Can I connect two dc step down converters in series?

[rg12]

Hey Dudes,

I need to get my 67v pack to around 12v for a few different appliances.

All the buck modules are for around 30v to 40v max input.

I found only one that is for 100v but he doesn't ship internationally and also it's about $10 per unit which is not cheap (compare to the $0.75 the regular one costs).

Is there a way to take two let's say 40v (input) step down modules and connect the 67v pack in series to the two converters and have the 67v spread evenly on them to input 33-34v on each?

 

[MrDude_1]

I have even better news for you.
Go find a common 120v AC wall wart or power brick that puts out 12v DC. one of the lightweight ones that does not have a large transformer inside.
Connect your battery to its wall power prongs and check if it works. Most do, some dont.

They're all switching power supplies, and they will work in your 16s or higher lipo pack. Best part is they're cheap. You probably have one in the house already.
I use one that used to power my netbook. Its rated for 12vdc / 3a and easily runs my lights. The only downside is there is a 1.5 second delay between when I turn the bike on, and it kicks on... the caps take longer to charge because of the lower voltage. The one I use will work down to 55v. It wont turn on at 54.5v. I have others that need atleast 50v, and one that needs 70 or higher.

This all works because the first step of these power supplies is to rectify the power from AC to DC... so feeding DC doesnt hurt anything.
Then, because 12v is less than half of the input voltage, they still work as intended.

 

[rg12]

I need to check if I have one, but I live in a country where the AC voltage is 220v so maybe it will require double the minimum voltage to work?

I still prefer those little buck converters as they are smaller (pretty flat), very cheap (can't beat $0.75) and I will need a few of those so...

 

[MrDude_1]

I need to check if I have one, but I live in a country where the AC voltage is 220v so maybe it will require double the minimum voltage to work?

I still prefer those little buck converters as they are smaller (pretty flat), very cheap (can't beat $0.75) and I will need a few of those so...

Put your location in your profile. https://endless-sphere.com/forums/ucp.php?i=profile&mode=profile_info
That way we can tell where you are.. :lol:
even with 220v converters, it still works. not the one I use on the bike, but one of the ones I have is universal input...

as far as two buck converters with the input in series... that wont work you'll end up frying them. sorry.

another option if you dont have high amperage requirements is something like this: https://www.digikey.com/product-detail/en/recom-power/R-78HB5.0-0.5/945-1061-ND/2256241
I use one connected to the CA power plug to run my bluetooth serial output. They make them at different output voltages... just search digikey. However they are all limited to less than 1 amp.
If you need big power, a proper switched power supply is the best way to go... they're cheap, but they are not sold as listed for this application, so they're hard to find

 

[rg12]

Thanks alot, will search dgkey/ebay although I prefer to look for a module since those chips are fixed voltages and I need variable voltage...

Can I use maybe resistors in front of the converter or just resistors alone to make the voltage drop? (sorry if I sound stupid)...

EDIT: Found this https://vod.ebay.com/vod/FetchOrderDetails?ViewPaymentStatus&purchaseOrderId=658575638015
80V! that's great, this will work with 16s pack but I need also for a 20s pack (84v fully charged), do you think this 80v thingy will tolerate 84v?

 

[Mundo]

I recently bought this, works good.

DC-DC VOLTAGE REDUCER CONVERTER FROM 84V 72V 60V 48V 36V (30V-100V) TO 12V 240W 20Amax


https://www.amazon.com/gp/product/B00M6NWVTM/ref=od_aui_detailpages00?ie=UTF8&psc=1

 

[rg12]

Thats too big for my use (don't need high amperage/wattage) and it's a bit expensive...
but thanks, i did notice them on ebay...

 

[MrDude_1]

Thanks alot, will search dgkey/ebay although I prefer to look for a module since those chips are fixed voltages and I need variable voltage...

Can I use maybe resistors in front of the converter or just resistors alone to make the voltage drop? (sorry if I sound stupid)...

EDIT: Found this https://vod.ebay.com/vod/FetchOrderDetails?ViewPaymentStatus&purchaseOrderId=658575638015
80V! that's great, this will work with 16s pack but I need also for a 20s pack (84v fully charged), do you think this 80v thingy will tolerate 84v?

that link is only good for the buyer/seller.. can you post the link to the ebay auction?

 

[rg12]

Thanks alot, will search dgkey/ebay although I prefer to look for a module since those chips are fixed voltages and I need variable voltage...

Can I use maybe resistors in front of the converter or just resistors alone to make the voltage drop? (sorry if I sound stupid)...

EDIT: Found this https://vod.ebay.com/vod/FetchOrderDetails?ViewPaymentStatus&purchaseOrderId=658575638015
80V! that's great, this will work with 16s pack but I need also for a 20s pack (84v fully charged), do you think this 80v thingy will tolerate 84v?

that link is only good for the buyer/seller.. can you post the link to the ebay auction?

Oh sorry...
http://www.ebay.com/itm/152219552860

Also ordered that:
http://www.ebay.com/itm/26253345988...49&var=561382774158&ssPageName=STRK:MEBIDX:IT
as MrRude_1 suggested