnight and during the day when the radio unit wasn't transmitting worked well for many years:)..
Knowing how little most people know about how anything works I'd have asked her to put the head lights on first. If they are good and bright then try an start it, do lights just go out or dim a little/a lot as the engine goes through compression. Does it turn over quickly or struggle?
If it struggles or the lights die I go for a jump start but (carefully) touching any of the easy to access starter current connections as well. A hot one and that could be cause rather than a flat battery.
Petrol or diesel? Presumably a modern fuel injected engine not one with a carburetta and float chambers that evaporate...
Of course not you're just a grease monkey to be called upon as an when and cheaper than AA/RAC/Green Flag membership.
Wouldn't work, she'd not know how to use ,em and would need your spare battery and/or car for you to jump from.
I thought there was somthing, but not much beyond which fluid in which hole and checking levels. Maybe tyre pressures?
Some (30+ I guess) bloke down the road during the cold snap, didn't understand that he had a flat battery, at about 6am he tried to start it, the starter solenoid just making the clicking noise as they do, he kept trying every half an hour or so, with the clicking getting slower and weaker, I think he expected it would somehow warm up and start working.
Whilst you are right, I wouldn't have considered her to be someone who would have got so confused ... and when she asked for the jump leads there was already a council truck hovering about who may have seeded the idea in her head.
Understood.
That was a question to her in 'is it spinning over as fast as it usually does' and different engines, starters, batteries sound different and what sounds slow to me could be perfectly normal.
Good point but again, in this case she said herself it sounded perfectly normal (but just wasn't starting).
Petrol I think Andy. I think I got a whiff of it along the way.
Nope, classic modern oversized SUV thing.
It does make you wonder. I think she's one of these who considers it perfectly normal / acceptable to 'knock up a neighbour' to borrow time / equipment / skills but may well be equally happy to offer help in return (like shelter if I find myself locked out in the rain).
Yeah ... you are probably right ... ;-(
I believe that is part of the test now ('now' compared with 'in my day' etc).
Yes, that should be covered for sure if it isn't already and they could even have an airline at the test centre to do it with.
I was going to say 'all drivers' should be able to say change a rear lamp but with more and more vehicles going for LEDs I think that would be too late now.
I think there are several types of drivers and two are being those who are interested and able in their rides and others who treat them (and anyone they park next to it seems) as a disposable appliance. The sad thing is that that is the way cars seem to be going. ;-(
Cheers, T i m
If it's really cold turning on your headlights for a short while increases the battery temperature and improves the available capacity of the battery for an engine start. Putting your car away in a heated garage or leaving it plugged in (block heater and battery blanket) whilst in the company car park is far better though :)
Well ... it might have been that or something else but when Mum had her 4dr Moggy saloon that seemed to be what was happening. She would go to use it in the morning and it 'wouldn't start' ("flat battery" (because she hadn't used it for ages etc)). She would phone and tell me and (more often or not), when I pop in at lunchtime, whilst being sluggish it generally did start.
I think it would have to be pretty marginal for that to apply though.
Bringing a battery indoors and letting it warm (without charging) up definitely helps (as I have tested several times).
I have also had what I call 'winter batteries' that when cold and have lost capacity wouldn't see me though a typical week of stop starts (without an off jump-start etc) ... but once though the winter would be fine for the whole summer and until the next winter. ;-)
Cheers, T i m
Didn't they all come with a starting handle?
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