Battle Born Charging

Good info on the Trimetric. 2% for heat loss compares with BB claim of 99% efficient battery, but Tri explains the diff between charging efficiency and battery efficiency, if that applies here.

2% amps for full is different from 4-5% Li links say is full

It looks like Mobilesport's monitor has no setting for heat loss while recharging so it will overstate the AH going to "full"
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That 10 minutes from 2:00 -2:10 is worth 9AH at 53 amps, so now all the distortion was in the first hour and total overage was 25AH (53-28)

Of that 28% SOC, by 40 min it was up to 10% then it did 18 more in the next 20 minutes. After that, the rise in SOC over time matches the rise in AH at 53 amps. The voltage does not match, being fairly flat until near the end, which is correct.

If the monitor was just late getting started counting AH and %SOC that would explain it, but it was counting %SOC from the start.

The heat loss (in amps) from the bad connection did not get to the battery, but the monitor did not see that via its shunt or else the amps shown would not be constant 53 in the first hour.

The heat loss might show in the battery voltage not rising as fast as normal in the first hour, don't know what is normal.

It is a mystery why the monitor's %SOC rose to 28% while at the same time its AH counter must have been near 53AH

I have to edit some previous posts where I missed that 10 minutes time out.

BFL13 wrote:
"If using IC I'll set incoming ac from generator so 100a will charge steady almost all the way to 100%, once it gets to 96-98% it will start dropin some current but not a lot"

It would be the same constant amps with a 100a PowerMax or any other converter or charger that does constant max rated amps. What you didn't report there is what charging rate that 100 amp is. To do that you need the capacity of your battery bank in AH.

With the charging rate you can then compare when Bulk ends in SOC with where it ought to, like that 1C gets you to 65% (or 60 in the other link)

What confuses me is the notion that you can pick your capacity by choosing your absorption voltage. A lower Vabs gives you a lower capacity they say. That seems bizarre to me. To me the capacity is what it is and is not adjustable by changing your settings.

You can get higher amp acceptance rates by increasing Vabs, but that will then make your Bulk end at a lower SOC by increasing the charging rate.

With Li they like a lower Vabs to reduce stress, but that is not the issue here.

If you are getting to 99% SOC at constant 100a, then to me that says you are using a low charging rate. The battery bank must be big in AH as its capacity

I have similar setup MSH & PT, however I have De-Linked my PT & MSH for charging.

MSH CC/CV set for Amps stop at 40 Amps.
PT Custom Set for 14.4 VDc Absorption, and 13.1 Float. Absorption is set for time and 12 Hrs.

My reason is simple on Shore Power or Generator - MSH Comes on and off based on the Lithium Battery needs.

PT, I want it working and Producing Power all day long to power the Coach. The Lithium Batteries will stop accepting a charge when full, however if they are Linked, the PT will STOP producing power until the LB need to be re-charged.


I have tested various setting since my First installation. I have continued testing in various condition Dry-Camping and Non Dry Camping.

BFL13 wrote:
How can you use a Trimetric monitor with a BB?

You can set the 100AH as your capacity, and set the charging efficiency for Li, you can make 14.4 your target voltage, and 4 amps your target amps for "full".

But the Trimetric uses the AH counter wrt the AH capacity entry for saying what the % SOC is. It does not use rising cell voltage.

Mobilesport was reading %SOC from his monitor based on the BB voltage vs % SOC specs, but his AH count was way off. A Trimetric would not do that. How did Mobilesport's monitor manage to?

Here's what Bogart Engineering told me last summer:


Hello Steve,

We have a link below to the TM-2025's User Manual. In it you'll find, on pages 6 & 7, a description of all the 'P' parameters.

For Lithium LFP batteries, the changes needed are as follows:

P1 - 14.4 Volts.
P2 - 2% of P3 (battery bank capacity)
P3 - Battery Bank capacity in Amp-hrs
P7 - L3
P10 - 98%
P14 - 0.00 hrs

- Kedar

http://www.bogartengineering.com/wp-content/uploads/docs/TM-2025%20Users%20Instructions062017.pdf

Mobilesport wrote:

Itinerant1 wrote:

Mobilesport wrote:
One thing I noticed when I was running my battery down trying to reach the BB low voltage disconnect,, I was paying attention to my capacity monitor the whole time and when it got down to 12% soc I was actually looking at the monitor and all the sudden it dropped like a rock from 12% soc to 0% soc instantly.

At that point I started thinking that I must be close to the battery shutting down.

Nope , it took another hour and a half until the battery shut down , volts were 9.3 volts when the battery shutdown.

I'm not saying my monitor is correct just what I witnessed.

That there is the knee. They'll give their all till....lights out.

Yeah but it went lights out a hour and a half after my Soc meter read 0% soc?
I was thinking that my soc % monitor should read 0% at least close to the time the lights go out.
Shouldn't the battery have been at 0ah when the lights went out?

That's because your meter isn't properly synced to the batteries and most likely why BLF13 is going bananas with ah out/ ah in being so far out of wack.

Maybe it's a cheap meter, that shunt looked cheap in the video, maybe Chinglish count is different and programmed it wrong? ;)


Try reprogramming it or think about a different meter, many folks seem to like the Victron stuff.

Either way BB bms will protect the battery if the voltage gets to low or high.

Cell voltage to SoC while charging/ discharging is not accurate. The batteries has to rest for a few hours with no loads to get an accurate reading.

Coulomb counting is recommended, LFP voltage is to linear.

Your furnace by-passes the shunt so no effect on monitor's amps reading or its AH count. The converter runs the loads so no furnace load on the battery reducing its voltage.

Yes, Eco has no effect on the gen's 120v level so no effect on converter output.

If the furnace was eating some of the converter's amps and cycling, it would have shown by the 53 amps changing, but that stayed constant. So if it was on it was on the whole time at the same amps.

I just noticed that you must have stopped for 10 minutes at 2:00 and restarted at 2:10,(fixing the hot spot) so that might explain why the first half of that hour from 2-3 was lower.

Not much voltage rise over time in that second hour while SOC went up.
Was a graph of that in one of the links ISTR. Have to look at that cell voltage vs SOC relationship with Li again.

BFL13 wrote:

Mobilesport wrote:
I was told to not use a voltmeter to try and determine soc% except at the very end when I hit 14.4 volts .

How/where did you see distortion ?
Let me know and I'll look into It and try to find a problem.

EDIT--here's another thing using your numbers. In the second hour, in the first half SOC went from 28-45% a rise of 17%. Instead of half of 53= 26.5
In the second half SOC went from 45-73% a rise of 28% (instead of 26.5)
BUT amps stayed at 53 the whole time. How can that be?
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Most of the distortion was in the first hour when amps stayed at near 53 for 53AH, but the percentage SOC said only 28%

53-28 = 25AH, which is most of that 33AH it went over.

It's like it didn't start the % SOC count until 25 amps had already been put out by the charger, but it is not quite like that because there was also 8AH missing in the second hour. Then it was on for the last 48 minutes. So it gets better with higher SOC.

Your plan to operate between 30% and up will keep you mostly clear of whatever is "wrong" at the low end. I think you are good to go for operating your BB the way you intend otherwise.

The wiring hot spot, converter mystery for max amps, and monitor questions are just other things of interest with your own situation AFAIK.

The only thing that I can think of off the top of my mind is maybe I turned my diesal heater on , when I first start it up I think it draws high amps , not sure how many but probably at least 10 amps could be more , and then alot of times when I first start the heater I run it at full blast (4.5 amps) for about 5 thru 8 minutes to get the room up to temp then I dial it back to low 1.5 amps , but I don't remember if I did that during the test but I'll be watching the numbers in the future.

There was a point that I turned eco throttle off on the genset trying to see if the amps would go higher , the amps did'nt go higher and so I shut eco throttle back off , I think I did that before that red line that's on the chart.
Eco throttle was off for about 3 minutes.

OK to just charge at 0%. I believe the BMS does allow slight over discharge and slight over charging. Just not enough to damage the battery too much.

Same as lead-acid. 10.5 volts is dead but you can certainly run lower even when your monitor says zero. I don't recommend testing the low (or high) voltage too often with Li or Pb.

Itinerant1 wrote:

Mobilesport wrote:
One thing I noticed when I was running my battery down trying to reach the BB low voltage disconnect,, I was paying attention to my capacity monitor the whole time and when it got down to 12% soc I was actually looking at the monitor and all the sudden it dropped like a rock from 12% soc to 0% soc instantly.

At that point I started thinking that I must be close to the battery shutting down.

Nope , it took another hour and a half until the battery shut down , volts were 9.3 volts when the battery shutdown.

I'm not saying my monitor is correct just what I witnessed.

That there is the knee. They'll give their all till....lights out.

Yeah but it went lights out a hour and a half after my Soc meter read 0% soc?
I was thinking that my soc % monitor should read 0% at least close to the time the lights go out.
Shouldn't the battery have been at 0ah when the lights went out?

MEXICOWANDERER wrote:
PS One single discharge to 0% destroys the batteries.

This is why the relay opens upon reaching a minimum voltage.
Instant stop until the battery is charged.

MEX, I know you know this but you know.... for the others learning.