Lithium battery discharge/charge cycle

[dg0603]

Hi all, thanks in advance.

Tellaro with the Reliable 200Ah system.

Is it better to let the batteries work their way down if possible, and then to charge them back up to capacity? Or does it matter that they are brought back up to full constantly after just a partial discharge?

I guess it's a question of these battery types developing a memory type thing.

Thanks!

[lwmcguir]

Most all batteries list a value for recharges or cycles. Tesla used to have some of their batteries listed for 1700

Whether it is a phone or tool or RV they all have a number of cycles before losing recharge or usable storage capacity.

There is a Battery expert on here so going to be interesting to hear his input.

[dg0603]

Yes, exactly. I was wondering if the partial discharge/recharge issue impacted the overall number in that rating. Does a 1/3 discharge and recharge count toward that....just like an 85% discharge/recharge?

[Scubawise]

We leave ours plugged into 30 amp or let solar keep charged or AGS kicks in..all from my 30 year tech kurt

[16ACE27]

Originally Posted by Scubawise

We leave ours plugged into 30 amp or let solar keep charged or AGS kicks in..all from my 30 year tech kurt

But you don't have lithium batteries so how is this pertinent to the OP's question?

[Beau388]

Originally Posted by dg0603

Hi all, thanks in advance.

Tellaro with the Reliable 200Ah system.

Is it better to let the batteries work their way down if possible, and then to charge them back up to capacity? Or does it matter that they are brought back up to full constantly after just a partial discharge?

I guess it's a question of these battery types developing a memory type thing.

Thanks!

While the chemistry is nearly the same for all LiFePo batteries, the battery manager is somewhat different. The answer to the questions you pose are best answered by the battery manufacturer. For instance, some manufactures recommend the lithium batteries not be stored at charge levels above 80% or discharged below 20%, but not all do. To answer your question directly LiFePo batteries do not have a memory.

The reason be so vague is that all lithium batteries have a battery manager that charges and discharges each cell as an individual battery and combines the cells to supply the current required. Remember each lithium cell is about the size of a D size alkaline dry cell battery and controlled separately or in similar groups by the battery manager. This design and operation is total different than any common lead acid battery. For instance, if one lithium battery cell goes bad, the battery manager will remove only that cell from the array. You would not normally notice that happening unless you interrogate the battery manager

[Chance]

Originally Posted by dg0603

Hi all, thanks in advance.

Tellaro with the Reliable 200Ah system.

Is it better to let the batteries work their way down if possible, and then to charge them back up to capacity? Or does it matter that they are brought back up to full constantly after just a partial discharge?

I guess it's a question of these battery types developing a memory type thing.

Thanks!

That shouldn’t be an issue to worry about. They don’t develop a low-charge memory like old nickel metal hydride batteries. That’s probably what you were referring to.

The issue that we hear about now with lithium batteries is that topping them off all the time can reduce their life a little, but even that depends on chemistry. As far as I know Tesla recommends not charging to 100% every day unless you will be taking a long trip and need added driving range. However, most Tesla use a different battery chemistry that is more sensitive to this.

RV lithium batteries are mostly lithium iron phosphate which tolerate charging to 100% better than typical Tesla battery. I should note for clarity that due to supply chain issues, Tesla is offering lithium iron phosphate batteries to buyers which loses just a little normal driving range (they don’t store quite as much energy).

To other question, when RV LiFePO4 batteries are not discharge as much, you gain additional life cycles. It is not as much percentage wise as with lead batteries though (flooded or AGM). In other words don’t discharge them down unnecessarily thinking you will help them last longer.

Just enjoy them. Chances are than 1,000s of cycles will outlast motorhome.

[Chance]

This article mentions not having to worry about charging to 100% with LiFePO4 but you do with normal Tesla chemistry. It’s been reported by many sources.

https://www.cnbc.com/2021/10/20/tesl...ange-cars.html

or

https://www.cnet.com/roadshow/news/t...tandard-range/

[dg0603]

Thank you guys, that was fascinating and very useful.

[Lamokadave]

Not to hijack this thread, but on a similar topic, when multiple 12v lithiums are ganged in series should one expect that the power draw from the batteries is equal or is it normal that in use they can discharge at a different rate.
I'm using 3 100ah Renogy lithiums with a bluetooth function and as I use the batteries I notice that the amp draw from each battery can be different. This is true when they recharge as well.
Over several days use, this can amount to a 10-15% difference in remaining capacity from one battery to the next.
This last trip I found the battery with the positive leads connected showed an over 10% reduction in remaining ah as compared to the center and negative lead connected batteries.
I assumed that the batteries would self equalize but that doesn't seem to be the case.
I'm thinking the solution to this would be to have the batteries all feed a busbar and draws be taken from that point as well

[Trophy1200]

Series or parallel?

[16ACE27]

Originally Posted by Lamokadave

Not to hijack this thread, but on a similar topic, when multiple 12v lithiums are ganged in series should one expect that the power draw from the batteries is equal or is it normal that in use they can discharge at a different rate.
I'm using 3 100ah Renogy lithiums with a bluetooth function and as I use the batteries I notice that the amp draw from each battery can be different. This is true when they recharge as well.
Over several days use, this can amount to a 10-15% difference in remaining capacity from one battery to the next.
This last trip I found the battery with the positive leads connected showed an over 10% reduction in remaining ah as compared to the center and negative lead connected batteries.
I assumed that the batteries would self equalize but that doesn't seem to be the case.
I'm thinking the solution to this would be to have the batteries all feed a busbar and draws be taken from that point as well

Do you want to rephrase your question? When batteries are in series thay all have the same current flowing through them but can have different voltages.

When batteries are in parallel they all have the same voltage but can have different currents to/from each.

Theoretically, in parallel batteries will "equalize" state of charge due to voltage status differences but this is less true for lithium batteries due to their flat voltage vs state of charge profile. Plus, if the parallel batteries are not in the same "age condition" (true storage capacity) they will unequalize as soon as they are loaded with the better batteries suppling a majority of the load current. This is why, with any type of battery used in parallel service, it is recommended to replace them all at the same time.

I recommend you disconnect your batteries and fully charge them individually before reconnecting.

[Chance]

Originally Posted by Lamokadave

.....cut....

I'm using 3 100ah Renogy lithiums with a bluetooth function and as I use the batteries I notice that the amp draw from each battery can be different. This is true when they recharge as well.
Over several days use, this can amount to a 10-15% difference in remaining capacity from one battery to the next.


......cut.....

I personally think people assume data they receive from electronics is way more accurate than it may be. I would always question that first and rule it out before proceeding to look for other issues.

I assume you have three batteries in parallel and not in series to make 36 Volts.

[Lamokadave]

I definitely misspoke or typed. They are wired in parallel for 300ah at 12v.
They are all the same age and only several months old. They were all charged individually to 100% using a NOCO lithium 10A charger prior to installation but with use seem to discharge at different rates. The same goes for recharging off the lithium charger I installed in the powercenter. The differences in discharge and recharge rate are typically less than 1A but over time the accumulated difference becomes somewhat significant. I know the difference is real as I recently separated the batteries to bring the deficient one back to full charge as my powercenter charger would not do it and the one battery was reading high 80% SOC while the other 2 were over 99%. The portable charger did bring it up to match the other 2 batteries.
With very slight current draw ie <3a, I'll see all current come from a single or 2 batteries while 0 from the remaining.
Maybe that is a resolution issue of whatever the BT is getting data from, but I believe the accumulated differences are real. It just seems odd as I assumed being wired together they would act as a single battery.
Is my idea of connecting all through a bus vs linking in parallel a likely solution?

[HarryS]

I think that's more a question for your battery maker. They will be able to tell you exactly what is going on.