Sterling Pro Batt Ultra Battery to Battery Charger

  |   LiFePO4 Charging   |   21 Comments

Applicable Models: BB1230, BB122440 



The Battery to Battery charger made by Sterling Power solves a huge issue that many of us have, charging your battery bank off of your cars alternator. Sterling accomplished this by creating a charger that takes power from the starter battery, regulates the voltage and current, then sends it to the battery bank.


Here is how to set this unit up with Battle Born Batteries!


Before starting this installation, make sure that your vehicle is powered off.


Step 1:

Take unit out of box and remove lower front red face plate to expose the input terminals.


Step 2:

Connect the negative terminal of the house batteries to the negative terminal of the starter battery with a 6 or 8 AWG cable. We used a 6 AWG cable throughout our installation.


Step 3:

Run a positive cable from the positive terminal of the starter battery to the “IN+” terminal of the battery charger.

Run a negative cable from the negative terminal of the starting battery to the “NEG-” terminal of the battery charger.


Step 4:

Bring a cable from the positive terminal of your house battery and connect it to the “OUT +” of the battery charger.

Double check that you have made all of the correct connections and then start the vehicle and the unit will power on.


Step 5:

Once the charger is fully powered on press both of the buttons, “SETUP” and “SELECT”, for 10-12 seconds (10-12 flashes). Then use the left or right button to move the LED up to the “Custom” position. Press and hold the two buttons again for 2 seconds to select this setting.


Step 6:

A LED at the top of the unit will be blinking over “Bulk/Boost”. Use the two buttons to move the LED’s so that both the 14.2V and 14.6V are illuminated. Press and hold the two buttons again for 2 seconds to select this setting.


Step 7:

The “Conditioning” LED will now be flashing. As before, use the two buttons to move the LED’s so that they are illuminating 13.4V and 13.8V. Press and hold the two buttons again for 2 seconds to select this setting.


Step 8:

The “Float” LED will now be flashing. Use the two buttons to move the LED’s so that they are illuminating 13.4V and 13.8V. Press and hold the two buttons again for 2 seconds to select this setting.


Step 9:

Two LED’s at the top of the unit should ow be flashing, the  “Bulk/Boost” and “Float” LED’s. Press the two buttons for two seconds. Now the “Conditioning” and “Float” LED will illuminate. Press and hold the two buttons for two seconds. Press and hold the two buttons for two seconds for the third and final time.

Now you can either press the two buttons again or let the unit sit for 30 seconds to restart it. It will then power off and restart with the correct charging parameters.


Step 10:

If your vehicle does not have regenerative breaking, you can turn it off by pressing the “SETUP” button for 10-12 seconds. You will then see the “Absorption” light blinking. Press the two buttons for two seconds and then wait 30 seconds for the unit to restart.


Step 11:

With the vehicle on, use a multimeter to make sure that the charger is outputting the correct voltages. If it is not, you can reset the unit by following this video.


If you have any issues, please give us a call at 855-292-2831 and we will be happy to help with the process.

  • Steven Peaslee | Mar 8, 2018 at 10:44 pm

    Can you give instructions for the Sterling BB1260
    60 amp unit for runn two 100ah batteries


  • Garrick Boyd | Jun 10, 2018 at 4:00 am

    I see Steven’s question, but don’t see an answer. I have the exact same question. Also, is the Sterling a good choice or a waste of money vs a battery isolator?

    • Sean Nichols | Jun 10, 2018 at 5:10 pm

      Sorry about that, we missed that one. The Sterling product is great, its a step up from just an isolator. Anything 300ah or more, I would consider it.

      We also offer an isolator programmed for Lithium from precision circuits. All depends on how much control you want.

      Please call me 775-221-8894 or email me [email protected] Thanks for reaching out.

  • Dave Stilholme | Sep 7, 2018 at 6:28 am

    If the Sterling unit is recommended for 300AH or more what would you recommend for using only one 100AH battery? Is a B2B charger needed if using only one battery or would the current draw damage the alternator or overcharge the lithium batter? This Sterling unit seems quite large for the space I have to work with. Is there a somewhat smaller alternative for a smaller system?

    • Sean Nichols | Sep 7, 2018 at 10:49 am

      We actually offer 2 choices for managing current flow and alternator charging. We have a special battery isolation manager from Precision Circuits that works really well and takes up very little space and does not require programming. This device will duty cycle your alternator charging current 15 min on 20 min off, to make sure you don’t overheat your alternator on a long drive. This is or the Sterling battery to battery charger work well in banks 300ah or more.

      In smaller batter banks you can just use any isolator, it will work fine. If you want to expand your bank later to 3 or more, put the LiBIM in now and that way you are all set for your future expansion.

      Here is a link to this part

  • Nicholas Wilson | Nov 28, 2018 at 10:24 am

    How do you pair this with a solar charge controller and PV panels?

    • Dianne F | Nov 28, 2018 at 3:50 pm

      Hi Nicholas,

      The Sterling Battery to Battery chargers act as a charging mechanism to properly fill your lithium battery bank via the alternator/starter battery. Solar charging is not involved in this process and is meant to charge from the sun.

      We hope this helps but please don’t hesitate to give us a call if you would like to discuss this further.

      Thank you!

  • Kevin Holt | Dec 3, 2018 at 9:36 pm

    I keep reading all this stuff about modern vehicles have smart alternators now and they don’t charge auxiliary batteries good with a regular charge relay like they used to and I need one of these DC to DC chargers. Is that true or can I just use a charge relay? I have two of your 100ah batteries I’m putting into my 2018 Ford Transit. I’m just wanting to pump some amps into my batteries driving between campsites or possibly running the engine at a campsite without damaging my batteries.

    • Dianne F | Dec 5, 2018 at 3:21 pm

      Hello Kevin,
      2 we recommend charging the batteries with half the amperage of your battery bank. If you have 2 batteries in parallel giving you 200 AH’s you can charge with up to 100 amps. If your alternaotr is pushing more than 100 amps when charging the batteries you muight want to look into a battery to battery charger that limits the amps. If it’s slightly more than 100 say 115 that’s not going to make a difference. But by the time it reaches the batteries the amps may be limited to around 100, so you may be good with a simple relay or solenoid.

      Thank you!

  • Dave Garth | Dec 31, 2018 at 7:47 am

    I also have a LTV Wonder motorhome on a 2018 Ford Transit chassis. I want to install two 100 amp hour BattleBorns. I’m still not clear whether I need the Sterling unit or not as I’ve gotten conflicting advice. (I don’t think I have room for it.) My alternator is a “210 amp” alternator, but, I don’t know how many amps it would typically output to the batteries, and I don’t know how I could determine this in advance of installation. I don’t want to unnessarily shorten the life of the new batteries or my alternator. Would the isolator mentioned above be adequate? With an isolator or Sterling unit, can I use the existing cable that is charging my current lead-acid house batteries now (that I assume is connected to an isolator) or do I need to install a new cable direct to the starting battery or alternator? Thanks for your help on this.

    • Dianne F | Jan 8, 2019 at 10:21 am

      Hello Dave,

      The Sterling 60 amp B2B charger is a good choice for a two bank lithium battery setup. This will regulate the current into the lithium batteries and properly isolate the starter battery and the house bank. Its a good chance that without regulating the current coming from the alternator, you will be exceeding the recommended .5c charge rate. Its difficult to make the correct recommendation without knowing how much amperage is coming into the house bank without putting an amp meter on the wires. We could safely assume the existing wire would be ok to use when installing the Sterling device between the battery banks. When you find the amperage that is being delivered to the house bank then you could refer to a wire sizing chart for the correct gauge.

      Thank you

  • Eric Talaska | Jan 1, 2019 at 6:12 am

    Can I restrict the output to 24.4V for a battery that has a max charge rate of 25V? If the output is higher than 24.4, will line loss bring it down to about 24.4?

    • Dianne F | Jan 8, 2019 at 10:31 am

      Hi Eric,

      Your charging voltage for a 24 volt system looks a bit low. For our batteries used in a 24 volt configuration we recommend: Bulk/absorb 28.4 – 29.2
      float 27.2 or lower

      Thank you,

  • John Bell | Jan 3, 2019 at 8:34 am

    Since a “simple relay or solenoid” will continuously connect the starting battery and Lithium when driving, is their a concern of overcharging the Lithium batteries by continuously subjecting them to say 14.4 volts for hours once they are “fully charged”?

    • Dianne F | Jan 4, 2019 at 5:10 pm

      Hi John,

      Subjecting the batteries to 14.4 volts for a few hours, even a few days will not cause damage or problems to these batteries. If you were storing these batteries for months and had this voltage then we would discourage it.

      Thank you,

  • Jim Kelly | Jan 13, 2019 at 11:28 am

    Hi John,

    I have a follow up question from Nicholas about pairing to the solar. When the BB1260 is in operation charging the batteries, can the solar system simultaneously be connected and charging? I’m concerned that this might create a conflict or backfeed situation without some form of isolation.


    • Dianne F | Jan 17, 2019 at 3:10 pm

      Hi Jim,

      If you are charging simultaneously, you will just be increasing the amperage going into the battery bank with this scenario. You will not get a conflict or a back feed from this.


  • Bryan Stephan | Jan 15, 2019 at 8:25 pm

    Will the Sterling Pro Batt Ultra Battery to Battery Charger work just fine for a 100ah lifepo4 battery with a Mercedes Benz sprinter? I’m charging my battery now with (2) 100 watt solar panels and an mppt charge controller. However, I’m hoping on rainy winter days the B2B charger will help support the system. Thoughts?

    • Dianne F | Jan 17, 2019 at 12:36 pm

      Hi Bryan,

      Yes, the 30 and 60 amp versions work great to properly isolate, limit current and properly charge our lithium batteries.

      Thank you,

  • Bryan Stephan | Jan 15, 2019 at 10:34 pm

    Do you need a fuse between the b2b charge and the house/starter batteries?

    • Dianne F | Jan 17, 2019 at 12:34 pm

      Hello Bryan,

      Yes, per Sterling’s installation diagram they are calling for fuses before and after this device on the positive wires.

      Thank you,

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