Exactly HOW does the BMS Stop the Charging Process?

[hwy17]

Soooo.... in my configuration... the only real issue is... that the charger is going to go to 100% and oh, wait... no... the BMS can stop the flow in charge mode at 90% because... it's a DIODE! Right?

The BMS *could* if it has the settings, cut off the FETs at 90% SOC. But that would be a bad way to do that. If you want a charge to stop at 90% you generally need more advanced comms and controls than what you have in your diagram.

I would let go of the 90% desire, unless you strongly hold it for some reason. If you do, then your design will have to get more complicated.

I do have mid SOC charge shutoff control desire in my design, and here's where I am getting to with that:

hwy17's battery build

Rather than keep spamming new threads out as thoughts come up I'm starting a build thread now to share as I go. 16x EVE 304 from Ezeal Orion JR2 BMS Planning work in progress (polarity not detailed yet):

diysolarforum.com

 

[bass-o-matic]

I would let go of the 90% desire, unless you strongly hold it for some reason. If you do, then your design will have to get more complicated.

I like your world view here. So, if I let go of the 90% thing. It just means the batts won't last as long right? Keep in mind that I was planning on keeping my trailer plugged in... as it sits in my driveway under a cover 90% of the year.

 

[hwy17]

I like your world view here. So, if I let go of the 90% thing. It just means the batts won't last as long right? Keep in mind that I was planning on keeping my trailer plugged in... as it sits in my driveway under a cover 90% of the year.

Yes but you can also manually mid level it. Charge it up, let it discharge to 80%, disconnect the charger and battery, and let it sit at 80%. You will just need to remember to go charge it again within about 6-12 months before it falls below 20%.

 

[upnorthandpersonal]

I like your world view here. So, if I let go of the 90% thing. It just means the batts won't last as long right? Keep in mind that I was planning on keeping my trailer plugged in... as it sits in my driveway under a cover 90% of the year.

Put your charger to 3.5V per cell or so for bulk charging, and set float to 3.25V or something per cell. That way, your charger will kick in when the battery drops below that and recharge until full. If there are no loads connected except for the BMS, this won't happen very often.

 

[bass-o-matic]

Put your charger to 3.5V per cell or so for bulk charging, and set float to 3.25V or something per cell. That way, your charger will kick in when the battery drops below that and recharge until full. If there are no loads connected except for the BMS, this won't happen very often.

I think that is the problem. My charger cannot be programmed.

 

[hwy17]

I can get my 48v 18A EG4 charger into float today and record it. Then maybe we can guess the 12v is a quarter of that.

Unfortunately EG4 does not list this voltages in the manual.

@SignatureSolarJess Any chance you can get the 12v 30A float voltage spec for us?

 

[SignatureSolarJess]

Yes you are correct. 54v / 4 = 13.5v

 

[upnorthandpersonal]

Yes you are correct. 54v / 4 = 13.5v

That's 3.375V per cell so @bass-o-matic - you should be fine.

 

[bass-o-matic]

Wow! Thanks everyone!

I thought of another simple strategy around the idea of manually mid-leveling.

I really don't draw that much. I could just put my charger on a timer and have it shut off after eh.... 5 hours... not sure... then just watch my battery monitor and charge up the batts again every few months. Really, I draw nothing.

I'm just having fun with the whole LifePO4 thing. It's a very OCD Hobby! Who knew! (I miss Lead Acid. )

 

[bass-o-matic]

Let the festivities begin! Out with130lbs of Tongue weight and Lead Acid!

 

[hwy17]

I have confirmed my 48v 18A EG4 was floating at 53.26 when I checked it.

 

[bass-o-matic]

I have confirmed my 48v 18A EG4 was floating at 53.26 when I checked it.

Awesome! I love this group.