# Might go without the BMS



## kchiangusa (Mar 28, 2012)

Hi sabahtom,

What are you using to monitor your pack then? I also chose to do simple monitoring of my cells with manual bottom balancing. But I put together a quick measuring device using cell log 8s. It takes less than 2 minutes to measure the 45 cells that I have.

http://blog.mr2ev.com/?p=871

Ken


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## sabahtom (Mar 1, 2011)

Hi Ken

I haven't been able to get a reply from the manufacturer yet, but it might be that my BMS is internally fused in which case I will use it after all. Your idea sounds great though, I'll check it out.


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## kchiangusa (Mar 28, 2012)

It would be great if they are internally fused. That's a smart move. What brand BMS do you have?


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## sabahtom (Mar 1, 2011)

I called China Hipower. It's not internally fused and the circuit diagram in the manual doesn't mention fusing it at the terminal either. I told them to fix their manual.


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## kchiangusa (Mar 28, 2012)

sabahtom,

That's a bummer! It is definitely safer to have a fuse near the battery terminal for the BMS connection. I use a 1/2amp fuse and fuse holder for my setup and it has worked really well. Yes, I agree soldering the fuse on each individual lead and heat shrinking will be very time consuming. 
I have an idea, I've use these Wago connectors before and they are really great! Super easy to install, just cut the wire, strip, and insert into the levered holes and engage the lever. I have a friend that works for Tesla and supposed they use these for prototyping and such and the connections are solid. Check it out for yourself. If I do another conversion, I think I will use these instead of soldering the fuses.

http://www.amazon.com/gp/product/B0...rder:none !important; margin:0px !important;"

Good luck!

Ken


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## sabahtom (Mar 1, 2011)

Thanks they look nifty. How do the fuses connect to the wago? Looks like they still need to be soldered to a wire, then joined in the wago to the BMS voltage tap?

I heard that using fuses on the terminals can make the V reading unreliable on BMS. Have you got any idea about that?


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## bruceme (Dec 10, 2008)

Why don't you just solder an inline radial fuse?

2Amp inline fuse

...and shrink tube of course.


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## coulombKid (Jan 10, 2009)

EVTV.me and a graduate thesis in Europe generally confirm what us old-dogs have suspected all along. Top balancing is a looser. Bottom balancing on a periodic basis is what I will do. I like the Cellog-8 idea. I most likely won't ever charge above 3.6 volts/cell. 
I like to be able to see which cells are charging up too fast (loss-of-capacity) so I can get them out of the string before the next PM scheduled bottom balance. As Jack says: "when they swell, they tell." A top balance system will prevent overcharging but gives us a false sense of security when it comes to age and usage related degradation. 

Yes I am going to EVCCON this year.


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