Low priced LiFePO4 Batteries vs High priced

[newhaul]

Originally Posted by T1 Terry

What brand cells do you use and what BMS do you have. 11 yrs of 24/7 use, the $10,000 worth of cells don't have many survivors, mostly learning about the number of fail safes are required and and you can't build anything to be stupid proof .... me in this case, I bypassed all the fail safe measures in an attempt to get power into the battery pack after 2 weeks of constant rain or rain clouds so thick there was very little solar ... left for a 6 week travelling holiday at 3 am and forgot all about the bypass wire ... you guessed it, the sun appear the day we left. The 720Ah 12v pack was at 16.5v, all the inverters had shut down due to over voltage and two fridge freezers absolutely full had defrosted and became home to multiple generations of flies.
Also learnt about punching the pins out of the MC4 connectors and soldering the pins together with heat shrink over them after discovering part of the solar wasn't actually reaching the controller because the pins in the MC4 connectors only make contact via a small spring insert in the female sleeve, if that gets pushed up deeper into the sleeve, there is no connection between the male and female pins ....... This is something we find in a lot of solar systems where panels have failed, the string was open circuit and one by one the panels failed after being turned into heaters.

One 400Ah @ 12v nom. is still functioning in the Mazda motorhome, it doubles as the starter battery and has been below 10v a few times till I mastered the battery isolation at 5% SOC and getting the BMV to reset to a correct 100% SOC where all the cells were better than 3.5v in every cell so a 14v reset to 100% SOC with 5% current flow for 1 minute. That eliminated the 14v reset when the cells were not within a reasonable balance of each other .... The 2 cells Mainsail has on his info site blown up like they were pregnant are two replacement cells I was going to put in that battery pack, just based on age because the cells were well past the "10 yrs shelf life or combination of shelf life and use was the point the cells collapsed" B/S that was rife across the interweb "those in the know" sites. They had been 4 yrs old from production before I received them, then I'd used them for 7 yrs, we were heading off on another long road trip and decided to play it safe .....
Long story short, had visitors, thought I'd turned the charger off but it was the wrong power point I switched off ..... just before heading to bed some 10 hrs later, the battery was so hot I could feel it as I walked past.
The old cells went back in along with other cells I'd retired and that pack is still going today ..... So the 10 yr calendar life was proved to be B/S as well ...

T1 Terry

Ok my bank 250ah calb aluminum case cells ( they were sold to me as 240ah purchased from factory ) . A dead simple Daly 200 amp single in single out .
Average usage is 25ah to 30ah per day. Charging comes primarily from 200 watts solar through MPPT controller. 4 years in and still have 263.8ah total capacity.

[T1 Terry]

Originally Posted by newhaul

Ok my bank 250ah calb aluminum case cells ( they were sold to me as 240ah purchased from factory ) . A dead simple Daly 200 amp single in single out .
Average usage is 25ah to 30ah per day. Charging comes primarily from 200 watts solar through MPPT controller. 4 years in and still have 263.8ah total capacity.

You should see a long life from that set up, once you add an inverter and capacitive and/or inductive loads, things start to become a lot more difficult, the Daly BMS uses a Mosfet to turn the loads off and they can't handle ripple loads or high in rush currents .... so you have to add filters and precharge circuits and ..... let's just say the simplicity is lost :lol:

We are having problems sourcing the Gigavac GX 14 contactors we have been using and all the other alternatives, including the Gigavac GX 11 series, weld the contactors closed because the sudden inrush current causes the contact faces to chatter, creating an arc and presto, welding the faces together is achieved Now we have have to build precharge circuits and delayed load switching so the inverters have a chance to charge the capacitors before the contactors close and then the full inverter load can be applied .... after the smoke coming out of Mosfet solid state relays that claimed they could handle 700 amps, we have given up and we're going back to contactors .....

T1 Terry

[newhaul]

Originally Posted by T1 Terry

You should see a long life from that set up, once you add an inverter and capacitive and/or inductive loads, things start to become a lot more difficult, the Daly BMS uses a Mosfet to turn the loads off and they can't handle ripple loads or high in rush currents .... so you have to add filters and precharge circuits and ..... let's just say the simplicity is lost :lol:

We are having problems sourcing the Gigavac GX 14 contactors we have been using and all the other alternatives, including the Gigavac GX 11 series, weld the contactors closed because the sudden inrush current causes the contact faces to chatter, creating an arc and presto, welding the faces together is achieved Now we have have to build precharge circuits and delayed load switching so the inverters have a chance to charge the capacitors before the contactors close and then the full inverter load can be applied .... after the smoke coming out of Mosfet solid state relays that claimed they could handle 700 amps, we have given up and we're going back to contactors .....

T1 Terry

I have a 2512 trace inverter charger up to 120 amps charge have it set at 50 for now infinite adjustable on everything on it. Runs my dorm fridge , rice cooker, and my TV. Always on in port just in case the power trips out .5ms auto transfer to battery inverter if pass thru goes out. I turn the charger side off unless I actually need it . Let the solar do the job. So far the only time I pull heavy is when I'm doing my annual capacity test and then it's just 100 amps draw with a portable heater. So still not quite a .5C have newwave2 induction hot plate but not using yet.

[T1 Terry]

I wrote a post on another thread that also should appear here. Rather rewriting it, I'll just post the link for those interested
https://www.cruisersforum.com/forums...ml#post3699463

T1 Terry

[newhaul]

Originally Posted by T1 Terry

I wrote a post on another thread that also should appear here. Rather rewriting it, I'll just post the link for those interested
https://www.cruisersforum.com/forums...ml#post3699463

T1 Terry

think part of the problem we are seeing is multiple inverters in parallel. This wasn't really a thing in the past, inverters were much smaller output and switch off as soon as they were no longer needed, the batteries back then just couldn't handle the constant load, not necessarily because of capacity, but more because of the slower recharging ability.
Once quality lithium systems hit the scene, the inverters got bigger, more solar and a lot more 240vac appliances where extra low voltage appliances (12v or 24v) were used in the past. A much bigger inverter household fridge and freezer, even pigeon pairs in the bigger rigs, full electric galley, hot water and air conditioning. Now the single inverter wasn't enough to run more than one high draw appliance at a time .... we now have systems with 3 inverters in parallel, 15kW continuous output and up to 30kW surge load that can be accessed for around 10 mins without any of the inverters tripping out.
Once the inverter/s are powered up and only the on/off of the inverters is used, there is no inrush current, but if the system has battery isolation contactors or the BMS uses Mosfets to isolate the load, then the inrush current is only limited by the size of the cabling and the ability of the battery to supply instant high current.
This is where lithium batteries add a problem that lead acid batteries did not. Lithium batteries can supply huge instant current, 20C or more, 800Ah x 20C = 16000 amps, so the cable or the fuse becomes the limiting factor .... A 300 amp maxi fuse can handle a 300% overload very short term, 900 amps really puts a strain across the faces of contactors and Mosfets just aren't in the hunt because they by nature limit current and this generates heat that just can't be moved quick enough ..... if it open circuits then things just don't turn on, but if the punch through, then there is no turning them off, just like a welded contactor.

Basically what i'm saying is, if a contactor that is rated for 350 amp continuous welds closed due to inrush current on a single 3,000w inverter, a BMS rated for 500 amps is not going to handle the inrush current if it is using a Mosfet to do the load switching ...... so be aware if you are using drop in batteries, the BMS inside the battery might fail open circuit and then you'll know straight away, but if it punches through, there is nothing protecting that battery from being dragged down to destructively low voltage ..... if the other batteries in parallel drop out due to low voltage, the ones with the punched through Mosfets will still be feeding power until they are destroyed ..... when the charging resumes and the batteries that drop out reconnect to the load, they are going to try to recharge the destroyed batteries that have had cells suffer reverse current flow ..... the end result is a full set of dead batteries in parallel.

The fix is to add a precharge circuit before the inverter, one for each if needed, this will stop the inrush current destroying the Mosfets in the drop in batteries.

T1 Terry

there ya go

[T1 Terry]

Originally Posted by newhaul

think part of the problem we are seeing is multiple inverters in parallel. This wasn't really a thing in the past, inverters were much smaller output and switch off as soon as they were no longer needed, the batteries back then just couldn't handle the constant load, not necessarily because of capacity, but more because of the slower recharging ability.
Once quality lithium systems hit the scene, the inverters got bigger, more solar and a lot more 240vac appliances where extra low voltage appliances (12v or 24v) were used in the past. A much bigger inverter household fridge and freezer, even pigeon pairs in the bigger rigs, full electric galley, hot water and air conditioning. Now the single inverter wasn't enough to run more than one high draw appliance at a time .... we now have systems with 3 inverters in parallel, 15kW continuous output and up to 30kW surge load that can be accessed for around 10 mins without any of the inverters tripping out.
Once the inverter/s are powered up and only the on/off of the inverters is used, there is no inrush current, but if the system has battery isolation contactors or the BMS uses Mosfets to isolate the load, then the inrush current is only limited by the size of the cabling and the ability of the battery to supply instant high current.
This is where lithium batteries add a problem that lead acid batteries did not. Lithium batteries can supply huge instant current, 20C or more, 800Ah x 20C = 16000 amps, so the cable or the fuse becomes the limiting factor .... A 300 amp maxi fuse can handle a 300% overload very short term, 900 amps really puts a strain across the faces of contactors and Mosfets just aren't in the hunt because they by nature limit current and this generates heat that just can't be moved quick enough ..... if it open circuits then things just don't turn on, but if the punch through, then there is no turning them off, just like a welded contactor.

Basically what i'm saying is, if a contactor that is rated for 350 amp continuous welds closed due to inrush current on a single 3,000w inverter, a BMS rated for 500 amps is not going to handle the inrush current if it is using a Mosfet to do the load switching ...... so be aware if you are using drop in batteries, the BMS inside the battery might fail open circuit and then you'll know straight away, but if it punches through, there is nothing protecting that battery from being dragged down to destructively low voltage ..... if the other batteries in parallel drop out due to low voltage, the ones with the punched through Mosfets will still be feeding power until they are destroyed ..... when the charging resumes and the batteries that drop out reconnect to the load, they are going to try to recharge the destroyed batteries that have had cells suffer reverse current flow ..... the end result is a full set of dead batteries in parallel.

The fix is to add a precharge circuit before the inverter, one for each if needed, this will stop the inrush current destroying the Mosfets in the drop in batteries.

T1 Terry

there ya go

:lol: Now I'll make everyone read it 3 times

T1 Terry

[newhaul]

Originally Posted by T1 Terry

:lol: Now I'll make everyone read it 3 times

T1 Terry

Works for me some need to read it 3 times.

[fxykty]

Originally Posted by T1 Terry

We are having problems sourcing the Gigavac GX 14 contactors we have been using and all the other alternatives, including the Gigavac GX 11 series, weld the contactors closed because the sudden inrush current causes the contact faces to chatter, creating an arc and presto, welding the faces together is achieved Now we have have to build precharge circuits and delayed load switching so the inverters have a chance to charge the capacitors before the contactors close and then the full inverter load can be applied .... after the smoke coming out of Mosfet solid state relays that claimed they could handle 700 amps, we have given up and we're going back to contactors .....



T1 Terry

We use Gigavac contactors to disconnect our load and charge bus from the battery based on BMS relay commands. There is a GX 14 on our charge bus and a GX 16 on our load bus. They are normally open and activated by default to keep the circuits closed.

They run very hot. Is that normal?

We are planning to replace them with Blue Seas ML-RBS 7713 to reduce that heat.

[T1 Terry]

Originally Posted by fxykty

We use Gigavac contactors to disconnect our load and charge bus from the battery based on BMS relay commands. There is a GX 14 on our charge bus and a GX 16 on our load bus. They are normally open and activated by default to keep the circuits closed.

They run very hot. Is that normal?

We are planning to replace them with Blue Seas ML-RBS 7713 to reduce that heat.

I guess it's a case of personal judgement as to what is considered very hot, to me it would indicate it would be unpleasant to painful to hold a finger on the hot part. If it just feels hot to the touch but you can hold a finger on it, I'd class that as very warm and often relates to the air movement avaiable around it. It is an electromagnet after all and the winding do generate some heat.
What voltage are you running into these Gigavacs? We use 24v Gigavacs on the 12v and 24v systems to keep the heat down, the 24v units will operate fine as long as the voltage is up around 12v or more and they will hold closed down to around 10v, maybe even lower.

T1 Terry

[s/v Jedi]

Originally Posted by fxykty

We use Gigavac contactors to disconnect our load and charge bus from the battery based on BMS relay commands. There is a GX 14 on our charge bus and a GX 16 on our load bus. They are normally open and activated by default to keep the circuits closed.

They run very hot. Is that normal?

We are planning to replace them with Blue Seas ML-RBS 7713 to reduce that heat.

Exactly, some are propagating the myth that these don’t heat up but they do and it is a continuous waste of energy.

The 7713 will use no energy at all and completely eliminate the problem

I like the pulsed versions better and they are more affordable because of higher sales, but your system may not be compatible with them. There are circuits to adapt them though and they can be very easy. CatNewBee has this info and it’s buried in his superthread incl. schematics

[fxykty]

Originally Posted by T1 Terry

I guess it's a case of personal judgement as to what is considered very hot, to me it would indicate it would be unpleasant to painful to hold a finger on the hot part. If it just feels hot to the touch but you can hold a finger on it, I'd class that as very warm and often relates to the air movement avaiable around it. It is an electromagnet after all and the winding do generate some heat.

What voltage are you running into these Gigavacs? We use 24v Gigavacs on the 12v and 24v systems to keep the heat down, the 24v units will operate fine as long as the voltage is up around 12v or more and they will hold closed down to around 10v, maybe even lower.



T1 Terry

12V units and very warm - finger touch gets uncomfortable in about 30 seconds. That’s even with normal currents (+- 10A). With big charging or big loads (150-350A) the heat level doesn’t appreciably go up such that finger touch notices.

[Phil_Fr17]

Hi,
Here is the link giving the explanation of the rise in temperature of the Gigavacs contactors. Found on their site.
https://www.sensata.com/sites/defaul...e-app-note.pdf


It seems they know about this sort of thing.
https://www.sensata.com/search?searc...+14+&op=Submit


But the fact that the temperature increases during operation does not necessarily mean that there is a defect or problem, simply that the coil is either oversized or not optimized.
Many contactors in electrical cabinets become hot or even very hot during use.


I have seen many installations made with Blue Sea equipment, therefore the ML-RBS, recognizable by their yellow control finger.
From there to affirm that it is good material, I do not know.

[PaulCrawhorn]

Cross reference for original topic

https://www.cruisersforum.com/forums...ml#post3699854

[s/v Jedi]

Originally Posted by Phil_Fr17

Hi,
Here is the link giving the explanation of the rise in temperature of the Gigavacs contactors. Found on their site.
https://www.sensata.com/sites/defaul...e-app-note.pdf


It seems they know about this sort of thing.
https://www.sensata.com/search?searc...+14+&op=Submit


But the fact that the temperature increases during operation does not necessarily mean that there is a defect or problem, simply that the coil is either oversized or not optimized.
Many contactors in electrical cabinets become hot or even very hot during use.


I have seen many installations made with Blue Sea equipment, therefore the ML-RBS, recognizable by their yellow control finger.
From there to affirm that it is good material, I do not know.

No, that is the other way around: this explains how the characteristics of the contactors change when the ambient temperature changes.

For example: using a lower coil voltage because “it works” may suddenly not work on a very hot day as the graphs show… because when it’s hot, a higher voltage is required.

Solenoids and contactors get hot for two reasons: coil inefficiency and contact resistance. When it gets hot without large currents flowing through the contactor, it is just the coil heating it up and this is what the OP describes. Depending on size of the units, a coil can use between 100mA to several amps just to hold the contact closed. Not all this energy is converted into magnetic field and this part ends up as heat. This heat builds up over time (it’s only a problem for continuous duty applications) until it finds a level where the same amount of heat is radiated out as that is added from the coil and hopefully this heat level isn’t too high. In that case the solenoid or contactor is rated as continuous duty.

Then there are optimizers that reduce coil current to keep the contact closed after switching. I think most continuous duty versions now have that. This reduces heat from the coil as well. Next step are latching versions, which require no coil current to hold the contact closed at all and thus are the most efficient. Of course price goes up as well. The 7718 is a plug-in replacement (https://www.bluesea.com/products/7718/Solenoid_ML_12V) and the mentioned 7713 adds a manual control knob to it.

[Phil_Fr17]

Whoops ! You're right s/v Jedi, I carefully reread the documents and the curves that I found odd.
My apologies, I have read too fast and diagonally.


Being in a rush and not fully fluent in a foreign language can lead to this kind of inversion. It has already happened to me several times to misunderstand what I was told in English, the English drive on the left, this is perhaps the explanation of my misunderstanding in a good way... ;-)