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# DC Voltage Booster

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#### ketchumwt

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Hi! I need help designing a circuit to boost a 12V DC source...a vehicle battery from 12V DC to 13.8 to 14.5 volts DC to charge an RV battery.

Problem: Current charging circuit = 40' of #12 cu. 20' in length and 40' of #8 cu. 20' in length. Voltage drop through this circuit is too great to allow adequate charging of RV battery at end of line.

Specs:
Input Voltage 11 to 12v DC
Ouput Voltage 13.8 to 14.5v DC
Charge Rate minimum = 10 amps/hour but would like 20 to 30 amps/hour is possible.

Any help would be appreciated.

Thanks, Bill K

use a dc-dc converter (switch mode boost)

if ripple is too high connect external inductance to cct
interactive power electronics online text (i discovered it 3 months ago during university semester when i was studying a course power electronics and drives). even details microcontroller implementation!

RV Charge Circuit

Hello, I realize this is quite an old post, but where you able to solve this issue. If so, do you have a complete diagram of your RV charging system that could be made available?

Thank You!

I doubt he'll be back after five years.

Using thicker cable will probably work out cheaper than adding a boost converter.

Why would you boost the voltage instead of connecting a battery charger to the RV battery directly? The wire guage you specified is the same as that used on booster cables and industrial rapid chargers.

Hello, I realize this is quite an old post, but where you able to solve this issue. If so, do you have a complete diagram of your RV charging system that could be made available?
I built something similar a few years ago. I've attached the diagram and PIC source code. It has worked flawlessly for around 4yrs and we go camping often. It can supply a max current of 15A at 14.2V to the battery with apx 12V input after wiring voltage drops. If you decide to build it, I can supply more details about the coil, etc.
The reason I went this way, rather than use thick cables, was that I wanted to use the standard trailer connection to my camper and not have to unbolt #0 cables every time I wanted the camper off the truck. If you unbolt heavy cables connected to a battery enough times you'll eventually weld them to something grounded like the truck box!

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vboost

Hello,
I am interested in doing your project vboost "to improve the battery charging services in the camper, in practice I would put it between the alternator and battery.
Thank you.

It is designed to go between the vehicle battery/charging system and the RV battery. The vehicle alternator charges the vehicle battery and also supplies current for Vboost. You cannot drive it with just the alternator alone which would be redundant anyway since the alternator can output more than 18V on it's own.

I built something similar a few years ago. I've attached the diagram and PIC source code. It has worked flawlessly for around 4yrs and we go camping often. It can supply a max current of 15A at 14.2V to the battery with apx 12V input after wiring voltage drops. If you decide to build it, I can supply more details about the coil, etc.
The reason I went this way, rather than use thick cables, was that I wanted to use the standard trailer connection to my camper and not have to unbolt #0 cables every time I wanted the camper off the truck. If you unbolt heavy cables connected to a battery enough times you'll eventually weld them to something grounded like the truck box!

Now had I been here I would have just said use heavier gauge wire and a set of standard issue welder lead connectors like the smart RV'ers, truckers, contractors,and farmers do!

But I wasn't so oh well.

I explained why I didn't want to use heavy cables.
The reason I went this way, rather than use thick cables, was that I wanted to use the standard trailer connection to my camper and not have to unbolt #0 cables every time I wanted the camper off the truck. If you unbolt heavy cables connected to a battery enough times you'll eventually weld them to something grounded like the truck box!

Last edited:
I caught that well enough but welding lead connectors I was referring to are the quick connector type. Push together and give a half twist!

When I worked at the welding center we sold sets of them whenever there was a big RV'er crowd in town. If one person had a set at the camp ground it seemed like others would find out that it solved the trailer charging problems associated with the undersized wire in the factory harnesses.

We usually sold them a set of black and red in line twist lick type (Lenco LC-10) for the 4 ga 100 amp leads. However a few would mount the socket type connectors right into the vehicle and only have a set of pigtail leads from the trailer to the tow vehicle (trucker style).
Very clean and professional looking. Plus they handle far more power with much less chances of melting a harness line.
Farmers and contractors will often set up their vehicles with a set of sockets up front near their battery. Then have a set of jumper cables with the quick connect ends on them.
It makes jump starting much faster and easier plus a set of jumper cables with only one clamping end dont get borrowed only to never return!

Its just one option.

Hello,
I have to do is to mate with the vboost the battery start the service when the generator delivers.
Your project is just what I need just that I lack information sull'induttanza.
Thank you.

alternator -> engine battery -> vboost -> battery service

There have been several amateur radio articles on boosters such as you describe. The purpose for these is to boost 12 volt battery voltage that is further depressed by voltage drops, to the nominal 13.8 vdc that a transmitter could use. There is at least one commercial product made for this purpose and it would seem that it's easily adapted for your use. Sorry I can't forward a link or attachment.

Draft Kchriste turns the alternator charging real charger with boost phase (14.2 V) and maintenance phase to 13.2 V. is a great project to par with commercial ones like:

**broken link removed** 20SCHEDA%% 2030% 20A.pdf

The charging system of the engine battery is only for recharging the battery of the motor that is not subject to deep discharge (to the max is at 90%). That service, however, when it is profoundly low (less than 50%) can not be recharged with the only constant voltage of the alternator but needs at least two phases.

I ask forgiveness for my English is very rusty.

I am very interested in building up this project of yours. I would appreciate it if you could supply me with a more info the coil design, ferrite details(manufacturer and part no), wire guage and number of turns. On your schematic what do you connect your Chrg input to as you already have a battery connection?

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