Trouble making 48 volt bank from 24 volt lithiums

softdown

Thought this would be simple. Isn't working so far.
What is missing?
Always just went pos to neg for serial connections. I think. Rusty.
uld

softdown

There are two bolt holes in each “lug”. Perhaps that is consequential?

There are also “lugs” on the other side of each battery. These apparently “fake” lugs will not produce measurable voltage with my “techniques”. 

softdown

Positive note. Batteries have almost no voltage drain after sitting 3 1/2 years with no charges. Went from 26.28 volts to 26.22 volts at 38F. Impressed by that. Perhaps “automotive grade” is substantive. 

softdown

Negative note. The bolt holes only allow 6mm bolts and 10mm depth. Perhaps 15mm would fit but my next option is 20mm.
~26mm is an inch. 

Slightly less than 1/4” bolts to transfer current. Seems off. 

EDIT: Currently is likely transferred from cable lug to battery lug. Rather than bolt though some current transfer is concurrent. 

softdown

softdown

Think I figured it out. I am soooo rusty!!!

Been doing construction for past couple years. Almost ignored solar energy. 

Time to get out of construction. Youngish laborers are usually walking bad habits. Good help is taken. Time to prepare for tumultuous times in some likelihood. 

SteveK

Hope you don't mind me asking but have you worked out the BMS yet? Supremely important to have a handle on that before pressing these guys in to service at all. I saw a picture of a connector that appears to be the BMS connector. You will need to tickle that with something.

I have done quite a lot with Tesla Model S battery modules. The BMS's I have used are Orion, Batrium and Thunderstruck. My favorite by far is Thunderstruck (Dilithium Designs). It is dead dog simple, automotive quality reliable and scalable beyond all others especially in parallel fashion.

You wrote:" Youngish laborers are usually walking bad habits. Good help is taken. " I hire a fair share of plumbing and electrical contractors for my business. When they get a new apprentice out of trade school I am sure to tell them that, one day, they will rule the world.

softdown

I bought BMS when I bought the batteries. Forgot EVERYTHING.

Need to dig them out and install. I have some time. 6am voltage is about 49.2 these days. Not good but somewhat tolerable.

Running old batteries until they are pretty bad seems acceptable. Good back up genset 

softdown

Are the BMS lugs those featured in top right of most recent pic?

Measuring no voltage with those lugs. Yet they must serve a purpose.

SteveK

No, the BMS connector appears to be in another post you did titled "Hooking up these lithiums". It's on the left side of the picture.

SteveK

This video will help you. https://www.youtube.com/watch?v=pcatgGpdE9o

It's an 8S so I'd probably consider the Overkill Solar 8S 120A BMS as long as my power requirements were low enough . I always go much larger current ratings as it works the BMS less. I've used it, it works reliably, it's not my favorite but it is worlds better than riding those packs bareback like you are......

With the Batrium, Orion and Thunderstruck you need to provide a disconnect. The Overkill has this already. It can switch the battery out of the circuit if there is an event. I don't like mounting this type of BMS as shown in the video above. This type of BMS can fail in a cloud of smoke, heat and possibly flame. Some separation is preferred. 

That is about all the help I can offer. Be well, be safe!

softdown

"worlds better than riding those packs bareback like you are……”

Never hooked them up. Thinking about it.