Nobodybusiness
Collecting the leftovers of the Great Sky Reactor.
Sounds like he doesn’t have a clue.
Very strange comment re AGM v Lifepo4
- Thread starter bds70
- Start date
pollenface
Solar Addict
Just smile and nod, and get what you need.
jerry wayne
New Member
Maybe the lead acid battery is too heavy and doesn't perform as well as lifepo4
HarryN
Solar Enthusiast
Either chemistry can work, it is a matter of understanding the limitations and benefits of each.
One of the challenges of LiFe batteries is that it is possible to trip the BMS on one in a parallel setup and not be able to re-set it unless there is a switch or breaker on each battery to cut it off from the others. With AGMs this just does not happen. So diagnosing a LiFe pack without this separation capability is a pain.
When starting up an inverter, there is a surge of power draw to charge up the capacitors. It is possible to trip the BMS of a LiFe battery unless the caps are pre-charged. With AGMs this is a non issue. With LiFe there really should be a pre-charge method.
Some RVs charge the house battery from the alternator by just having a direct connection via a relay. This is sort of ok for AGMs but with LiFe you really need a battery to battery charger to do it correctly and reliably. It really should be used for both scenarios, but with LiFe it really is needed.
People have a tendency to purchase cheap LiFe batteries vs good ones. Good ones have higher charge rates than cheap ones. Some AGM setups can charge at remarkably fast rates during some stages, so some of this depends if you are buying some cheap LiFe battery vs a really good quality one.
If your plan is to go "cheap", then I would instead also suggest the AGM would be more reliable. If your goal is to buy really good quality ones, then either can work.
Your solar charger may or may not be compatible with LiFe, if not then it might require changing it out.
In the US, there have been a lot of 12 volt exhaust fan failures. The companies that build them basically didn't build the control board with much voltage range so they were blaming LiFe batteries slightly higher voltage for this failure mode. I am not sure if that is real or not, but it is a common story in the industry. As a result, adding a voltage stablizer that feeds sensitive items like this is becoming increasingly common. I suspect that the actual problem is voltage spikes, but I am not sure.
Many state of charge meters that are on AGM battery systems work by measuring the voltage and translating this into a state of charge. This does not work with LiFe, you really need to use a true state of charge meter that measures power going in and out of the battery. It requires you to be able to understand it and really how it works - being able to read the manual vs not.
Most people will not read a manual or listen to instructions, so they end up calling the tech with a complaint of it all not working correctly, even though it is. This can come across as an unhappy customer and consumers time - which is a big deal on the thin margins that people work under.
AGMs have a significantly wider temperature use range, not just on the cold end, but also on the hot end. In a hot climate, inside of a vehicle, you can be really bumping up toward the top of that LiFe range.
So it would not be a complete surprise if he is seeing customers calling with LiFe issue scenarios, especially for first time customers who have not been willing to make the complete / optimum investment in dealing with the batteries properly. For him, those show up as warranty / labor effort that does not show up as customer complaints in an AGM setup.
So you kind of have to decide if you are someone who will actually read a manual and follow directions, vs a person who is not. Are you someone who is technically inclined and really understands volts, amps, watts, SOC or willing to learn - or not?
Are you willing to really buy a good quality battery or the cheapest import around?
Are you willing to put in the investment for proper charging and pack separation or not?
On the benefits side, IMHO, the big benefit of LiFe batteries is not the weight, it is the ability to run at partial charging vs needing regularly to be fully charged. It is the equivalent of a fuel tank needing to always be refilled to completely full regularly vs you can just run around with a partial tank and just add "some" vs a "fill".
These are the things that will matter for you in a tough environment like you are in for what battery chemistry is optimal.
One of the challenges of LiFe batteries is that it is possible to trip the BMS on one in a parallel setup and not be able to re-set it unless there is a switch or breaker on each battery to cut it off from the others. With AGMs this just does not happen. So diagnosing a LiFe pack without this separation capability is a pain.
When starting up an inverter, there is a surge of power draw to charge up the capacitors. It is possible to trip the BMS of a LiFe battery unless the caps are pre-charged. With AGMs this is a non issue. With LiFe there really should be a pre-charge method.
Some RVs charge the house battery from the alternator by just having a direct connection via a relay. This is sort of ok for AGMs but with LiFe you really need a battery to battery charger to do it correctly and reliably. It really should be used for both scenarios, but with LiFe it really is needed.
People have a tendency to purchase cheap LiFe batteries vs good ones. Good ones have higher charge rates than cheap ones. Some AGM setups can charge at remarkably fast rates during some stages, so some of this depends if you are buying some cheap LiFe battery vs a really good quality one.
If your plan is to go "cheap", then I would instead also suggest the AGM would be more reliable. If your goal is to buy really good quality ones, then either can work.
Your solar charger may or may not be compatible with LiFe, if not then it might require changing it out.
In the US, there have been a lot of 12 volt exhaust fan failures. The companies that build them basically didn't build the control board with much voltage range so they were blaming LiFe batteries slightly higher voltage for this failure mode. I am not sure if that is real or not, but it is a common story in the industry. As a result, adding a voltage stablizer that feeds sensitive items like this is becoming increasingly common. I suspect that the actual problem is voltage spikes, but I am not sure.
Many state of charge meters that are on AGM battery systems work by measuring the voltage and translating this into a state of charge. This does not work with LiFe, you really need to use a true state of charge meter that measures power going in and out of the battery. It requires you to be able to understand it and really how it works - being able to read the manual vs not.
Most people will not read a manual or listen to instructions, so they end up calling the tech with a complaint of it all not working correctly, even though it is. This can come across as an unhappy customer and consumers time - which is a big deal on the thin margins that people work under.
AGMs have a significantly wider temperature use range, not just on the cold end, but also on the hot end. In a hot climate, inside of a vehicle, you can be really bumping up toward the top of that LiFe range.
So it would not be a complete surprise if he is seeing customers calling with LiFe issue scenarios, especially for first time customers who have not been willing to make the complete / optimum investment in dealing with the batteries properly. For him, those show up as warranty / labor effort that does not show up as customer complaints in an AGM setup.
So you kind of have to decide if you are someone who will actually read a manual and follow directions, vs a person who is not. Are you someone who is technically inclined and really understands volts, amps, watts, SOC or willing to learn - or not?
Are you willing to really buy a good quality battery or the cheapest import around?
Are you willing to put in the investment for proper charging and pack separation or not?
On the benefits side, IMHO, the big benefit of LiFe batteries is not the weight, it is the ability to run at partial charging vs needing regularly to be fully charged. It is the equivalent of a fuel tank needing to always be refilled to completely full regularly vs you can just run around with a partial tank and just add "some" vs a "fill".
These are the things that will matter for you in a tough environment like you are in for what battery chemistry is optimal.
Last edited:
bds70
New Member
Some great information there. If you are going to put a breaker on each battery where and how would they mount, and if a BMS has tripped what is the process to wake it back up again.
I was running 8 AGM 250ah 6v in series then parallel. 6v have thicker plates and hold up better to traveling vibration. They were good but started to fail at 6 yrs or so. My situation is my bus is my 24/7 fully off grid home. So I switched to 340ah lifepo4 x 3. Saved a ton of weight and space.
I am going to fit a 12v extraction fan into the solar locker. It already has two large ventilation plates, but with outside temps hitting 37⁰C (100⁰F) the internal heat from the mppt''s inverters will be a lot higher. So I think a permanent extraction fan to draw the heat outside would be a good investment.
I am an avid researcher, I don't just want someone to supply and fit me something and show me the start stop button. I need to know how it works, why it works and how to take it apart and put it back together again. (Working) lol. Hence my number of questions I am now asking here on this excellent forum.
Thanks for taking the time to give me such a comprehensive answer.
McKravitts
Solar Enthusiast
- Joined
- Sep 8, 2022
- Messages
- 534
Like the incandesant light bulb there'll be people saying; "They'll have to pry my lead acid battery out of my cold dead hands."
HarryN
Solar Enthusiast
So for re-setting the BMS ( on many LiFe batteries ), the circuit needs to be able to individually isolate them on one side - for example the positive connection.
So a common method is to have parallel setups of
- ( battery positive ) --- ( breaker ) --- ( + bus bar ) for each battery in parallel
So for 3 batteries, you would need 3 breakers and attach it to a bus bar.
All of your larger loads would also attach to this bus bar so it will need to be healthy size.
An example breaker would be something like this but you could also use a switch if the only purpose is on / off. I like the dual capability of circuit protection and on / off.
187-Series - Blue Sea Systems
Thermal circuit breakers provide heavy duty circuit protection for 25 to 200 Amp loads when switching and circuit protection are both required.
www.bluesea.com
This is actually a good idea for both Li and AGM batteries IMHO because it makes maintenance so much safer and easier.
__________________
For smaller loads, such as a 12 volt fuse block can be connected the same way to the bus bar, for example
(+ fuse block ) ---- (breaker ) ---- ( + bus bar)
The reason for considering this is that those batteries can really pump out some amps, and a simple ATO fuse in a fuse block might not be capable of stopping it before damaging the fuse block vs the breaker can. It isn't absolutely mandatory, but a good practice.
___________________
With a circuit like this in place, the procedure to do maintenance of all types is to just go in and turn off the breaker for each battery and each source of charging. This will stop power from coming into the circuit.
If you turn on the inverter or any small load for even 10 seconds, it will discharge the capacitors on the input stage of the inverter and output stage of chargers. A volt meter will allow you to tell if it is really down to zero and safe to work on.
Some electricians will carry a small piece of wire and go around and short things out all over before touching anything as an additional precaution. Obviously they have had some experiences......
Meters can behave in weird ways if the batteries start to get low or if they have been dropped too many times.
________________________
As far as re-setting the BMS on a battery in parallel - it is actually slightly difficult to tell if it has tripped or not.
A modern volt meter has very high impedance, so it takes almost negligible amounts of current to register a voltage on a meter. There is a small leakage current though the FET of most Li battery BMS's to be enough to register essentially 12 volts, even if the BMS has tripped.
One way to tell is if you have a clamp meter, you can measure the current in each wire to tell if all of the batteries are in fact having power go in / out. It is a very useful diagnostic tool and anyone who is dependent on their power system like you are really should own one.
___________
Regardless of if you are sure that a BMS has tripped or not, peace of mind can be had by simply turning off the breaker of a battery for 10 seconds, and turning it back on. This can be done one at a time going down the row of batteries and now you can be almost certain that they are all operating.
___________
My wife is pretty competent, but it is a lot easier to convince her to flip off some breakers and turn them back on while talking on the phone than to walk her through getting out tools to disconnect wires and re-attach them.
Last edited:
HarryN
Solar Enthusiast
As far as the fan in the electrical area, what some people do is to add a thermal switch / sort of a thermostat that turns on at a specific temperature.
For instance if the air temperature inside of the compartment hits 35 C, it will turn on the fan. Similar in concept to a vehicle radiator electric fan. In the US we can buy them from for example digikey or mouser with pre-set temperatures built in. Of course there is some tolerance, it isn't a precision device.
This can always be added over time to the fan circuit.
For instance if the air temperature inside of the compartment hits 35 C, it will turn on the fan. Similar in concept to a vehicle radiator electric fan. In the US we can buy them from for example digikey or mouser with pre-set temperatures built in. Of course there is some tolerance, it isn't a precision device.
This can always be added over time to the fan circuit.
RV8R
Solar Enthusiast
bds70
New Member
Classic, your wife & mine must b related, dear things. Lol.So for re-setting the BMS ( on many LiFe batteries ), the circuit needs to be able to individually isolate them on one side - for example the positive connection.
So a common method is to have parallel setups of
- ( battery positive ) --- ( breaker ) --- ( + bus bar ) for each battery in parallel
So for 3 batteries, you would need 3 breakers and attach it to a bus bar.
All of your larger loads would also attach to this bus bar so it will need to be healthy size.
An example breaker would be something like this but you could also use a switch if the only purpose is on / off. I like the dual capability of circuit protection and on / off.
187-Series - Blue Sea Systems
Thermal circuit breakers provide heavy duty circuit protection for 25 to 200 Amp loads when switching and circuit protection are both required.
This is actually a good idea for both Li and AGM batteries IMHO because it makes maintenance so much safer and easier.
__________________
For smaller loads, such as a 12 volt fuse block can be connected the same way to the bus bar, for example
(+ fuse block ) ---- (breaker ) ---- ( + bus bar)
The reason for considering this is that those batteries can really pump out some amps, and a simple ATO fuse in a fuse block might not be capable of stopping it before damaging the fuse block vs the breaker can. It isn't absolutely mandatory, but a good practice.
___________________
With a circuit like this in place, the procedure to do maintenance of all types is to just go in and turn off the breaker for each battery and each source of charging. This will stop power from coming into the circuit.
If you turn on the inverter or any small load for even 10 seconds, it will discharge the capacitors on the input stage of the inverter and output stage of chargers. A volt meter will allow you to tell if it is really down to zero and safe to work on.
Some electricians will carry a small piece of wire and go around and short things out all over before touching anything as an additional precaution. Obviously they have had some experiences......
Meters can behave in weird ways if the batteries start to get low or if they have been dropped too many times.
________________________
As far as re-setting the BMS on a battery in parallel - it is actually slightly difficult to tell if it has tripped or not.
A modern volt meter has very high impedance, so it takes almost negligible amounts of current to register a voltage on a meter. There is a small leakage current though the FET of most Li battery BMS's to be enough to register essentially 12 volts, even if the BMS has tripped.
One way to tell is if you have a clamp meter, you can measure the current in each wire to tell if all of the batteries are in fact having power go in / out. It is a very useful diagnostic tool and anyone who is dependent on their power system like you are really should own one.
___________
Regardless of if you are sure that a BMS has tripped or not, peace of mind can be had by simply turning off the breaker of a battery for 10 seconds, and turning it back on. This can be done one at a time going down the row of batteries and now you can be almost certain that they are all operating.
___________
My wife is pretty competent, but it is a lot easier to convince her to flip off some breakers and turn them back on while talking on the phone than to walk her through getting out tools to disconnect wires and re-attach them.
I bought a clamp meter last week and already had a good quality ordinary one. I didn't know how to use it as you describe so I shall give it a go.
Things have moved on a bit with the company that supplied the batteries. I am now negotiating refunds on two of the batteries that are faulty. If successful I will start again and diy build a 48v system.
Thanks for the information, every little bit helps my overall education.
Have a great Christmas.
bds70
New Member
As I move forward with my plans I need to understand the pro's and con's of perhaps amalgamating the two seperate arrays I currently have.
So the 1st array is the one above - 2s3p 260W 20V -
The second array is 3s 400w Vmpp 34.2v
Is there a way to combine both outputs into one?
Is there an advantage to doing so? (I guess 1 MPPT rather than 2 maybe)
What are the disadvantages or maybe safety concerns?
TIA
So the 1st array is the one above - 2s3p 260W 20V -
The second array is 3s 400w Vmpp 34.2v
Is there a way to combine both outputs into one?
Is there an advantage to doing so? (I guess 1 MPPT rather than 2 maybe)
What are the disadvantages or maybe safety concerns?
TIA
To see how they will behave in different combination use the link in my signature for the Solar Panel Calculator.
SupraSPL
Solar Enthusiast
- Joined
- Aug 28, 2022
- Messages
- 222
I assume the salesman is talking about an occasional top balance and for those with a 240 volt inverter they need 240 volt grid access to charge.
A few nights I wanted to play around with top balancing a 24V lifepo4 system I used 40 volt Ryobi batteries hooked up to an extra MPPT to stay at 100% SOC while balancing the cells and of course you could do that with solar during the day if you don't mind a little lost power.
A few nights I wanted to play around with top balancing a 24V lifepo4 system I used 40 volt Ryobi batteries hooked up to an extra MPPT to stay at 100% SOC while balancing the cells and of course you could do that with solar during the day if you don't mind a little lost power.
bds70
New Member
If I have done the calculations correctly (Thanks Crowz) the calculator helped.
I think that the rear Array has the following numbers
6x 260w Solar Panels wired in a 2s3p configuration =1560W 80V & 19.5A
The front Array will have
3x 400w Solar Panels wired in a 3s1p configuration = 1200W 131V & 9.16A
Presuming I have got it right, what would the effect be of combining both outputs AFTER the RCD's into a single Pos/Neg cable?
What size all in one hybrid inverter would I need if I went that road or
What size MPPT if I go on that road.
All very confusing! ?
I think that the rear Array has the following numbers
6x 260w Solar Panels wired in a 2s3p configuration =1560W 80V & 19.5A
The front Array will have
3x 400w Solar Panels wired in a 3s1p configuration = 1200W 131V & 9.16A
Presuming I have got it right, what would the effect be of combining both outputs AFTER the RCD's into a single Pos/Neg cable?
What size all in one hybrid inverter would I need if I went that road or
What size MPPT if I go on that road.
All very confusing! ?
HarryN
Solar Enthusiast
If you want to combine two solar arrays before the solar charge controller, they will need to be at roughly the same Vmp.
If your two arrays have a large difference in Vmp like your post, then you will need to feed them into two separate solar charge controllers and purchase ones that can work in tandem, not just two random ones.
____________
The current rating of a solar charge controller is the output rating.
So for instance, if it says 150 / 30, then the absolute max voltage that it can have going in is 150 volts, and you don't want to ever see that number - ever. So the number to look at is the Voc number for this. The / 30 is the max amps it can output to your battery pack.
The Voc increases substantially when the panels are cold, so look for an on line calculator of the impact of temperature on the panel array voltage for the worst case low temperature conditions that you expect.
_________
If your battery pack is for instance 24 volts nominal, and the controller has an output max of 30 amps, then it is:
(battery pack voltage ) x ( solar charge controller output amps rating ) = array wattage capability
so
( nominal 24 volt ) x ( 30 amps ) ~ 720 watts array capability
bds70
New Member
So your saying that I couldn't combine the cables and feed one input into something like this? With a 48V 280A battery bank.
Or maybe get rid of the 260w array and buy new 400w same manufacturer panels and do another array? Then the Vmp's would be the same. Would that work with the AIO inverter I posted?
Attachments
HarryN
Solar Enthusiast
I don't have any experience with AIO units specifically, so I will leave that response to someone else.
In general correct, the incoming voltage needs to be roughly the same is all that matters.
Some people are very precise about this matching in order to get absolutely optimal results - but I am not that person. In mobile applications, you just have to use what fits and comes close enough.
Look through the data sheets for all of the items and make sure that things are within the operating specs.
On cloudy days, the Vmp and Voc can be easily 10 - 20% lower than the label rating, so keep this in mind when in the design.
Before you purchase 400 watt panels make sure that they will fit that you can really safely lift such a panel up on top of the RV. When I had my business, I limited the panel size to 26 x 60 inches for a variety of reasons, including safety and liability, but there are others on this forum who are big fans of such size panels.
HarryN
Solar Enthusiast
The forum has a section specific to mobile systems here in case that is helpful for your research.
diysolarforum.com
Vehicle Mounted Systems
RV's, Vans, Trucks and More! Typically 12v, and 100-1000w, but the limits are endless!
diysolarforum.com
bds70
New Member
I am with you re the lifting, the 3 I already have, I designed a lifting strap with spread hooks to catch the frame. Then quickly grabbed the frame and tipped it onto the roof. Worked quiet well with no damage to frame or panel.
There are so many ideas and options flying around in my head right now. It's going to take a while more to reach some conclusions. But I really appreciate the knowledge and the assistance.
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