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I'm building a hybrid PV/battery kart that is intended to weigh 120 kg with driver and average 30 km/h on a flat tarmac go kart track in full sun. I'm expecting that to require average power of 48 V x 25 A = 1200 W. Going through a corner that would mean more current, maybe max 40 A.

Please help with input about how this MPPT and SLA battery may interact as voltage and current draw change. The MPPT/PV array promises a 100 ms refresh, which I hope will be a reasonable response time as I go through a corner. If this is true and it supplies a full 5 A with a flat pedal, will the battery then supply the remaining 35 A to pull me through a corner? Then on a straight at 40 km/h, would the MPPT be supplying 5A and the battery 20 A, for example?

I plan to connect the MPPT across a 48 V series pack of 12 V 12 Ah SLA batteries. The CSB 12v battery in the link is supposed to handle 20 A for 10 min at a time for 200 or so cycles. 200 cycles is enough for me.

Battery: https://www.csb-battery.com.tw/english/01_product/02_detail.php?fid=5&pid=12

MPPT: https://makeskyblue.com/products/60a-mppt-solar-charge-controller-w-wifi

Drive rating: 48 V, 2000 W, 6.9n.m Kunray

PV panels: 4 x 60 W panels at 20 Voc, 5 A max.

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  • \$\begingroup\$ Have you tried to simulate it? \$\endgroup\$
    – winny
    Commented Feb 9, 2022 at 12:02
  • \$\begingroup\$ Yes, had a look on falstad and multisim but I have no idea how to set up the circuit, as it would need me to customise components and the parameters are way past my level. I basically just need to know if this is worth a try or if it is totally unrealistic, don't need exact numbers. \$\endgroup\$
    – frank
    Commented Feb 9, 2022 at 12:39
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    \$\begingroup\$ How about recalcualting the battery as a capacitor, the solar panel as a current source and your motor as a current sink? Should be easily doable in LTspice or any similar free SPICE simulator. \$\endgroup\$
    – winny
    Commented Feb 9, 2022 at 12:53

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Finally got to actually testing this - under a 2 amp load from a motor in parallel to the battery, the MPPT provides around 0.3 amps.

Setup:

  • 12 V x 4 = 48 V AGM
  • MPT-7210A set to 57 V, 1.8 A max charge
  • 21 VOC, 5 A PV panel on boost charge mode
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  • \$\begingroup\$ Is it intended for the MPPT to power the kart directly as some kind of solar power demonstration? Normally you'd worry about the battery powering the motor, and worry about the solar power system recharging the battery, and if the solar power system has some leftover power that goes directly to the motor, that's a bonus and not really something you need to care about calculating or measuring \$\endgroup\$ Commented May 19, 2023 at 19:05
  • \$\begingroup\$ Thanks user253, this is exactly what we're doing. The idea is that that the kart slowly charges when left outside, likely to reach full charge within 3 hours after use as we only drive it for around 40 minutes per session. \$\endgroup\$
    – frank
    Commented Nov 12, 2023 at 15:36

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