Buck-Boost converter 12V battery to 13.8V 5A?

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augustinetez

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After the mention of these 5A DC-DC XL4005 adjustable step-down module in another thread, has anybody seen a 5A rated Buck/Boost converter outputting 13.8V?

Input would be a 12v battery (and possibly attached charger), so input volts would be in the range of ~10v - 16V.

Usage is for low power portable transceiver if they weren't overly noisy/easily suppressed.
 
To do that you would obviously need a step-up/step-down module, as you need to do both.

Exactly what are you trying to do?, the mention of 13.8V looks like you've seen the nominal voltage of a lead acid 12V battery and are wanting to maintain that for some reason?. A low power transceiver should be designed to work from the battery 'as is', no need to do anything - just connect it to the car battery.
 
Something like this is about as near as you will get in an all-in-one unit.

That can take vehicle 12V in and give stabilised 12V, 15V or various other voltages out.

100W 12-24V UNIVERSAL NOTEBOOK LAPTOP CAR CHARGER AC POWER SUPPLY ADAPTER BLACK | eBay

Power: 100W. 1 x Laptop Power Adapter. Adapter Size: 20cm x 10cm/7.87" x 3.94" (Approx.). Due to the light and screen setting difference, the item's color may be slightly different from the pictures.
www.ebay.co.uk
 

Some older stuff, while yes, designed to used "in a car", was not designed to used on top of a mountain where there are no cars - possible use #1 - I'm assuming you've heard of SOTA operation?

Other stuff is designed to be battery powered, but falls miserably short with just a small drop in battery voltage - possible use #2.

#3 - why do I need a reason, other than just out of curiosity?

There are several circuits for DIY jobs in QST/QEX/CQ magazines etc and I was curious as to whether there were any cheap modules around already built.
 

If your power requirement actually that high?, or would lower be OK - if so cheap modules are available:

3pcs DC-DC Boost Buck Adjustable Step Up Step Down Automatic Converter XL6009 Module Suitable For Solar Panel

Only US$4.99, buy best 3pcs dc-dc boost buck adjustable step up step down automatic converter xl6009 module suitable for solar panel sale online store at wholesale price.
www.banggood.com

You're considerably limited by your requirement for step up and step down.

One easy option would be to step UP (to say 18V) then step DOWN from there to 13.8V - but that's essentially what the step up/down converters are doing anyway.

Here's a 5A step up:

LM2587 DC DC Boost Converter 5A 3-30V Step Up to 4-35V Power Supply Module

Only US$7.99, buy best lm2587 dc dc boost converter 5a 3-30v step up to 4-35v power supply module sale online store at wholesale price.
www.banggood.com

And a 5A step down:

Geekcreit® 5A XL4005 DC-DC Adjustable Step Down Module Power Supply Converter

Only US$1.39, buy best geekcreit® 5a xl4005 dc-dc adjustable step down module power supply converter sale online store at wholesale price.
www.banggood.com
 
Most low power rigs would get away with 2-3A, I prefer to be a little cautious and leave a little headroom 'just in case'.

A trawl through Ebay and the likes throws up plenty of 3A ones like your first one and I did come across a 5A one but it needed an input voltage of min 15V to supply the current and voltage, so kinda defeats the purpose.
 

As I've repeatedly told you, your requirement needs BOTH a step-up and a step-down, either a single module, or (as it more likely for 5A) a pair of modules. You can't step down from a car battery to maintain 13.8V.
 
A portable transceiver will probably get lots of hash noise from any buck/boost converter, they are all switching power supplies. From what I've seen, most portable transceivers (ie 5W to 10W) will operate ok down to about 11V, so a regular battery will do as-is. Put on a small solar charger if you want to maintain the voltage a bit longer...
 
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