Stopping Inverter at 90%

The_Breeze

The Breeze
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I've been reading Will's posts and watching his vids. In here (re:https://diysolarforum.com/threads/r...e-for-diy-lifepo4-batteries-sticky-post.5101/), he describes the desired charge profile for 12V 4S LiFePO4 Battery w/ BMS as:
Absorption: 14.5V
Float: 13.6V
Inverter Cut-off: 10.7V-12V (depending on size of load and voltage drop etc)

I have 4-BB 100ah batteries (NIB) that will be connected to an AIMS 2500w inverter charger (PICOGLF25W12V120AL) using a 8ft 4/0 welding cable run. They have a built in BMS. I'll be using a generator and shore power to charge the batteries until I can get some solar set up (phase 2 of the project)

Will recommends stopping the charger at 10.7-12v 'depending' but doesn't mention where he's taking that measurement. I've read other posts in here that suggest it should be what the inverter sees, opposed to what the batteries say. He goes on to mention that to extend the live of a 12v battery for 5,000+ Charge Cycle Absorption Recommendation: 12V Battery: 14.1V

The inverter doesn't seem to allow the flexibility needed to follow this advice, or I just don't understand the inverter well enough. It does have a 'Charge Rate' adjustment and I was wondering if I could use that somehow. I'd contact AIMs but they don't answer inquiries, so another lesson learned too late and I'd really hate to try and wing it.

My questions are:
1) Where should the measurement be taken? At the inverter?
2) The inverter only understands volts. If I use @MisterSandals chart, I see 90% 13.3v Can I somehow limit the charge rate and possibly intervene when the measured volts reach the 13.3v?
3) Anyone else have this setup and find away to achieve the desired outcomes mentioned above?




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time2roll

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Under what situation would you want the inverter to actually run the battery dead? I assume no normal situation should put you in this spot. I would avoid this situation except for some unforeseen emergency in which case it will be the BMS or inverter that involuntarily cuts power. Either build more battery to avoid shut down or monitor power to turn the inverter off manually. Or even check the battery level before you turn on the inverter.

As an alternative you may need a battery monitor to monitor total power available. Or you may need an autostart generator.
 

mikefitz

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Where should the measurement be taken? At the inverter?
I suggest the battery.
If I use @MisterSandals chart, I see 90% 13.3v Can I somehow limit the charge rate and possibly intervene when the measured volts reach the 13.3v?
This chart is for the resting voltage of the battery, to charge the applied voltage must be higher. Any charge voltage over 13.6 will eventually charge to full.
BB suggest a charge voltage of 14.2 to 14.6. There is not a lot you can do to prevent charging to 100% without additional equipment and there may be disadvantages in attempting this with 'drop in' ready built batteries.

It seems with the AIMS charger /inverter you have to live with the preset values.

Mike
 

Just John

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You want to have the inverter stop before the BMS decides to protect the battery.
Since you are asking about inverter shut off, unless you are using something else to trigger turning off the inverter, the inverter can only read the voltage at its own battery terminals.

I for one can't answer your question, but Battleborn can. I don't know the settings on their BMS, or even what chemistry their cells are. Chemistry and BMS settings are what would determine the correct voltage to tell the inverter to turn off, and the inverter will read the voltage from the battery input terminals.

Battleborn likely has the answers you seek, and will likely answer them if you ask. The voltages Will gives are for LiFePO4.
 

The_Breeze

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Thanks folks. Really. mY attempt at answers follows.
Under what situation would you want the inverter to actually run the battery dead? I assume no normal situation should put you in this spot. I would avoid this situation except for some unforeseen emergency in which case it will be the BMS or inverter that involuntarily cuts power. Either build more battery to avoid shut down or monitor power to turn the inverter off manually. Or even check the battery level before you turn on the inverter.

As an alternative you may need a battery monitor to monitor total power available. Or you may need an autostart generator.
I do not want to run the battery dead? I only sought to charge only to 90% in lieu of 100% in an attempt to get more lifecycles out of it, if Will's assertions are correct. Not sure where that came from and my regret if the question wasn't clear.

Battleborn is the source of answers. They have their own BMS, and I'm not sure they even use LiFePO4 cells (the voltages change depending on the chemistry).
They claim LiFePO4?: https://battlebornbatteries.com/product/12v-lifepo4-deep-cycle-battery. I had no idea the chemistries differed?
I will go to them with the question. I will mention Will Prowse and hope they don't read the post like I have 3 heads.

I suggest the battery.

This chart is for the resting voltage of the battery, to charge the applied voltage must be higher. Any charge voltage over 13.6 will eventually charge to full.
BB suggest a charge voltage of 14.2 to 14.6. There is not a lot you can do to prevent charging to 100% without additional equipment and there may be disadvantages in attempting this with 'drop in' ready built batteries.

It seems with the AIMS charger /inverter you have to live with the preset values.

Mike
That's sort of what I thought. The inverter has a LiFePO4 charge profile and BB says they're LiFePO4. Isn't the chemistry standard?

I'll pose the question to BB however, I suspect I'll have to place something between the inverter and batteries to achieve the recommended 90% charge. I close the loop with their answer.

Here's what I put to them:
"I purchased 4 BB 100ah LiFePO4 batteries. I'm reading info on DIY Solar and came across a post by Will Prowse, who seems to be a respected source on battery/solar topics, that suggests I can get more cycles out of my batteries if I only charge them to 90% instead of 100 and never discharge them below 20% (re:https://diysolarforum.com/threads/r...e-for-diy-lifepo4-batteries-sticky-post.5101/).

Can you confirm this and explain a little bit about how your internal BMS works (e.g. what are it's parameters?). If you can point me to something I can download and keep for future refernce, that would be great too.

Thanks for your time"
 
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MisterSandals

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I only sought to charge only to 90% in lieu of 100% in an attempt to get more lifecycles out of it, if Will's assertions are correct. Not sure where that came from and my regret if the question wasn't clear.
You should be looking at your charge controller settings to limit the charging. Not sure why your inverter is part of this discussion...
 

The_Breeze

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You should be looking at your charge controller settings to limit the charging. Not sure why your inverter is part of this discussion...
This is Phase 1. The charger is in the inverter (for now). It has the required charge profile. I haven't any solar yet, so charging will be done with shore power or the generator via the inverters built-in charger. Solar and its necessary components have to be Phase 2.

I'm grappling with addiotanl info I've come to learn. If the true desire is to only charge to 90%, the current lead acid charger in my RV will accomplish that. According to the manufacturer, they see that as a flaw, where Will sees it as a definte plus. The manufacturer claims the my curren chanrge controllerr will only charge LiFePO4 85-90% of capacity. What I DON'T know is if it'll destroy the batteries. They calim it won't - just not charge to 100%.


My question:
"Is the 8955PEC suitable for charging Lithium-ion batteries? I would like to upgrade from lead acid/AGM to lithium in gradual steps toward solar"?

Their answer:
"The converter you have is not an actual lithium converter but will charge to approx.. 90%. We do have a direct replacement converter that is lithium Part# WF-8950L2-MBA".
 
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mikefitz

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Is the 8955PEC suitable for charging Lithium-ion batteries?
This the the method of operation of the converter charger,
the charge graph is below.
The charge voltages and float values are within the recommendations produced by BB. It will charge your batteries to 100%. Any voltage over 13.6 volts will over time charge to near 100%.

Be realistic about charge cycles, even if you used the batteries full to empty every day, 2000 cycles is over 5 years. Even after 5 years the batteries are still usable, just less capacity than new.

The only way you can realistically control the point the terminate charge below 100% is to use a battery monitor like the Victron BMV712 and set its programmable relay to cut charging at a set capacity.

There are other issues to consider when using Battleborne batteries, in that regular internal balancing should take place. I suggest you approach BB for your charging advice, operating outside their recommendations may effect your warranty.
You will stress the batteries less by operating at the lower limits of BB suggest values. Remember the batteries have natural ageing even if you never cycle them.
converter charger.jpg
Mike
 

The_Breeze

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This the the method of operation of the converter charger,
the charge graph is below.
The charge voltages and float values are within the recommendations produced by BB. It will charge your batteries to 100%. Any voltage over 13.6 volts will over time charge to near 100%.

Be realistic about charge cycles, even if you used the batteries full to empty every day, 2000 cycles is over 5 years. Even after 5 years the batteries are still usable, just less capacity than new.

The only way you can realistically control the point the terminate charge below 100% is to use a battery monitor like the Victron BMV712 and set its programmable relay to cut charging at a set capacity.

There are other issues to consider when using Battleborne batteries, in that regular internal balancing should take place. I suggest you approach BB for your charging advice, operating outside their recommendations may effect your warranty.
You will stress the batteries less by operating at the lower limits of BB suggest values. Remember the batteries have natural ageing even if you never cycle them.
View attachment 51095
Mike
Thank you Mike. I will contact them again. I hope they don't mind all the newb questions. Don't want to wear out my welcome - here or there. I read the details on the BMV 712. It does not mention cutting off the charge? Some useless background: I am living in an RV until I decide to exit the lifestyle. It's likely I cycle the batteries often, so when I saw Will's post I became very interested and thought it may be good advice to practice. I also don;t need Bluetooth, so something in the 700 series would be a more desirable price point (e.g. https://www.ebay.com/itm/164396737791?epid=13028340125&hash=item2646cf24ff:g:CFUAAOSwOTZfapd5)

The BB batteries have an internal BMS. Will that take care of the internal balancing or are you refering to a separte process and additional equipment.

I may have misunderstood your advice and that wouldn't be unlikely. Please excuse my ignorance. I'm literlly 'just getting started'. Always feel free to point me to a valuable source rather than take the time to explain. I'm in this to learn as much as I can as well as do as much as I'm capable.

"Battery "fuel-gauge", time-to-go indicator, and much more - The remaining battery capacity depends on the ampere-hours consumed, discharge current, temperature and the age of the battery. Complex software algorithms are needed to take all these variables into account. Next to the basic display options, such as voltage, current and ampere-hours consumed, the BMV-700 series also displays the state of charge, time to go, and power consumption in Watts. The BMV-712 features an additional input which can be programmed to measure the voltage (of a second battery), battery temperature or midpoint voltage."
 
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The_Breeze

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Just to close this, here is their response:
"Thank you for reaching out to Battle Born.

This is a common question that we get asked, but I recommend fully charging the battery bank. Our batteries are top balancing batteries, so you need to reach a range between 14.2v and 14.6v to allow the BMS to enter passive cell balancing. Over time if you do not fully charge the battery bank, you can start to see decreased capacity.

I recommend taking a look at our Battle Born battery Youtube channel, and reading through the FAQs on our website to learn more about the BMS. The BMS has discharge limitations, and protective states for high and low voltage, high and low temp, as well as short circuit.


https://battlebornbatteries.com/faq/"
 

RVLiFe

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I purchased a SOK 206Ah Battery which has similar characteristics to the BB.
I opted for the WF-9855LiS charger in my RV. It will go into a 14.6v bulk/absorption charge for between 1 and 4 hours at 50 amps depending on the battery’s state of charge. This gives the batteries BMS time to equalize if needed and then it goes into a 13.6v float mode which basically will just sit there and do nothing because your battery is already charged above 13.6v. If additional charging is necessary (higher Ah battery) simply recycle the power to the charge controller and it will recycle its settings.
My recommendation is to install a battery shut off switch so that you don’t have to worry about your battery being overcharged unnecessarily if you so desire.
Purchase a Victron SmartShunt or some other battery monitor and just turn your battery off when it hits your desired charge level. It is recommended to fully charge (100% at 14.6v) either the SOK or BB once a month so that the BMS can balance the cells.
 

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AndrettiDog

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The only way you can realistically control the point the terminate charge below 100% is to use a battery monitor like the Victron BMV712 and set its programmable relay to cut charging at a set capacity.
The BMV712 can cut off charging? I thought it was only a monitor.
 

smoothJoey

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The BMV712 can cut off charging? I thought it was only a monitor.
At least some versions of the BMV have a relay.
Depending on your charge source, various levels of jiggery pokery can be employed to control the charger.
I've done pretty much the same thing with a Victron smart battery protect and normally open solid state relay.
 

Just John

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