Kind of an old design already, and very simple, but here's some shameless product placement:
Disclosure: I designed the circuit and board, and recommended the mechanicals for them. They did the rest.
For topical interest... it might be useful if you need an electronic load. It's protected for over and under voltage, reverse, and has a very flexible V(I) curve (including constant, or externally programmed, if that's all you need).
Tim
-- Seven Transistor Labs, LLC Electrical Engineering Consultation and Contract Design Website: http://seventransistorlabs.com
On a sunny day (Tue, 2 Feb 2016 19:18:21 -0600) it happened "Tim Williams" wrote in :
Do I see correctly 2 fan openings?
Efficiency?
I'm a bit ashamed to ask because it should be obvious for $659, but does it count the Ah that it's withdrawing?
joe
I don't think the panel meters they selected have that as an option unfortunately, so you'd have to add that.
It's designed to drain the battery from an unknown (and probably poorly balanced) state, so it's not a big deal for that. The current is also largely constant, so if you monitor where it transitions into "let's be careful, cells are emptying" territory, you'll have pretty much the capacity from that cycle.
Tim
-- Seven Transistor Labs, LLC Electrical Engineering Consultation and Contract Design Website: http://seventransistorlabs.com
Yes, the charge is burned off as waste heat.
Approximately 100%, give or take. :) (Or, I suppose, negative in a sense, as it requires AC power for the active circuitry, while burning all as waste heat -- but that was a better option than trying to make it self-powered over a wide range of discharge voltages, which would still preclude the ability to go to 0A.)
Likewise, something actually "high efficiency" (say, 90% dumping into the grid) would be terribly complicated, and much less safe (needing a careful design, lots of testing, and UL approval). Or dumping into another battery would be fine, but most users aren't expected to have that available.
Tim
-- Seven Transistor Labs, LLC Electrical Engineering Consultation and Contract Design Website: http://seventransistorlabs.com
On a sunny day (Wed, 3 Feb 2016 04:24:57 -0600) it happened "Tim Williams" wrote in :
You could add a 'cellphone charger' output :-) Reading light. Inductive cooking plate :-)
I think you'd be surprised what people expect from a $600 electronic device, and what can be delivered for that kind of sticker price.
The 'burn' might have been considered as a worst-case user-configured option.
RL
The price of small-production products is considerably different from "what people expect"!
Especially when it's designed and built in the US.
(If you have better ideas about the application and amortization of labor... we'd probably be interested in hearing about it, really.)
Tim
-- Seven Transistor Labs, LLC Electrical Engineering Consultation and Contract Design Website: http://seventransistorlabs.com
Why discharge? Auto shop use prior to replacing batteries?
"Tom Del Rosso" wrote in message news:n8vpkb$tsj$ snipped-for-privacy@dont-email.me...
Just to 'reset' the pack. This pairs with a charger, so you run it through a few cycles and charge capacity is back to normal(ish) again.
If you've ever had an e.g. laptop sitting around on the cord for months at a time, then picked it up and started using it portable, you've likely seen the same effect at work: the hotter/leakier cells get discharged, and the charge controller can't fix it, so the total capacity of the pack is simply less. After a few charge/discharge cycles, things get back in balance again.
Tim
-- Seven Transistor Labs, LLC Electrical Engineering Consultation and Contract Design Website: http://seventransistorlabs.com
Small product runs are brutally expensive in developed countries, but everything happens fast, fast, fast.
We used to see instruction manuals that said to completely discharge regularly, but then the word was that deep discharge can destroy some cells. Your device seems to avoid that by reducing the load to almost nothing near the end, but if I discharge my laptop it won't do that, so what am I missing?
When you "deep-discharge" (you're not, in the sense you imply above) your laptop, you're recalibrating its gas gauge. The theory is that if its gas gauge is accurate, it'll take care of the batteries (not allow a damaging discharge). That's why they tell you to completely cycle the batteries of a new laptop (three times).
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