My Lithium Upgrade

[rowiebowie]

Originally Posted by markopolo

It appears that the Renogy 100Ah LFP battery is the same as this EWT battery: IFR26650 12.8V 100Ah

EWT 50Ah LFP battery teardown:

I'm more than a bit curious about only seeing 3 red wires. I expected to see 4 in a 4S15P battery. There could be a few explanations for this. You can clearly see one group of 15 paralleled cells. 60 cells in the 50Ah battery.

Crazy to see youtube channels willing to destroy batteries to get to the see the inside (like this guy and Will Prowse). But glad someone is doing it.

I'm just not sure I'd want to see what they say about my 100ah Renogy's. But for all I know it could be made the very same as the blue one in the video. A Battleborn was opened by Will Prowse, and he was impressed.

https://www.youtube.com/watch?v=G5E30u-66VI

[markopolo]

Thanks for posting the info. I know that voltage isn't a great way to try to figure out SOC with LFP batteries but it would show us if there was a wide disparity between the SOC meter and the voltage reading.


Here's chart from a manufacturer that uses IFR26650 cells like Renogy.


IFR26650 cells.JPG


13.3V looks to be around 75% - no wide disparity between the SOC meter and the voltage reading here

[markopolo]

We have to remember that Rowie's Renogy battery is rated for 2000 cycles at 100% DOD.

It's awesome that people will buy items like this and take them apart so the rest of us can see what's inside.

The purpose of the 3 red wires in the shown in the video is obvious to me now. It's simply 3 conductors paralleled to support the required current.

With many cells in parallel, one challenge is trying to make sure every cell at least gets to see the same voltage when charging.

This person - https://svhajime.wordpress.com/2016/...e-little-pigs/ - thinks that this is the BMS in the EWT 100Ah battery: QUAWIN ELECTRONICS CO., LTD - charger, battery charger, high power charger,battery,battery pack, li-ion battery,lithium battery, Li-Polymer battery,LiFePO4 battery,PCM,PCBA,BMS,18650 battery,E-bike battery,NIMH-NICD battery charger,NIMH-NICD

(the 50A battery in the Youtube video is the "Smart" version so it would have a different BMS)

of particular interest is:

Balance voltage for single cell: 3.65V±0.025V

"Cell" might also mean "string" but the important thing appears to be that balancing occurs at 14.6V. That explains Renogy's very specific charging instructions to take the batteries up to 14.6V and hold them there until the current drops to 2% of the batteries capacity. You not only need to get to 14.6V but also need to hold it there to allow enough time for balancing to complete.

I would make sure that happens at least every three months if one is uncomfortable doing it every charge cycle.

[markopolo]

Because you can't set the charge termination current on the Renogy Inverter/charger, I wonder if setting it to 14.7v would suffice? (if the default LFP setting doesn't seem to get to 14.7V as noted by Rowie)

[booster]

Originally Posted by markopolo

We have to remember that Rowie's Renogy battery is rated for 2000 cycles at 100% DOD.

It's awesome that people will buy items like this and take them apart so the rest of us can see what's inside.

The purpose of the 3 red wires in the shown in the video is obvious to me now. It's simply 3 conductors paralleled to support the required current.

With many cells in parallel, one challenge is trying to make sure every cell at least gets to see the same voltage when charging.

This person - https://svhajime.wordpress.com/2016/...e-little-pigs/ - thinks that this is the BMS in the EWT 100Ah battery: QUAWIN ELECTRONICS CO., LTD - charger, battery charger, high power charger,battery,battery pack, li-ion battery,lithium battery, Li-Polymer battery,LiFePO4 battery,PCM,PCBA,BMS,18650 battery,E-bike battery,NIMH-NICD battery charger,NIMH-NICD

(the 50A battery in the Youtube video is the "Smart" version so it would have a different BMS)

of particular interest is:

"Cell" might also mean "string" but the important thing appears to be that balancing occurs at 14.6V. That explains Renogy's very specific charging instructions to take the batteries up to 14.6V and hold them there until the current drops to 2% of the batteries capacity. You not only need to get to 14.6V but also need to hold it there to allow enough time for balancing to complete.

I would make sure that happens at least every three months if one is uncomfortable doing it every charge cycle.

Very interesting stuff, for sure.


The Renogy rating at 100% DOD is certainly of question in relation to the video and it sure would nice to know what they would say. It is possible they are using an actual battery with more capacity than rated and putting limits on it, but the voltages wouldn't seem to suggest that is not the case. I would guess we are going to see more and more "cushion" space at the top and bottom of SOC as time goes on and all this shakes out better. So much of the available information is for other chemistries that it hare do know what will also apply to the LiFePo4 batteries.


The vehicle aftermarket part "reviewers" have been doing the take it apart to compare things inside routine for a long time and over the years quite a few have been exposed of having been hired to come to the desired results. I think there is a very good chance the batteries in these videos were probably not purchased, but provided by a vendor. There are so many people doing this kind of stuff now that we are getting more and more slanted reviews than ever, on everything. Or maybe I am just skeptical


Good information on the 14.6v needed to balance the cells. I remember there was a lot of discussion of whether to "top balance" or "bottom balance" the cells quite some time ago during a couple of the home build threads. Of course, that time was before the upper and lower cushions were added so that didn't get into the picture then IIRC. I think that at that time a lot of recommendations said balancing was only needed initially, also.



I wonder if the 14.6v is really necessary or just chosen because that was the charge max so easy to hold that level for the time needed? If the don't go to full regularly issues are as bad as some say, it would be nice not to go there regularly. It seems like a better choice, if it would actually balance the cells right, would be to have the rebalance happen at whatever the max SOC you have chosen to have some headroom. Holding the voltage there until at a certain current would possibly be better for the batteries as long as it worked to balance correctly. We know that AGM batteries will continue to charge and use less current for the first day or two they are on float, so perhaps similar happens with lithium at less than the 14.6v level.

[markopolo]

To me, it appears to mean that 3.65V per parallel cell group is required. That is 14.6V for 4 cells in series.

balance at 14_6V.JPG

The 12.8V+ leads look to come directly off one 15P group. The series connections are happening somewhere else in the box. My assumption is that the layering is like this:

12.8V-negative leads_-15P cells+_-15P cells+_-15P cells+_-15P cells+_+12.8V positive leads (shown in video).


4S15P.JPG

[markopolo]

Just to add that if you don't balance the groups of series connected cells you could end up with: 3.7V+ 3.8V + 3.3V + 3.7V = 14.5V compared to 3.65V + 3.65V + 3.65V + 3.65V = 14.6V for example.

It looks like cell group over voltage protection kicks in at 3.9V.

Edit: deleted a bit, looking for sources

[rowiebowie]

See my post on Renogy's Black Friday Sale here: http://www.classbforum.com/forums/f5...tml#post102055

Their sale is site-wide until 12/1/19.

[Bud]

Originally Posted by rowiebowie

Crazy to see youtube channels willing to destroy batteries to get to the see the inside (like this guy and Will Prowse). But glad someone is doing it.

I'm just not sure I'd want to see what they say about my 100ah Renogy's. But for all I know it could be made the very same as the blue one in the video. A Battleborn was opened by Will Prowse, and he was impressed.

A bell just kind of went off in my head rowiebowie. Then it took me a moment or two to put it together - Will Prowse. On a different forum totally unrelated to rv, batteries or ....... It was found out that this guy was a fraud, simply making a buck from publishing Amazon books to..........

Has he found a new venue?

[booster]

Originally Posted by Bud

A bell just kind of went off in my head rowiebowie. Then it took me a moment or two to put it together - Will Prowse. On a different forum totally unrelated to rv, batteries or ....... It was found out that this guy was a fraud, simply making a buck from publishing Amazon books to..........

Has he found a new venue?

Interesting. Couldn't find anything about fraud or such, but most of the books on Amazon are about medical things like pain and supplements, so he is probably just going to whatever topic can make him the most cash, but now on Utube.

[rowiebowie]

Originally Posted by Bud

A bell just kind of went off in my head rowiebowie. Then it took me a moment or two to put it together - Will Prowse. On a different forum totally unrelated to rv, batteries or ....... It was found out that this guy was a fraud, simply making a buck from publishing Amazon books to..........

Has he found a new venue?

Originally Posted by booster

Interesting. Couldn't find anything about fraud or such, but most of the books on Amazon are about medical things like pain and supplements, so he is probably just going to whatever topic can make him the most cash, but now on Utube.

I found the book on chronic pain relief on Amazon that booster found. But I also didn't find any fraud mentioned on the search results I got. That being said, I'm not buying anything from the guy. I just enjoy watching him (and others) gut electronics on youtube to see what's inside. Something I cannot afford to do. And he admits he gets the stuff free.

But it's always good to cast a wary eye on all things on the interwebs.

[rowiebowie]

Two months after returning from our first trip using the new Renogy 200Ah lithium/3000W Inverter-Charger/40A DC to DC Charger, I finally took the time to observe the charging parameters of my system.

As I previously stated, during our trip I never saw charging by 120v plug-in of over 13.5v; which is well below the stated 14.4v (+/- .2v) recommended charging parameters in the Renogy literature and charger specs.

If yesterday's observation is typical, I now know the reason I never saw charging above 13.5 volts is because peak voltage happens so fast. Holy cow! You could almost blink and miss it.

It seems the voltage stays in the 13.5v range most of the charging cycle, then only in last phase rises to over 14 volts. Then things really happen quickly with voltage rapidly peaking to 14.6v (over the course of the last 3 minutes of charge) then just as quickly, charging cuts off. Within another few minutes, the battery voltage settles at 13.5v, then 13.3v by this morning.

My biggest question is this. Is less than 3 minutes above 14.0 volts enough to ensure cell-balancing and proper charging?

I have highlighted the furious 10 minute time period (which includes the 3 minutes above) between 8:02pm and 8:12pm in red on the attached chart. After considering comments offered on this forum, I will call Renogy to inform them of my results.

[markopolo]

Thanks for sharing that info.
Some thoughts:
- I would expect to see some tapering of amps in before the end.
- The math doesn't seem to work. Wouldn't approx 2.5 hrs at 50A+ = at least 125Ah in?
- 13.2V at the beginning was probably 50% or so SOC.
- The 13.3V next morning seems ok, maybe a bit low if trying for 100% the night before. 13.3V might be 80% SOC.

[booster]

I agree with Marko that if it had reached the "knee" of the charging there would be current dropping with voltage rising.


This could mean that it was not the battery getting full that caused the voltage to go up, but that the charger itself turned it up. Normally, you would expect the charger to be set at the higher voltage but run lower voltage due to the 50 amp current limit in the the charger so only when the battery got full would the voltage get to the higher voltage, but then you would see the current tapering.


Looking at the data, it does appear that the voltage rising happened at very close to 90 minutes so it may be just on a timer set at 90 minutes. Certainly could be a coincidence, also.



I think the test would be to run the same test at higher and lower SOC starting points from this test, and see if and where the voltage changes.


I think it is very hard to guess what the effect would be on how full or not the battery got or if it is enough to balance, as we have seen so much conflicting information on those topics lately, including lots of stuff saying either or both could be hard on the battery.

[@Michael]

Originally Posted by markopolo

- The 13.3V next morning seems ok, maybe a bit low if trying for 100% the night before. 13.3V might be 80% SOC.
[/IMG]

The discharge curves that I've seen show a quick drop to approx 13.3v then a gradual, near linear taper down to 12.5 or so. See the 10A discharge curve here:

https://battlebornbatteries.com/comp...teries-series/

I don't think that one can necessarily associate 13.3v with 80% SOC.

Originally Posted by rowiebowie

My biggest question is this. Is less than 3 minutes above 14.0 volts enough to ensure cell-balancing and proper charging?

Renogy would be the best source for this.

Assuming passive top balance, my thinking is that if the cells are already balanced, then the time needed to balance would be minimal and the battery voltage would rise from 14.0 to 14.6 very quickly.

BTW - the recent YouTube video where Will interviews the president of Battleborn is informative. Seems like much of the conventional wisdom related to LiFePo4's isn't as is often presented on the Internet.

[booster]

Originally Posted by @Michael

The discharge curves that I've seen show a quick drop to approx 13.3v then a gradual, near linear taper down to 12.5 or so. See the 10A discharge curve here:

https://battlebornbatteries.com/comp...teries-series/

I don't think that one can necessarily associate 13.3v with 80% SOC.



Renogy would be the best source for this.

Assuming passive top balance, my thinking is that if the cells are already balanced, then the time needed to balance would be minimal and the battery voltage would rise from 14.0 to 14.6 very quickly.

BTW - the recent YouTube video where Will interviews the president of Battleborn is informative. Seems like much of the conventional wisdom related to LiFePo4's isn't as is often presented on the Internet.

In general, you can not really determine SOC on most any battery while it is being discharged as there is always a voltage drop somewhere along the way and that is based on the amp discharge rate. Note the different voltages those discharge curves show at the different discharge rates for the same SOC.


SOC needs to be checked on a battery that is not charging or discharging, and needs to sit long enough for the residual voltage change caused by either charging or discharging dissipates and is stable. That point is the the SOC profile in Marko's posted chart and where he got the 13.3v being about 80% SOC.

[tgregg]

Originally Posted by rowiebowie

Two months after returning from our first trip using the new Renogy 200Ah lithium/3000W Inverter-Charger/40A DC to DC Charger, I finally took the time to observe the charging parameters of my system.

As I previously stated, during our trip I never saw charging by 120v plug-in of over 13.5v; which is well below the stated 14.4v (+/- .2v) recommended charging parameters in the Renogy literature and charger specs.

If yesterday's observation is typical, I now know the reason I never saw charging above 13.5 volts is because peak voltage happens so fast. Holy cow! You could almost blink and miss it.

It seems the voltage stays in the 13.5v range most of the charging cycle, then only in last phase rises to over 14 volts. Then things really happen quickly with voltage rapidly peaking to 14.6v (over the course of the last 3 minutes of charge) then just as quickly, charging cuts off. Within another few minutes, the battery voltage settles at 13.5v, then 13.3v by this morning.

My biggest question is this. Is less than 3 minutes above 14.0 volts enough to ensure cell-balancing and proper charging?

I have highlighted the furious 10 minute time period (which includes the 3 minutes above) between 8:02pm and 8:12pm in red on the attached chart. After considering comments offered on this forum, I will call Renogy to inform them of my results.

How did you set the initial SOC on the Renogy battery monitor?

The instructions in the manual that I read online said to 'discharge the battery to 0 % and hold the 'down arrow' for 3s or charge the battery fully and hold the 'up arrow' for 3s.

Just curious.

[rowiebowie]

As Marco mentioned, the beginning SOC did not look accurate to me either (too high given the voltage). Probably confirmed by the charging time required.

During the 60 days the batteries have been sitting since our last trip, the SOC percentage had barely dropped (85 to 82%). This is with a small parasitic draw of .14 amps (1-2 watts).

In full disclosure, I may have screwed things up using my measly 20W solar panel to charge the batteries from 83% to 93% a couple of weeks ago. I was just experimenting, but the paltry 3-4 watt average net daylight charging for about 10 days was increasing the SOC about 1% per day. This seemed too much given the longer 1-2 watt overnight draw that should have offset the gains during sunlight hours. However, voltage before solar charging was 13.3v & 83% SOC before solar charging and 13.4v & 93% after 10 days of solar charging, so go figure.

Prior to beginning the charge, the SOC monitor still showed 93%, but only 13.1 volts which seemed a couple of tenths of a volt too low given the SOC has not changed.

I used a portable heater set at middle temp setting and let it run about 30 mins to get the SOC to show 69% just prior to starting the charge cycle. The heater drew about 77amps and voltage dropped to the upper 12v range during the discharge reaching a low of 12.5v when I disconnected at 69% SOC reading.

[rowiebowie]

Originally Posted by tgregg

How did you set the initial SOC on the Renogy battery monitor?

The instructions in the manual that I read online said to 'discharge the battery to 0 % and hold the 'down arrow' for 3s or charge the battery fully and hold the 'up arrow' for 3s.

Just curious.

The instructions you quote are correct. I was afraid to over-discharge the batteries and lock the BMS. So I just set the SOC monitor for 100% initially and did a full charge.

Once during our first trip I accidentally reset the monitor to 100%, but figured in both cases a full charge would sync batteries and monitor back up.

[markopolo]

Can you force the charger to have another go at it? Hopefully you'll see current tapering. After that you could set the monitor to 100%. It probably won't be actual 100% but much closer than what it shows now.


Renogy should be able to tell you what voltage balancing kicks in.