battery chargers and inverters

Post a link.

.... Phil

power a couple chargers that I can't seem to find the 12V equivalent for.

Volt Ni-MH batteries.

inverter is bad. What would happen? Would I fry something?

The problem is the dV/dT. The rectifiers and caps are rated for the current you get when driven with a sine wave. Stresses on those components can be significantly higher. But maybe they can take it.

So, my experience is that it's perfectly safe to run most anything from an inverter...EXCEPT when it isn't.

Here's an example. Tektronix 211 miniscope. Good company. You'd think they designed good stuff. Plugged on into an inverter and it quit.

Gazing at the schematic showed why. They use a series cap and rectifier as a charge pump to charge the batteries. The cap has a different value depending on the market, 50 or 60 Hz. The fast rise input waveform from the inverter blew the fuse instantly. Could have been much worse.

Compaq laptop. They hooked the battery thru a FET to the input socket. Relied on the current limit in the adapter to set the charge current. If you put voltage into the port, it smokes the FET. But the manual did say, "Use only the recommended charger."

Bottom line is that it's a crap shoot. For most consumer devices, vendors are more concerned about saving half a cent than whether it works in an environment not in their spec. Clever implementations that save cost don't necessarily enhance reliability.

thanks Mike

So the best (safest) way would be to use a full s> Hi

power a couple chargers that I can't seem to find the 12V equivalent for.

Volt Ni-MH batteries.

inverter is bad. What would happen? Would I fry something?

You stinking damn troll.

Are you talking to me Phil?

the modified sine wave one?

power a couple chargers that I can't seem to find the 12V equivalent for.

Volt Ni-MH batteries.

inverter is bad. What would happen? Would I fry something?

Well...the simple answer to the simple question is, YES. Depending on the relative cost of sine and modified sine, real sinewave is the safest. BUT You'll probably find that 99% of the time you'd be ok with modified. What's the cost of failure?

If you have a 99-cent 9V charger from China, I'd expect they're very creative in how it works. I'd worry more about the battery than the charger. And if it smokes, so what?

The Ryobi is another matter. It's probably designed for abuse. But you probably don't want to smoke a $100 charger and have it destroy all your batteries.

First thing I'd do is call Ryobi. Then I'd find a news group more suited to commercial guys who might use one and ask there.

Failing that, I'd stick a current probe and oscilloscope on the power line and look at the peak currents with sine and inverter inputs. If the peak current ain't too much greater, you're probably ok.

Don't forget to do the math. If you expect to drive your truck to a remote job site and have batteries on fast charge all day in your truck, you might have. trouble starting the truck at the end of the day.

Phil, your act is really tired. Your off-the-meds rants used to be funny, now they're just sad. Get help, and while you are, stay off the internet.

John

power a couple chargers that I can't seem to find the 12V equivalent for.

Volt Ni-MH batteries.

inverter is bad. What would happen? Would I fry something?

to follow up on this, if the battery charger is using a cheap cap-based power circuit to produce consant current for fast (15 min to 1 hour) nicd and nimh charging, you may very well get flames and smoke coming out of your charger and/or batteries if used with a poor modified sine wave output from a generator.

when i worked at Black & Decker, we started getting a lot of returns of for commercial and industrial tool 1-hour chargers for just this reason. the more expensive 15 minute charges fared much better, but also would have occassional failures. and we were even using a Honda generator (supposedly quit good) in the lab to do the tests to determine cause of failure.

i believe that B&D has made significant strides towards making their chargers not blow up or massively overcharge the batteries under theses conditions, but, as noted above, its something of a crap shoot unless you check with the battery charger manufaturer first. (i would recommend checking with both a power tools manufacturer's hotline as well with their local repair outlet)

small trickle chargers, on the other hand, for 8-12 hour AA type charging should be a lot safer IMO and experience, as their low levels of current even if increased 3 times shouldnt hurt the cells much and ive never seen them catch on fire.

dave hillstrom wrote in news: snipped-for-privacy@4ax.com:

They -used- to. the TEK of today is not the TEK of the earlier years. the 200 series was a good product,very popular with field service people,especially the 213 with it's DMM.

the TEK 211(and 212,214,and 221) is not a fast charger circuit. in fact,TEK had to add a protection circuit and fuse the individual battery packs to keep the scope from catching fire,literally.

One other item to watch out for on the TEK 200 series is that the PCBs are held in place by 4 plastic pins,two on each case half. they shear off under impacts,then the PCBs shift in relation to each other,the female pin connectors spread open and their spring leaves fall out,shorting things out.

I have a 213 that's very intermittent. The connections you mention are a mess. Any kluge tricks for making it work better? I thought about just soldering 'em all, but you'd never be able to replace the battery.

to power a couple chargers that I can't seem to find the 12V equivalent for.

inverter is bad. What would happen? Would I fry something?

Thank you too Dave for your input.