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Lithium LiFePO4 LFP DIY Batteries

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#211 buckland

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Posted 19 May 2019 - 06:10 PM

Here are the Victron app battery settings page. Note I set the float and the absorb volts but then when I select the LiFePo4 for battery type it changes the settings. IMG_7970.JPG IMG_7971.JPG
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#212 rando

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Posted 19 May 2019 - 08:21 PM

Based on what you are seeing on the Victron and this photo assuming it is how it is set up:

index.php?app=core&module=attach&section

 

It appears that your battery isn't actually connected to its output.    You need to run a heavy (10AWG) wire from the 'B-' terminal on the BMS board to the terminal with the 'black 4' wire on the terminal block.    The main output terminals of your battery will then become the 'red 1' terminal on the wiring block an the 'P-' terminal on the BMS which already has a wire.   

 

The primary purpose of the BMS is to protect the cells in your battery from over or under charge.   It does this by measuring the voltage of each cell using the skinny wires connected to the white connector.   These wire are only to measure the voltage and aren't supposed to carry any current.   If the BMS senses that any individual cell is over or under voltage it will disconnect the heavy negative terminal (that should run through the BMS) from the battery and save it from being damaged.     Yo are using a different BMS to the one I am using but it may have balancing as well, in which case the back box is a bit redundant.   What the black box provides is a quick way to see where your cells are, how well they are in balance and a way to manually force a balances.

 

When you switch the battery type on your Victron to LiFePO4, all that does is load some pre configured settings, which then over rides the settings you entered - you would do better to use custom settings for your usage.

 

 

 


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#213 rando

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Posted 19 May 2019 - 08:23 PM

PS you probably want to make the 'absorption time' shorter, like an hour.   The ideal charge profile for a lithium battery is to bring it up to the specified bulk voltage (13.8V in this case) then shut off the charger, no absorption and no float charge required, which is one of the big advantages of lithium.


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#214 buckland

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Posted 20 May 2019 - 12:01 AM

Got it and done. Appreciate your sticking with the explanations. I am starting to 'get it'...all the parts are making sense and though understanding is shallow compared to electrical folks... I have learned a bunch. This will be a longterm solution for power.

I assume the Fluke reading of 13.13 V and the BMS montitor with 13.13 V being different from the Victron app reading of 13.6 V of the battery is no big deal? All in all a relief it works!

I now have to do some cutting (metal rollover couch support on front wall) to be able to get this battery pack into the Eagle battery box.

Construction work I feel good about...it won't be a big job.

I also assume that it would not be a big deal to have the Victron horizontally mounted instead of vertically (as stated in the install paper).  Just need to put it where it will fit in that battery box corner. 

I hope that others, who might be on the fence of whether or not to try this, will feel confidence to give it a go. It currently is an economical way to upgrade batteries when the AGM start to fade and they should last a long time. It is also good to learn new things even though they seem daunting. I certainly went through a lot of solder! Well worth it.

Thanks Lars 


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#215 rando

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Posted 20 May 2019 - 10:17 PM

If everything is connected correctly the Victron and the BMS/Fluke should now read the same voltage (+/- 0.01).  


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#216 buckland

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Posted 20 May 2019 - 10:34 PM

And that happened today! I finished the set up and plugged in the solar panel and suddenly the monitor started to show voltage changing as the Victron was on bulk charge. Over an hour they settled down and were closer to 3.3 each. I put on the balancer and hope that they will converge. I am very excited that things are coming together. I have bought a shunt and voltage display .... next step after install and have a vague idea (YouTube) how to set this up to monitor in and out usage to battery and load. Sure wish I learned this awhile ago.
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#217 buckland

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Posted 20 May 2019 - 11:07 PM

The next stage is the shunt and battery monitor. Here are a few photos ...the first is the BMS monitor that now seems to be responding well.

Attached Thumbnails

  • IMG_7978.jpg
  • IMG_7976.jpg
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#218 buckland

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Posted 26 May 2019 - 07:07 PM

As mentioned in the shunt thread, the Eagle has landed! I just decided to wire the shunt for battery and finished the install. It seems to work (yeah I am always amazed ). Thanks to Lars and Vic especially for your help. It took a year all told as life took a detour but getting out those two 55 pound AGM batteries and then putting the new 42 pound LiFePo4 battery in felt real good. I will plug in the portable panel soon and see how that works. The Victron app is real nice to see what is happening ... how much each item draws when running. The shunt monitor works as well so all in all I could not be happier. I could not have even attempted this without the help and I have learned a lot in the process (one of which is I am not a natural at soldering :mellow: ).

Not that I know much but if anyone attempting to make the battery needs to ask basic questions feel free to ask.  

Attached Thumbnails

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Edited by buckland, 26 May 2019 - 07:08 PM.

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