unicmarket:




Finally, every battery as a discharge rate that should come with it; such as 200A at 10hr or 20hr, meaning this battery is safe in discharging max 20A in the space of 1 hr for the 10h rating, so certainly the guidelines of battery discharge rate should be followed as specified for that battery.

For technical and educational purposes, it’s accurate and valid. The calculator is to ease calculation and not too exclude professional advice
Thanks bro

terrymason:
Have seen in various videos and setup where breakers/Fuse are put between panels and charger controller (Which is highly compulsory), but breakers in between batteries and charger controller are scary to me. Let say theirs a surge and the breaker between your battery and Cc tripped off and the one between the panel and CC is still on, what do you think will be the outcome of the CC in use.. ?

What's your input DIY Guru's, newbie and the house....

ojeysky:


Just curious, have you tried to charge at 3.45 per cell instead of over 3.5v per cell? And did you notice more than 5-10% difference in capacity? Because I don't think charging LFP at high voltage is a good thing for the battery's health

terrymason:
Have seen in various videos and setup where breakers/Fuse are put between panels and charger controller (Which is highly compulsory), but breakers in between batteries and charger controller are scary to me. Let say theirs a surge and the breaker between your battery and Cc tripped off and the one between the panel and CC is still on, what do you think will be the outcome of the CC in use.. ?

What's your input DIY Guru's, newbie and the house....

tchijioke:


Use a dual pole circuit breaker...connect it such that the pv+ve cable goes through one pole to the cc...while the cc to battery +ve cable goes through the other pole to the battery. So when it trips, both poles trips with your charge controller properly shutting down.

ceaser:


No, I've not tried charging each cell differently. But the two LFP AC chargers I was supplied by the battery vendor all charge at CC-CV 14.5 volts. Even LFP chargers sold online at AE all put their 12v chargers at 14.4v charging voltage. Besides, I noticed that my battery manufacturer scribbled voltage range on each cell (2.75v to 3.7v) on some and more or less on others. I guess this was done during the selection process to avoid cell mis-match which may affect performance. I'll see if I can snap a good picture to put on here.

That being said, when I was learning to get the sweet spot to charge with the CC, the BMS trips of at 14.5v. So I adjusted the charging voltage to 14.2v max. I notice that on CCs that has lithium settings, the moment you select it, the charging voltage resets from the usual 3-stage gradation to a recommended 14.4v. There is also a special lithium PWM CC that I've had for about 4 years now. It has various settings for different lithium chemistries and configurations. On it, 14.4v is the spot for 3.6v cell. I'll snap that page on the manual and upload here.

Your suggested 3.45v per cell puts the charge voltage for four cells at 13.8v which is still within the charge voltages I mentioned earlier as sufficiently giving good backup (reference to my earlier post). I think I will do some controlled trials to determine if 13.8v gives as much sweet spot as the 14.2v I presently use.

Whenever the sun is favourable and the voltage indicator on the battery gets to 14.2v for at least 3 hrs before sundown, the battery works uncharged for the next 22 hrs at a LV disconnect (user customized) of 12.2v. But this rainy period that occasionally pits the highest attainable top up at 13.5v, if the sun does not come up by 8am the following day, the 12.2v low voltage cut off point is sure to be reached by around 10am. The battery (12v/200ah) solely powers a 120 watts deep freezer, so it works the inverter 24/7.

It's intended to secure more panels within the CC's allowable limit to mitigate the effect of poor insolation during this rainy period after lockdown is fully over.

tchijioke:


Use a dual pole circuit breaker...connect it such that the pv+ve cable goes through one pole to the cc...while the cc to battery +ve cable goes through the other pole to the battery. So when it trips, both poles trips with your charge controller properly shutting down.

terrymason:
That's great!
But the double pole breaker will have same amps but the pv and batteries are of different amps (Wire rating), don't you think rhe purpose of the breaker has be defeated?

Note: Breakers are for cable protection (Panel and battery cables most times are not the same)

ceaser:


I think I will do some controlled trials to determine if 13.8v gives as much sweet spot as the 14.2v I presently use.
.

idris4r83:
kainji dam

ojeysky:


This should work but current/voltage from panel to cc and cc to battery are not similar hence getting a suitably rated breaker may be a problem there.

tchijioke:

Just get the appropriate circuit breakers for the PV side as well as the battery side...then hook them up together to create the dual pole breaker as in the pix attached.

These are two separate breakers hooked up as one.

tchijioke:

Just get the appropriate circuit breakers for the PV side as well as the battery side...then hook them up together to create the dual pole breaker as in the pix attached.

These are two separate breakers hooked up as one.

Deluxe8000:
Ups converted inverter for sale at cheap price.

ojeysky:


This should work but current/voltage from panel to cc and cc to battery are not similar hence getting a suitably rated breaker may be a problem there.

BetaTechnicians:

It is simple, the breaker should be sized for just the battery - CC connection since that's the part we're worried about, once that trips then it switches of the +ve PV input too, and note that the +ve PV input would still go into another breaker with it's -ve input before getting into the CC. Can you visualize this?

ojeysky:


I guess we are on the same page then, ultimately 2 breakers needs to be procured. Though I don't think it's necessary to connect them on a single pole, just put them separately and let them do their job. Will like to know the advantage in putting them together

ojeysky:


Breakers are mainly for equipment protection(it's possible for the wire to still be okay while the equipment is toast), what has been stated could work if the ratings of your cc to battery and panel to cc are similar. For instance my GK is 450v/18A max for PV to CC side but Inverter to battery side would be max 31v/60A (the current limit is due to BMS installed in my battery).

I personally don't have a breaker between inverter and battery but it will be good to add it, just that am not sure a single breaker will sufficiently serve both ends, you may have to get 2 breakers.

However the gurus may know better

tchijioke:


You are to connect them as individual circuit breakers then link them up with the cap as captured in the pix I posted.
Linking them to function as dual circuit breaker will ensure that both breakers trip off instantly when the need arises. Thereby controlling the battery and PV side simultaneously and by extension keeping the charge controller off harms way.

terrymason:
Have seen in various videos and setup where breakers/Fuse are put between panels and charger controller (Which is highly compulsory), but breakers in between batteries and charger controller are scary to me. Let say theirs a surge and the breaker between your battery and Cc tripped off and the one between the panel and CC is still on, what do you think will be the outcome of the CC in use.. ?

What's your input DIY Guru's, newbie and the house....

mctfopt:



You can turn off some SCC from battery at blazing sun with no issues. Though the same can't be said of some system. I'll say if your SCC doesn't have that feature, jejely don't try to add a breaker between battery and SCC.

bigrovar:


something like this happened to me recently. The breaker between my cc and battery tripped up - thus saving my house from burning down - It turns out the I undersized the cable from cc to battery. I use 25mm (a distance of about 1 meter) with current up to 90A @24v passing through the wire.. this was then compounded by what I suspect to be partial contact with the DC breaker.. wire got so hot, breaker did it's job and tripped.. All this happened in peak afternoon with a solar panels array sending about 2800w of power to the cc..

This were my respect for Victron went to a whole new level.. My victron charge controller stood there.. without a battery to send all that energy too, it just switched to the higher curve of the MPPT and switched to float..In fact it took a long time to realise what was happening because controller continued working like nothing happened.. I had to turn off the breaker from the pv to cc and then changed removed the bad wire, upgraded it to 35mm and turned the system back on.. Victron charge controller resumed charging.. The trip from the battery gave no problem at all.

Teewhy2:
House,
Does it have to be a DC breaker that has to be between the PV and CC or can someone use an AC breaker in between.
My CC is rated PV 150 volts and 70 amps, what size of breaker can I introduce between the PV and CC. In case there is lighting during rain will the breaker protect the CC by tripping off.