Final LFP Charging settings with Batrium BMS?

[Firstascent]

Hey all,

Looking for a little input and opinion on some charging settings including the option for ramping current.

After what seems like forever, I've officially connected my eve 280ah cells to my MultiPlus II 2x120 Inverter in my RV. Now that everything is connected and doing its first official full charge I wanted to revisit my thoughts on some settings and get your input.

First off I have the Batrium BMS controlling all the Victron equipment (DVCC) and everything is connected and commicating properly via CANbus.

The attached screenshots are the various settings "currently configured", some high level settings are
1. 14.2V = 100%
2. individual cell will auto balance/bypass at 3.55v
3. I have the "option" to set a ramped current so that as the SoC increases I can lower the current. Of course this can also be turned off and be fixed.
a. 120a max current (max setting in MultiPlus)
b. The 82, 84, 87, and 90% settings are all user configurable including the percentages, the values in there are just random numbers I entered in initially.

Open to any suggestions as you know there are a ton of settings if you've ever dealt with Batrium

p.s. I will say that currently it looks like everything is charging up nice and evenly! When I first got the cells probably almost 2 years ago I hooked them up all up parallel and did an initial top balance. then the batteries sat forever. so this is a good sign the cells are healthy (last screenshot from a few min ago.)

 

[sunshine_eggo]

Hey all,

Looking for a little input and opinion on some charging settings including the option for ramping current.

After what seems like forever, I've officially connected my eve 280ah cells to my MultiPlus II 2x120 Inverter in my RV. Now that everything is connected and doing its first official full charge I wanted to revisit my thoughts on some settings and get your input.

First off I have the Batrium BMS controlling all the Victron equipment (DVCC) and everything is connected and commicating properly via CANbus.

The attached screenshots are the various settings "currently configured", some high level settings are
1. 14.2V = 100%
2. individual cell will auto balance/bypass at 3.55v
3. I have the "option" to set a ramped current so that as the SoC increases I can lower the current. Of course this can also be turned off and be fixed.
a. 120a max current (max setting in MultiPlus)
b. The 82, 84, 87, and 90% settings are all user configurable including the percentages, the values in there are just random numbers I entered in initially.

Open to any suggestions as you know there are a ton of settings if you've ever dealt with Batrium

Batrium is a poor choice for LFP. LFP genuinely requires an absorption voltage for proper charging and a float voltage like lead acid.

Batrium is great choice for most other Lithium chemistries, and that's what it was designed for. I use one for my 14S 23.3kWh NMC bank.

Setting the Remote to 14.2V means that you will experience low current overcharge every day. Your cells are full @ 3.65V at 14A. If held at 3.65V to where the current drops below 14A, you have overcharged the cells. For the purposes of top balancing, this isn't a big deal. Doing it every single day for several hours will shorten the life of the cells. Ramped targets may help, but the final stage needs to be 0A at or near 100% to avoid overcharging.

Charging to 3.45V/cell is generally regarded as maximizing cycle life due to reduced stresses during charging. This causes a trade-off of increased charge times as the current naturally tapers sooner at the lower charge voltage. Personally, I would pursue a combination of the lower charge voltage and ramped current.

It also depends on how you're charging. If charging via grid/solar, 3.45V. If plugged into shower power for extended periods, 3.375V. If charging via generator, 3.55-3.65V/cell.

p.s. I will say that currently it looks like everything is charging up nice and evenly! When I first got the cells probably almost 2 years ago I hooked them up all up parallel and did an initial top balance. then the batteries sat forever. so this is a good sign the cells are healthy (last screenshot from a few min ago.)

"Balance" refers to state of charge, not voltage. Voltage correlates to balance in the upper and lower legs of the voltage curve. 16 cells sitting at 3.38-3.39V do not necessarily indicate good balance. If they remain tightly grouped at higher voltages/states of charge, then yes, that's a very good sign.

EDIT: I want to make it clear that Batrium is a poor choice if the Batrium is controlling the charging as in this case with the Victron GX. It's perfectly fine if you plan to use it in the same way you would a DALY, JBD, etc., and the Batrium is controlling a protection relay (or relays) to isolate the battery from the system (or separately with charge/discharge protection (a relay for each). It's also very expensive, poorly documented and by many recent accounts, including my own experience, indicate that it's poorly supported.

 

[Firstascent]

Batrium is a poor choice for LFP. LFP genuinely requires an absorption voltage for proper charging and a float voltage like lead acid.

Batrium is great choice for most other Lithium chemistries, and that's what it was designed for. I use one for my 14S 23.3kWh NMC bank.

Setting the Remote to 14.2V means that you will experience low current overcharge every day. Your cells are full @ 3.65V at 14A. If held at 3.65V to where the current drops below 14A, you have overcharged the cells. For the purposes of top balancing, this isn't a big deal. Doing it every single day for several hours will shorten the life of the cells. Ramped targets may help, but the final stage needs to be 0A at or near 100% to avoid overcharging.

Charging to 3.45V/cell is generally regarded as maximizing cycle life due to reduced stresses during charging. This causes a trade-off of increased charge times as the current naturally tapers faster at the lower charge voltage. Personally, I would pursue a combination the lower charge voltage and ramped current.

It also depends on how you're charging. If charging via grid/solar, 3.45V. If plugged into shower power for extended periods, 3.375V. If charging via generator, 3.55-3.65V/cell.



"Balance" refers to state of charge, not voltage. Voltage correlates to balance in the upper and lower legs of the voltage curve. 16 cells sitting at 3.38-3.39V do not necessarily indicate good balance. If they remain tightly grouped at higher voltages/states of charge, then yes, that's a very good sign.

wait what?? oh man I could've sworn LFP didn't require absorption and float voltages, now I have to go back and look into that.

with that being said, my current settings will not allow the entire pack to go above 14.2V, nor will it allow any individual cell to go above 3.6V.
So it can never reach 3.65V nor anything above 14.2V which is 3.55V/cell

Currently I expect about a 60/40 mix of Shore power vs solar respectively. The generator is only for back up but not intended to be used.

I guess the good thing is if I change to an absorption/float charging config, it's just a few clicks to disable DVCC and have all my Victron equipment take over the charging. My Victron equipment is actually already configured for a 14.2V absorption and 13.6V float just not enabled since the Batrium has control currently.

 

[Ampster]

oh man I could've sworn LFP didn't require absorption and float voltages, now I have to go back and look into

Absorb is sometimes called the ending voltage of the Bulk stage. It is a constant voltage stage of any charger. It is not essential with LFP but it cant hurt. I let the current taper so that at the end my batteries also have a chance to balance since my balancer does not start balancing until 3.4 volts per cell. I only charge to 3.45 volts per cell and they probably stay in CV stage for a half hour or so. Float is not necessary with Lithium because they do not self discharge like Lead Acid.

 

[sunshine_eggo]

wait what?? oh man I could've sworn LFP didn't require absorption and float voltages, now I have to go back and look into that.

Like lead, LFP must be charged to a higher voltage than operating voltage.

Float isn't needed for a LFP battery in storage, but a float voltage is needed to trigger use of the non-battery power source (grid, generator, solar). If you don't have a float voltage, the MPPT will allow the battery voltage to simply drop even if PV is available.

with that being said, my current settings will now allow the entire pack to go above 14.2V, nor will it allow any individual cell to go above 3.6V.
So it can never reach 3.65V nor anything above 14.2V which is 3.55V/cell

You meant not?

It's not about going above those voltages. It's about overcharging AT those voltages. Again, charging is complete BEFORE current drops to zero. LFP cells are charged to full at 0.05C.

Currently I expect about a 60/40 mix of Shore power vs solar respectively. The generator is only for back up but not intended to be used.

In this case, I would use 3.45V and use the remote ramped current to 0A @ 99%.

I guess the good thing is if I change to an absorption/float charging config, it's just a few clicks to disable DVCC and have all my Victron equipment take over the charging. My Victron equipment is actually already configured for a 14.2V absorption and 13.6V float just not enabled since the Batrium has control currently.

I would vigorously discourage this. My MPPT 250/100 gets pissed when I turn off DVCC. I have to reset it.

Additionally, NEVER do this unless you have secondary safeties in place like a critical fault relay that isolates the battery. If you don't have this, you don't have BMS protection. Another option is to wire one of the Expansion board relays to the MPPT cut-off pins and install the two signal BMS assistant on the MP.

 

[Rocketman]

If you want to let the Victron stuff have control, you can just break the Batrium to GX link.(don’t disconnect the DVCC). Then the DVCC is working but acting under Victron controls.

But (like Sunsine said) make sure you have a way for the Batrium to go critical and disconnect the battery (I use a Kilovolt contactor). You would also want a Victron shunt in the system - Smartshunt or BMV712.

I was going to setup the Batrium charging control, but one I got to that point, other projects came up and I haven’t revisited it.

Good Luck and let us know what you finally decide to do and how you set it up.

 

[Firstascent]

Absorb is sometimes called the ending voltage of the Bulk stage. It is a constant voltage stage of any charger. It is not essential with LFP but it cant hurt. I let the current taper so that and the end my batteries also have a chance to balance since my balancer does not start balancing until 3.4 volts per cell. I only charge to 3.45 volts per cell and they probably stay in CV stage for a half hour or so. Float is not necessary with Lithium because they do not self discharge like Lead Acid.

Thanks for your input, luckily these settings are all easy to change instead of having to re-wire things like I've been doing all day haha (separate issue)

Like lead, LFP must be charged to a higher voltage than operating voltage.

Float isn't needed for a LFP battery in storage, but a float voltage is needed to trigger use of the non-battery power source (grid, generator, solar). If you don't have a float voltage, the MPPT will allow the battery voltage to simply drop even if PV is available.

I'm a little confused on this, at least in my scenario. With DVCC enabled, the Batrium controls all charging/discharging. the Multiplus, and MPPT have no control. The touchscreen display from my Cerbo even shows "External Control". Now, I haven't tested all scenarios yet but so far this is what I've seen.

You meant not?

It's not about going above those voltages. It's about overcharging AT those voltages. Again, charging is complete BEFORE current drops to zero. LFP cells are charged to full at 0.05C.

Yes, sorry, I meant "not". updated my post.
Ah, I see, when you said overcharging I thought you meant going above the voltage. Thanks for that clarification.

In this case, I would use 3.45V and use the remote ramped current to 0A @ 99%.

would I still leave my charge voltage at 14.2V and just stop when the cells are 3.45V?
I just checked, I cannot set a 0A current setting, so for now it is set to 0.1A at 99%

I would vigorously discourage this. My MPPT 250/100 gets pissed when I turn off DVCC. I have to reset it.

Additionally, NEVER do this unless you have secondary safeties in place like a critical fault relay that isolates the battery. If you don't have this, you don't have BMS protection. Another option is to wire one of the Expansion board relays to the MPPT cut-off pins and install the two signal BMS assistant on the MP.

Interesting. Since my original plan was to have the Batrium do the controlling I haven't done much testing with the Victron equipment being in control. Although I recall only turning DVCC on when I was getting the Batrium online. I didn't think it was necessary since the Victron gear supposedly plays well together, and DVCC is off by default.
I haven't done any testing at all where the Batrium was ONLY the BMS and monitoring and the Victron was in control. At minimum, the Batrium won't go anywhere.

And agreed, I wouldn't take the Batrium out of the mix for control until I wired in the extra relays. I do have the expansion board with my Watchmon Core even though currently it isn't being used at all.

 

[Firstascent]

If you want to let the Victron stuff have control, you can just break the Batrium to GX link.(don’t disconnect the DVCC). Then the DVCC is working but acting under Victron controls.

But (like Sunsine said) make sure you have a way for the Batrium to go critical and disconnect the battery (I use a Kilovolt contactor). You would also want a Victron shunt in the system - Smartshunt or BMV712.

I was going to setup the Batrium charging control, but one I got to that point, other projects came up and I haven’t revisited it.

Good Luck and let us know what you finally decide to do and how you set it up.

Ah ok, so DVCC is still needed even with Victron equipment working together. I wasn't sure on that. yup easy enough to disconnect my CAN link from the Batrium to my Cerbo.

I'm good to go on the shunt. I spent almost a month (if not longer) getting the Lynx Shunt (because I also am using the Lynx Distributors) and the Batrium shunt working in parallel accurately (installed the Batrium shunt inside the Lynx enclosure). So it's already online in my system.

Thanks, will do! I definitely have more research to do as I've learned a lot today

 

[sunshine_eggo]

Thanks for your input, luckily these settings are all easy to change instead of having to re-wire things like I've been doing all day haha (separate issue)

I'm a little confused on this, at least in my scenario. With DVCC enabled, the Batrium controls all charging/discharging. the Multiplus, and MPPT have no control. The touchscreen display from my Cerbo even shows "External Control". Now, I haven't tested all scenarios yet but so far this is what I've seen.

Correct. I was just reinforcing why the Batrium is not a good choice for LFP. It was designed for NCA/NMC/LMO, etc. (3.7V chemistries), and they have a direct voltage to SoC correlation.

Yes, sorry, I meant "not". updated my post.
Ah, I see, when you said overcharging I thought you meant going above the voltage. Thanks for that clarification.

Yep.

would I still leave my charge voltage at 14.2V and just stop when the cells are 3.45V?
I just checked, I cannot set a 0A current setting, so for now it is set to 0.1A at 99%

No. You would set remote to 13.8V (3.45 * 4) and set bypass to 3.45V. 0.1A @ 99% should be fine.

 

[Firstascent]

No. You would set remote to 13.8V (3.45 * 4) and set bypass to 3.45V. 0.1A @ 99% should be fine.

got it, thanks! I'll set it this way for now until I dive deeper into this. really appreciate all the info!

 

[sunshine_eggo]

got it, thanks! I'll set it this way for now until I dive deeper into this. really appreciate all the info!

If you have to charge via generator, set to 14.4V Remote and 3.55 bypass (to start balancing a little early).

Not sure if you're aware of it, but if you need to chase balancing issues, the Batrium has an AutoLevel feature that makes it a little more flexible and intelligent.

 

[Firstascent]

If you have to charge via generator, set to 14.4V Remote and 3.55 bypass (to start balancing a little early).

Not sure if you're aware of it, but if you need to chase balancing issues, the Batrium has an AutoLevel feature that makes it a little more flexible and intelligent.

Why would the generator charging algorithm be different than shore power? It wouldn’t know the difference it would just see the 120vac as an AC input. I have an ATS with generator priority so even if connected to shore power, if the generator is running it will switch to that circuit.

Yes I actually have Auto Level enabled already instead of the traditional Batrium bypass. Still playing with settings there but it’s currently enabled.

 

[sunshine_eggo]

Why would the generator charging algorithm be different than shore power? It wouldn’t know the difference it would just see the 120vac as an AC input. I have an ATS with generator priority so even if connected to shore power, if the generator is running it will switch to that circuit.

You don't care if you pull less power from shore as it all costs the same. Lower current from a generator burns more fuel per kWh, e.g.,

3kW generator:
6kW charged in 2.5 hours uses less total fuel than
6kW charged in 4 hours due to increase absorption time.

I have seen a handful of small Onan generators with a fuel burn along the lines of:

1 gal per hour at 50% output.
1.1 gal per hour at 100% output.

That 50% output will cost you almost 90% the fuel that 100% output.

In reality, the sweet spot is about 70-80% max continuous to balance wear-and-tear and fuel efficiency.

Yes I actually have Auto Level enabled already instead of the traditional Batrium bypass. Still playing with settings there but it’s currently enabled.

If you enable auto level, you disable the bypass voltage function.

Please screen cap your auto level settings.

 

[callmeburton]

Grabbing some popcorn since I also have a batrium with LFP ... have some thoughts but will get back to it later.

 

[sunshine_eggo]

Grabbing some popcorn since I also have a batrium with LFP ... have some thoughts but will get back to it later.

Expressed thoughts are far more useful than popcorn.

 

[callmeburton]

I agree, and I have saved the beginning of them in a notepad ... I have to dive into the batrium documents some more and don't have time right now as I am working, then later going to gym then sleep etc. Just tagging this so I can keep track of replies and find it easier later (hence the popcorn )

 

[sunshine_eggo]

I wouldn't put a lot of weight into the Batrium documents. They're outright atrocious. The docs for the Victron configuration are 100% wrong unless they've been updated in the last 6 months.

This isn't just simple BMS configuration or use. It's about allowing the Batrium to control the charge parameters of the equipment.

If you're going to use the Batrium with LFP like you would a DALY, Overkill, etc., without communication, then it's fine.

 

[Firstascent]

You don't care if you pull less power from shore as it all costs the same. Lower current from a generator burns more fuel per kWh, e.g.,

3kW generator:
6kW charged in 2.5 hours uses less total fuel than
6kW charged in 4 hours due to increase absorption time.

I have seen a handful of small Onan generators with a fuel burn along the lines of:

1 gal per hour at 50% output.
1.1 gal per hour at 100% output.

That 50% output will cost you almost 90% the fuel that 100% output.

In reality, the sweet spot is about 70-80% max continuous to balance wear-and-tear and fuel efficiency.



If you enable auto level, you disable the bypass voltage function.

Please screen cap your auto level settings.

Sorry for the delay, yesterday was a travel day

ah yes, completely makes sense on the generator, charge up faster to use less fuel. I was thinking at it from a charging/balancing perspective not from a fuel efficiency perspective.

Here are my current Auto Level settings

 

[Firstascent]

I wouldn't put a lot of weight into the Batrium documents. They're outright atrocious. The docs for the Victron configuration are 100% wrong unless they've been updated in the last 6 months.

omg yes, I started following the Victron configuration awhile back then figured out quickly it's just wrong haha.

 

[Zwy]

I wouldn't put a lot of weight into the Batrium documents. They're outright atrocious.

Understatement. When I went to go live with the Batrium, I had watched the videos on hooking up the Shuntmon and how to setup in the software. It showed my battery voltage at 300+V.

Really strange I thought. Then ran across this page and scrolling down found the Shuntmon Rev3.2 has a high voltage side and a low voltage side. Swapped the wire and sure enough, it read the correct pack voltage.

It's always little things here and there. If you have K9's, the only videos out there are from people using the K9 like Lithium Solar when he first built the LFP bank. Go to documentation, it's not easily found or non existent. You do better watching the older videos, much of the older hardware was just repackaged as a K9, same function for much of it. One beef is the bypass test with a K9, it will let you know it needs a bypass test and it will most likely fail on some cells but if you go here, (and I really had to look for the information), you will find this jewel:

Each device is progressively run to warm up during the testing session to confirm that the bypass function works. The verification test is aimed at BlockMons, LongMons, and LeafMons rather than the CellMate-K9 since these do not have heatsinks attached and are much easier to detect a thermal change.

Watched a video (from Batrium on Youtube) about bypass function before I found that info and he did mention something about the K9 to turn off the fans if had them installed and some options that could be done to help the test run. I figured out on my own to just set if for 1C temp increase and put a towel over the K9 and it would pass. I wanted to ensure bypass would work before charging.

The docs for the Victron configuration are 100% wrong unless they've been updated in the last 6 months.

This isn't just simple BMS configuration or use. It's about allowing the Batrium to control the charge parameters of the equipment.

If you're going to use the Batrium with LFP like you would a DALY, Overkill, etc., without communication, then it's fine.

I use mine without comm, I don't see the point. Works well but it tripped the ABB this morning early and I never found what fault it saw. It still had over 40% SOC when I checked it a half hour earlier. I did have a K9 comm cable that wouldn't let the last K9 in the chain power up, had another cable and it worked fine, tried the original cable after ohming it out (was fine) released each ferrule and made sure it was crimped well on the wire and reinserted it, worked fine after. This post just got me thinking maybe that was the cause of the fault this morning.