Replacing lead-acid batteries with Lithium batteries

[SRDavis]

On my Isata 3 Ineed to replace my batteries due to failure of the existing batteries (cracked). I am considering replacing with lithium batteries. What is involved in that replacement? is is a simple swap or are there a lot of other systems that need to be changed out? Any guidance appreciated.

 

[bclemens]

there are several threads on this if you search the Dynamax sub-forum.

Right off the bat...
-Battery Monitor (standard voltage will not work. Victron Smart Shunt would)
-Converter charger is likely not set up for lithium. Some are as simple as a switch to change it.
-the device that charges the house batteries from the alternator is not set for lithium. (Forget what we used on 2018)

Someone else on there has done this exact swap as I recall.

Not all are totally necessary....but you won't see the full benefits of the lithium without them. They can charger faster and better with all components set up for it.

 

[Aussieguy]

unless you drive every day for around 4 -5 hours........... improving alternator charging for lifepo4 does not do lot of good.

adding some solar on the roof will help to keep the lifepo4 battery happy whether you drive or not.
you can still use the existing converter and allow the solar to FINISH the charging to 100%

a simple solar setup of around;
600-800w will allow good boondocking off grid and some INVERTER usage
200-400v will keep up with 12v usage (not great for inverter usage)

alternator ... if you want to use it the most popular ways are to get a DC-DC charger OR a Li- BIM
A good dc-dc would be best choice as it can increase the voltage going to the lithium batteries

change out the 120v converter is last in line as whenever you are plugged in your new battery will be getting charged.... once it is charged it will get maintained at 100% as long as you are plugged in
you can mooch dock at storage using just a 15 or 20amp outlet if one is available OR use solar

 

[TravelingSulls]

I did this on our 2018 Isata 5, easy to do.

First off is the BIM, you need to get one for Lithium. Below is the wire diagram for the Isata 5, not sure how it changes for the I3, I'm sure Brian could help with that. You will also need to change the settings in your solar controller as well as you inverter/charger.

Feel free to DM or contact me with more questions.

The BIM you will need.

Diagram with the BIRD, it's what I had, not sure what you have.

You need a diode on the ignition terminal (blue wire in picture), I have a few left over if you need one.

 

[Aussieguy]

only need a LI-BIM if you drive a lot
and It only works as you drive...

If you don't drive a lot just disconnect the original BIM by disconnecting the smaller control wires

You can Manually control the BIM ... nice cool morning/day with no traffic and batteries not really discharged ... it would be OK to turn on the BIM (allow alternator charging)

LI -BIM is just a BIM with a timer switches on/off the charging of the Lithium so alternator work get over worked.

with a half decent solar setup you can get the batteries almost full and therefore they won't be a big load on the alternator ... turn on alternator charging (BIM) near the end of your driving day if the solar has not fully re-charged them

NOTE Lifepo4 do not have to be fully charged to 100% every day

 

[SRDavis]

Thanks all for the replies and sharing knowledge. For now, I think I'm replacing them with the lead-acid originals. I need to study a bit more to make the move to Li.

 

[bclemens]

And as an FYI, the 3 series electrical and 5 series are totally different. a 2018 would not have the BIM or the Inverter/charger. It would have a solenoid in the step well, a small 1000 watt inverter, and a converter/charger.

 

[tewasch]

I converted my 2021 I3 last summer. I'm an electrical engineer, so it wasn't unfamiliar; but anything with an RV can be a mystery. Here's some background on things that were mentioned above....

You can swap-out the basic batteries with LiPO4 versions. In the existing stairwell, I have 610 amp hours (AHr) of capacity. The factory batteries offer 70? Ahr of capacity, so this is a huge upgrade (Lead Acid batteries don't like to be discharged farther than 50% where LiPO4 ones can use 100% each cycle without damage). LiPO4 batteries run a little higher in voltage than Lead Acid. They are more like 13.8V rather than 12V. You charge them at around 14.5V instead of 13V for Lead Acid. This little voltage difference is the source of all the remaining issues left to deal with. You can see that if you charge the new LiPO4 battery with a 13V charger, you won't get much charge in.

Therefore your charger needs to be LiPO4 compatible. In the 2021, this meant simply throwing a little DIP switch on the charge controller below the cooktop. If yours does not support the switch, you can simply buy a new charger module for that same power distribution box (from Amazon) and you'll be good to go in 5 minutes of replacement time. This will allow your 110VAC source to charge your batteries.

The next problem is that the way Lead Acid batteries are monitored for capacity is to simply measure the voltage of the battery. As it is drained, the voltage will drop from 12.5V down to 11.5V (rough numbers), and you can plot a line that translates that into fill level. This does not work on LiPO4 batteries. Happily, nearly regardless of fill level, the batter will still put out 13.2-ish volts. It is a very flat line so it cannot be used to estimate fill level reliably. Instead, there are ways to count the charge going in and out of a battery terminal to make a fill-level-meter. This is the SHUNT device that is mentioned. It is a device that sits in series with the electron flow in and out of the battery and simply keeps a count in and out and translates it to fill level. These are available on Amazon as well. I used a Victron one.

The next problem is charging your LiPO4 batteries from your sprinter alternator when driving. Alternators are, by default, setup for the Lead Acid charging voltage (some newer ones in newer Sprinter vans are a little more advanced and behave better with LiPO4 charging levels). As mentioned before, this is a little low for LiPO4 battery which would mean you might drive for hours, but you would never fill-up the battery. Further, an empty, large LiPO4 battery could draw A LOT OF CURRENT from an alternator causing it to heat up. A BIM (and a LiBIM) is a device that will connect the Sprinter's battery to the house battery when the house battery needs charging and the engine is running. The LiBIM includes timers to help reduce the problem of heat. This was not my choice. Instead, I used another Victron product that actually accepted the 12V Sprinter's battery voltage and DC-DC voltage converted it to the 14.5V charging profile of a LiPO4 battery. This device has a programmable current setting. This gave me the opportunity to both get a full charge and limit the heat/current I would draw from the chassis alternator.

Finally, there is the question of solar. It is not required. If you're going to drive a lot between stays, you could just use your alternator or plug-in (or generator) to charge your batteries. The 110VAC charger is around 60 Amps (840 Watts). The Alternator setup I have is rated at 50 Amps (that's 700 Watts). The battery capacity is 8,500 watts (in my case) so a half-full battery would charge by driving 6 hours. Putting solar on the roof gives you an independence from finding 110VAC somewhere or having to drive. Personally, I love having it. It also means that I NEVER have to worry if my battery is too low (or being damaged by over draining). Just sitting in my backyard, my RV keeps its battery charged (even in the winter shade). My Solar installation used 800W of CIGS solar panels (see Bougerv). My choice was driven by the fact that these were peel-and-stick to the roof and you can walk on them--so much better than screwing mounting brackets for hard solar panels. Driving down the road on a sunny day, I charge with both the alternator (700W) and the solar (another 700W) which means I can fill a half-drained battery in 3 hours.

Another thing I should mention is your Inverter. My rig came with a 2KWh inverter which is enough (if you're careful) to drive my air-conditioner/heat pump or my microwave oven for many hours. Honestly, we never plug in. You might consider swapping out your 1KWh one for a 2-3KWh one. This will mean you can warm-up your coffee in the morning without turning on your generator. Becky and I just got back from a Las Vegas trip. We camped in Mojave (Red Rock Canyon State Park) and at Circus-Circus (on the strip). We used battery to run our refrigerator and heated at night using the heat-pump. Virtually no propane used (except for hot water). We never started the generator and never plugged-in.

I would enjoy helping you understand each of these steps and guide you through you actions if you choose to take on this project. I chose a Victron DC-DC converter, Victron current SHUNT and Victron Solar MPPT charge controller. There are a little cheaper alternatives, but Victron is well-respected and they all share the same remote access via Bluetooth App on my phone.

Tom
Portola Valley, CA

 

[Aussieguy]

Good write up by tewasch

Add to this is to add a manual over ride onto the dc-dc so if your alternator is on the small side and you stuck in heavy traffic in death valley in the middle of summer you can turn off the dc-dc

until traffic improves or the solar has done enough charging that the BIG load has been reduced


Plus try get enough battery capacity to last about 3 days

 

[tewasch]

Thanks.... Yes, good point. The Victron DC-DC I bought can set the current limit in their phone app. So far I've never changed it. Its set to 50 amps. The Mercedes alternator is rated at 220 amps as I recall. I haven't really seen any impact to fuel consumption.

Capacity is an issue. Unfortunately, I still have the propane/AC fridge which is terribly inefficient when in electricity mode. Something like a 400 watt draw (when on) instead of a compressor based fridge which would be more like 65 watt draw (when on). This is what sucks-up my battery overnight. When this fridge dies I'll probably replace it with an all-electric setup.

 

[5picker]

Thanks.... Yes, good point. The Victron DC-DC I bought can set the current limit in their phone app. So far I've never changed it. Its set to 50 amps. The Mercedes alternator is rated at 220 amps as I recall. I haven't really seen any impact to fuel consumption.

Capacity is an issue. Unfortunately, I still have the propane/AC fridge which is terribly inefficient when in electricity mode. Something like a 400 watt draw (when on) instead of a compressor based fridge which would be more like 65 watt draw (when on). This is what sucks-up my battery overnight. When this fridge dies I'll probably replace it with an all-electric setup.

Why not run your refrigerator on LP?
There seems to be an awful lot of folks with all electric refrigerators (DC or AC) jonesing for a LP unit that uses a minute amount of battery.

 

[tewasch]

Its true. Even as I wrote my note I reconsidered it a bit. The LP fridge sips propane and lasts a long, long time on a tank. I'll never remove the propane as my cooktop and furnace (for really cold nights) still need it.

 

[Loghead-FRF]

I converted my 2021 I3 last summer. I'm an electrical engineer, so it wasn't unfamiliar; but anything with an RV can be a mystery. Here's some background on things that were mentioned above....

You can swap-out the basic batteries with LiPO4 versions. In the existing stairwell, I have 610 amp hours (AHr) of capacity. The factory batteries offer 70? Ahr of capacity, so this is a huge upgrade (Lead Acid batteries don't like to be discharged farther than 50% where LiPO4 ones can use 100% each cycle without damage). LiPO4 batteries run a little higher in voltage than Lead Acid. They are more like 13.8V rather than 12V. You charge them at around 14.5V instead of 13V for Lead Acid. This little voltage difference is the source of all the remaining issues left to deal with. You can see that if you charge the new LiPO4 battery with a 13V charger, you won't get much charge in.

Therefore your charger needs to be LiPO4 compatible. In the 2021, this meant simply throwing a little DIP switch on the charge controller below the cooktop. If yours does not support the switch, you can simply buy a new charger module for that same power distribution box (from Amazon) and you'll be good to go in 5 minutes of replacement time. This will allow your 110VAC source to charge your batteries.

The next problem is that the way Lead Acid batteries are monitored for capacity is to simply measure the voltage of the battery. As it is drained, the voltage will drop from 12.5V down to 11.5V (rough numbers), and you can plot a line that translates that into fill level. This does not work on LiPO4 batteries. Happily, nearly regardless of fill level, the batter will still put out 13.2-ish volts. It is a very flat line so it cannot be used to estimate fill level reliably. Instead, there are ways to count the charge going in and out of a battery terminal to make a fill-level-meter. This is the SHUNT device that is mentioned. It is a device that sits in series with the electron flow in and out of the battery and simply keeps a count in and out and translates it to fill level. These are available on Amazon as well. I used a Victron one.

The next problem is charging your LiPO4 batteries from your sprinter alternator when driving. Alternators are, by default, setup for the Lead Acid charging voltage (some newer ones in newer Sprinter vans are a little more advanced and behave better with LiPO4 charging levels). As mentioned before, this is a little low for LiPO4 battery which would mean you might drive for hours, but you would never fill-up the battery. Further, an empty, large LiPO4 battery could draw A LOT OF CURRENT from an alternator causing it to heat up. A BIM (and a LiBIM) is a device that will connect the Sprinter's battery to the house battery when the house battery needs charging and the engine is running. The LiBIM includes timers to help reduce the problem of heat. This was not my choice. Instead, I used another Victron product that actually accepted the 12V Sprinter's battery voltage and DC-DC voltage converted it to the 14.5V charging profile of a LiPO4 battery. This device has a programmable current setting. This gave me the opportunity to both get a full charge and limit the heat/current I would draw from the chassis alternator.

Finally, there is the question of solar. It is not required. If you're going to drive a lot between stays, you could just use your alternator or plug-in (or generator) to charge your batteries. The 110VAC charger is around 60 Amps (840 Watts). The Alternator setup I have is rated at 50 Amps (that's 700 Watts). The battery capacity is 8,500 watts (in my case) so a half-full battery would charge by driving 6 hours. Putting solar on the roof gives you an independence from finding 110VAC somewhere or having to drive. Personally, I love having it. It also means that I NEVER have to worry if my battery is too low (or being damaged by over draining). Just sitting in my backyard, my RV keeps its battery charged (even in the winter shade). My Solar installation used 800W of CIGS solar panels (see Bougerv). My choice was driven by the fact that these were peel-and-stick to the roof and you can walk on them--so much better than screwing mounting brackets for hard solar panels. Driving down the road on a sunny day, I charge with both the alternator (700W) and the solar (another 700W) which means I can fill a half-drained battery in 3 hours.

Another thing I should mention is your Inverter. My rig came with a 2KWh inverter which is enough (if you're careful) to drive my air-conditioner/heat pump or my microwave oven for many hours. Honestly, we never plug in. You might consider swapping out your 1KWh one for a 2-3KWh one. This will mean you can warm-up your coffee in the morning without turning on your generator. Becky and I just got back from a Las Vegas trip. We camped in Mojave (Red Rock Canyon State Park) and at Circus-Circus (on the strip). We used battery to run our refrigerator and heated at night using the heat-pump. Virtually no propane used (except for hot water). We never started the generator and never plugged-in.

I would enjoy helping you understand each of these steps and guide you through you actions if you choose to take on this project. I chose a Victron DC-DC converter, Victron current SHUNT and Victron Solar MPPT charge controller. There are a little cheaper alternatives, but Victron is well-respected and they all share the same remote access via Bluetooth App on my phone.

Tom
Portola Valley, CA

Tom, this is by far the best explanation for this very common question and I very much appreciate it. I just purchased a new LiTime 200A lithium battery to replace my 2 old 6-volt setup. All of our camping is boonddocking so this new lithium setup will help us immensely. I was planning on buying the compatible charger, monitor and shunt from LiTime. I planned on just running the charger from the AC coming from the camper and utilizing it when it is plugged in to shore power. I am definitely looking into your solar solution as well.

 

[tewasch]

Thanks. My wife says I should have been a college professor. Some of the batteries come with built-in BMS systems that offer bluetooth connectivity such that you can check battery fill level and currents in and out on your phone. This is a phone-version of a monitor that might be enough. I like a meter that Becky can read, so I went with the SHUNT as well. Good luck with the upgrade. You might look at the alternator charging as well. LiTime has a dc-dc converter as well (I helped a friend install it on his camper).

 

[TitanMike]

I chose a Victron DC-DC converter, Victron current SHUNT and Victron Solar MPPT charge controller. There are a little cheaper alternatives, but Victron is well-respected and they all share the same remote access via Bluetooth App on my phone.

Tom
Portola Valley, CA

Another feature beyond bluetooth monitoring, these victron devices, DC-DC converter and MPPT solar controller, have is remote voltage monitoring that controls their output voltage by what's read by the shunt at the battery. Not at their output terminals. This is accomplished by the VE Smart networking that connects shunt and both chargers via Bluetooth. Output voltage is then adjusted as necessary to overcome voltage drop over wires connecting them to battery bank.

Usually voltage drop is not a major issue but if chargers and batteries are separated by any distance it can affect where charging stages change to next in sequence.