Cell monitor

Z

zoneblue

New member
Joined
Mar 7, 2019
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Hi all. Quick question. Without going a full bms route can anyone recommend a cell monitor product that:

-7S
-draws its power from the full pack
-low idle current
-audible warning on cells above or below threshold
-robust

Ta.

BTW Heres a pic of the build. 7S36P NCR18650PF


image_fcumth.jpg
 
You could use a LiPo alarm. They are often used in RC devices.

However for a pack of that size, I would defiantly use a proper BMS. Even if it was a cheap Chinese smart BMS. You really don't want to over charge a pack of that size. Even one 18650 can make quite a bang.
 
Geek said:
However for a pack of that size, I would defiantly use a proper BMS. Even if it was a cheap Chinese smart BMS. You really don't want to over charge a pack of that size. Even one 18650 can make quite a bang.
Click to expand...

Agreed. Im just waiting for Electrodacus's next batch of integrated solar charger/BMS to ship in April/May.

My concern about cheap chineses BMS is they are often more of a liabilty than a help. Perhaps thats changed since last i looked.
 
zoneblue said:
Geek said:
However for a pack of that size, I would defiantly use a proper BMS. Even if it was a cheap Chinese smart BMS. You really don't want to over charge a pack of that size. Even one 18650 can make quite a bang.
Click to expand...

Agreed. Im just waiting for Electrodacus's next batch of integrated solar charger/BMS to ship in April/May.

My concern about cheap chineses BMS is they are often more of a liabilty than a help. Perhaps thats changed since last i looked.
Click to expand...

Daromer did a review of a 14s modal. Link
 
+1 on the Lipo Alarm. I use it on my lawnmower battery instead of a BMS and it works great! Very low current draw. Only thing is the lipo alarm only works for discharge, so you would still need another product to monitor charging voltages, unless you use an RC charger with balance loads.

Btw, nice pack! Did you spot weld first and then solder the fuses on the bent nickel strips? Or did you leave nickel strips on from cell recovery? I'm talking about the positive side. Just curious as that's pretty ingenious and I wish I thought of that.
 
Cherry: Use 2. THey dont check total voltage on the larm function anyways.
 
daromer said:
Cherry: Use 2. THey dont check total voltage on the larm function anyways.
Click to expand...

Pulling your leg: Impossible ! :D :D
 
"Pulling leg" ??
 
daromer said:
"Pulling leg" ??
Click to expand...

10 s was the second time i asked, the other one was the BMS, remember ? ( i bought that btw).
So, i asked the same, with a twinkle in the eyes, and you didnt fall prey.


Invincible, really. I raise my hat.
 
Sorry, dont follow at all.
 
Dallski said:
Did you spot weld first and then solder the fuses on the bent nickel strips? Or did you leave nickel strips on from cell recovery? I'm talking about the positive side. Just curious as that's pretty ingenious and I wish I thought of that.
Click to expand...

Im not really sure i could recommend the way i did it, it was kinda labor intensive:

1. bend nickel strip using a form
2. holding the bus copper and nickel strip over the cell spacers, line everything up, and temporarily tie the strip to the bus using copper strand.
3. solder nickel to bus (for positives), then remove tie wire (where it isnt soldered in too much).
4. weld positives, alignment was really really good. so far so good.
5. cable tie both grids together (not too tight)

6. cut nickel strip for the negatives in 15mm lengths, punch a small hole in one end to house the fuse wire. Bend to 90 degrees
7. weld negatives
8. bend negative strips back on themselves, using a small wood slither (maybe 2mm x 8mm x 20mm),
9. cut fuse wire to length, and make a small hook on one end. Insert hook into nickel tab, make another hook on the other end, and using the springiness of the fuse wire allow both hooks to hold the fuse wire in place. Then solder the two ends, which goes super easy and fast.
10. lastly solder the fuse wire to the bus. I used a combination of locking tweezers to dissipate heat, and small wooden wedges to lift the bus of the cell spacers. Worked ok once i got the hang of it.

At step 2 dont try to solder one at a time, the alignment becomes almost impossible. Also soldering one, melts the adjoining one, so the tie wire helps with this and or locking tweezers to shed heat. At step 5 i realised some cell spacer intersections dont cable tie too nicely. Bodge required here and there. At step 8 i realized the protruding fuse wire might take an alternative path to the cell and i so added the red insulator offcuts to prevent this. God i was glad when it was finished. Gotta be an easier way.

Thanks for the ideas guys.
 
Wow, that's a lot more complicated than I thought it would be. I was thinking that you could use the nickel strips that are already on the batteries you reclaim and fold them for soldering. Would eliminate gassing (holes caused by removing particularly stubborn nickel strips, like from e-bike packs), as well as keeping the heat away from the cell during soldering, while also saving the time it takes to remove nickel strips.
 
chargery bms16 (cost 100) monitors all those parameters and also triggers relays to stop charging. All the parameters are programmable.



If you just want over/under alarms the Tenergy Intelligent Cell Meter Alarm Digital Battery (cost 11 dollars) you need 2 of them because they are 6s. I use these and they work good.

Tenergy Compact Cell Meter
can display total voltage. For 1S-6S LiPo/LiFePO4/Li-ion battery pack, it can display: total
battery voltage, individual cell voltage and the difference between the highest and the
lowest individual cell voltage.
Battery Alarm For lithium-based batteries, Tenergy Compact Cell Meter can be used as an
over-charging / over-discharging alarm. It emits a loud beeping sound and its LED flashes
brightly when the batterys voltage rises above 4.22V, or drops below an adjustable
threshold between 3.0V and 4.0V.
Flight Time Tracker With Tenergy Compact Cell Meters lightweight and compact design, you
can mount the unit on your RC helicopter/plane, and during its flight the alarm can inform
you when the battery is in need of charging.
Easy To Use Tenergy Compact Cell Meter can read the status of your battery automatically as
soon as they are connected. Its simple control makes it suitable for users at all levels.
LCD screen Easy-to-read LCD screen lets you view your batterys status at a glance.


image_nafmwu.jpg


another one I used is the isdt bc-8s (cost 20 dollars), but this one has a lighted led screen it uses more power then the tenergy

"The BC-8S is also equipped with a number of alarms that activate a beeper as well as flashing
red lights when triggered. A high voltage alarm, a low voltage alarm, a voltage difference
alarm (voltage difference between cells) and finally a location beeper alarm for finding lost
aircraft. All of the aforementioned alarms have user definable parameters."


image_ptojyc.jpg
 
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