Solar controller not on bulk .

[merl]

I had a discussion recently with someone about Lithium BMSes and the fact that on some supplied (ready-built) batteries - and on DIY builds - they are far too open to incorrect configurations.
And then add in Youtube 'experts' and Forum 'experts' who tell you that you have to top-balance, bottom-balance, stick your left leg in and your right leg out and the chance of having a setup that is actually optimum starts getting remoter by the amp-hour. My advice would be to leave well alone!

I have a Victron BMV that monitors my Lithium Battery Bank and I have Lithium Batteries with various BMSes that report their voltage, current and state of charge. I have not made any changes to any of the BMSes on any of the batteries - one reason being they do not have that option and another being I feel no need to do so anyway - and the currents have always matched between the BMS and the BMSes added together and the Victron BMV SoC matching the average BMS SoC.

Absolutely agree, It seems to me that users on youtube are often needlessly obsessed with trying to extract every last milli amp hour from a battery and I just cant see to point. Ultimately there will be differences in the cells that make up a battery, to my eyes it's an unreasonable expectation to expect ALL of the cells to reach cut-off /full charge at exactly the same time. If you bottom balance then they'll fail to reach full charge simultaneously, likewise if you top balance em then they'll fail to all reach discharge together. Sure the 'balancing' resistors/FETs in the BMS will help but their resistance is very high and consequently the current that they draw is very low (just a few milliamps), so if you're discharging the pack over a period of several days then the balancing resistors could/should work but when you start drawing higher currents, you stand no chance. It's akin to having 4 baths filling and emptying at the same time and you trying to maintain the exact same level in all 4 with a teaspoon.

 

[mistericeman]

Absolutely agree, It seems to me that users on youtube are often needlessly obsessed with trying to extract every last milli amp hour from a battery and I just cant see to point. Ultimately there will be differences in the cells that make up a battery, to my eyes it's an unreasonable expectation to expect ALL of the cells to reach cut-off /full charge at exactly the same time. If you bottom balance then they'll fail to reach full charge simultaneously, likewise if you top balance em then they'll fail to all reach discharge together. Sure the 'balancing' resistors/FETs in the BMS will help but their resistance is very high and consequently the current that they draw is very low (just a few milliamps), so if you're discharging the pack over a period of several days then the balancing resistors could/should work but when you start drawing higher currents, you stand no chance. It's akin to having 4 baths filling and emptying at the same time and you trying to maintain the exact same level in all 4 with a teaspoon.

Wait till you join a Chinese diesel heater group on Facebook ....

It's like a lesson on how to frig about with working stuff TILL it shits itself and then complain about it not working .

 

[Nabsim]

Never really understood why they bother with Bluetooth on battery’s. If you only have on battery then I guess you could use the Bluetooth and not bother buying a Victron shunt. Have seen so many people posting problems or possible problems with the info from the battery’s.
Mine are just dumb battery’s with whatever dumb bms the manufacturer put in. No idea if they balance or what cell voltages are but they just work.
I just look at the Victron shunt for SoC

 

[wildebus]

Never really understood why they bother with Bluetooth on battery’s. If you only have on battery then I guess you could use the Bluetooth and not bother buying a Victron shunt. Have seen so many people posting problems or possible problems with the info from the battery’s.

It can be a nightmare for suppliers as well. I fitted a pair of batteries which had a BMS that was adjustable by the end user. I was constantly getting questions about should they upgrade the firmware, should they do this, should they do that, etc, etc.
Every time my reply was the same ... "Leave it, don't touch it. Just use it"

Mine are just dumb battery’s with whatever dumb bms the manufacturer put in. No idea if they balance or what cell voltages are but they just work.
I just look at the Victron shunt for SoC

 

[wildebus]

Wait till you join a Chinese diesel heater group on Facebook ....

It's like a lesson on how to frig about with working stuff TILL it shits itself and then complain about it not working .

Totally agree.
Buying either a battery with a configurable BMS or getting a Chinese Heater and then trawling the web .... It is not buying a battery - or heater, ir is buying a Hobby.
Which is fine if that is what someone wants, but if they bought it to use it, just leave the damn thing be!