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Old 01-19-2015, 08:27 PM   #43
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i have been following this thread and learned a lot but still at the middle of the learning curve. up to now, i have 1440w solar panels and a midnite classic 150. i am thinking to get a 100ah or 200ah lfp batts to test the water (later to expand to 400-600). a set of balance boards and powerlog 6s could get me going. a big hurdle is the charging function from genset and chassis alternator. my existing charger/inverter is an heart interface freedom 20D, apparently it's not designed for lfp. getting a magnum or victron will be a big pinch on the skin. i am thinking of letting solar controller do the job - connect genset/alternator charging lines (with a throttled amps - will lose some amps but that is ok) to midnite controller input directly. am i stepping out of boundary? any thoughts?
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Old 01-20-2015, 09:34 AM   #44
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i have been following this thread and learned a lot but still at the middle of the learning curve. up to now, i have 1440w solar panels and a midnite classic 150. i am thinking to get a 100ah or 200ah lfp batts to test the water (later to expand to 400-600). a set of balance boards and powerlog 6s could get me going. a big hurdle is the charging function from genset and chassis alternator. my existing charger/inverter is an heart interface freedom 20D, apparently it's not designed for lfp. getting a magnum or victron will be a big pinch on the skin. i am thinking of letting solar controller do the job - connect genset/alternator charging lines (with a throttled amps - will lose some amps but that is ok) to midnite controller input directly. am i stepping out of boundary? any thoughts?
Hi CountryFit,

Your PV solar system will be great for your future with Li-ion batteries. [moderator edit] We use the Midnight Classic controllers often as it allows us to install up to 1400 Watts on a single controller. The only problem with Midnite and ALL charge controller is the voltage regulation is not very tight. You will have to tweak some to get the right float voltage. A 0.2 volt variance can make the difference between a full battery or one that is 60% full.

Because of very low internal resistance, Lithium batteries always charge in the Bulk stage until they are full, no absorption (CV, constant voltage) time is necessary unless you were charging at a very high rate, like 1C or higher. If you stay connected to shore power, your Heart inverter/charger will be a problem because it forces a 2 hour absorption charge time. For most lithium batteries this is not acceptable because charge voltage must be stopped or lowered for all Lithium batteries once they are full. You could turn off the breaker to the inverter while on shore power and the charger will be off. You will need to use the inverter for any connected loads which means discharging the battery. A new inverter/charger with CC/CV settings can solve this by terminating the charge cycle once you hit absorption.

While driving your alternator could be a problem after the battery is full. Some alternator voltage regulators can be adjusted. If you can reduce it to 13.8 volts, coupled with line and connection losses, you might have 13.6 volts at the battery. This is generally acceptable but check with the battery manufacturer. I have designed a few systems where you can simply turn off the alternator feed to the house battery. By monitoring the battery, you can choose to charge or not from a switch on the dash.

I have heard of people using a PWM charge controller to regulate voltage from an alternator if that is what you are saying. I have not needed to do this but I have not heard that it presents any problem. I would not use the Midnite or any MPPT controller for this.

Happy Trails,

Larry
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Old 01-20-2015, 03:30 PM   #45
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Hi CountryFit,

Your PV solar system will be great for your future with Li-ion batteries. I began installing LFMP batteries for our customers about a year ago including my own RV. We use the Midnight Classic controllers often as it allows us to install up to 1400 Watts on a single controller. The only problem with Midnite and ALL charge controller is the voltage regulation is not very tight. You will have to tweak some to get the right float voltage. A 0.2 volt variance can make the difference between a full battery or one that is 60% full.

Because of very low internal resistance, Lithium batteries always charge in the Bulk stage until they are full, no absorption (CV, constant voltage) time is necessary unless you were charging at a very high rate, like 1C or higher. If you stay connected to shore power, your Heart inverter/charger will be a problem because it forces a 2 hour absorption charge time. For most lithium batteries this is not acceptable because charge voltage must be stopped or lowered for all Lithium batteries once they are full. You could turn off the breaker to the inverter while on shore power and the charger will be off. You will need to use the inverter for any connected loads which means discharging the battery. A new inverter/charger with CC/CV settings can solve this by terminating the charge cycle once you hit absorption.

While driving your alternator could be a problem after the battery is full. Some alternator voltage regulators can be adjusted. If you can reduce it to 13.8 volts, coupled with line and connection losses, you might have 13.6 volts at the battery. This is generally acceptable but check with the battery manufacturer. I have designed a few systems where you can simply turn off the alternator feed to the house battery. By monitoring the battery, you can choose to charge or not from a switch on the dash.

I have heard of people using a PWM charge controller to regulate voltage from an alternator if that is what you are saying. I have not needed to do this but I have not heard that it presents any problem. I would not use the Midnite or any MPPT controller for this.

Happy Trails,

Larry
this is awesome larry. you cleared the cloud in my mind whether the controller could be used as a regulator. although i thought it over and over trying to find a most economical way to get where i wanted to be, never been certain. the idea of using a separate pwm controller to regulate the charging current is cool, especially some controllers can handle very high amps (for example svm 150 pwm controller can handle 150a for a 12v system) that would certainly make the charging process without loss of current and easy. with this approach, no matter if the rig is on shore, running on the road or genset is kicking, the charging lines will feed the pwm controller and the controller in turn, based on the battery condition, determines bulk or float. the function of freedom 20d inverting will not be compromised (i will see if i need to install a few high amp diodes).
to protect the battery from over drawn, i don't think it needs to demand the genset to start as some suggested, for freedom 20d doesn't have the function. i would just use a battery disconnect relay to turn it off when the voltage drops to close to 20%. i think that will work.

i feel more confident on this now than ever before. i love this board...
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Old 01-21-2015, 10:57 AM   #46
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this is awesome larry. you cleared the cloud in my mind whether the controller could be used as a regulator.....

...with this approach, no matter if the rig is on shore, running on the road or genset is kicking, the charging lines will feed the pwm controller....
While a PV solar charge controller might work for lowering the alternator voltage to your house battery, it should not be installed as you describe.

You can't connect your Freedom 20 inverter through a regulator. It must stay connected to the battery to work. If you install Lithium batteries, you must make sure the Freedom 20 charger is turned off or replace the inverter with one that can be programmed for CC/CV charge profile.

Larry
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Old 01-21-2015, 11:24 AM   #47
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While a PV solar charge controller might work for lowering the alternator voltage to your house battery, it should not be installed as you describe.

You can't connect your Freedom 20 inverter through a regulator. It must stay connected to the battery to work. If you install Lithium batteries, you must make sure the Freedom 20 charger is turned off or replace the inverter with one that can be programmed for CC/CV charge profile.

Larry
larry, my intention was to install a pwm between freedom 20 and the house battery. think about it this way - when on shore/genset/alternator, the electricity will go to freedom 20 first which will massage it into 12-14vdc to feed batteries. when a lithium battery pack is installed, it's critical to have a way to control such electricity to fit lithium battery acceptable parameters (bulk/float/cutoff/reconnect), that was what i meant to let the pwm take care of it. a separate solar controller midnite classic 150 will be connected to the lithium battery directly for just solar charge purpose. do you see anything missing or flawed?
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Old 01-22-2015, 01:05 PM   #48
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larry, my intention was to install a pwm between freedom 20 and the house battery. think about it this way - when on shore/genset/alternator, the electricity will go to freedom 20 first which will massage it into 12-14vdc to feed batteries. when a lithium battery pack is installed, it's critical to have a way to control such electricity to fit lithium battery acceptable parameters (bulk/float/cutoff/reconnect), that was what i meant to let the pwm take care of it. a separate solar controller midnite classic 150 will be connected to the lithium battery directly for just solar charge purpose. do you see anything missing or flawed?
Yes, flawed. You can not connect your Freedom inverter to a PWM charge controller because the inverter will not be powered from the battery and won't charge or invert. Battery power is necessary for the Freedom to function.

If you install Li-ion batteries and don't upgrade your Freedom 20, you could manually control the charger but that is risky. You could also install a voltage controller like the Magnum Energy SBC and a solenoid to disconnect the battery at a preset high and low voltage. This a a crude way to stop the absorption charge.

Larry
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Old 01-22-2015, 07:42 PM   #49
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Yes, flawed. You can not connect your Freedom inverter to a PWM charge controller because the inverter will not be powered from the battery and won't charge or invert. Battery power is necessary for the Freedom to function.

If you install Li-ion batteries and don't upgrade your Freedom 20, you could manually control the charger but that is risky. You could also install a voltage controller like the Magnum Energy SBC and a solenoid to disconnect the battery at a preset high and low voltage. This a a crude way to stop the absorption charge.

Larry
well taken larry, thanks again. I made a flow chart to describe what i plan to do. two diodes do make the freedom get power from lithium bank. i could be wrong but i would like to try it out with minimum risk.

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Old 01-23-2015, 11:11 AM   #50
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well taken larry, thanks again. I made a flow chart to describe what i plan to do. two diodes do make the freedom get power from lithium bank. i could be wrong but i would like to try it out with minimum risk.
It sounds like you are set on experimentation. The Freedom 20 is capable of conducting over 200 amps DC. Just be carefull working with such high currents.

Your alternator does no connect to your Freedom inverter as you have drawn.
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Old 01-23-2015, 01:25 PM   #51
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Lithium batteries

I hope you realize that with all that effort to modify a normal battery system, you are going to lose the first .6 to .7 volts off your battery bank when it flows though that high power silicon blocking diode. And same issue going in the other direction from your charging system. Personally, I'd like every tenth of a volt my battery stores to be available to my RV systems.
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Old 01-23-2015, 01:37 PM   #52
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It sounds like you are set on experimentation. The Freedom 20 is capable of conducting over 200 amps DC. Just be carefull working with such high currents.

Your alternator does no connect to your Freedom inverter as you have drawn.
on my lead-acid batteries, there are 3 (size 2/0) cables being connected to battery positive terminals, so are negative. i am not sure if both alternator and genset are by-passing freedom20. i will find out from schema and also measure the current for each lead while (1) only engine runs; (2) only genset runs, just to be sure. i will be surely careful with their huge currents.
for the pwm, this is the one i am planning to get. it handles up to 400a HVM Charge Controller 440 Amp 10 00 Watt 12 24 or 48 Volt for Wind Turbine P | eBay. a concern is how much the highest current the lfp battery can accept without damage to it. will see...
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Old 01-24-2015, 11:05 AM   #53
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on my lead-acid batteries, there are 3 (size 2/0) cables being connected to battery positive terminals, so are negative. i am not sure if both alternator and genset are by-passing freedom20. i will find out from schema and also measure the current for each lead while (1) only engine runs; (2) only genset runs, just to be sure. i will be surely careful with their huge currents.
for the pwm, this is the one i am planning to get. it handles up to 400a HVM Charge Controller 440 Amp 10 00 Watt 12 24 or 48 Volt for Wind Turbine P | eBay. a concern is how much the highest current the lfp battery can accept without damage to it. will see...
I get it ...you must prove things to yourself instead of learning from others. That's an expensive way to learn.

Li-ion charge current
Each Li-ion battery manufacturer specifies the maximum charge current for their battery. Many spec 3C or three times the 20 hour discharge capacity rating. This limit was set so the battery can be recharged in a reasonable amount of time for motive applications where low capacity, high voltage strings are used. For a 12 volt battery, for example a 100AH GBS battery (LFMP), can be charged at 300 amps. A 300AH bank can accept 900 amps. I don't know of any RV power system that can approach this charge ratio.

Recently some manufacturers have reduced their maximum charge current to 1C. I believe this was done to reduce the effect of heat and increase cycle life.

Larry
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Old 01-24-2015, 05:32 PM   #54
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i have been following this thread and learned a lot but still at the middle of the learning curve. up to now, i have 1440w solar panels and a midnite classic 150. i am thinking to get a 100ah or 200ah lfp batts to test the water (later to expand to 400-600). a set of balance boards and powerlog 6s could get me going. a big hurdle is the charging function from genset and chassis alternator. my existing charger/inverter is an heart interface freedom 20D, apparently it's not designed for lfp. getting a magnum or victron will be a big pinch on the skin. i am thinking of letting solar controller do the job - connect genset/alternator charging lines (with a throttled amps - will lose some amps but that is ok) to midnite controller input directly. am i stepping out of boundary? any thoughts?
You've received a lot of good advice from this forum, but one thing is troubling me. I'm not sure why you believe you need a diversion load controller to cut off the charge along with the diodes. Looking at the Freedom 20 manual page 36 (this is the old manual but the newer ones are the same), what they call acceptance (regulating at the bulk charge voltage) is based on current flow, with acceptance being cut off at a current of about 6-7A. At that time, per the manual, the charger is turned off until the battery voltage goes below the float level, at which time it turns on and maintains float voltage.

Absorption time is a maximum of two hours, with no minimum stated in the manual. The Freedom 25 I used in my previous coach worked this way, staying in Absorption for about an hour while the current decreased to the 6A level, then went to float.

The cutoff current of 6-7A is the key. A noted expert on LFP charging, Jack Rickard of evtv.me, has written that the preferred charging algorithm for LFP will charge at full current until the battery voltage reaches the desired (bulk) voltage level, then maintain the bulk charge voltage and reduce the current gradually, until the current reaches about 5-10% of the battery's amp/hour rating, then cut off. 6-7A is right in the ballpark for the 100AH to 200AH pack you're thinking about.

In this article he mentions that his preferred charge voltage is 3.55V, or 14.2V for 4 cells in series. Freedom 20 offers 14.1V or 14.3V, I'd try both and see which gives you the best results. The Powerlog 6S has a logging function which will allow you to see how well your Freedom 20 is regulating, I would closely monitor this while you are selecting the charge setting. I use 14.2V bulk charge level.

I use a similar product, a Celllog 8S, to monitor my 400AH LFP battery. I do not use balance boards, I top balanced the cells during installation and rebalance them manually when the cell voltage difference goes over about 75mV during the last part of the charge cycle (easy to see with the Celllog/Powerlog). I've had to rebalance once in the four years I've owned the LFP battery pack.

LFP cell balancing, top balancing, bottom balancing, whether to install balancers, etc, is anther can or worms with vocal adherents on every side. Jack Rickard is vocally opposed to top balancing, installing balancers and even somewhat against installing per-cell monitoring.

In my case top balancing and having monitors makes the most sense to me, given my particular situation. My RV batteries spend a lot of time floating at full charge as we have the coach plugged in most of the time. It almost never gets below 80% discharge. This spring (2014) I purposely discharged the cells and bottom balanced them as Jack suggested. When I charged them back up, as they were approaching 100% one of the cells got too high (close to 3.8V) and I had to terminate charge early. After top balancing them I could fully charge them without worrying one may get too high. In this case, I believe call monitoring kept me from ruining a cell. I still don't like any of the cell balancers that I've seen out there, they all apply a passive load only when charging, they do not try to actively keep the cell voltages the same while discharging. TI makes a chipset that does this, but I haven't bothered getting one and making my own.

As far as charge current is concerned, if you get 200AH worth of LFP's the 100A Freedom 20D charger current will be much lower than the 1C the more conservative LFP manufacturers are specifying now. With 100AH you'll be right at the spec.

IMHO The float voltage is much less important than the bulk/absorption charge voltage, so you can get away with either 13.4V or 13.8V that the wet cell and gel cell offer. I use 13.8V float charge level and have had no issues with overcharging at that float level.

Admittedly, there are better inverter/chargers that can be used (I use an ancient Trace SW2512, but it is fully programmable and is well-suited for LFP batteries). If I had to choose a new one I'd get the Magnum suggested by other posters. But my opinion (FWIW) is that you won't destroy your battery or cause a fire by using your current inverter/charger connected directly to the LFP battery pack.

As far as genset/alternator lines, I have no experience with gensets that charge their own batteries, My Onan HGJAB does not charge it's starting battery. My alternator, however, is connected directly to the battery as before and I have had no issue with it. It only puts out about 14.1V max, and that goes down to 13.8 within about 5 minutes of starting, so it does not have the capability of overcharging the LFP battery pack. If I were you, I'd check the output voltage of your alternator, if it is below 14V after the engine has run a while I'd leave the present connection. I' you're worried about it I'd add some kind of switch to turn off the battery isolator relay almost all coaches have.

Also, I do not run the inverter/charger with a temperature sensor. LFP's have a much different temperature curve than lead acid and there's no way to make the temp sensor circuit in the Trace inverter match it.

LFP's don't take kindly to over-discharging and I actually would be more worried about discharge than charging with the Freedom 20D inverter. The low voltage cutoff of 10V of the Freedom series is too low, IMHO. I never let my cells get below 2.8V per cell (11.2V) and normally keep them above 3V per cell (12V). The Powerlog has an alarm for when the pack voltage or each cell voltage get's too low, I'd highly recommend setting them both.

You could bottom balance your batteries and limit the charge voltage by choosing the 12V wet cell warm temp charge setting which will charge to 13.9V. This should keep the scenario that happened to me from happening to you with bottom balanced batteries. You can read more about bottom balancing on Jack's website, he sells a reasonably priced tool which will help you bottom balance manually.

I would also highly recommend getting a Link 1000 or similar control for your inverter so you can keep track of exactly how much energy remains in your battery. This way you can discharge to, say, no more than 80% and avoid the issues in the previous paragraph. The Link 1000 is probably not available any more but can probably be picked up on eBay fairly cheaply. I suggest this one because it doubles as a remote control for your Freedom inverter. The Link 1000 has a neat Time Remaining indicator which I miss in my present battery monitor, tells you the time you have left running on battery. It's just a guess based on past usage, but it will help you plan your usage.

Please take this advice as I intended, I do not install systems professionally so do not have lots of experience with badly designed and installed systems, I have experience with only my system which I designed and built. It's now almost four years old now and I suspect I must be doing something right, during the bottom balancing exercise I mentioned above I was astounded when my battery monitor indicated I had over 430AH capacity in a nominal 400AH battery pack!
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Old 01-24-2015, 08:33 PM   #55
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stewart, big thanks for the lengthy and complete explanation!! i talked with the 440a controller maker today, he wasn't sure his would work in connecting to lithium, so your message is right in time that clears out the uncertainty on that part.

i have a copy of freedom 20 manual. by comparing the file in your link and the one i have, yours is even newer!! in older version it didn't mention the 6-7a thing, so now i know it cuts off when amp drops to 6-7a or 1 hour is reached whichever comes first (i remember another user technomad wrote in his doc he couldn't make the absorption shorter than 1 hour on his victron). i will try both 14.1 and 14.3v aborption to see which gets a better result.

the fact that you have been using your system for 4 years without problems, that is truly encouraging. i will follow your suggestions to check alternator (and generator) charging voltage. i do have an xantrex monitoring panel which has all the good info but i have yet to dig into it. i will do.

it's very nice receiving so much info. i really appreciate it. i will update after get all parts and start rolling.
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Old 01-25-2015, 03:03 PM   #56
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...... But my opinion (FWIW) is that you won't destroy your battery or cause a fire by using your current inverter/charger connected directly to the LFP battery pack.
Hi Stewart,

Thanks for sharing your LI battery experience.

The concern I have in using the Freedom 20 is if there are loads on in the RV, the current could stay above the 6-7 amp transition current for the entire time. This means it will hold the acceptance voltage for up to 1 hour or 3 hours for GEL setting.

Here's why this could be a problem: The first cell in a series string to reach 100% SoC will start to rise quickly in voltage as the other cells continue to accept current. This could be bad for that cell as lithium plating can occur or worse, a thermal reaction leading to very high internal temperatures. This could be bad!

The LI battery systems (GBS) [moderator edit] have a per cell sense boards for voltage and temperature, top balancing per cell shunts, a system shunt for current monitoring and coulomb counting (BMS) and 2 high current protective relays. When properly installed, this system offers 100% protection. The EMS CPU is programmed for a maximum cell voltage of 3.8 volts (15.2). Two [moderator edit] have experienced over-voltage shutdown issue in systems that we have installed. Both times it was the alternator had risen to 14.4 volts. Both customers had the over-voltage protective relay turn off the charge current because one cell was reaching 3.8 volts even though the bank voltage was only 14.4. I later tested this on the bench and verified that a CV above 14 volts can cause over 4 volts on a full cell if sustained.

I am very familiar with Jacks Rickards concept, and to date, success with bottom balancing and limited charging to retain the bottom equilibrium. This usually works fine for an electric vehicle. An EV owner will use the battery, plug in and charge continuously until the charger shuts off, then use the battery again.

This won't work in the RV world because an RV battery is in constant flux from multiple charge sources and loads. This complicates caring for LI batteries in the RV environment.

I do not recommend using any charger, Freedom 20 included, for Li-ion batteries that can sustain high voltage after any one cell is full. Since there is no reason to fully charge any Lithium battery bank, in fact, some data shows that this will shorten cycle life, it is best to stop charging or reduce to an acceptable float voltage, when the bank voltage reaches that specified by the battery manufacturer using a CC/CV protocol.

Larry
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