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I really need your help in order to figure out a solution to detect a blow fuse in a 16S parallel connection.
The issue is: Despite a fuse has been blown, the voltage at the other side of the fuse is going to be the same just because it comes from the rest of the parallel batteries.
I would really appreciate your help to figure out a solution to send a signal when a fuse has been blow.
This is my battery project and the PCB:
The circuit diagram:
Something like this should work.
Comparators are usually slightly biased (biasing not shown - could perhaps just be drop across wiring with proper design) such that when fuses are not blown comparator outputs are high and LED not lit.
If say battery B12 blows fuse 4 then B12 voltage rises under sudden no load.
Comparator 2 in- rises above its in+ and comparator output goes LOW and lights LED D2.
simulate this circuit – Schematic created using CircuitLab
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WINDOW COMPARATOR MONITORING OF BLOWN BALANCING FUSE.
Here is a conceptual window comparator system that lights an LED if a balance fuse is high or low.
I'm not convinced that this is useful - but, it may be.
I expect that being able to monitor whole string current contribution would tell you if a string was bad - but with a lot less work.
However:
CP is the common point for all 3 cells B4 B5 B6.
Say F3 blows.
CP is now the common +ve voltage of BAT4 and BAT5 but NOT BAT6.
CMP1_+ is slightly above CP due to R3/R1. If BAT6 +ve is still AT CP or below it then CMP1 output will be high.
If BAT6 output rises slightly above CP then CMP1 output will go low signalling a fault.
Similarly
CMP2_- (opposite of for CMP1) is slightly above CP due to R3/R1. If BAT6 +ve is still AT CP or ABOVE it then CMP1 output will be high.
If BAT6 output falls slightly below CP then CMP2 output will go low signalling a fault.
So, CMP1 + CMP2 form a window comparator so that if BAT6 with blown F3 remains very close to CP then no alarm is given. BUT if BAT6 Vout deviates more than very slightly from Cp an alarm will be given.
You need two comparators and 4 resistors per battery.
Comparators can be very low cost.
I've assumed an open collector output (eg ye olde LM339, LM393 etc).
BUT - is this really meeting your need? It MAY be.
If
All the answers assumed an external fuse with easy access to both sides. However, the lithium battery pack you are using is probably made of three or four lithium batteries in parallel. The final output voltage is created by repeating so many of these groups of 3 or 4 parallel batteries, each connected in series. The fuse is inside each lithium batteries, at the very tip of the positive side. That fuse will blow when current is too high or voltage drop too low. The battery then become permanently disconnected and we will call it _"dead".
How to detect one dead batteries?
Method #1: charging and discharging time is proportional to the number of batteries in parallel. When you connect the charger to the pack, the voltage will rise faster on the group that has one or more dead batteries. Starting from fully charged state, the voltage across the group with dead batteries will fall faster. Method #2: Insert a small resistance in series with every single lithium batteries on the negative side. The smaller the resistance, the lower the loss but the more difficult it is to distinguish from noise. Method #3: The best but most expensive method is too use connectors such that you can disconnect any single batteries to test voltage and load current as needed.
