Is it OK to keep charging when the LiFePo4 battery is 100% charged?

[Gypsy Freedom]

Don't try and scare me. OK you did scare me enough to run outside to check the charge again for the 100th time. But this battery has a BMS which appears to have a over-charge disconnect because it gets up to 15.8 volts for a split second before dropping back to 14.3 volts.

dont be so sure of that. what you are seeing is not a product of the bms

from the specs i saw on the link you posted, it states a low volt disconnect of 8.4 volts. that is way way lower than the minumum operating voltage of 11.5.

the max operating volts is 14.8, so even if there is an over volt shut down it is likely much higher. and if there is an over volt shutdown built into the bms, it may be like a fuse, and once tripped their may be no way to reset it. i have seen this or if you are lucky the over volt shut down will be a self resetting "breaker" type action and will reset after awhile. but when it does trip, the battery will just stop excepting any charger. in this case any charger hooked up will continue to climb in volts to its max.

what charger are you using to charge this? i dont recall seeing that specified

 

[poot_traveller]

Thank you for the informative post Gypsy. You're probably right and it is a crappy Chinese battery. But as long as it doesn't present any danger and lasts for at least two years, I'm happy.

 

[poot_traveller]

15.8v even for a split second is not going to be good for the battery. it might take a while to see the hurt but it could cause a problem sooner

Yeah it isn't good for the battery but the over-charge protection kicks in pretty quick and I shouldn't see the bad effects of those split second voltage spikes for a very long time.

 

[poot_traveller]

Gypsy, fantastic posts!

Not to scare you but that jump to 15.8v is not good and likely means no over-charge protection. Or its acting like its trying to equalize.

Check your controller settings. Thats not usual. Turn equalization off as well as temp compensation. Set your bulk/absorb to 14.2 - 14.6v and float to 13.8v.

The voltage gets dropped quickly, that will be the over-charge protection kicking in.

I might adjust the controller settings, like you recommend.

 

[poot_traveller]

dont be so sure of that. what you are seeing is not a product of the bms

from the specs i saw on the link you posted, it states a low volt disconnect of 8.4 volts. that is way way lower than the minumum operating voltage of 11.5.

the max operating volts is 14.8, so even if there is an over volt shut down it is likely much higher. and if there is an over volt shutdown built into the bms, it may be like a fuse, and once tripped their may be no way to reset it. i have seen this or if you are lucky the over volt shut down will be a self resetting "breaker" type action and will reset after awhile. but when it does trip, the battery will just stop excepting any charger. in this case any charger hooked up will continue to climb in volts to its max.

what charger are you using to charge this? i dont recall seeing that specified

Well, I guess I'll have to see how long it will last. If it dies inside two years then I've learned my lesson and know to get a good brand battery.

I only want two years out of it and I'm happy.

It is a MPPT controller from fazcorp.co.nz

 

[jonyjoe303]

the weight of the battery 13kgs is about 30 pounds which is about right for a 100 ah lifepo4. When you see the voltage jump to 15.8 volts that means the bms has tripped to stop the charge. That means the battery is fully charge (if you were slow charging) or one of the cells has reached 3.65 volts before the rest of the cells (happens when fast charging) but its close enough to a full charge.

The reason the voltage jumps to 15.8 volts is that the bms on the battery "leaks" voltage, the controller see's a undercharge battery connected and tries to force a charge on the battery. The bms won't allow any amps into the battery thats why you get voltage surges. 

It is very bad to leave the battery connected once the bms has tripped. Voltage surges will destroy any devices connected to the battery. Also you don't want to have the controller connected in that situation.  

I encounter what you are experiencing on my system, I added an overvoltage protection relay on my system that would trip a relay when the battery reach a certain voltage (14.4 volts) you never want the bms to trip. I also use a 12 volt voltage stabilizer and connect all 12 volt devices (like fans/pumps/lights) to protect from voltage surges. In my diagram the relay is installed between the solar panel and controller, when it disconnects the panel the controller goes to sleep thinking its night time. 



12 volt voltage stabilizer, any valuable devices go connected to this to protect from voltage surges. Fans/pumps can't handle any overvoltage even for a millisecond.

 

[Gypsy Freedom]

the weight of the battery 13kgs is about 30 pounds which is about right for a 100 ah lifepo4. When you see the voltage jump to 15.8 volts that means the bms has tripped to stop the charge. That means the battery is fully charge (if you were slow charging) or one of the cells has reached 3.65 volts before the rest of the cells (happens when fast charging) but its close enough to a full charge.

The reason the voltage jumps to 15.8 volts is that the bms on the battery "leaks" voltage, the controller see's a undercharge battery connected and tries to force a charge on the battery. The bms won't allow any amps into the battery thats why you get voltage surges. 

this is very poor and unsupported guidance. until you know what BMS is in that battery you are just guessing as to what parameters and actions are handled in/by the bms. BMS come in a wide range of quality and complexity and so far we have no idea what this one is. sure, some BMS board work the way you described, but many are far different.

your recommendation to never let the BMS trip is a wise one.

it is always a good idea to treat any lithium battery as if it had NO BMS, set up the charge and discharge controlls so the BMS is just a (hopefully) failsafe if something else in the system were to go wrong. especially in the case of an unknown battery/BMS from a source with zero tech support

as for the voltage jumping to 15.8 volts, even just momentarily. this concerns me. something is wrong and i am not talking about the BMS. the OP states the charger/controller is an MPPT from a NZ company. a link to that product would prove worthy as any decent mppt charge controller i have worked with will not go over the voltage set point even when disconnected from the battery. they just peak out at the set point and often lock up there. we need to find out why the source voltage (from the charger or controller) is ever getting that high.

since the provenience and pedigree of this battery and BMS is unknown the best we can do is set up outside protections (that should be set up anyways) to stop charge/voltage increase beyond the recommended 14.6v also to prevent discharge below the recommended 11.5 v then keeping the batteries cool as you can and not charging them if they freeze. these simple steps will likely ensure quite a nice life for this battery

following good sound procedures is much better than continuing to guess wildly about what the BMS might be doing

 

[Gypsy Freedom]

is this the controller in use?
https://fazcorp.co.nz/products/mppt-solar-charge-controller-30a-1224v-ml2430-1


and you have the 160 watt panel connected to that, correct?

what are the specs on this panel?

open circuit voltage?
max current?
and max power?

there should be a label that list these (may be describe in different terms) and other specs. a picture of that data label would help

 

[jonyjoe303]

On my solar system I tried both mppt and pwm controllers, and when they encounter a bms that has tripped to stop charging, both of them produce voltage surges, on my 240 watt system I saw voltage as high as 20 volts.

This only happens on bms that use mosfets(electronic relays) to control amps because electronic relays leak voltage. Almost all bms use mosfets, there are some bms that use mechanical relays but those are rare. Almost all batteries use mosfet bms because they are reliable and have no moving parts to break.

This lifepo4 battery is definitely using a mosfet bms because of the voltage surges encountered. To prevent these voltage surges the battery has to be charged to 14.4 volts or less and preferable at low amps so it stays in balance. But definitely stop charging once 14.4 volts is reached. This type of battery is one you never one to fully charge while on solar. These voltage surges only happen with solar controllers, AC and DC chargers are smart enough to shutoff when they encounter a full battery or battery that won't take a charge.

Another method to stop voltage surges
1. Charge a small lead acid from the battery out of the controller, and charge the lifepo4 from the aux out of the controller (the aux out is design not to produce voltage surges), the aux out will easily charge the battery as it produces the same amp output.

The overvoltage protection relay is a cheap method to try and control it, the overvoltage protection relay cost 5 dollars, the 30 amp automotive relay is another 4 dollars. This measures the voltage from the battery terminals so its fairly accurate.

 

[Gypsy Freedom]

notice my choice of words. a "quality" controller

just because it is likely a moffset based MBS does not magically tell us how it is set up or what protections are designed in

i stand by my recommendation to treat the battery as if there was no BMS and make sure the charge voltages are not exceeded and the battery does not get discharged below the recomended operating voltage.

the simple and sure way to protect a $600 ish us dollar investment

 

[poot_traveller]

the weight of the battery 13kgs is about 30 pounds which is about right for a 100 ah lifepo4. When you see the voltage jump to 15.8 volts that means the bms has tripped to stop the charge. That means the battery is fully charge (if you were slow charging) or one of the cells has reached 3.65 volts before the rest of the cells (happens when fast charging) but its close enough to a full charge.

The reason the voltage jumps to 15.8 volts is that the bms on the battery "leaks" voltage, the controller see's a undercharge battery connected and tries to force a charge on the battery. The bms won't allow any amps into the battery thats why you get voltage surges. 

It is very bad to leave the battery connected once the bms has tripped. Voltage surges will destroy any devices connected to the battery. Also you don't want to have the controller connected in that situation.  

I encounter what you are experiencing on my system, I added an overvoltage protection relay on my system that would trip a relay when the battery reach a certain voltage (14.4 volts) you never want the bms to trip. I also use a 12 volt voltage stabilizer and connect all 12 volt devices (like fans/pumps/lights) to protect from voltage surges. In my diagram the relay is installed between the solar panel and controller, when it disconnects the panel the controller goes to sleep thinking its night time. 



12 volt voltage stabilizer, any valuable devices go connected to this to protect from voltage surges. Fans/pumps can't handle any overvoltage even for a millisecond.

I've had a modem and laptop connect when it spikes to 15.8 v.  No problems.

If I'm not mistaken, I believe the inverter has protections for voltage spikes.

 

[poot_traveller]

this is very poor and unsupported guidance. until you know what BMS is in that battery you are just guessing as to what parameters and actions are handled in/by the bms. BMS come in a wide range of quality and complexity and so far we have no idea what this one is. sure, some BMS board work the way you described, but many are far different.

your recommendation to never let the BMS trip is a wise one.

it is always a good idea to treat any lithium battery as if it had NO BMS, set up the charge and discharge controlls so the BMS is just a (hopefully) failsafe if something else in the system were to go wrong. especially in the case of an unknown battery/BMS from a source with zero tech support

as for the voltage jumping to 15.8 volts, even just momentarily. this concerns me. something is wrong and i am not talking about the BMS. the OP states the charger/controller is an MPPT from a NZ company. a link to that product would prove worthy as any decent mppt charge controller i have worked with will not go over the voltage set point even when disconnected from the battery. they just peak out at the set point and often lock up there. we need to find out why the source voltage (from the charger or controller) is ever getting that high.

since the provenience and pedigree of this battery and BMS is unknown the best we can do is set up outside protections (that should be set up anyways) to stop charge/voltage increase beyond the recommended 14.6v also to prevent discharge below the recommended 11.5 v then keeping the batteries cool as you can and not charging them if they freeze. these simple steps will likely ensure quite a nice life for this battery

following good sound procedures is much better than continuing to guess wildly about what the BMS might be doing

Here is the MPPT controller I'm using:

https://fazcorp.co.nz/collections/m...pt-solar-charge-controller-30a-1224v-ml2430-1

I have a remote meter (display) with it as well.

 

[poot_traveller]

is this the controller in use?
https://fazcorp.co.nz/products/mppt-solar-charge-controller-30a-1224v-ml2430-1


and you have the 160 watt panel connected to that, correct?

what are the specs on this panel?

open circuit voltage?
max current?
and max power?

there should be a label that list these (may be describe in different terms) and other specs. a picture of that data label would help

Yep Gypsy, that's the controller.

The label is on the underneath of the panel which is screwed and VHB tapped to the roof. However,
I went back through some of my old posts and found the specifics in one of my posts....

Solar panel:
Standar power: 160 Watts
Maximum power voltage: 17.8
Maximum power current: 9.0A
Open Circuit voltage: 21.1V
Short Circuit current: 9.5A

 

[Gypsy Freedom]

ah, thanks

they did not have good specs or an easy download for that unit that i saw quickly. i will see what i can find out now that i know that is the one

 

[Gypsy Freedom]

hey Poot, i emailed the distributor and they responded pretty quick and sent me downloads for the controller and both the remote display and the bluetooth interface

do you have either of them, the blue tooth or the remote display?

reading through the controller files they sent now

 

[Gypsy Freedom]

i see the base unit has some presets for various battery type that you can choose from. do you have the basic manual to know how to change the battery type and confirm the setting? have you set it to the 12v lifepo4? what color is the "BAT type indication" led showing

 

[poot_traveller]

hey Poot, i emailed the distributor and they responded pretty quick and sent me downloads for the controller and both the remote display and the bluetooth interface

do you have either of them, the blue tooth or the remote display?

reading through the controller files they sent now

Yeah they respond real quick, even on weekends. I wish my new Internet Service Provider was like that; but they don't answer the phone, they don't answer emails, they don't answer facebook messenger.... they don't answer nothing.

I have the remote display which I currently use. I also have the bluetooth but I don't need it.

 

[poot_traveller]

i see the base unit has some presets for various battery type that you can choose from. do you have the basic manual to know how to change the battery type and confirm the setting? have you set it to the 12v lifepo4? what color is the "BAT type indication" led showing

Yeah it's set to 12v Li. It's showing blue.

 

[Gypsy Freedom]

so then as you probably have alrady seen in the specs. the lifepo4 12v setting has the boost charge limited to 14.4 volts and everything else seams turned off

my interpretation of "boost charge" is what we in the states call absorption switch over voltage

i did not see a clear explanation of how each step or parameter was implemented but for all intents and purposes, it sure looks like the setting you have the charger should only be putting out 14.4 volts max. this is well under even the max working voltage of 14.6 listed for the battery. this should not be tripping any over voltage protection from the BMS if it even has one

since you are seeing the the much higher voltage, even just briefly. tells me something is wrong. could be BMS could be charger

the first thing i would do it try to determine that. easiest way i can think of would be for you to take the charge controller and hook it up to a basic lead acid battery with no BMS and leave the settings on the lifepo4 then see how the voltage goes. if it comes up to 14.4 and stays or slowly drops off. then i would say the charger is doing its job and something in the BMS is cutting off the charge below that point and the sudden discinnect is causing the controller to spike.

but if you see the voltage climb considerably higher on the lead acid battery than that 14.4 spec, then i would suspect something wrong with the charger

based on the specs and the settings you are using, this should be working so i think there is something wrong. let us know if you do the test with the controller on a different (lead acid) battery

 

[poot_traveller]

something in the BMS is cutting off the charge below that point and the sudden discinnect is causing the controller to spike.

I haven't got a lead acid battery to carry out the test but I suspect you're right about the BMS cutting off the charge before it gets to 14.4v and the sudden disconnect is causing the controller to spike.

I'll take a look at the settings on the remote display when I get home from work in about 12 hours. I've got the remote display manual with me, and it says; boost charge voltage is 14.4v, floating charge voltage is 13.8v, equalizing charge voltage is 15.5v. I believe these are the default settings on the controller.

I think I know why the BMS is cutting off the charge; it is constantly charging when the battery is 100% charged which is why the battery is cutting off the charge before it gets to 14.4v and this in turn causes the controller to spike...….or no?