Community Forums

Mathisw · 10-08-2021, 08:52 AM

I’m trying to learn.

I saw someone post this image as illustration of battery charge stages. See first photo.

This made me wonder what my inverter panel is REALLY telling me. So my questions are:

(1) When my Inverter panel shows “Bulk Charging 13.6v” (see second photo) is the 13.6 my current level of my battery bank OR is “13.6” what the charger is sending to my battery bank to charge them up?

(2) When my inverter panel shows “Silent 13.6v” (see third photo) is it telling me charge complete and my battery bank level is currently 13.6v? That’s what I have, ready to use?

I have always thought the volts shown on my inverter is like a fuel gauge, so to speak. In other words I’d like to check the panel and see how much battery power I have (fully charged, almost fully charged, getting low, etc.). It seems the volts I encounter change around a lot … up, down even in a short period of time. I would think I’d see, let’s say, 13.6v at first and then if only running on inverter with minimal electrical use (fridge and a few lights) I could go back in 3 hours and maybe it changed from 13.6 to 13.5. Then a few hours later 13.5 to 13.4 and so on. Does that make sense?

I will add that our 2017 (new to us) coach came with lithium batteries and solar already installed. So I realize I have to consider some solar charging could cause my batteries to charge even while on inverter only. So my scenario about about staring at 13.6 and watching it reduce down slowly over several hours of battery use may not completely apply when … considering I have solar. But I’d at least like to understand the concepts of charge and discharge.

Thanks!

theboondork. · 10-08-2021, 09:27 AM

Your going in the right direction since you have lithium iron batteries and solar panels to charge them, I've been using lithium iron batteries for several years now and their great.

But if you want something like a DC electric "fuel gauge" your not going to get it with the factory voltmeter, all you will get is a rough estimation of what's going on with your batteries. If you want to know exactly how many amps are going into your batteries, how many amps are coming out of your batteries in real time, and how many amps you have left you have to get one of these.

Best RV Battery Monitor | Bogart Engineering

I've had one of these battery monitors in all my RVs, and since I boondock most of the time I consider it an essential piece of equipment.

theboondork.com

757driver · 10-08-2021, 10:07 AM

Quote:

Originally Posted by Mathisw

I’m trying to learn.

I saw someone post this image as illustration of battery charge stages. See first photo.

This made me wonder what my inverter panel is REALLY telling me. So my questions are:

(1) When my Inverter panel shows “Bulk Charging 13.6v” (see second photo) is the 13.6 my current level of my battery bank OR is “13.6” what the charger is sending to my battery bank to charge them up?

(2) When my inverter panel shows “Silent 13.6v” (see third photo) is it telling me charge complete and my battery bank level is currently 13.6v? That’s what I have, ready to use?

I have always thought the volts shown on my inverter is like a fuel gauge, so to speak. In other words I’d like to check the panel and see how much battery power I have (fully charged, almost fully charged, getting low, etc.). It seems the volts I encounter change around a lot … up, down even in a short period of time. I would think I’d see, let’s say, 13.6v at first and then if only running on inverter with minimal electrical use (fridge and a few lights) I could go back in 3 hours and maybe it changed from 13.6 to 13.5. Then a few hours later 13.5 to 13.4 and so on. Does that make sense?

I will add that our 2017 (new to us) coach came with lithium batteries and solar already installed. So I realize I have to consider some solar charging could cause my batteries to charge even while on inverter only. So my scenario about about staring at 13.6 and watching it reduce down slowly over several hours of battery use may not completely apply when … considering I have solar. But I’d at least like to understand the concepts of charge and discharge.

Thanks!

Mathis,

With your lithium bank the voltage shown on your Magnum remote is the voltage the bank is at whether charging or not. With the relatively flat charge and discharge curve of lithium you cannot use it to judge the SOC (state of charge) of your bank.

With your lithium bank (from your Magnum chargers standpoint) it will either show you charging (Bulk) or not charging (Silent) but really nothing more. If you catch it when Bulk changes to Silent you can be assured your lithium bank is at 99-100% SOC. If you catch it when Silent changes to Bulk your bank is approximately 40% SOC.

One of your Magnum remotes has the Magnum BMK attached so you meter button (push and then rotate the dial) will show you SOC of your bank in percent but if your bank has not been fully charged in a while this value will be increasingly inaccurate as time goes by so use it as a reference.

Your lithium bank will show 13.x volts until either a low SOC or a high SOC. In between it will not change much and as you said your solar array will add to the charging when in sunny conditions, and a large load on either inverter will temporarily drop the indicated voltage as the Magnum inverter/chargers do not use a dedicated voltage sense line.

Mathisw · 10-12-2021, 09:06 AM

Hi Don. Thanks so much for that info (and all the other info prior!). I think what really hit home for me (finally) was your comment “ With the relatively flat charge and discharge curve of lithium you cannot use it to judge the SOC (state of charge) of your bank.” I went and found a discharge chart so I could see what it looks like and now I see, my lithium battery power is nice, until it starts to drop, then it drops quickly. I am posting a photo here because this illustration really helped me. So my big takeaway is SOC is really a moment in time view of my battery charge status … and it not something I can accurately use to know much much battery power I have left to use.

Thanks again … to Don and everyone here!

Mathis

RichardE · 10-12-2021, 09:47 PM

Hang on.

If you have the Battery Monitor Kit installed with the remote you have, then you can indeed program the system to show your SOC. The SOC will be calculated more on amps in and amps out, than voltage. The Magnum will go through a self cal procedure when the SOC is first activated. The SOC will certainly allow you to estimate the power you have remaining.

The programming will require you to input the size of the battery bank.

Based on your pictures, the Magnum is set up to Bulk Charge, they go into Silent Mode. You can program it to behave differently, for example, you can program it to go from Bulk to Float. Five years ago, the conventional wisdom was the LiPo batteries did not like float, but that opinion has mostly changed. I float mine at 13.4.

Perhaps some more time with the ME ARC manual, specifically Custom Charge Profiles and studying the charge profiles recommended by the battery manufacturer would be beneficial. I say this only because there are many parameters that need to be input to maximize your Magnum charger/LiPo battery setup.