Do i need to use a charge controller between battery and 12 volt cigarette plug to keep from blowing the fuse in my car?

[jamescompi]

I am building a camping/glamping battery pack using 4 lifepo4 125 ah batteries and my question is do I need a second smaller charge controller for using the cigarette lighter plug in my car to top it off to avoid blowing the fuse in my car? Or will it only pull what the plug can safely put out?

 

[Bud Martin]

Your cigarette outlet is probably fuse with 10A fuse, 15A fuse at the most. I would use charger that will limit the current draw from the cigarette outlet and will also properly charge your LiFePO4 battery bank..

 

[jamescompi]

So limit the charge controller to say 10 amps?

 

[jamescompi]

I'm going to have a 30 amp charge controller for my 110 to 12 volt converter for charging from the wall already my question was should I pick up a second 10 amp one for pulling 12 volt from the car or would the 30 amp one somehow know to only pull 10 amps?

 

[Bud Martin]

You should so you will not draw more than 10A from cigarette outlet, the charger will have some conversion loss which mean if the current draw from the cigarette outlet is 10A, the output charge current will be less than 10A. You should show us the spec sheet of the charger you are going to get first before buying it. You should also check the fuse in your car to see if it has 10A fuse or 15A fuse for the cigarette outlet.

 

[jamescompi]

I'm looking at this one for the 10 amp

https://www.amazon.com/ExpertPower-Controller-Auto-Select-Intelligent-Regulator/dp/B08ZK3PT3P/ref=sr_1_3?dchild=1&keywords=10+amp+solar+charge+controller+lifepo4&qid=1619567302&sr=8-3

And the 30 amp version for wall power However i am open to suggestions for sure first time builder.

 

[Bud Martin]

That unit the link is Solar Charger Controller, you are trying to charge your battery pack form cigarette output so you need DC-DC charger.
So at this point do you also have Solar Charger Controller? I read your post #1 again, it sounds like you do not have Solar Charger Controller.

 

[Forbisher]

I'm looking at this one for the 10 amp

https://www.amazon.com/ExpertPower-Controller-Auto-Select-Intelligent-Regulator/dp/B08ZK3PT3P/ref=sr_1_3?dchild=1&keywords=10+amp+solar+charge+controller+lifepo4&qid=1619567302&sr=8-3

And the 30 amp version for wall power However i am open to suggestions for sure first time builder.

Thats a SOLAR charge controller only used for charging with solar panels.

You need a battery Charger.

Also 4 lifepo4 125 ah "batteries" are probably four 3.2V cells in series making a 12.8V battery.

 

[jamescompi]

Correct i have not purchased anything as of yet I was under the impression that the solar charge controller would work with my cars 14.5 volt output like it would with solar panel. is this not correct?

 

[jamescompi]

do I even need one? if I say hook up the wires from the 12 volt directly to the battery the bms should handle the charging itself my only concern is that the bms would draw too many amps and blow the fuse so I was thinking I could utalize a 10 amp charge controler to regulate the amp draw down to 10 amps so as not to blow the fuse.

 

[Bud Martin]

The BMS is to protect the batteries from over charged or discharged, what draw the current from your car are the batteries, the BMS is the batteries management and it draws small current to run.
When you hook up the batteries directly it will draw lots of current when the batteries is low, it can try to draw more than 10A from the cigarette outlet. Do you know what the maximum charge current the battery pack spec is? The maximum charging current the BMS will allow should be printed on the spec sheet of the battery pack. For example if the max charging current limit by the BMS is 50A it means the battery can draw as much as 50A and the BMS goes into shutdown if the batteries will try draw >50A. LiFePO4 can be charged up to 1C, so in your case, it will be 125A, but if the BMS can only handle 50A then it will only allow up to 50A to be fed to the batteries. BMS does not regulate charging current, it will only allow current up to the maximum the BMS can handle to flow into the batteries or out off batteries. That is why you need proper charger.
So what is the spec of your battery pack?

 

[Bud Martin]

Correct i have not purchased anything as of yet I was under the impression that the solar charge controller would work with my cars 14.5 volt output like it would with solar panel. is this not correct?

The charging Voltage must be higher than the batteries, so if you want to charge LiFePO4 to 13.40V (905 SOC), so the charger has to be higher than 13.40V, so if you feed PWM SCC with 14.5V which is only about 1V higher than the battery it may work, you can try it.

 

[jamescompi]

That's a screenshot of the batteries I am looking to buy

So what would be better a solar charge controller or a DC to DC charger or are they the same? And I am oversizing the system in the hopes of running the pack in the middle 80% to extend the life my CPAP only draws 350 watts when humidifier and heated tube are running so this pack will last me and any devices I want to charge a very long time anyway

Perhaps use a DC to DC charger for the car and a 300 watt ac to DC charger connected to the main bus bar for wall charging?

 

[chrisski]

You may be able to find a DC to DC charger of 10 amps or less with a lithium charge profile.

One thing to think about though is how long you need to run the engine in a car to charge something. At idle, depending on the vehicle and alternator, there may not be a lot of spare amps at idle. Even at a full 10 amp charge, with 500 ah of lithium batteries, a ten amp charger will barely put a dent in charging.

If I have several cloudy bad weather days in a row, I have a generator I hook my RV converter to. Doesn’t really matter what the generator is, my converter only charges my battery at 15 amps. One day when I used 165 ah, I charged the battery for 4 hours, and between that and the reduced solar energy because of the clouds, Iwas back to 100%.

IMO, to charge a 500 ah pack from a vehicle, need a charger with more amperage, but at that point, the vehicle really can’t idle to produce that much energy, so a high idle mod to the vehicle or driving around. That also means getting a fused circuit from the battery. For me, that’s why I still have my generator and have not went with a DC to DC charger.

 

[jamescompi]

that was kind of my thought process too i was looking at charging it home with the 3-400 watt ac to dc charger and or leaving it in my compass plugged in as my 12 volt plugs dont run without the jeep being on anyway and it would only be used sparingly a few times a year when we are camping or when the power gos out so the time to charge it would be a non issue for me only that it has enough charge to run a 3-4 day camping trip and if we are running around in the jeep it can be "topped off" or put some charge back in it more likely as we are driving around.

 

[Bud Martin]

View attachment 47019
That's a screenshot of the batteries I am looking to buy

So what would be better a solar charge controller or a DC to DC charger or are they the same? And I am oversizing the system in the hopes of running the pack in the middle 80% to extend the life my CPAP only draws 350 watts when humidifier and heated tube are running so this pack will last me and any devices I want to charge a very long time anyway

Perhaps use a DC to DC charger for the car and a 300 watt ac to DC charger connected to the main bus bar for wall charging?

OK, that is the spec of the raw battery, not the 12V battery pack with BMS. I thought you are buying battery pack, already made pack complete with BMS. I miss the "I am building a camping/glamping battery pack" part completely, sorry about that.

 

[jamescompi]

lol no worries this is all new to me damn youtube giving me ideas on how to save $500 and make more work for myself lol

 

[Bud Martin]

"I am building a camping/glamping battery pack using 4 lifepo4 125 ah batteries"
You are building JUSTT ONE 12V 125Ah battery pack, correct? Not four battery packs and connected in parallel to form 12v 500Ah battery bank, correct?

 

[Bud Martin]

You may be able to find a DC to DC charger of 10 amps or less with a lithium charge profile.

One thing to think about though is how long you need to run the engine in a car to charge something. At idle, depending on the vehicle and alternator, there may not be a lot of spare amps at idle. Even at a full 10 amp charge, with 500 ah of lithium batteries, a ten amp charger will barely put a dent in charging.

If I have several cloudy bad weather days in a row, I have a generator I hook my RV converter to. Doesn’t really matter what the generator is, my converter only charges my battery at 15 amps. One day when I used 165 ah, I charged the battery for 4 hours, and between that and the reduced solar energy because of the clouds, Iwas back to 100%.

IMO, to charge a 500 ah pack from a vehicle, need a charger with more amperage, but at that point, the vehicle really can’t idle to produce that much energy, so a high idle mod to the vehicle or driving around. That also means getting a fused circuit from the battery. For me, that’s why I still have my generator and have not went with a DC to DC charger.

OP post #1: "I am building a camping/glamping battery pack using 4 lifepo4 125 ah batteries"

I think he is building only ONE 12V 125Ah battery pack made from four 3.2V 125Ah batteries connected in series to form ONE 12V 125Ah battery pack.

 

[jamescompi]

that is correct however the case I am using is large enough where I could run a second 12V 125AH pack in it as well and have it connect to a second case with the inverter and power distribution but thats another project for later