dc to dc convertor bridging multiple

Thread Starter

linkokie

Joined May 9, 2020
5
Hi!
wanting to buy 1500W 30A DC-DC Boost Converter 10-60V to 12-90V from aliexpress
is it possible to bridge the load side of converter to double output supply?

thanks!
 

LesJones

Joined Jan 8, 2017
2,642
I expect this unit is not isolated. The negative of the input will be common with the negative of the output. To bridge it you would need one unit that gave a positive output with respect to the common negative and the other unit would have to give a negative output with respect to the common negative. (I am assuming both units would be fed from the same supply that was positive with respect to the common negative.) The output of two of the units could be connected in series BUT ONLY IF THE INPUT TO THE TWO UNITS WAS FED FROM TWO SUPPLIES THAT WERE TOTALLY ISOLATED FROM EACH OTHER.

Les.
 

Thread Starter

linkokie

Joined May 9, 2020
5
I expect this unit is not isolated. The negative of the input will be common with the negative of the output. To bridge it you would need one unit that gave a positive output with respect to the common negative and the other unit would have to give a negative output with respect to the common negative. (I am assuming both units would be fed from the same supply that was positive with respect to the common negative.) The output of two of the units could be connected in series BUT ONLY IF THE INPUT TO THE TWO UNITS WAS FED FROM TWO SUPPLIES THAT WERE TOTALLY ISOLATED FROM EACH OTHER.

Les.
ah ok. yeh its not isolated. and it seems isolated dc converters cost way more $$$$ i guess this is not an option then. thanks
 

ronsimpson

Joined Oct 7, 2019
684
charge lithium batteries 24v. so around 30v at 40a
I should have asked where are you getting power?

Assume input is 12V and output is 24 to 30V.
There is little data on this supply. We know the input current should be less than 35A and the output less than 30A.
I do not know if the supply will limit its self to 35 & 30A!! Lets assume it has good current limits and can run for hours in current limit mode. (likely not true)
Vin = 12V @ 35A and Vout = 24V at 17A. (if supply is 100% efficient) input power (12 x 35) = output power - power lost to heat output power is (24 x 17.5).

You can parallel two supplies to get 17 x 2 amps out. Or parallel three supplies to get 17 x 2 to charge the battery.
Three supplies in parallel: The supplies are set to 30V, 29.9 and 29.8V. The battery voltage starts at 24V with all three supplies pushing current. At 29.801V supply-3 drops out and only two supplies are working. At 29.901 V the second supply stops and only one is charging. The at 30.01 the third supply will drop back to a small current. This is OK.

This type of supply has no current limit when Vout is less than Vin! If you connect to a battery that is damaged and is at 5V there is no mechanism to limit the current.
 
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