I finally took the plunge and purchased 8 x 3.2v 200ah cells from RJ Energy direct from China. They weren’t the cheapest or the dearest cells that were available, however they were easy to correspond with via emails and they had a good understanding of English. Payment was made with Paypal, which added a 5% surcharge, although it gave me peace of mind when dealing directly with China, just in case something went wrong. Everything went well and the cells arrived within 5 weeks inside 2 solid cardboard boxes, with 4 cells individually wrapped and well protected in each box. They were all exactly the same voltage, something that indicates that they are well matched cells.
The first step involved before installation is to top balance all the cells. There are lots of Youtube videos explaining this process. There is also lots of discussion whether to top or bottom balance cells before use. Another video explaining top balancing.
I hooked them all together with 14 busbars and charged them in steps to 3.4v, 3.5v and finally 3.6v. Using a Variable 0-30v 0-10a power supply, this was going to be a slow process. It took over a week, with the initial part of the charging process being very slow, charging at around 7amps while I could keep an eye on everything, dropping it down to 2-3amps overnight. The voltage from 3.45v to 3.5v was a little quicker, while the voltage rose very quickly to 3.6v. This last stage needs to be monitored very closely, as run away voltage can quickly destroy a perfectly good cell with cell bloating, leading to an almost non recoverable fatal cell very quickly.
I swapped out the 6mm bolts for 25mm long grubscrews with nuts. This allows to undo the nuts when doing modifications instead of the bolts. I have done this to stop stripping out the aluminium thread in the top of the battery, which are probably the weakest link of these type of battery
As of December 2020,I have had the Batteries installed for over three months now, the process was a little daunting. The initial charging them to top balance was a very slow process, however this is not to be rushed. I have never done this before, however I have watched lots of Youtube videos and read about lithium batteries on lots of forums.
There is lots of negative feedback out there and different people do different things. I am taking a conservative approach and have my charging limited to 13.8v. This is approximately 99% of full charge and as yet the BMS has kept the cell delta (difference between highest cell and lowest cell) very low and I have not had the BMS trip out the battery pack out, except while testing to make sure everything works as expected.
While I have the batteries installed, some adjustments and alterations are to be expected as I monitor them into the near future.
Chris and Dianne's Ultima adventure 