Dump Load Question

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Dump Load Question

Postby expresso » 24 Jan 2023, 20:41

I just received my Dump load 600Watt unit - it has two ends to connect the wires

i was told i can connect either end pos or neg.

is that correct ? it dosnt matter which end is pos or neg ?

its a resistor bank

https://windandsolar.com/diversion-dump-load-resistors/

on my older one that went dead - it has a pos and neg sign - if that mattered or not but it was there

this one has no signs or indication - they told me either end is fine -

how can i safely test it other than connecting it and see ?

thanks
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Re: Dump Load Question

Postby Burgerman » 24 Jan 2023, 21:16

Any way round. Same as the old one. Its a resistor. It neither cares or knows! Think of it as a long thin wire. Add a fan... Connect to the same terminals. Get a 24v one from amazon. It is 100 times better than a desk fan.

Measure height. If its 60mm or more fit 2 of these to the side. https://www.amazon.co.uk/GDSTIME-60mm-C ... B086SLQK5S

If its less fit smaller ones. Works a treat stays cool enough to pick up and hold. You also need to drill 60mm hole with a hole saw/drill. https://www.amazon.co.uk/Bi-Metal-Cutti ... B09WDSNWVR

Then it will not burn out like your previous one. And add some rubber feet... 1/2 inch https://www.amazon.co.uk/Medium-Rubber- ... B07VNQFV59
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Re: Dump Load Question

Postby expresso » 24 Jan 2023, 21:44

i can add some cushion stick on stuff on the bottom - i sit on a wood board - i place a fan near it and run it all the time the fan -

i guess i can add a 24 volt fan also - its a large unit - two would fit

i would have to add them on top of the unit - bottom is not exposed - cant fit fans on the sides - the ends - thats where the wire is connected - i can only place them on top of the unit - blowing in or out i guess - but in would be better i believe

the older unit had exposed coils which bent broken etc,

this unit is much better quality -

the old unit did have a Pos and Neg marking - where i connected the wires - that made me feel that its a certain way to connect it -

its not then - i will get a few 24 volts - also the screw size seems smaller than a m6 - i have to see - i have so many screws nuts etc, and i bet you not one of them will fit -
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Re: Dump Load Question

Postby Burgerman » 24 Jan 2023, 21:52

You want heat blowing across, not down. Fit them to the side.

Like I did. Just measure and order fans that fit.
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Re: Dump Load Question

Postby expresso » 24 Jan 2023, 21:53

https://www.amazon.com/WINSINN-Bearings ... =8-10&th=1

something like this ? should be OK ?

cut the ends off and connect extend the wire to both ends - i would just velcro the fans on top -

i found a few more 24V

the above link is a 2 pack - good price

https://www.amazon.com/Jamicon-JF0625B2 ... 08&sr=8-15


https://www.amazon.com/Wathai-60x60x25m ... r=8-3&th=1


first link is a 2 pack - least amount of money - should work the same as the others ?
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Re: Dump Load Question

Postby expresso » 24 Jan 2023, 21:56

Burgerman wrote:You want heat blowing across, not down. Fit them to the side.

Like I did. Just measure and order fans that fit.



ok i was thinking the ends - didnt think the side of the unit -

i can do that also - both on one side

would the first link be fine the 2 pack

i can extend both wires and connect them together in a ring like the balance wires - both pos wires of one fan in one ring terminal and black same way - they would just start working once a battery is connected to them ?
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Re: Dump Load Question

Postby Burgerman » 24 Jan 2023, 21:58

Like this.
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Re: Dump Load Question

Postby Burgerman » 24 Jan 2023, 22:04

Those are 24V fans. You connect all the reds together. And all the blacks together...
The resistor itself doesent care but the fans do.

Also you need to measure, see if those 60mm fans fit. If not order 50 or 3x 40mm. And a hole saw! They wont blow throgh the tiny holes. I had to dril mine out, 2x 60mm holes. Thats not done yet in the pics.
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Re: Dump Load Question

Postby expresso » 24 Jan 2023, 22:05

right - like yours - it shows the pos and neg marking

but it dosnt matter which side you connect them - why put the markings - makes me believe that it can be connected wrong -

that fan unit has one wire for both fans ?

would be nicer that way
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Re: Dump Load Question

Postby expresso » 24 Jan 2023, 22:06

Burgerman wrote:Those are 24V fans. You connect all the reds together. And all the blacks together...
The resistor itself doesent care but the fans do.

Also you need to measure, see if those 60mm fans fit. If not order 50 or 3x 40mm. And a hole saw! They wont blow throgh the tiny holes. I had to dril mine out, 2x 60mm holes. Thats not done yet in the pics.



measure i can do - and get the right size length etc, now the drilling part - thats another story - so you cut the whole side of the unit where the fans are mounted ?
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Re: Dump Load Question

Postby Burgerman » 24 Jan 2023, 22:08

Theres only so many different ways I can tell you IT DOESENT MATTER WHICH WAY YOU CONNECT A RESISTOR...

The fans on mine are 12V and connected in series. From an old memory cooler. The fans I linked to are 24V chosen so you dont need to think about that stuff. Just use 24V fans. In parallel. And drill a hole with hole saw behind them, correct size.

Look at the links above. I linked to a hole saw. Makes light work of drilling a 60mm hole, if you use 60mm fans.
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Re: Dump Load Question

Postby expresso » 24 Jan 2023, 22:13

dont see any link to saw - but its fine - dosnt matter - i have a fan i can just run it inches away if i have to

24 fans are fine - i can get two and try it on the side

making holes is another story - i try it without cutting anything up first - or dont have to use a fan at all really - will get hot though

i see the link - i dont need to get that drastic - more tools i will never use - i already have way too much stuff thanks - i may consider it or use a dremal to cut a hole the size of the fan i install ?
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Re: Dump Load Question

Postby Burgerman » 24 Jan 2023, 22:17

If you want it reliable and cool enough to leave doing is thing, safely you must use a fan. Resistors trying to dump 600 watts without get super hot and burn out or go brown and start to come apart otherwise. And no a deskfan is not adequate!

But why not do it properly?
Another thing. When a 600 watt resistor is dumping 600 watts it tries to get super hot. Thats a lot of energy to dump. But as temp rises resistance increases. Which means your battery discharge slows down too. So cooling it well means you discharge your batteries faster. And everything stays much cooler. Except the room! Lots of warm air.

Hole saw link copied from above...
https://www.amazon.co.uk/Bi-Metal-Cutti ... B09WDSNWVR
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Re: Dump Load Question

Postby Burgerman » 24 Jan 2023, 22:23

You can do it with a dremmel, I did. Takes lots of time that way though.
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Re: Dump Load Question

Postby expresso » 24 Jan 2023, 22:31

its a cheap item cost wise - i could get it and never use it again - it will fit any drill ?

i have a drill - if one of my girls says she can do it - i may try - if not - i just run a fan as i did before and face it in the front to flow thru and call it a day - its not like i am using this thing all the time - i think i used the other one a half dozen times in many many years -

i just like to have it for when i need to - can discharge my pack in 8 hours - instead of 4 or 5 days nonstop with the pl 8 so its useful to have a way to discharge faster at 25A is not that fast either but a good enough rate -
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Re: Dump Load Question

Postby Burgerman » 25 Jan 2023, 04:23

Mines 40A roughly, so almost twice as fast, around 1000W. Warms the room nicely.
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Re: Dump Load Question

Postby shirley_hkg » 25 Jan 2023, 10:34

I use PL8 to measure the capacity of a battery and also note the pack's voltage relative to the DOD, in order to get reference for riding.

Always dump to another empty battery , which has BMS .

Would like to know what would PL8 do , when the pack's BMS cuts it off or the power lines were pulled off accidentally ?

May damage PL8 or not ?

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Re: Dump Load Question

Postby Burgerman » 25 Jan 2023, 13:45

I think no damage, 99% garanteed. Its well designed compared to other hobby chargers regarding protection. Cant garantee that though.

But I would allow the SUPPLY tab settings in the PL8 to set a safer max voltage and not use an unsafe on/off bms mosfet for that. As it will then reduce discharge power gradually. And when it reaches YOUR SET safe max voltage, will revert to 100w discharge internally automatically. Set to maybe 28.0V? max on the supply tab.
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Re: Dump Load Question

Postby shirley_hkg » 25 Jan 2023, 15:39

I always did it at 27.6V but things just happen.

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Re: Dump Load Question

Postby Burgerman » 25 Jan 2023, 23:19

In the west its called shit.

Shit Happens...


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