buh bye AGM

[Wiley1]

After 5.5 years, my 4x 100Ah AGM battery bank is performing like 60ah.
I won't replace them with another set of AGMs and here is why:

Cost of 4 new AGM batteries, 100Ah each, is about $760. But, to avoid discharging below 50% SoC, only 200Ah is usable. Over 5.5 years, that's a cost of $138 per year ($0.69 per Ah per year).

Cost of 3 new LifePO4 batteries, 100Ah each, is about $570. Because these can be routinely taken down to 20% SoC, the usable capacity is 240ah which is 20% greater than the 4 AGMs. Over 10 years, that's a cost of $57 per year ($0.24 per Ah per year).

As a bonus, 3 LifePO4 batteries weigh only 66 pounds compared to 251 for the 4 AGMs. That's 185 pounds that I won't have to lug around anymore.

An additional benefit is the significantly less steep discharge voltage curve. When LifePO4 battery reaches 50% SoC, the open circuit voltage drops to about 13.2. Compare that to an AGM battery that would be fortunate to measure 12.2.

So, LifePO4 wins in every category: initial cost, cost over usable life, weight, capacity, number of cable connections needed, and discharge voltage curve.
Unless there is a flaw in my math or logic, this is an absolute NO-BRAINER.



The only downside I can imagine is the lack of CCA. Each LifePO4 battery can deliver a maximum of 100 amps, (x3 = 300) where an AGM battery can give up to 1000 amps (x4 = 4000). This could possibly be an issue if the chassis battery is dead and the "Emergency Start" button is needed in really cold weather. I'll take my chances.

[ducksface]

Very convincing to right minded people.
Thanks.
There are some folk who can't be convinced no matter how compelling and how good the charts.

I tested my emergency start against my house lithiums.
Everything works just fine.
When jump starting a d10 dozer they might be a problem( but all I could think of needing that cranking power)

[Wiley1]

Originally Posted by ducksface

Very convincing to right minded people.
Thanks.
There are some folk who can't be convinced no matter how compelling and how good the charts.

Maybe if people would stop posting pictures of burned up RV's.

[The Rookie]

Originally Posted by Wiley1

After 5.5 years, my 4x 100Ah AGM battery bank is performing like 60ah.
I won't replace them with another set of AGMs and here is why:

Cost of 4 new AGM batteries, 100Ah each, is about $760. But, to avoid discharging below 50% SoC, only 200Ah is usable. Over 5.5 years, that's a cost of $138 per year ($0.69 per Ah per year).

Cost of 3 new LifePO4 batteries, 100Ah each, is about $570. Because these can be routinely taken down to 20% SoC, the usable capacity is 240ah which is 20% greater than the 4 AGMs. Over 10 years, that's a cost of $57 per year ($0.24 per Ah per year).

As a bonus, 3 LifePO4 batteries weigh only 66 pounds compared to 251 for the 4 AGMs. That's 185 pounds that I won't have to lug around anymore.

An additional benefit is the significantly less steep discharge voltage curve. When LifePO4 battery reaches 50% SoC, the open circuit voltage drops to about 13.2. Compare that to an AGM battery that would be fortunate to measure 12.2.

So, LifePO4 wins in every category: initial cost, cost over usable life, weight, capacity, number of cable connections needed, and discharge voltage curve.
Unless there is a flaw in my math or logic, this is an absolute NO-BRAINER.



The only downside I can imagine is the lack of CCA. Each LifePO4 battery can deliver a maximum of 100 amps, (x3 = 300) where an AGM battery can give up to 1000 amps (x4 = 4000). This could possibly be an issue if the chassis battery is dead and the "Emergency Start" button is needed in really cold weather. I'll take my chances.

That’s great info, thanks. I’m convinced and LifePO4 house batteries upgrade is on the list.

[Chateau_Nomad]

Ignoring the benefits of LiFePO4 vs lead-acid batteries is like living in a world with bias ply tires and sealed beam halogen headlights... give it up folks, it's time.

[Lt Keefer]

Is a lithium battery a direct replacement? What else 'must' be done to convert to lithium?

[PS89]

Originally Posted by Lt Keefer

Is a lithium battery a direct replacement? What else 'must' be done to convert to lithium?

Nothing else "must" be done, it would work as-is although not optimally. However, it's a pretty good idea to replace 1) the stock WFCO converter in your rig with one that has a Li profile and 2) swap your BIM for a Li-BIM to manage the load on your engine alternator.

Just finished the above on my rig, now it's time to rip a whole lot of stuff out and re-do it MY way...

[DavidEM]

Originally Posted by Lt Keefer

Is a lithium battery a direct replacement? What else 'must' be done to convert to lithium?

Aha! That question results in two of the minor negatives to
Li batteries.

Unless you have a new RV you will have to replace the converter charger with a Li compatible one for best performance.

The other thing is the heavy load that the Li batteries can put on your chassis alternator that can overheat it and lead to failure.

There are two possible solutions. If you have a BIM 160 you can replace it with the Li-BIM225 or you can replace your BIRD/IRD with one. The other solution is a DC to DC charger to limit current.

David

[Mark54]

Originally Posted by DavidEM

Aha! That question results in two of the minor negatives to
Li batteries.

Unless you have a new RV you will have to replace the converter charger with a Li compatible one for best performance.

The other thing is the heavy load that the Li batteries can put on your chassis alternator that can overheat it and lead to failure.

There are two possible solutions. If you have a BIM 160 you can replace it with the Li-BIM225 or you can replace your BIRD/IRD with one. The other solution is a DC to DC charger to limit current.

David

What David said!
DCDC charger and new onboard LFP compatible converter, or change settings on existing. Check your manuals.
Costs for LFP batteries has come down a lot too. I paid $1900 for 600Ah (1x300A), but since I did mine, others have gotten the same batteries for much less.
If your 'draw' (amp usage) is the same, you can keep the same wireset.
If your solar controller has settings for lithium, make sure you change them.
Some inverter/converters have settings or DIP switches as well.
So be sure everything is LFP compliant!
No more cell fluid monitoring
Less weight
Better cycling/ usage
Safer than wet-cell or Li-ion- no off-gassing, won't light up, and have built in BMS for the most part.
Lighter too. Like having one less grown up riding along.
If you live in a cold climate like I do, then remove in the fall after winterising, and keep at 50-60% SOC, and every 3 mo.s charge to 100% and drop back to 50-60%
I use a 2000W I/C in my heated storage space to do this, and a small heater (750W) to draw down to storage spec.
Best lifespan (most cycles) is having at 20-40% to 80% SOC. So if you can find a battery manager to do that let us know.

My EV (VW ID4) has settings for that, but I am still looking for one to do the RV coach batteries.

[Chateau_Nomad]

Originally Posted by Mark54

What David said!
DCDC charger and new onboard LFP compatible converter, or change settings on existing. Check your manuals.
Costs for LFP batteries has come down a lot too. I paid $1900 for 600Ah (1x300A), but since I did mine, others have gotten the same batteries for much less.
If your 'draw' (amp usage) is the same, you can keep the same wireset.
If your solar controller has settings for lithium, make sure you change them.
Some inverter/converters have settings or DIP switches as well.
So be sure everything is LFP compliant!
No more cell fluid monitoring
Less weight
Better cycling/ usage
Safer than wet-cell or Li-ion- no off-gassing, won't light up, and have built in BMS for the most part.
Lighter too. Like having one less grown up riding along.
If you live in a cold climate like I do, then remove in the fall after winterising, and keep at 50-60% SOC, and every 3 mo.s charge to 100% and drop back to 50-60%
I use a 2000W I/C in my heated storage space to do this, and a small heater (750W) to draw down to storage spec.
Best lifespan (most cycles) is having at 20-40% to 80% SOC. So if you can find a battery manager to do that let us know.

My EV has settings for that, but I am still looking for one to do the RV coach batteries.

Looks like you have an Aims variant inverter/charger.

Our Chevy Bolt has an easily adjusted charge profile... just move a slider on the control screen. Tesla and other EVs have a similar interface.

If you have a computer/electronics background, an Arduino could be used to do exactly what you need. Basically program a date-based solution and configure a series of resistor circuits to control charge. The discharge cycle could even be built in to work automatically.

[Wiley1]

Originally Posted by PS89

... replace 1) the stock WFCO converter in your rig with one that has a Li profile and 2) swap your BIM for a Li-BIM to manage the load on your engine alternator.

I've got #1 covered with my 3000va Aimco inverter/charger, but I'd like to talk about #2.

I've had some issues with my chassis battery going dead when the rig is on shore power for extended periods. What do I need to buy? And, what's a BIRD?

[DavidEM]

BIRD stands for Bidirectional Isolator Relay Delay, a device made by Intellitec that connects or disconnects the house and chassis batteries depending on voltage. It consists of two parts, a control box and a solenoid. The solenoid is made by Trombetta so the two parts are often called a BIRD/Trombetta. IRD, an older system drops the bidirectional as it only allows charging one way.

Unfortunately the Trombetta solenoid is the weak link, and if yours has failed, replace it with a heavier one.

A more recent design is Precision Circuits BIM, Battery Isolation Manager which does much the same thing as the BIRD, but seems to be more robust. When RVers think that the BIRD isn’t working right, a simple switching of the chassis and house wires will solve it. This is entirely Thor’s fault as their wiring diagram has it backwards.

PC makes a Lithium specific version called the Li-BIM 225. It does much the same as the BIM 160 but it also cycles the chassis alternator/battery on and off 50% to limit alternator load which can burn up the alternator with the heavy charging load of Li batteries.

Wiley1: You may have a BIRD whose solenoid has failed or you may have an IRD that only charges the other way. The solution is to replace it with a BIM either the original or lithium version.

David

[Scubawise]

Originally Posted by DavidEM

Aha! That question results in two of the minor negatives to
Li batteries.

Unless you have a new RV you will have to replace the converter charger with a Li compatible one for best performance.

The other thing is the heavy load that the Li batteries can put on your chassis alternator that can overheat it and lead to failure.

There are two possible solutions. If you have a BIM 160 you can replace it with the Li-BIM225 or you can replace your BIRD/IRD with one. The other solution is a DC to DC charger to limit current.

David

Just bim 160 to bim 225 & leave original 2020 converter?

[DavidEM]

Originally Posted by Scubawise

Just bim 160 to bim 225 & leave original 2020 converter?

The old non Lithium converter will do a partial charge, but you need the higher voltage that a Li specific charger provides to fully charge Li batteries.

If you read my concurrent thread about a Li specific charger it seems darn difficult to find one. I suspect that the converter manufactures are just tweaking the voltage settings on their LA converters and calling them Li capable rather than redesign the electronics.

David

[16ACE27]

Originally Posted by DavidEM

The old non Lithium converter will do a partial charge, but you need the higher voltage that a Li specific charger provides to fully charge Li batteries.

If you read my concurrent thread about a Li specific charger it seems darn difficult to find one. I suspect that the converter manufactures are just tweaking the voltage settings on their LA converters and calling them Li capable rather than redesign the electronics.

David

Nope, the old converter will fully charge the LiFePO4 batteries, but won't keep them fully charged when it shifts to float mode.

[Wiley1]

Originally Posted by DavidEM

PC makes a Lithium specific version called the Li-BIM 225. It does much the same as the BIM 160 but it also cycles the chassis alternator/battery on and off 50% to limit alternator load which can burn up the alternator with the heavy charging load of Li batteries.

Wiley1: You may have a BIRD whose solenoid has failed or you may have an IRD that only charges the other way. The solution is to replace it with a BIM either the original or lithium version.

We like to run a bunch of AC & DC appliances while we're driving down the road including the fridge, 2 TV's, laptop chargers, phone chargers, dashboard media center, CD radio, SirusXM receiver, and even the microwave in short bursts. So far, the alternator has kept up nicely.

My coach is a 2017 Freedom Elite on an E450 chassis. Not sure what I've got for a BIM but I'm certain that is hasn't been replaced or upgraded since the vehicle was delivered. According to the Thor manual, it is a bi-directional device and they even show a picture of a BIM-225 that they call "typical". I suspect that is not what I have because it behaves like a uni-directional device that charges my house battery but ignores the chassis battery.

So, when I get my new Lithium batteries, all I need to do is get an Li-BIM 225 ($136 on Amazon) and all my issues will be solved?

Can somebody tell me where to look for my BIM? The Thor manual says to look in the "battery compartment" except my batteries are mounted under the stairs. Maybe under the hood?

What would happen if I installed 3 new LifePO4 batteries but did not change the BIM? Would that put my alternator at risk?

What would happen if I installed an Li-BIM 225 while I still have 4 AGMs connected?

[Scubawise]

Originally Posted by DavidEM

The old non Lithium converter will do a partial charge, but you need the higher voltage that a Li specific charger provides to fully charge Li batteries.

If you read my concurrent thread about a Li specific charger it seems darn difficult to find one. I suspect that the converter manufactures are just tweaking the voltage settings on their LA converters and calling them Li capable rather than redesign the electronics.

David

Great. That makes sense..

[DavidEM]

Answer to your last question first- Nothing bad would happen.

Second question:

It all depends on how many amps will be drawn and for how long. My guess is that 200Ahs of Li would be fine. Not enough current and not for long to hurt the alternator. 400 Ahs is marginal. 600+Ahs is likely to cook the alternator.

It is easy to measure the temp of the alternator and see if it is overheating. First run down the Li batteries to at least 75% SOC. Then start the chassis engine (with a working BIM of course). Shoot the alternator case with an IR gun at 15 and 30 minutes. If the temp is below 225F you are probably ok. Any higher than 225 and you are at risk of burning up the alternator.

First question. The BIM could be anywhere usually in the engine compartment.

David

[16ACE27]

Originally Posted by Wiley1

We like to run a bunch of AC & DC appliances while we're driving down the road including the fridge, 2 TV's, laptop chargers, phone chargers, dashboard media center, CD radio, SirusXM receiver, and even the microwave in short bursts. So far, the alternator has kept up nicely.

My coach is a 2017 Freedom Elite on an E450 chassis. Not sure what I've got for a BIM but I'm certain that is hasn't been replaced or upgraded since the vehicle was delivered. According to the Thor manual, it is a bi-directional device and they even show a picture of a BIM-225 that they call "typical". I suspect that is not what I have because it behaves like a uni-directional device that charges my house battery but ignores the chassis battery.

So, when I get my new Lithium batteries, all I need to do is get an Li-BIM 225 ($136 on Amazon) and all my issues will be solved?

Can somebody tell me where to look for my BIM? The Thor manual says to look in the "battery compartment" except my batteries are mounted under the stairs. Maybe under the hood?

What would happen if I installed 3 new LifePO4 batteries but did not change the BIM? Would that put my alternator at risk?

What would happen if I installed an Li-BIM 225 while I still have 4 AGMs connected?

If it is uni-directional you likely have an IRD.

https://intellitec.com/isolator-relay-delay/

[Chateau_Nomad]

Originally Posted by Wiley1

We like to run a bunch of AC & DC appliances while we're driving down the road including the fridge, 2 TV's, laptop chargers, phone chargers, dashboard media center, CD radio, SirusXM receiver, and even the microwave in short bursts. So far, the alternator has kept up nicely.

My coach is a 2017 Freedom Elite on an E450 chassis. Not sure what I've got for a BIM but I'm certain that is hasn't been replaced or upgraded since the vehicle was delivered. According to the Thor manual, it is a bi-directional device and they even show a picture of a BIM-225 that they call "typical". I suspect that is not what I have because it behaves like a uni-directional device that charges my house battery but ignores the chassis battery.

So, when I get my new Lithium batteries, all I need to do is get an Li-BIM 225 ($136 on Amazon) and all my issues will be solved?

Can somebody tell me where to look for my BIM? The Thor manual says to look in the "battery compartment" except my batteries are mounted under the stairs. Maybe under the hood?

What would happen if I installed 3 new LifePO4 batteries but did not change the BIM? Would that put my alternator at risk?

What would happen if I installed an Li-BIM 225 while I still have 4 AGMs connected?

Look on the driver's side... firewall area directly under/behind the coolant reservoir. I think there's three hex head screws holding the reservoir. Remove the screws and carefully tip the reservoir out of the way... no need to remove the rubber hose.

Your relay and controller will be mounted to the fender well. Take pictures of ALL wiring before removing!