what are you using to monitor the current in and current out of the battery?

 

I am using a victron battery monitor. I'm not 100% sure what I should be looking for though, as far as charging in the most healthy way for longevity...

 

This is a voltage vs state of charge chart from this site, which has a lot of info on the care of LiFePo4 batteries.

​

State-Of-Charge​	Voltage at rest (zero current)​	Voltage under load (0.25C)​
100%​	14.0 Volt​	13.6 Volt​
99%​	13.8 Volt​	13.4 Volt​
90%​	13.4 Volt​	13.3 Volt​
70%​	13.2 Volt​	13.2 Volt​
40%​	13.2 Volt​	13.1 Volt​
30%​	13.0 Volt​	13.0 Volt​
20%​	12.9 Volt​	12.9 Volt​
17%​	12.8 Volt​	12.8 Volt​
14%​	12.6 Volt​	12.5 Volt​
9%​	12.4 Volt​	12.0 Volt​
0%​	10.4 Volt​	10.0 Volt​

So, by voltage, you are at near zero SOC.

What brand/model is the battery, and how are you getting the 65% SOC?

I intially charge my Li battery from the alternator via an isolator. I monitored the charging on a Victron battery monitor and found that it would go over the max recommended charging voltage given enough time, and I would cut the charging off manually. Promaster alternators vary a bit on what max voltage they eventually get to. I switched to a DC to DC charger to avoid having to watch it.
The BMS on the battery should cut charging off if the charge voltage gets quite high.

Battery isolators don't regulate or limit charging voltage at all - they just insure that the house battery does not run down the van starter battery. They are basically connecting the house battery to the van alternator whenever the engine is running. DC to DC chargers do a full multi stage charge of the house battery and they shut off charging if the battery gets to fully charged. I think probably should replace your isolator with a DC to DC charger.

With the battery as it is now, will it power your loads (eg fridge, lights, pump etc)?

Do you have anything that shows the actual charge rate going to the house battery? If you don't, its probably worth getting a DC camp multimeter that measures DC current when you clamp it over a wire. This would make it easier to figure out whats going on.

Gary

 

This is a voltage vs state of charge chart from this site, which has a lot of info on the care of LiFePo4 batteries.

​

State-Of-Charge​	Voltage at rest (zero current)​	Voltage under load (0.25C)​
100%​	14.0 Volt​	13.6 Volt​
99%​	13.8 Volt​	13.4 Volt​
90%​	13.4 Volt​	13.3 Volt​
70%​	13.2 Volt​	13.2 Volt​
40%​	13.2 Volt​	13.1 Volt​
30%​	13.0 Volt​	13.0 Volt​
20%​	12.9 Volt​	12.9 Volt​
17%​	12.8 Volt​	12.8 Volt​
14%​	12.6 Volt​	12.5 Volt​
9%​	12.4 Volt​	12.0 Volt​
0%​	10.4 Volt​	10.0 Volt​

So, by voltage, you are at near zero SOC.

What brand/model is the battery, and how are you getting the 65% SOC?

I intially charge my Li battery from the alternator via an isolator. I monitored the charging on a Victron battery monitor and found that it would go over the max recommended charging voltage given enough time, and I would cut the charging off manually. Promaster alternators vary a bit on what max voltage they eventually get to. I switched to a DC to DC charger to avoid having to watch it.
The BMS on the battery should cut charging off if the charge voltage gets quite high.

Battery isolators don't regulate or limit charging voltage at all - they just insure that the house battery does not run down the van starter battery. They are basically connecting the house battery to the van alternator whenever the engine is running. DC to DC chargers do a full multi stage charge of the house battery and they shut off charging if the battery gets to fully charged. I think probably should replace your isolator with a DC to DC charger.

With the battery as it is now, will it power your loads (eg fridge, lights, pump etc)?

Do you have anything that shows the actual charge rate going to the house battery? If you don't, its probably worth getting a DC camp multimeter that measures DC current when you clamp it over a wire. This would make it easier to figure out whats going on.

Gary

I have three Elfhub 12V 100Ah LiFePO4 Battery with BMS, from Amazon. Wired in parralel so my bank is 12v with 300ah.

I use victron battery monitor, but I've never checked to see what is happening when driving while it is charging via alternator... is there something I should look for, or should I switch off alternator charging at some point? For some reason I thought leaving my isolator on "auto" meant that it would detect what needed to happen and switch off automatucally if necessary, but I just learned overcharging can be bad. It does automatically disconnect/switch if it senses low voltage on either side.

I charged my battery bank to 100% yesterday. This morning it showed 85% at 13.15v.

 

I should have also asked, what battery brand? how many amp hours is the battery bank? inverter brand? what type/brand of isolator?

 

So, when you have the engine running, what kind of charging current does the battery monitor show?
It should be charging rapidly with the battery at that low voltage.

If you are not showing significant charging from the alternator with the battery voltage that low, I'd say that's an important thing to get to the bottom of. If it is not charging now with the low voltage, maybe look for something wrong in the charging system?

Gary

 

I will have to check these things next time we are driving...

 

do you have this display ?

 

I was never able to set up the app on my phone, so I just have the physical display contraption that came with it.

My battery isolator is actually an automatic charging relay:
Blue Sea Systems Automatic Charging Relay with the option for it to be on, off, or on auto. I have had it set to auto the while time. Worked fine on my AGM batteries for over two years.

My inverter is KISAE Technology IC122055 Abso Sine Wave Inverter Charger, 2000W, 55A

 

Most charts assume even wear in the entire battery pack, but you may have experienced a step change, not a gradual degradation of the battery pack. Just as with a lead acid battery, your battery is made up of individual primary cells connected in series. It sounds like you may have a bad cell in the pack. Only fix is to rebuild, or else replace the product.

 

I guess it is possible one of the batteries could be bad. We will have to check them. We tested them all before installing and they all had good readings. This was only a month ago...

 

lithium batteries are showing very low voltage (11v) at 65% charge

these number are wrong, I'm guessing the meter and the battery are not calibrated.

If you have an actually LiFePO4 charger charge them till it stops and reset the meter to 100%.

In lieu of a battery charger, run the engine and see if the battery monitor shows incoming wattage or amps. The alternator will output approx 14.1v and when the battery monitor displays only a couple of amps going into the batteries, reset the meter to 100%.

fwiw
Victron battery monitor config video

FWIW
random SOC curve, anything outside of the red circle is pointless

 

these number are wrong, I'm guessing the meter and the battery are not calibrated.

If you have an actually LiFePO4 charger charge them till it stops and reset the meter to 100%.

In lieu of a battery charger, run the engine and see if the battery monitor shows incoming wattage or amps. The alternator will output approx 14.1v and when the battery monitor displays only a couple of amps going into the batteries, reset the meter to 100%.

fwiw
Victron battery monitor config video

FWIW
random SOC curve, anything outside of the red circle is pointless
View attachment 90454

OK, Thank you! I will try that. Wow, that is probably what it is because it just didn't make sense! I never set up the battery monitor to the new batteries!

 

do have the manual for the BMV 700?

here's a link to the pdf:
Manual (victronenergy.com)

once you get the battery parameters set correctly and charge the battery it should sync automatically.

Based on the parameters you listed above (once you set the battery capacity to 300Ah) fully charged means 14.2 volts, less than 12 amps charging for 3 minutes.

If you have something on like a refrigerator or other high amp draw the current may never go below 12 amps, so you may have to turn everything off.

the manual shows how to manually set synch to 100% but I would only do that if you know the batteries are fully charged with either the alternator or a LiFePo4 plug in charger.

the Ah display on the bmv is Ah used not the Ah available. At 100% it would show 0Ah at 99.4% it would show -1.8Ah which is .6 % of 300Ah.

do you have a bmv 712 or a bmv 700?

 

do have the manual for the BMV 700?

here's a link to the pdf:
Manual (victronenergy.com)

once you get the battery parameters set correctly and charge the battery it should sync automatically.

Based on the parameters you listed above (once you set the battery capacity to 300Ah) fully charged means 14.2 volts, less than 12 amps charging for 3 minutes.

If you have something on like a refrigerator or other high amp draw the current may never go below 12 amps, so you may have to turn everything off.

the manual shows how to manually set synch to 100% but I would only do that if you know the batteries are fully charged with either the alternator or a LiFePo4 plug in charger.

the Ah display on the bmv is Ah used not the Ah available. At 100% it would show 0Ah at 99.4% it would show -1.8Ah which is .6 % of 300Ah.

do you have a bmv 712 or a bmv 700?

I have BMV 700.

Thank you for the link to the manual. I'm not sure if I'll be able to do what I need to do if I can't install the app on my phone...

 

Hi,
Your first post said the battery voltage was 11 volts, which is very very low. Is that still the case?

If the voltage is this low, then when you run the van you should see a good charging current on the battery monitor.

Can you let us know what happens when you do this?

Gary

 

Your Victron display will not show correctly until you tell the display precisely what your system is composed of, and accurately set the state of charge, ideally when the batteries are topped off via shore power or other reliable means of charging.

It is possible to set up the monitor manually via the display. I highly recommend you clear the space in your phone and use the app.

Note that the display will not show accurately when solar is feeding into the system due to the voltage boost.

 

Your Victron display will not show correctly until you tell the display precisely what your system is composed of, and accurately set the state of charge, ideally when the batteries are topped off via shore power or other reliable means of charging.

It is possible to set up the monitor manually via the display. I highly recommend you clear the space in your phone and use the app.

Note that the display will not show accurately when solar is feeding into the system due to the voltage boost.

BMV7OO will require a bluetooth smart dongle or ve direct to usb cable(to a computer) in order to use Victron Connect. The 700 is "dumb", vs. the BMV712 Smart which has built-in bluetooth.

Download the online manual. Dongle and usb cable part numbers are in this manual.

 

The victron battery monitor will show voltage and current accurately without any setup at all, and these are the things you need to troubleshoot your problem.

I have the same monitor, and did the original setup on the monitor itself without the bluetooth app - I later got the bluetooth dongle, and the app is nice to have.

I'd not worry too much about getting the monitor setup right until you figure out whats wrong with the electrical system.

Gary

 

I see it the same as @GaryBIS

Voltage & Current (shunt based) should be accurate.

All other parameters I believe are calculated by the Victron “computer” & the settings (variables) you set (user input setup). “GIGO” is in my forefront when I look at everything but voltage & amps & Ahrs.

If you have a multimeter that can be very helpful in diagnosis of your electrical system.

 

Aside from monitoring, I think tgregg is right. When I switched from agm to Li, I also changed charging from isolator to DC2DC charger. It's the right charging method for your Li.