Holding the cells together in trays

[1xAA]

What are you guys using to hold packs together? Hot glue, nuts-bolts, shrinkwrap, all of the above?When I lift the cell(s) the trays are flexing.

 

[Redpacket]

Your pack looks like it is 12 x 25 = 300p?
This is quite large & as you found, also quite heavy.
Seems more common sizes are 80 - 120p.
You'll probably get more rigidity once the bus bars (eg spot welded strips for neg?) are installed.
People seem to use cable ties threaded between the cells around the busbars.
Nuts & bolts might add shorting risk.
Hot glue might make changing a bad cell harder.
Shrink wrap ditto, + can't measure individual cells well but also not that strong?

 

[OffGridInTheCity]

Me -I use 4 x 5 holders,hot-gluethe busbars to the holders,add twist ties around the pack as needed to get it 'solid', and then soldering/wires (or nickle/spot-weld)add somerigidity. Between all 4 of these - they are quite hardy to pick up/carry/manipulate into place.

Here's an 88p on left and 44p-60p on the right:

 

[1xAA]

Thanks. Zipties it is. I really want to keep a close eye on these cells when I finish this pack in a couple weeks.

12v - 288p (one row empty for front panel). I know 24 is better but I have several 12V inverters and not enough cells for a good 24v pack.

 

[Korishan]

If you are going with 12V, it would be best to use LiFePO4 cells. LiIon cells are very difficult to fit with 12V arrangement. It's either too low on full charge (3s) or you can't quite high enough to get a good charge (4s).

Depending on how many amps you would be pulling, and you need to stay with the 12V based inverter, then it would better to go 5s or higher and then use a buck converter.

Otherwise, it would be recommended to wait until you do have enough cells to go 24V.

 

[1xAA]

Thanks for the input. Currently the pack I am making is planned for a low-load (60watts) environment with a 12v inverter that alarms at 10.6v.

I do have a 24v APC, but I am thinking the 388 cells are not enough to make a decent 7s and I am not sure if the inverter will tolerate 7s voltage. I could make a test pack and see, but afraid I will mess up the 24v ACP testing on 7s @ 29.4v when it is only designed to tolerate 26.5ish. Do these APCs usually protection from hardware failure in overvoltage situations? Seems I hooked this APC up and ran the voltage to 6s and the display went blank and when I power it on my power supply powers off due to the surge.....I don't think it liked 7s. I will confirm this in a few days when parts arrive.

I have 400+ LiIon so I just need to get some money out of them as I move away from pb into Lithium. I simply am not patient enough to wait until I acquire more cells. Maybe later I could build another 3s388p and series the two together for the 24v APC. No soldering on the pack yet so I am not totally committed to 12v.

Another problem is I am nearly out of panel space with my current charger controller, it only has room for 100 watts of expansion. I could spend until I am broke, so moving as much as I can financially tolerate atm with this project.

I hope to be moving soon, so I hope this will allow me to expand....

 

[Korishan]

The APC should handle all the way up to 28VDC. A fully charged lead acid battery is usually 14V (after the charger is disconnected, the battery will drop down to about 13.5V after resting).

Which APC UPS unit do you have?

I would not drop to a 6s, as that'd put a possible over voltage condition on the cells.

It would be a waste of time to build a 4s for now, then later build a 3s because you would have to disassemble the 4s and reprocess the cells to compare them to the additional cells as each Parallel section needs to be as close to the same as the others. If you just add some more in series later on, you will not have this balance in capacity.

With 400 cells, you can have 7s57p. Then to add more in parallel, just make sure each additional section has the same amount of capacity added, regardless of the count in parallel.

 

[OffGridInTheCity]

I do have a 24v APC, but I am thinking the 388 cells are not enough to make a decent 7s and I am not sure if the inverter will tolerate 7s voltage.

If you literally mean "APC" as in www.apc.com - then yes, 7s will work with it. The APC UPS line (1500, 3000, etc) willcharge up to 25.6v (3.95v/cell) +/- a bit - well within safe range of 18650. Here's an example of my Chargery 8T BMS readings on a 7s7p 18650 lithium-ion pack in an APC 1500:




I have several APC 1500(s) and 3000(s) running 7s replacements for the original lead acid and they are all right around 3.95v/cell.

The downside is that 3.95v/cell is the max the cells will charge so you loose some capacity at the top end (3.95v -> 4.15v/cell), but the pro is that 3.95v max will lead to long life and its not horrible (like 3s or 4s for 12v) as far as power ranges.
Another con is that the bottom / cut-off voltage for the APC unit itself is around 21.5v (3.07v/cell) which is safe BUT its better to only go down to 3.4v-3.5v/cell on a regular/daily basisbecause of the discharge curve... there isn't much power between 3.4v and 3.0.v and is reduces the life of the cell and balance is more difficult. So if you can figure a way to cut-out at 3.4v-3.5v with a battery guard or some other means - itslonger life if you stay within 3.4v -> 3.95v.

7s will work as a direct battery replacement for "APC" UPSs.

 

[jdeadman]

I drill holes in the black area's of the Holders and over the Bus bars. (Bus bars are 3 strands of 14awg copper) then that holds the pack together

 

[1xAA]

APC is the 1300 PRO. Anyone know charging current, no load drain and if the fan is thermally controlled on this APC?

Still have a couple weeks before I commit.

 

[Korishan]

I would recommend getting the PowerChute software (https://www.apc.com/shop/us/en/products//P-SFPCPE31). That'll tell you a lot about the unit and can possibly configure stuff as well. Might even be able to set the charge voltages and limits. This is the Personal version of PowerChute. There is a Professional, or Server, or Enterprise (not sure what they call it) that gives you a lot more functionality. Not sure if it's free or not, though. I do know that older versions of it are usually free, or you can get a copy of it.


And here's the stats on that unit: https://www.apc.com/shop/us/en/products/APC-Power-Saving-Back-UPS-Pro-1300/P-BR1300G

 

[OffGridInTheCity]

APC is the 1300 PRO. Anyone know charging current, no load drain and if the fan is thermally controlled on this APC?

Still have a couple weeks before I commit.

I would bet that all APCs are similar as they all are built to use the same24v lead-acid battery technology. Charging is around 3a'ish (24v@3a = 72w)on APC 1500s.
If you buy one, a 7s lithium-ion will for sure work and you can measure the top voltage and charging amps directly at the unitonce you get it for exact numbers.

Native APC chargingispretty low compared to what the 18650s can handle but APCsare not made for fast charging but rather to keep the battery topped off for power outages.

You can hook Solar ->charge controller -> batteryto facilitate solar charging at the same time itshooked up/running in the APC. A moderately sophisticated charge controller (such as EPEVER with control box -https://www.amazon.com/dp/B07M6PD3DP/ref=sspa_dk_detail_1?pd_rd_i=B07K9HBYPY&pd_rd_w=BARKL&pf_rd_p=7d37a48b-2b1a-4373-8c1a-bdcc5da66be9&pd_rd_wg=3QAO6&pf_rd_r=Y02A32RDKZXTPWESJW36&pd_rd_r=37213d8b-9bd4-4c72-b5e6-5eb8c1e967a3&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUExWU9DS1RHUkxMWDI2JmVuY3J5cHRlZElkPUEwNjM5MjA2MlQ0TENaNFM1TFlIVyZlbmNyeXB0ZWRBZElkPUEwODc5ODkxMTlWQVRPNFBZREJITCZ3aWRnZXROYW1lPXNwX2RldGFpbCZhY3Rpb249Y2xpY2tSZWRpcmVjdCZkb05vdExvZ0NsaWNrPXRydWU&th=1)will let you set the top charge (bulk/float) so you keep it down to the APC's operating range.You'll need to top out at the APC expectations or itwill show red-light/beeps if the battery get's higher than expected.

You could even hook a direct 120v -> 24v lithium ion charger to it as well, maybe a 6s charger with25.2v top charging (http://www.batterysupports.com/22v-...attery-charger-6s-6x-36v-lion-lipo-p-476.html) on the 7s for fast charging in the lower range, orsomething where you can keep it from charging too high and causing the APC to beep/show-error.

TMI - I've purchased all my APCs as used on ebay... and all have worked perfectly. For example, here's an APC 1500 for only $150 and free shipping -https://www.ebay.com/itm/APC-Smart-UPS-1500-SUA1500-UPS-No-Battery-90-Days-Warranty-Fast-Ship/274449536180?hash=item3fe67794b4:g:uW0AAOSwEl5fKccu (I have 11 of them and some are over 15yrs old and still in service - I must be in love)

I don't mean to come across as pushing either product or solution above - but rather trying to share some ideas about what's possible with thehopethey will help you figure out what you want to do for your situation

 

[Korishan]

You can hook Solar ->charge controller -> batteryto facilitate solar charging at the same time itshooked up/running in the APC. A moderately sophisticated charge controller (such as EPEVER with control box -https://www.amazon.com/dp/B07M6PD3DP/ref=sspa_dk_detail_1?pd_rd_i=B07K9HBYPY&pd_rd_w=BARKL&pf_rd_p=7d37a48b-2b1a-4373-8c1a-bdcc5da66be9&pd_rd_wg=3QAO6&pf_rd_r=Y02A32RDKZXTPWESJW36&pd_rd_r=37213d8b-9bd4-4c72-b5e6-5eb8c1e967a3&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUExWU9DS1RHUkxMWDI2JmVuY3J5cHRlZElkPUEwNjM5MjA2MlQ0TENaNFM1TFlIVyZlbmNyeXB0ZWRBZElkPUEwODc5ODkxMTlWQVRPNFBZREJITCZ3aWRnZXROYW1lPXNwX2RldGFpbCZhY3Rpb249Y2xpY2tSZWRpcmVjdCZkb05vdExvZ0NsaWNrPXRydWU&th=1)will let you set the top charge (bulk/float) so you keep it down to the APC's operating range.You'll need to top out at the APC expectations or itwill show red-light/beeps if the battery get's higher than expected.

You could even hook a direct 120v -> 24v lithium ion charger to it as well, maybe a 6s charger with25.2v top charging (http://www.batterysupports.com/22v-...attery-charger-6s-6x-36v-lion-lipo-p-476.html) on the 7s for fast charging in the lower range, orsomething where you can keep it from charging too high and causing the APC to beep/show-error.

Agreed. You could use a secondary charger specifically designed at charging lithium. Then in the PowerChute turn off charging (if you can), or at least lower it's charge voltage (again, if you can). If you can't change any of the settings, just make sure that the solar charger will take control of the charging by charging faster.

 

[1xAA]

I have the comms cable with personal edition for the APC and nothing can be changed other than when it shuts down or when to switch from the grid to backup power unfortunately; sure wish they had something to give us more control. The only useful info from Powerchute PE is battery state and time until power off. 3a charge would be decent compared to the EPS 550 (12v) which is .3a.

I was thinking (future parameters thread) about programming my charge controller to charge my 18650 pack and putting the two cheapo PWMs on the pb bank, but, but, but, voltage, current, holes in house, wires and on and on and on. I might switch the 18650 pack to 7s and just get a buck converter for 12v as mentioned if I want to use the 24v pack on another inverter later. Still waiting to do the self-drain on these cells.

My system has to grow is all I know at this point for sure.

 

[Korishan]

I have the comms cable with personal edition for the APC and nothing can be changed other than when it shuts down or when to switch from the grid to backup power unfortunately; sure wish they had something to give us more control. The only useful info from Powerchute PE is battery state and time until power off. 3a charge would be decent compared to the EPS 550 (12v) which is .3a.

Sounds like you need the Server, Network, Pro, what ever it's called version then

---

https://www.apc.com/shop/us/en/cate...nagement/powerchute-business-edition/N-o29ysx
here's the Business Edition. There's also a Network edition as well

 

[1xAA]

Zipties fixed this pack up well. Good and solid now. Thanks for the suggestions.

 

[ng.sa]

G'Day OffGridInTheCity

Here's an 88p on left and 44p-60p on the right:

These packs do not seem to have BMSs, do you use them with your packs ?

TIA

 

[OffGridInTheCity]

G'Day OffGridInTheCity

Here's an 88p on left and 44p-60p on the right:

These packs do not seem to have BMSs, do you use them with your packs ?

TIA

Good eye! Thepacks will be managed by Batrium WM4 but weren't quite done at the time of the pic-I add the longmons as a last step.