UPS lighting?

[Mr Macaw]

Cars don't do that. They don't need to. They just apply 14.4V to the battery all the time the engine is running. That can not overcharge a battery, no matter what two batteries you connect to it.

The other battery won't cause a spike. The other alternator might, but in exactly the same way as the alternator on the other car.

Therefore the flat battery will not take enough current from the full battery to stop it being able to start the engine.

It has every time I've done it. From a battery that only just won't start a car, to one that's completely and utterly drained by having the headlights on all night.

I thought you said you should start the donor car?

It shows that even a big battery doesn't draw much current from a full smaller battery.

But at a slow rate, because you'll get an average voltage at the terminals of say 13V, which isn't high enough to charge a battery very well. So the full battery is still capable of powering the starter.

Easier to buy as big as you can afford.

Yes, I've connected it to some old batteries in the past with a total of 300Ah. Looking at the monitor a week later after some discharging periods have happened, it read something like 230Ah, and calculated the battery levels more accurately.

Whatever they do I'm sure they'd still work ok with huge numbers of batteries connected. Even if you increased the Ah by a factor of 50, it would initially say you have 30 minutes runtime left, but it would keep recalculating it as 30 minutes and not get to the point where it tells the computer to shut down until all the batteries are quite empty.

I'm sure it's more complicated than a voltmeter. It'll take account of current draw. For example a lead acid that's dipped to 12.2V open circuit is emptier than one that's dipped to 12.2V with a big load on it.

Yes. The UPS thinks you have a 20Ah battery, and seeing a certain voltage at a certain load, thinks it's 50% full. But you really have a 60Ah battery, so that voltage at that load means it's emptier than the UPS thinks. BUT.... as it's a bigger battery, 30% full is more run time than 30% full on the original UPS battery alone.

They all tend to be the same size fort a certain Ah.

Funny, I usually keep my car battery for over 5 years.

By killing I was thinking of harming it quickly, so you'd need to buy a new car battery if you discharged it a handful of times.

Well as I said before I flattened mine completely many times, and didn't notice any reduction in capacity.

It was still running fine when it was 6 years old.

I did it 15 times. Folklore says if you do it 1-3 times you need to buy a new one. Presumably that was the case in the old ones where you had to top up the water and all that stuff.

I didn't se any drop, if there was one it wasn't big enough to notice.

I guess not, but you'll probably be in the house if the lights are on. You could always get the computer to switch off a relay. If you have a computer on 24/7, wire a relay that's powered off one of its PSU lines.

?

It was a wild guess anyway. My computer only takes seconds to shut off. 20% is well more than enough.

Actually, the UPS we both have will flash the battery LEDs if it thinks the battery will not last x minutes on its remaining charge at that load. I can get that to happen now by loading it with 1kW. I think the batteries are only 2-3 years old.

Huh? Why do that?

That's what I meant. I call them things CBs. CB means Citizens band, isn't that what you use? Or is that only truckers?

I said "anything electronic", and you said "within reason, some stuff needs to be 'small' for example" - what things were you referring to?

But a motorbike on dry roads is still bloody dangerous, just ask anyone working in an emergency ward.

I sacrifice safety by being lazy and not earthing everything.

I'll stick to my car. With no seatbelt.

[T i m]

Well, they may try to apply 14.4V but once the alternator is at full power (current) the voltage wont be that high. It will only reach that voltage when the battery is taking less current than the alternator can supply, then the current will slowly drop off.

Incorrect and I'll see if I can explain why. Take a half charged 40Ah car battery and a half charged 10Ah motorcycle battery, join them together and connect to your car charging system and start the car.

Assuming the alternator can put out 20A and the batteries take the current equally (10A each), the motorcycle battery will be charged in the first half hour and the car battery only a quarter charged so

*it's* terminal voltage will only be that of a 3/4 charged battery. So, the alternator will continue charging the bigger battery and the smaller battery will now be being overcharged.

If you get to the point where the big battery is now fully charged, you turn off the engine and connect your electric cooler (the chances are it's wasn't an actual 'fridge'?). ;-)

Now, again, assuming the current drawn from both batteries will be split equally and the cooler draws 10A, the same battery will be flat in 1 hr (it will be less at the 1hr (reserve capacity) rate but let's keep it simple ) and the big battery will then carry on. However, as the voltage drops the smaller battery will also carry on trying to supply current and so be even further (over) discharged. If this over-charge / discharge process carries on the smaller battery will be killed pretty quickly. Now, the principal still applies if the batteries are supposed to be the exact same because they rarely are and rarely continue to be if they were.

Attaching it with jump leads might though.

Yes but no, it won't.

Generally, and if you are quick (and assuming the dead battery isn't faulty (shorted cell), no, it won't.

I said yes. ;-)

Yes, it's possible that two fairly flat batteries will start a car that one alone won't. One that has headlights on all night will not help an already weak battery though.

If I was jump starting a car with another I'd first try it with the donor engine off and if that didn't work I'd run the donor engine for a couple of minutes, turn it off then try the slave car again.

It will though, again it's ohms law.

Yes.

Correct. It *will* charge it though.

Yes, if it's done reasonably quickly (minutes).

Agreed. ;-)

Yup. To be able to 'calculate the capacity of a battery you have to monitor it and measure the energy it take during charge and what it gives out during discharge.

For an instant reading of capacity (not current charge) I have one of these:

It seems pretty good when testing it against a batch of new batteries and known weak ones.

I don't. (see all the above)

Depending on how it does what it does (like extrapolate the rate of voltage drop for a given load to capacity), possibly. ;-)

Yes, simply because the higher the current draw the more depressed the terminal voltage. That's why they use those low resistance testers to test car battery condition.

Correct.

Agreed. ;-)

Trust me, the semi traction batteries I have in my Moke aren't the same size as a 200Ah SLI battery (they are probably at_least twice the size).

And in the olden days they might last for 10+ years.

Ah, no, like I said I raced a pair (hard) but only 10 times in a year.

No, maybe not (measurably) over 'a few times'.

Sure, but at what capacity?

I often find what I call 'summer batteries'. They start and run the car fine when it's warm but as soon as it gets cold, they die (won't start the car one morning). This is often for two reasons.

1) The capacity will be much reduced when it's cold.

2) You are generally using it harder in the winter, making 1) even more apparent.

Nurse the battery though to the spring and it will probably carry on all that summer.

Replace the battery with one of the correct capacity and it will

*also* be fine all winter under the exact same conditions / usage.

Yup, probably not enough for ant obvious drop in capacity and depending on how fast you got charge back in it again.

Nah, not normally (depending etc).

That may have something to do with it (difficult to unsulphate a badly sulphated battery).

That's probably more accurate. ;-)

Yup. I think you can even buy such things but I might prefer to use an Arduino for something like that.

Sure, I was really talking about the concept of pre-empting the loss of capacity over time.

Interesting, thanks.

Because you can preempt the buildup of heat by getting a fan to start cooling before it's actually needed, potentially buying yourself some time (or ability pre overheating).

Oh no. That is a very different world. ;-)

Erm ... battery chargers, power supplies, my battery discharge rig dummy loads, amplifiers ...

Again, the motorcycles themselves rarely are, it's either the rider or 'other people'.

Till something goes wrong ...

I'd be too bored with that. I like to regularly swap between being a pedestrian, a cyclist, a motorcyclist and a car driver. 'Variety is the spice of life' they say. ;-)

You rebel you. ;-)

Cheers, T i m

[T i m]

I would say from the bottom of your stomach as I believe it's to do from the overconsumption of food.

You 'have to'?

Quite.

Yes, but what damage might it do in the process? If it's a thermal overload trip it may be all the electronics will be damaged before it heats up sufficiently to trip?

That's the idea (to not rely on just the fuses in the plugs relying the lighting circuits).

Not sure.

I'll look into it. Worst case was just a housing to take two std DIN MCBs.

Lets hope, although surge loads like inrush don't quite have the same instantaneous current peaks (that kill electronics) as real spikes caused by stuff failing.

Cheers, T i m

[Mr Macaw]

Huh?

Hate. Typographical error.

I doubt it. The thing is quite happy starting big motors and the inrush= current in loads of computer PSUs (which can easily trip bloody circuit= breakers - bring back the fuse!).

gh to trip a health and softy breaker but not a proper manly fuse.

But bulbs blow so quickly that the short isn't big enough to knacker any= thing.

circuit, so anything really bad would likely blow that.

nd inrush things on big server power supplies.

The only thing I've broken with a blowing bulb was a =A35 piece of shit = thyristor output PIR detector from China. I always use relay ones now (= mainly because they cause LEDs to flicker as the current isn't high enou= gh for them to work properly).

-- =

Abdicate (v.), to give up all hope of ever having a flat stomach.

[T i m]

Ah, like I said then, not a fridge but a 'cooler'. A fridge has the means of cooling down to a specific temperature. Your 'cooler' can only reduce the temperature to something like 20 degrees below ambient.

CA.

A 12V 'battery' is made up of 6 x 2V cells.

They are viable for many people of course.

Yes, it's a good 'idea'. However, I understand it takes the equivalent of 3 gallons of petrol to crack enough hydrogen to duplicate the performance of 1 gallon of petrol ...

And the change the composition of the lead plates as well I assume? You have a degree in electronics you say?

Ain't that the truth. ;-)

As do I, but for most people they have to ride some pavement to get to the tracks.

Ok.

I'm pretty sure that is the intention of 99% of those who crash. ;-)

Cheers, T i m

[Mr Macaw]

A fridge is anything which cools the inside temperature of a box. Some methods might be more efficient than others, but it's still a fridge.

What?

Huh? We're talking about how much CHARGING CURRENT the "10V" battery would TAKE from the good 12V battery.

That'll be why there are so many of them, oh wait.... no places to charge them, too long to charge them, not enough range, too expensive to buy, too expensive to replace the batteries after 5 years, .....

But you can crack the hydrogen with any power station, including renewables. So when oil runs out, you can still make hydrogen.

I don't know what type of battery it was, but probably not lead acid. I'm just repeating what I saw in an article years ago.

Yes, but when travelling form A to B, the car is best.

Most people never have more than a bump in their entire driving life. I put a seatbelt on if the conditions are dangerous, eg fast roads or snow.

[T i m]

Yes, that is the generically accepted use of the term, however there are 'other solutions' that aren't fridges that are called something else, like 'a freezer' or more importantly 'a cooler'.

Not once you have gone past the generic definition it isn't. Most (actual) refrigerators, like most freezers have the ability (requirement) to reduce the temperature within their enclosure to an absolute (not relative) temperature. No matter if you live in the desert or the snow, you want to keep your milk at say -3 DegC, just in the same way your freezer needs to be -18 DegC or so.

Your 'cooler' does not have the ability to reduce the absolute temperature but simply cools the air to a maximum of -20 DegC below the ambient temperature. So, if you took it into the desert it would only manage 20 DegC which would hardly be considered 'fridge like. Take it to somewhere around freezing and it would now be colder than most freezers at -20.

Anyway, back to the point, I questioned you that what you were describing as a 'fridge', wasn't actually a fridge at all but a cooler. Once you told me how it worked, you confirmed that.

Cranking Current. Any argument re being able (or not) of starting something with a small battery is simply down to it's cranking current. Just in the same way you can overload any source if the load is to big by comparison.

Yes, I have since noticed your point.

There are over here, nearly 60,000 in fact. There's in one in my back garden in fact. ;-)

Many places to charge them. You can now drive an EV from London to Cardiff along the motorway and charge all along the way.

That depends on what else you might be doing at the same time. A local restaurant has several charging points outside and a rapid charge might take the same time as a casual meal. Or if you are at work all day, often charging for free.

I could commute for a forthright on ONE CHARGE?

Again, 'depending'. If you have to otherwise pay any road tax, 'congestion charge' or daily parking charge an EV could work out cheaper than an IC alternative.

See above (and most batteries last longer).

Agreed. I was just stating that is was currently 1/3 the efficiency of petrol.

Whist I can't disprove the concept, I'm not aware of any real-world battery technology where all the 'charge' is carried in the electrolyte (specifically lead-acid).

Not if the only route is a cycle track?

Possibly, however 1.25 *million* people died in RTAs in 2010.

And you can always determine that at all times can you? You know when say a car goes out of control and hits you head on?

I hate these 'safety nuts'. ;-)

When you would generally be going slowly anyway?

You could be onto something though mate, an 'intelligent safety belt' that only prompts you to apply it when the conditions are known to be dangerous. ;-)

Cheers, T i m

[Mr Macaw]

When I hear "cooler" I think of something that's just well insulated but doesn't have power. For example a bag or box you keep cool beer in when going on a picnic.

Which makes it a poor quality fridge in some countries. But to refridgerate just means to cool. And it's doing that.

Yip, and a double sized lead acid is the same as two in parallel. Double the cranking current.

As a percentage of cars on the road, they're pitiful.

Nothing compared to the availability of petrol stations, you don't even need a map for those. Until most petrol stations have electric points, it's an inconvenience.

Inconvenience again. In a petrol car I can be driving to a destination that I need to get to at a certain time, notice the low fuel gauge, and spend a few minutes topping it up. Not possible with batteries.

I don't know how long your commute is, but typical ranges I see for electric cars are 90 to 130 miles. A decent diesel will do 300-400 miles.

Yes you might get the money back eventually. But you can get an old banger petrol car for hundreds. An electric car requires a big outlay, then new very expensive batteries every 5 years. And a 2nd hand one will probably come with knackered batteries. I worked out the savings I'd make (no congestion or parking, just petrol saving) and it came to precisely zero. Plus I'd have spent that money at the start instead of on petrol over the next 10 years..

I've never heard of a battery having a decent capacity after about 5 years.

How does the efficiency compare to battery cars?

I saw it on a technology program years ago, and can't remember anything about it apart from the fact that you emptied the battery then refilled it (in a similar time to putting petrol in your car), and the petrol station recharged your electrolyte later. It could be this:

Unusual for that to happen.

Even though they were wearing seatbelts....

Anyway, what is that as a percentage? How likely is it that John Smith dies of a car accident or of something else?

I go by likelihood. For example driving around town where most people are doing 20-40mph, that's safe. Driving on country roads at 60-80mph, not as safe.

?

But very likely to come across somewhere you can't stop or steer. An accident on tarmac usually has one or both drivers brake hard just before impact, lessening the blow.

Cars with radar brakes should remove almost every single accident.