LiFePO4 Battery Isolation Manager

[al1florida]

On huge advantage of lithium that was not covered very well was that "lithium has no requirement" to be brought to 100% or even 90% as does lead acid (AGM is a lead acid battery).

In fact it is perfectly fine to use your lithium batteries by only getting to 80% full and then using to 40% on a daily basis.

If you fail to bring your lead acid battery to 100% every 5-7 days, over a month or few months you will find that the battery plates have sulfated and the battery capacity as been greatly reduced.

Because of the recent posts about charging lithium at 14.4V and getting to 95% to 100%, I felt far to much emphasis is being placed on fully charging lithium batteries.

If your only source of charging is the RV engine alternator then the need to provide 14.4V from the alternator is more important.

The lithium will charge at 13.4V to 13.6V, just not as fast as it will at 14.2V to 14.4V. So if you have solar panels the alternator will provide some charging and the sun will take care of the remainder.

[jerichorick]

Originally Posted by powercat_ras

Here's a little tutorial to try to educate, and to correct some mis-information in this thread.

LiFeP04 Batteries are made of multiple small 3.2 volt nominal battery cells connected in a combination of series and parallel. UL Listed ones MUST have a integrated Battery Management System (BMS).

BMS does constant monitoring of each of the four (3.2 Volt) Lithium Cells connected in series that are required to produce a 12.8 Volt Lithium Battery. The BMS disconnects the battery from the load or charger, to prevent damage, if monitoring indicates. Each cell is monitored for temperature and excess current drain and again the battery is disconnected from the load if these limits are exceeded. The BMS also monitors the state of charge for each of the four cells and automatically balances their voltages during the recharge cycle to bring all cells to full charge at the same time. This balancing ensures a safe full charge and long battery life. This complex BMS accounts for much of the high cost of UL Listed LiFeP04 batteries, along with the cost of interconnecting many small LiFeP04 cells together in series and parallel to make a large size battery pack. For example, it takes 80 type 26650 5 Ah capacity 3.2 V LiFeP04 cells to make a 100 Amp Hour LiFeP04 battery. FYI, 26650 is the same size individual batteries used in the Tesla electric car.

Some key facts:

UL Listed 12 volt nominal LiFeP04 battery need a charging voltage of 14.4 to fully charge. Any battery equalization feature of converter/chargers that would output more than 14.4 volts needs to be disabled.

LiFeP04 purpose designed chargers and solar charge controllers only have 14.4 volt output "boost mode" and 13.6 volt output "float mode".

Unlike Lead Acid batteries, LiFeP04 chemistry batteries accept full charge current up to about 95% charge, allowing them to be recharged faster as they only use a bulk charge mode and don't need an lower charge rate equalization charge mode.

The 95% charged LiFeP04 battery starts delivering load when the system voltage is 13.4 volts or less. Voltage will drop to 12.8 after a few % of storaged charge is consumed then slowly drop to 12.0 at about 80% consumed.

LiFeP04 batteries worst case storage and discharge temp range is -4 to +160 F. All manufacturers currently recommend a narrower operating temperature range than this to extend life and to avoid pusing the limits of what the batteries can do.

LiFeP04 batteries should not be charged if the individual cell temperatures are below freezing, 32F.

LiFeP04 batteries only lose 2-4% of their stored charge per month if they are stored disconnected.

Typical Automotive / Truck Alternator DC charging systems output less than 14.4 volts and this prevents them from fully charging LiFeP04 battery packs and increases charge time due to the lower voltage difference between the charging voltage and the internal battery voltage. It will recharge them to about 70%.

Excellent, well organized and well articulated write-up. Thank you for clearing up my defective understanding of this topic.
How do you keep your batteries from getting too cold to charge safely? If I were to upgrade my ageing AGM bank that would be a major consideration.

Will the BMS compensate for a higher than 14.4V charger output?
Rick

[SLOweather]

Originally Posted by jerichorick

How do you keep your batteries from getting too cold to charge safely?

You can always put them inside your camper. They are light (100ah = 29 lbs), and have no acid or offgassing to be concerned with.

Will the BMS compensate for a higher than 14.4V charger output?
Rick

As I understand it, it won't "compensate", it will just disconnect the battery to protect it. Hence the need for proper charge regulators.

[al1florida]

Originally Posted by jerichorick

Excellent, well organized and well articulated write-up. Thank you for clearing up my defective understanding of this topic.
How do you keep your batteries from getting too cold to charge safely? If I were to upgrade my ageing AGM bank that would be a major consideration.

Will the BMS compensate for a higher than 14.4V charger output?
Rick

Assuming your batteries are like mine in my Journey and exposed to the open air back by the engine:
-- Build an enclosure, simple plywood box is fine.
-- Buy one or two heating pads like these: https://www.amazon.com/Flukers-Repti...ilpage_o07_s00 to put in the battery box. The above heating pad is 120V so you will need to add a small 100 watt inverter to power the 20 watt heating pad.


Do keep in mind it is the temperature of the batteries, not the air temp. Also charging and using (discharging) creates some heat to help keep the batteries above 32F inside the box. So if the daytime temps go into the mid to upper 30's and only the night time temps go below freezing the batteries will be fine.

[jerichorick]

Originally Posted by al1florida

Assuming your batteries are like mine in my Journey and exposed to the open air back by the engine:
-- Build an enclosure, simple plywood box is fine.
-- Buy one or two heating pads like these: https://www.amazon.com/Flukers-Repti...ilpage_o07_s00 to put in the battery box. The above heating pad is 120V so you will need to add a small 100 watt inverter to power the 20 watt heating pad.


Do keep in mind it is the temperature of the batteries, not the air temp. Also charging and using (discharging) creates some heat to help keep the batteries above 32F inside the box. So if the daytime temps go into the mid to upper 30's and only the night time temps go below freezing the batteries will be fine.

Great suggestions. I am thinking along the lines of ridged construction insulation board to line the battery box with. Because we volunteer we will, on that rare occasion, get caught in an unexpected freeze at the camp we are at. We try to move to a warmer area before the snow flies but nature happens.

I think my Magnum inverter will work for my charging source. With the new controller I can set the charge and float voltage and the charge time. Not the float time on my control board version. If I am reading all of this correctly, the BMS will stop the charging even with charge voltage present?
I am doing future planning. I now have 6 aging AGM's, group 31 100ah (?) batteries. Any advise as to what I would need for a reliable LiFeP04 replacement bank? Because of the depth of discharge, I figure the controlling factor is for the 2800W inverter requirement. We Walmart style camp when traveling between projects. We freely use our generator when needed for HVAC or battery charging. We have no problem running silent, when the weather permits, for as long as the batteries are happy.
This is one of the best threads I have come across on this forum. Your civilized intelligence is well appreciated by me. Thank you all!

[West6550]

Originally Posted by jerichorick

I believe the lithium batteries are damaged if they are charged over 13.4V. The AGM's charge to 13.8V if I recall.

Per Battleborn the charging voltage is 14.2-14.6 and the recommended float voltage is 13.6 or lower.


I have the inverter/charger and solar charge controller figured out, I only needed help with wiring in this piece, but I have that figured out now.


We will be removing our converter and going with a AIMS inverter/charger that has numerous voltage selections for charging and float. The Victron solar charge controller is adjustable as well.

[West6550]

Originally Posted by SLOweather

Jesse from BB called me this afternoon, and we got a lot of things clarified.

The "drop in" feature of the 100ah battery mainly refers to its physical Group 27 size. The integral BMS does protect the battery from over charge, over discharge, temperature excursions and the like.

As noted above in Powercat's excellent summery, Li batteries need 14.4 volts to come to a full charge. The BMS doesn't, however, fully charge a battery from the standard alternator or converter sources.

For my one (potentially 2) 100 ah battery system, the solution he recommended was the Sterling Battery to Battery Charger BB-1230. This is essentially an intelligent DC/DC boost converter that takes the nominal chassis battery voltage and boosts it to a programmable DC voltage, 14.4 in this case, to fully charge a BB battery. It's a simple 2 wire connection, to each battery's positive terminal.

Jesse said that the isolator mentioned above would be used for 300AH or greater battery banks, mainly to minimize the wear on the alternator trying to charge a depleted big bank.

Thanks for posting a follow up! I have been very pleased with how easy they are to get on the phone and to answers to questions.


The BMS system on Battleborns is one of the things I liked about them. Sure you can't charge them if it is too cold out.. but you can still drain them aka run the furnace to stay warm over night. We follow the weather and being born and raised in Florida, we won't be trying to camp in long spells of cold weather LOL especially with my wife .



After reading your response and the post above I doubled checked the voltage on the sheet they sent with the batteries. 14.4 sounds to be ideal, but it states the charge voltage range is 14.2 - 14.6 with the float charge being 13.6 or lower. I grabbed my multi-meter and cranked up the engine. The reading at the wire going into the solenoid on my RV was 14.2 and was bouncing to 14.3 here and there. That voltage was taken at an idle with the A/C running. I recommend you test yours as you might need to grab that booster like Jesse said. I am okay with the 14.2 as we will have solar, shore power, and we have an onboard generator to help top of the batteries if needed. We didn't have an alternator on our travel trailer and I never got below 92% on the old AGM battery bank running all the plugs and the fridge on 120v with the solar we had alone. We didn't even have an generator on that rig so the alternator is a bonus charger for us!

[West6550]

Originally Posted by SLOweather

You can always put them inside your camper. They are light (100ah = 29 lbs), and have no acid or off gassing to be concerned with.

I originally thought they wouldn't fit inside, but I did some measuring today under the dinette and we can fit them. So I'm not going to even bother with the outside factory battery box. I am going to remove the old AGM and put the BB's under the dinette. That way I don't need to enclose the battery box or put a battery warmer in it. Plus they will be closer to the inverter and I can use less wire!! WIN WIN!

[al1florida]

The BMS should be thought of as a last resort protection for your battery (i.e. fail safe protection), not as something to manage the charging or discharging.
For whatever battery you choose it would be good to know what the recovery process is for low voltage and high voltage cutoff is.

Typically when the BMS triggers, then all 12V is cut off to the RV. No lights, fridge, no starting the generator, etc. If your solar controller is like mine (Morningstar Tristar MPPT 60) it doesn't work unless it sees 12V from the battery. The BMS is protecting the batteries from catastrophic failure.



Once the BMS triggers it may stay in the disconnected state it may not be able to see 12V or ground from the external source until a manual process is taken to energize the solenoids to allow it to see the external power.

[al1florida]

Originally Posted by West6550

Thanks for posting a follow up! I have been very pleased with how easy they are to get on the phone and to answers to questions..........
After reading your response and the post above I doubled checked the voltage on the sheet they sent with the batteries. 14.4 sounds to be ideal, but it states the charge voltage range is 14.2 - 14.6 with the float charge being 13.6 or lower. I grabbed my multi-meter and cranked up the engine. The reading at the wire going into the solenoid on my RV was 14.2 and was bouncing to 14.3 here and there. That voltage was taken at an idle with the A/C running. I recommend you test yours as you might need to grab that booster like Jesse said. I am okay with the 14.2 as we will have solar, shore power, and we have an onboard generator to help top of the batteries if needed. We didn't have an alternator on our travel trailer and I never got below 92% on the old AGM battery bank running all the plugs and the fridge on 120v with the solar we had alone. We didn't even have an generator on that rig so the alternator is a bonus charger for us!

The alternator regulator is temperature compensated. In very cold weather the voltage will go higher, maybe as much as 15.0V or higher in very cold weather, i.e. 15-20 degrees.

[al1florida]

Originally Posted by jerichorick

Great suggestions. I am thinking along the lines of ridged construction insulation board to line the battery box with. Because we volunteer we will, on that rare occasion, get caught in an unexpected freeze at the camp we are at. We try to move to a warmer area before the snow flies but nature happens.

I think my Magnum inverter will work for my charging source. With the new controller I can set the charge and float voltage and the charge time. Not the float time on my control board version. If I am reading all of this correctly, the BMS will stop the charging even with charge voltage present?
I am doing future planning. I now have 6 aging AGM's, group 31 100ah (?) batteries. Any advise as to what I would need for a reliable LiFeP04 replacement bank? Because of the depth of discharge, I figure the controlling factor is for the 2800W inverter requirement. We Walmart style camp when traveling between projects. We freely use our generator when needed for HVAC or battery charging. We have no problem running silent, when the weather permits, for as long as the batteries are happy.
This is one of the best threads I have come across on this forum. Your civilized intelligence is well appreciated by me. Thank you all!

Lithium is an expensive option unless you do lots of dry camping or boondocking. Plain old golf cart batteries from Costco or Sam's Club for under $100 each, work just fine. Especially if you have a slideout battery tray to check the water level every 2-3 months.

Going from one project to another with a few days or a week of dry camping and then back on elect hookups work perfectly well for lead acid batteries. We have lithium and may go for weeks w/o elect hookups. On our 2016 trip to Alaska from Oregon and back, we dry camped or boondocked for 137 of the 139 days of the trip. We also only ran our generator 1 time for about 1.5 hours to charge the batteries.

Your Magnum inverter/charger should have a custom battery setting, however you need the remote to program it for the lithium voltages.

Note that the BMS does not stop the charging. It disconnects the battery from the RV. That is you loose all 12V. You won't be able to start the generator. (The battery boost switch on the dash board may allow the generator to start.) You may have to use a manual procedure to reset the BMS to allow it to charge.

[al1florida]

Can anyone with Battle Born batteries provide info as to what is required (if anything) when the BMS protects the batteries from over/under voltage condition?

[SLOweather]

So far, with ours, it has tripped out a couple of times after ~30 seconds on overcurrent when running the microwave on a partially depleted battery. I suppose the MW causes the inverter to draw right at 100 amps or so. I'll have to do a little test and check the Victron monitor to see.


Now that I type this, I think my work-around would be to run the MW at reduced power. The cycling of the magnetron would still draw high current, but intermittently instead of continuously.


In any case, after a few seconds. the battery has always reset itself.

Originally Posted by al1florida

Can anyone with Battle Born batteries provide info as to what is required (if anything) when the BMS protects the batteries from over/under voltage condition?

[al1florida]

Originally Posted by SLOweather

So far, with ours, it has tripped out a couple of times after ~30 seconds on overcurrent when running the microwave on a partially depleted battery. I suppose the MW causes the inverter to draw right at 100 amps or so. I'll have to do a little test and check the Victron monitor to see.

Now that I type this, I think my work-around would be to run the MW at reduced power. The cycling of the magnetron would still draw high current, but intermittently instead of continuously.

In any case, after a few seconds. the battery has always reset itself.

Are you sure it is the battery dropping out or the inverter? If it is the battery then you will loose all 12V to the RV. Lights, fridge, etc. My experience in the past is that the inverter is the one detecting a problem and then resets after 30 seconds or so.
BTW a typical microwave pulls about 140 amps of 12V DC though the inverter. What size inverter do you have?

[SLOweather]

The inverter is a 2kW Xantrex Freedom XC. It was definitely the battery BMS working, because we did have a 12v power failure for a few seconds.

Originally Posted by al1florida

Are you sure it is the battery dropping out or the inverter? If it is the battery then you will loose all 12V to the RV. Lights, fridge, etc. My experience in the past is that the inverter is the one detecting a problem and then resets after 30 seconds or so.
BTW a typical microwave pulls about 140 amps of 12V DC though the inverter. What size inverter do you have?

[jerichorick]

Originally Posted by al1florida

Lithium is an expensive option unless you do lots of dry camping or boondocking. Plain old golf cart batteries from Costco or Sam's Club for under $100 each, work just fine. Especially if you have a slideout battery tray to check the water level every 2-3 months.

Going from one project to another with a few days or a week of dry camping and then back on elect hookups work perfectly well for lead acid batteries. We have lithium and may go for weeks w/o elect hookups. On our 2016 trip to Alaska from Oregon and back, we dry camped or boondocked for 137 of the 139 days of the trip. We also only ran our generator 1 time for about 1.5 hours to charge the batteries.

Your Magnum inverter/charger should have a custom battery setting, however you need the remote to program it for the lithium voltages.

Note that the BMS does not stop the charging. It disconnects the battery from the RV. That is you loose all 12V. You won't be able to start the generator. (The battery boost switch on the dash board may allow the generator to start.) You may have to use a manual procedure to reset the BMS to allow it to charge.

Here is my thinking. On the AGM's, the voltage sag is great when we run the convection oven. This means that the batteries now supply the power by providing a higher current, about 170A if I recall correctly. If the battery voltage stays high under load the amps needed to feed the power demand of the load are lower. Lower amps means less voltage drop from the battery wire supply to the inverter. The inverter runs cooler on the higher voltage, less current. This is a good thing.
Wet cells would give even a worse performance. The internal resistance of the battery is even higher than that of the AGM's. Thus worse performance per heavy load usage.

Cost for a new bank of 6, 100ah AGM's is around $1,800++. I have a new ME-RC50 remote controller for my Magnum 2800w inverter. Though my main board is only a series 3, I do have control of the charge and float voltages. Two lithium's would be about $2,000 and would give me about 2/3's the power I now have available and reduce the weight on the coach by about 350 to 400 #. My generator has the auto start feature for charging the battery bank. I can set the start sense voltage. What am I missing? It seems too simple looking at it this way.

Another thought about inverters. Pure sine wave inverters, like mine, are more efficient than the modified sine wave types. I think this is a key factor in getting the most out of any house battery bank.
With everything we have covered here, no mention has been made of how changes to the charger will effect the start battery. Hummm.

[al1florida]

Originally Posted by SLOweather

The inverter is a 2kW Xantrex Freedom XC. It was definitely the battery BMS working, because we did have a 12v power failure for a few seconds.

Thanks, good info.

What is the amp hour (AH) capacity of the batteries. Kind of surprising to see lithium battery voltage drop that low or have a current overload unless you only have about 100AH of battery.

[al1florida]

Originally Posted by jerichorick

Here is my thinking. On the AGM's, the voltage sag is great when we run the convection oven. This means that the batteries now supply the power by providing a higher current, about 170A if I recall correctly. If the battery voltage stays high under load the amps needed to feed the power demand of the load are lower. Lower amps means less voltage drop from the battery wire supply to the inverter. The inverter runs cooler on the higher voltage, less current. This is a good thing.
Wet cells would give even a worse performance. The internal resistance of the battery is even higher than that of the AGM's. Thus worse performance per heavy load usage.

Cost for a new bank of 6, 100ah AGM's is around $1,800++. I have a new ME-RC50 remote controller for my Magnum 2800w inverter. Though my main board is only a series 3, I do have control of the charge and float voltages. Two lithium's would be about $2,000 and would give me about 2/3's the power I now have available and reduce the weight on the coach by about 350 to 400 #. My generator has the auto start feature for charging the battery bank. I can set the start sense voltage. What am I missing? It seems too simple looking at it this way.

Another thought about inverters. Pure sine wave inverters, like mine, are more efficient than the modified sine wave types. I think this is a key factor in getting the most out of any house battery bank.
With everything we have covered here, no mention has been made of how changes to the charger will effect the start battery. Hummm.

I agree with your thoughts on moving to lithium.

[SLOweather]

Right now it is indeed just one 100AH BB. I plan on adding a second one soon. I need to rearrange some cables in the under-step battery bay to fit a second one in.


I had 2 Group 27 flooded batteries in the Suncruiser, wired to a Perko switch so I could choose either battery or bank them together. That was also my battery disconnect. I don't anticipate installing one on these batteries.

Originally Posted by al1florida

Thanks, good info.

What is the amp hour (AH) capacity of the batteries. Kind of surprising to see lithium battery voltage drop that low or have a current overload unless you only have about 100AH of battery.

[SLOweather]

Originally Posted by jerichorick

With everything we have covered here, no mention has been made of how changes to the charger will effect the start battery. Hummm.

AFAIK, the start or engine battery is only charged off the engine alternator unless you have made other arrangements.