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!

[pianotuna]

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.

[BFL13]

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. ( snipped para 2)

.

Not sure the following applies to the above, but there is some cause for worry in the way it is worded. Not trying to teach Granny how to suck eggs!

First issue is the AH capacity set. At just above freezing at 35F say, capacity can be 15% less than at 77F.

Second issue is charging efficiency where some of the amps go to heat. If the AH counter just goes back to what it was when AH were taken out, you are not back to where you were by some percentage. Usually, they say you need about 115% to get back to where you were.

With solar charging stopping at dusk, a Trimetric monitor will auto reset its AH counter like it does when "charging stops" when it thinks the batts are full. ( I think the Trimetric method of identifying Full is bogus, but never mind that) So Trimetric says to turn off the automatic reset feature if you have solar.

So now with solar, the Trimetric will just keep counting AH in and out and you have to reset it yourself whenever you can get to true full (as measured independently).

If you do not reset your monitor fairly often, it will be hopelessly out of whack, which could lead you to have undercharged, sulphated batteries.

We have had guys come on here who found their batteries shot while their monitor said they were fine. They had no clue about how much to believe their monitor's reading of percent SOC).

[RLS7201]

Vintage465 wrote:

RLS7201 wrote:
A shunt is just another device to get corroded and cause a bad connections.
Meters with hall effect sensors are the way to go for monitoring batteries now days.

All the goodies

Richard

So, with one of these, does the sensor need to go near or at the battery? I suppose if there was an online manual I could get all this info. Thinking that the Victron and the Morning Star are the "standards" for reliability and accuracy, how do these measure up? I like the idea of not needing to cut a shunt in but that's not really a deal breaker in my book. Most of my blanks in my mind are the location of sensors, the location of the read out, and what connects them together. It looks like the base station and the sensor goes near or at the battery and the read out goes........wherever?

The sensor does not need to be near the battery but it does need to surround the battery cable that the battery gets charged and discharged from.
I have done some extensive rewiring on my Bounder and my Hall Effect Sensor is about 13' from my batteries.

Richard

[Harvey51]

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.

[MDKMDK]

Itinerant1 wrote:
No fancy graphs.

Awww, why not?:B

Itinerant1 wrote:
Nice thing about lfp no need to fully charge unless you think it's needed.

Yup.
My solar is limited to around 10A on a good sun day (3X100Wpanels), although I've pulled closer to 15A on a perfect sun day last summer. I just happened to be looking at the display and noted the higher charge rate. Pretty much maxed out for my panels. That was before the lithiums were installed though, and was wasted on a couple of barely adequate factory installed FLAs.
My point (from my prior post) is that I believe my system is pretty much "set it, and forget it" now. I still look at the displays, but I worry a lot less about power management, since I added the lithium batteries to the mix.

[BFL13]

Great info on Li charging in the above two posts. That one with the graph shows they do act the same way as other batts for amps tapering when Vabs is reached.

The thing is, Vabs is reached at a much higher SOC for the charging rate. That graph has a 50% charging rate and Vabs reached at about 92% SOC when amps taper. BIG diff from Wets and AGMs as seen in my ugly graph. (Also Wets can't take 50% and only Lifeline AGMs can, where most AGMs say limit is 30%.)

Good point about not needing to get to 100% and better not to with Li.

For this thread, note that 2000w inverter on "two batteries" is not the same with two Li batts as with two Wets or AGMs. Must specify which kind the two are for what is possible.

[Itinerant1]

BFL13 wrote:
Not a clue about Li batt charging profiles. I ASSume they are like other batts where once their Vabs is reached and held there by the charger, that amps will have to taper as SOC rises.

Perhaps one of our members here with Li batts and nothing better to do, can make us an ugly graph like this, only using Li batts. (Or not so ugly if he is a computer whiz)

No fancy graphs.

If I was worrying or even trying to get a full charge on my 500ah bank.

Using your stated 50% SOC (250ah) and my limited charging ability from a eu2200i (I upgraded from previous eu2000i) it will accept bulk @100ah from my Magnum 3000w inverter/ charger till it reaches 14.1v 100% SOC in under 2.5 hours, then drop back to float @ 13.6v if left on charger.

On solar my max is 75-80a charging and it will accept that if the sun keeps shinning right to full.

Nice thing about lfp no need to fully charge unless you think it's needed.

[MDKMDK]

BFL13 wrote:
Not a clue about Li batt charging profiles. I ASSume they are like other batts where once their Vabs is reached and held there by the charger, that amps will have to taper as SOC rises.

Actually, everything I've read about them says hammer them with around 14.2 to 14.5 volts at whatever charging rate you can manage, until the BMS says they're full. They'll take the full charging current until the BMS burps, and says "I'm full, what's for dessert?". I think the 14.6V display posted earlier is how I would see my bank being full, or very close. They can also be discharged very low, without recharging them right away, or you can recharge them, your choice. They're probably the most flexible type of storage medium you can use these days.

BFL13 wrote:
Perhaps one of our members here with Li batts and nothing better to do, can make us an ugly graph like this, only using Li batts. (Or not so ugly if he is a computer whiz)

There's a chart in this link about half way down, if you really want one, and some explanatory text around it, as well. Battle Borns are used as the example brand, because that's what they sell. They always seem to get good reviews on the 'net. I've got Relions, also fairly well accepted as not bad.
Happy Lithiums

[Vintage465]

RLS7201 wrote:
A shunt is just another device to get corroded and cause a bad connections.
Meters with hall effect sensors are the way to go for monitoring batteries now days.

All the goodies

Richard

So, with one of these, does the sensor need to go near or at the battery? I suppose if there was an online manual I could get all this info. Thinking that the Victron and the Morning Star are the "standards" for reliability and accuracy, how do these measure up? I like the idea of not needing to cut a shunt in but that's not really a deal breaker in my book. Most of my blanks in my mind are the location of sensors, the location of the read out, and what connects them together. It looks like the base station and the sensor goes near or at the battery and the read out goes........wherever?

[BFL13]

Not a clue about Li batt charging profiles. I ASSume they are like other batts where once their Vabs is reached and held there by the charger, that amps will have to taper as SOC rises.

Perhaps one of our members here with Li batts and nothing better to do, can make us an ugly graph like this, only using Li batts. (Or not so ugly if he is a computer whiz)

[TomG2]

The OP confessed that he did not know all the technical jargon but people start referencing "Hall effect" and "Peurket's Law" as though it might help him. Nobody can answer his simple question?

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

Or at least educate us non experts on the reason to want or not want a battery monitor in the first place. What it can/cannot do for us.

[MDKMDK]

BFL13 wrote:
"When the amps start tapering down, you are getting closer to fully charged. "

With solar and its typically low charging rate (under 10%) you can be in the 90+ percent SOC zone, but with a better charging rate you will not be close. Even so it takes a long time to get from 90 to 100.

EG, at the 20% charging rate specified for the Bulk stage with AGMs amps will start to taper at about 75% SOC--a long way from being fully charged.

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

[BFL13]

"When the amps start tapering down, you are getting closer to fully charged. "

With solar and its typically low charging rate (under 10%) you can be in the 90+ percent SOC zone, but with a better charging rate you will not be close. Even so it takes a long time to get from 90 to 100.

EG, at the 20% charging rate specified for the Bulk stage with AGMs amps will start to taper at about 75% SOC--a long way from being fully charged.

[MDKMDK]

time2roll wrote:
If my voltmeter shows 14.5+ volts at some point in the day I know I have enough charge to get through the evening meal, tv, charge small items and run the furnace.

It doesn't get much simpler than that.:C

[time2roll]

If my voltmeter shows 14.5+ volts at some point in the day I know I have enough charge to get through the evening meal, tv, charge small items and run the furnace.

Remember this is solar. Not a 120 amp inverter/charger that will show full voltage in 20 minutes.