Is my battery too strong?

emmikel

Member
Joined
Jan 6, 2025
Messages
12
Location
United States
I keep my RV plugged into shore power and I have a lifepo4 battery hooked up in my Cherokee 27rr. The converter charges the battery but once it finishes charging with bulk charge, the battery has a higher voltage than the converter. This is causing my battery to drain 1 amp hour to power all the DC appliances instead of using the converter and once the 1 ah is drained the converter kicks back on to charge it.

This cycle repeats a few times an hour and I believe this will put undue stress on the battery. Is there any way for me to force the DC system to run off of just the converter while plugged in? Or do I just need to keep the battery disconnected when I want to keep the power running from the converter?

Side question: how much damage will this do to the battery if I do let it cycle 1 ah 35+ times a day?
 
Sounds as though there may be a converter issue. Even after the converter has brought the battery to 100% SOC, there are some parasitic loads which will slowly pull the battery down. This is seen by the converter and the charge cycle starts all over. This too could be affected by the temperature of the battery or the battery BMS, or even the temperature of the converter.

Without knowing the charging voltages and current values out of the converter to the battery, anything is possible. I would also be concerned that the DC negative connection to the trailer frame along with the negative of the converter could be an issue. I know I found one with ours and others have commented they have found this to be a weak point.

Specifically, on our TT the DC negative battery cable was connected to the frame by a single #10 self-drilling screw. While chasing an intermittent electrical issue, I found the connection to be loose and rusty. I removed the screw, drilled the hole to 1/4". Using an abrasive wheel, I removed the paint from around the hole on both sides of the trailer frame. I reattached everything using good quality stainless hardware, lock washers and lock nuts. All of my issues were resolved.

Your issue could be as simple as a loose or poor connection. High charging current can cause a questionable connection to heat. Then when it cools, it is then a different electrical value. The converter may see this and respond accordingly.

Sounds like time for some routine and preventative maintenance.

Bob
 
I keep my RV plugged into shore power and I have a lifepo4 battery hooked up in my Cherokee 27rr. The converter charges the battery but once it finishes charging with bulk charge, the battery has a higher voltage than the converter. This is causing my battery to drain 1 amp hour to power all the DC appliances instead of using the converter and once the 1 ah is drained the converter kicks back on to charge it.

This cycle repeats a few times an hour and I believe this will put undue stress on the battery. Is there any way for me to force the DC system to run off of just the converter while plugged in? Or do I just need to keep the battery disconnected when I want to keep the power running from the converter?

Side question: how much damage will this do to the battery if I do let it cycle 1 ah 35+ times a day?
You may consider a different converter although I doubt any damage is really occurring.

I have a Victron Phoenix IP-43 12/50 kncerter charger. It's fully programmable and mine is set for a 14.4v bulk rate and when this is achieved for a set time ( depending on total battery capacity) it switches to a 13.5v float and eventually Storage level. After a given period (settable by user) it goes into a brief Bulk/absorption phase. I have mine set for 7 days.


Remember, a "cycle" on a battery is a full discharge followed by a complete recharge.

The scenario you describe would add one cycle to a 100ah battery roughly every 3 days. A 200 ah battery would receive a full cycle every 6 days, 300 amp capacity a cycle every 9 days.

Now consider that even low cost batteries are capable of delivering several thousand cycles before capacity reaches only 80% of original capacity.

With this in mind, most lifepo4 batteries will most likely outlive many of us so don't overthink this.
 
Sounds as though there may be a converter issue. Even after the converter has brought the battery to 100% SOC, there are some parasitic loads which will slowly pull the battery down. This is seen by the converter and the charge cycle starts all over. This too could be affected by the temperature of the battery or the battery BMS, or even the temperature of the converter.

Without knowing the charging voltages and current values out of the converter to the battery, anything is possible. I would also be concerned that the DC negative connection to the trailer frame along with the negative of the converter could be an issue. I know I found one with ours and others have commented they have found this to be a weak point.

Specifically, on our TT the DC negative battery cable was connected to the frame by a single #10 self-drilling screw. While chasing an intermittent electrical issue, I found the connection to be loose and rusty. I removed the screw, drilled the hole to 1/4". Using an abrasive wheel, I removed the paint from around the hole on both sides of the trailer frame. I reattached everything using good quality stainless hardware, lock washers and lock nuts. All of my issues were resolved.

Your issue could be as simple as a loose or poor connection. High charging current can cause a questionable connection to heat. Then when it cools, it is then a different electrical value. The converter may see this and respond accordingly.

Sounds like time for some routine and preventative maintenance.

Bob
This is totally normal as a LiFePo4 charge profile calls for 14v + but Float only 13.5v. Yes, the usage by connected devices draws battery down enough to trigger a other Bulk/Absorption cycle by the converter.
The OEM converter/chargers are very rudimentary (and cheap) so user programming like Victron and others provide is non-existent.

Maintenance is always important but I seriously doubt it's an issue in this case. Technically it's a function. Of the "re-bulk delay or threshold which in most OEM converter/chargers is hard programmed by the mfr.

One of the reasons I'm a major fan of Victron products. The user has a lot more control.
 
This is totally normal as a LiFePo4 charge profile calls for 14v + but Float only 13.5v. Yes, the usage by connected devices draws battery down enough to trigger a other Bulk/Absorption cycle by the converter.
The OEM converter/chargers are very rudimentary (and cheap) so user programming like Victron and others provide is non-existent.

Maintenance is always important but I seriously doubt it's an issue in this case. Technically it's a function. Of the "re-bulk delay or threshold which in most OEM converter/chargers is hard programmed by the mfr.

One of the reasons I'm a major fan of Victron products. The user has a lot more control.
So I don’t have to worry about it?

I can just let the battery charge and discharge all day every day?

And does it matter if I have 2 batteries in parallel? Obviously they are the exact same battery, but would it be better to do just 1?
 
So I don’t have to worry about it?

I can just let the battery charge and discharge all day every day?

And does it matter if I have 2 batteries in parallel? Obviously they are the exact same battery, but would it be better to do just 1?
Two batteries lessen the effect on each single battery.

Don't worry. Just enjoy.
 
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put a couple of good solar panels on your roof
turn OFF your converter
mine has been off for 9 months
and I can camp indefinitely

got 2 x 370w for $300.00
$85.00 solar controller (bluetooth)
works like a dream for standard 12v b devices and battery usage... (no inverter)

if you want inverter look at a system with bigger battery and more solar

PS.. try to camp in spots that allow some reasonable sun
 
Update: temgot, the battery manufacturer has informed me that microcharging is not recommended for their batteries.

So my options are to buy a new converter that allows me to make it stay in bulk charge mode 100% of the time, or keep the batteries disconnected until I actually need to use them...
 
what voltages are you actually seeing... and what are you using to measure the voltage?

just about all chargers will charge at a higher voltage and then drop down to a float
Older converters may float at around 13.2 and wont go back into full charging mode until battery has dropped even further below 13.2

the battery is designed to handle charge/discharge
what it does need is to stay around 13.6 for a while so it can do internal cell balancing

wiring and connections on a older trailer need to be looked at if you want newer converter to work properly
may be just easier to add a small 120v lifepo4 charger ... once in a while (every 2 weeks ) put the small charger on so battery has a chance to balance

OR use solar.... get some benefit from the addition.. longer boondocking if you like idea of remote camping.
 
Update: temgot, the battery manufacturer has informed me that microcharging is not recommended for their batteries.

So my options are to buy a new converter that allows me to make it stay in bulk charge mode 100% of the time, or keep the batteries disconnected until I actually need to use them...
I'd keep the batteries disconnected until you actually need to use them.
If you're on 'shore power', you don't need the batteries.
Once they are disconnected, they should hold their charge.
Just remember to turn them on before you tow because the brakes need a battery to work.
 
what voltages are you actually seeing... and what are you using to measure the voltage?

just about all chargers will charge at a higher voltage and then drop down to a float
Older converters may float at around 13.2 and wont go back into full charging mode until battery has dropped even further below 13.2

the battery is designed to handle charge/discharge
what it does need is to stay around 13.6 for a while so it can do internal cell balancing

wiring and connections on a older trailer need to be looked at if you want newer converter to work properly
may be just easier to add a small 120v lifepo4 charger ... once in a while (every 2 weeks ) put the small charger on so battery has a chance to balance

OR use solar.... get some benefit from the addition.. longer boondocking if you like idea of remote camping.
Battery is at 14.2v when fully charged, converter is at 13.8v float. From my understanding, (and what appears to be happening in real time) is that the higher voltage is pushing through the system. So the battery charges all the way up, then starts powering all the dc appliances until it reaches float voltage at which time the converter kicks back to bulk charge mode and recharges it (this is about 0.7 ah out of the 300ah battery). Temgot (the battery manufacturer) says that this is not advisable.

I am using a Klein cl800 volt meter to measure voltages.

The RV is less than 12 months off the factory line and does have a 100w solar panel on top that is charging the battery but not enough to keep it charged while my fridge is pulling power.

I am attempting to find a way to either keep the converter always running at bulk charge voltage or limit the battery so that it discharges at 13.7v to allow the converter to power everything until the shore power is disconnected. So far, I have been unsuccessful in finding a way to do either with the equipment I have and due to needing to purchase a truck, I am not in a position to buy new equipment to solve the issue.

Current solution is to just keep the battery disconnected while on shore power and let the solar panel keep it charged while the converter powers the rv.
 
I'd keep the batteries disconnected until you actually need to use them.
If you're on 'shore power', you don't need the batteries.
Once they are disconnected, they should hold their charge.
Just remember to turn them on before you tow because the brakes need a battery to work.
That is the solution I am currently using as the power has only shut off twice. once when I plugged in too many things, and once when the shore power went wonky. Both times it was my watchdog that cut the power.
 
Where do you live?

It is usually ok to disconnect batteries six months. No problem usually. Not sure a trickle charger or converter is a better plan.

Batteries properly tested are 0-12.6 volts. Any higher reading just reflects the chargers voltage or a residual charge.

Here solar panels connected to a battery are not so reliable. Snow does them in.
 
I think you are worrying about a non-existent problem. Just let the system cycle at the full charge state like it is doing. I don't believe or trust what your battery vendor has told you.

FWIW, here's the behavior of a much more expensive system used for home backup power. The battery bank and inverter/charger are made by the same company and the charging cycle is controlled by their BMS communications. What you see in this graph is essentially the same as what is happening with your system. If this is bad for the LFP battery chemistry, then my equipment vendor has a charging/maintaining algorithm that is destroying their own batteries.

I'll convert voltages for this description... this graph shows a battery being slowly discharged at 70 watts until the battery voltage reaches 54.1V (13.5V), and once an hour the system applies a 56V (14.0V) charging voltage to bring the battery back to full.

vbat_cycle.png


It's weird that your converter is switching back to bulk charge voltage so frequently instead of remaining at the float voltage, but I don't think you are doing any harm here. Which model of converter do you have? I didn't see it mentioned anywhere in this thread.

The 14.2V full charge battery voltage you are measuring is an abnormally high voltage you should only see when a charging voltage is applied and the battery has stopped taking in more charging current. If you are measuring that 14.2V without a charging voltage, then it is a residual surface charge on the battery that will quickly decay and settle down to something closer to 13.6V, regardless of whether there is a parasitic load on the battery. With the cycling between 14.2V and 13.8V that you mentioned above, very little energy is being cycled in & out of the battery.
 
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I think you are worrying about a non-existent problem.
THIS
-------------------------------------------

nominal lifepo4 battery voltage at 100% is 13.6 -13.8
if you try to keep it at 14.2 you will probably get it to 110% CAPACITY
but risk straining the battery more

there is absolutely no benefit or reason to try and keep it at 14.2v charge
manufacturers have settled on 13.8 as the best voltage

If you don't intend to use it ... put it is storage mode
discharge to around 40-50% then disconnect the battery

since the battery is designed to last so long at 13.8v I don't disconnect... never gets too cold here
I will be dead when my batteries need replacing

even if you did setup charging to the 14.2 you would have to be able to setup the battery BMS to take it The internal BMS should shut off charging before the battery gets to the 14.2

for any charge to FLOW to the battery the charge voltage must be a bit higher
they don't expect you to get the battery voltage upto 14.2

perfectly normal for the battery drop down a little bit after the higher charging voltage is removed

blog-lifepo4-battery-voltage-chart.webp




That is the solution I am currently using as the power has only shut off twice. once when I plugged in too many things, and once when the shore power went wonky. Both times it was my watchdog that cut the power.
this sound like the 120v got tripped (overloaded)
nothing to do with battery 12v
 
Having trouble about what is best for lithium batteries in storage over the winter.

They talk about storing them pretty fully charged.

Never seen a definitive statement that a trickle charge is a good plan.

Some say store them in your home over the winter.

Mine are in storage in Ohio in the rv. 13.25 volts on a 16 degree day. Was 14. 25 just off the Victron charger. SOC of the batteries says 99% after several weeks in cold weather.

Becoming confused.
 
makes no sense to me to discharge them to 50% as some manufactures want
probably some stupid rule for long tern storage....... before shipping

Biggest issue is not to charge them when THEY are too cold
if you storing simply disconnect them
Bring them inside if you want .... they don't self discharge a lot so no trickle is required

If you using them in cold weather
keep them warm with a heating pad and blanket
or move batteries inside ... then charging wont be a problem if they are warm

If you are warm then they will be too.
 
Having trouble about what is best for lithium batteries in storage over the winter
They talk about storing them pretty fully charged.

Never seen a definitive statement that a trickle charge is a good plan.
True static storage is supposed to be at around 50% SOC according to best-practice.

I've yet to find definitive information about whether shallow-cycle "station keeping" at or near 100% is considered "storage." For the OP, if he's going to disconnect batteries and leave them static/idle for several months he should first discharge them to around 50% and then disconnect. For something like my home system where I want the backup ready to switch over when the grid fails, I will keep them maintained at 100% and not worry about whether I'm causing a degradation that won't be seen until 10 years from now.
Some say store them in your home over the winter.
Not needed. Just guard against charging in sub-freezing weather. My RV batteries have BMS low-temp protection, but I still open the disconnect switch when I know we'll have a hard freeze. Otherwise, I leave them connected and let my converter keep them at 100% through the winter.
Mine are in storage in Ohio in the rv. 13.25 volts on a 16 degree day. Was 14. 25 just off the Victron charger. SOC of the batteries says 99% after several weeks in cold weather.
That sounds normal. Assuming your RV has been stored for ~3 months, with a 3% monthly self-discharge rate the actual SOC can't be any higher than about 90%. Note that self-discharge current is not measured by the BMS and will not be included in its SOC calculations, so the calculated SOC will remain high and drift further from the actual SOC as the self-discharge occurs. Same is true for a SOC reported by an external shunt monitor. 13.25V is a reasonable value for a static-idle battery that's at somewhere between 70~90% actual SOC.
Becoming confused.
 
makes no sense to me to discharge them to 50% as some manufactures want
probably some stupid rule for long tern storage....... before shipping
There's apparently a legal requirement that batteries cannot be shipped at full capacity and must be near 50%. So I'm sure battery vendors store at that value after manufacturing and testing, but I don't know if that would be the source of their end-user advice to store at 50%. I've seen numerous vendor recommendations, white-papers, etc. advising static storage should be at 50%, presumably due to battery chemistry to get the best longevity, but I've never seen a scientific explanation about why this would be true.
 

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