Navasolar Trolley Inverters

[Tech Guy SA]

okay got this feedback (finally)


Please ignore the battery level indicator as you need to understand how the Lithium batteries work. These units were AGM units, which we had changed to Lithium as per our specifications.

So, a Lithium battery will drop quickly from 27 down to about 26.9 V, as that is how they work. When you work with these batteries, you work in 0.1 V, not 1v as per AGM or Lead.

The graph will explain it more. This is from the manufacturer. As you can see, on 24V these batteries are done and need to be recharged.

 

[wingnut771]

okay got this feedback (finally)


Please ignore the battery level indicator as you need to understand how the Lithium batteries work. These units were AGM units, which we had changed to Lithium as per our specifications.

So, a Lithium battery will drop quickly from 27 down to about 26.9 V, as that is how they work. When you work with these batteries, you work in 0.1 V, not 1v as per AGM or Lead.

The graph will explain it more. This is from the manufacturer. As you can see, on 24V these batteries are done and need to be recharged.

View attachment 1925269

That doesnt explain the 4 to 1 bar after 6 minutes. 26.9V is 90% resting or 100% under load. The bars should stay full using AGM voltage curve until LFP battery is almost dead. As you can see, 10% LFP is at 50-60% AGM voltage.


@icantchooseone, how long has your test been running?

 

[icantchooseone]

That doesnt explain the 4 to 1 bar after 6 minutes. 26.9V is 90% resting or 100% under load. The bars should stay full using AGM voltage curve until LFP battery is almost dead. As you can see, 10% LFP is at 50-60% AGM voltage.
View attachment 1925276

@icantchooseone, how long has your test been running?

still have not tested . was waiting for feedback from supplier

 

[wingnut771]

okay got this feedback (finally)


Please ignore the battery level indicator as you need to understand how the Lithium batteries work. These units were AGM units, which we had changed to Lithium as per our specifications.

So, a Lithium battery will drop quickly from 27 down to about 26.9 V, as that is how they work. When you work with these batteries, you work in 0.1 V, not 1v as per AGM or Lead.

The graph will explain it more. This is from the manufacturer. As you can see, on 24V these batteries are done and need to be recharged.

View attachment 1925269

 

[icantchooseone]

im testing now

 

[icantchooseone]

battery is currently fluctuating between 25v and 25.1v and its been on for almost 30 minutes

load is at 400 watts ( i had plugged in my Ellies 1440 watt to increase the load so i guess the batteries in the Ellies got full ) so the load dropped from 450watts

 

[wingnut771]

battery is currently fluctuating between 25v and 25.1v and its been on for almost 30 minutes

load is at 400 watts ( i had plugged in my Ellies 1440 watt to increase the load so i guess the batteries in the Ellies got full ) so the load dropped from 450watts

Okay, ignore bars and focus on voltage. A load will cause voltage drop so a heavy load will cause more drop than a light load but then voltage should settle which it has. End test when it gets below 24V (completely dead lfp is 20V but this might make bms in the battery to cut out and go to sleep and would need to jump it with external voltage which we dont want so maybe dont go below 22V) but also take note of what voltage starts the low battery alarm.

 

[wingnut771]

battery is currently fluctuating between 25v and 25.1v and its been on for almost 30 minutes

load is at 400 watts ( i had plugged in my Ellies 1440 watt to increase the load so i guess the batteries in the Ellies got full ) so the load dropped from 450watts

Also be aware of lfp voltage curve, nothing happens in the middle and then the end it drops off quick:

 

[icantchooseone]

battery is currently on 25.0v and its been on for 46 minutes

 

[icantchooseone]

battery is currently fluctuating 24.9 to 25.0 and its been on for 1 hour

when it starts beeping im stopping the test i dont want to damage it

 

[wingnut771]

battery is currently on 25.0v and its been on for 46 minutes

 

[wingnut771]

battery is currently fluctuating 24.9 to 25.0 and its been on for 1 hour

when it starts beeping im stopping the test i dont want to damage it

I wouldn't put much trust in the battery low warning, remember its probably set for AGM voltage so keep an eye on it. You cant damage it, we just want to avoid the bms shutting down before the inverter shut down voltage (whatever that is). If the inverter shut down voltage is higher than BMS shutdown (unknown, anywhere between 20-22V) then there is nothing to worry about but I doubt it is. I would stop test at 23.5V, remember, those voltages in the chart above is resting voltage. You can always remove the load and see where the voltage bounces back up to to get an estimated soc.

 

[wingnut771]

battery is currently fluctuating 24.9 to 25.0 and its been on for 1 hour

when it starts beeping im stopping the test i dont want to damage it

Maybe when it starts beeping (if it beeps at all before 23.5V, if no beep at 23.5V then stop test), take a note of the voltage resting voltage, then start a new austerity test and see how long it can run just the wifi/laptop until it starts beeping again (or 23.5V). It should stop beeping (if it did beep) when the load is removed because the voltage should increase. Then we can see how long you can run like that so you know in future how long you have until you back in the stone age.

So far it sounds like its fine. Still fun to test these things though.

 

[icantchooseone]

Maybe when it starts beeping (if it beeps at all before 23.5V, if no beep at 23.5V then stop test), take a note of the voltage resting voltage, then start a new austerity test and see how long it can run just the wifi/laptop until it starts beeping again (or 23.5V). It should stop beeping (if it did beep) when the load is removed because the voltage should increase. Then we can see how long you can run like that so you know in future how long you have until you back in the stone age.

So far it sounds like its fine. Still fun to test these things though.

i think if i did that it would run into the AM , but i cant because i need lights on

just making notes : test was started at 4.33pm .

battery is currently 24.4 and its been on for 2 hours

 

[wingnut771]

i think if i did that it would run into the AM , but i cant because i need lights on

just making notes : test was started at 4.33pm .

battery is currently 24.4 and its been on for 2 hours

Fair enough, forget about austerity test, lets just see when beeping starts but stop at 23.5V if no beep. Anyway, so far things are happening the way they're supposed to.

 

[wingnut771]

i think if i did that it would run into the AM , but i cant because i need lights on

just making notes : test was started at 4.33pm .

battery is currently 24.4 and its been on for 2 hours

Take note of bounce back voltage after 400W is removed.

 

[icantchooseone]

it completely shut down at 24.7 volts . beep was so soft i never heard it

its now on 25volts after maybe 8 minutes

can i charge it now ?

 

[icantchooseone]

charging . i assume you dont need to know when its fully charged ?

it completely shut down at 24.7 volts

is that bad ?

 

[wingnut771]

it completely shut down at 24.7 volts . beep was so soft i never heard it

its now on 25volts after maybe 8 minutes

can i charge it now ?

Wasn't it on 24.4V, how can it shut down at a higher voltage?

Anyway, insignificant details. Test passed.

Yes, you can charge it now.

 

[wingnut771]

charging . i assume you dont need to know when its fully charged ?



is that bad ?

No, it will stop charging when its full.

Bad in you not getting full capacity or bad you damaging the battery?

I'm still confused by conflicting 24.4 and 24.7 numbers.

I suspect it shut down at 24V, bounced back to 24.7V and then slowly rose to 25V (resting voltage takes a while to get a proper reading).

So, no, its not bad for either reasons.