4p4s 304ah... build starts today

[ericfx1984]

Well it's starting right now.. 16 Eve cells.. these were originally slated to go in the new house that I'm building but for the time being we're living in the RV and I need more power ... With this heat and running the air conditioner 6 KW hours just ain't cutting it

The plan is to initially configure in 4p4s and then to do a quick charge with about 40 or 50 amps until I get closer to 90%, then do a quick reconfigure to 16p and finish up with the lab power supply...

Then reconfigure to 4p4s attached the BMS and do a quick capacity test.. unfortunately the test unit I have only draws 20 amps...

So I might do it a little bit differently I have an additional 3,000 watt inverter... I might hook it up to a heavy load and just use the BMS to calculate the draw and just time it?

 

[sunshine_eggo]

Please read and follow the guide. Don't 4P4S them unless you have the BMS installed. You'll literally need to watch each 4S group constantly to ensure things don't get away from you. If you don't have a BMS, just 16P them and set a timer to check them in a month.

If your BMS is already in use, get a cheapo and use it:

Amazon.com: 12V 100A 4S BMS Protection Board with Balancing for 18650 LiFePO4 Battery Pack : Electronics

Buy 12V 100A 4S BMS Protection Board with Balancing for 18650 LiFePO4 Battery Pack: Battery Chargers - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

www.amazon.com

https://www.amazon.com/Anmbest-Balancer-Charger-Protection-Lithium/dp/B07X6RBXWH

If you follow the guide and 4P4S them with the BMS installed, charge until the BMS trips out on the high cell. Might as well get at least one cell to 100%. If you're super lucky, you'll discover you don't need to parallel them.

 

[ericfx1984]

Please read and follow the guide. Don't 4P4S them unless you have the BMS installed. You'll literally need to watch each 4S group constantly to ensure things don't get away from you. If you don't have a BMS, just 16P them and set a timer to check them in a month.

If your BMS is already in use, get a cheapo and use it:

Amazon.com: 12V 100A 4S BMS Protection Board with Balancing for 18650 LiFePO4 Battery Pack : Electronics

Buy 12V 100A 4S BMS Protection Board with Balancing for 18650 LiFePO4 Battery Pack: Battery Chargers - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

www.amazon.com

https://www.amazon.com/Anmbest-Balancer-Charger-Protection-Lithium/dp/B07X6RBXWH

If you follow the guide and 4P4S them with the BMS installed, charge until the BMS trips out on the high cell. Might as well get at least one cell to 100%. If you're super lucky, you'll discover you don't need to parallel them.

Why would it be a problem to hit them at 35-55 amps in 4p4s while monitoring the cells without a BMS? I figured I could bring it up to 80-90% SOC, then do a final top balance @ 16p?

Then put.it back in 4p4s with the BMS...

I do have a 16s BMS... And a mpp lvx6048... I could take it out of the box and use it as a charger...

 

[sunshine_eggo]

Why would it be a problem to hit them at 35-55 amps in 4p4s while monitoring the cells without a BMS? I figured I could bring it up to 80-90% SOC, then do a final top balance @ 16p?

Because this is how people screw these up. If the human is the BMS, the BMS fails. ?

Then put.it back in 4p4s with the BMS...

I do have a 16s BMS... And a mpp lvx6048... I could take it out of the box and use it as a charger...

THAT is a winner!

 

[ericfx1984]

Because this is how people screw these up. If the human is the BMS, the BMS fails. ?




THAT is a winner!

I went ahead and bought one of those $15 bms's as a way to bring the battery up quickly.. and then I figure I'll finish the last one or two percentage points with my bench power supply..

Unfortunately I'm only charging at about 17 amps

So far the cells are staying pretty close to balanced. I started charging yesterday around noon... I'm currently sitting around 3.335v. (started around 3.3v)

I know I'm in that flat part of the charge/discharge curve... So I'm not going to see a whole lot


This is been an incredibly slow process but I know I'm dealing with a 1200+ amp hour battery lifepo4 (4p4s)

I have a couple other chargers.. and they're capable of being programmed in any fashion I like... These are remote control car chargers and they can be programmed to charge anything from Old School led acid to nickel metal hydride to lithium polymer, or custom settings making them appropriate for lithium iron phosphate... They only would add an extra 150 watts to the charge


I was considering simply hooking up one of my 60 amp charge controllers and 2p2s solar panels... Bites it's raining today tomorrow and the next day so I probably won't get much if anything out of that

 

[ericfx1984]

Well I purchased a couple of those cheap bms's ... But I didn't realize is they're only capable of charging at 10 amps a piece... Anyway I'm about 40 hours into charging... Cells look good so far ... but only 3.371v

I don't know that I really have time for all this so I think I may go about it a different way... I think I might fall one of my 200 amp common port BMS is off of the existing system.. it will bring me down to half capacity but it will allow me to charge at a much faster rate... (Before reconfiguring to parallel for a proper top balance)

 

[ericfx1984]

Well we are getting there..

I made some 6 gauge cables for my adjustable bench power supply

Put everything in parallel and hooked up the bench power supply

Currently it is at 3.592 volts and about 3.45 amps... As usual I don't trust the power supply and rather trust my voltmeter and clamp meter

A few more hours and we should be good to go I know initially when I first powered this up it was at about 10.5 amps going into the battery

 

[ericfx1984]

Well we made some progress... We're doing our capacity test as we speak

After reassembling the battery in a 4p4s configuration and attaching a 200 amp BMS, I proceeded to attach a fuse, a 3000 watt inverter, and a 1500 w heat gun... That works out to almost 1600 50 Watts on the battery or around 120 or so amp

Anyway the battery has been running on discharge for 6 hours so far and we're currently setting at 3.26 volts the cells are still showing balance within 0.004v I would call that a win..

The BMS is nice and cool, all the bus bars are nice and cool, the 1/0 wire has a slight increase in temperature but nothing concerning

And the inverter is outputting a solid 119 volts

 

[No Idea]

I know you will turn your 1500w x hrs into a capacity in watt hours but do a quick spot check on the battery cable amps with your clamp meter and also take the voltage just after you take the amp reading. It will tell you actual watts you are using throughout the test including inverter losses. So your 1500w will become something a little higher when you do your final sums.

 

[ericfx1984]

Well the test finally finished ... And it looks like I ended up at 1,332 amp hours? time for bed