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DIY Power Tank with a 12V 100Ah LiFePO4 battery: Story, pros & cons and equipment

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#1 mathieucarbou

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Posted 23 September 2022 - 04:53 AM

I wanted to share my experience when I've built my own power tank having 1 unregulated 11-13.5V output and 2 regulated 12V outputs.

 

10 DC Output installed

 

Looking at the batteries for astro, many options are available. I was looking for big LiFePO4 batteries.

 

Complete solutions like BLUETTI, offering with the EB series with  2 regulated 12V 10A max.

  • EB55 is a 537Wh battery (~ 45Ah at 12V) and costs 550 euros.
  • EB70 is a 716Wh battery (~ 60Ah at 12V) and costs 650 euros.

 

There are also raw LiFePO4 batteries like the Amperetime 12V 100Ah LiFePO4 battery (1200Wh) at 600 euros with the 20A charger.

I chose this battery because of the reviews and specs:

  • Has a very good SoC and can nearly maintain more than 11V until the end
  • Has an integrated BMS which shutowns the battery between 9-10V
  • It is at 13.5 fully charged and the recommended cut voltage is 10.8V. It can deliver more than 12V even at 10% capacity.
  • This is also roughly twice the capacity for the same price...

But is it really cheaper ? Because complete solutions come with inverters, a good box, fan, integrated buck boost regulators, BMS, LCD monitors, etc.

 

So what is really the price of a power tank built with such battery ? Let's see...

 

 

NEEDS:

  1. Have at least 2x regulated 12V 10A ports (like BLUETTI), but the advantage of an Ampere Time battery is that it won't be a total of 10A, it will 10A per socket
  2. Have a direct access to the battery voltage (DC 9.5-13.5V in this case)
  3. ON/OFF switch
  4. LCD battery monitor with Shunt and alternate power input so that it works if the battery is too low (small Li backup battery for that)
  5. Transport case with wheels
  6. 14 and 16 AWG at least for the cables

 

Why regulated output ?

 

A lot of people are directly connecting their 12V equipment (Mounts, Asiair, etc) to a LiFePO4 battery. If they are doing that, it doesn't mean you can! For 12V equipment, there is a tolerance range of 10%: so 12V equipment can be powered with ~ 11-13V without problem. If the LiFePO4 battery has a very good SoC and is able to maintain a voltage around this range, then it is fine. Otherwise, it isn't, and it is better to have a regulated 12V output. The Ampere Time battery for example goes from 13.5V and maintains more than 12V until less than 10%. So with such battery, we could get rid of the regulators if we wanted to.

 

The thing is that some devices are more sensitive to voltage compared to others so to not take any chance, I opted to add 2 regulated 12V outputs. Also, using a regulated 12V output helps determining the required capacity for one equipment in advance.

 

EXCEPTIONS: some devices like Asiair sometimes put the supported input voltage in their spec. Example for Asiair: 11-15V.

 

HELPERS:
 

This calculator gives an approximation of cable length depending on the AWG numer, maximum allowed voltage drop and amperage.
 

For example with 16AWG cables CC 5521 cables (see below), I can go up to 6A with a length of 3m and only a 2% voltage drop.

SHOPPING LIST:
 

Required:

 

Note: I took the 20A charger, I think it's worth it for the price difference

Note: these at the 2 regulators to give a constant 12V (10A max). Pay attention to the efficiency level. It has to be has high as possible.

02 Buck boost voltage regulator

Note: I took more to gave spares, but the idea is this one: if you need a few amperage (around 4-5A), then you cna combine 2 wires and go up to 3 meters without any voltage drop. If you need more amp, then just use 1.5m.

Note: hard cases like Pelican or others are super expensive. So I went with hardware cases: they support a high load, are stackable and a lot less expensive. They are not waterproof though.

14 Case

Note: this is to protect the battery in the case

08 DC Outputs

 

Note: I have connected the shunt directly on the battery with a M8 bolt... This avoided me to built a case for the shunt, but you need a M8 bolt for that.

04 Battery monitor with Shunt
03 Some components And tools
01 Some components

 

Note: this is overkill for the need, but I didn't find any other switch with M8 bolts and 6 AWG wires with M8 connectors.

05 Switch OFF And monitor installed

Note: this is to connect in parallel the 3 DC outputs

Note: this is to connect to the DC 5521 female sockets and do some extensions. UN-SOLDER THE THIN CABLES FROM THE 5521 FEMALE SOCKETS: THEIR AWG IS TOO HIGH. WE ONLY NEED THE DC DOCKET.

07 DC Output addon wiring

 

Note: this is to wire the regulators

09 DC Output addon wiring with buck boosts

 

Optional:

 

Note: you'll probably need some cable extensions. You can make them with previous items but this one is 30cm long.

Note: this is only to connect the monitor to the battery M8 equipment... Not required if you can live with the wires directly connected to the M8 screws. I just like things be correctly done so I prefer to have a proper connector and soler the wires onto them.

Note: this is required if you want the batttery monitor to still work when the battery is nearly depleted and enters in protection mode. This one is nice because it can be charged easily with any 12V adapter and has a BMS integrated plus 12V sockets and a power switch.

Note: you don't need it if you take all the wired connectors above. You need it if you want more DIY stuff, more cable length, etc.

Note: useful if you need to power some USB equipment, charge a phone, etc. Can even be powered on the unregulated socket.

 

 

TOOLS:

  • Multimeter
  • Heat gun with heat shrink tubes
  • Insulating red/black tape
  • Screwdrivers
  • Pliers
  • Cutter
  • Soldering equipement
  • Gaffer tape
  • Optional: More heat shrink tubes
  • Optional: quick 12V voltmeter
  • Optional: some DC 12V 5521 connectors easy to wire (tighten with screws)

CONCLUSION:
 

This is an approximate cost of 900 euros to build such power tank. This is a cost of 900 / 100 = 9 euros per Ah.
Compared to that, the BLUETTI EB70 (650 euros for less than 60Ah IN THEORY) has a cost of ~11 euros per Ah.

 

Pros:

  • Unlimited power!
  • The unregulated docket taked power directly from the battery, so the only limit in amps is what the wire can support
  • 2 regulated 12V soket, 10A each
  • The pack can power at least 3 setups at the same time
  • Flexible: thanks to the XT60 wireing, it is really easy to adapt the setup
  • Really fun and interesting to build
  • Thanks to the optional addition, it is even possible to add USB!

 

Cons:

  • More bulky compared to having 2 BLUETTI EB55
  • No inverters for AC
  • Complicated to build and properly wire and choose the right wires
  • Needs more attention and care

Here are some photos of the voltage test:

 

13  Test Of regulated voltage #2
12  Test Of regulated voltage #1
11 Test Of unregulated voltage from battery

 

I hope this thread will help some people choose the right product for them!


Edited by mathieucarbou, 23 September 2022 - 07:41 AM.

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#2 astroboyabdi

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Posted 23 September 2022 - 06:08 AM

This is gold thx for sharing
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#3 mathieucarbou

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Posted 08 October 2022 - 02:25 PM

I've finished my project.

 

So finally, this power bank on wheel is powered by a 12V 100Ah battery and has:

  • A real-time battery monitor with shunt
  • 2x DC 5521 connectors directly connected to the battery at 10-13.5V
  • 2x DC 5521 connectors each one outputs a 12V regulated 10A max
  • 2x Device Chargers with 1.5m cable length (20W power delivery + 18W QC Quick Charge)
  • 6x 1.5m DC 5521 power cables
  • 1x XT60 Extension direct to battery
  • DC-powered USB Hub (that can be connected to the XT-60 extension)
Final #1
Final #2

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#4 Leafus

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Posted 08 October 2022 - 05:25 PM

Wow. I want one. It even looks cool.

Now can we have the budget Lead-Acid version. £150 budget and not needing advanced electrical engineering. I can manage to put battery in a toolbox plus bolt on an off the shelf something that clips on top of the battery.

#5 mathieucarbou

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Posted 09 October 2022 - 01:44 AM

Wow. I want one. It even looks cool.

Now can we have the budget Lead-Acid version. £150 budget and not needing advanced electrical engineering. I can manage to put battery in a toolbox plus bolt on an off the shelf something that clips on top of the battery.

Well, sure, same thing but just replace the battery. The only difference will be that you will need to add a BMS on your battery so that it can shutdown the current otherwise your battery will be drained and will be dead.

Also, one disadvantage is that the unregulated sockets (2x 5531 and 1x XT60) will have a voltage going down really quickly so not as stable.  An ampere time LiFePO4 battery can maintain 12V or more until 90% capacity.


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#6 astrohamp

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Posted 09 October 2022 - 02:52 PM

My airline portable (hopefully) alternative to the lead box I still use puts two12Ah LiFePo4 batteries in a Pelican case.  Fused and wired in parallel using a Powerwerx 4 Position Power Distribution Block (also inside) they terminate into a single through wall PanelPole2, Panel Mount Housing. The Pegasus PPBADV box and mount I power with it monitor and both measure voltage so no need for additional panel meter expense and space allocation.

The series 1270 lead batteries replaced by these Amped LiFePo4 batteries are nearly identical in size making the Pelican 1170 case choice ideal.  Room inside for wiring and an AC charger as well.  The real gain was nearly three times useful power trade up at about one half the weight.  2x7Ah lead @50% drain = 7Ah (84wh @12v) while the 2x12Ah LiFePo4 @80% drain = 19.2Ah (230wh nominal @12v more like 246wh @12.8v).   8lb 10oz all in.  Takes 7 hours to recharge though when run down.

The new battery box is itself small yet merely field power to the instruments hauled on board.  Hence the need for an airline (under seat) package that also contains the less fragile parts of a plane trip dark site outing.  Luck and diligent web searching found that a Pelican iM2300 Storm Case would accept the 1170 case inside.  As shown...with slight trimming of both short sides I was able to just fit one in the other little worse for the wear.  Divider fabrication completes the holders for mount, dovetail saddle (detached), NUC Pc, USB travel router,  Pegasus PPBADV, Hubo HC, hardware, even a Liliput 7" monitor if I choose to bring it.  Behind the wood panel in the iM2300 lid is a 17" laptop.  The downside to all this is it weighs in at 34-35 pounds.  Backpackable as I have one to fit, but will it meet carry on as a hand item especially since I would be dragging a rolling Pelican 1535Air case housing the OTA, camera, chargers, cables... the rest including tripod inside expensive checked bag.  Still cheaper (cost,time) then finding/buying tech at some airport destination.

Several considerations here, the major one being is it all airline friendly in size, weight, number of containers, contents?  Contents specifically since there are severe LiFePo4 capacity air travel restrictions, ones "With airline approval, passengers may also carry up to two spare larger lithium ion batteries (101–160 Wh)...This size covers the larger after-market extended-life laptop computer batteries and some larger batteries used in professional audio/visual equipment." where I would be carrying two 12vx12Ah (nominal 144Wh) batteries.  AND why I chose the 12v 12Ah (clearly stated on outside) batteries to meet the strict guidelines.  This stuff IS professional audio/visual equipment right?  The 12v-12Ah Amped LiFePo4s I'm using are no longer made unfortunately replaced by even higher capacity models of similar size.

I cannot check the full on iM2300 case with ANY LiFePo4 batteries in it.  So if need be they would get yanked, stuffed back into the carry on back pack while checking the iM2300 case, emptied battery box inside to ...ah... keep things from moving.

Not sure I want to fly anywhere anymore anyway.

 

 

 

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#7 fishonkevin

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Posted 18 October 2022 - 01:11 PM

How accurate is the Battery Monitor that you are using?  Especially the AH. Does it register the capacity left after a night of use? If fully charged at the start of the night, does it read 100ah and after use does it read how much capacity is left? The one I have is not accurate at all. After fully charged it only reads 5ah for a 30ah ( 2 x 15ah in parallel ). I'm looking for one that is more accurate.



#8 mathieucarbou

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Posted 18 October 2022 - 03:34 PM

How accurate is the Battery Monitor that you are using?  Especially the AH. Does it register the capacity left after a night of use? If fully charged at the start of the night, does it read 100ah and after use does it read how much capacity is left? The one I have is not accurate at all. After fully charged it only reads 5ah for a 30ah ( 2 x 15ah in parallel ). I'm looking for one that is more accurate.

I cannot say I have enough usage since I've recently built it, but so far I am happy.

 

The voltage more often matches the on on my multimeter, battery OFF and ON.

 

I say sometimes because just after recharging the battery, I happen to have some issues: the battery is at a little more than 13.5V (like 13.55, 13.56). And the monitor displays 13.2, a voltmeter on the 12V DC socket displays 13.3V and the multimeter displays 13.55V. This 0.25V difference is EXACTLY the voltage measured by the monitor when I power it with the little Li battery, which serves as a backup battery for the monitor, and I keep the battery switch to OFF (so no current draw from the big battery).

 

Voltage Battery OFF
Voltage Battery ON
 
And the current measured between the multimeter and the monitor has a difference of about 100-130mA. Part of this difference is caused by the battery monitor which is drawing between 40-60 mA. The other part could be an inaccuracy: this device has an inaccuracy of 1% (specs) but I saw some users having measured an inaccuracy of 2-3%. In my case for this measure, 60 / 5630 is exactly an inaccuracy of 1%.
 
Current Battery ON with connected devices

 

For the capacity, it is cumulative. Each time I recharge the battery, I reset the running time, capacity, and energy, which are all cumulated values stored in the battery monitor even when it is not powered. I have set the maximum voltage to be 13.5V and cutoff voltage to be 9.5V according to the spec of the AmpereTime SoC. They recommend a disconnect at 10.8V and the battery is at 0-1% capacity at 9.5V. So the bars in the middle are computed based on these values

 

That's how mine work. It is far from being perfect but it is precise enough.

There are many of them on AliExpress or other places I saw.

 

Hope it helps!



#9 astrohamp

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Posted 18 October 2022 - 07:52 PM

fish'... in my case the Hubo hand controller monitors voltage it sees at the mount I'm assuming.  The Pegasus PPBADV seems to have a shunt in series with it's through current therefore displays Ah used through the box as well as the battery voltage it sees at it's input, another assumption.

From Ah used I can judge how much is left in the battery from a quick calculation of total capacity of 246Wh.  The Pegasus does not have a 'tally' for use, or a reset point after charge like some monitors.

I have only once, just recently, run down the LiFePo4 battery enough to have the BMS kick in an cut off voltage/power out of the battery.  I do not want to do this very often so as to extend cycle life past the 3000 mark.  Not that I will be observing that long, rather to ensure longest life at highest capacity possible as all batteries deteriorate with use/age and pulling 100% many time will shorten life.



#10 fishonkevin

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Posted 19 October 2022 - 09:55 AM

Thanks for the replies. There are a lot of different ones on Amazon.  Just have to read reviews, especially 1-and 2- Star, to chose which I think will work best for me.



#11 mathieucarbou

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Posted 19 October 2022 - 10:31 AM

Thanks for the replies. There are a lot of different ones on Amazon.  Just have to read reviews, especially 1-and 2- Star, to chose which I think will work best for me.

I was searching for a Coulombmeter with a shunt (more precise to display current passing through and accumulation), not with a ring (magnetic), and wanted something where I can reset, set the low and high voltage, and also turn the screen off to reduce its power consumption. Some are also monitoring the recharge or have bluetooth, but I didn't need that and also bluetooth == more power consumption and requires to rely on an app that might be discontinued at a time...

 

For these kind of electronic devices, I first tend to look at AliExpress because Amazon (at least Amazon.fr) does not have a lot of choice.

Then when I see something interesting, I check the bad reviews too ;-) But sometimes they are bad because people can do crazy things also ;)

Then I would first check to order from Amazon (fats hipping and pleasant return policy), otherwise from China.


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