Testing My Self-Built Home Battery Under Heavy Load

Steps

1. 1

   Step 1: Reviewing system setup and safety limits

   I use three 5 kVA MultiPlus 2 units and a modified Lynx busbar to save costs. Inside the steel cabinet, I have a 16S setup with EVE MB31 battery cells. These cells have a C-rating of 0.5 and 314 Amp hours, meaning they can theoretically handle 357 Amps.

   However, I limit each accupack to a maximum of 100 Amps to protect the lifespan of the batteries. My cables, fuses, and BMS are all rated for 100 Amps max, so I stay well away from the absolute edge.

   What I used

   Item	Amount	Notes
   MultiPlus 2 units	3	5 kVA units
   Links busbar	1	Modified to save costs
   EVE MB31 battery cells	16	16S setup behind each other

2. 2

   Step 2: Checking temperatures with a thermal camera

   I use a GoJojo thermal camera, which is very cheap compared to standard ones. While it has a limited resolution, it costs around 100 euros and gives a lot of useful information. It lets me see temperature differences in the battery cells after long charging sessions, and spots hot connection points or bolts that indicate bad contacts or overloads.

   Before starting, I check the cold system: the back multi-inverters are at 14 to 15 degrees, the Cerbo is warmer due to its internal power supply, and the busbar is fully cold.

   What I used

   Item	Amount	Notes
   GoJojo thermal camera	1	Low cost thermal camera around 100 euros

3. 3

   Step 3: Explaining how the thermal camera works

   The thermal camera uses a color scale where black means cold and yellow means hot. This shows temperature differences rather than making things actually glow red like fire. Even a small difference of three degrees can make one part look very dark and another look very bright.

4. 4

   Step 4: Starting the high load discharge test

   I set the multi-inverters to feed 4.5 kW back into the grid. This aims to draw 95 to 98 Amps from the battery pack. HomeWizard shows we are feeding over 4 kW back into the grid, which totals around 4.5 kW including house usage.

   The BMS app shows 96.5 Amps drawn from the battery, which is safely within specifications. I choose 95 to 98 Amps because exact 100 Amp settings fluctuate and trigger the overcurrent safety protection, causing the system to shut down.

   What I used

   Item	Amount	Notes
   HomeWizard	1	Used to monitor grid return power

5. 5

   Step 5: Inspecting cables and fuses after ten minutes

   I remove the plating from the Lynx busbar to look underneath with the thermal camera. Ten minutes into the test, the multi-inverters start warming up. The battery cable running to the battery pack reaches 90 degrees on the center while the wall is 12 degrees, showing a 7 degree difference.

   The 70 square millimeter cables stay cool with no temperature difference. The BMS reads 20 degrees, and the plus and minus cables going through the wall cable duct to the busbar reach 25 degrees with nearly 100 Amps flowing through them.

6. 6

   Step 6: Checking half an hour into the test

   We are now half an hour into the test, and the cooling fans on the three multi-inverters are running hard. The battery feed cable to the busbar is at 26 degrees, which is a very nice temperature. The Mega fuses remain cool because each multi-inverter handles only 1.5 kW, putting about 15 Watts through each fuse.

   The cell busbars with black heat shrink show 16 degrees while the battery cell itself is at 14 degrees, a minor 2 degree difference.

7. 7

   Step 7: Clearing up the balancing wires debate

   I want to settle a discussion from Facebook regarding the thin wires on the battery pack. Many people panicked seeing the thin red cables, thinking high power runs through them and poses a danger. These are just the balancing wires, and as the thermal camera shows, they are completely ice cold with no heat at all.

   They are used for measuring voltages and carry only 0.6 Amps during cell balancing.

8. 8

   Step 8: Inspecting front battery pack temperatures

   At the front of the battery pack, the plus cable sits stable at 34 degrees for over an hour and gets no warmer. The Mega fuse underneath gets warm at 32 degrees because a lot of power flows through it, and the same applies to the minus side. The BMS remains stable at 30 degrees.

   Everything shows an even, consistent temperature with no hotspots caused by loose bolts or high resistance.

9. 9

   Step 9: Inspecting the system at two hours

   Two hours into the test, the battery is about 50 percent empty. The BMS stands at 34 degrees, which is less warm than an average laptop. The plus cable is around 30 degrees, just slightly above room temperature.

   The cells themselves are at 16 degrees, about 5 degrees above ambient temperature. The class T fuse is warmer than the busbar, which is completely normal because all energy passes through that narrow restriction designed to burn through first in an emergency.

10. 10

    Step 10: Completing the three hour maximum load test

    After more than 3 hours, the multi-inverters shut off automatically because the battery is empty. The accucells are at 16 degrees, showing no unexpected hotspots, warm busbars, or warm screw connections. The continuous 4.5 kW test proves the system easily handles heavy loads well within specifications, even though my practical use will be around 3 kW.

11. 11

    Step 11: Demonstrating the thermal camera around the room

    To show how the camera works in practice, I point it at my feet and shoes to see where I just walked. I can even look around my living room to spot my dog and my son sitting on the couch. This proves how easily the camera detects warm and cold spots in daily life.

12. 12

    Step 12: Supporting the channel with an affiliate link

    I am very happy with this GoJojo thermal camera and use it all the time for work and home projects. If you want to buy one as well, please use the affiliate link in the description below. Ordering through this link helps support my channel and this project with a small commission.

    What I used

    Item	Amount	Notes
    GoJojo thermal camera	1	Optional purchase to support the channel

13. 13

    Step 13: Takeaways

    • Limiting battery discharge to 100 Amps protects cell lifespan and keeps cables and fuses safely within limits.

    • A budget thermal camera is an invaluable tool for spotting hot connections and monitoring temperature differences before issues arise.

    • Thin balancing wires carry minimal current and do not heat up during high power delivery.

    • Fuses like the class T fuse are designed to run slightly warmer due to concentrated current flow.