Monitoring Battery Discharge

[john61ct]

Originally Posted by smac999

that never plug in and never get a bank full, and never properly reset them when full. you likely have issues.

SmartGauge and maybe SG200 do reduce those issues.

But even with straight AH counters but of good quality, ongoing attention to the details, following MaineSail's guidelines can compensate and ensure pretty good accuracy.

[heron237]

you sound like a gear head, this'll work: plugs for yer "GOODIES"

[rgleason]

Delfin wrote:
When current acceptance drops to a certain point, the Ah used resets to zero.

The SG200 does use trailing amps in its algorythm, there is a setting for that. Chris W. could tell you how this is used, but then he'd probably be giving away hard won trade secrets. It is likely to be a somewhat complex calculation in any case.

I agree that with soc and soh, and starting (new) 20hr AH you have the information necessary, particularly if the SG200 is accurate enough.

At this point I have no data that indicates the SG200 is not accurate to 4-5%, but I need to gain more experience and do some better discharge tests.

I do hope the SG200 App will show lifetime history and ah and I hope it will have a summary screen which includes all data.

I ordered this unit with a free upgrade to the BT app when it comes out.

[john61ct]

Just pointing out, "starting (new) 20hr AH" is also SoH, in fact should be the baseline for 100%.

With good model batteries during breaking in period but after commissioning protocols, usually over the mfg published spec.

Especially with LFP

[wingssail]

Originally Posted by heron237

you sound like a gear head, this'll work: plugs for yer "GOODIES"

Well, I like this one that you displayed! You can see the battery state in an instant whenever you walk by the nav station.

Oh, the LCD displays for AH usage and remaining, etc, are cool, and make good income for the manufacturers that sell them, but the battery voltage is a pretty good (AND SIMPLE) indicator for me.

I am always amazed at how quickly the discussions evolve into which piece of equipment is best and why, down to the last infinite detail, as if finding out that answer will somehow enhance a person's cruising enjoyment. But I never hear any discussion about going sailing and learning how to sail your boat in different conditions, which would probably do much more for your future enjoyment of cruising.

I suspect it leads to the common feeling people have which goes something like this (thought but never spoken) "I have all the best equipment and all the coolest gadgets, but I still don't like sailing."

So my advice is, get a simple meter, then get out there and use it.

[rgleason]

Originally Posted by john61ct

Just pointing out, "starting (new) 20hr AH" is also SoH, in fact should be the baseline for 100%.

With good model batteries during breaking in period but after commissioning protocols, usually over the mfg published spec.

Especially with LFP

SOH =20hr AH , yes of course.



To keep it less complicated, Balmar uses and I believe wants the manufacturer battery specs.

[john61ct]

If you measure it more precisely yourself, IMO that's what should go into that field.

Later on, after SoH gets below the mfg rating, could always reset the learning curve and change the setting to mfg 20-hour rating.

Actually if doing subsequent periodic load tests to verify SG200's accuracy, could keep modifying that setting on the meter, since load testing and / or equalizing will restore some capacity, the BM showing SoH declining would be a good indicator to do another round.

Just keep the mfg rating in mind for actually deciding on EoL replacement time.

[Pete the Cat]

Originally Posted by smac999

what you want is a battery monitor.

victron 702 (or new bluetooth one, 712?)

xantrax linklite / link pro.

the new smart gauge I haven't seen so can't comment.


yes the old fashioned way was to watch the volt meter drop...

Yes, and the volt meter drop method was generally useless and misleading. With the evolution of battery monitoring systems with everything running through a shunt, you can get a good idea of what is going in and out of your bank. It shocked me into realizing that my “smart” regulator and large battery bank were actually being chronically undercharged. Getting too large a bank and too sophiticated a system actually backfires. Would never have understood what was going on until I invested in a battery monitoring system.

[Antares Sky]

I really like the Victron 712 with the built in Bluetoothhat I currently have. It’s very convenient to use
And the cost compared to the new soon to be released Balmar is way more affordable. The extra cost for an add on Bluetooth doggle that the Balmar needs is ridiculous to me. I saw the Balmar at the Annapolis sailboat show in October this year and Spoke with a rep. it’s a nice looking unit but wow pricey!☹️
I purchased the Victron 712 from Amazon. It was easy to install and setup.


Glen

[FlyingScot]

Anyone use the Blue Sea Systems battery monitor?
https://www.bluesea.com/products/1830/M2_DC_SoC_Monitor

It appears to monitor two additional battery voltages, plus the main house bank. Good for catamarans (and others).

[toddedger]

I just traded my little boat with LiFePo4, and upgraded to larger boat with LA. Iast week I installed the new beta SG200. So far I wish it would show SOC at a tenth of a percent for large banks. It says my my six T-105 Trojans are at 90% SOH. Will be interesting to see what equalizing does to that number.

I like the fact that it will work with LiFePo4 if I decide to upgrade. It could really shine if it works for LiFePo4. The Link moitor just didn't cut it.

Looking forward to seeing the Bluetooth App. I would love to see it show some plots over time of some of the info. There's lots of potential for making this a real gem. I hope they stick with it and make upgrades in firmware along the way.

Lets add Bluetooth control to the regulators. And how about a battery combiner that I can turn on or off and program with an app?

Poor Chris is probably saying shut up

[MJH]

Originally Posted by Nostromo

I have a pretty basic question: what is the best way to monitor how much juice is left in your house batteries when you are out and about for a few nights? I am confident I have plenty of new battery capacity to run all the goodies in the boat, but the question is, for how long? I have seen the load tables that show how much current each gizmo is drawing, etc., but those seem to be focused on system design, not operation. Am I just watching the battery status - volt meter to see the voltage start to drop...? Thanks!

How do you monitor the batteries...install a BETTERY MONITOR.

~ ~ _/) ~ ~ MJH

[tbodine88]

Originally Posted by Nostromo

I have a pretty basic question: what is the best way to monitor how much juice is left in your house batteries when you are out and about for a few nights? I am confident I have plenty of new battery capacity to run all the goodies in the boat, but the question is, for how long? I have seen the load tables that show how much current each gizmo is drawing, etc., but those seem to be focused on system design, not operation. Am I just watching the battery status - volt meter to see the voltage start to drop...? Thanks!

Here is my battery monitor "Trac Dynamics T10001"
Frimi's Battery Monitor

[EngNate]

OP said "out and about for a few nights". It's not a cheap solution, but a DCM-100 battery monitor and an SMS-100 text module from Maretron would provide the ability to text in and receive a status message that includes battery voltage. Unfortunately, state of charge cannot be obtained this way, however, with a Maretron display alerts can be setup for any monitored parameter and be sent by sms. Quite a bit higher on the $ scale you can get full remote monitoring on a mobile device - it requires the N2K View PC software to configure screens for the device, as well as the IP Gateway and internet connection.

[GrowleyMonster]

FLA batteries?


Determining state of charge by checking battery voltage is most accurate when the batts have been resting for 24 hours, or at least 12 hours. If you are discharging batteries then your voltage reading will be down a bit more than the resting voltage. Heavier discharge, more down. Light discharge, less down. The good news though, is that means you will apparently have less juice than you actually do. So you won't be toasting your batteries. If you calculate that your batteries are at say 50%, they might actually be at 55% or 60% but they won't be 40% or 30%. You can also check Specific Gravity, but remember to correct SG higher by .004 for each ten degrees (fahrenheit, of course) above 80f. Vice versa for cooler than 80f.



There are cheap monitors all over fleabay and amazon that will display system voltage, discharge amps, watts, and watt/hours used. These cheap (under $20 including shunt) monitors do not typically give you percentage state of charge but you will know the SOC fairly close by the watt/hours discharged since last reset. They don't reset automatically... you have to do it yourself. Push a button.


The "SmartGuage" battery monitor looks like a great piece of gear but to get the full benefit of it you need to take the time to program it properly. You will I think need your Peukert coefficient or else your capacity at 20hr disch rate and your reserve or else capacity at some other discharge rate. You can discover this yourself, actually. Set it up right, and this gadget will give you a fairly accurate picture of where you are in your batteries' discharge cycle.


There are also "dumb guage" bar graph displays that work like the gas guage on your car, about as accurate as the monitor I mentioned above that gives all the data.



Another tactic is to have two separate banks. Run on one for 24 hours. Check the offline bank's voltage and SG, take readings twice, three times if the first two dont agree. Record your observations and switch banks. Every 24 hours check the bank that has rested and then bring it online.



Resting means no load. It also means no charging. Charge while it is online.


There are disadvantages to having split banks but at low discharge currents it is small potatoes. Some zealots will go to war with you over this, but it's your boat. There are also obvious advantages to a split bank. Put them in parallel with an Off/A/B/Both switch, when you need lots of juice for starting an engine or whatevah.