Testing a LFP Deep Cycle Charging an AC180

Product Discussion BLUETTI Apex & AC Series
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(This Topic will be over several posts;)


PURPOSE;

  1. To check the capacity of a 100Ah LFP deep cycle battery.
  2. To check the recharge time of an AC180 using the Charger 1 (C1) connected to the above 100Ah LFP and what SOC is achieved.
  3. To check the voltage at which C1 shuts off under a 20A load, if possible.
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BACKGROUND;

  1. The LFP is a Pylontech LiFePO4 100Ah that is 9 years old. For 6 of those years it alone powered the 12VDC system of a previously owned caravan. That caravan had a 3 way refrigerator, therefore 12VDC was primarily for lights (LED), water pump etc. as well as a 2kW Erberspacher diesel heater. Average daily use when camping was 35Ah before recharge, which fits within 3 days desirable autonomy.
  2. Since then the battery has been occasionally used to augment Bluetti power station capacity, both at home and camping. It has been flattened about 10 times in its life.
  3. As an aside, the current caravan has a 12VDC compressor fridge and daily use along with the above and a Webasto 2kW diesel heater is approx. 65Ah before recharge. It has 2 x Pylontech 100Ah LFPs in parallel.
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SETUP;

  1. The LFP was charged several times from a Victron Bluesmart 15A – 240VAC charger. Initially at an absorption voltage (AV) of 14.0, left to rest overnight, then at an AV of 14.1, again rested and then at 14.2V. These voltages are adjustable within the Victron App in Expert Mode. This was a gradual increase to allow for cell balancing.
  2. The AC180 has an 1152Wh battery, which will use more than that Wh input to charge and should fully discharge the 100Ah LFP. The AC180 was fully discharged to a SOC of zero % before recharge started.
  3. Charger 1 was set to a 30V output in expert mode. This setting approximates a load on the LFP of 20A, which is 0.2C of the LFP’s capacity. The AC180 display shows an approximate input of 235W. A DC power meter (PM) is connected between the LFP and the C1 input.
    TEST
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RESULTS;
RESULTS

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CONCLUSIONS;

  1. The Pylontech provided 97Ah according to the DC power meter, when charging stopped due to the AC180 SOC reaching 100%. It was then connected to a depleted AC70 in an attempt to garner more charge. However the Charger 1 would not restart at 11.5V battery voltage. There is no doubt at a lower resistive load, the Pylontech had more to give. Regardless a 97% capacity for an aging battery is still a very good result.
  2. It took 4.4 hours to fully recharge the AC180s 1152Wh battery from the 100Ah LFP, which means any other power station at or below 1152Wh i.e. Elite 100v2, AC70 etc. will double or more its capacity from 100Ah.
  3. Although the C1 could have been set to a higher voltage for a quicker chargem this was a 0.2C test on the LFP.
  4. Of not there was a constant 0.1 voltage drop per hour for the first 3 hours (67%) discharged. At some point between 3 & 4 hours this increased, but was not noted. (I was not going to sit and watch for over 4 hours, lol.) From the results, readers can see that as voltage dropped, amps increased. This proves that C1 definitely has a stable output.
  5. The LFP, C1 & AC180, when checked for data, were also touch checked for heat. All were cool to the touch, so no heat issues detected.
  6. Final observation – All through the charge cycle, the AC180 display showed a constant 232W input.


    As a further comment – My reasons for using Pylontech are; 1. They have an Aluminium casing, so more robust for Off Road Travel and heat dissipation. 2. Each has an On/Off button in the top centre of the battery, which disconnects the cells from the terminals via the BMS. This allows for storage isolation, removing the chance of any parasitic loads depletion.