12V House Battery Shuts Down With Battery Fully Charged

[gurroz]

We have a 2016 Minnie Winnie 25B. We have Lithium batteries, a lithium converter, and DC to DC charger. It worked flawlessly until last night while camping. I checked the SOC and we were at 90%, about 30 minutes later the 12V shut down. I started the coach and 12V power came back immediately showing 13.1V. I ran the generator for 30 minutes and turned it off. About 3 minutes later the 12V power shut down again. I started the coach again and let it run for 30 minutes or so. The 12V power stayed on but then shut down after about 30 minutes. We did run the water heater and furnace during that time. We drove 5 hours home and that battery showed 100% SOC. I turned off the coach and within 2 minutes the 12V power was off. I turned on the coach and the power came back on. Once it was turned off the 12V shut down again in about 2 minutes. I think it may be a relay. Do you have any ideas?

[gurroz]

I may have used the wrong term, I said relay and I think I meant solenoid. Also, I disconnected the inverter to see if that was the problem, however, it is still doing the same thing.

[Morich]

This will be kind of a tough one to figure if you are not well experienced with a number of smaller points on how the RV batteries work. They seem so simple but get terribly confusing!

What you tell us really just sounds like the coach batteries may be bad or possibly there is some type of major drain making them discharge way too fast. But when you drive or run the generator, you can look at the voltage and it looks like they are charged or even above fully charged!

Keep in mind that the voltage is checked at the posts, not all down through the chemicals and lead in the battery. If we charge and check the voltage during that charging or too soon after the charge is stopped, the batteries will show what is called "surface charge".
We need to charge and then wait a couple hours for the chemical reaction to become stable all down through the battery to get the real voltage! That's part of the confusion!

But when we drive there is a solenoid that connects the chassis and coach batteries together. There is also a dash switch with various names like "boost" or "aux" that also ties them together. When you see low voltage on the coach , start the engine and then see good high voltage, what you are seeing is the engine alternator feeding power to both sets of batteries! We know that is happening as a fully charged new lead/ acid battery will only show a stable voltage of 12.8 or so! Lithium has slightly different numbers.

The real truth is that is takes 6-8 hours to really recharge a fully drained lead acid battery! When you charged for 30 minutes, you might see good voltage at the posts but most of the battery is still dead! So it starts to do it's job but soon dies.
Lithium operates with slightly different numbers but the same general idea! I just don't work lithium to know the correct numbers!

I would work the problem by first getting both battery groups fully charged. That may take several hours and then let them set for at least a couple hours to become stable again.
During this time, I would open the coach battery disconnect switch to avoid running excess power out if there is a major problem in the coach wiring. No point in putting power out into a short of some type while also trying to put power in the batteries!

I suspect it may just be a problem with the voltage just running down and they may need to be recharged, but also be alert for any odd behavior as there may be some type problem.
If there are not fuses or breakers tripping, it really sounds more like simply a battery charge problem more than actual equipment failure.

See if getting them fully charged will chase the problem away and let us know where you wind up. We can assist in chasing the problem further but lets see if the easy stuff will work first?

[gurroz]

Morich, thanks for the reply. These are lithium batteries. I use a Victron battery monitor which connects to my phone app via Bluetooth. It shows a charge of 13.4V presently. I generally check it several times throughout the day and monitor it when my solar panels are deployed. If I have a question I will double check it with a multi-meter. I have not had a problem with it for the past two years, this only started yesterday.

[l1v3fr33ord1]

gurroz-

What is the voltage at the battery posts when not connected to any charging source or load? It should be around 12.6V. Any voltage in the 13V+ range indicates a charging source is present.

If you can have the batteries load-tested, do so. It's possible one has failed, and no longer maintains a charge.

[gurroz]

Originally Posted by l1v3fr33ord1

gurroz-

What is the voltage at the battery posts when not connected to any charging source or load? It should be around 12.6V. Any voltage in the 13V+ range indicates a charging source is present.

If you can have the batteries load-tested, do so. It's possible one has failed, and no longer maintains a charge.

Will do, thank you.

[creativepart]

Originally Posted by l1v3fr33ord1

What is the voltage at the battery posts when not connected to any charging source or load? It should be around 12.6V. Any voltage in the 13V+ range indicates a charging source is present.

This is not correct for the Lithium Iron Phosphate batteries that gurroz has. The info you provided only applies to Lead Acid batteries.

Most LFP batteries rest at 13.5v and charge at 14.2v or higher. Also they don’t show surface voltage after charging. I’m not positive but they also can’t be load tested the same as LA batteries.

[Morich]

Yes, the numbers and charging are different and that needs to be figured in! The basic idea is that when you run the engine or use other charging, you can't get a real idea of the total charge.
My main thought was when you run the engine for a short time and see it looking good but it dies soon after, I suspect it was not actually well charged.

But that is where better testing is needed. First to see that the battery did get fully charged and will hold that charge. Second to see if there is some form of massive drain taking the c harge out way too fast.
That second part should not happen if the fuses and breakers are set up and of the right size. those should cut off massive drains!
And that design question can come into play when the systems have been changed. We have to start with the idea that all was fine but also be aware that mistakes are possible.
Since there are so many different issues possible, I might start in this order.
1. Make sure the charging system is getting power to the batteries.
2. Make sure the voltage testing is correct. This can be a problem if the monitor or
remote items become a problem.
3. Make sure the batteries will take and hold that charge. They can have internal
problems that we need to be aware of in the chase.
4. When we have good, well charged batteries, do they perform as expected or is there
a problem with how power is used?

But what we DON'T know about the modified system is far greater than what we DO know!
I tend to be a simple thinker, so one thing I always assume is there may be dirty cables. One way the builtin monitor may think all is well when we have dead batteries is if the connection for using the power are not the same as where we monitor the power!
So we have to start at the basics and work upward!

[creativepart]

When you say you ran the water heater and the heater, do you mean you ran the water heater on AC power from an inverter? If so that combo is a huge power drain. It may not matter in figuring out your problem but as a general rule the water heater should only run on electric when you’re on shore power with unlimited 110vac power.

How many LFP batteries do you have? It is possible that the BMS inside your battery has a problem and is shutting down. I have two LFP batteries and one of them has, after two years, developed a BMS failure. It won’t take a charge and it shuts down in 10 seconds of use. Having two batteries I couldn’t tell what was happening since one battery was working normally and one had failed. The only way to figure it out was to remove the parallel connection to separate the two batteries. Then I could see that one was working and the other not.

There could be other explanations for your problem, too. But they will be unique to how you are using the batteries and we don’t know that. Operating normally LFP batteries will shut down if too many amps are pulled out above their continuous rated output at one time. You could even have a problem with some electrical device that when you try to power it that this demands too much power and your BMS in the battery is shutting down. In which case it wouldn’t be a battery problem at all.

We don’t know how many batteries you have, nor their brand, nor their specs. So, it’s hard to determine what your problem is exactly. We also don’t know what inverter you have and what you are running or trying to run from it when it shuts down. We’re not even sure when you say “all 12v shuts down” exactly what you mean. Is it all 12v items including lights, etc?

In other words, we need more info to even start to figure this out. And, folks here without much LFP experience might not understand all the unique properties of your LFP batteries so responses may be limited.

[creativepart]

Originally Posted by gurroz

Morich, thanks for the reply. These are lithium batteries.

Yes, when we try to help gurroz with this issue everyone needs to understand that LFP batteries are very different than Lead Acid batteries.

Pretty much all the usual notions of how lead acid batteries behave - from charging, to resting, to testing is very different and do not apply to his Lithium batteries.

[gurroz]

Thanks to all for your input. I have one 150Ah lithium battery. I checked it with my multi-meter this morning and it is dead. I put in a claim with Ohmuu Lithium Batteries this morning as I am 42 months into the 48 month warranty. I will see what they say about the warranty, they no longer make a 150Ah battery. Their 180Ah is $1,000, which seems high by today's standards. I can buy a 300Ah for around $500. Someone asked about running the water heater, I was dry camping and only running off DC power.

[creativepart]

Originally Posted by gurroz

Someone asked about running the water heater, I was dry camping and only running off DC power.

I asked that... can't you run your WH off of propane? When Dry Camping that is the way to go. The AC water heater element is as big a draw as your microwave or A/C unit.

I agree with your assessment to seek warranty replacement from the manufacturer.

As to 300ah for $500... that could put you right back in this situation. You probably should look at batteries in the middle of the range from too cheap to too expensive. Most of the middle of the road better batteries are $700 to $900 for 300 ah.

My bad battery is a Renogy 300ah that I spent $1000 for 2.5 years ago. I can replace it for about $800.

Renogy by the way is not super responsive. When I first reported the trouble with the battery they immediately opened a case and asked for the battery's serial number which I provided immediately. It's been two weeks and multiple attempts at contact and they have gone silent. So, I'd never recommend a Renogy product.

[Ray,IN]

I agree with creative part; the electric water heater put too much draw on the battery and the BMS turned off the battery to prevent damage.
Remember, a 1,400W 120VAC draw is 1/10 of the wattage draw from the 12VDC battery.

[gurroz]

Originally Posted by creativepart

As to 300ah for $500... that could put you right back in this situation. You probably should look at batteries in the middle of the range from too cheap to too expensive. Most of the middle of the road better batteries are $700 to $900 for 300 ah.

My bad battery is a Renogy 300ah that I spent $1000 for 2.5 years ago. I can replace it for about $800.

I spoke with the company today and made arrangements to exchange the battery next month. They moved from Phoenix to Prescott which is about 100 miles away. I will be in the area in August so it should work out fine. Their 180Ah battery is $899 which seems high, bit he said no proration it will be an even exchange.

I currently use Renogy solar panels and DC to DC charger. They are a good company.

[creativepart]

Originally Posted by gurroz

I currently use Renogy solar panels and DC to DC charger. They are a good company.

I thought so too, until I needed support and have not been able to get them to respond to 5-attempts over 2+ weeks.

[cruizerEd]

Originally Posted by gurroz

Thanks to all for your input. I have one 150Ah lithium battery. I checked it with my multi-meter this morning .... .

This is why batteries with a BMS that provides telemetry about the system state is so important. Knowing the state of each cell it's voltage and current to one hundredth of a volt or amp, temperature, faults, helps detect problems early and isolate problem faster.

Bluetooth version are handy but hardwired to the rest of your system is more reliable and can provide more functionality.