Recommended new rack battery charging?

[flammafeuer]

I've got a 2-unit Aolithium rack battery set coming soon, and I'm reading up on charging. Right now, I have a Victron 150/35, and was planning on using solar to charge. I noticed that most people seem to have a dedicated charger for getting their batteries initially charged up. Is solar still a reasonable way to charge a new rack battery? If not recommended, what chargers or methods do you recommend?

 

[sunshine_eggo]

I've got a 2-unit Aolithium rack battery set coming soon, abs I'm reading up on charging. Right now, I have a Victron 150/35, and was planning on using solar to charge. I noticed that most people seem to have a dedicated charger for getting their batteries initially charged up. Is solar still a reasonable way to charge a new rack battery? If not recommended, what chargers or methods do you recommend?

PV charging is fine. Recommend charging to 3.45V/cell and holding there for a combined total of 12hr (okay to split across multiple days) or until all cells equal 3.45V.

 

[Steve_S]

I've got a 2-unit Aolithium rack battery set coming soon, and I'm reading up on charging. Right now, I have a Victron 150/35, and was planning on using solar to charge. I noticed that most people seem to have a dedicated charger for getting their batteries initially charged up. Is solar still a reasonable way to charge a new rack battery? If not recommended, what chargers or methods do you recommend?

Assembled packs by AOLithium, SOK, EG4 etc are all top balanced & charged & tested prior to assembly, so this is generally not a problem. The only GOTCHA is that the packs may be a slightly different voltage when they arrive, most likely just above 3.2V per cell (51.2V for a 48V Pack) so when you first install them into the rack, before turning anything else on, turn on the battery packs and let them balance out between themselves. If you have the ones that can be controlled with a phone APP, you will see power being transferred back & forth as they balance out, once they have settled (showing same voltage & no amps being used) then power up your solar charger controller followed by your inverter/charger.

Note I am assuming you have a separate Inverter/Charger as you are using a Victron SCC. You can also use the Charger in the Inverter which can be Generator or Grid Power. You CAN charge with the Inverter/charger AND the SCC simultaneously "provided" that you do not exceed the Max Amps the battery packs can take.

AOlithium 48V/100AH Rack Packs have an EndAmp/TAILCURRENT of 5A (see settings in SCC) When packs reach Tailcurrent, they flip to FLOAT mode (constant voltage / variable current) from ABSORB (should be a max of 60min, will kick off earlier as Tailcurrent is reached).

!! WARNING !! Correct for Voltage Differential !
When charging from Solar AND/OR Inverter/Charger:
Use a Multimeter and check the voltage at the SCC or Charger and again at the battery pack terminals, note the difference. There is always a bit of difference because every lug, wire, connection like fuse/breaker adds resistance & a bit of loss results. LFP unlike Lead Acid is MILLIVOLT & MILLIOHM sensitive (not brute force). Adjust your Solar Controller & External Charger (as applicable) so that the Battery Packs are getting what they are supposed to get and not more.
-- Now the part everyone hates....
You have to do it AGAIN when there is NO Solar Input and the inverter is powering normal loads. The "bias" is different when discharging and it can be enough to cause issues... You NEED to ensure that the Low Volt Shutdown of the inverter is accurate or else it may disconnect too late with the batteries being too low causing the BMS to shutdown and not take a charge.

Good Luck, Hope it helps.

Here is a quick reference you may find helpful

 

[sunshine_eggo]

Assembled packs by AOLithium, SOK, EG4 etc are all top balanced & charged & tested prior to assembly, so this is generally not a problem.

I don't believe this for a second, or if it's done, it's not done in a way that ensures the customer consistently receives a top balanced battery. Posted issues of imbalance with SOK and EG4 are pervasive on this board. There's been at least a couple of AOlithium, but they seem lower volume.

Unless you're using near perfect matched cells, a shelf sit of a couple of weeks can throw the balance out enough to trigger charge protection.

@HighTechLab care to comment?

 

[HighTechLab]

SOK is charge and discharge tested, but not top balanced in the typical sense (all cells paralleled and charged to 3.65). Despite this, the packs still output well over their rated capacity.

The BMS dials in the balancing on the first handful of cycles. Even if we shipped the packs from China perfectly top balanced, in the minimum 3 months (I've seen customers let them sit up to a year) between leaving the factory and being installed, there would still be some balancing work for the BMS to do no matter what. This is why I've done extensive testing on the SOK BMS to be sure that repeated OVP triggers won't damage it.

I asked the factory to top-balance first when we started manufacturing...but realized it's pointless and impractical. Time has proven to me that the cells show up to assembly so close together that further balancing aren't adding any value, but do add a significant cost.



Sidenote; I have contacted a few different factories that do top balance to 3.65 before assembly...but almost always end up learning it's because they are using B-grade or recycled cells that don't stand a chance without being balanced. A lot of the time they will also slap in an active balancer to mask what's really going on with the cells. I have zero interest dealing with the problems that come from packs made like this and part of why I stopped working with BigBattery a long time ago.