Using zener diode to reduce charge voltage

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calab   100 kW

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Using zener diode to reduce charge voltage

Post by calab » Jan 19 2022 2:20am

If I want to reduce the voltage on a 36v (42v) 6a charger do I parallel six 5.6v 5w zener diodes because each diode can handle 1.12a and that should be 6a?

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Chalo   100 GW

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Re: Using zener diode to reduce charge voltage

Post by Chalo » Jan 19 2022 2:22am

Use silicon power diodes that can tolerate higher current, if you can get the Vf value you want that way. Parallel diodes tend not to share current equally at all.

Be sure you have adequate heat sinking for the amount of power you're trying to dissipate.
Last edited by Chalo on Jan 19 2022 3:19am, edited 1 time in total.
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Re: Using zener diode to reduce charge voltage

Post by amberwolf » Jan 19 2022 2:28am

And also be aware that the voltage drop on a diode changes with the current thru it, and with temperature (not usually much, but it does). So as your charge current changes thru the charge cycle, so will the voltage dropped across the diodes.

You'll need to check the spec sheet for the specific diode you wish to use to see what it's specific drop will be under the specific conditions you'll have.

It may not be enough to affect your usage scenario, but if it is, you should be aware of it.
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AHicks   10 kW

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Re: Using zener diode to reduce charge voltage

Post by AHicks » Jan 19 2022 9:12am

Using a diode to lower the charge voltage works, but how are you going to shut this charge down accurately as the battery approaches full charge status?

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E-HP   1.21 GW

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Re: Using zener diode to reduce charge voltage

Post by E-HP » Jan 19 2022 10:52am

I assume the charger doesn't have the ability to adjust the output voltage? Is it one of those charging bricks?

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DogDipstick   100 kW

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Re: Using zener diode to reduce charge voltage

Post by DogDipstick » Jan 19 2022 12:07pm

Silicone controlled rectifier diode.

Such as this: https://www.newark.com/solid-state/50ri ... dp/07R9712
84v of Ironhorse XC.. :) :bolt: by Chevy :bolt: :D You call .. that.. a "glitch:" ? :twisted: (...No Mom. The formula is Kaw > 1(Hr) = Impounded. The math checks out. I'll be fine. ).. :? Broke20Horsies! 17,830w !! :x 1 (pound / second) Hp = 338.24 M^2 Kg^2 / Sec^4 ( :twisted: 1200v? :twisted: ) :| isn't 13" x 27".. Oh nvrmnd :roll: 4+25% = 5 ; 5-20% = 4... 5(1-20%) = 4.. so, to correct the incorrect reading, of 4 ... 4(1+25%) = 5 :confused: Fabricator @BSECo.

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Re: Using zener diode to reduce charge voltage

Post by 999zip999 » Jan 19 2022 4:10pm

if you need six of those at $13 each you want to just buy another charger that's adjustable for your needs and then you have another backup charger cuz 6 * 63 is what $84 I don't know it sounds like a lot of money

calab   100 kW

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Re: Using zener diode to reduce charge voltage

Post by calab » Jan 20 2022 12:05am

It is just a cheap charging brick that you cant open and that is not adjustable. I already have a settable charger but I have two batteries and I just want to lose 4-6v to get the pack from empty to 37.5v (3.75v) when I get home I charge both batteries at the same time. The good battery with the good settable charger and let it charge slow to a voltage above storage voltage, the other battery is an older battery but I cant time it to charge an hour or two because I forget I just gave myself an idea https://www.walmart.com/c/kp/outlet-timers got a few around for christmas time. I thought it would be easy to buy 5 or 6 of those 5w 5.6v diodes in parallel to handle the 6a of the charge current, those diodes worked out to be 0.85a each not 1.xx that I typed but it does not work that way I just did the divide wrong.

I need one big zener diode that can handle 6a and 250w not my original plan. Charger on the left battery on the right, diodes are probably in the wrong direction or no because line on triangle is negative.
zener.jpeg
zener.jpeg (26.49 KiB) Viewed 256 times
999zip999 wrote:
Jan 19 2022 4:10pm
if you need six of those at $13 each you want to just buy another charger that's adjustable for your needs and then you have another backup charger cuz 6 * 63 is what $84 I don't know it sounds like a lot of money

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DogDipstick   100 kW

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Re: Using zener diode to reduce charge voltage

Post by DogDipstick » Jan 20 2022 9:20am

(doubleposted)
Last edited by DogDipstick on Jan 20 2022 9:22am, edited 1 time in total.
84v of Ironhorse XC.. :) :bolt: by Chevy :bolt: :D You call .. that.. a "glitch:" ? :twisted: (...No Mom. The formula is Kaw > 1(Hr) = Impounded. The math checks out. I'll be fine. ).. :? Broke20Horsies! 17,830w !! :x 1 (pound / second) Hp = 338.24 M^2 Kg^2 / Sec^4 ( :twisted: 1200v? :twisted: ) :| isn't 13" x 27".. Oh nvrmnd :roll: 4+25% = 5 ; 5-20% = 4... 5(1-20%) = 4.. so, to correct the incorrect reading, of 4 ... 4(1+25%) = 5 :confused: Fabricator @BSECo.

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DogDipstick   100 kW

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Re: Using zener diode to reduce charge voltage

Post by DogDipstick » Jan 20 2022 9:21am

The "line" on the diode just indicates polarity. Inline flow. I dont know about your picture, nothing is labeled. The flow indicates teh charger is on the (left), battery on the (right).

... kinda ambiguous diagramming.

999zip999 wrote:
Jan 19 2022 4:10pm
if you need six of those at $13 each you want to just buy another charger that's adjustable for your needs and then you have another backup charger cuz 6 * 63 is what $84 I don't know it sounds like a lot of money
you would only need one of those SCR diodes I linked . 13$, one time. Handles 50A and up to 800v. From the data:

Zip. Yea they dont " drop" much voltage. For this little level of power, maybe just a "voltage divider" with strong resistors is in order.
The 50RIA80 is a Medium Power Thyristor/Silicon Controlled Rectifier (SCR) intended for general purpose applications. The 50RIA series SCR is ideal for phase control in converters, lighting circuits, battery chargers, regulated power supplies and temperature/speed control circuits. It is a four-layer, unidirectional soli
84v of Ironhorse XC.. :) :bolt: by Chevy :bolt: :D You call .. that.. a "glitch:" ? :twisted: (...No Mom. The formula is Kaw > 1(Hr) = Impounded. The math checks out. I'll be fine. ).. :? Broke20Horsies! 17,830w !! :x 1 (pound / second) Hp = 338.24 M^2 Kg^2 / Sec^4 ( :twisted: 1200v? :twisted: ) :| isn't 13" x 27".. Oh nvrmnd :roll: 4+25% = 5 ; 5-20% = 4... 5(1-20%) = 4.. so, to correct the incorrect reading, of 4 ... 4(1+25%) = 5 :confused: Fabricator @BSECo.

john61ct   100 GW

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Re: Using zener diode to reduce charge voltage

Post by john61ct » Jan 20 2022 11:26am

Doesn't it rate up to 80A?

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