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16-20 Varying Voltage DC Input to Regulated 12-13.5 DC Buck Converter/Regulators

outhouseengineering

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Jan 23, 2021
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Good morning. Somewhat a digression from the systems themselves but here in New England it is cold working outside many days in the winter months. I am looking to utilize the multiple 20 & 18 volt power tool batteries in hand to power my 12 volt, 85 watt motorcycle heated jacket liner. To date, there doesn't seem to be manufactured battery packs that will handle this load for at least 6-8 hours. Yes, there are many lower wattage 12 volt clothing lines, which do not have as much resistive heat designed in them and will allow a longer run time, but at a significantly reduced heat output. And the battery packs from my clothing line are in the neighborhood of $ 250 and then comes the need for a matched controller and remote at additional cost.
I am thinking of how to utilize a DC-DC chopper (Buck Converter) to achieve a reasonable wattage output at a regulated 12-13.5 volts. Given the power tool batteries are either 20 volts or 18 volts, depending on brand, and have ampere hour ratings between 5 & 6 ampere hours, I am assuming I can pull close to an hour of full 85 watt draw from the 18 volt/6 ah power tool battery if using one of these DC-DC voltage reducing converters and expecting some losses due to transformation inefficiencies. My math - ( Jacket: 12 volts X 7 amps = 84 watts) (Battery Draw: 84 watts / 18 volts = 4.7 amps) (Duration of Power Draw: 6 ah rated battery / 4.7 amps = 1.28 hours) Seeing as I normally run the jacket at a lower (medium) heat, which has the controller basically turning on & off the power at varying intervals, I am thinking I will probably squeeze a bit more time from a battery. And when the power of one battery is depleted, I simply swap it out for another.
So given the approach, and my limited research online of DC-DC converters, I am seeking any experienced feedback on these DC-DC converters, which seem fairly inexpensive, as to whether I can utilize one of these and more specifically what the input voltage specification should be. I am totally confused as to whether one rated at 48 or 24 volt input needs to have a continuously regulated 48 volts DC, or regulated 24 volts DC, for the input or if my input voltage could fluctuate as will be the case with the discharging and decreasing voltage of my input voltage source. And if the input voltage can have a fluctuating range, within reason, does that in turn affect the output voltage? I will note that I have considered the likelihood that at some point the supply battery will either discharge to an inoperable level, or in the case of these lithium power tool batteries, just shut off when they fall below a set point. I do realize that at some point in reduced supply voltage, I can not expect an operable load supply voltage. This may also assist others in different applications as well.
Thanks for any thoughts.
 
I have deleted your other thread. Duplicate posting is not permitted.

Welcome to the forum.

There are many wide range input XV to 12VDC converters. The concern is that you would need to monitor the lithium packs to ensure they do not over-discharge.


In one place, this one accepts 18-33V If your 20V/18V batteries operate above 18V and 18V is a safe cut-off, i.e., the converter will stop outputting 12V once the input voltage drops below 18V.

In another place:

Specifications:
Input voltage: 24V DC
Input range: 12-40V DC
Output voltage: 12V DC
Output current: 20A (Max) / 240W
Case material: die-cast aluminum
Potting material: epoxy sealed

Features:
Brand new and high quality
Industry grade DC 24V to 12V step-down converter
More than 90% power conversion efficiency
Built-in over/under voltage input, overload, overhead, and short circuit full protection
Used in vehicles, security systems, telecommunications, medical equipments, instruments etc
100% waterproof & anti-shock protection
Ultra compact size, light weight
Auto-recovery when device is back to normal operating
Stable and reliable performance
Simple to install

This might get you there. You'd need to find the actual cut off (12 or 18V) and see if that works for your batteries.
 
Check specs on your heater systems. Many "12v" systems will run more voltage. All the tool systems are the same volts. Some call then 18v nominal. The rest call them 20v FSOC. But they are all the same 5s Li-Ion. While every tool manufacturer builds the same, nothing else in the world uses that voltage. So it can get interesting to use the batts outside of their ecosystem
 
I have deleted your other thread. Duplicate posting is not permitted.

Welcome to the forum.

There are many wide range input XV to 12VDC converters. The concern is that you would need to monitor the lithium packs to ensure they do not over-discharge.


In one place, this one accepts 18-33V If your 20V/18V batteries operate above 18V and 18V is a safe cut-off, i.e., the converter will stop outputting 12V once the input voltage drops below 18V.

In another place:

Specifications:
Input voltage: 24V DC
Input range: 12-40V DC
Output voltage: 12V DC
Output current: 20A (Max) / 240W
Case material: die-cast aluminum
Potting material: epoxy sealed

Features:
Brand new and high quality
Industry grade DC 24V to 12V step-down converter
More than 90% power conversion efficiency
Built-in over/under voltage input, overload, overhead, and short circuit full protection
Used in vehicles, security systems, telecommunications, medical equipments, instruments etc
100% waterproof & anti-shock protection
Ultra compact size, light weight
Auto-recovery when device is back to normal operating
Stable and reliable performance
Simple to install

This might get you there. You'd need to find the actual cut off (12 or 18V) and see if that works for your batteries.
Thanks Snoobles!! Just spent some time with those leads and pulled the trigger on a DC-DC Voltage Reducer Auto Buck-Boost Converter, which claims to accept an input voltage range of 8 volts to 40 volts and produce a DC output voltage of 13.8 with a maximum current of 10 amps. Cost: $ 32.00. A bit pricey but I liked the fact that it had a wider input voltage range, with an output voltage more in line with the normal operational voltage being supplied on my motorcycle (i.e. above 12 volts). There may be a downside, as I believe you may have also inferred, and that is the potential that the battery may draw down to a completely exhausted state and present issues with recharging. Would also note that this converter advertises a "Boost" feature as well, which I am thinking will come into play once the input voltage drops below 13.8. But I will bench test the set-up and monitor current draw and voltage at both input and output and carry test through to see what the results will likely be should I use the ol' "Set It & Forget" approach. Will post my findings and whether this contraption may have some merit.
Thanks again.
 
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