[F16bmathis]

Hey,

Just bought 46 Thundersky 160 AH's and did an initial charge in parallel with a small (5A) hobbie charger. Charged them several times and got a finished voltage of 3.4.

Now the batteries are in my truck and I have gone 60 miles (30 charge then 30 more) with them. I'm charging them with my Manzanita, which I had set to show full charge when I first put the batteries in, then increased the voltage some as a friend (with 200 AH Thundersky's) said I should be charging them at 170V. It actually reads about 160V when charging.

They read 3.4V when I started, but now they are reading 3.4, 3.47, 3.5, 3.48,....

So... Before my BMS shows up, should I stop using the truck?
What voltage should they read fully charged? I'm hearing 3.2 to 4.0!
With the Manzanita charger, should I set it to read 170V when charging (which means the end voltage will be higher)

 

[gdirwin]

I also have 46 TS cells (but 200 AH). The nominal voltage is 3.2 V per cell - this is in the "flat region" which is where most of the energy is.

TS tells you to charge up to 4.2 V per cell, but most people do not go this high. I have set my BMS to stop charging once each cell is at 3.8V (there is little energy above this).

A key factor is balancing - if every cell is balanced perfectly, then your peak voltage would be 3.8*46 = 175V. Once you get fully charged (and balanced) then this is what you would set your charger voltage limit to (ie when the current has reduced to zero amps).

It seems your pack may not yet balanced - if you are top balancing, then all voltages should be the same. I see you put all cells in parallel and charged them, but you should have gone to a higher voltage (say 3.8 resting volts). You may be best to manually balance each cell - you can get get most of the charge into the cells by charging with all cells in series, then disconnect the charger (Manzanita chargers are not isolated from the AC mains!) and manually bring each cell up to the same resting voltage with a DC power supply - you can also discharge the highest cells with a load... If you rely on the BMS to balance, it may take a long/long time, depending on the wattage of the balancing resistors.

Rember the CV/CC concept - initially the charger will keep the current constant - then once the pack voltage hits the limit you have dialed in, it will keep that voltage constant and reduce the current, ultimately getting to the desired voltage and 0.0 current - if you have 3.8V per cell at 0.0 current (resting voltage) then you got it right. Without a BMS perhaps get each cell to 3.7V - it rises quickly!

I would keep the charger limit voltage much lower until your BMS arrives - do not let any cell get above 4V! This happens very quickly - once it is past the flat region, the voltage climbs quickly. I would set a very conservative voltage limit on the charger, and initially charge with a very low current until you can set the voltage limit... As your pack gets balanced, you will get more and more energy out of it...

 

[F16bmathis]

Sounds about right. Thundersky's data sheet says 4.0V (charge). My biggest problem is I only have one BMS unit. Bought it to see what I was getting and now I can't find where I bought it from! Really neat though, sealed, had a green led light up when I placed it on a battery while charging. I think it was from ElectricBlueMotors.com. Though I do like the BMS system from MINI BMS - looks like it'll shut off the charger when the batteries are done, but I gotta look into it... But I like the pretty green LED on the other one...

P.S. A Manzanita is probably not isolated as I shocked myself with 220V yesterday touching the trucks ground and the positive 144V that is disconnected from the pack. (But is connected to the Curtis 1231C) So how I got shocked is still a mystery to me.

 

[F16bmathis]

I should've also mentioned.. My BMS is from energetech.com. I was told its a BMS, but I don't think it really is. When I had a link to the manual or site, I didn't remember anything that actually said it was a BMS, thought through e-mail I was told it is. All it really seems to do is display battery voltages and a fuel meter, ect through a touch screen display.

Why do people not advertise thier products better? I found these items before, I should be able to find them again. I gotta start using just one computer and save a link!

 

[F16bmathis]

I guess I'm going with the Mini BMS. Pretty sure the touch screen display I bought will not function as a BMS, and the Mini BMS will turn off my charger.

 

[Overlander23]

I just went through this with a new pack... balancing, etc... with TS160s. I ended up final charging all the cells in parallel to 3.8v and left it there for a bit (using a constant voltage power supply). The thing is, the knee of the charge curve is 3.6v, so unless you balance at at least 3.6v your cells could still be unbalanced.

When I received my cells all 64 were reading 3.31 volts. But as I charged them in series (just to speed things along), a few cells were hitting 3.6-3.8 much sooner than the others. So while it all looked balanced at 3.31v, they really weren't. The charge curve is so flat at 3.3, 3.4 volts that it's not a good indicator of capacity. I think you really have to get to the knee, 3.6v, before you can truly say they are, for all intents and purposes, full and balanced.

What you'll notice is that per cell voltage rises quite rapidly after 3.6v.

 

[dimitri]

Don't increase your charger's voltage until you get MiniBMS installed. The reason your cells have various voltages is because you stop your charger right around the time most cells are at the "knee" voltage. In this area cells would vary the most, but its perfectly normal. If you increase the charger voltage now, there is a chance a first cell can get too high while others are still catching up.

Sounds like you did a good initial balance, so once you install MiniBMS you would crank up the charger and they will all line up at the pack voltage around 170V-175V.

Please carefully follow install instructions to avoid damaging the last module. Also, with Manzanita being non-isolated, extra attention must be paid when wiring up the cell signaling loop, if any signaling terminal touches any cell terminal it will likely damage one or more modules.

Once MiniBMS is installed make sure to test the charger control via REGBUS interface. Only if you tested BMS ability to stop the charger you can rely on it later on during daily charges.

 

[F16bmathis]

Ordered the Mini BMS earlier today. I'll heed your advise and take my time. I've been driving the truck only 15 miles a day, then letting it charge to the 3.4V per cell setting it at currently. They were sorta all over the place right after charging, but this afternoon, they seemed to settle to around 3.4V +/- a little.