upgrading to Lithium batteries

[ekgflashnet]

Hello All,

Now that prices are looking more attractive, I'm looking to upgrade my current 6 - 6 volt AGM batteries (600AH, 300AH usuable) with two 200AH Lithium battery.  I have a few questions for the group just to confirm my plans are reasonable.

1.  Looking around, I found this 400AH lithium battery for what looks like a very decent price.  This battery has built-in BMS, bluetooth interface for looking at the status of the batteries and cells, it also includes a built-in heating for cold weather operation.  Total price is $1460 on Amazon.  This would be equivalent to 8 -6v batteries or about $180/6v battery.  Any comments/issues I should look at before purchasing something like this?  

2.  To protect the alternator, I'm planning to install a dc-dc charger after the BIRD on the house terminal side and before the house batteries.  I believe this will minimize any wiring changes, keep the BIRD in tact (although I've read some don't like the BIRD solution), and protect the alternator from running too hot.  There appears to be two basic types of dc-dc chargers.  Isolated and non-isolated ones.  non-isolated are less expensive.  I'm not sure I see the value of an isolated one since the ground comes from the frame and no real reason to isolate the ground from the input and output of the dc-charger.  However, the ones I've seen that are rated at larger amps seem to be isolated chargers.  here's the one I'm considering (60Amp, $188).    opinions/feedback.  This appears to be an isolated dc-dc charger.  Seems like both the input ground and output ground would simply be connected to the frame ground source or ground wire.

3.  I'm thinking of putting into place a smart shunt.  With the smart shunt, I can then monitor usage and draws from the app on my cell phone.  Seems like a better solution than what's currently in place.  For this, I'm looking at the Victron bmv-712 smart shunt ($206). This includes the shunt and a wired monitor.  I'm wondering of the value of the package offering over just getting the smart shunt and using the bluetooth connection with the app to view all your current parameters.

Total cost for these items is in the $1900 range.

thanks for your feedback/suggestions/opinions.

steveg 2005 DDIV

 

[timaz996]

I replaced my AGMs with two 200ah lithium Lossigy batteries as I already have the BMV-712, and a Victron 3000w multiplus inverter and it all works great. I didn't have room in my bay to fit the Multiplus II our I would have gone that route. my Lossigy 200ah batteries cost 659 each...669 on Amazon. Look up Will Prowse on YouTube, he takes them apart and shows you how all of the different lithium batteries are built and rates them. Mine don't have blue tooth but with the BMV-712 I don't need it. A friend just put in two 400ah Lossigy batteries in his bay because the 200ah battery you are looking at is the same size as his 400ah batteries, that cost him 3000 for his two.

I would call your thoughts a good way to go.

Tim  

Edited April 24, 2022 by Tim-AZ

[vito.a]

I've also been considering the switch to LiFePO4 batteries.  I agree with Tim,  I've been watching the Will Prowse video's on YouTube.  You can build your own batteries for less than half the cost of buying one already complete.  And you can upgrade the components to make a much better battery pack.  

The downside to LiFePO4 batteries is the temperature sensitivity.  They do not like temperatures above 90 or below 32.   You can install a 12v heater for cold temperatures, but it's much more difficult to keep the battery compartment cool.  During the summer here, it's not unusual to see our battery compartment above 125 degrees Fahrenheit as it's right next to the engine compartment.  

[JDCrow]

Looking over your stuff, what is your coach inverter/charger? 
 

It will need be rated to charge lithium. 
 

Here is the battery in my coach 

Smart 12V 200AH LiFePO4 Battery | Bluetooth Lithium Battery | Support Low Temperature Charging (-31°F) | Built-in 100A BMS | Mobile Phone APP Monitors Battery SOC Data https://www.amazon.com/dp/B09SX4CGFV/ref=cm_sw_r_cp_api_i_F6415RNJZF18ZN42F0C9?psc=1

 

Max charge temp is 118

max discharge temp is 136

I have Victron Multiplus 2 and Victron 30am Dc/Dc charger, tossed The bird

Edited April 21, 2022 by JDCrow

[timaz996]

If he has a Magnum pure sign he can set the voltages to match the lithium batteries. AZ wind and sun did a test and said it did fine. On another note. I tested my coach charging the lithium batteries with the alternator when they were down at 80% of 400ah. They only pulled 97 amps peek (I have a 200 amp alternator) so I didn't install a DC/DC charge controller. I will keep an eye on it as time goes on. I also have my engine lid spaced out about 7" so the engine bay stays a lot cooler then most. I full time so I'm never in the AZ heat. Most lithium BMS have a high temp cutoff at 76c or 167F.

Tim 

Edited April 24, 2022 by Tim-AZ

[JDCrow]

6 minutes ago, Tim-AZ said:

If he has a Magnum pure sign he can set the voltages to match the lithium batteries. AZ wind and sun did a test and said it did fine. On another note. I tested my coach charging the lithium batteries with the alternator when they were down at 80% of 400ah. They only pulled 97 amps peek (I have a 200 amp alternator) so I didn't install a DC/DC charge controller. I will keep an eye on it as time goes on. I also have my engine lid spaced out about 7" so the engine bay stays a lot cooler then most. I full time so I'm never in the AZ heat. Most lithium BMS have a high temp cutoff at 79c or 174F.

Tim 

Look for the Victron YouTube video where they smoke alternators. Pretty cool 

[timaz996]

41 minutes ago, JDCrow said:

Look for the Victron YouTube video where they smoke alternators. Pretty cool 

I have seen it. That's why I did the test with my alternator. What I love about these batteries is they will take full amperage all the way to 99% SOC. So they charge in less then a 1/4 of the time my AGMs took. Here is the gap on my engine lid. Everything stays much cooler in my engine compartment.

Tim

Edited April 21, 2022 by Tim-AZ

[TOBYLB4]

56 minutes ago, Tim-AZ said:

If he has a Magnum pure sign he can set the voltages to match the lithium batteries. AZ wind and sun did a test and said it did fine. On another note. I tested my coach charging the lithium batteries with the alternator when they were down at 80% of 400ah. They only pulled 97 amps peek (I have a 200 amp alternator) so I didn't install a DC/DC charge controller. I will keep an eye on it as time goes on. I also have my engine lid spaced out about 7" so the engine bay stays a lot cooler then most. I full time so I'm never in the AZ heat. Most lithium BMS have a high temp cutoff at 79c or 174F.

Tim 

Tim, I'm interested in how you spaced the engine lid out 7"s. I'm trying to find a way to exhaust the heat from my engine bay. Do you have pictures of what you did?

[Paul J A]

16 minutes ago, TOBYLB4 said:

Tim, I'm interested in how you spaced the engine lid out 7"s. I'm trying to find a way to exhaust the heat from my engine bay. Do you have pictures of what you did?

R

That engine compartment grill is something Ricki Mackin posted on F B. He used to run the paint shop at Monaco in Or.  

Owner-operator at Mackin Street Customs & RV's Inc.

[timaz996]

My brother made me some brackets that work great and the engine lid doesn't move at all driving. See pictures. As you can see they attach to the linkage of the engine lid.

Tim

Edited April 24, 2022 by Tim-AZ

[CAT Stephen]

Ekgflashnet,

The Renogy DC-DC charger is a good product at this low pricepoint.  Take care not to mount this DC to DC charger  in the battery compartment because it is not ignition protected which means an explosion in the presence of gassing from your SLA or FLA starting batteries.  There are ignition protected DC to DC chargers in available, but the pricepoint of the ignition protected DC to DC charger options are above $500.00

The battery specifications fit your application well, but you should avoid LiPO4 batteries that have not been extensively reviewed through full teardown and capacity testing by third party sources.  These Chineese LiPO4 batteries, like the one you referenced in your post, appear on Amazon & eBay for a short time then disappear after a few months rendering your battery warranty useless.  The exception in the 12V LiPO4 world is SOC, AO Lithium, Chins, and Battleborn which are tremendously rugged LiPO4 batteries from established long term companies that have excellent build quality, strong performance, very impressive warranties, with extensive testing and tear down by some great volunteer experts.  As Vito.a mentioned in a post above, Will Prowse is the primary volunteer in the industry that has the performed the most thorough reviews.  Before buying any LiPO4 battery, review Will's battery teardown and testing here: https://www.youtube.com/c/WillProwse/videos

I recommend SOC & AO Lithium above all other battery manufactures for your application.  SOC has a slightly better warranty and slightly lower cost per amp-hour than the AO Lithium, but has no built in shunt.  AO Lithium has a built-in shunt negating the need for you to purchase an external shunt from Victron and others.  Also, AO Lithium has the best thermal performance under heavy discharge which is rated at 1C discharge continuously, 2C discharge for 3 minutes, and 3C discharge for 30 seconds.  So, in your application with a 2500W Magnum inverter and four (4) 100Ah-Hr AO Lithium Batteries in parallel , you could run your inverter at 2500W full output (which is 2750W drawn from the battery due to inverter efficiency loss) resulting in 229Amp continuous load with no concern for thermal overload as your AO Lithium bank will be running at 0.57C which means minimizing overall life degradation because of low thermal stress.  

[ekgflashnet]

I have a freedom pure sine wave inverter which can be configured for lithium batteries.  Also, my house batteries are in a separate compartment from my engine batteries.  Therefore, there is no outgassing issue in my case since my starting batteries (FLA) are not near my house batteries.  One of the items that caught my attention on the batteries I was looking at was the internal heating element which is enabled when charging in colder weather.  During such an event, the charge to the batteries are used to first heat up the battery.  Once the battery temperature is above the required operating temperature, then the the charge is directed to the battery cells.

steveg 2005 DDIV

[TOBYLB4]

9 hours ago, Tim-AZ said:

My brother made me some brackets that work great and the engine lid doesn't move at all driving. See pictures. As you can see the attach to the linkage of the engine lid.

Tim

Thanks Tim

[wamcneil]

16 hours ago, Tim-AZ said:

... Look up Will Prouse on YouTube, he takes them apart and shows you how all of the different lithium batteries are built and rates them. ...

Tim  

X2. Personally if I were buying preassembled batteries on a budget, I would stick with something where I can see the teardown video and some objective technical reviews.

Building a quality battery is more complicated than just connecting some cells and dropping them into a case. Trusted manufacturers like battleborn spend a lot of time and effort engineering the batteries to last, exactly balancing/matching the cells and carefully constructing the batteries. And they get paid for all that work. 

Maybe those Himassi batteries you linked are fabulous batteries... but the reviews seem to mostly cover their little 6ah battery that the reviewers didn't fork out their own money to purchase. And the "EE-BMS" app has four apple appstore reviews, three of which are one-star.

IMO, the phrases 'you get what you pay for' and 'sounds too good to be true' are especially relevant when dealing with Chinese suppliers. 

Cheers,

Walter

[Rocketman3]

 

One area you need to be careful (and think through and test) is how many amps the bms can pass through. The bms is the most important part of the lithium battery and many times one of the cheapest parts. Some/many FET based bms’s can only pass 100 amps per battery (some are 150amps. Many people on Wil’s site like to derate the Chinese bms by 70% (never use more than 70% of the bms value).
 

Considering 100amps throughput- with two batteries- you can only use 200 amps. That will be marginal to run the microwave/ convention oven on the inverter. (Three batteries would be just fine).

 Does your generator use the chassis battery or the house battery?  If the house battery you need to know the amps needed to start the generator and the surge amps needed -so you don’t trip the bms. (Use a clamp meter to get the starting amps).

Using the cheap bms’s the boost abilities of the MotorHome will be changed. Because the two batteries can only deliver 200 amps (maybe 400 amps for 10 seconds), that’s not enough to start the big diesel motor. You will need to transfer more power to the starting batteries before kicking on the starter. This is one area you probably need to think about. 
 

As far as other equipment - definitely put in the Victron BMV712 or the Victron Smartshunt (I have used both).  I feel this is the most important part of my system. The only difference is the 712 has the remote display (which I never really used), it has a relay, and the Bluetooth has a longer (more normal) range and is about $50-$70 more. The Smartshunt’s Bluetooth range is about 8 to 10 feet.  

The DC-Dc converter- you want the non-isolated one. The isolated one is for vehicles like a truck and pull trailer - where the grounds may be separated. The one downside is it will only charge at 30amps. So after four hours of driving - if your batteries started out low - they would not be full when you arrived. 
 

if you want to read my write up on my lithium project (I self-built my own batteries - but much of the other logic is important). I did a write up on Wil’s site. https://diysolarforum.com/threads/batrium-watchmon-install.17539/
 

Good luck!

Edited April 22, 2022 by Rocketman3
Fix typos

[Ivylog]

“lithium-ion batteries can be charged from 32°F to 113°F and discharged from –4°F to 140°F” not 90 degrees as previously posted.

Instead of a DD to DC I’m going to try switching the alternator on-off on a yet to be determined cycle… $7 programmable remotely controlled switch. 

[TOBYLB4]

On 4/21/2022 at 6:37 PM, Paul A. said:

R

That engine compartment grill is something Ricki Mackin posted on F B. He used to run the paint shop at Monaco in Or.  

Owner-operator at Mackin Street Customs & RV's Inc.

Thanks Paul, I've seen this just not sure I want to cut on my door. Also it's a little pricey.

[waterskier_1]

Rocketman3 has brought up some great points.  I’ll add or amplify on some that I think need to be considered.

First, I don’t like the “huge” batteries – that being batteries which have cells greater than 300 Amp-Hr capacity.  Himassi doesn’t say if they are using 4 individual 400 Amp=Hr cells or are paralleling 8 200 Amp-Hr cells.  Both have pluses and minuses.  But at almost 90 pounds (87.1 pounds) that is going to be a real pain to install & remove.  I’d go for two each 200 Amp-Hr or 300 Amp-Hr batteries.  That way, if a cell were to fail, you are not dead in the water.  (Simply remove the battery with the bad cell and carry on, aware of the reduced capacity).

The BMS is extremely important, and all are not equal. 

Besides the amount of charge/discharge current they can handle, there are more subtle functions that some have and others don’t – and some don’t work as advertised.  Things like

Hi/low temperature cut-off – does it really disconnect the cells for protection. 

Same with hi/low voltage cut-off. 

They don’t say which BMS they are using, if it’s a in-house design or a proven device already on the market. 

WiFi is nice – but mostly useful if you have control over the BMS values.  Otherwise, you are just looking at individual cell voltages, which can’t be otherwise monitored outside of the battery case.

 

Regarding the heating, it sounds like they are using the basic approach, which yields little, IMHO.  With the heated option, it will allow you to charge the battery down to -20°C (-4°F).  It does NOT change the discharge temperature (the same -20°C or -4°F).  This should be referring to in internal battery temperature.      

The process described is the heating film turns on at 32°F UNDER charging conditions.  If the battery is not needing charge, it won’t come on.  During this heating phase, the charger supplies power ONLY to the heating film, until the internal temp reaches 50°F, at which time it turns off the heater and begins charging the battery.  This presumably would continue until the battery cools down to 32°F at which point the process repeats.  Note that during charging (depending on the charge level) the battery will warm up on its own, which should delay the time it takes to drop to 32°F.  It is less than desirable if you plan on using solar to maintain the batteries in cold weather.  There are reports that it can take ½ up to most of the sun producing day to just heat the batteries, which leaves little time to actually charge them.  This is the most rudimentary way to heat batteries, and IMHO, is only useful in selling batteries they claim to be low temperature rated. 

If you plan on storing you coach, with the LiFEPO4 batteries installed, note that no heating function will occur, since there needs to be a charge function to enable it.  That means you must     ensure you have good solar or shore power to keep the batteries from freezing.  This may not be an issue in your case, I mention it because it is in mine.

 

On to your question of the BIRD, it will serve no useful function if you install a DC-DC Charger. 

The BIRD basically connects both banks (Chassis and House) together when either bank had a voltage greater than around 13.5 volts to allow charging of the other bank.  You will be using a DC-DC Charger to charge the house (LiFePO4) batteries from the Alternator so that half of the BIRD is not needed or wanted. 

As far as charging the Chassis batteries from the House Chargers (Inverter or Solar) it will not be the correct voltage for a FLA or AGM Chassis battery. If you need to charge the Chassis battery from Shore Power, get a Battery Maintainer or, a DC-DC Charger from the House to Chassis, or, a Solar Controller.

The last function of the BIRD (not really part of the BIRD, but part of the Big Boy that the BIRD controls) is the BOOST function.  You really don’t want to be attempting to start the main engine with you LiFePO4 batteries.  Unless you have 900+ Amp capability you will likely degrade, if not destroy, your Lithium battery. 

If you have an unexpected need to “BOOST”, do if from you Toad, or call ERS, it will be much cheaper than replacing your LiFePO4 batteries.  Based on the above, I would recommend disconnecting the BIRD and removing the Big Boy since they will become obsolete.

 

Some food for though.  I have totally isolated the Chassis electrical system from the House electrical system. 

The chassis battery is charged by the engine alternator when running down the road, and by a solar panel (the Monaco original 100 Watt) and a dedicated solar charge controller (set for FLA batteries).  There is no direct way to otherwise charge the Chassis battery.  I do have a disconnected 110 VAC battery maintainer that I could use if there were an absence of sun and I happened to discharge the Chassis batteries while parked, but I’ve not needed it.

The house battery is primarily charged by solar (1300 W) and also by the Victron MultiPlus Inverter/Charger when the SOC drops below 40%.  I also have AGS enabled at 20% for dry camping without Shore Power.  Other than the initial test, the AGS has never been needed.  But I do practice battery management, and use the generator when cooking meals to supplement the solar when necessary. 

I have needed to “Jump” or “BOOST” my chassis batteries once, due to not turning off all the chassis electronics when dry camping.  I simply pulled my toad up to the back of the coach and jumped it.  

 

Regarding the need for 60 Amps vs 30 Amps or less in a DC-DC charger, you need to ask yourself how much you really need.  I always try to start out with my House batteries over 50% SOC, and I don’t have much (less than 150 W – 12 Amps) draw, and my solar will carry that easily.  But, if you don’t have solar, have a residential refrigerator and other power consuming devices that will be in use while driving, then you might need to supplement from the alternator. 

 

Lastly, I would never connect an alternator directly to LiFePO4 batteries.  Even if the alternator could supply the 200 – 300 Amps charge current, I do NOT want my LiFePO4 batteries sitting with 14.2 – 14.4 charge volts for hours while I motor down the road.  Once the batteries are full, you should immediately reduce the voltage to around 13.6 volts (follow the cell manufacturers recommendation for “Float” voltage).

 

One last thing I’ll mention is PROTECTION.  Yes, a good BMS may save your cells, but it may also burn up and allow your cells to be destroyed.  Based on my previous life as an Electronics Design Engineer, I recommend taking actions before the BMS has to.  The BMS should be you last and final line of resort.  That mean, turning off your charger or discharge before you reach the minimum/maximum temperature, current or voltage.  Many of the current Inverters (I have the Victron MultiPlus) can be programed to do this.  So can the Victron MPPT Charge Controllers.  I would not intentionally design a system where the BMS was the only thing protecting the LiFePO4 cells, not to mention protecting the BMS itself.

 

This post is much longer than I intended.  But, if anyone has any questions, I’m happy to respond.

  -Rick N.

 

[Paul J A]

7 hours ago, TOBYLB4 said:

Thanks Paul, I've seen this just not sure I want to cut on my door. Also it's a little pricey.

The engine compartment door on a Newell is awesome. Aluminum and very functional. It would not be difficult for a Fab shop to make one. Maybe less than what Ricki gets for his panel. That is what i would do. All you need is the door . You already have the mounting hardware. 

[Ivan K]

While I don't plan on lithium in the near future, all this is a great free! learning experience and I appreciate everyone involved sharing their experiences and opinions!

[ekgflashnet]

Rick,

You've brought up some good points that I want to further understand.  First, the idea that the BIRD is not useful or needed.  If there is not a BIRD, then doesn't the alternator just charge the chassis batteries only since there is no connection to the house batteries any longer?  How do you charge the house batteries using the alternator via the dc-dc charger? Are you suggesting that the alternator be used to charge both the house and chassis batteries simultaneously (i.e. jump the house and chassis post on the BIRD)?  I think your point on having the BIRD connect the house to the chassis battery while charging the house batteries via the inverter/charger is a good point.  The charger will be putting out 14.5V (or so) to the house lithium batteries.  So, the BIRD would pass that on to the chassis battery when the house batteries are over 13.5V and the BIRD engages.  However, I'm proposing to place the dc-dc charger after the BIRD on the house side post.  If I'm charging the house batteries via the inverter/charger, nothing would get passed to the BIRD as the dc-dc charger is there.  So, I believe in this case, the chassis batteries are no longer charged when the house batteries are above 13.5V (which means in effect, the BIRD is no longer bi-directional, just uni-directional (ie. UNIRD 🙂

In my case, I live and travel in high elevation areas.  So, I feel that I'm likely to run into nights where the temperature can be quite cool even into late spring and early fall dates. On the idea of using self-heating lithium batteries, what do you think about using a small 100W 12V thermostat controlled heater used in the battery bay?  In my case, the house batteries are located in an enclosed space) Energy wise, I'm wondering if it is more efficient to maintain an enclosed space at some desired temperature rather than try to bring up cold batteries up to temperature.  The savings in using non-heated batteries would easily pay for the 12V heater.

steveg 2005 DDIV

[wamcneil]

2 hours ago, ekgflashnet said:

  How do you charge the house batteries using the alternator via the dc-dc charger?

The DC-DC charger has an Input terminal and an Output terminal.

Input would be connected to the chassis 12v system (alternator and starting batteries) 

Output would be connected to the house 12v system (house batteries, inverter/charger, solar)

The DC-DC charger takes whatever Input voltage is present on the chassis side (8v-16v) and up or down converts it to the specified Output charge voltage for the house side.

I think some models come with an ignition sense wire so the DC-DC charger only charges when the engine is running.

Cheers,

Walter

 

Edited April 24, 2022 by wamcneil

[timaz996]

Steve,

My battery box is back next to the engine (as most are) and is just a steal box with two large holes for battery cables. It has been as low as 25F in the mornings and my batteries have not gotten colder then 37F. I'm plugged into a 20amp circuit. I do have my Victron solar controller set to not charge below 40F. I guess my coach has a different setup for charging my batteries then yours Steve. It charges both house and chassis batteries at the same time. The two of my batteries together can be charged as fast 200amps so I didn't want to be restricted to only a 30 or 40 amp charging rate. Here is my charging circuit bay. As with generators you should size an alternator to 75% of it's max output rating. The batteries only pulled about 50% of my alternator's rated load. (including all 12 volt loads at the time. Good luck with your project and you will love how fast they charge to float.

Tim 

Edited April 24, 2022 by Tim-AZ

[ekgflashnet]

Thanks Walter, 

that makes sense to me.  So, effectively, when the alternator is running, it is charging both the chassis battery and house batteries (regardless of the state of the chassis battery).  Total charge to the house battery would be limited by the dc-dc charger.  The model I was looking at also has the trigger wire as well.  Is there an easy location to tie this ignition sense wire to in/near the rear bay?  I'll have to take a look at my schematic.  Maybe I'll find something there to tie into.

FYI, my house batteries are located on the PS rear bay.  Nothing else is in that bay other than the batteries.

steveg 2005 DDIV

[RoadTripper2084]

On 4/23/2022 at 11:31 AM, waterskier_1 said:

Rocketman3 has brought up some great points.  I’ll add or amplify on some that I think need to be considered.

First, I don’t like the “huge” batteries – that being batteries which have cells greater than 300 Amp-Hr capacity.  Himassi doesn’t say if they are using 4 individual 400 Amp=Hr cells or are paralleling 8 200 Amp-Hr cells.  Both have pluses and minuses.  But at almost 90 pounds (87.1 pounds) that is going to be a real pain to install & remove.  I’d go for two each 200 Amp-Hr or 300 Amp-Hr batteries.  That way, if a cell were to fail, you are not dead in the water.  (Simply remove the battery with the bad cell and carry on, aware of the reduced capacity).

The BMS is extremely important, and all are not equal. 

Besides the amount of charge/discharge current they can handle, there are more subtle functions that some have and others don’t – and some don’t work as advertised.  Things like

Hi/low temperature cut-off – does it really disconnect the cells for protection. 

Same with hi/low voltage cut-off. 

They don’t say which BMS they are using, if it’s a in-house design or a proven device already on the market. 

WiFi is nice – but mostly useful if you have control over the BMS values.  Otherwise, you are just looking at individual cell voltages, which can’t be otherwise monitored outside of the battery case.

 

Regarding the heating, it sounds like they are using the basic approach, which yields little, IMHO.  With the heated option, it will allow you to charge the battery down to -20°C (-4°F).  It does NOT change the discharge temperature (the same -20°C or -4°F).  This should be referring to in internal battery temperature.      

The process described is the heating film turns on at 32°F UNDER charging conditions.  If the battery is not needing charge, it won’t come on.  During this heating phase, the charger supplies power ONLY to the heating film, until the internal temp reaches 50°F, at which time it turns off the heater and begins charging the battery.  This presumably would continue until the battery cools down to 32°F at which point the process repeats.  Note that during charging (depending on the charge level) the battery will warm up on its own, which should delay the time it takes to drop to 32°F.  It is less than desirable if you plan on using solar to maintain the batteries in cold weather.  There are reports that it can take ½ up to most of the sun producing day to just heat the batteries, which leaves little time to actually charge them.  This is the most rudimentary way to heat batteries, and IMHO, is only useful in selling batteries they claim to be low temperature rated. 

If you plan on storing you coach, with the LiFEPO4 batteries installed, note that no heating function will occur, since there needs to be a charge function to enable it.  That means you must     ensure you have good solar or shore power to keep the batteries from freezing.  This may not be an issue in your case, I mention it because it is in mine.

 

On to your question of the BIRD, it will serve no useful function if you install a DC-DC Charger. 

The BIRD basically connects both banks (Chassis and House) together when either bank had a voltage greater than around 13.5 volts to allow charging of the other bank.  You will be using a DC-DC Charger to charge the house (LiFePO4) batteries from the Alternator so that half of the BIRD is not needed or wanted. 

As far as charging the Chassis batteries from the House Chargers (Inverter or Solar) it will not be the correct voltage for a FLA or AGM Chassis battery. If you need to charge the Chassis battery from Shore Power, get a Battery Maintainer or, a DC-DC Charger from the House to Chassis, or, a Solar Controller.

The last function of the BIRD (not really part of the BIRD, but part of the Big Boy that the BIRD controls) is the BOOST function.  You really don’t want to be attempting to start the main engine with you LiFePO4 batteries.  Unless you have 900+ Amp capability you will likely degrade, if not destroy, your Lithium battery. 

If you have an unexpected need to “BOOST”, do if from you Toad, or call ERS, it will be much cheaper than replacing your LiFePO4 batteries.  Based on the above, I would recommend disconnecting the BIRD and removing the Big Boy since they will become obsolete.

 

Some food for though.  I have totally isolated the Chassis electrical system from the House electrical system. 

The chassis battery is charged by the engine alternator when running down the road, and by a solar panel (the Monaco original 100 Watt) and a dedicated solar charge controller (set for FLA batteries).  There is no direct way to otherwise charge the Chassis battery.  I do have a disconnected 110 VAC battery maintainer that I could use if there were an absence of sun and I happened to discharge the Chassis batteries while parked, but I’ve not needed it.

The house battery is primarily charged by solar (1300 W) and also by the Victron MultiPlus Inverter/Charger when the SOC drops below 40%.  I also have AGS enabled at 20% for dry camping without Shore Power.  Other than the initial test, the AGS has never been needed.  But I do practice battery management, and use the generator when cooking meals to supplement the solar when necessary. 

I have needed to “Jump” or “BOOST” my chassis batteries once, due to not turning off all the chassis electronics when dry camping.  I simply pulled my toad up to the back of the coach and jumped it.  

 

Regarding the need for 60 Amps vs 30 Amps or less in a DC-DC charger, you need to ask yourself how much you really need.  I always try to start out with my House batteries over 50% SOC, and I don’t have much (less than 150 W – 12 Amps) draw, and my solar will carry that easily.  But, if you don’t have solar, have a residential refrigerator and other power consuming devices that will be in use while driving, then you might need to supplement from the alternator. 

 

Lastly, I would never connect an alternator directly to LiFePO4 batteries.  Even if the alternator could supply the 200 – 300 Amps charge current, I do NOT want my LiFePO4 batteries sitting with 14.2 – 14.4 charge volts for hours while I motor down the road.  Once the batteries are full, you should immediately reduce the voltage to around 13.6 volts (follow the cell manufacturers recommendation for “Float” voltage).

 

One last thing I’ll mention is PROTECTION.  Yes, a good BMS may save your cells, but it may also burn up and allow your cells to be destroyed.  Based on my previous life as an Electronics Design Engineer, I recommend taking actions before the BMS has to.  The BMS should be you last and final line of resort.  That mean, turning off your charger or discharge before you reach the minimum/maximum temperature, current or voltage.  Many of the current Inverters (I have the Victron MultiPlus) can be programed to do this.  So can the Victron MPPT Charge Controllers.  I would not intentionally design a system where the BMS was the only thing protecting the LiFePO4 cells, not to mention protecting the BMS itself.

 

This post is much longer than I intended.  But, if anyone has any questions, I’m happy to respond.

  -Rick N.

 

I just finished my LiFeP04 280Ah battery assembly and installation on my rig. Pretty much followed your recipe above:

• Removed the original Battery Isolator, Boost solenoid, and chassis Battery Maintainer from the engine bay electrical panel.
• Installed a Renogy 60A DC-DC charger in the panel between the chassis/alternator and LiFeP04 / Converter + Inverter.
• Moved the factory 80W? solar setup to chassis battery (FLA) instead of the House to act as a maintainer while in storage, etc. I also have an external low-amperage battery maintainer that I can plugin to the engine outlet if require to maintain the chassis battery.
• I installed my LiFePO4 battery in the utility bay next to the inverter, away from elements and will benefit from the internal heating from the hot water tank, inverter, etc.) in cold weather (I'm Canadian, eh!).

First real trip is coming up this weekend, but so far it all seems to work as planned, while driving LiFP04 charges up to 60A from the alternator->Chassis FLA battery->DC-DC charger.  When plugged in to shore power (or running the generator) the LiFP04 charges off the converter's built-in 100A charger.

My battery's BMS has bluetooth support so I can monitor/control everything from my phone, so replaces the need for a bluetooth charger or battery shunt.

In my case I was trying to do a "minimal" impact conversion to LiFePO4, utilizing the stock FLA converter, etc. as much as possible. My converter has different pre-set settings I can configure with DIP switches for different charge/float voltages so I a still experimenting with those to find the "best" match for my needs. If necessary I can also put it into manual charge mode where I have to initiate the charge session vs. it doing so as soon as 120v power is supplied. So I do have a few "levers" at my disposal to control the charge profile from the stock converter.

Will report back after our 2 week trip with more real-world experience.