AMG to LiFePo4 ?

[Whynot]

Can the Stock AGM battery replaced to one LiFePo4 100Ahbattery by a simple swap in a 2018 Simplicity SRT with an underhood generator (or UHG as some say)

[gregmchugh]

Originally Posted by Whynot

Can the Stock AGM battery replaced to one LiFePo4 100Ahbattery by a simple swap in a 2018 Simplicity SRT with an underhood generator (or UHG as some say)

Where is the AGM located? If inside the van then you can use that location for the lithium. If under the van then you need to worry about low and high temperatures along with the mounting if it is not compatible with the lithium.

Assuming the inverter/charger, solar controller, and Balmar regulator for the under hood generator have charge profile options that are acceptable for the drop in lithium then it is an easy swap after you set the correct charge profiles.

[Whynot]

The battery is under the chassis at the original location. Thanks for the quick replay.

[hbn7hj]

Those that were going to do that quit posting. If you are going to travel in freezing weather you shouldn't do it without battery heaters. I think we have all decided that lithium batteries need to be inside for climate control.

[gregmchugh]

Originally Posted by hbn7hj

Those that were going to do that quit posting. If you are going to travel in freezing weather you shouldn't do it without battery heaters. I think we have all decided that lithium batteries need to be inside for climate control.

Option 1 - Lithium batteries within the heated space of the van. In the case of Winnebago they are heating the batteries that are mounted below the floor using ducted air so I guess you can consider that within the heated space of the van.

Option 2 - Lithium batteries mounted outside the heated space of the van with battery heating pads to keep the cells above the minimum temperature for operation (charging and discharging). Inactive cells below operating temperate but above minimum storage temperature would be warmed before operation.

In both cases when in storage the cells must be kept above the minimum storage temperature limit.

[Whynot]

Thank you all. Probably will stay with the AGM and increase the size as well as adding a second battery. So far for overnight camping and using the 120W suitcase solar I was good. I am thinking of a 2-3 day dry camp may need a bigger capacity to start wilth as solar will maintain it but probably not fully charge it w/ fridge running.

[JML]

I put a LiPo in the outside battery compartment of my 2013 Pleasure Way Excel. (The back of the tray had to be cut to accommodate the battery.) I keep the RV outside in a covered port - lowest temp in the coach recorded this winter was 11 degrees. I charged it up prior to winterizing and turned the battery off. It stored fine and was in perfect health when the temps warmed up and we took her out. We didn't charge it when it dropped below freezing so we had no problem. I highly recommend the LiPo - it is a 100Ah and I use a 100 watt solar suitcase to top it off camping.

[eric1514]

Originally Posted by JML

I put a LiPo in the outside battery compartment of my 2013 Pleasure Way Excel. (The back of the tray had to be cut to accommodate the battery.) I keep the RV outside in a covered port - lowest temp in the coach recorded this winter was 11 degrees. I charged it up prior to winterizing and turned the battery off. It stored fine and was in perfect health when the temps warmed up and we took her out. We didn't charge it when it dropped below freezing so we had no problem. I highly recommend the LiPo - it is a 100Ah and I use a 100 watt solar suitcase to top it off camping.

Exactly. I don't understand the admonition that says Lithium batteries need to be mounted inside the coach. Other than storing them charged, a well designed BMS should prevent them from charging when it's too cold.

[booster]

Originally Posted by eric1514

Exactly. I don't understand the admonition that says Lithium batteries need to be mounted inside the coach. Other than storing them charged, a well designed BMS should prevent them from charging when it's too cold.

Many of the lithium batteries also have a cold storage limit of -4*F, so that can knock out a lot of the country. Of course having them inside the van only works for a while until it gets too cold inside, but if you were to go on a cold winter ski trip, outside ones could also get too cold.



If you have a a BMS that shuts down charging below freezing, and it appears some of the drop ins don't do that, you also need to have a method of heating the batteries up to charge temp. If they are outside that means heaters and way to power them. Lots of us have seen under freezing in our travels, and would need to be able to charge the batteries.

[markoch]

On the Simplicity with the Under hood generator I think the built in regulator is not set up for LiFePo. Also if you remove the AGM load and your BMS disconnects the LiFePo for some reason you will damage the alternator I thought. So a few issues to address.

[booster]

Originally Posted by markoch

On the Simplicity with the Under hood generator I think the built in regulator is not set up for LiFePo. Also if you remove the AGM load and your BMS disconnects the LiFePo for some reason you will damage the alternator I thought. So a few issues to address.

The charging control for full shutoff by a BMS is the hardest part of the lithium swap for most applications, I think. That is probably why most of the drop ins tell you to float them instead. Of course that totally blows up the idea of an easy swap by just having the BMS shut stuff off.


As mentioned here disconnecting under load so no battery reference is not good to do. You would also need a battery reference to get the charging equipment to come back on line and if you are in cold lockout they won't have that.



It is much more complicated than the drop in battery sellers would indicate, unless you ignore the now pretty common rules about charge, use, and storage temps and the full shutoff charging.

[RossWilliams]

Eric -

I think some people want to use their RV in cold weather, so being able to get it above freezing is important.

The other thing is if you drive it in very cold, sub-zero, weather you may damage a battery. My understanding is that getting a lithium battery down below -4F may damage it. Where I live -4F can be the high temperature for a week or two. An exposed battery outside the coach is going to get to that ambient temperature pretty quickly.

[eric1514]

Originally Posted by booster

The charging control for full shutoff by a BMS is the hardest part of the lithium swap for most applications, I think. That is probably why most of the drop ins tell you to float them instead. Of course that totally blows up the idea of an easy swap by just having the BMS shut stuff off.


As mentioned here disconnecting under load so no battery reference is not good to do. You would also need a battery reference to get the charging equipment to come back on line and if you are in cold lockout they won't have that.
...

Let's say in my case, the alternator would also be charging the chassis battery and that battery would always be connected, would that eliminate the danger to the alternator of disconnecting the coach batteries?

[booster]

Originally Posted by eric1514

Let's say in my case, the alternator would also be charging the chassis battery and that battery would always be connected, would that eliminate the danger to the alternator of disconnecting the coach batteries?

If you are charging off a common system that has another battery in the system you will be able to disconnect the alternator from the coach safely. Most of the high charger rate systems needed for lithium batteries aren't set up that way, and use standalone high output alternators, in factory and non drop in aftermarket setups. Many of the newer vehicles, like Sprinters has some strict rules about pulling off more than a small amount of power.

One thing we don't know right now is how the drop in batteries are going to do over time current limiting. You can get into a situation where some of the drop ins want lower current that an is available, but how to do that is not all that easy currently unless you use a 12v to 12v charger.

Of course, your solar and coach systems would also have to wired into van starting battery systems so they would activate and you would need the controls necessary to shut them off and on properly. Solar in particular can be an issue as they want you to always have battery in the system if the solar panels are seeing any sunlight. The problem is that if the panels are putting out power to an unreferenced controller, there is no voltage regulation and big spikes can occur when the controller is activated. Normally, the panels would be shut off first then the controller, and the opposite when turned back on.

The issue of battery reference would be in making sure the starting battery was in the system whenever you were not running the engine but where on shore power or solar in case the BMS shuts down the charging from them. It would also be needed to be able to connect the van battery and system to a cold or other BMS shutdown to run heaters or just to get the other charging sources online.

A lot of the risk of these systems is based on if and how often a BMS shutdown would occur, especially with a manual switching setup for three charging sources.

You need to decide if floating the lithium batteries is acceptable or not as that is about the only way you would be able run a drop in battery into a older system. That choice gets down to a who do you believe type thing, as the cell and system manufacturers mostly say don't float lithium, but the drop in sellers say it is no issue. With a small system if you do full shutoff of charging, you will have to recharge much more often compared to if you are on shore power and floating the system as all use would come out of the batteries. Systems with full shutoff of charging get very much more complex than floating, as in the comments above.

[eric1514]

Originally Posted by booster

If you are charging off a common system that has another battery in the system you will be able to disconnect the alternator from the coach safely. Most of the high charger rate systems needed for lithium batteries aren't set up that way, and use standalone high output alternators, in factory and non drop in aftermarket setups. Many of the newer vehicles, like Sprinters has some strict rules about pulling off more than a small amount of power.

One thing we don't know right now is how the drop in batteries are going to do over time current limiting. You can get into a situation where some of the drop ins want lower current that an is available, but how to do that is not all that easy currently unless you use a 12v to 12v charger.

Of course, your solar and coach systems would also have to wired into van starting battery systems so they would activate and you would need the controls necessary to shut them off and on properly. Solar in particular can be an issue as they want you to always have battery in the system if the solar panels are seeing any sunlight. The problem is that if the panels are putting out power to an unreferenced controller, there is no voltage regulation and big spikes can occur when the controller is activated. Normally, the panels would be shut off first then the controller, and the opposite when turned back on.

The issue of battery reference would be in making sure the starting battery was in the system whenever you were not running the engine but where on shore power or solar in case the BMS shuts down the charging from them. It would also be needed to be able to connect the van battery and system to a cold or other BMS shutdown to run heaters or just to get the other charging sources online.

A lot of the risk of these systems is based on if and how often a BMS shutdown would occur, especially with a manual switching setup for three charging sources.

You need to decide if floating the lithium batteries is acceptable or not as that is about the only way you would be able run a drop in battery into a older system. That choice gets down to a who do you believe type thing, as the cell and system manufacturers mostly say don't float lithium, but the drop in sellers say it is no issue. With a small system if you do full shutoff of charging, you will have to recharge much more often compared to if you are on shore power and floating the system as all use would come out of the batteries. Systems with full shutoff of charging get very much more complex than floating, as in the comments above.

Thank you. That was a great explanation. There certainly are a lot of contingencies to consider if you want to do it right. In a few years I'll probably be needing to replace my AGMs and it's temping to drop in something else.

I wonder if we're being overly cautious or underestimating the robustness of the drop-in batteries or their BMSs. People are truly just replacing their batteries and nothing else. One fellow on facebook in the Travato group is putting Battleborns in other peoples' coaches sometimes alongside the factory AGMs and telling folks to just push the button on their PD chargers to boost (14.4v). I think that's crazy, but their must be some middle ground.

[booster]

Originally Posted by eric1514

Thank you. That was a great explanation. There certainly are a lot of contingencies to consider if you want to do it right. In a few years I'll probably be needing to replace my AGMs and it's temping to drop in something else.

I wonder if we're being overly cautious or underestimating the robustness of the drop-in batteries or their BMSs. People are truly just replacing their batteries and nothing else. One fellow on facebook in the Travato group is putting Battleborns in other peoples' coaches sometimes alongside the factory AGMs and telling folks to just push the button on their PD chargers to boost (14.4v). I think that's crazy, but their must be some middle ground.

You are exactly right, there is a huge gap between what integrated new systems do and what the drop in suppliers say you can do. Everything from charge profile, temps allowable, charge rates, etc all have conflicts between them.

We do know that Roadtrek and ARV both started out with drop-ins before they went to integrated systems. Both got out of them quite quickly, but we have never heard details of why.

Personally, and not with any proven testing, I am skeptical that it can be as simple as just drop in and replace AGM or wet cells. If it were, I can't imagine that the systems would have such accurate and expensive controls on them for competitive reasons. Another, totally opinion, thing is the way many of the drop ins are marketed. I don't know if any of it has been fixed, but the Battleborn site was full of mistakes, inaccuracies and exaggerations in their specs and comparisons, and the layout and verbage sounded like an infomercial. They are made by Firefly, which has been around for a long time and was much more of a mainstream supplier with very accurate literature and claims, from what I remember, so this is a change for them.

What it may all come down to is that the drop-ins could not last as long or perform as well as the integrated systems, but the cost/benefit may still be there, especially if they can get the price down.

Time will tell if they come close to what is promised, as it will take quite some time to get even half way there. Likewise it will be interesting to see if we start to hear of multiple failures in the desert or frozen north, as those could be the most likely issues to cause rapid damage. I would guess charging profile and floating issues would be a slower degradation if there is a problem. Fellows like the Facebook one you mention may accelerate how quickly we start to find out things, be it good or catastrophic.

[RossWilliams]

" I think that's crazy, but their must be some middle ground. "

Lets say its not optimum. But optimum solutions may be both initially more complicated, expensive and/or overkill. If your goal is adequate power for your summer vacation this year, then a lot of the details aren't all that important. On the other hand, if you are going to full time on a limited budget for the next five years, optimizing for cost and lifespan of the system may be very important. And even then, you will find multiple opinions on how to best achieve it and what is worth the cost.