Building a 2.5 kW resistor load bank

Building and testing a 100A PWM controlled resistive load bank for testing 48 volt batteries. The resistor pack is made up of (16x) 0.25 ohm resistors that can be connected in series, or parallel groups.
The resistor is made from 18 awg Nichrome wire. In ambient (still) air, it starts to glow at 8.5 amps, and is glowing orange at about 14 amps, and at 22 amps it's bright orange. With a forced fan blowing, I was able to draw 22 amps with just a trace of red glow, and 29 amps with an orange glow.
100A (mine died at 60A) solid state relay
www.amazon.com...
Nichrome wire 18 awg
www.amazon.com...
Bakelite / Phenolic plate
www.amazon.com...
Copper bars 10mm wide
www.amazon.com...
Ammeter 0-50A shunt
www.amazon.com...
High current disconnect
www.amazon.com...

[@rataloadbank]

Super strong hands-on ability👍

[@aussieknowhow]

Thanks mate, I really enjoyed watching your video and got some great ideas for the battery testing system I'm looking to build 👍

[@prashkd7684]

I believe you can get tungston tubes (used in toaster elements) to encapsulate each wire. That way you won't have to worry about them touching each other. Great video by the way. I am building a resistor bank using power reistors and man the project cost shoots up quite rapidly with these expensive buggers. I like the idea of using nicrome wires but the final product is a bit too dangerous-to-work-with for a hobbyist like myself.

[@waynec369]

Stiff extension springs can be your friends here...

[@MPC30]

Com este ssr a corrente se mantem constante na descarga das baterias ou a a corrente diminui com a tensão.

[@MPC30]

Como esta ligado o SSR esta em série com a resistência feito um dimmer?

[@SiriusSolar]

Nothing like a hot wire burn is there?

[@mwint1982]

Possible to pre-stretch the wire? Like new guitar strings

[@etischer]

I pulled them as tight as I could by hand, they were like banjo strings. As soon as they heated up, they relaxed slightly elongated again. Maybe the key is to wrap the wire up into a coil spring? Next time I'll leave more space between the wires, but this seems to be working ok so far. I could also add mica tabs to hold the wire in place, as they do on some toasters.

[@After_Tech_Industries]

Try having a spring at one end of each strip...

[@MR-si2xx]

SSR at these currents without a heat sink? Might well have been why the thing got toasted at the end..... Revision: I see that all the control elements are mounted on a heatsink (I think) - so maybe the heat wasn't dissipated enough (?) or just a cheap SSR.

[@etischer]

SSR is on a huge heat sink, and it never even got warm.

[@livedem0]

Why not use the heating elements from a couple cheap toasters? They’re already mounted on extremely heat resistant mica sheets that would prevent the nichrome wires from sagging and potentially shorting out.

[@etischer]

The resistance of the resistor I built is about 1 ohm, at 48V it would draw 48 Amps. A toaster would be about 16 ohms, and only draw about 3 amps at the same voltage. The nichrome wire in a toaster is much thinner.

[@caeli5532]

Why not spiral?

[@Matt-og5kd]

What is the point of bench testing these cheap batteries? What kind of diagnostic info are you looking for that you can't get from the BMS app? Wouldnt it be easier to throttle the bike while it's suspended, and tweak the battery current output thru controller interface? Very cool vid, you and Damien Maguire are my heroes lol

[@etischer]

We're actually building batteries for an electric airplane. Currently I'm testing a small 48v version of a much larger battery we're getting ready to build. We've done exhaustive cell testing already with off the shelf testers. I'm using this resistor bank for testing our clamshell and bus bar system, hope to show those off soon! I could use my e-bikes for load testing, but to sustain 2kW, I'd be doing +40mph. The e-bike won't draw much current with the wheel spinning in the air.

[@Matt-og5kd]

@@etischer I see, that definitely makes sense. Excited to see more of this

[@Matt-og5kd]

@@etischer what kind of cells did you go with for those batteries

[@etischer]

@@Matt-og5kd I can't get into detailed specifics, but there will be a future video about the batteries.