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Old 04-20-2018, 12:10 PM   #21
Goliath
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Default Re: Lithium Woes - How to avoid house fires!

I got the 72 AH 48v kit.
I bought it in January, as they have an end-of-year sale every year and it is $250 off the regular price.

I paid about $2,200 for everything, which is very reasonable for a complete system, and I've read good things about the LithiumBoost system.

I've heard the price went up a little, but that could just be a rumor. You can email Tsipi (Sam's wife) at tsipi.landen@lithiumboost.com and she's pretty quick to reply with a quote.

I don't endorse their system, as I haven't used it yet.
I will say that so far, they have been excellent at communication, and the owner is sending me a whole new BMS and 5 new cells for that row.
As long as they follow through, I would do business with again.

An interesting aspect of their system, which I'm not sure other systems have, is their management of power cutoff. What I mean is that they have a proprietary harness that comes off the BMS that goes to the ignition switch. There are two other wires that go to the original ignition wiring. When the BMS detects the batteries are getting low enough to do damage, the BMS sounds an audible alarm. If kept driving too long, the BMS takes control and cuts off the cart. After that, there's some kind of mode to re-enable the cart for another mile or so, but it's designed to prevent an under-volt situation.

Not sure if that's present in other BMS systems, but thought it was handy.

@CrazyDad - BTW, wifey does know what I paid for the BMS system. There's just many "extras" that I decided to do, like motor, controller, lighting kit, etc...
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Old 04-20-2018, 09:04 PM   #22
BobBoyce
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Default Re: Lithium Woes - How to avoid house fires!

Looks like a great project Goliath!

As you probably know, the primary issue with most lithium systems that suffer catastrophic failure are due to cell chemistry. I'm glad that you chose the LiFePO4 cells, otherwise your cell/BMS failure would have had a very different outcome. Way to go man!

I bought 100 A/H GBS LiFePO4 cells and will be doubling them up for a 200 A/H 48V pack. My project was sidelined due to weather, and waiting for more cell jumpers to arrive. The guy I bought from recommended that I double up on the cell jumpers since I'm doubling the A/H capacity of the pack.
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Old 04-21-2018, 11:11 AM   #23
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Default Re: Lithium Woes - How to avoid house fires!

Here is an episode of an unbalanced & overcharged Nissan Leaf pack. Here is the story. Nick, at EV Battery Center, had given me a way to rescue a pack that had been over discharged by a neglectful owner.

I used Nick's method on two packs of owners who left key on and not plugged in for a week. Each 58V pack had drained to a total pack voltage of right around 3.8V. Not a typo. So, per Nick, I used a 36V lead acid PowerWise charger (control board bypassed) and connected it directly to the pack. In about 10 minutes, at 23-25A, it picked up enough voltage that I could reconnect the Lithium charger. It completed the charge, packs now have same range as before, no damage and owner learned a lesson. This is possible because the cells remained balanced, even at the low voltage. These episodes happened a year ago.

The pictures attached depict what happens when a pack is left unconnected to a charger for 6 months, with the BMS eventually draining the pack to 0V. It would not even move my Fluke digital voltmeter. So, I used the same rescue method on the pack. Once the Lithium charger took over, I left it to complete the charge. Hmmmmm...

BUT, then I talked to Nick about the 0V rescue. He told me he hoped this rescue would be OK because from 0V, he was only able rescue dead modules with an RC charger, using a long slow charge on each individual cell. He had failed to mention that to me for rescue of a completely dead pack. OOPS

So, as the charger pushed the current through the cells, they were no longer balanced. The BMS could never start to operate. The BMS does not control the charger; it has a programmed shutoff voltage. But, the BMS can shut off the charging, when it is operating. Because the BMS had no control of the charging process, the result is in the pictures.

There must have been a pretty solid BOOM, but no one heard it. He only noticed when he went to use the cart week or so later, still on charger ( though it had shutoff). But, as soon as KS on, pack voltage would drop rapidly and he could not drive it. Then he called me.

When the cart was brought back to me, pack voltage was still about 54V nd these pics are what I found.
Pic 1 - BMS end of pack, side plate should be flat. You can see the expansion.
Pic 2 - Power end of pack after bus bar removal, same expansion.
Pic 3 - Two threaded rods removed, expanded so fast when the nut came off, it knocked the battery drill from my hand.
Pic 4 - The two most expanded cells. No leakage. Nothing. Just damaged beyond recovery, except they still read about 3.7V per cell.
Pic 5 - Replacement pack. Jon won't forget the charger again.

Can Nissan leaf cells catch fire, NO and it is a good thing because of this episode Jon & I experienced. Watch this video produced by Nick at EV Battery Center.

https://www.youtube.com/watch?v=Jz37WycW-7E

Description under the video by Nick. A used battery from Nissan Leaf, 3.8V 33Ah, tested for how likely to catch fire when is destroyed or in flames. We had no success making it burn. Same battery after the burn test was charged/discharged twice at 1/3C - 10A - it has 30Ah capacity remaining. Before the test this cell was under salty water for 2 hours - you can see the contact are destroyed.
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Old 04-21-2018, 12:28 PM   #24
Gazoo
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Default Re: Lithium Woes - How to avoid house fires!

Quote:
Originally Posted by Goliath View Post
Finding that cell swollen freaked my s**t out. After my wife's story about our neighbor, I'm thinking it's gonna keep growing, and my house would become the China Syndrome (an old movie for the younger crowd - Google it).

After I calmed down, I decided to remove it, to see the extent of damage. Luckily, I had installed foam all around the inside of the box, to dampen vibration. The cell had swollen so much, it compressed the foam, then proceeded to push the plywood box outward about 1/2".

It took an hour to get the cells out of that end row. I had to pry a middle one out sideways with a plastic auto trim tool, and broke 2 tools doing it.

I included a pic of a good cell, for reference.
Keep that swollen cell, I think its pregnant!
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Old 04-21-2018, 02:01 PM   #25
ThreeCW
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Default Re: Lithium Woes - How to avoid house fires!



Your picture 4 looks like an inflatable vehicle jack (https://www.youtube.com/watch?v=sWTrBq9iT_g).

Thanks for sharing this experience ... it looks like lithium batteries certainly can not handle the abuse that lead acid batteries can be subjected to. Abuse a lead acid battery and you might have to buy a new one. Abuse lithium and you can introduce a whole new host of problems ... and potential dangers.

I am (was?) considering lithium for my upcoming battery replacement ... but am now rethinking that from a safety perspective, lithium might not be the right product (for everyone?) in a hobbyist application such as a golf cart.

There are lots of advantages to lithium ... this thread certainly points out some of the risks that need to be understood and managed correctly for successful lithium use.
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Old 04-23-2018, 07:34 AM   #26
PingEye3
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Default Re: Lithium Woes - How to avoid house fires!

Please read the entire write up and watch the linked video before letting any panic set in on Nissan leaf modules. Basing the fear merelly by looking at the pictures attached and not reading everything about the episode, is premature. They are very safe.
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Old 04-23-2018, 10:11 AM   #27
cgtech
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Default Re: Lithium Woes - How to avoid house fires!

This sort of thing is why I always suggest a Battery Management System. I don't subscribe to the "well, my batteries can do without a Bms" theory. And, yes I did read the whole thing.
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Old 04-23-2018, 08:58 PM   #28
PingEye3
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Default Re: Lithium Woes - How to avoid house fires!

It had a BMS.
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Old 04-23-2018, 11:30 PM   #29
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Default Re: Lithium Woes - How to avoid house fires!

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This sort of thing is why I always suggest a Battery Management System. I don't subscribe to the "well, my batteries can do without a Bms". And, yes I did read the whole thing.
I did read it, and I never said all scenarios could be prevented. I believe the Bms should have stopped the charger as soon as the balloons went outside normal parameters if it were active, which would have prevented this, shouldn't it? If the BMS cannot protect cells from overcharge, it's not a BMS.
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Old 04-24-2018, 08:49 AM   #30
Sergio
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Default Re: Lithium Woes - How to avoid house fires!

Goliath had the charging issue, PingEye3 had the discharge issue, but both are examples what I called "flawed safety protection systems".

It is not enough to have a BMS, it needs to be properly wired so it can disconnect the load or the charger in case of a single cell failure.

Unfortunately since the BMS itself can fail, the pictures showing the physical changes to the cells/pack expose another type of safety design needed.

It is important that there is no "sharp" objects like bolts near the pack in case the pack expands due to a catastrophic failure as it could puncture the cells.

It is also important to notice any cables that could short when the pack expands (either part of the pack itself or like a nearby Controller, Converter, etc).

Perhaps a simple limit switch activated by either movement or expansion of the pack could be wired as a "kill switch" as a final safety.

For low voltage cutoff I think a latching relay (dual coil) would work best since it would not further drain the pack once activated and a simple manual switch could be wired to the second coil as a "reset" button.

While I like the clean installation You guys are doing, I think more time should be spent planning for the accidental action or premature failure of a component.
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