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Battery Isolator with Lithium and Lead Acid Connections

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Don’t Keep Lithium Batteries Directly in Line With Your Lead Acid

As lithium ion technology is becoming more readily available our team has noticed an outpour of questions. These are in regards to interconnecting lead acid and lithium ion battery banks. As pioneers in this field, Battle Born Batteries is the go-to resource for lithium tech and battery safety.

Why Different Battery Chemistries Don’t Mix

For battery safety, we do not recommend combining different types of lithium batteries and lead-acid batteries. This is because the load characteristics and capabilities of these batteries are drastically different which can lead to safety issues. Due to this, do not directly combine these batteries in parallel or series.

Our team of experts at Battle Born Batteries does not recommend that you ever mix batteries’ chemistry, or battery types. Doing so can be detrimental to your system in a number of ways. You run the risk of irreparably damaging your electrical system an can create a variety of electrical hazards.

Mixing battery types and chemistries can  lead to a multitude of issues. Across assorted brands of lithium, we do not recommend ever mixing brands because of the BMS (Battery Management System). Our BMS protects the battery from several potentially damaging scenarios. This ensures battery safety, by verifying the user and battery are not put into precarious situations.

Some of these scenarios include:

  • High/Low voltage protection
  • Short Circuit Protection (One time only)
  • High/Low Temperature Protection
  • Cold Charging Protection
  • Automatic Cell balancing

Danger Zone Without a Battery Isolator

Even though both battery types are classified as a 12V battery, a lead-acid battery sits at a nominal voltage of 12.6V while on the other hand, our lithium batteries sit at a nominal voltage of 13.6V.  The voltage difference of the two batteries, combined with the internal BMS within the lithium and lack of BMS within the lead-acid can create a variety of concerns for the health of your batteries and safety of your system.

When batteries are not at the same voltage or discharge at mismatched rates, the power flows quickly between them. When this happens, this creates heating issues within your system arise which can damage your batteries and onboard components.

Both lithium batteries and lead-acid batteries are rechargeable energy storage batteries, but they have very different characteristics. Without proper components in line to separate the two, the batteries cannot be used in conjunction. Please note that these components must meet the technical requirements, including protective measures.

As a result of the previously mentioned differences, our team strongly suggests you do not tie your lithium battery bank directly to your lead-acid batteries.

When to Connect Your Battle Born Batteries and Lead Acid Batteries

When you are looking to interconnect your lithium-ion batteries with your lead acid batteries, the only method we recommend  is with a battery isolator or DC to DC charger in line between the two. The most common application of this set up is for alternator charging. As you may be familiar with, to be able to successfully charge your lithium battery house bank while driving you will have to connect it to your alternator and starting battery setup. Please keep in mind that Battle Born Batteries should not be used for cranking applications such as turning over the engine, and you will need to keep your lead acid starting battery in place.

To be able to charge your lithium house bank you will need to place a battery isolator or DC to DC charger in line between the starting battery and your house bank. These components will separate the two battery chemistries and allow for a proper charge to go to your lithium house bank.

Charging Parameters for Chargers and Battery Isolators

In addition to the voltage difference, lithium is also capable of charging and discharging much faster than lead acid. As a result of these differences, lithium has a very specific charging profile that must be met by your charger. You will want to confirm your current charger is able to fully and properly charge your lithium batteries. Chargers can vary from one to three stage charging profiles depending on the make and model. Most of the time you are able to reprogram your existing chargers to match our batteries’ charging profiles. Below are some of the common settings you may see and our suggested charging parameters for your Battle Born Batteries.

  • Bulk: 14.2-14.6V
  • Absorption: 14.2-14.6V
  • Absorption Time: 30 min per battery
  • Float: 13.4-13.8V
  • Equalization: Disable if possible or set to 14.4V
  • Charging Current: 50A per 100Ah of battery

Connecting Your Battle Born Batteries and Lead-Acid Bank with a Battery Isolator

To ensure battery safety, you need an isolating unit in line between your starting battery and your lithium house bank. You need this unit in line because lithium sits at a higher voltage and requires different charging parameters than lead acid. An isolating unit will disconnect the line between the batteries so that your lithium batteries do not continuously feed power into your starting battery. You can isolate your two battery banks with a battery isolator or a DC to DC charger depending on your system needs and preferences.

When choosing your isolating component, you will want to make sure that it is recommended by the Battle Born Battery team. Even if a component is deemed a battery isolator, it may not allow for a proper charge to your lithium bank. This often is the case when the isolator is strictly a voltage based unit.

Battle Born recommends the Victron Orion TR Smart 12/12V-30A Isolated DC to DC Charger for charging needs. This DC to DC charger is easily programmable for a proper lithium profile and is Bluetooth compatible as well.

For a Battery Isolator our team recommends using the LI-BIM. This unit is preprogrammed with the correct lithium charging profile. It also duty cycles your alternator periodically and will monitor your starting battery and lithium house bank to prioritize the charge. Below is a layout of the connections you need to make with the LI-BIM to properly isolate your two battery banks.

Li-BIM battery isolator

If you have any additional questions about your battery bank check out our FAQ, give our sales and tech team a call at (855) 292-2831 or send an email to [email protected].

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14 thoughts on “Battery Isolator with Lithium and Lead Acid Connections

  1. Why isolated? The non isolated is ok if both battery banks share common chassis ground, as I understand. But I guess the isolated covers all ground senario.

  2. I have a Victron 200A 3 bank ARGOFET Isolator. Will this work with a Battleborn House Bank, Lead Acid Starter & Lead acid bow thruster Bank?

  3. In addition to the email I just sent regarding the Victron isolator.
    I have a 170A Balmar alternator and an external Balmar 614 regulator. Which can be tuned to Lithium settings.

    1. Hi Kevin, thanks for your comments. Although we have not tested this device with our batteries and after looking through the information on this product, our team does not see any red flags and it looks like it should work well. Also, the MC614 Balmar regulator works great with our batteries. Please let me know if you have any additional questions and have a great day!

  4. Would the Orion-TR Smart 12/12V-30A Isolated Charger work in a solar set because i currently have 2 lead acid batteries are not even a year old but i want to add a lithium battery. Im trying to figure out how to have both charge by the same panels and out put to the same inverter would this help? Would i need two charge controllers?

    1. Hi Pat, thanks for reaching out. Please give our sales and tech team a call at 855-292-2831 and they would be able to assess your system and its needs for solar. I apologize for the delay in getting back to you and please let me know if you have any additional questions.

  5. I have a boat with 130A alternator for my 1 x G31 AGM start battery and 4 x G31 AGM House batteries. Currently when the engine runs and engine start battery voltage increases over 13.0 volts, a charge relay connects engine battery to the house battery. The charge relay works in reverse when the solar or inverter/charger increases voltage to house battery during charging and it rises to over 13 volts, it connects the house to engine battery to charge it. With 4x BB lithium this wont work.
    I can disconnect the charge relay so there is no cross charging. I can set my inverter/charger to lithium and my solar charge controller lithium; both attached to the house battery. Thus solar and generator charge the 4x BB lithium properly. However, I have no way to charge the house lithium by alternator.
    I’d like to use the Victron Orion TR Smart 12/12V-30A Isolated DC to DC Charger to connect the AGM start battery to the BB lithium house so when the engine runs, the Orion will see the increased voltage of the AGM and charge the lithium house. My concern is that people say the Orion puts out a constant 18 amps. Is this bad for a bank of 4 BB 100Ahr lithium batteries? What if the house bank is full and you give it 18 amps?

    1. Hi Lorne, thanks for reaching out. The Orion will not be bad for a bank of 400ah. It’s a good size for your alternator and for high voltage charge as well. If you have any additional questions please give our sales and tech team a call at 855-292-2831.

  6. Hello,
    Here is our 5th wheel Setup
    – 4 100W solar panels with one 50A charge controller.
    – Onan 7000 genset (7KW output)
    – 1 Led acid battery to start the genset (Located in 5th wheel, already have)
    – 3 Battle Born Li batteries (Will be located in the 5th wheel, Soon to have)
    NOTE: We boondock 95% of the time (almost never plug into a RV park). Mostly battery charge comes from the truck (while I am pulling the RV. about 10% of the time we are out), the solar panel array (While we are boondocking. About 60% of the time while we are out), or the genset (about 30% of the time we are out . We travel fulltime.
    As stated, I am replacing my Led Acid Batteries with Battle Born 100ah lithium batteries (3 each). I have already committed (gave charge card number to the sales rep to go ahead with purchase) to a quote that includes an upgraded inverter.
    Here is the question… I would like to keep one of my led acid batteries for the start battery for the genset. The three BB batteries will be running the 5th wheel travel Trailer. How can set up the charger (to charge both battery banks without the batteries ever seeing each other (do not mix Lithium and Led acid batteries in one bank). I thought of a isolator but it seems, theoretically, that when the isolator (relay) kicks in when is senses the low voltage on the LAB (Led Acid Battery) that it will connect the two battery banks together in an attempt to charge the LAB.
    What do you recommend so I can have the set up ready when I receive my three, most coveted, Battle Born batteries. Thank you in advance
    Carl Combs [email protected]

    1. Carl, I have passed along your email to our sales and tech team and one of them will be following up with you shortly. Please note that you may also need an LI-BIM if the size of your alternator is under 225 amps.

  7. One of the features of my RV is a Auxiliary Start System,

    “which engages this solenoid and joins the house battery with the chassis battery to provide a “boost” to help start the motor home if the chassis battery charge is low.
    The auxiliary start switch can momentarily connect both the house and chassis batteries should the chassis battery become discharged.
    To operate, depress either the Battery Boost switch on the driver console and hold it down. While the Battery Boost switch is depressed use the ignition key to start the chassis engine.
    Release the Battery Boost switch after the engine has started.”

    Please keep in mind that Battle Born Batteries should not be used for cranking applications such as turning over the engine, and you will need to keep your lead acid starting battery in place.

    If I were to install Lithium batteries for my house 12V electrical needs/Inverter, would I need to disconnect the Battery Boost capability?

    1. Yes, that is correct, you would need to disconnect the Battery Boost as it is used for cold cranking.

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