LiFePO4 12 V battery - DIY powerstation (suggestions)

[Calzune]

Im planning on building my own powerstation so I can image from remote locations. Since a diy solution is SO much cheaper than a "finished" portable battery I want to build one. i just need some suggestions for a good battery (EU)

My plan is to go with: 

• LiFePO4 12 V 100 Ah
• battery box
• usb charging ports,
• cigarette charging port etc.

I will connect the battery to my pegasus powerbox via cigarette lighter, and the powerbox will give all my gear power (2600mm,eq6r, guidecamera, mele quieter 3 mini pc, 2x dew heater and focuser)

Since there are tons of different batteries I need some suggestions.

I live in Sweden so the german Amazon is where im going to buy it from: https://www.amazon.de/s?k=lifepo4+100ah+12v&crid=2MA4JXXBEYRJQ&sprefix=lifepo4+100ah+12v%2Caps%2C83&ref=nb_sb_noss_1
 

Edited August 27, 2023 by Calzune

[Cosmic Geoff]

I have a Celestron LiFEPO4 power tank which already has USB ports built into it, not to mention handy red and white work-lights.  Note that a "12v" LIFEPO4 battery will require a specialist battery charger - mine came with a 16 volt charger.

[Naughty Neal]

12V Lifepo4 /LFP will need a 4s lifepo charger, not hard or difficult to buy.

If self building then EVE LF105ah  prismatic cell modules is one route to go, here in the UK the Grade A modules are £60 per module or a LF280K /280ah module is £100.

A home build though isn't always going to be cheaper, though a larger 280ah most likely will be.

 

 

Edited August 27, 2023 by Naughty Neal

[AstroKeith]

That battery comes with a BMS so that's good.

I would have a range of outputs.

• Cigarette  lighter style (Yuk, if you must!) straight off the battery for heavy duty items that dont care too much about voltage.
• 5.5/2.1mm 12 volt output sockets, fed by a DC/DC converter. So you get a steady 12V https://www.amazon.de/-/en/Converter-Waterproof-Downward-Regulator-Surveillance/dp/B0922RYXJ5/ref=sr_1_5?crid=2KCZIZNJ6HOGY&keywords=12%2Bdc%2Bdc%2Bconverter&qid=1693147512&sprefix=12%2Bdc%2Bdc%2Bconverter%2Caps%2C90&sr=8-5&th=1
• A couple of USB A type sockets for 5V/2.4A
• A couple of USB C PD sockets https://thepihut.com/products/sparkfun-power-delivery-board-usb-c-qwiic?variant=39558770786499&currency=GBP&utm_medium=product_sync&utm_source=google&utm_content=sag_organic&utm_campaign=sag_organic&gclid=Cj0KCQjw6KunBhDxARIsAKFUGs-fDZXFGKL8OKSmDwpxJYGTlv8Ez3WIlJqiBrAN22GU_L8kXvvPctYaAhBDEALw_wcB
• A panel meter showing capacity drawn so far, battery voltage and current being drawn.

[Calzune]

41 minutes ago, AstroKeith said:

That battery comes with a BMS so that's good.

I would have a range of outputs.

• Cigarette  lighter style (Yuk, if you must!) straight off the battery for heavy duty items that dont care too much about voltage.
• 5.5/2.1mm 12 volt output sockets, fed by a DC/DC converter. So you get a steady 12V https://www.amazon.de/-/en/Converter-Waterproof-Downward-Regulator-Surveillance/dp/B0922RYXJ5/ref=sr_1_5?crid=2KCZIZNJ6HOGY&keywords=12%2Bdc%2Bdc%2Bconverter&qid=1693147512&sprefix=12%2Bdc%2Bdc%2Bconverter%2Caps%2C90&sr=8-5&th=1
• A couple of USB A type sockets for 5V/2.4A
• A couple of USB C PD sockets https://thepihut.com/products/sparkfun-power-delivery-board-usb-c-qwiic?variant=39558770786499&currency=GBP&utm_medium=product_sync&utm_source=google&utm_content=sag_organic&utm_campaign=sag_organic&gclid=Cj0KCQjw6KunBhDxARIsAKFUGs-fDZXFGKL8OKSmDwpxJYGTlv8Ez3WIlJqiBrAN22GU_L8kXvvPctYaAhBDEALw_wcB
• A panel meter showing capacity drawn so far, battery voltage and current being drawn.

thanks! but is it not better to use a 13.8V converter instead for some headroom? : https://www.amazon.se/dp/B07XTB9YCK/?coliid=I2YXRID7YVZSLS&colid=3GZ14DKTFIXXJ&psc=1&ref_=list_c_wl_lv_ov_lig_dp_it

[Cosmic Geoff]

Why would you want 12v or 13.8 volt regulators/converters?  I have run mounts directly from my LIFEPO4 power tank for years without incident.  The actual output voltage versus discharge state of these batteries can be found on data sheets.

[AstroKeith]

7 minutes ago, Cosmic Geoff said:

Why would you want 12v or 13.8 volt regulators/converters?  I have run mounts directly from my LIFEPO4 power tank for years without incident.  The actual output voltage versus discharge state of these batteries can be found on data sheets.

Indeed these batteries do a have fairly flat discharge curve and so most cases will be fine.

I guess my recommendation comes from being an equipment designer. 

[AstroKeith]

1 hour ago, Calzune said:

thanks! but is it not better to use a 13.8V converter instead for some headroom? : https://www.amazon.se/dp/B07XTB9YCK/?coliid=I2YXRID7YVZSLS&colid=3GZ14DKTFIXXJ&psc=1&ref_=list_c_wl_lv_ov_lig_dp_it

Ah the old 13.8 volt argument!

The reason people have to increase their supply voltage is because of voltage drop down the cable. This means they arent using thick enough conductors.

Using 13,8 volts with volts lost in the cable is OK for steady loads. But many mounts use stepper motors and other kit (ie dew heaters) may use PWM. This means that the current down the supply cable is pulsing which means the voltage will be too.

So use 13.8V, but also make sure your cables are thick.

[Calzune]

I forgot to show how im going to connect everything so here it is: I will connect the battery to my pegasus powerbox via cigarette lighter, and the powerbox will give all my gear power (2600mm,eq6r, guidecamera, mele quieter 3 mini pc, 2x dew heater and focuser)
 

Im planning on buying this cable is it thick enough?: https://www.amazon.se/dp/B07D7G8ZJ7/?coliid=I1UANSMEPP6WXQ&colid=3GZ14DKTFIXXJ&ref_=list_c_wl_lv_ov_lig_dp_it&th=1
 

[Carbon Brush]

Throwing something else into the pot.
If you are building your own kit and basing it around 4 cells, you need to think about the voltage the equipment may be subjected to when in use.
A LiPO charges at 4.2V/cell = 16.8V for a 4 cell stack.
You also MUST MUST use a BMS with charge balance if you buy your own cells.

Unless you really know what you are doing with lithium cells, buy a pre-assembled lithium pack with the protection already built in.
IMPORTANT. Read the safety approvals and check the documents exist.
There (almost weekly) reports in the UK news about lithium battery fires in houses, caused by cheapie dodgy imported product.
In some cases there are deaths.
In the wrong hands, or incorrectly used, lithium batteries are best thought of as potential fireworks and bombs.
Sorry if this seems heavy handed. But lithium cells are often kept in our homes without thinking about safety.

These people are not cheap. But their products meets safety standards and the documents to prove it are readily available.
https://tracerpower.com/

Can you get similar traceable safety documents and test reports from an Amazon seller?

HTH, David.

[Naughty Neal]

Lipo should  be avoided as the chemistry isn't as safe as the Lifepo4/LFP chemistry, I think carbon brush is confusing LIPO/Lifepo4 up a little.   

For a static enegy choice Lifepo4 /LFP every day for a far more stable energy source.

The 12v rating is just a noimal rating of the DC equipement but it is best to check the spes of the device for a max temporary rating as any 12 nominal battery will have a higher max temporary charge voltage.

And yes as mentioned a BMS is must to monitor charge /discharge voltage and must be the correct type for the batteyr chemistry in use.  

The voltages  differs for the two main lithium chemistries.

Lipo/Lion are 3s for 12v , each series having a max 4.2v charge for total 12.6v.

 

Lifepo4/LFP  is 4s for 12v , each series having a max 3.6/3.65v  charge for total of 14.4/14.6v.  Typically with LFP there is little or any gain by charging to 3.65v so 3.35v or 13.4v for the 4s is 99%.  

For LFP the main energy is stored between the voltage of 13.4v /99% down to 13v/30% , the voltage curve being very shallow.

 

 

 

 

Edited August 28, 2023 by Naughty Neal