Mars Hydro FC-6500 Review

This is an updated review for the newest version of the Mars Hydro FC-6500 that I tested in January 2023. I originally tested the first version of the FC-6500 in January 2021. There have been several updates since I first tested it. Most importantly, the power draw has been increased significantly. The model I tested in 2021 pulled 621 watts from the wall. This updated version pulls 710 watts. The added power allows the new FC-6500 to fill in a 5×5 space with even denser light.

The Mars Hydro FC 6500 is a sleek and elegant fixture with exceptional performance. I am impressed with the efficiency, coverage, and the design. The FC series have sleek thin aluminum ribbed LED bars connected to aluminum frame pieces. The FC-6500 folds to accommodate shipping and storage.

Mars Hydro has two lines of LED bar fixtures: The FC series and the FC-E series. The FC series is the top end and features Samsung LM 301b full spectrum diodes along with Osram 660nm diodes. The updated FC-6500 has a total of 2688 diodes, which is 3.79 diodes per watt or about 0.26 watts per diode. It is an excellent number of top end diodes. The driver on the new FC-6500 is branded as Mars Hydro and Manufactured by LG LED Solutions. Mars Hydro has been using these self-branded drivers since 2022. They have performed well.

For the first test, I recreated the official test from my test with the original FC-6500 2 years ago. In a 5×5 test area the original FC-6500 hit a maximum PPFD of 1000µmol/m² at a height of 41.5cm (16.5in). I hung the new fixture at that height and the maximum PPFD went up to 1063µmol/m². This is to be expected since the power draw was increased by almost 90 watts. I am more impressed that the average PPFD went up by 92µmol/m² and the lowest corner PPFD went up by over 100µmol/m². As you can see, the new version of the FC-6500 creates a significantly better PAR map with much better densities around the perimeter. Also impressive is the fact that the power draw and the density along the edges went up while the efficiency stayed outstanding. The new version essentially ties the original with a Photon Efficacy of 2.37 µmol/w in this test.

Although the comparison is interesting, 41.5cm is too low to hang the new FC-6500 for our official stats. I test lights with a maximum PPFD of 1000 µmol/m², which is safe for growers without supplemental CO2. For the new FC-6500, the minimum hanging height in a 5×5 space at 100% power is 48cm (19in) above the canopy. That is the height where I measured a maximum of 1000 µmol/m² and ran the new official PAR and ePAR tests.

The new official tests have excellent coverage and great densities. In the PAR map, the corners are all in the 490s and most of the map is in the maximum production zone above 700 µmol/m². In the ePAR map, the corners are well above 500 µmol/m². The ePAR test measures all of the PAR light plus far red light from 700-750nm. The numbers in these tests show that 4.8% of the total flux put out by the FC-6500 is far-red light.

The Mars-Hydro FC-6500 can fill a 5×5 grow space with high density light. However, growers may also want to run it in a 4×4 grow space with or without supplemental carbon dioxide. I ran several tests in a 4×4 area and the results were impressive.

First, I set the hanging height to 30cm (12in), and ran a test at 100% power. This test had a maximum PPFD of 1257 µmol/m², which is ideal for grows with supplemental carbon dioxide. The uniformity of coverage at this height is remarkable. In the ePAR range, the entire canopy except for one corner is above 1000 µmol/m². Uniform coverage at that ultra-high density is exactly what you are looking for if you want to take advantage of supplemental carbon dioxide for your grow space.

Grower’s without supplemental CO2 can run the new FC-6500 in a 4×4 tent, but not at full power. I ran a final set of tests with the set-up that I would use if I ran the FC-6500 in my 4×4 tent. I hung it at 36cm (14in) and dimmed it down until the maximum PPFD was at the 1000 µmol/m² limit. The dimmer setting was at about 80% and the power draw was 565 watts. The PAR and ePAR maps from these tests are excellent.

The original Mars Hydro FC-6500 impressed me two years ago, but this new version is significantly better! They increased the power without lowering the efficiency. In both 4×4 and 5×5 test areas, the new FC-6500 gets above 2.4 µmol/w in the ePAR range.

The Mars Hydro FC-6500 has an excellent distribution of light, even at low hanging heights. For grows with supplemental CO2, it can cover 16 square feet brilliantly. For growers without supplemental CO2, it can cover 16 square feet at 80% power or 25 square feet at 100% power.

The FC-6500, like all Mars Hydro fixtures, comes with a continuously variable dimming box attached to the driver. The dimmer will come in handy for almost all growers, so I tested it. As you can see, the fixture dimmed more than expected based on the apparent dimmer setting. However, the relationship between the power draw and the PPFD/ePPFD are as expected. For accurate dimming you should measure the power draw and not just depend on the dial position.

Finally, I measured the surface temperatures. Surface temperatures are important because they can affect the efficiency and longevity of the fixture. However, surface temperatures are not directly related to the amount of heat that the light will contribute to the grow area. The FC-6500 ran remarkably cool. The hottest temperature I measured on the LED bars was a mere 38.8C (101.8F). The driver was more typical at 53C (127.4F).

The Mars Hydro FC-6500 is a top end light at a great price. Use discount code CCFC on Mars-hydro.com for the best deals. I measured 1740 µmol of usable light, which gives the FC-6500 a cost efficiency of only $0.41/µmol. This is an incredible price for a fixture with these components, capabilities, and performance.