Replacing Sunova House Batteries With Lithium

[Tim Nadaud]

Hello, I have 2004 Itaca Sunova 27C, Workhorse chassis P32, Vortec engine. My Bat configuration is 2 Lead A house batteries, and one engine cranking Lead A battery. Recently my house batteries died. So, my question is: could I replace my two house batteries with one Lithum battery connected in parallel? Any info would be greatly appreciated. Tim

 

[SMH2026]

T,

So if I understand you have 2 lead acid batteries in parallel that have failed. You can replace the lead acid units with Lithium battery(s). Add up the total ampacity of the house batteries, so if you have one lead battery that stores 300 amps, 2 units in parallel would be additive so you would have 600 amps at 12 VDC. Lead acid batteries do not like a depth of discharge (DOD) greater than 50% or their useful life is shortened. You can install 1 Lithium battery at 600 A and 12 VDC or 2 x 300A 12 VDC Lithium batteries in parallel that will give you 600 Amp/hours at 12 VDC. Lithiums can safely discharge to about 10-20% state of charge (SOC), you can go lower if the BMS (battery management system) allows it. However at 10% SOC you would get 270 Ah from one battery or ~ 540 Ah from 2 units in parallel. However, I'd highly recommend a 100A fuse at each battery to protect your rig. Lithium units can supply SERIOUS current so a fuse at each battery helps protect your rig. Upgrading to Lithium will give you more useable power because they can be discharged to a lower SOC than lead acids without damage but you need to add some protection (fuses) at each unit. I do not recommend direct current circuit breakers. Fuses by definition are better at this job.
Lithiums do not like the cold, if you live in northern latitudes take appropriate precautions to prevent low temperature exposure and resulting damage.

Hope this helps,
SM

 

[Tim Nadaud]

T,

So if I understand you have 2 lead acid batteries in parallel that have failed. You can replace the lead acid units with Lithium battery(s). Add up the total ampacity of the house batteries, so if you have one lead battery that stores 300 amps, 2 units in parallel would be additive so you would have 600 amps at 12 VDC. Lead acid batteries do not like a depth of discharge (DOD) greater than 50% or their useful life is shortened. You can install 1 Lithium battery at 600 A and 12 VDC or 2 x 300A 12 VDC Lithium batteries in parallel that will give you 600 Amp/hours at 12 VDC. Lithiums can safely discharge to about 10-20% state of charge (SOC), you can go lower if the BMS (battery management system) allows it. However at 10% SOC you would get 270 Ah from one battery or ~ 540 Ah from 2 units in parallel. However, I'd highly recommend a 100A fuse at each battery to protect your rig. Lithium units can supply SERIOUS current so a fuse at each battery helps protect your rig. Upgrading to Lithium will give you more useable power because they can be discharged to a lower SOC than lead acids without damage but you need to add some protection (fuses) at each unit. I do not recommend direct current circuit breakers. Fuses by definition are better at this job.
Lithiums do not like the cold, if you live in northern latitudes take appropriate precautions to prevent low temperature exposure and resulting damage.

Hope this helps,
SM

SM, thank you for the in depth response. Tim.

 

[Morich]

Be aware that the combo of lead acid and lithium is far more complex than first thought. Do NOT simply tie them together without considering several of the main factors!
A couple big things to consider is that the two have far different float voltages. For simple talk we might define float as the fully charged voltage? That means that when you connect both to the same charge source, you need to consider how to get the lithium fully charged without boiling the lead acid? Also the lithium are prone to taking a charge current that can overheat the engine alternator while driving. Something to consider when designing the system to avoid burning up the alternator!
There are a number of small points and each person has to decide what they want to do, so I find no single answer will fit all of us. First step may be what level of expense we each feel worthwhile. I have never gone to lithum because the gain was not worth the effort and expense for my current use. We rarely go without hookups for more than a single night, so find no big advantage that makes the extra work and large expense worthwhile!
First step might be to find what the current RV converter does for charging a lithium. In RV built before lithium became common, many will not charge the lithium to fully charged voltage, so part of the advantage is not going to happen. That is part of the decision for each. Is it worthwhile to pay the premium for lithium batteries and not fully charge them, or does it fit to change out the converter for a new one with options for charging to the higher voltage as well as add the equipment to avoid overheating the engine alternator?
Way deep subject that can't be fully discussed in any single post as there are many variables involved! I looked it over and decided it not worth it for me. But my first word of advise is to not take the first bit of info you find without checking!
A search of this forum alone will turn up dozens of posts on the very deep, very confusing subject!

 

[Morich]

Quick look at what was built on your RV when new?
This is part of what you may need to deal with when swapping to lithium?

Your RV came built with this mode solenoid which acts to automatically tie your chassis 12V start battery together with the 12V coach batteries as we drive. Turn the key and start the engine and wire LR gets 12v to close the contacts in the solenoid. That ties the "truck" part of the electrical sytem to the coach part! That lets us recharge the coach batteries we may have drawn down while camped. Works good---most of the time!
But consider what may happen if we have a couple lithium batteries as coach power and we draw them way down like they are really good at doing? Say we get them even as low as 10 volts, which does not harm them? Then when we start the engine and it connects the alternator and lead acid chassis battery together with two lithium that are really good at charging at a high current level and needs to go to 14. 6 volts for full charge while the lead wants to stop and float at around 12.8?
Or the opposite can be true when having camped if you have changed the converter to newer which charged the lithium to 14.6? Start the engine and it finds you've tied the 12V lead system to that 14.6?
Kind of like hitching a motorcycle to a bicycle as a team? It can be done but it takes some thought!
Very easy to overwork the alternator, or not get the full value out of the semi-charged lithium!
Beware the quick and easy answer!

 

[Tim Nadaud]

Be aware that the combo of lead acid and lithium is far more complex than first thought. Do NOT simply tie them together without considering several of the main factors!
A couple big things to consider is that the two have far different float voltages. For simple talk we might define float as the fully charged voltage? That means that when you connect both to the same charge source, you need to consider how to get the lithium fully charged without boiling the lead acid? Also the lithium are prone to taking a charge current that can overheat the engine alternator while driving. Something to consider when designing the system to avoid burning up the alternator!
There are a number of small points and each person has to decide what they want to do, so I find no single answer will fit all of us. First step may be what level of expense we each feel worthwhile. I have never gone to lithum because the gain was not worth the effort and expense for my current use. We rarely go without hookups for more than a single night, so find no big advantage that makes the extra work and large expense worthwhile!
First step might be to find what the current RV converter does for charging a lithium. In RV built before lithium became common, many will not charge the lithium to fully charged voltage, so part of the advantage is not going to happen. That is part of the decision for each. Is it worthwhile to pay the premium for lithium batteries and not fully charge them, or does it fit to change out the converter for a new one with options for charging to the higher voltage as well as add the equipment to avoid overheating the engine alternator?
Way deep subject that can't be fully discussed in any single post as there are many variables involved! I looked it over and decided it not worth it for me. But my first word of advise is to not take the first bit of info you find without checking!
A search of this forum alone will turn up dozens of posts on the very deep, very confusing subject!

Quick look at what was built on your RV when new?
This is part of what you may need to deal with when swapping to lithium?
View attachment 2506605
Your RV came built with this mode solenoid which acts to automatically tie your chassis 12V start battery together with the 12V coach batteries as we drive. Turn the key and start the engine and wire LR gets 12v to close the contacts in the solenoid. That ties the "truck" part of the electrical sytem to the coach part! That lets us recharge the coach batteries we may have drawn down while camped. Works good---most of the time!
But consider what may happen if we have a couple lithium batteries as coach power and we draw them way down like they are really good at doing? Say we get them even as low as 10 volts, which does not harm them? Then when we start the engine and it connects the alternator and lead acid chassis battery together with two lithium that are really good at charging at a high current level and needs to go to 14. 6 volts for full charge while the lead wants to stop and float at around 12.8?
Or the opposite can be true when having camped if you have changed the converter to newer which charged the lithium to 14.6? Start the engine and it finds you've tied the 12V lead system to that 14.6?
Kind of like hitching a motorcycle to a bicycle as a team? It can be done but it takes some thought!
Very easy to overwork the alternator, or not get the full value out of the semi-charged lithium!
Beware the quick and easy answer!

Morich, Thank you for the in-depth info. The cost and what is involved does not justify the switch to lithium. Tim

 

[Morich]

Different thought and where I wound up was sticking to lead acid type but built different? Deep cycle batteries do charge the same as they are still lead acid, just different build on lead plates, etc. to let us discharge them far more like if we use them for trolling motors for fishing. Thay can be found reasonably cheap but last better for deeper discharge and do still recharge the same as start batteris.
But, again it is a question of what and how much we each feel worth the effort!

 

[RV_Lee]

https://rvjournal.org/how-to-swap-your-rvs-lead-acid-batteries-for-lithium-a-plain-english-guide/

 

[EverettO]

Hi Tim! I did that on my 2008 Itasca Sunova 26P. But I replaced the two 6v batts with TWO 100Ah 12v lithium batteries, and it has worked very well. Enough room under the step! I discovered the on-board convertor/charger could be jumpered to accommodate the increased peak voltage of the new batteries, so I did not have to replace it. Mine had probably been replaced at some point by a prior owner, so check yours. It literally took 5 mins to set it for lithium! I was going to install a LBIM (https://amzn.to/4xhDsO0) to protect my alternator, but then I found that companies like Battleborn indicate this is really not needed unless you are charging 3+ lithium batteries. Have been running on this for a 18 mos or so, and I am very happy with this. I also replaced my single 100w solar panel with a 385 residential panel (got cheap on Marketplace) and upgraded the solar charge controller (to this Amazon.com) to handle the extra juice from the panel. Works great! Reach out if you need pics or something!

 

[Morich]

It does certainly get less expensive to do the change if the converter has already been upgraded at some point, but that is also part of what makes the decision more difficult as we may not know what those changes involved! If we have an RV that has had major changes, my first move is to check how and what was done as there are certainly some very WRONG ways to do things!
When I was into swapping and changing RV, I quickly learned to shy away from those which had been "improved" by previous owners. With all the possible changes I see on battery supply being done, I no longer consider those as they are full of ticking time bombs that I do not want to get near!
For a quick headache, how much do we trust a battery saleman's word on what happens to our alternator? Do we get a guarantee on that ?
It only takes me less than a minute to walk away from that RV!

 

[EverettO]

Thanks Morich!. The OP has already bought the motorhome, so this isn't a buying decision. But knowing what is and isn't already in the rig is important. BTW, Battleborn (makes and?) sells the LBIM module, so I felt their recommendation against adding it was pretty good evidence it wasn't required. The argument was that the max or likely draw from a discharged group of 1 or 2 lithium batteries would not be sustained at a high enough level for long enough to damage the OEM alternator. That equation changes if you have three discharged lithium batteries all pulling lots of power. But you probably know more way more than I do about such things. I have only a baseline knowledge.

 

[7997redtail]

I'm just in the process.

I bought a new house charger to charge the lipo4 while I'm on shore power. It's located by the door and is part of the 110vac/12vdc panel. If you take the front cover off and a bottom panel you'll see it in there. Make sure you've disconnected from all power sources. You'll be dealing with both AC and DC.

My RV is a 2008 and the original charger is not set up for lithium and that's why I need to change it out. You can charge on the original but the lithiums will not get a full out proper charge.

Here is a link to what I've found out and decided to do in regards to protecting the alternator.

LiFePO4 DC-DC Charger Wiring and Battery Boost

I think I've looked at enough posts and electrical drawings to choke an elephant. That doesn't really make any sense but I'm shaking my head trying to figure this out. I'm switching to LIPO4 lithium batteries and I'm trying to figure out the best way to hook in the DC-DC charger/alternator...

www.winnieowners.com

The attachment is in the other post but I've put it here as FYI.