Lithium battery charger conflicts in recommendation.

[booster]

Moderate term lurker here just signed up.

I have been closely following the tech side of lithium batteries since the early days and never determined they were worth the cost penalty and downsides vs AGM. The price thing has mostly relieved itself and my 440ah of Lifeline AGMs are getting near aging out so I decided to put in a bank of SOK 206ahX3 12v batteries to test and see if they are worth the close to 50% cost difference to us in our 07 Roadtrek 190 RV. We have 300 watts of solar on a Blue Sky controller with Pro remote so it can charge to tail amps. Shore charger is a 100 amp Magnum MS2000 with ARC-50 remote which will also charge to tail amps and do full cutoff/rebulk charging with no float. Alternator charging is from 530 amps of dual alternators that can give 200 amps continuous and 300 amps for about 20 minutes before getting to hot. I have a dash ammeter off the batteries to see tail amps and can lock the remote regulator into absorption for constant output. All three have temp compensation turned off for lithium. The three batteries can handle 120amps total at recommended rate and 150 or 210amps depending on who you believe. I have the Bluetooth so I can see individual cells on each battery.

The recommendations from SOK say to charge to 14.4-14.6v and hold 10 minutes to activate and give time to the auto balancing they use.

The problem in deciding is because there is lots of information and tech papers recently saying charging to a lower voltage like 13.8v is better than higher as the higher voltage shortens life. Some say go to 13.8v and cutoff and some say hold until a low amperage like 1%C is reached.

My guess is that the lower voltage is better but then you lose the auto balancing initiation which is probably needed, but maybe not on every cycle. I have tested the charge to 13.8v and hold until 1%C and the batteries got to a nice 90-95% SOC so decent headspace, where if I shut off immediately in was closer to 85%. At 14.6v and immediate shutoff it about the same 90-95% and with the hold time gets into the headspace too far it appears.

If the 13.8v is the better of the two I think the obvious solution was to put active balancers on each of the batteries, with a common shutoff for the balancers, if I find the balance is going off after some period of time/cycles that I would need to test for. I have found no real testing on this issue to this point so flying kind of blind.

Anybody got opinions or experience the this type of quandary?

 

[Tomthumb62]

LOL, welcome to the various sects of how to best charge lithium.

My current method is to use solar to charge to 14.0v. I use shore power charging once a week or so to charge to 14.4v

I don’t have SOK batteries, but a single 12v 200Ah Powerurus lifepo4. They said any voltage above 13.8v will trigger the balancing function. I don’t know how to verify this, but so far (14 cycles so far), I’m seeing a 0.006 to 0.010 delta, under load. My loads are typically not more than about 8ADC.

 

[booster]

Thanks for the answer, I think your battery balancing setup is much better than the SOK, and also Battleborn and others. They are at 14.4v activation on the balancing so no way to avoid the high voltage, and they want it on every recharge. Doesn't make a lot of sense to me.

 

[Brucey]

LOL, welcome to the various sects of how to best charge lithium.

My current method is to use solar to charge to 14.0v. I use shore power charging once a week or so to charge to 14.4v

I don’t have SOK batteries, but a single 12v 200Ah Powerurus lifepo4. They said any voltage above 13.8v will trigger the balancing function. I don’t know how to verify this, but so far (14 cycles so far), I’m seeing a 0.006 to 0.010 delta, under load. My loads are typically not more than about 8ADC.

I ended up getting a Redodo 12v 100Ah "mini" (using pouch cells) rather than Powerurus. I reached out to their support to see what their recommended charge profile is. I did initial charge with these settings I found on victron forums

 

[Tomthumb62]

My limited understanding is that it’s not necessary for the higher voltage EVERY charge cycle to balance the battery. But this is a general rule and a specific BMS might require otherwise. You might ask their tech support for more specifics as to whether or not you can get away with only charging to 14.4v once or twice a week.

Also there are those like Will Prowse who claim that he uses his batteries 0% or 10% to 100% every single day and that the battery cells will die of calendar aging sooner than babying a battery at 20-80%. This is why it’s a religion. There are the lifepo4 scientists who see a certain perspective and then real world users who see another. It’s going to be another 10-20 years before we know where the truth actually lives.

My hunch is the truth depends upon a person’s use case, environmental conditions and more. In other words, I’m not going to worry about it too much.

But do probe SOK a bit more for details about why they are so adamant about 14.4v EVERY cycle for balancing purposes, since this isn’t the typical trend. They might be trying to cover their asses for their cycle count and capacity claims and keeping batteries as balanced as possible is a good way to do that.

Also, the kind of passive balancing that these BMS’s use can sometimes take months to correct. An expensive active balancer can do it quicker. Since your SOK can be opened up, perhaps an active balancer could be added. But you’d only want to do that if you end up with a big out of balance issue.

Enjoy your battery and watch the trend of your deltas.

 

[Tomthumb62]

I ended up getting a Redodo 12v 100Ah "mini" (using pouch cells) rather than Powerurus. I reached out to their support to see what their recommended charge profile is. I did initial charge with these settings I found on victron forums

View attachment 164233

That’s the “typical manufacturer recommended charge profile” for many lifepo4 batteries.

Based upon lots of reading on the subject, this is what I’ve come up with. Mind you my settings for the Victron shore charger are more aggressive than my solar charge controller. This is for a 12v 200Ah

 

[booster]

But do probe SOK a bit more for details about why they are so adamant about 14.4v EVERY cycle for balancing purposes, since this isn’t the typical trend. They might be trying to cover their asses for their cycle count and capacity claims and keeping batteries as balanced as possible is a good way to do that.

Also, the kind of passive balancing that these BMS’s use can sometimes take months to correct. An expensive active balancer can do it quicker. Since your SOK can be opened up, perhaps an active balancer could be added. But you’d only want to do that if you end up with a big out of balance issue.

My limited understanding is that it’s not necessary for the higher voltage EVERY charge cycle to balance the battery. But this is a general rule and a specific BMS might require otherwise. You might ask their tech support for more specifics as to whether or not you can get away with only charging to 14.4v once or twice a week.

Also there are those like Will Prowse who claim that he uses his batteries 0% or 10% to 100% every single day and that the battery cells will die of calendar aging sooner than babying a battery at 20-80%. This is why it’s a religion. There are the lifepo4 scientists who see a certain perspective and then real world users who see another. It’s going to be another 10-20 years before we know where the truth actually lives.

My hunch is the truth depends upon a person’s use case, environmental conditions and more. In other words, I’m not going to worry about it too much.

But do probe SOK a bit more for details about why they are so adamant about 14.4v EVERY cycle for balancing purposes, since this isn’t the typical trend. They might be trying to cover their asses for their cycle count and capacity claims and keeping batteries as balanced as possible is a good way to do that.

Also, the kind of passive balancing that these BMS’s use can sometimes take months to correct. An expensive active balancer can do it quicker. Since your SOK can be opened up, perhaps an active balancer could be added. But you’d only want to do that if you end up with a big out of balance issue.

Enjoy your battery and watch the trend of your deltas.

 

[booster]

I did contact the seller which is Current Connect and all I got was same thing about balancing the SOK posts and tells everyone. I was unable to get a hold of Dexter however.

The adding of active balancers to them is my go to if I do get unbalanced cells, as I mentioned in my original post. We will be going on a month long trip this fall and will probably just never plug in because it so convenient that way because then you can just drive a class b away with taking in a cord that may be wet or muddy if it is raining.

 

[Tomthumb62]

The adding of active balancers to them is my go to if I do get unbalanced cells, as I mentioned in my original post. We will be going on a month long trip this fall and will probably just never plug in because it so convenient that way because then you can just drive a class b away with taking in a cord that may be wet or muddy if it is raining.

We also took a long trip recently and found that our battery would last us 54 hours without a charge. Rain, clouds and thick forest prevented any solar charging. All we had to do was pack up and drive to a place we could plug in. We were trying to do a hike and spent some valuable sun time trying to find a safe and sunny place to park near the trailhead. We also didn’t want to set out the additional 200w of portable panels to add to the charge, and leave them for possible theft. LoL these are problems of a modern society.

While the sun did keep our fridge running in the warm weather, there wasn’t enough to also charge the battery much, hence needing to plug in at the end of the day. We rolled in with 0.5Ah left, according to the BMS.

Edit to say that the portable panels weren’t much use in the thick forest, as the 25’ cord couldn’t quite reach the best sun location. Time to upgrade that cord…

 

[booster]

We also took a long trip recently and found that our battery would last us 54 hours without a charge. Rain, clouds and thick forest prevented any solar charging. All we had to do was pack up and drive to a place we could plug in. We were trying to do a hike and spent some valuable sun time trying to find a safe and sunny place to park near the trailhead. We also didn’t want to set out the additional 200w of portable panels to add to the charge, and leave them for possible theft. LoL these are problems of a modern society.

While the sun did keep our fridge running in the warm weather, there wasn’t enough to also charge the battery much, hence needing to plug in at the end of the day. We rolled in with 0.5Ah left, according to the BMS.

Edit to say that the portable panels weren’t much use in the thick forest, as the 25’ cord couldn’t quite reach the best sun location. Time to upgrade that cord…

How much engine charging do you have when you drive? That will be our main source of recharging if the sun doesn't shine or we use more than the solar can put out, which in our case is somewhere around 90 amp hours or a bit more on a good day. On engine charging we can get that is about 25 minutes now and when I determine all is good, I will turn it up from 110amps to 120-130, maybe with a second option of 160 or so if decide we need it, but that isn't likely. We have plenty of capacity to use 100amps per day for 3 days and only be at 50% and we typically drive at least some in 3 days and it doesn't take long to get back a couple of days worth of charge. Our intent is to be so we don't ever need to plug in unless we need AC in extremely hot conditions, then we will look for shore power or use it if the site happens to have it.

 

[Tomthumb62]

How much engine charging do you have when you drive? That will be our main source of recharging if the sun doesn't shine or we use more than the solar can put out, which in our case is somewhere around 90 amp hours or a bit more on a good day. On engine charging we can get that is about 25 minutes now and when I determine all is good, I will turn it up from 110amps to 120-130, maybe with a second option of 160 or so if decide we need it, but that isn't likely. We have plenty of capacity to use 100amps per day for 3 days and only be at 50% and we typically drive at least some in 3 days and it doesn't take long to get back a couple of days worth of charge. Our intent is to be so we don't ever need to plug in unless we need AC in extremely hot conditions, then we will look for shore power or use it if the site happens to have it.

We have zero engine charging. It’s not a van but a trailer. Cost of installing a decent DCDC charger with appropriate sized cabling would be about $400 DIY. Our problem was camping in the thick woods but it was at a sentimental family camp. Longer cord for the portable panels would have solved our issue as we could’ve gotten a solid 4-5 hours of sun, which would’ve ran our fridge and given a partial charge.

 

[Brucey]

That’s the “typical manufacturer recommended charge profile” for many lifepo4 batteries.

Based upon lots of reading on the subject, this is what I’ve come up with. Mind you my settings for the Victron shore charger are more aggressive than my solar charge controller. This is for a 12v 200Ah

View attachment 164237

Thanks Tom. Redodo support did confirm 14.6V and 13.8V. I may drop down to 14.3 or so as I don't need 100% capacity. I do wish they had Bluetooth like the powerurus so I could see cell balance etc but I guess that's why there's a price gap ($400 versus $310). Next step, get a Victron 12/1200 inverter.

 

[Tomthumb62]

I do wish they had Bluetooth like the powerurus so I could see cell balance etc but I guess that's why there's a price gap ($400 versus $310). Next step, get a Victron 12/1200 inverter.

To me that price gap is priceless. If the cells are really out of balance, I can see it and know why my battery is struggling.

Don’t know if I mentioned or not, but I have that Victron 12/1200. It ROCKS. If you intend to take advantage of the ECO mode, be sure to buy the Bluetooth dongle so you can adjust the settings. The default settings didn’t work with my fridge and there’s no way to change them without the dongle and Victron Connect app.