24v BMS for 12v battery

[Borneoboy]

Can i use just the first 4 wires from my 24v Daly bms to control overvoltage on my new 12v battery?
It only looks at single cell voltage doesn't it? And will stop the charging if any one cell goes above 3.65v (max).
Only using 100A/hr battery and 500 watt inverter

 

[Borneoboy]

When I look back at my first posts to this Forum 2 years ago, I realise how little I knew about the whole thing.... I didn't even know the difference between MPPT & PWM !
Now, as you can see from the above post, I am trying improvements and experimentation... Apart from "off-grid garage" (his stuff is interesting but also a bit pricey for the average guy) , I feel there's not enough on the net about this, it's mainly reviews and recomendations and of course making money from these...
This Forum and Will's backing have been a great help, even if sometimes the replies do dry up!

 

[Rednecktek]

Can i use just the first 4 wires from my 24v Daly bms to control overvoltage on my new 12v battery?
It only looks at single cell voltage doesn't it? And will stop the charging if any one cell goes above 3.65v (max).
Only using 100A/hr battery and 500 watt inverter

As I understand BMS's, and from what I've learned on here, you have to have the right BMS for the job unless you have one of the wierd multi-cell versions. If you were to only hook up 4 wires and let the other 4 hang I think the BMS would assume the SOC on 4 of them is 100% and the SOC on the other 4 is 0% and crash itself.

Now, there ARE some that are multi-cell and you have to short certain cell wires in a specific order to get them to play with what you have, but I don't think Daly makes any of those.

 

[Borneoboy]

As I understand BMS's, and from what I've learned on here, you have to have the right BMS for the job unless you have one of the wierd multi-cell versions. If you were to only hook up 4 wires and let the other 4 hang I think the BMS would assume the SOC on 4 of them is 100% and the SOC on the other 4 is 0% and crash itself.

Now, there ARE some that are multi-cell and you have to short certain cell wires in a specific order to get them to play with what you have, but I don't think Daly makes any of those.

Thanks for your input... You're probably right and the BMS wouldn't like a 0 volt return from 4 of its wires... IF it is monitoring total voltage.
It is a very basic BMS (e-bike type) and seems to only react to over and low voltage... there's no monitoring function to see what it's doing, (I use my multimeter) but definitely stops the charging if any ONE cell gets to around 3.4 volts or 2.5 volts. I rarely get more than 27.2 for "fully charged".
I think I'll play safe and use the correct BMS.

 

[Borneoboy]

Thanks for your input... You're probably right and the BMS wouldn't like a 0 volt return from 4 of its wires... IF it is monitoring total voltage.
It is a very basic BMS (e-bike type) and seems to only react to over and low voltage... there's no monitoring function to see what it's doing, (I use my multimeter) but definitely stops the charging if any ONE cell gets to around 3.4 volts or 2.5 volts. I rarely get more than 27.2 for "fully charged".
I think I'll play safe and use the correct BMS.

I'll soon be building a much larger battery (when I've finally got all the ingredients together from China!) - 2P8S.
Watch this space for more possible problems !!