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TonyWilliams
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BMS and Energy Gauge for Dune Buggy

Fri Dec 07, 2012 11:38 am

I need some help with an electric powered dune buggy.

This machine is running now using two Warp 9 DC motors. Monitoring is via Racepack Datalink II 32 sensor system. There is not currently a good way to measure and quantify the energy in the pack to be delivered to the Datalink II. How might that be done?

The vehicle has 2 cells – each cell has 69 individual 3.305 CALB 180 Ah cells for a total of 228 volts and 41kW. There is no BMS, but I believe it needs one. Where would it start looking?

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surfingslovak
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Re: BMS and Energy Gauge for Dune Buggy

Fri Dec 07, 2012 12:10 pm

What else is on the buggy in terms of instrumentation? I have seen some DIY EVs, which relied solely on a pack voltage reading to determine SOC.

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TonyWilliams
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Re: BMS and Energy Gauge for Dune Buggy

Fri Dec 07, 2012 12:53 pm

surfingslovak wrote:What else is on the buggy in terms of instrumentation? I have seen some DIY EVs, which relied solely on a pack voltage reading to determine SOC.
Well, that was my first guess, too. Just measure volts. But with no BMS, and a $40,000 battery, really bad stuff can happen.

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DaveEV
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Re: BMS and Energy Gauge for Dune Buggy

Fri Dec 07, 2012 1:21 pm

So now you're consulting for EV West?

If EVwest isn't individually monitoring each cell in each module with a BMS module to prevent over/under voltage, I will be sadly disappointed in their EV knowledge, especially considering that on the surface they have built many successful EV conversions. Maybe I shouldn't be surprised - they don't appear to have any BMS equipment on their online shop.

Step #1: Install BMS on each individual cell - you need this for safety and so one doesn't need to babysit a pack to make sure it's properly balanced when charging.
Step #2: You'll want to monitor pack voltage as this will most easily show overall SOC. Ideally you would also see the average cell voltage along with min/max cell voltages since your pack will be empty when the weakest cell gets low.
Step #3: You need to monitor energy going in/out of the pack and start coulomb counting. Won't be perfect but you'll get an idea of how much energy you've used which one can use to correlate with voltage data.

There's quite a few BMS solutions out there for Lithium packs. I've never used any of them so I can't recommend any.

I've heard of MiniBMS being used with success by the DIY crowd. There are also more cabpable solutions such as the ones here: http://www.evolveelectrics.com/BMS.html" onclick="window.open(this.href);return false;

IMO BMS is the single most important piece of equipment for a multi-cell battery pack. This is not an area to get lazy or cheap out - especially when you have a "$40k" battery pack to protect and use.

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TonyWilliams
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Re: BMS and Energy Gauge for Dune Buggy

Fri Dec 07, 2012 1:50 pm

drees wrote:So now you're consulting for EV West?
No, the owner.
I've heard of MiniBMS being used with success by the DIY crowd. There are also more cabpable solutions such as the ones here: http://www.evolveelectrics.com/BMS.html" onclick="window.open(this.href);return false;

IMO BMS is the single most important piece of equipment for a multi-cell battery pack. This is not an area to get lazy or cheap out - especially when you have a "$40k" battery pack to protect and use.
Thanks, I'll check those out and, of course, I agree.

metricmind
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Re: BMS and Energy Gauge for Dune Buggy

Wed Jul 03, 2013 9:56 am

Would EVision work for you? http://www.metricmind.com/products/evision-2/" onclick="window.open(this.href);return false;

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