I purchased 4 UT-1300s through the Costco deal on Lion Energy Lithium Batteries. Per the Lion Energy manual you are limited to (4) 12v 105ah batteries wired together. I was hoping to expand my system to a total of 8 batteries and wasn't sure the best way to do this-if even possible.
I may have just answered my own question after re-reading the manual. There is a limit on connecting 4 batteries in a "series" for 48v. I understand this. However it seems as though there is no limit on connecting any number of batteries in parallel, is this correct?
To better answer your question, it would be useful if you described your current system, before expansion. What voltage is your current system running at? How are your current batteries wired up?
I haven't assembled my system yet but did start to mock up my battery compartment etc.to realize that I have a bit more room than I initially thought. I had (almost) always planned on a 12v system with copper bus bars to connect all the batteries. Would there be any balancing advantage over the life of 8 batteries to run a higher voltage?
Finally, I'm collecting various batteries of the same make, model, and manufacturer but DIFFERENT production dates. Given they have never been put into service, "how old is too old?" If I'm using unused units from a year ago, should I put them in a certain order within the bank or avoid it entirely?
The production date question depends as much or more on whether the older batteries were stored properly as per manufacture guidance (storage voltage, periodic recharge to stay within nominal voltage, no deep discharge events, temperature limits) than chronological age (within reason). Likely the older the date the higher the chance they were not properly stored/maintained? Make sure they are all individually and fully charged & @ the same multimeter-measured voltage before starting to wire up.
In an 8 parallel topology, the voltages will be the same. There are several parallel wiring topologies that help keep the battery’s lifecycle wear profiles similar over time when using higher #’s of batteries in parallel. Victron’s (free) Wiring Unlimited book is a good resource. It does not say in the manual but ask Lion about up to 8 of their batteries in parallel as the limit can be manufacturer specific.
Add up your KilowattHour / AmpHour demand for your intended use to figure out what kind of capacity you need for a reasonable runtime between charge cycles and how much time you will have to complete each charge cycle. Consider your charge source(s) and their practical runtimes in your environment to bring the battery bank up to 100% SOC. No right or wrong answer but more is not always better.
12, 24, 48 V depends on your intended use and the requirements of your loads. 12V keeps it simple from a voltage balancing perspective. Higher voltages of series-parallel will cut down on your wire size requirements but, as you say, introduce voltage balancing considerations.
