Battery Monitors

[Vintage465]

I've nearly completed my upgrade to my Solar System(Pics coming when I'm done). Thinking(after the fact of course)that I should have considered a Battery Monitor in the upgrade, or at least preparations for such an install.

I know very little about battery monitors except that most experienced boon dockers with solar recommend them. I don't see any reason to try and take a low rent route to get this done and end up with an iffy unit that works her and there or not at all.

I hear the Morning Star unit is kind of the standard. I also hear some pretty good things about Victron.

So:
1. I assume a shunt needs to be installed some where on the positive near the battery bank. I am "Parroting" this term "shunt" , as I really don't know what the term "Shunt" means. I've seen the pic's of one and it looks pretty straight forward to install. Is the shunt the only thing that needs to be installed for the monitor to gather info? How would I size the shunt? We only use 12v. No inverters. The only high draw item we have is the furnace. How close or far from the batteries is acceptable to install the shunt. Should it be very easily accessible? Meaning, is there a reason to view it regularly?

2. I have Samlex PWM 30a controller, will a Victron or Morning Star work with that controller? I looked in some installation info and reading material and that info doesn't seem be very forthwith as of course they are hoping one uses their charge controller.

3. In order to have Bluetooth connectability for monitoring does there have to be a "base unit hardwired somewhere that the iPhone can snag the signal?
Is that what I'd be doing by installing a shunt with the wiring going to the hard wired battery monitor?

4. Maybe there is a good link to send me to that has "battery monitors 101"?

Thanks!

[BFL13]

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

98% for charging efficiency makes sense, based on what has been said. They do heat up some during a recharge.

I don't like Bogart's idea of "full" so I don't use that to get a percentage SOC, but I still get lots of use from my Trimetric I got ten years ago.

Others who know Li batts can answer the questions.

[steveh27]

I have 200ah lifepo4 battery bank and pd 35 amp charger/converter and Trimetric meter.

Here's what Bogart Mfg said about the Trimetric:

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

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

Progressive Dynamics said to use the boost button to fully charge the battery.

I am not using the RV now due to health issues, haven't since July. I've had the rv on shore power for 5 weeks now without pushing in the boost button as lifeo4 are best stored at 50-60% soc or so. My meter says SOC = 72% and it's not being charged, just maintained. It has gotten below freezing at night & the BMS is supposed to shut off the charging then. I hope this is working well. I could limp out and spend time unhooking from shore power & removing the batteries to bring inside. But if what I have now is OK I may leave it that way. Not sure though.

[BFL13]

Thanks for the additional info. No doubt that the Li batts are a good thing.

I still don't understand how the percentage SOC can be at all accurate, but OTOH you don't need it to be. And I don't have to figure it out, thank goodness. I guess you "have to be there" to see how it all works.

IMO Li does not change the general monitor situation that has been explained to the OP. In all cases, the monitor must be reset often enough using other meters/evidence to keep it from becoming off-kilter and giving misleading info.

[Itinerant1]

"How can you tell if the AH counter is correct wrt to SOC?"

My system is made up of 20 prismatic 100ah cells, 4s5p= 500ah 12v. I have EMS/ CPU (BMS) system a little more robust than a dropin battery.

The Magnum has nothing to do with AH counting it's done through the EMS of the Elite GBS batteries.

The EMS system has a minimum recorded resolution of +/- 0.5A so any current below that level is not accounted for. The system could be setup for a finer resolution, but the shunt value would have to be reduced which reduces the systems maximum current capability. 

The system will reset the capacity to 100% whenever the pack voltage reaches 3.49 to 3.52 V/cell on average.

No, you don't need to charge to 14.6v (maybe dropins so they can sync their capacity % depends on the bms). A charger that can be adjusted to your specific needs is best, not one size fits all.

I have my Magnum inverter/ charger programmed Bulk 14.1v, Absorb 14.2v (10 minute minimum, can't be turned off), Float 13.6v. The Magnum PT100 is linked in the Me-Arc to follow the settings of the IC.

"Li batts are just weird!"

That they might be but after living off them for 43 months now using 99% of the time charging with solar, using them at low SOC with heavy draw items, not worring if they're fully charged or not, with 500 + full cycles on them now.
A happy camper here.

[BFL13]

Very interesting.

So temperature went up 10 degrees going from 86% SOC to 99%, which is like what happens with AGMs and Wets. That heat must be counted as a "loss" in charging efficiency somehow.

I am deeply suspicious of those percentage SOC figures where the AH count needs to be set to zero at 100% true full, and the Lis are not brought to true full. They even say they do better not being brought to 100%. How can you tell if the AH counter is correct wrt to SOC?

Where you get ahead with the Li is how you don't need to do 50-80s to stay in the good zone for fast generator recharging. The batts keep accepting the high amps to a high SOC, which is very different from Wets and AGMs.

I am not familiar with the way the Magnum does AH counting on a recharge. Is there any default factor for charging efficiency as there is with Trimetric's 94% (which can be set to some other percentage) ?

Also curious that the recharge was at 13.x and low 14, where supposedly you need the charger to be able to do 14.6 Vabs for Li batts. You don't get to Vabs until a very high SOC though, and you don't want to get to 100, so who cares? I am missing something there I think.

EDIT--this blurb seems to be wrong in saying if you don't use the right voltage and get them full, they will be under-charged and have a shorter life. That is in conflict with saying they do better not being full. He does say that 14.6 might be different for different Li batts, so that is why he also promotes the adjustable voltage chargers for Li duty.

http://www.bestconverter.com/Progressive-Dynamics-Inteli-Power-Lithium_c_221.html

One thing might be the voltage drop still significant at 100 amps on the wires. The charger voltage will show as higher than at the batteries, so it matters where you take the reading maybe. With Wets and AGMs, the amps have tapered a lot by those high SOCs, so voltage drop is not much by then.

Li batts are just weird! 🙂

[Itinerant1]

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. 😉

[allen8106]

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

[BFL13]

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.

[Itinerant1]

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.

[MrWizard]

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

[dieseltruckdriv]

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.

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.

[BFL13]

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. ?

[2oldman]

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

[Harvey51]

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.