Wiring for boost/buck converter

[Kristalsdreamtrip]

Does anyone know how to wire in a boost/buck converter, a boost converter and a small 12v fan for them? I have a picture of them together but I cannot see the exact wiring. A drawing or schematic would be great, showing the relation to the wiring to my compressor fridge and my control panel. I'm trying to stabilize the power from my solar charge controller and battery pack because I'm getting a full 14.4v from my batteries but my fridge is still shutting down before morning. I have 96ah of lifepo4 batteries. Also I installed/added my second 250w solar panel to my van roof. I haven't tried to plug it into my system yet so I'm still just using 250w. I only have a BougeRV 30Amp 12V PWM Solar Charge Controller but it seems to charge the batteries well. I just have no idea where to wire these parts in.
https://www.dropbox.com/s/n75wlhnfrryzke7/boostbuckfan.png?dl=0
https://www.dropbox.com/s/n75wlhnfrryzke7/boostbuckfan.png?dl=0

 

[tx2sturgis]

Does anyone know how to wire in a boost/buck converter, a boost converter and a small 12v fan for them?

Buck and/or boost converters typically have 2 input wires or terminals (positive and negative) and 2 output wires or terminals...  or sometimes they have a common negative wire and positive input and positive output wires. Pretty simple.

But...if your fridge is unhappy with low voltage, some of them can be set to a lower LVD (low voltage disconnect or low voltage battery protection, etc)

Check your instructions for that first. Maybe the LVD is set for 12.5v, lets say, and if it can be set for 11.5v that might get you thru the night.

Keep in mind that nothing in electronics is free. For a voltage boost function to work, the converter pulls more current and then uses that in it's power conversion to a higher voltage. This means that if your batteries are sagging by morning, they may sag even earlier with the boost converter, if the batteries are not up to the task at hand.

Lots of 'ifs'...

Consider a buck or boost converter as a 'band-aid' in this situation...it might actually work for you....or it might not.

Good luck.

 

[jonyjoe303]

On the one I built it had toggle switches and an led meter which you dont need and makes it look more complicated then it really is. All you need is an input connector and an output connecter, I use the xt60 connectors but you can use the cigarette type plug if that what your fridge uses.

You will need a multimeter to measure output voltage on the boost converter ( adjust to 19 volts) , the current adjust you can just turn clockwise several turns to max it out.
Unplug everything before you connect the boost output to the buck input. Then you can adjust the buck output with the multimeter to 13.2 volts. Also max out the current adjust. There are youtube videos that will show you how to make these adjustments if your unsure including how to adjust the current with a multimeter. The current you can just max out (no multimeter needed) since fridge will only use about 6 amps. 

The fan you can connect on the input side of the boost. On my fan I used a small buck converter to reduce the fan speed, at full speed the small fan make alot of noise. But thats something you can do later.

The boost  buck as long as its properly configure and your battery has amps available should fix your problem. I have had mine connected 24/7 to my fridge almost 9 months and fridge hasnt shutdown once. I also tried the fridge low/med/high switch but that didnt fix the problem. Powering the fridge seems to be easy duty for the boost buck converter and the small 40mm fan keeps it cool even having the fan rpm at half speed.

 

[Tom_M]

If your fridge is shutting down because of low voltage you may be doing some major harm to your batteries if you don't have a BMS (Battery Management System). If you do have a BMS your batteries are disconnecting, which is a good thing. You probably need more battery power.

 

[MotorVation]

You don't mention how your fridge is wired to your "control panel." If you're using a cigarette plug adapter from the fridge, it causes voltage drop. I cut my plug off and have the fridge wired directly to my batteries with ring terminals. I've never had the fridge shut down to low voltage. I do still have some voltage drop but it's not nearly as bad as it was

 

[Kristalsdreamtrip]

I am using the cig lighter while driving during the day then switch to the cig lighter on my panel when not driving. it runs and freezes everything during the day while driving perfectly. When I switch to my panel, I set fridge to eco mode.

 

[Kristalsdreamtrip]

This is the only tech pages from my manual for fridge and my wiring since I stripped it down to only support my fridge. The tape u see is just temp to be safe, the wiring is temp, the batteries and wires will come from behind the board and thru the board.
https://www.dropbox.com/s/yvpyy16hoeierm1/strippeddownwiring1.jpg?dl=0

https://www.dropbox.com/s/70q4gnzytw6e4u5/stripeddownwiring2.jpg?dl=0

https://www.dropbox.com/s/rxd8bn0odyny25j/fridgemanual1.jpg?dl=0

https://www.dropbox.com/s/on7yywyyag3ar7y/fridgemanual2.jpg?dl=0

https://www.dropbox.com/s/kz88n73j5s41ghf/fridgemanual3.jpg?dl=0

 

[Kristalsdreamtrip]

I'll be on my way soon to see texas2stugis so I'll just wait on the boost/buck converter

 

[jimindenver]

Wait

250 watt panels on a PWM controller?

30 amps is good for only 400 watts

What else besides the fridge is running?

It would be interesting to see what the actual voltage of the battery is when the alarm sounds. It may simply be a case of under wiring.

Also looking at your pictures I see no wires coming from the solar panels to the controller

I don't know what lithium cells you are using but that is unbalanced wiring

The 12 volt distribution box should be fed by the batteries with a switch and fuse. The load terminals themselves could be cutting the power when it is not necessary.

There is no switch or fuse for the controller.

Last thing is ciggy outlets are the worse way to go especially if you use the wire that came with them.

 

[Kristalsdreamtrip]

I can change the ciggy wire for 8awg with an xt60 connector. I have those. I removed the panel and batteries from my van for this pic since I'm at a friend's house and have my fridge plugged into 120v right now. Of course I normally have my solar panel attached to the input on my charge controller. I have two 250w panels that were donated to me, on my van with 30a fuses but I only use one panel for now. It seems to be giving me a full charge. That 30a pwm is all I have for now. I haven't been able to afford a good controller yet. I had five 16ah lifepo4 batteries, then my daughter heard me complaining about my fridge and bought me yet another one of those batteries, not knowing that I am saving to buy better ones, so now I have 6. I do already know they are not ideal and I do know I am risking them by connecting more than 4 together but again, it's what I have. I ran out of money so I'm just doing the best I can with what I have for now.

 

[Kristalsdreamtrip]

As far as readings from the controller goes.... I still have problems making sense of them. When I connect it all back up in my van, I'm going to take pics of the readings I'm getting. I'm probably doing or reading something wrong. Maybe then y'all can help me figure it out. I do, as always appreciate everyone who takes the time to read my post and offer bits of advice. I'm always learning.

 

[Kristalsdreamtrip]

This is my challenge, to get the most I can out 9f what I already have.