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pianotuna

Regina, SK, Canada

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Posted: 11/17/19 10:43am Link  |  Quote  |  Print  |  Notify Moderator

Hi MDKMDK,

Charging to 100% on LI is not recommended. Best to stop at 90%. Going to 0% is not recommended. 20% may be a reasonable low.

MDKMDK wrote:

What about LiFePO4 banks? Can't assume everyone is using FLA or AGMs any more.



Regards, Don
My ride is a 28 foot Class C, 256 watts solar, 556 amp hours of AGM in two battery banks 12 volt batteries, 3000 watt Magnum hybrid inverter, Sola Basic Autoformer, Microair Easy Start.

Harvey51

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Posted: 11/17/19 12:43pm Link  |  Quote  |  Print  |  Notify Moderator

I’m sure the Trimetric is much more accurate and easy to calibrate and has more useful features.
I do think my cheapo Ebay one is far better than having no monitor that can count amp hours out and in. Voltmeters alone are not adequate.

I do understand that more energy must be put back than is taken out due to losses so I just leave the solar panel charging after the monitor says 100%. If using generator, shore power, or a lot of solar an automatic or manual shut off would be necessary. My first set of batteries lasted one year; the second pair are working well after 8 years.


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2oldman

Ca

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Posted: 11/17/19 05:10pm Link  |  Quote  |  Print  |  Notify Moderator

My BMV-700 Victron is working real well with my Li battery. And the monitor is on my smartphone. Pretty cool.

BFL13

Victoria, BC

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Posted: 11/17/19 05:29pm Link  |  Quote  |  Print  |  Notify Moderator

How do Li batts work for charging efficiency anyway? Wets go crazy for heat loss going past 80% SOC on up. AGMs heat up too.

If Li batts have better charging efficiency, then a straight AH counter when charging would be more accurate than with Wets. (The Trimetric has a built -in allowance for heat loss while charging, but it is not expected to fit all batts. You can adjust that if you do enough trial and error work on that for your own set of batts)

Not sure what it means that Li has that slow rise in voltage. I doubt it means poor charging efficiency. ?


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dieseltruckdriver

Black Hills of SD

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Posted: 11/17/19 05:52pm Link  |  Quote  |  Print  |  Notify Moderator

Harvey51 wrote:

I don’t find it complicated or in need of micromanagement. I charged it fully, set the amp hour capacity and 100% charge on the monitor when I first installed it. The solar charge controller keeps on charging slowly after the monitor reads 100% but the monitor doesn’t go beyond 100%. It has recalibrated itself so 100% means charging has replaced all the amp hours used since it was last fully charged. No adjusting ever. No doubt it is getting less accurate as the battery capacity diminishes but I always know when I’ve got a full charge.
[image]
The battery monitor is perfectly easy to use and the only convenient means of knowing how charged the batteries are. The voltage method, including idiot lights, is overly optimistic because it reads the charging voltage for hours after charging has ceased and you think all is well until your batteries die. For me, on our first long trip, it was no heat on a cold morning. Fortunately we were near a town on Vancouver Island that had a Costco store where I could get new batteries. Those batteries I bought in 2011 now seem to be as good as new so I figure the $25 battery monitor is doing its job.


That is the battery monitor I had in my first 5th wheel, or one very nearly like it. It told me all I needed to know, and I don't watch the batteries nearly as close as I used to, so a lot of the features of the Victron go unwatched by me. My DW likes to watch the progress too.
I don't know why, as much as I like tech stuff, I have no desire to use the bluetooth on the Victron.


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MrWizard

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Posted: 11/18/19 12:29am Link  |  Quote  |  Print  |  Notify Moderator

I have the wireless meter ( two parts transmitter and display-controller , display uses 5volt USB, monitor transmitter mounts at battery uses 12v ) that shows capacity percent, capacity amphrs , voltage .amps plus or minus, charging or discharging AkA load amps, the meter stops adding amphrs once it gets back the counted discharge, BUT it keeps on displaying the charging amps going in, when It gets down to less than 1 amp charge rate I know it's full, even if that takes 2-more hours of charging after the amp hood counter stopped
That is the true measure of fully charged when using sealed agm batteries
So IF I stop the charging when it is at 4 amps charge rate, I know I'm not full, even though the capacity number says I am !
A full days charging to the amps drop off point sets everything at the correct start point,
I can reset/change the battery capacity if/when the capacity changes with age and use

* This post was edited 11/18/19 01:06pm by MrWizard *


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Itinerant1

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Posted: 11/18/19 06:08am Link  |  Quote  |  Print  |  Notify Moderator

BFL13 wrote:

How do Li batts work for charging efficiency anyway? Wets go crazy for heat loss going past 80% SOC on up. AGMs heat up too.


LFP are near 100% efficient, take a 100ah out your putting a 100ah back. No long drawn out charging.

As I mentioned in earlier post, I could almost put a stop watch on the amount of time needed to charge just by looking at the monitor and knowing my SOC.

BFL13

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Posted: 11/18/19 06:36am Link  |  Quote  |  Print  |  Notify Moderator

Itinerant1 wrote:

BFL13 wrote:

How do Li batts work for charging efficiency anyway? Wets go crazy for heat loss going past 80% SOC on up. AGMs heat up too.


LFP are near 100% efficient, take a 100ah out your putting a 100ah back. No long drawn out charging.

As I mentioned in earlier post, I could almost put a stop watch on the amount of time needed to charge just by looking at the monitor and knowing my SOC.


So with a Trimetric monitor and Li batts you would have to change the default Charging Efficiency setting so it would allow nearly all the amps from the charger to count as going to battery.

I haven't read the newer Bogart instructions since Li came out. They probably mention that.

On going over 100%, I do not have my Trimetric set up to show percentage SOC. I just have it doing straight voltage, amps, and AH. I have disabled auto-reset of AH, as required with solar.

So I can see in late afternoon on a good solar day that the AH count has gone "positive" past zero, and is going up. I have noted with Wets that SG only gets back to "baseline" indicating the batts are full when AH have risen to about +15 in my case.

If you were in a stable scenario and could see that happening every day, there is a Trimetric adjustment for Charging Efficiency so you are closer to zero on the AH count when the SG gets to baseline. You have to do a bit of trial and error till it is about right. (RVing is not generally a stable scenario for solar, so can't really do that)

EDIT--that's when I reset the AH count to zero too. As soon as the solar charging is over for the day, and the SG says the batts are at true full, now you change the AH count from +15 to zero. If you never got to full that day due to clouds or high draws, you do not reset the counter. Just let it go up and down until the next chance when the batts do get to true full.

So you can call that "micro-managing", but if you don't then your monitor will be telling you lies. Your choice. As long as you don't believe anything it says. Probably better to not have a monitor in that case.

* This post was edited 11/18/19 06:55am by BFL13 *

allen8106

Burrton. KS

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Posted: 11/18/19 12:51pm Link  |  Quote  |  Print  |  Notify Moderator

I recommend the Trimetric TM-2030-RV from Bogart Engineering. I have this one installed on my solar system and it works flawlessly.


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Itinerant1

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Posted: 11/27/19 04:00pm Link  |  Quote  |  Print  |  Notify Moderator

BFL13 wrote:

How do Li batts work for charging efficiency anyway? Wets go crazy for heat loss going past 80% SOC on up. AGMs heat up too.

If Li batts have better charging efficiency, then a straight AH counter when charging would be more accurate than with Wets. (The Trimetric has a built -in allowance for heat loss while charging, but it is not expected to fit all batts. You can adjust that if you do enough trial and error work on that for your own set of batts)

Not sure what it means that Li has that slow rise in voltage. I doubt it means poor charging efficiency. ?


Here is a follow up charging the lfp batteries with some #s. Using a eu2200i generator, using a Magnum inverter/ charger (max 125a charging) I set my AC input to 15a on the remote display.

Totally overcast today no charging from solar. Started at noon at 53% SOC (prior readings 13.13v), didn't really plan to do any recording and didn't get a starting voltage.

12:00 53%
12:24 Bulk 59% 13.60v(reading from monitor) 105.8a(charging) 57f(cell temps)
13:39 Bulk 86% 13.76v 102.5a 62f
14:01 Bulk 94% 13.90v 100.4a 64f
14:03 Absorb 95% 14.09v 80.4a 66f
14:08 Float 99% 13.76v 0.1a 71f

Generator turned off, reading after, cell temps drop.
14:20 Float 99% 13.60v -12.0a 64f

In 2 hours 8 minutes went from 53% (265ah) to 99% (495ah), total 230ah.

I would consider that pretty efficient. [emoticon]

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