DC Step Down

General Discussion about electric bicycles.
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PlanetDad   100 mW

100 mW
Posts: 46
Joined: Mar 22 2019 2:11pm

DC Step Down

Post by PlanetDad » Apr 08 2021 11:38am

Greetings Everyone.

Currently finishing up my new build, and while doing some bench testing before final fit and wiring I ran into some things that concern me.

After disconnecting the battery and re connecting the display showing remaining battery will drop by 10% overall took the pack from 68% to 38% when I finally noticed. Is this a issue?

Also, when the DC step down was connected and I turned the key to power it on. My battery voltage dropped to 0% instantly. With only one small LED attached to show it had power.

Everything is tinned and wired correctly. But too worried to try and re connect. Should I be worried?

Thanks

100a sabvoton controller SVMC72100 48-72V
5000W QS Motor
20s7P 72v 24.5ah pack

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markz   100 GW

100 GW
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Location: Alberta Canada

Re: DC Step Down

Post by markz » Apr 08 2021 2:07pm

Its short circuited

Remaining battery voltages is very hard to measure, then you pu tinto the mix cheap displays.

Display is erratic, thats why you take a digital multi meter and measure to confirm 0V.

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amberwolf   100 GW

100 GW
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Re: DC Step Down

Post by amberwolf » Apr 08 2021 9:28pm

HOpefully you will reply to this thread, unlike a number of your other threads, so that we can help you with your project, or at least know that you have corrected the problem (and what the problem was), and that we weren't just wasting our time trying to help.
PlanetDad wrote:
Apr 08 2021 11:38am

After disconnecting the battery and re connecting the display showing remaining battery will drop by 10% overall took the pack from 68% to 38% when I finally noticed. Is this a issue?

Also, when the DC step down was connected and I turned the key to power it on. My battery voltage dropped to 0% instantly. With only one small LED attached to show it had power.

Everything is tinned and wired correctly. But too worried to try and re connect. Should I be worried?

Thanks

100a sabvoton controller SVMC72100 48-72V
5000W QS Motor
20s7P 72v 24.5ah pack
You don't mention what you are using to see the battery voltage, or what format the display shows the voltage in.

If it is actually showing you a voltage, then stating those voltages, along with the starting voltage of the pack, would be helpful.

If it is only showing a percentage of full charge, you would need to know what that particular display uses for "full" and "empty" to know if there is a problem or not. (You can use a voltmeter on the 200vdc range to get every measurement along with that display, so you then know what they are, if the display does not provide this info)

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