Direct Solar Charging

For the non-millennials amongst us, it is hard to appreciate or internalize how fast and far solar panels have progressed in terms of performance and price. It is without a doubt the cheapest form of energy now. In fact, in terms of kW of power, for approximately the same price as a typical 8-10kW forklift charger, you can buy over 10kW of solar panels. However, the balance of system (BOS) adds a relatively large proportion of the cost to any renewable energy installation, in terms of electronics, MPPT, inverters, certification etc needed. Balancell, however, has found a way to minimize these BOS costs.

Firstly, the realization that solar power is now so cost-effective, the panels do not have to be optimized for maximum power. The second realization is that if solar panels drive a constant voltage source at the correct voltage, you can get most of their power out anyway. If we can match panels approximately to the battery voltage, then we do not need an MPPT. A 52V Balancell battery charges for most of the time between 54 to 56V. If we take a standard 60 cell solar panel, their maximum power point voltages (Vmp) are around 29 to 32V. Two of these panels in series gives ~62V. Taking this 2-panel series string and driving it directly into a 54V battery gives approximately 55/62 *100% = 89% of the maximum power available, without any MPPT.

Connecting panels directly to the battery reduce the cost considerably and is a very robust simple system. The battery itself, however, must have the ability to regulate its own charge and stop charging when full. This functionality is already built into the balancell battery.

A 270W panel has a maximum power point current between 7-9A, hence 2 of these panels in series will achieve approximately 8A of charging into a 52V battery. To achieve more current, simply add in parallel as many of the 2-panel series strings as you desire. The kit we are offering has 26 panels, giving 13 series strings in parallel, giving up to 13 x 8 = 104A of charging current.

Safety notes! With only 2 panels in series, the voltage is low enough to fall beneath various safety standards, and the panels should not arc when unplugged. However, caution should still be exercised, polarity checked, and wire lengths and loops kept to a minimum. In addition, with more than 2 panels in parallel, the possibility exists for reverse current to flow, and parallel connection should be either done through diodes or appropriate fuses.

Lastly, this solution is not a one-stop-shop for all applications, but there are many applications where it could work well on its own. Any business that only uses a forklift a few hours a day, and can leave it on charge for the rest of day, should manage. Night shift only applications would be ideal. In distribution centers, it could work well in combination with conventional chargers. The solar charge stations used during the day, and conventional chargers used at night.

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