The issue here is usually one of internal resistance and heat
Its actually OK to have a peak start current of 600A provided that the starter motor then turns and drops it to 200-300A.
That should be easily doable with a 30Ah battery
30 f these would probably start a car dead easy
That's a good 'un. At least you disassemble the UPS. I've had similar but disassembly would have required cutting of the metal frame work not just undoing a few screws/
That's the problem APC UPS's don't drop to float charging they stay at or near the bulk rate and with no temperature compensation (automatic or guesstimated).
I've "got at" min reduced the charge voltage, adjusted the firmware calibration and fitted a temerature controlled fan. Before being "got at" it used feel decidedly warm and would report temperatures over
40C. Now it's coolish to the touch and reports temps of 30 C.Recycle time I'm happy to sacrfice. I have mine set not to power back up after switch off due to low battery until it has 15% charge. That used to take 10 to 15 mins, it's now around 30 mins.
APC...
As for the orginal portable starter thingy I wouldn't be surpised if it could deliver 200A when fully charged, It just wouldn't do it for very long.
We have a few here and there and in all they seem, well more recent ones, to be a bit better in that respect..
In article , Andrew Gabriel scribeth thus
Have got some of the original fit from this firm and they seem to last well...
I read somewhere that that make were around the best fro UPS service..
Another good 'un here what you can do with a meter;!...
It would have been more accurate to have described it's size as being "only a bit bigger than a mobile phone from the 70s".
The close up of it in the hands of the 'mechanic' suggests that it, and the cables, are somewhat bigger than you suggest. Whilst the cable gauge seems to be a bit on the light side compared to the much longer cables typically used to make up conventional jumper cables it's heavy enough to pass the 200 amps without fear of melting during the half minute or so it would take to exhaust energy contained in the battery and the very short length of the leads limits the volt drop, probably to less than what you'd see with 'standard length' jumper leads.
WARNING: The following anecdote is quite long but does ram home a point.
I remember one time, when our automatic car's battery was on its last legs and I made the mistake of leaving the parking lights on with the engine off whilst waiting for the missus to purchase a fish 'n' chips meal for our tea from the local chippy (which, fortuitously, was just 5 minutes walk from home) whilst returning from an outing to somewhere local.
By the time the missus returned to the car, some ten minutes or so later (the chippy was rather busy), there wasn't enough life left in the battery to crank the engine by much more than half a revolution. I really should have left the engine running or else completely switched off the lights and any and all accessories to avoid this embarrassment since I was already well aware of the battery's shortcomings.
Since we were only 5 minutes walk from home, it was just a matter of pushing the vehicle into a less exposed parking spot and locking it up to make the short trek home carrying our chippy meal and the slightly larger NiCad version of the aforementioned emergency jump start power pack we kept in the boot for just such an emergency so it could be put on charge (typically these NiCad based emergency jump start battery packs would be flat by the time they were called upon to fulfil their duty as was the case here).
Since it takes several hours to fully charge the 1.2AH 10 cell battery from its mains charger, I decided to check out what I had by way of 12v SLAs as a backup option to the emergency starter pack and chose a 12AH SLA I'd bought in our local flea market the previous year for a fiver. This proved to be in a lower state of charge than I'd measured using a borrowed DMM at the time of purchase, just over 12 volts when using a DMM that *didn't* have a flat battery to give inflated voltage readings as the one I'd borrowed to test with in the flea market must have done.
No matter, at least it was still above the 12v mark so I'd hooked it up to a charger for a test charge which suggested it was still in good condition. I'd then used a pair of those 1.2Wp solar panels designed to keep a car battery maintained against leakage when parked for weeks at a time in remote country places not blessed with mains power. I simply hung the panels out of the east facing windows and let the battery charge up 'for free' entirely from solar power until the voltage finally started to go north of the 14 volt mark a week or three later.
I tested this battery with 55W halogen lamp loads for brief periods of time to monitor its behaviour voltage wise, using it for the odd 12v test supply over the next few months. Basically, by the time I came to borrow it as a jump start battery, it had been given a brief top up charge a few months earlier and then simply left alone.
When I decided to make use of this battery, I bodged a couple of short jumper wires similar in gauge to that April Fool jump starter pack with crock clips and spade connectors to attach to the battery and trotted back to the car after allowing the 'proper' NiCad based emergency starter pack a good hour's worth on its mains charger.
Needless to say, after allowing the proper pack to transfer some of its charge back into the car's own battery, I managed to crank another revolution out of the engine without any hint of firing up. I then hitched my makeshift jump start battery pack up and tried again. Much to my surprise, the car started up just as if I'd dropped a brand new fully charged battery into the place of the old one.
That 5 quid fleamarket purchase proved to be one hell of a bargain which still stands, largely unused, on my office window ledge in between its annual solar powered charging sessions with no signs of deterioration in regard of its capacity to power 55W lamp loads without voltage droop, managing to keep its terminal voltage above the 12.67 volt mark for the
11 months of the year that it isn't receiving its annual solar powered topping up charge.I've not had any occasion to use it as an emergency jump start battery in the 3 or 4 years since I was forced by those events to fit a new battery to the car. I think I aught test it as a starter battery just to reassure myself that it's still in good condition.
The point of this anecdote was simply, "Don't let first appearances deceive you." Modern Li-Ion or Li-Po batteries of the size shown in that advert can easily pack the required punch to start a car that's merely been disabled by a flat or weak battery.
If a secondhand 12AH SLA of dubious condition revived merely by a 2Wp solar charger for a few dozen hours worth of summer sunshine is capable of jump starting a 1.6 litre Astra Automatic with a totally flat battery, don't be too surprised that the April Fool charger you were scoffing at should be more than capable of the same feat. After all, 200 amps for just 10 seconds represents just over half an ampere hour of charge. If you can't get the engine to fire up after ten seconds of cranking, the problem goes way beyond the simple matter of a flat battery.
In the light of my experience as extolled in my previous anecdote is anything to go by, I think your opinion would be more than justified. :-)
That's exactly the point! the big proviso being that the battery is able to deliver the required amperage without too much volt drop. Afair, Li- Ion or LiPo outperform lead acid batteries in this regard. A new car battery will typically drop to 8 or 9 volts at its terminals whilst cranking the engine on the starter.
I believe the UPS manufacturers are over specifying the float charge voltage requirements in order to maximise capacity at the expense of corrosion induced reduction in service life. From their point of view, it allows them to gain a higher autonomy rating using a cheaper battery which increases turnover in the "Consumables" department. It's the classic disposable razor blade business model pioneered by Guillette and copied by the inkjet printer manufacturers to an even higher extreme of end customer abuse.
My experience with that 12AH SLA over the past 5 years since I bought it secondhand from a fleamarket trader seems to strongly suggest that there's no need to keep their terminal voltage as high as the recommended
13.8 volts. I rather think a saner value for the classic 6 cell SLA is 13.5 volts (and possibly even a little lower than that but 13.5 volts seems a reasonable starting point to test the effect of float charge voltage setting on battery life).I rather think that a 10 or 20 percent reduction in per charge cycle capacity is a sacrifice worth making if it doubles or even triples the service life of these rather expensive 'consumables'. It's easy enough to compensate for the reduction of usable capacity per charge cycle by simply specifying a 10 or 20 percent larger capacity battery.
I know that this trade off between life and per charge capacity applies to Li-Ion battery technology but doesn't seem to be mentioned in the case of SLA batteries. My experience, however, does rather suggest that a similar trade off may also apply in the case of SLA batteries. If so, it's been one of the UPS industry's best kept secrets.
It wouldn't need to. 10 seconds worth at an *average* current draw of
200 amps is only some 33 ampere minutes, just over half an AH. It's highly likely that the battery pack could consist of just 3, maybe 4, 2000mAH cells (2AH) which could give you some 3 ten second attempts at cranking the engine.If all you're dealing with is the effect of a flat or weak battery, a ten second cranking time should be more than ample to allow the engine to fire up (and you'd still have another 20 seconds worth to play with after that).
I have a very accurate voltmeter sitting across my car battery. On a normal cold start it doesn't drop below 10v.
On a very cold day, it does. But I've never seen it anywhere near 8v.
We've got quite a few SLA batteries are remote locations supplying standby power and we float those of a 13.8 volt supply, batts last for years and we never have those swelling problems that APC UPS units have..
FWIW...
Cold oil or cold battery?
Andy
Both.
It will be a combination of both battery giving out less due to the cold and the oil in the engine being thicker due to the cold. Rover V8s do start very easily though so as long as everything else is in order turning over a little more slowly should not be an issue.
However, if its not starting then firstly check all the battery connections particularly both ends of the ground lead, right back to the engine. Corrosion on these often results in slow cranking. A simple test is to attach a decent jump lead from battery negative to good ground point on engine. If it then cranks faster you have a ground lead problem.
Mike
Aye.
Not sure what battery technology can produce a nominal 12 v from 3 or
4 cells. Lithium would but trying to draw 200A from 'em will trip the protection... Had a Li-ion powered screwdriver, worked well enough until you got a tight screw, start to stall the motor currennt goes up protection trips. Wouldn't have been too bad if "tight" was a decent torque but it wasn't.The batteries in these jump starter packs are normally 12 V Sealed Lead Acid of a few AH. They can take the abuse...
I'm sure they'd either forego the polyfuse protection in such a battery pack or else use a protective device rated for much higher current loadings than would be required in the case of a screwdriver battery.
Amen to that last remark! :-) I discovered just how effective a secondhand 12AH SLA of uncertain provenance could be as I related in an earlier posting.
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