I’m looking to connect the batteries together. I don’t need the JST connectors. I already have 2 batteries configured as a “MASTER” for each of the two strings for balancing. I’m using the few BMS connectors I have now to balance the batteries as needed. I would like to have a full harness that connects the batteries in each string together to eliminate having to move the harness around.
I am OK with buying connectors and putting the harness together myself. No problem there. Otherwise I’ll need to measure the distance between all the connectors to get the harness length correct.
First picture is 3way to jst and one splitter.
All wires are 500mm long pin to pin.
Bottom picture is a 2x6s to 12s adaptor that I made from wires shown.
I have more of the type on the right. Only difference is which wire is double.
Double female on right. Double male on left. Both do the same thing.
I don’t know how many spare housings I have but they are common computer psu type.
The connectors have arrived and I’ve started building the harness for my batteries. So far things are looking much neater than using the factory pieces.
The pack is working out great. I’ve been using between 6 and 10kw/hr of power from it daily. My normal cell voltage swing is 3.85 to 4.04. The cells are staying very well balanced. It must be working OK since my power bill last month was $52. In years past its been in the $120 range during this time of year.
The BMS is a Batrium WatchMon 4 setup. I have mixed emotions about it to be honest. I like it from a conceptual level but I’ve found some issues with build quality and calibration of the individual cell monitors. I had some issues with a firmware bug that caused the watchmon to lock up on a weak wifi signal leading to an over-discharged pack and swelled cells. This was during my initial capacity testing of the individual packs.I was less than happy with that situation but relieved it was only one pack. When I reached out to Batrium they were not very helpful other than to say, Yea, we know about that…
Assuming the graph shows up in my response you can see the battery output compared to the PV input. The energy level ramps up starting in June due to adding a window AC to the mix to help keep the house cool.
@Cmed wow that is great! Your pack will last “forever”. I am amazed with my pack being almost 8 years old (from two 2011 Volts) at how well the capacity has remained. I think a lot has to do with how they were designed - support huge charge and discharge scenarios vs. the easy life now in handling only a 3~4kw load from my inverter. I would love to get another pack to help out on my discharge range due to overall demand. That way it would help cut down on my cycle count.
As of now I have not used a BMS, I have been managing the high and low cut off through the inverter and charger. Has worked great so far but something that I plan on looking at in the future. Usually my cells are spot on with a couple being within a hundredth of each other, 3.80 vs. 3.81. Chalk it up to some of my wires being slightly longer / shorter.
I am looking to get a new inverter. Looks like you from your earlier post you are using a Schneider product? How do you like it and how are you setup?
I do like the Schneider gear. I have the 6848 inverter and the MPPT 150-60 charge controller. I have 3.4kw of solar panels out in the yard.
The power system at the house has been divided into two segments. The main panel carries all the high current loads like the central AC and ovens. I have a second panel with all the inverter loads. That is the fridge, lights, well, computers, etc.
If the batteries go down to the minimum I have set in the BMS the BMS closes a transfer switch on the input side of the inverter. The inverter is programmed to prioritize utility power so once it sees the utility available for 5 minutes it changes to PASSTHROUGH mode. When I have sufficient battery power available the BMS opens the transfer switch cutting the input power to the inverter. With this configuration I am not operating in parallel with the utility. I’m either on battery or on utility with the critical loads panel.
The connectors are MOLEX 5557 18P. They are not the exact mate for the batteries but the pin spacing is correct and the connectors make good contact. There is no retaining clip so they will pull right out if you tug on them. Not really a problem but something you should be aware of.
The main harness is made from 18 gauge silicone insulated 200 degree C wire. I used a short piece of 22 gauge silicone 200 deg C wire to connect the harness to each battery connector. The 22 gauge acts as a fusible link in case something was to go sideways.
During normal use I measured the amperage around the harness to see what was happening. I did see some energy moving around during charge and discharge. The readings were in the tenths of amps.
In addition to having the batrium connected I also spot check the batteries with a VOM. I wanted to make sure the connectors are reliable. So far so good.
@Cmed
I assume you are not using inverters at the panels (I.E. Enlighten)? I am looking into this but I have straight AC coming off my panels into my main breaker box so I have figure out how to get from AC to a DC charge controller to the batteries and back to AC when I need it.
Correct. Panels, charge controller, and batteries are all on the DC side. I use some DC power directly and I’m considering putting in a 48v mini-split heatpump. They are still a bit pricy for the amount of cooling you get so I’ve not done it yet.
I have read about systems that are AC coupled and I can see in the Schneider software that it is set up for that but I went the more conventional route.
Thanks - yea, I love my system (9kw) but the AC coupling makes things a little more complicated. I have yet to find someone that has either done it or knows about it. But I have not looked that hard either.
