Upgrading House Batteries to Lithium

[TheArthurs]

We are just about ready to pull the plug on replacing our house battery bank to LiFePO4. This will include the whole shebang...inverter, EMS and battery monitor.
Question is: Will we need to switch out our coach batteries as well? ie, we have 3 deep cycle LA coach batteries, do these need to be lithium as well?

Thanks

[Winterbagoal]

I've always referred to "house" and "coach" as being the same thing.
If you mean "chassis" batteries, the engine starting ones, it's up to you, and depends on the overall charging system setup. I've not heard of too many people using lithium iron phosphate batteries as starting batteries, but I suppose you could do it.
I've got an LA AGM starting/chassis battery, and 2 100Ah LiFePO4 Relions for my house/coach. Seems to be working OK.

[TheArthurs]

Originally Posted by Winterbagoal

I've always referred to "house" and "coach" as being the same thing.
If you mean "chassis" batteries, the engine starting ones, it's up to you, and depends on the overall charging system setup. I've not heard of too many people using lithium iron phosphate batteries as starting batteries, but I suppose you could do it.
I've got an LA AGM starting/chassis battery, and 2 100Ah LiFePO4 Relions for my house/coach. Seems to be working OK.

Ah, my bad LOL, thanks for your answer. Yes I was referring to my chassis batteries. Sounds like we can leave the engine battery bank alone and switch out only the coach bank.

[DeltaRome]

Originally Posted by TheArthurs

Ah, my bad LOL, thanks for your answer. Yes I was referring to my chassis batteries. Sounds like we can leave the engine battery bank alone and switch out only the coach bank.

i upgraded my 2 coach batteries on my 2020 View from flooded group 31 100 amp to 210 amps of LiFePO4 batteries from Renegy thru Costco.
These are built with internal BMS and are almost plug and play. I had to update the battery charger to the newer battery type but i already have a 2000 watt inverter and i installed a third solar panel so now have up to 300 watts of solar.
The chassis battery is designed for high amp draw over a short time and the LiFePO4 batteries are not suitable for this service. You should stay with flooded lead acid. Hope this helps.

[creativepart]

There is one thing you did not mention in your original post.

The LiPo battery companies like to refer to their batteries as "drop in replacements" for your current LA/AGM house batteries. But it's not exactly true.

The issue is that your alternator on your RV can be an issue. Most of the battery sellers will advise you do something to protect your alternator. Some take that advice and some don't but you should be aware of it.

The main workarounds I've seen for this are:

1. Put the charge line from the alternator on a switch so you can turn off charging the house batteries when driving - the chassis battery would still charge though. Of course, that means you won't be charging your house batteries as you drive your RV.

2. Put an BIM device between your house batteries and your alternator. This connects the alternator for a while, then disconnects it for a while, then turns it back on again.

3. Put a DC to DC charger between the alternator and your batteries. This takes the DC voltage from your alternator and applies smart charging rules to the process of charging the house batteries. You can control the charge rate and protect the alternator.

There is a 4th way and a number of people follow this way - and that's to do nothing. Just let the alternator charge as it wants to and worry about any problems latter. I guess there is a 5th alternative that even less people use and that's to add a special dedicated alternator made just for charging LiPo.

By the way, the problem is that your alternator is made to charge LA batteries and LA batteries naturally increase resistance to charging as they get closer to fully charged. But LiPo batteries don't do that so they can take more and more amps from your alternator and the end result is your alternator can over heat and be destroyed.

I think at present the DC to DC charger is the preferred way to protect the alternator and those expensive LiPo batteries. Though you'll find folks on all sides of this debate.

[DavidM]

Creativepart:

Good summary. I wonder, has anyone actually measured the current going to their Li house batteries with no device in between the battery and the chassis alternator and at various charge levels? And what happens with newer "smart" chassis alternators as well as the older fixed voltage type.

I would suspect in most cases the charging rate of the house batteries would be rather low. I think you need the B2B charger to present a low enough impedance to the alternator to fool it into thinking that the connected battery is well discharged to get serious current. And then the B2B will limit the current drawn by adjusting the impedance.

Or maybe Li batteries have a low impedance even if charging at relatively low voltages, ie 13.0 V that the alternator will produce lots of current. Don't know.

David

[TheArthurs]

Originally Posted by creativepart

There is one thing you did not mention in your original post.

The LiPo battery companies like to refer to their batteries as "drop in replacements" for your current LA/AGM house batteries. But it's not exactly true.

The issue is that your alternator on your RV can be an issue. Most of the battery sellers will advise you do something to protect your alternator. Some take that advice and some don't but you should be aware of it.

The main workarounds I've seen for this are:

1. Put the charge line from the alternator on a switch so you can turn off charging the house batteries when driving - the chassis battery would still charge though. Of course, that means you won't be charging your house batteries as you drive your RV.

2. Put an BIM device between your house batteries and your alternator. This connects the alternator for a while, then disconnects it for a while, then turns it back on again.

3. Put a DC to DC charger between the alternator and your batteries. This takes the DC voltage from your alternator and applies smart charging rules to the process of charging the house batteries. You can control the charge rate and protect the alternator.

There is a 4th way and a number of people follow this way - and that's to do nothing. Just let the alternator charge as it wants to and worry about any problems latter. I guess there is a 5th alternative that even less people use and that's to add a special dedicated alternator made just for charging LiPo.

By the way, the problem is that your alternator is made to charge LA batteries and LA batteries naturally increase resistance to charging as they get closer to fully charged. But LiPo batteries don't do that so they can take more and more amps from your alternator and the end result is your alternator can over heat and be destroyed.

I think at present the DC to DC charger is the preferred way to protect the alternator and those expensive LiPo batteries. Though you'll find folks on all sides of this debate.

Ah, great summary!! Thanks...i am going to be getting a bundled system through battleborn and I believe it includes something like what you describe as option 2 (BIM??what does this stand for?). But just to be sure, I am going to ask them specifically if they have something to protect my RV alternator.

[creativepart]

Originally Posted by TheArthurs

like what you describe as option 2 (BIM??what does this stand for?).

BIM is Battery Isolation Mananger.

Battleborn seems to go back and forth. First they promoted the BIM and then they switched to the DC to DC charger. And now I see them offering both and sometimes suggesting one, and then suggesting the other.

DavidM, Victron has a good YouTube video where they show the problem with LiPo charging via alternators. Their tests find that the alternator gets hot at any engine speed BUT that the internal fan on the alternator acts to cool the alternator but only at higher RPMs. So, their conclusion was that idling and slow speeds put the most stress on the alternator and can cause it to burn out.

They then show a specialized alternator with a regulator with a temperature sensor that lowers amperage as the alternator heats up. But this would require and expensive alternator replacement on an RV.

https://www.youtube.com/watch?v=jgoIocPgOug

[Winterbagoal]

I wonder if Winnebago does anything special to the alternator charging circuitry if someone chooses their Lithium battery option, instead of the standard GR31 AGMs in the newer Views and Navions? Or do they replace the standard MB 220A alternator with a special version that doesn't heat up?
Personally, I doubt it, but I wonder if anyone has had problems with charging them using, probably, the same alternator in both cases?
I have faith in the BMS to protect the batteries, and that the MB alternator is smart enough not to get overheated. I've only put 4,000 miles on my "plug and play" version of your options listed above. No additional hardwae added. In that stretch, no problems that I've noticed. But, it's only 4,000 miles.
If you want to get an opinion on Battle Born's recommendations and hardware, ask AJMike. He's followed their advice with his set up.

[creativepart]

Originally Posted by Winterbagoal

I wonder if Winnebago does anything special to the alternator charging circuitry if someone chooses their Lithium battery option,

That's a great question. Thing is... WBGO publishes almost no information about what all is included in the Lithium Option - just it's price.

[DavidM]

The Victron video was interesting. As you said lithium batteries can draw significant current from the alternator even at low alternator rpms to burn out the windings.

That tells me that you absolutely do need a current limiting device like a B2B charger to limit current from the alternator. A 40 amp Renogy B2B may have kept the stock alternator from overheating.

The video did not say anything about smart alternators on newer chassis like the Mercedes Sprinter. BTW the Balmar is not what I call a smart alternator. It's external regulator is smart enough to reduce the field current and therefore alternator current when the case gets too hot (180+F roughly) which is not what I call a smart alternator. But it is effective. Unfortunately I don't think the Mercedes and other smart alternators do that.

David

[Winterbagoal]

At around the 01:00 mark of the video, they admit that the 300Ah battery they're using to test has NO BMS. I wonder why that might be? Would a battery protected by the charge/discharge current limits enforced by a BMS, reduce the chances of a problem when using alternator charging? Again, I wonder why they would make that rather significant variation to what would be a typical real world setup?

[Winterbagoal]

Originally Posted by creativepart

That's a great question. Thing is... WBGO publishes almost no information about what all is included in the Lithium Option - just it's price.

That's why I asked, I bet there's nothing to tell.
It's probably the same alternator/isolator/charging set up for both.
Was hoping someone with a newer View/Navion with lithium would add some real world experience here.

[AJMike]

I think that one thing you need to keep in mind is how you use your RV. If you do a lot of dry camping/boondocking then you need to be concerned about keeping your Lithium batteries charged since you are probably using a lot of their power as you camp. If you usually stop at places where you have hookups your situation is different and your solution might be different as well.

We typically dry camp and/or boondock and we replaced our OEM batteries with BB Lithium for that reason. We also had a DC-DC charger installed at BB's suggestion since they recommended against a BIM. One thing I did at that time was insist that the installer add an on/off switch to the DC-DC charger so that I could turn it off if not needed, and that turned out to be a good idea.

We are now on one of our few hookup only trips since we are traveling in the southwest and it is August. We need air conditioning and that means shore power. What I found is that I don't even need the DC-DC charger on this trip. Our 300 watts of solar power keep the batteries at 100% when we are traveling and the shore power keeps them at 100% when stopped, so the on/off switch is off, and stays that way. The reason I mention this is that it might be worth while having an on/off switch installed if you add a DC-DC charger. You have no such option with a BIM.

[BobC]

Originally Posted by AJMike

I think that one thing you need to keep in mind is how you use your RV. If you do a lot of dry camping/boondocking then you need to be concerned about keeping your Lithium batteries charged since you are probably using a lot of their power as you camp. If you usually stop at places where you have hookups your situation is different and your solution might be different as well.

We typically dry camp and/or boondock and we replaced our OEM batteries with BB Lithium for that reason. We also had a DC-DC charger installed at BB's suggestion since they recommended against a BIM. One thing I did at that time was insist that the installer add an on/off switch to the DC-DC charger so that I could turn it off if not needed, and that turned out to be a good idea.

We are now on one of our few hookup only trips since we are traveling in the southwest and it is August. We need air conditioning and that means shore power. What I found is that I don't even need the DC-DC charger on this trip. Our 300 watts of solar power keep the batteries at 100% when we are traveling and the shore power keeps them at 100% when stopped, so the on/off switch is off, and stays that way. The reason I mention this is that it might be worth while having an on/off switch installed if you add a DC-DC charger. You have no such option with a BIM.

I'm not sure I understand the need for this. If your batteries are fully charged, they're not going to be drawing a charging voltage from the DC-DC charger, so why the need to turn it off?

[TheArthurs]

So helpful! Thank you, we will probably look into a doc to doc charger.

[BobC]

Originally Posted by TheArthurs

So helpful! Thank you, we will probably look into a doc to doc charger.

Renogy had several models, including one that has a built-in MPPT solar charge controller, which is a good idea if you're contemplating, or have solar.

https://www.renogy.com/products/battery-chargers/

I have the 20 amp DC-DC charger.

[TheArthurs]

Originally Posted by BobC

Renogy had several models, including one that has a built-in MPPT solar charge controller, which is a good idea if you're contemplating, or have solar.

https://www.renogy.com/products/battery-chargers/

I have the 20 amp DC-DC charger.

haha, i was just over there looking at this. Say, how do i know what 'size' Dc-DC charger to get??? The upgrade we are doing is 3-100Ah lithium batteries with a 3000w inverter.

[DavidM]

Originally Posted by TheArthurs

haha, i was just over there looking at this. Say, how do i know what 'size' Dc-DC charger to get??? The upgrade we are doing is 3-100Ah lithium batteries with a 3000w inverter.

You don't want to put too much load on your chassis alternator. Mercedes recommends no more than 40A external load from the Sprinter alternator. Other engines particularly the Cummins 8.3 can pull more.

How much solar capacity do you have or are you planning to add. The Renogy controller shares its amp rating between the solar panels and the chassis alternator input with solar having preference.

Renogy makes up to a 40A and Victron up to a 60A I believe.

David

[AJMike]

Originally Posted by BobC

I'm not sure I understand the need for this. If your batteries are fully charged, they're not going to be drawing a charging voltage from the DC-DC charger, so why the need to turn it off?

Over the last couple of months I have come to agree with a post saying that running the DC-DC charger applies too high a voltage to the starter battery and that continued use of it will eventually shorten its life span. Not by a lot, perhaps, but by some. Given that I have come to agree with this I decided I did not want to run it when I did not need to. Added to that, of course, is the knowledge that the charger will put additional stress on the alternator when it (the charger) is running.

You are right when you say that the DC-DC charger will not output a charge if the battery is fully charged, but as we drive the normal electronics and the compressor refrigerator discharge the batteries enough for the DC-DC charger to begin outputting a charge again. If there is a lot of sun, then perhaps not much will be applied, but if it is overcast and there is little solar, but I know I will be stopping and using shore power, then I make sure the charger is off and allow the batteries to discharge down to 85-90% knowing that they will fully charge from shore power.

In short, if I am dry camping or boon docking, then I run the charger and let the chassis battery take care of itself. If I am going from hookup to hookup then I leave the charger off and take care of the chassis battery myself.