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How to build a 5Kwh Power Wall using Headway 38120 LifePo4 Batteries Answered

Frequent power cut during the summer and hours of no power issue during the monsoon makes our lives miserable. It's a common picture in rural areas where the overhead power line connection is prevalent. This led me to think about an alternative power back up that would be way better than the conventional LA or SLA battery solutions. With the constant advancement in the technology, new dimensions are being unfolded to us and I believe, the powerful Headway 38120 batteries are going to reign in the market for quite sometime. I need help from the experts to build a 5kwa Power Wall using Headway 38130 LifePo4 cells and an Inverter too. The parameters are: Output Voltage: 230v, Max Load: >500wh (I'm looking for 10hrs bkp= 5kwh), I'm clueless about how many cells I might need and how many of them will be in series and in parallel connection. Do I need a custom built charger for these LifePo4 cells and BMS too? Please help me up.



1 year ago

Adding up your 5 Kwh with the consumption of the inverter (20 - 50 Watt per hour) and thinking about 85% efficency for the inverter i see some 6,1 - 6,4 Kwh of needed capacity.
Although it would not be wise to chose the Batteriepack that small, we are allready talking about 190 - 200 Cells. I don´t know about the prices for these cells in your country, but in Germany this would be quite a investment.

How many cells in series an parallel depends on the inverter. If your demand does not exceed 500 Watts you could go for a 12V inverter. If there is a fridge you need about 10 times of the average current draw for 2 Seconds for the Compressor to start up.
In that case i would chose 24 Volts to reduce the Voltagedrop over the cables.
You have to look up the specs. of the inverter if it is strong enough.

If you go for 24 Volts we are talking about at least 25 Cells parallel and 8 of these Packs in series. (8S25P) Chargers for 24V are available, you don´t need to custom build.
To charge the Pack in about 10 Hours you need 20 Amps of charging current.
BMS is highly recommended.

In my opinion Headway are a bad choice for a 24V Powerbank, as you need a BIG number of connectors for 200+ cells. I would go for Winston Power Cell 3,2V WB-LYP 100AH instead.
200 Headway equal 16 Winstons, 2 parallel and a series of 8. (2S8P)
(32 Bolts to turn instead of 400!)

I do have a Power Backup operational, using a 24 Volts 2000 Watts Inverter, 12 Lead Acid Batterys (2V 240Ah each), 4 Photovoltaik Panels and a maximum Powerpoint Tracker. This works just fine since 10 Years now.

If you could find a used Forklift-Lead-Acid Battery and the matching charger in good working condition, you could build your Power-Backup for a fraction of the Price, just adding up the Inverter...
Good Luck!


Reply 1 year ago

Thanks very much, Battery Wizard, for enlightening me. My consumption will always be less than 400wh, despite having all my lights, fans and appliances (not refrigerator) turned on. However, your suggestion for Winston Power Cells is great as compared to my idea about Headway Batteries. After knowing from you about the Winston Power Cells I searched for the availability of similar batteries in our country (India) and found that there's a company that manufacturers similar batteries. I'm yet to get the price quote from them. Anyways, thanks once again.