I was recently sent one of the new Tattu 1800mah 75C 4S batteries to do a bit of testing. I’ve been flying it for a week or so and I have spent some time gathering data. Here is what I’ve found so far.
To give a bit of background, I am a multirotor pilot, and am primarily interested in miniquads.That being said the testing I’ve done applies universally. These high C rated batteries are useful beyond the bounds of multirotors into the world of 3D flying, and high performance aircraft.
For this test I’ve done some stress testing (and unintentional abuse!) and general data collection with this battery, and for comparison purposes a Dinogy 1800mah 65C as well. I did a current draw test on both batteries at 25A to measure voltage drop. For now I have skipped the internal resistance test as my current tester seems to be giving unreliable results. I will post an update as soon as I get some reliable results. Finally I recorded a flight with an onboard current and voltage sensor in the OSD to demonstrate voltage drop in real world flight conditions.
As with the GensAce 2200mah I reviewed last week, my first impressions of this battery are very positive. GensAce/Tattu seem to use the same build techniques in both their lower discharge and higher discharge batteries. It has the same aluminum support that covers the battery and adds additional protection to the top and bottom of the battery. After a bit more research I have found that this actually provides compression during high discharge and according to research can significantly extend the life of the battery. Again, where the high current lines enter the battery casing they are re-enforced with additional heat shrink. The balance leads also come out the opposite side of the casing rather than the same side as the high current lines. In addition this battery has a plastic cover that extends over the balance lead cables, preventing stress on the cables when plugging and unplugging the balance cable. I will point out that on some chargers this can prevent the balance leads from fitting properly. Unlike the 2200mah, this battery came with XT60 connectors, which means no soldering for me. Battery dimensions actually exactly the same as the 2200mah 3S, and are accurate to the product description on the sellers website. The wight is just over 200g and the physical size is 105mm x 35mm x 25mm. Because of the aluminum plates the size is very consistent.
I wired the battery up to a 25A load to test voltage drop. At the top of the battery the voltage dropped mostly linearly at a rate of 0.037V per A. That leads to a projected drop of 1.9V at a 50A load.
The flight video shows a voltage drop of about 1.5V at 65A which is actually a good deal higher than the projected ratings. Granted this sag was at the top of the battery, and this was the batteries first flight, however it leads me to believe that the performance of these batteries increases as the amp draw increases. It appears to be a factor of the carbon nano-polymer used to increase the C rating.
Also it is worth noting that on this first flight test, I got a bit caught up in flying and pushed it a bit harder than I was planning. The battery came down screaming hot and a tad unbalanced at 0.10V maxium variance between cells. However after a few hours of cool down the battery was back to withing a 0.03V maximum variance. After a slow charge the battery was perfectly balanced. After several additional flights there seem to be no ill results from the abuse on the initial discharge. I am very impressed with the handling of the abuse!
Comparison Load Test
For comparison the Dinogy battery performed slightly worse with a 0.043V per A drop.
My initial impressions of these batteries both in build quality and performance are very positive. Because of the very high C rating, it is hard to get an accurate picture of whether or not this battery can fullfill a 75C (135A) current load, but given very few people have a setup that can draw that type of constant load, that’s not something we can easily gauge. Since I haven’t found a reliable method for testing internal resistance (other than the load tests above) It’s hard to get an objective measurement of true C rating. I will post an update as soon as I can test these on a more reliable tester. I can say up to 65A loads this battery performs excellently. I was also very impressed with how well it recovered from first time abuse.
The battery provides both solid performance and the extras in the build such as the reinforced cables and aluminum compression plates add up to a very nice battery. However that battery does come at a premium price compared to other similarly rated batteries. For those interested, the battery is available here: http://www.genstattu.com/tattu-1800m…tery-pack.html