My first LiFePo4 build project

trevor.the.van

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Having been an avid lead acid battery user for many years in 4x4 and recently my own van build - I finally decided to take the plunge into LiFePo4 batteries. Like many here, I spent hours watching Will's videos and learning everything I thought I needed. Then a few weeks ago I took the plunge, bought all the parts and built my first 100Ah portable LiFePo4 battery pack.

I must say, with the knowledge I picked up here - the process was pretty straight forward! Buy the batteries, buy a BMS, wire it all together and put it in a box!

The only issue I had was with the screw terminals on one cell being a little cross threaded, which fortunately caused the bolt to fail and not the internal thread. So I replaced all bolts with new ones - and then everything was good.

I used 100Ah cells from an Australian distributor (I dont like waiting)
I used a 100Amp Daly BMS for a 4s configuration that I was using.
The box, I built that myself and added appropriate fuses, cig sockets, andersons, cut off switch, battery monitor and external terminals.

I performed a top balance as per the standard procedure, and had the cells nicely balanced at 3.6 volts before hooking them up in series and doing a capacity test. I didn't have great monitoring ability on the discharge, so took closer note of the recharge process through the victron MPPT I have hooked up - and charged up with a respectable 1320kWh of power - for a 1280kWh rated pack, I figure that's pretty good.

In my battery box, I have also wired up a 10A Victron MPPT to charge up from solar, and a step-up converter from 12v to 24v, which feeds into the Victron PV input, to use as a battery to battery charger (mainly because I had these parts already).

All up, I'm very happy with the results and now planning my next build which will be a 400Ah pack for a new camper van build I'll be doing this year.

Thanks to everyone on this forum, and Will for provide such a great knowledge base.

Some photos follow. And hit me up for any questions.
01-top-balance.jpg
02-external.jpg
03-internal.jpg
04-charge-components.jpg
05-charge-up.jpg
06-incoming.jpg
07-capacity-report.jpg
 

trevor.the.van

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Supplier I used for the cells was bigweibattery8 on ebay:


Delivery took a couple of days - but of course you pay premium price in that case too. $120 per cell.
 

Supervstech

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If I understand your build, it looks like you have a buck converter on the PV input... why? What is that for?
I am dubious of your Wh totals, be sure you have zeroed the meter. 103ish Ah out of 100Ah cells seems too good to be true!
 

DJSmiley

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If I understand your build, it looks like you have a buck converter on the PV input... why? What is that for?
I am dubious of your Wh totals, be sure you have zeroed the meter. 103ish Ah out of 100Ah cells seems too good to be true!

For B2B charging capabilities

You need a DC-DC charger if you want to eg charge it with a leadacid car battery. If you have a smart alternator eg the battery voltage might be low, and not sufficient to charge the LFP properly.

By using a stepup the 12V (or whatever it is) is boosted to 24V, which is fed to the PV input of the MPPT. The MPPT will take care of the charging profiles, and provide proper charging the LFP (including the boost/float stages as set in the Victron app)

Cheap but nice way to charge from a DC 12V source, without having to buy a DC-DC charger

Only important thing is the 12-24V stepup should have enough power, since he is using a 10A MPPT, and with 14.6V or so (Whatever it is set to), 10A and the MPPT losses, you're looking at 150-155W at the input, thus the 12-24V stepup should be able to provide at least 7A, otherwise it will shutdown/overload.
5A as done in the test is probably with the cells near empty. Assuming a 12V voltage across the cells at 10A, would result in the 5A current draw at the primary (24) side. But as the SOC raises, the cell voltage increases, and to maintain the 10A charge it pulls more amps from the source.
With 13V at 10A (= 3.25V / cell) the charge is 130W, thus pulling 5.4A at the 24V side. If the cells get more full, this increases even more, till approx 6.4A at max (assuming 14.6V)
With a solar panel the MPPT will take care of this and a panel can't overload (It will just deliver it max amps available at a specific time). But the boostconverter will try to maintain the 24V)

I doubt if those stepup things are current limited. I'm quite sure they will shutdown or hickup once overload. Another issue I noticed is heat: I won't recommend running them at full load, they become pretty hot. I would prefer one who is able to provide at least 240W (10A) at 24V, even if it's 'only' using 6-7A max, never run electronics for longer periods on its max ratings if you don't want it to die prematurly.
 
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trevor.the.van

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Messages
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South Coast, NSW, Australia
If I understand your build, it looks like you have a buck converter on the PV input... why? What is that for?
I am dubious of your Wh totals, be sure you have zeroed the meter. 103ish Ah out of 100Ah cells seems too good to be true!
The buck converter lets me plug straight into another battery as it will step up the 12v battery to 24v, which is a good voltage for the PV input. I can then hook this up into my existing van either up to the current battery bank, or to my alternator. It's a poor mans DC-DC charger made from components I already had in my 'box of bits'.

Definitely had a zero setting before I started the recharge, and the discharge went pretty close to this also. But as I said, that was less accurate. Time will tell I guess.
 

trevor.the.van

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South Coast, NSW, Australia
For B2B charging capabilities

You need a DC-DC charger if you want to eg charge it with a leadacid car battery. If you have a smart alternator eg the battery voltage might be low, and not sufficient to charge the LFP properly.

By using a stepup the 12V (or whatever it is) is boosted to 24V, which is fed to the PV input of the MPPT. The MPPT will take care of the charging profiles, and provide proper charging the LFP (including the boost/float stages as set in the Victron app)

Cheap but nice way to charge from a DC 12V source, without having to buy a DC-DC charger

Only important thing is the 12-24V stepup should have enough power, since he is using a 10A MPPT, and with 14.6V or so (Whatever it is set to), 10A and the MPPT losses, you're looking at 150-155W at the input, thus the 12-24V stepup should be able to provide at least 7A, otherwise it will shutdown/overload.
5A as done in the test is probably with the cells near empty. Assuming a 12V voltage across the cells at 10A, would result in the 5A current draw at the primary (24) side. But as the SOC raises, the cell voltage increases, and to maintain the 10A charge it pulls more amps from the source.
With 13V at 10A (= 3.25V / cell) the charge is 130W, thus pulling 5.4A at the 24V side. If the cells get more full, this increases even more, till approx 6.4A at max (assuming 14.6V)
With a solar panel the MPPT will take care of this and a panel can't overload (It will just deliver it max amps available at a specific time). But the boostconverter will try to maintain the 24V)

I doubt if those stepup things are current limited. I'm quite sure they will shutdown or hickup once overload. Another issue I noticed is heat: I won't recommend running them at full load, they become pretty hot. I would prefer one who is able to provide at least 240W (10A) at 24V, even if it's 'only' using 6-7A max, never run electronics for longer periods on its max ratings if you don't want it to die prematurly.
Everything you said... :):)

The step up converter is not current limited, and will cut out if overloaded. This one is 360W (24v 15A) and as the MPPT I have there is only 10Amps, its unlikely to ever be driven at even 50% its rated capacity, so should do the job for me.

Also, feeding it into the Victron gives me all the battery protection I need since the Victron MPPT is well known for quality - and also its adjustability which I like.
 
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Bud Martin

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Can you tell me where you get that DALY BMS from? I cannot read the model numebr from your picture.
My LiFePO4 4s 12V 100A BMS does not look like that and the power leads are very short, yours has much longer power leads.
Thanks.
 

trevor.the.van

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Can you tell me where you get that DALY BMS from? My LiFePO4 4s 12V 100A BMS does not look like that and the power leads are very short, yours has much longer power leads.

Same seller on ebay

 

Bud Martin

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Same seller on ebay

Thanks, I search US EABY using your model DL-24A-F04S100ATJ-MM00, nothing shows up, strange.
The spec of the DL-24A-F04S100ATJ-MM00 also does not match yours, yoru shows 100A CHARGE/DISCHARGE rating, the spec of DL-24A-F04S100ATJ-MM00 shows 100A discharge, 60A charge.
I try to read the model on your sticker, it shows J05U-??????
 
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trevor.the.van

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Thanks, I search US EABY using your model DL-24A-F04S100ATJ-MM00, nothing shows up, strange.
The spec of the DL-24A-F04S100ATJ-MM00 also does not match yours, yoru shows 100A CHARGE/DISCHARGE rating, the spec of DL-24A-F04S100ATJ-MM00 shows 100A discharge, 60A charge.
I try to read the model on your sticker, it shows J05U-??????
I find it quite amazing how many varieties of these things are out there! My model number is J05U-FJ30

20210306_124007.jpg
 

Bud Martin

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I just made contact with Daly factory, the rep said they do not make that model any more, if I want 100A Charge/Discharge I have to get Smart version.
 
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