Well I stuck my big toe into Lifep04

[grizzzman]

Hi all! I picked up 8 50 AH cells. (Sure took me a long time to go for it.) 2P4S 100 AH is how there set up. The spec sheet shows a "normal" charge at .5C and a "quick" charge at 1C. At 3.65 volts per cell, untell amps drop to .05C. Then terminate charging. I picked up a Renolgy 40 Amp DC to DC charger, As a back up charging source. ( A good thing too. At the grand canyon this summer, I had a ground issue on the charge controller.) The main source of charging is solar. Here is my question, If I charge at say 3.5 volts per cell do still terminate the charge at .05 Amps? Does the roller coaster type charging (clouds, low early low amps charging in the mornings affect the charge rate? Am I overthinking this?

Thanks

[BruceS]

If I charge at say 3.5 volts .............

Firstly I think you need to forget a lot that sounds like lead/acid battery technology.
One thing I learnt very quickly was that you can hook up a 12v charger to one single cell & the current flows so quickly into these cells that the resulting voltage of the cell will slowly increase as the cell is charged.
So ... basically you charge with almost any voltage until the voltage in the cell/battery gets to your desired cut off point & then kill the charger. Rest for a given time & hit it again .... over & over.
Have you read through T1's website? (Terry's)
www.t1lithium.com.au

[bagmaker]

I would only charge to 3.45 -3.5v maximum for long term use. The slight difference in voltage over 3.5 is buggar all difference in capacity but a lot of difference in safety. Grab yourself an active balancer, monitor each cell and you shouldnt have too many problems

[T1 Terry]

If you decide to use an active balancer, choose one the only kicks in at say 150mV between the highest and lowest cell and turns off at 50mV, 20mV at the most, otherwise the balancer will hide cells that have problems .... until it is too late to fix the minor problem because it has become a major problem.
As long as you stop charging when a cell hits 3.6v and doesn't restart until the cell is below 3.6v you won't have a problem with the cells that was caused by over charging or over heating of a cell. If you cut the load when any cell hits 2.8v that will protect the cells from over discharge.
You can't use battery voltage as the control point, once a cell goes over 3.4v and is saturation charged, that cell will rapidly climb to over 3.6v while the lowest cell goes even lower, yet the total 4 cells in series voltage remains the same. If you stop the charging at less than 3.4v x 4 cells = 13.6v, you probably won't suffer from a cell going high but you will end up progressive loosing cell capacity.
The reason why this happens is far too complex to explain on here, even face to face I see the eyes rolling back Let's just call it compound memory charge effect. I know those with a lot less hands on experience claim these lithium cells don't suffer from memory effect, but 9 yrs of testing shows they certainly do and if you introduce a regular under charge voltage to each cell the effect happens much faster.
Charging to a battery voltage and maintaining that voltage is the quickest way to put a lithium battery out of balance. The out of balance is only seen at 100% state of charge in any cell, and totally drained to below 3v in any cell. Anywhere between 99% SOC and drained (below 0% SOC) they will all look balanced so no point in looking at cell voltages or trying to balance cells at any other point in the charge/discharge cycle. House batteries are top balanced, at the 100% SOC point, electric vehicle batteries are bottom balanced, generally at 2.8v, so they all run out capacity at the same time so reverse current flow can't occur (not gunna try to explain that one either )

T1 Terry

[grizzzman]

Thanks, BruceS I have not looked at Terry's site in a long while. Lots of good info there. Thanks for the reply Bagmaker. I would like cells to last, but I also due to not many AH find a balance of life-Amp hours stored.

Terry, are you saying that when a cell hits 3.6 regardless of the amps of charging that it is saturated? My goal is 90 to 95% charge. I now have 3 "claimed" active balancer's I plan to test since camping is done for this year, One has an off-on switch. (The plan is not to use the balancer during camping.) (between trips, I plan on using the active balancer) Ya, I was aware of the capacity loss issue. (The cruiser forum) I am trying to avoid that issue. I figure I have 5 years (retirement) to figure this stuff out. This is a hobby for me, however, I plan on lots of camping and will upgrade to a larger bank at that time. Oh and way, Terry nice site. Looks like things are going great for you!

[BruceS]

Yep! Once at 3.6 they are 'saturated' as you call it. They don't need to trickle like lead acid. Once again try to forget much what you learned back in them days.
Imagine two tanks of water. One full and one empty. Lead acid is like a half inch pipe between them & a 5/8" hose filling the full one.
Compare that to a 24" pipe between them & a 12" hose filling the full one. (keeping it full)
Be careful taking a lot of notice of 'him' on the cruiser forum. (You know who I mean!)

[T1 Terry]

Thanks, BruceS I have not looked at Terry's site in a long while. Lots of good info there. Thanks for the reply Bagmaker. I would like cells to last, but I also due to not many AH find a balance of life-Amp hours stored.

Terry, are you saying that when a cell hits 3.6 regardless of the amps of charging that it is saturated? My goal is 90 to 95% charge. I now have 3 "claimed" active balancer's I plan to test since camping is done for this year, One has an off-on switch. (The plan is not to use the balancer during camping.) (between trips, I plan on using the active balancer) Ya, I was aware of the capacity loss issue. (The cruiser forum) I am trying to avoid that issue. I figure I have 5 years (retirement) to figure this stuff out. This is a hobby for me, however, I plan on lots of camping and will upgrade to a larger bank at that time. Oh and way, Terry nice site. Looks like things are going great for you!

I'll pass that on to Margaret, she wrote all the stuff on the site, I just had to go through editing pages of stuff printed off while trying to enjoy a few cold drinks on the front verandah at home. By about the 3rd cool drink all hope was lost because I didn't even understand what I'd written the night before
Margaret is in the process of doing a major rewrite of the site info to keep it fresh and even more informative. I have to try and reel her in every so often because she is getting as bad as me with the whole "over the top" explanation of stuff.
Her latest is trying to explain Peukert factor and how it works for lead acid batteries WHY????? doesn't seem to cut it and trying to explain that there is no one Peukert exponent you can add to the equation as it can't be reverse engineered. I've tried explaining the greater the load to capacity ratio, the greater the loss factor therefore the actual Ah capacity of the lead acid battery reduces and the 50% SOC end point is reached even faster .... see, I've even got your eyes rolling back in your head
Trying to get her to understand that theoretically an air conditioner can be powered via an inverter from lead acid batteries, but in reality the battery build and required capacity make it impractical for anything but an off grid house or a houseboat .... but $$ per AH stored is nearly twice the cost for lead acid compared to lithium to supply the same load requirement ..... all right, I'll stop now You can see why I send a few hundred people at a Stone The Crows talk into a coma eh

T1 Terry

T1 Terry

[Mrcoolabah1au]

When will the re write be ready to read does take a lot of time for it to sink in

[Grandad]

Her latest is trying to explain Peukert factor and how it works for lead acid batteries WHY????? doesn't seem to cut it and trying to explain that there is no one Peukert exponent you can add to the equation as it can't be reverse engineered. I've tried explaining the greater the load to capacity ratio, the greater the loss factor therefore the actual Ah capacity of the lead acid battery reduces and the 50% SOC end point is reached even faster .... see, I've even got your eyes rolling back in your head

With an over riding preface in place that sometimes my eyes do roll back into my head after you've explained something, your explanation of the Peukert effect certainly isn't one of them. You explained that to me years ago.

A 100AH battery may give you close 100 amps if you withdraw it at 1 amp only but try to withdraw 100 amps and you won't get anywhere near 1 hour of service time.

Do I have it right? If so, what's so hard to understand about that?

Jim

[T1 Terry]

Her latest is trying to explain Peukert factor and how it works for lead acid batteries WHY????? doesn't seem to cut it and trying to explain that there is no one Peukert exponent you can add to the equation as it can't be reverse engineered. I've tried explaining the greater the load to capacity ratio, the greater the loss factor therefore the actual Ah capacity of the lead acid battery reduces and the 50% SOC end point is reached even faster .... see, I've even got your eyes rolling back in your head

With an over riding preface in place that sometimes my eyes do roll back into my head after you've explained something, your explanation of the Peukert effect certainly isn't one of them. You explained that to me years ago.

A 100AH battery may give you close 100 amps if you withdraw it at 1 amp only but try to withdraw 100 amps and you won't get anywhere near 1 hour of service time.

Do I have it right? If so, what's so hard to understand about that?

Jim

Understanding how that 100Ah was determined seem to be a hurdle too high for many. The C rating starts the whole eye roll thing, but simplified, divide the advertised capacity, in this case 100Ah by the number after the C. Most honest lead acid battery resellers rate a deep cycle battery at the C20 rate or the capacity discharge at a continuous rate for 20 hrs, so in this case 100/20 = 5, so a continuous discharge rate of 5 amps for 20 hrs will see a new fully charge battery go from 12.8vdc down to 10.5vdc.
The less than honest ones use a C100 rate, or the capacity discharged over 100 hrs, or in our example 1 amp for 100 hrs. The same battery rated as 100Ah at the C100 rate would only rate at 80Ah at the C20 rate.
Good lithium batteries are rated at the C2 rate, or the capacity discharged over 2 hrs, in this case 50 amps for 2 hrs will bring a fully charged lithium battery from 13.8v down the 12v or 3v per cell.
The less than honest lithium drop in battery sellers could be using the C20 rate or even the C100 rate to measure their 100Ah capacity, but try getting any of them to tell you what the C rating was used to get that 100Ah capacity.
Because many can't get their head around the idea that the 100Ah is the same no matter what chemistry battery it is, a You Tube video test might help.
I have 4 x 100Ah Winston cell batteries on a discharge test with a halogen globe, the load is 3 amps. The test has run for 92 hrs so far with 276Ah drawn out so far, the cells are still showing 3.27vdc in each cell, still waiting to see if we get more than 133 hrs before the cells hit 3vdc per cell .... me thinks it might be quite a bit longer than that.

T1 Terry