Battery Building Questions.

Yep the Dayly 100a BMS from battery hook up. 12v.  all my other batts got the same kind and they all work fine. but even when I tried a brand new one never used on this battery its giveing the same results.  I check the wire coming from the negative to the bms and it shows the correct voltage.

hmmm, wondering if the solder could be bad on the negative, but that would effect the voltage at the connection point on the bms if that was the case and its not. so can't be that.  Just weird. 

Just had one of my Le Ion go up in flames.  Luckly I was awake in smell sometrhing burning, wnet into the power room and there was heat coming from one of the batts I made, grab the wire cutters , and snipped the wires off the bus bar and ran outside and place in the middle of the drive way.

luckly it was one pack in a pack of 16 that went up, snipped it out and left it while keeping the ammo box on the porch checking each of the other 15 packs makeing sure there wasn't any heat or melted eletrical tape lol.

These were 4.4 3.7 le ion flat cells that was used in scanners, and I paird 7 of them to make a 24v.   16 of them made 70ah.  These had built in bms, but, for some reason one of them decide to say the heck with it, my other batts bms didn't even shut down I got some floating at 15.73vdc and they are set to cut off at 14.40  Looks like I'm going to have to find a cut off switch to have from the charger to the batts. any suggestion?  I got one of those 100a victron, but from what I heard those things are junk.

Yikes.  Glad you caught it before it got out of hand.

Did you test the cells before building the pack - ie, full cycle capacity test, temperature rise during charging, resting voltage after charging, impedance test etc?  Personally I'd never reuse any of the lithium chemistries that are prone to thermal run away unless I knew their full use history.  Even experienced people can get caught out with cells randomly turning into glow plugs.

Nope, I check to make sure they were working as far as voltage, as these supposed to have built in bms per 3.7 cell.  and they was new never used flat cells for scanners, battery hook up still sell them.

What happen was they were the first on the bus bar after the charger, so they get all the power before my main bank of regular Lipa4, and they reached 29.2, if I had a regulator I could have prevented it from reaching that high of a battery power. I only want my system to go up to 28V nor more better at 27.8v.  since I got a skyblue that is not wifi running my charging I can't program it so its pushing I'm guessing to 29.4 before it floats.   I'm probley going to switch it out to the other blue since I know it works now, and I have it set to not go pass 28.8 I've been letting my bank recover from a full discharge which I wasn't trying to do, and well I see what happens now, and odd, two of my 12v built batts the BMS were hot, and when I log into them to see what was going on they was over 15v range, however, as soon as I got rid of the le ion out of the system and ran a shop vac to suck the power down the master GS stop beeping and I went back into the bms and it was at normal 13.89V makes me not trust those daily bms and one of them was the overkill bms which is a modified daily bms it was hot as well.  That is why I'm looking for something that I can clamp down on the chargers when they hit that level and don't back off.

Also I'm really, really considering on moveing the batts outside in a shed, keep the inverter where it is but move the batts on the outside in some kind of shed against the house where the power room is.  soon as I find a job where I can afford to buy a shed.

The Victron Battery Protect works well, but you have to keep within it's own specs.  The BP is not intended to switch very high loads.  People were hooking up inverters and the inrush current from the capacitors in the inverter charging up grossly exceeds the ratings of the transistors in the BP, and pretty much all FET (transistor) based protectors for that matter, and kills them.  The FETs either go open, so no power, or short, so impossible to turn power off.  Victron even advises that loads like inverters should not be connected to the BP, but it doesn't stop people doing it, and then blaming the BP when they kill it.

Ideally the battery's own BMS should protect the cells rather than relying on something external turning the current off.  Some solar chargers, such as Victron's blue / smart series, can be remotely turned off by pulling a pin on the VE.direct interface ... to +12v or 0v, can't remember which, but also with hex commands set via the serial lines on the VE.direct port.  The problem with non-lifepo4/lto cells is that once thermal run away starts disconnecting the load makes no difference.  It's all self sustaining.  All it takes is one defective cell in a pack that draws current from its neighbouring cells, not necessarily enough to blow it's own fuse to the pack bus wire.  The heat from that cell raises the  temperature of its neighbours to the point where they run away, and all hell breaks loose.

Watch this ...  it started when just one cell failed.

FYI, it's not just things like the BP that get destroyed with extreme current from inverter capacitors etc.  BMSes that use FETs to switch the battery output can also be damaged.  Even contactors degrade if subjected to another high current cycles.  Precharging is mandatory IMO.

well, then I can use the bp to cut off if the voltage gets higher then I like, will do that. I've siwtching everything to those mega vuse, but thats not going to stop the over chargeing.  nah, I don't put the bp in line to the inverter, its a BP not a power giver lol. cause 100a it would trip just turning on the gs inverter lol.

You really should adjust the voltage your chargers are set at rather than using the BP to disconnect them even if it means calling in a friend / relative / etc.  Using the BP to terminate  charging is like using a hammer to put a screw in.  It'll work but it's not really the right tool for the job.

*laughs* last time I had somebody try to program a solar charger, they justr didn't understand what to do. lol.

On 6/27/2021 at 10:41 PM, TheButcher said:

The Victron Battery Protect works well, but you have to keep within it's own specs.  The BP is not intended to switch very high loads.  People were hooking up inverters and the inrush current from the capacitors in the inverter charging up grossly exceeds the ratings of the transistors in the BP, and pretty much all FET (transistor) based protectors for that matter, and kills them.  The FETs either go open, so no power, or short, so impossible to turn power off.  Victron even advises that loads like inverters should not be connected to the BP, but it doesn't stop people doing it, and then blaming the BP when they kill it.

Ideally the battery's own BMS should protect the cells rather than relying on something external turning the current off.  Some solar chargers, such as Victron's blue / smart series, can be remotely turned off by pulling a pin on the VE.direct interface ... to +12v or 0v, can't remember which, but also with hex commands set via the serial lines on the VE.direct port.  The problem with non-lifepo4/lto cells is that once thermal run away starts disconnecting the load makes no difference.  It's all self sustaining.  All it takes is one defective cell in a pack that draws current from its neighbouring cells, not necessarily enough to blow it's own fuse to the pack bus wire.  The heat from that cell raises the  temperature of its neighbours to the point where they run away, and all hell breaks loose.

Watch this ...  it started when just one cell failed.

 

FYI, it's not just things like the BP that get destroyed with extreme current from inverter capacitors etc.  BMSes that use FETs to switch the battery output can also be damaged.  Even contactors degrade if subjected to another high current cycles.  Precharging is mandatory IMO.

 

LG had a major problem with the cells they sold GM for the Bolts. Owners were warned not to park their cars in a garage as they could end up with a battery fire. jehugarcia did a test on the cells like I'm working with and in his shorted battery test it was 352 Amps for 30 seconds before the battery popped. Thermal camera showing only the temp of boiling water when it did it. But no fire. That is a 50C test which no one should ever do on any of the Lithium batteries unless they take proper safety precautions as something IS going to give. Mine will have a 150Amp breaker on one leg and a 100 Amp fuse on the other and in theory, I could safely pull 800 amps as I have 4 cells in parallel in each battery. If the 6K GS inverter ever hit that high a load, Sid would have some troubleshooting to do on a fried unit.

55 minutes ago, Waterman said:

If the 6K GS inverter ever hit that high a load, Sid would have some troubleshooting to do on a fried unit.

Haha, likely.  Continuous datasheet spec is 1,080A/quadrant on the FETs, with an absolute max surge of 3,240A rated.  However, due to (PJ) mainboard layout, I don't think the FETs would be able to reach that level without damaging themselves...especially at 48vDC (due to signal crosstalk).

Though it is worth noting that a GS 6k inverter in 12v configuration WILL run 600A continuous current at full load.  We can't recommend/guarantee 12v operation on a GS inverter (due to the high amperage!)--but hey, I've heard that we have one customer running a 12v GS inverter, and he's had it up to 5kw without issues (>500A).

I bet I could get Puff to visit if I had all the cells hooked up without a breaker on them. The total surge from them on just the SPIM08H cells could reach 12,000 Amps and a continuous rating of 6,400 Amps.

Lithium cells are a bit bonkers really.  Quality 18650s can have sustained discharge rates of 30A and short circuit capabilities round 200A.

Okay, after getting back into the swing of things, with my lf04 batts, I've ran into a issue that must have happen when my whole system decided to over amp it self.  I have one diy batt that has a bms that will not turn off, or on and even if you unplug the balance wires from it, it still allows power through, so I'm guessing the eletrical is shot, probley the relay is welded close.  and it showing that the battery is nearly dead, the info will not update on the bluetooth.

Then I got another diy batt that will not accept charge, and shows a different power output then what the battery is saying also the first battery is doing that same it showing on the screen its got 13.12v but testing the batt shows a 12.9.

So looks like I'm going to have to buy two new bms to replace these.

I got fuses now to protect each batt from over surge, but I reather go with breaker, and the one on amazon that are rated 120a seems to be a knock off even the busman seems to have bad reveiws.  Any suggestion on a resetble breaker that don't cost a arm and leg, cause I'll need to get roughly 8 of them.  I'm really considering on doing a hybrid setup, I'm seeing a new thing or some what old school of useing lythuim to keep a set of agm batts topped off useing a higher voltage to a solar charger to charge the lower voltage.