Home Made Voltage Booster charges TT battery off 7-pin

LittleBill wrote:

eb145 wrote:


The little voltage boosters are designed for laptop power supplies that can plug into 12V cigar lighter outlets in cars. They are designed as constant voltage output (variable voltage). With no apparent limit to the current. They will burn out quickly if allowed to pass lots of current - thus the fan to cool them in the summertime. Max power is 150W per device.



Ed

Not really sure what you mean by there is no limit to current . right in the listing it says 6 amp. of course they have no limit but you better push some serious airflow if you expect them to last


" DC-DC 150W Boost Converter 6A 10-32V to 12-35V Step-Up Voltage Power Supply"

fan would do alot better also if you actually had it aimed over the heatsinks

This is closer to what I got - 16Amps input max, 10 Amps output max:
150W DC-DC boost step up converter

"You can use it to power all your electronic devices, as long as the rated input voltage and rated input current is not exceeded."
I see they cost $11.99 now.

What I meant to say is that there seems to be no over-current protection for these little things. There is a limit on the specifications, but there seems to be no current-limiting control (other than letting the smoke out).

For the airflow I am going to cut out some plastic baffles to force all the air to flow over the voltage converters and their heatsinks. I don't know if you can tell by the pictures, but the air is drawn in by the fan, blows under the wood block and exits the other side. Plastic and duct tape baffles will force all air to exit where I want it to. When I did my initial testing on this, temperature was in the low 40s (F) so cooling wasn't so critical. In July, cooling will be a big deal.

Ed

I personally think you are just creating a parasitic load that adds nothing to your batteries. If you measure the actual current going into the batteries, I bet you find it higher without your device. Having said that, if you were to put a dc-dc switching power supply at the front of the truck and upped it to 72 volts and then another one at the rv to drop it back to 14+ volts, then you have done something.

eb145 wrote:


The little voltage boosters are designed for laptop power supplies that can plug into 12V cigar lighter outlets in cars. They are designed as constant voltage output (variable voltage). With no apparent limit to the current. They will burn out quickly if allowed to pass lots of current - thus the fan to cool them in the summertime. Max power is 150W per device.



Ed

Not really sure what you mean by there is no limit to current . right in the listing it says 6 amp. of course they have no limit but you better push some serious airflow if you expect them to last


" DC-DC 150W Boost Converter 6A 10-32V to 12-35V Step-Up Voltage Power Supply"

fan would do alot better also if you actually had it aimed over the heatsinks

drsteve wrote:

RoyB wrote:
What do you do when the battery gets hit with your 14 PLUS VDC and wants to draw around 20AMPS of DC current. There may not be that much DC current available in your 7-way connector wiring.

I wondered that myself.

To the OP, have you used it yet to see how well it charges your batteries?

Short driveway testing only so far. In 40%F weather.

My initial testing showed 20+ Amps to my pair of Group 24 Marine batteries when I dropped them to about 75% SOC. In fact, they were cranking too much current when they were both running in parallel and I set the output voltage high (14.8V) and blew a fuse in my truck. I need to lower the voltage output to reduce the current draw on the truck.

The little voltage boosters are designed for laptop power supplies that can plug into 12V cigar lighter outlets in cars. They are designed as constant voltage output (variable voltage). With no apparent limit to the current. They will burn out quickly if allowed to pass lots of current - thus the fan to cool them in the summertime. Max power is 150W per device.

Other things to do for testing/refining/playing:

1. reduce output voltage to reduce current draw from truck 7-pin. I'll probably try 13.6V when camping to see how that goes.

2. bring lots of fuses for the truck so I can have fun experimenting with this when camping :-)

3. hook up jumber cables from truck alternator to input side of these converters eliminating the 7-pin from the circuit. Then I have to worry about letting the smoke out of these voltage boosters with too much current / power.

rough power estimates below:

150W x 2 voltage boosters = 300 Watts max power before component failure and smoke let out. When current is flowing, the 7-pin will have reduced voltage due to the high current.

Output (charging side): 300W/14V = 21.4Amps

If Input side (7-pin) is @12V: 300W/12V = 25 Amps
If Input side (7-pin) is @11V: 300W/11V = 27.2 Amps
If Input side (jumper cables) @13V, 300W/13V = 23.1 Amp

EDIT: I did the testing a month or two ago. And actually, now that I think about it, the truck fuse would blow only when I had both voltage boosters operating. With only one wired in I would get half the amps and it wouldn't blow the truck fuse. And what is disturbing is I just found this:
Dodge Trailer Battery Charging Wire

where someone states Dodge uses 14 gauge wiring for the trailer battery charge wire! While Ford and Chevy use 10 gauge. 15 Amp max on 14 gauge wire.

It looks like I'll use jumper cables to power this thing or use just a single booster and drop the voltage to keep the current under 15 Amps from the 7-pin.

Ed

RoyB wrote:
What do you do when the battery gets hit with your 14 PLUS VDC and wants to draw around 20AMPS of DC current. There may not be that much DC current available in your 7-way connector wiring.

I wondered that myself.

To the OP, have you used it yet to see how well it charges your batteries?

What do you do when the battery gets hit with your 14 PLUS VDC and wants to draw around 20AMPS of DC current. There may not be that much DC current available in your 7-way connector wiring.

I have found Unless you can provide 14.4VDC at around 15-20AMPS of DC Current when charging a 50% discharged state 12VDC deep cycle battery it will take many many hours to recharge the battery. If you have the higher DC current available to use when you apply 14.4VDC it will then charge your deep cycle battery from a 50% charge state to a 90% charge state in three hours time.

This is deep cycle battery science at play.
Just saying...

Roy Ken

Fishinghat wrote:
Pretty impressive! Thanks for sharing.

X2! Great work!

Measure the output under load (batteries connected).

Pretty impressive! Thanks for sharing.