sunshine_eggo
Happy Breffast!
I do not know what "the fees in a bms" are.
FETS (MOSFETS)
I do not know what "the fees in a bms" are.
Sorry, I didn’t notice the autocorrect… Fets. As in mosfet switches.I do not know what "the fees in a bms" are.
I thought the idea of a pre charge resister is to protect things from getting destroyed. If I want to prevent the fantom load from the inverter, I will have to disconnect it from the battery when I am not using it, or switch the inverter off. I can see that happen multiple times a day in a camper for example. Surely a manufacturer solution would be preferable and cheaper, regardless if it is in the BMS, the inverter or both.
Big difference between turning inverter off and connecting the inverter to the battery.
A precharge limiter is needed when connecting the battery to inverter.
Depends on the BMS design. Some are just shutting of for a brief period and then self reset after a few minutes.I am always worried what happens when the battery is disconnected unintentionally and/or automatically. For example, when there's undervoltage in the battery and the BMS shuts it down.
Question:
- is the battery then really disconnected - or is the inverter, physically, still connected?
- do the capacitors (I assume that's the most vulnerable part) of the inverter discharge of time, and when the BMS brings the battery online again blow up?
Depends on the BMS design. Some are just shutting of for a brief period and then self reset after a few minutes.
Capacitors bleed of over a period which could be days.
the BMS is not a switch - there are MOSFETs on the circuit board which are the shutting off the current. They ramp up very quickly when activated - but are slower then connecting a cable.
The cells will be "physically" connected to the inverter via BMS MOSFETs at all times, unless a physical switch is used to disconnect.So the battery and the inverter always stay connected. I assume this is a good thing here because it might prevent a huge surge of current, no?
The mosfet are odd in a way, the BMS can independently disable Charging or disable Discharging. Disabling both should effectively disconnect the inverter.
I'm also considering doing this instead.. I delved into the Midnite breakers in this post: https://diysolarforum.com/threads/class-t-fuse-or-dc-circuit-breaker.44249/post-575402I have dual AIMS 12,000w inverters and have not used pre-charge. When I got my first one (4 yrs ago), doing an Initial test connection produced a modest 'spark' but I wouldn't call it a major spark. For regular operation I wired in 250a Midnite breakers and just turn them on/off as needed for maintenance with no problems observed.
In short, yes that is possible, but very few BMS seem to implement it.I have no deeper understanding of MOSFETs. Wouldn`t it be possible to implement a "connect to inverter" mode in the BMS where it gradually ramps up and allows the MOSFETs to transfer more current? Or do MOSFETs have no chance to "defend" themselves against high currents?
The CSL500 Current Surge Limiter is a FET-based current limiting device [...] in conjunction with large (greater than 3.5kW) inverter/chargers.
The device is mounted permanently in series between the negative pole of the battery bank and the negative DC input terminal of the inverter/charger. The device protects the battery management system (BMS) from damage caused by the initial current spike that is created when connecting directly to the large capacitors (> 5 milliFarads) that are typically on the DC input side of the inverter/chargers. The device allows the batteries to slowly charge the capacitors (within 1 ms). This soft start avoids the high-current shutoff inherent to the BMS of the batteries.
Thanks for all your info.for the 3000 W inverter, i shall delay the power up until automated pre charge circuit declares bus has been pre charged.
Surely a manufacturer solution would be preferable and cheaper, regardless if it is in the BMS, the inverter or both.
were can you actaully buy these? where did this image come from? google lens gets it wrong
View attachment 116035
Anyone actually found one of these yet? cant find anywhere online