Test a battery pack. How can i easily create a high amp load?

Batteries, Chargers, and Battery Management Systems.
Post Reply
eikido   10 W

10 W
Posts: 71
Joined: May 08 2019 5:07am

Test a battery pack. How can i easily create a high amp load?

Post by eikido » Mar 18 2020 4:00am

I would like to put a load on a battery pack to troubleshoot it.
How do you guys do this fellow forum members?

Frank   100 W

100 W
Posts: 174
Joined: Dec 10 2007 11:57am
Location: Maine/Nova Scotia

Re: Test a battery pack. How can i easily create a high amp load?

Post by Frank » Mar 18 2020 4:53am

What voltage? Electric heater controlled via contactor is one possibility.

Sent from my SM-T380 using Tapatalk

Frank

eikido   10 W

10 W
Posts: 71
Joined: May 08 2019 5:07am

Re: Test a battery pack. How can i easily create a high amp load?

Post by eikido » Mar 18 2020 6:25am

10s=36v nominal and 16s=60v nominal.

Frank   100 W

100 W
Posts: 174
Joined: Dec 10 2007 11:57am
Location: Maine/Nova Scotia

Re: Test a battery pack. How can i easily create a high amp load?

Post by Frank » Mar 18 2020 6:43am

Maybe try some incandescent light bulb(s) but a small heater might be better (depends on how much load you want to create).

A 1500 watt heater (or toaster) draws about 12-13 A at 120V (mental arithmetic) so at 60V would be half that.

Someone else want to check my numbers please?
Frank

eikido   10 W

10 W
Posts: 71
Joined: May 08 2019 5:07am

Re: Test a battery pack. How can i easily create a high amp load?

Post by eikido » Mar 18 2020 9:07am

That's not a bad idea.
Here is a 2000w heater at 230v.

https://www.biltema.se/en-se/constructi ... 2000034997


But how would it behave if i connected it to a 36v source?
It is specified to 230/2000w

->230v source
R = VxV / P = 230x230/2000= 26,45 ohms

->36v source
I = V / R = 36 / 26,45 = 1,36 amps?

So it would only consume 1,36 amps? I might need more :)

User avatar
zeccato   100 W

100 W
Posts: 177
Joined: Jan 17 2019 8:16am

Re: Test a battery pack. How can i easily create a high amp load?

Post by zeccato » Mar 18 2020 9:24am

If you have a balancer charger, while you load one you unload the other, (checking imput).
Full susp. folding 20 swxh r. (2011),. 02 2020 MacT8. batt. 48v. 25A Life (2012), and 48 7,5A a123 (2018?). Controller programmable EB3 12 FET. Charger Balancer 14s: TP1430C. Gophert CPS-6011 60V 11A. Mercury (rarely). Buzzer. https://www.google.com/url?sa=t&source= ... 6dXxc9-lNW

Frank   100 W

100 W
Posts: 174
Joined: Dec 10 2007 11:57am
Location: Maine/Nova Scotia

Re: Test a battery pack. How can i easily create a high amp load?

Post by Frank » Mar 18 2020 9:26am

^^^

Great idea if it will accept the input voltage.
Frank

john61ct   100 GW

100 GW
Posts: 5121
Joined: Dec 18 2018 2:06pm

Re: Test a battery pack. How can i easily create a high amp load?

Post by john61ct » Mar 18 2020 12:50pm

Define easily

And note that it's best for cap testing if possible to do individual cells rather getting a pack average - depends on the batt type of course.

I don't know the math myself, but can just use resistors.

They make aluminum and ceramic wire-wrap ones, seen 1000W and up in different ohms.

People toss them in a container of water if air cooling is too slow.



eikido   10 W

10 W
Posts: 71
Joined: May 08 2019 5:07am

Re: Test a battery pack. How can i easily create a high amp load?

Post by eikido » Mar 19 2020 2:34am

I think i will find me a 400w 8 ohms resistor.

That should discharge my battery pack at:
I=V/R=54/8=6.75A

P=IxV=54x6.75=364W

Am i missing something? Will i burn my battery pack or my house if i do this? :D

User avatar
ginekolog   100 mW

100 mW
Posts: 48
Joined: May 13 2015 2:48pm
Location: Slovenia, Europe

Re: Test a battery pack. How can i easily create a high amp load?

Post by ginekolog » Mar 20 2020 4:53pm

Buy 4 50W 12V halogent bulbs, connect in series and you get 200W 48V 5A load. Thats how I test my batt.
Giant Trance X2 + BBSHD + 52V + 17,5 Ah = :bolt: :bigthumb: :D

eikido   10 W

10 W
Posts: 71
Joined: May 08 2019 5:07am

Re: Test a battery pack. How can i easily create a high amp load?

Post by eikido » Mar 20 2020 5:46pm

ginekolog wrote:
Mar 20 2020 4:53pm
Buy 4 50W 12V halogent bulbs, connect in series and you get 200W 48V 5A load. Thats how I test my batt.
Awesome! I will try this :) It will be a cheap test. Thanks.
So the resistance over one 12v, 50w halogen bulb is really low?
Something like 2.5 ohms (2.5x4=10 ohms)?

I=48v/10ohms=4.8A

User avatar
amberwolf   100 GW

100 GW
Posts: 29879
Joined: Aug 17 2009 6:43am
Location: Phoenix, AZ, USA, Earth, Sol, Local Bubble, Orion Arm, Milky Way, Local Group
Contact:

Re: Test a battery pack. How can i easily create a high amp load?

Post by amberwolf » Mar 20 2020 6:21pm


kansas   1 mW

1 mW
Posts: 14
Joined: Nov 05 2018 7:58pm

Re: Test a battery pack. How can i easily create a high amp load?

Post by kansas » Mar 21 2020 7:10pm

Buy 4 50W 12V halogent bulbs, connect in series and you get 200W 48V 5A load. Thats how I test my batt.
[/quote]
Awesome! I will try this :) It will be a cheap test. Thanks.
So the resistance over one 12v, 50w halogen bulb is really low?
Something like 2.5 ohms (2.5x4=10 ohms)?

I=48v/10ohms=4.8A
[/quote]

Use of incandescent bulbs (including halogen) is a poor means of load testing if there is any need for measurement, like capacity testing. Filament resistance of an incandescent bulb varies extremely with filament temperature. When I tested one common automotive bulb (194), the resistance was about 5 ohms cold and 60 ohms hot, a factor of 12. Resistance measured cold with a meter is low. Resistance with power applied to the bulb rises with temperature, which may be roughly estimated by color. It is calculated by measuring current through the bulb and voltage across it and applying Ohm's Law. As voltage is raised, the filament gets hotter/brighter, resistance rises, and the resistance calculated thus should be close to that calculated from the rated wattage of the bulb at its rated operating voltage.

In the example given of a 12V 50W bulb, current (amps) is 50/12 = just over 4A. R is V/A = 12/4 = 3 ohms. Power is 12 x 4(and a tad) = 50 watts. At 6V, resistance might be 1.5 ohms, thus 6/1.5 = 4A; 6V x 4A = only 25W.

Connecting 4 50W bulbs in series will not result in a 200W load as stated above because the resistances are additive. Neither will connecting them in parallel, except when they are operated at rated voltage.

Use of suitable resistors will give much greater accuracy. Their resistance too will vary some with temperature, but if they are of suitable wattage, they will not get very hot and it will not vary much.

Feel free to check my arithmetic. I think youtube has better tutorials on Ohm's Law than I can provide.

markz   100 GW

100 GW
Posts: 9463
Joined: Jan 09 2014 11:38pm
Location: Alberta Canada

Re: Test a battery pack. How can i easily create a high amp load?

Post by markz » Mar 21 2020 8:10pm

Get some power resistors and put it in a cup of water to keep them ultra cool.

angusinalberta   1 mW

1 mW
Posts: 17
Joined: Jun 18 2018 8:57pm
Location: alberta

Re: Test a battery pack. How can i easily create a high amp load?

Post by angusinalberta » Mar 27 2020 9:56pm

An old electric kettle will do the job.
Mine is rated 1500 W on 120 V
Since power is proportional to V squared we can readily find the power at any other voltage.
For a 48 V battery, for example, the power will be
1500 W * 48^2 / 120^2 = 240 W
The current will be 240 W / 48 V = 5 A That's probably close to what you want.
There is a glitch of course. The kettle will have a thermal switch that shuts it off when it starts to boil. You might want to disable the switch and then be _very_ careful to keep the kettle topped up. Otherwise you might fry your kettle. (or burn down your house)

Post Reply