It’s Electrifying
As non-stop rain and heavy showers batter the South East and with space at a premium in the van, we took the decision to move inside and work on getting some of the electrical parts of the build up and running. We’ve waited with anticipation to start the electrics and we’re hoping that our many hours of intense research will pay off. This post will mainly be a quick run through of Ben and I setting up stage one of the electrics. We plan to publish a more in-depth article on this subject shortly, which will outline the plan, the equipment used and any complications we run into along the way. For now, lets get electrical!
Wiring up the Inverter
As per our previous post we’ve decided to use two Tesla car battery modules to power our new home on wheels. Whilst there are lots of benefits to using these batteries, it’s still not the widely done thing. Never ones to shy away from a challenge we set about a gruelling couple of months of research, not only learning electrics but gaining understanding of the temperamental batteries. We found this took longer than previously imagined because there is simply not a lot of in-depth information on the web about the use of these particular batteries in such a set up. Sure there are some great blogs out there but they tend to not get into the real meaty parts of the install and the majority seem willing to risk their safety by not installing an appropriate BMS (Battery Management System).
Over the past couple of months, with our research complete, we slowly began ordering in the components we’d need in order to get up and running. Once the orders began arriving thick and fast it was time to unpack some of the main components. Unfortunately, it was at this point we realised that our transformer had been dropped, either at the factory or during transit. We were both disappointed, especially as neither the outer box or internal protective packaging showed any signs of damage. Given the expense of the item, it was not great news.
Not a great start to the day but still wanting to get some of the electrics up and running we decided to put the transformer aside for the moment. We do not feel comfortable connecting it to our system, in case it has been damaged internally. In a bid to keep the day moving forward we re-hashed the diagrams, updating the plans and temporarily removing the transformer from the install. This made things simpler and it will not be too much hassle to add it back in later. For now we prepare to charge the batteries up from mains power.
We got stuck-in making up cables, starting with the mains to inverter (left side of diagram) we used 6mm² (per core), 3 core tinned copper cable to connect from the plug to the inverter. We then moved across the diagram to the remaining cables. For all the cables from the inverter/charger to the busbars and on to the batteries we used some beastly 50mm² (1/0 AWG) tinned copper cable. It’s pretty difficult to cut such thick cable and crimp the lugs onto the end, I would highly recommend a hydraulic crimping tool for this task unless you resemble Popeye! After preparing the cables to the estimated length we sealed the lugs on with heat shrink wrap. Having never done anything like this before I was exceptionally pleased with our progress.
Next we confirmed that we had all the software for both the inverter/charger and the BMS installed ready on to a laptop. At this point, we decided to quickly plug the BMS into the batteries, firstly to set-up the parameters for the systems and secondly to check their state of charge (SOC). Upon doing so we were extremely alarmed to find that the batteries only had 36% charge left. Due to a limitation with the Victron inverter firmware, the inverter is only able to start charging the batteries if they are above 20.4v, meaning that if they dropped down by another 2.5% we would not have been able to charge them.
With this worrying discovery, we knew we had to get the batteries connected and charging today. After attaching all the cables we’d made we faced the nerve-wracking task of going live. Taking small steps, we decided to only power up the inverter to start. After double checking that the isolation switch was set to the OFF position, thus ensuring that NO power from the mains and consequently the inverter, would pass through to the batteries. We gingerly flicked the mains power switch on…. and hey presto! The humming noise of the inverter kicked in and as the lights began to flash, we anxiously stood there waiting for it to complete it’s start up. With the inverter now settled and working as expected we were in business. It was now time to connect the inverter to a laptop and set-up the charging parameters for the Tesla batteries.
This part was relatively quick as we’d spent the previous afternoon scouring the web for appropriate settings and researching to fill in the blanks where there was no direct information. Now the information was set it was time to unleash power throughout the rest of the system and get charging the batteries. I nervously switched the isolation switch into the ON position, desperately hoping not to receive an electric shock, whilst Ben monitored the data on the laptop. We were soon getting the numbers back the batteries were starting to charge and I remained shock free! A successful first day of electrics, with many more to come!