I know nowt about generators but maybe someone can help.
I've just bought a cheap generator that outputs 12v/8.3A for battery charging.
Does anyone know how long this would take to charge a Series 3 battery? And is there enough power to use it to jump-start the car (I guess there's not).
Look at the Amp Hour rating for the battery. Divide that by the output of the genny. (55Ah battery / 8.3A = ~6 to 7 hours). This is not a precise science - the math may not be known to the battery concerned ;-)
No.
Charging a battery from a generator is not a particularly good idea if the DC is rectified from AC. This is because the rectified DC is likely to have high levels of AC ripple superimposed and batteries don't like that. You can alleviate this, to a certain extent, by adding a large capacitor across the DC output terminals of the generator.
Another thing to consider is that if the genny really is a cheap one (as opposed to an expensive one purchased cheaply) then the DC may only be half wave rectified and that will probably kill your battery rather than charge it.
If the genny output really is 12V DC then it won't fully charge the battery anyway - that needs something more than 13.5V.
As for using the generator to jump start the vehicle; I doubt that will work. The DC current needed to start any vehicle is several hundred amps. Unless the generator has short circuit overload protection I wouldn't even attempt it.
Of course, there will be a generator/battery charging expert along in a minute to quash all of the above :-)
"> Charging a battery from a generator is not a particularly good idea if
That is not correct, in fact some charger eithe deliberatly superimpose AC or pulse the DC. The theory is that the AC causes the gas bubbles on the plates to disperse. In fact most simple mains chargers have no smoothing, their output is straight raw rectified mains.
Snip>
More like 14 -14.5V to fully charge a battery.
Agree totally with that.
Regards Jeff
But it should be enough to use it to fill the battery for maybe 30 minutes and then try to start the car.
SG: See I knew someone would have the real story. I guess I made a bad assumption that car batteries behaved like the ones we use in DC UPS systems. Ya learn summat every day :-))
SG: Agreed, I was just trying to say that 12V won't do the job.
SG: Phew! Got something right anyway :-)
In article , Jeff writes
Asymmetric AC is _recommended_ for charging many types of battery, including NiCds and Lead-Acid.
I once saw a very big and very expensive NiCd battery become very quickly knackered by charging it from a solar panel - steady DC. And before someone jumps in, it wasn't being overcharged and it was top-uppable with distilled water. What killed it was dendrite formation
- at least one of the cells went short-circuit.
Regards,
Simonm.
They don't like smooth DC either - see my other post and the rest of the thread.
Incidentally, given how much is known about cell chemistry these days, one has to wonder in the case of some types of battery if the poor charging regimes aren't deliberate, forcing one to replace cells that would last far longer if well treated.
Regards,
Simonm.
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