Using Load Tester

[lettersize]

Need to test pack behavior under load. The pack is rated 24v (8s).

Can i use this load tester
and additional volt meter?

The load tester is for 12v batteries, but i once can use it for all voltage pack, just should have external voltmeter(cause load tester won't show voltages higher than 16v), is that right?

 

[Jon NCal]

I don't think it would be a good idea, because it may have over-voltage protection circuitry, or if it doesn't, you may smoke it. Also, it is only meant for very short duration load testing, such as for starting a vehicle.

You can use other loads like light bulbs or space heaters for a load. Recommend also an inexpensive in-line volt/amp meter: http://electric-fatbike.com/2015/02/11/16-50-fuel-gaugetroubleshooterwatt-meter-for-your-electric-fatbike/

 

[lettersize]

I don't think it would be a good idea, because it may have over-voltage protection circuitry, or if it doesn't, you may smoke

Didn't though of that.
How about using it for individual cells? Or what device should be used to imitate 100amp-150amp load?

it. Also, it is only meant for very short duration load testing, such as for starting a vehicle.

That's actually what i am looking for. Peak current(on acceleration) is about 150amp, after that it's much less.
I want to see what levels are reached under peak load to calculate proper LVC level.

 

[amberwolf]

If you look around the forums for load tester, or heater, you'll find a few threads about better ways to do this.

 

[Ykick]

I use this. At 24V pulls between 2-3A which isn’t a lot but usually enough to get an IR reading for low C rate.

It loads about 6-7A on 66V pack. Cost nothing, bypassed thermostat wired directly to the heater element and can series more heater elements (range coils, old clothes iron, etc) to pull a little more load if desired.

 

[dilkes]

I use a 48V to 120V inverter something like this.

http://www.aliexpress.com/item/High-power-1200W-Generalduty-Power-inverter-DC-12V-24V-48V-to-AC-220V110V-high-power-for/32292930318.html?ws_ab_test=searchweb201556_3%2Csearchweb201644_4_10001_10002_10005_10006_10003_10004_62_9900%2Csearchweb201560_1%2Csearchweb1451318400_6151&spm=2114.01020208.3.125.4uJ16C

Mine has two AC outlets and with one of my George Foreman grills plugged in, I get about 15 amp draw...and I can cook a burger at the same time! (lol).

One other benefit of the inverter is that I keep my lithium batteries inside in the winter and can use them in combination with the inverter in case we lose power to run a few things for a while.

 

[Jon NCal]

He needs 150A at 24V...

 

[markz]

wired directly to the heater element and can series more heater elements (range coils, old clothes iron, etc) to pull a little more load if desired.

Seriosuyl, is that all you need, range coils?
Hook it directly up to the DC source and it pulls what it pulls (amps). Stoves are AC, so maybe it converts it to dc, like the treadmills.

 

[Ykick]

AC or DC doesn’t care with resistive loads. However, odd thing is the 120VAC power rating of most common household heater elements.

Odd because if you run 120VAC 1500W heater on 60VDC you won’t pull 1/2 the wattage but roughly only 1/4 rated wattage. That 120VAC 1500W heater element will only pull about 375W on 60VDC.

Now once you’re converted to DC it’s fairly linear relationship. 30VDC would be about 187W, 15VDC half of that 94W, so on.

There’s mathematic explanation why it works this way when converting power ratings from VAC to VDC bit I’m not qualified to quote any of that stuff.

This is based on what I’ve seen when using a power meter when load testing various cell count battery packs.

 

[markz]

AC or DC doesn’t care with resistive loads. However, odd thing is the 120VAC power rating of most common household heater elements.

Odd because if you run 120VAC 1500W heater on 60VDC you won’t pull 1/2 the wattage but roughly only 1/4 rated wattage. That 120VAC 1500W heater element will only pull about 375W on 60VDC.

Now once you’re converted to DC it’s fairly linear relationship. 30VDC would be about 187W, 15VDC half of that 94W, so on.

There’s mathematic explanation why it works this way when converting power ratings from VAC to VDC bit I’m not qualified to quote any of that stuff.

This is based on what I’ve seen when using a power meter when load testing various cell count battery packs.

Thanks Ykick.
I dont know much either, but IF I had to guess.......... I bet its RMS, just the AC sine wave averaged out, I think its like 75%.

Well now I am on the hunt for Microwaves and normal stoves. Landfill here I come!

Isnt it better to just use 100W light bulbs, or do you need a higher dc voltage for that?
Everytime I try and hook up 120Vac bulbs it never works. I just tried it now again. So maybe a 12V 100W bulbs are good.

Here is a good link

 

[Punx0r]

1VAC = 1 VDC

The non-linear relationship between voltage and power is because reducing the voltage applied to the heating element also reduces the current. So power being the product of voltage and current takes a double hit. Halving the voltage also halves the current, resulting in 1/4 of the power.

E.g. 1500W @ 120V

Current = P/V = 1500/120 = 12.5A

Resistance of the element is therefore: R = V/I = 120/12.5 = 9.6 ohms

Current at any given voltage = V/R
Power at any given voltage = V x I (or I^2 x R if you prefer)

So at 60V:

I = 60/9.6 = 6.25A
P = 60 x 6.25 = 375W (Check: 6.25 x 6.25 x 9.6 = 375W)

Hope this helps

 

[Ykick]

Markz - if you’ve gotta large supply of incandescent bulbs go ahead and try. Some guys here have made very impressive lighting load banks.

But my experience with 120VAC 100W bulb is they barely draw 25W on my 60V pack. That’s not quite enough for purposes.

Couple hundred Watts is usually enough though and yes, you can keep adding heater elements to your hearts content.

Thanks for the math Punx0r. Unfortunately, my eyes glazed over but I’m sure those smarter than me (ie; everyone) can use that info.

 

[Overclocker]

nichrome wire. easy to configure. fun to watch it glow

 

[markz]

^That is cool.

Nichrome (NiCr, nickel-chrome, chrome-nickel, etc.) generally refers to any alloy of nickel, chromium, and often iron and/or other elements or substances. Nichrome alloys are typically used in resistance wire. They are also used in some dental restorations (fillings) and in other applications.

as the heating coils of electronic cigarettes.

My first thought is you could buy that wire anywhere e-cigarette parts are sold.

Nice, https://www.fasttech.com/search?nichrome%20wire looks like it comes in 20, 22, 23, 24, 26, 28, 29, 30, 32, 34, 35, 36, 37, 38, and 39awg.
They seem to have very wide and differing ohm/m ratings, of course with the guage, seen some 100+ohm/m down to 7ohm/m.

Which guage would offer the most load? P = I^2 x R so wire with the most resistance. So the longest and thinnest wire (highest guage), you can get is the best.

https://www.fasttech.com/products/0/10014737/4035101-authentic-mkws-nichrome-80-resistance-wire-for
38 AWG (0.1mm) / 126.8ohm/m / 30m (100 feet) for $3.62.

Yeah I am building one fore sure. This is interesting.

 

[Punx0r]

Thanks for the math Punx0r. Unfortunately, my eyes glazed over but I’m sure those smarter than me (ie; everyone) can use that info.

I should have mentioned that it was Ohm's Law (with the power formula thrown in). For anyone dabbling with any kind of electrics I would highly recommend learning it since it's very simple once you get it in your head: It's a simple three-way relationship between voltage current and resistance, often depicted as a triangle. If you know any two, you can derive the other. Very useful - check out any of the multitude of learning resources on Google

 

[amberwolf]

And it can be remembered with a mnemonic of the Indian, the Eagle, and the Rock, for the version using variables E (voltage), I (current), and R (resistance). It's the one I learned when I was getting into ham radio as a kid....

The Indian sees the Eagle over the Rock (I = E / R)
The Eagle sees the Rock next to the Indian (E = R * I)
The Rock sees the Eagle over the Indian (R = E / I)

The only hard part about is remembering E instead of V, but remember it's the Electrons pushing and it's easier...or Electromotive force. Or you can substitute Vulture for Eagle, and then not have to worry about it. :lol:

This is the V version, from Wikipedia:

https://en.wikipedia.org/wiki/Ohm%27s_law

 

[Punx0r]

If you can just remember V = IR you can derive the other two by rearranging the question. I suck at algebra so used to substitute simple numbers to check my rearrangement. E.g.

V = IR
6 = 3*2

If I know voltage and current and want to calculate resistance, R(2) needs to be on its own on one side of the equation:

2 = 6/3

Checking back, 6 = V and 3 = I

So, R = V/I

 

[marty]

3/16" x 12" x 12" aluminum sheet
RESISTOR Alcol 100W 50 Ohm, part # HS100 50R 1%
LAMP HOLDER SPC Technology, Miniature Bayonet socket, part # 21722
BULB SPC Technology, Miniature Bayonet lamp 55V, part # 1835
FUSE HOLDER Cooper Bussmann, 1/4 x 1-1/4, Panel Mount, part # S-8002-1-R
FUSE Cooper Bussmann, 5A, 1/4 x 1-1/4, part # AGC-5
CABLE CLAMP Thomas & Betts, Catamount, .125 Diameter, part # N4NY-002-0-M
FEET Plastic Bumper, 5/8" McMaster-Carr part # 9405K18

 

[Overclocker]

^That is cool.

Nichrome (NiCr, nickel-chrome, chrome-nickel, etc.) generally refers to any alloy of nickel, chromium, and often iron and/or other elements or substances. Nichrome alloys are typically used in resistance wire. They are also used in some dental restorations (fillings) and in other applications.

as the heating coils of electronic cigarettes.

My first thought is you could buy that wire anywhere e-cigarette parts are sold.

Nice, https://www.fasttech.com/search?nichrome%20wire looks like it comes in 20, 22, 23, 24, 26, 28, 29, 30, 32, 34, 35, 36, 37, 38, and 39awg.
They seem to have very wide and differing ohm/m ratings, of course with the guage, seen some 100+ohm/m down to 7ohm/m.

Which guage would offer the most load? P = I^2 x R so wire with the most resistance. So the longest and thinnest wire (highest guage), you can get is the best.

https://www.fasttech.com/products/0/10014737/4035101-authentic-mkws-nichrome-80-resistance-wire-for
38 AWG (0.1mm) / 126.8ohm/m / 30m (100 feet) for $3.62.

Yeah I am building one fore sure. This is interesting.

pictured above is 0.8mm wire. just use longer/shorter or in parallel to get desired current