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Releasing the Magic Smoke
#1
The guy on whose land I park a few miles from mother Pacific, handed me a harbor freight Nicad cordless 18v drill and asked me to see if it could be charged.

I was suspicious of it, but then I saw the origignal prop whatever california cancer warning sticker was still bridging the body of the drill to the battery. It appeared whoever bought this drill, used it upto the point the battery died and then placed it next to their garbage with a free sign upon it.

So I look up how to charge Nicad batteries,  opened up the battery pack to count the number of cells. When i applied 19.6v it took almost no current for very briefly. But Nicads apparently you constant current them until they get warm then the voltage drops indicating full charge.  Only way to get the current up was up the voltage.

I was monitoring current with my Windynation 'Watt's up' wattmeter clone which never worked well, but which did come with 8awg leads and was good enough for this task.

i was using my 150 watt voltage booster step up converter I bought for cheap a few years ago.  very similar if not exactly the same as this one:

https://www.ebay.com/itm/150W-DC-DC-Boos...100623.m-1

[Image: s-l1600.jpg]

I had voltage up in the 27v with the battery accepting 65ish watts range when i noticed the battery started getting warm, and I pulled the Anderson powerpole inbetween the wattmeter and the Nicad battery.

Apparently, when i did so, removing the 65ish watt load, and even though the wattmeter is rated at 60voltsDC, a voltage surge smoked my Wattmeter. I should have disconnected the andersons on the other side of the wattmeter, or cranked voltage back down to the point the battery was accepting little to no amperage before disconnecting it.

So while I smoked my wattmeter, this wattmeter never worked well in terms of recording AH or WH accurately, even though instant amps or watts were very accurate, sometimes, other times the display would jump around 20% of actual voltage and amperage, and sometimes the thing would freeze up entirely.  I bought it primarily as it came with 8awg highly flexible leads, to which I added 45 amp anderson powerpoles.

i am going to buy another wattmeter that comes with 12awg leads, and transfer these 8awg leads and powerpoles to it.

[Image: 61nXT6%2B1LjL._SL1500_.jpg]

I have had one of these wattmeter clones on my meanwell power supply since 9/2014.  Very great seeing how much amperage at what voltage and how much AH and WH has passed to the battery being charged. I have another wattmeter more portable i use on loads, like my fridge.

These wattmeters are hardly perfect, especially at very low currents, but I still find them useful enough and nothing better to replace them for what i want them for.

So Consider the potential voltage spike of removing a load while a charging source is delivering it amperage, attempting to hold it at a certain voltage.  The cheap step up converter i was using apparently has nothing to prevent the damaging voltage transient, and if it did, like most devices should, these spikes are likely cumulatively damaging to whatever is designed to suppress it ether on output or input side.

Which is why one should never unhook a solar controller from a battery while the sun is shining on the panels, and to a lesser extent, removing solar panels in full sun,  that are delivering a significant portion of their rated capacity to a load, which would be the charge controller.  Diodes in the panels, especially if they are in series, might smoke.
  
Always best to slow the flow before quickly disconnecting.

There could be a 'thats what she said!" joke in there somewhere.

By the way the harbor freight drill battery is apparently still quite capable, i used it to drive several #8 4 inch long wood screws into stacked pine 2x4's.   This sub 3$ step up voltage boost converter might have smoked my ~ 20$ wattmeter due to my ignorance/arrogance combo, but it has now made 12v fans levitate, EQ'd a group 31 flooded battery at 16.2v, and now sucessfully recharged  a 'disposable' drill battery into full usefulness.

I will leave out the details of the  story of the 'free'  Hedge clipper 24v Nicad battery I also used it on, as I missed that short window where the battery got warm and the charger should have been removed.  

Thermal runaway, pop gurgle smoke!!! ARGHHHHHH. WHERE'S MY  eye protection  hold breath run towards fireproof container please don't explode or set fire to my workshop story.

But on a positive note the cheapo 150 watt rated converter linked above, with an additional 60mm computer fan atop the heatsink, has no issues passing ~200 watts for a few to several minutes.
Smile
[-] The following 6 users say Thank You to sternwake for this post:
  • Scott7022 (08-11-2019), rvpopeye (08-11-2019), heron (08-11-2019), Texjbird (08-11-2019), Gapper2 (08-11-2019), frater secessus (08-11-2019)
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Messages In This Thread
Releasing the Magic Smoke - by sternwake - 08-10-2019, 11:56 PM
RE: Releasing the Magic Smoke - by Roadtripp - 08-11-2019, 10:13 AM
RE: Releasing the Magic Smoke - by sternwake - 08-12-2019, 02:16 AM
RE: Releasing the Magic Smoke - by rvpopeye - 08-12-2019, 04:38 AM
RE: Releasing the Magic Smoke - by sternwake - 08-12-2019, 02:08 PM
RE: Releasing the Magic Smoke - by S Cello - 08-12-2019, 03:16 PM
RE: Releasing the Magic Smoke - by sternwake - 08-12-2019, 04:31 PM
RE: Releasing the Magic Smoke - by Roadtripp - 08-12-2019, 09:59 PM
RE: Releasing the Magic Smoke - by sternwake - 08-12-2019, 11:36 PM
RE: Releasing the Magic Smoke - by Roadtripp - 08-13-2019, 08:17 AM
RE: Releasing the Magic Smoke - by sternwake - 08-22-2019, 06:43 PM
RE: Releasing the Magic Smoke - by B and C - 08-22-2019, 07:03 PM
RE: Releasing the Magic Smoke - by sternwake - 08-23-2019, 12:39 AM
RE: Releasing the Magic Smoke - by sternwake - 08-23-2019, 03:27 PM
RE: Releasing the Magic Smoke - by sternwake - 08-23-2019, 07:28 PM
Releasing the Magic Smoke - by Cammalu - 08-24-2019, 05:25 AM
RE: Releasing the Magic Smoke - by sternwake - 08-24-2019, 06:34 AM
RE: Releasing the Magic Smoke - by Scott7022 - 08-24-2019, 06:45 AM
RE: Releasing the Magic Smoke - by sternwake - 08-24-2019, 07:42 AM
RE: Releasing the Magic Smoke - by CatPerson - 08-24-2019, 11:48 AM
RE: Releasing the Magic Smoke - by sternwake - 08-24-2019, 01:06 PM
RE: Releasing the Magic Smoke - by sternwake - 08-25-2019, 12:18 AM
RE: Releasing the Magic Smoke - by sternwake - 08-25-2019, 12:43 AM
RE: Releasing the Magic Smoke - by Roadtripp - 08-26-2019, 11:03 PM
RE: Releasing the Magic Smoke - by sternwake - 08-26-2019, 11:58 PM
RE: Releasing the Magic Smoke - by rvpopeye - 08-28-2019, 08:11 AM
RE: Releasing the Magic Smoke - by sternwake - 08-28-2019, 04:36 PM
RE: Releasing the Magic Smoke - by sternwake - 08-29-2019, 07:38 PM
RE: Releasing the Magic Smoke - by sternwake - 08-29-2019, 09:38 PM
RE: Releasing the Magic Smoke - by sternwake - 08-29-2019, 11:41 PM
RE: Releasing the Magic Smoke - by rvpopeye - 08-30-2019, 02:38 AM
RE: Releasing the Magic Smoke - by sternwake - 08-30-2019, 02:50 AM
RE: Releasing the Magic Smoke - by weigh2ez - 08-30-2019, 10:58 AM
RE: Releasing the Magic Smoke - by sternwake - 09-05-2019, 03:20 PM
RE: Releasing the Magic Smoke - by Roadtripp - 09-05-2019, 09:12 PM
RE: Releasing the Magic Smoke - by Roadtripp - 09-05-2019, 09:07 PM
RE: Releasing the Magic Smoke - by Blacktank - 09-05-2019, 10:47 PM
RE: Releasing the Magic Smoke - by Scott7022 - 09-05-2019, 11:56 PM
RE: Releasing the Magic Smoke - by sternwake - 09-06-2019, 12:04 AM
RE: Releasing the Magic Smoke - by Snikwahjm - 09-06-2019, 04:20 AM

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