Categories: RV Solar

Updated Tesla Module RV Installation

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After over a year of working with these systems, I have refined my recommendation on equipment and build a little. 

IMPORTANT

Before reading further, the design in this article does not meet new requirements I have learned about the BP220,  During the design of this 2 years ago, there was no information about reverse charging with the BP.  We got away with it for a long time but this could be a fire hazard, READ MORE HERE

I will most likely be replacing mine with a relay.   

While our original Tesla battery install is working great I have had the opportunity to install a few more of these systems and get tons of questions about it. 

These systems can be constructed with numerous different components and can work with many different designs, however to keep costs down and make a safe system the following is a recommendation on one way to build a safe, cost effective Tesla Install. 

Do note that while Tesla batteries are a very high quality and safe when handled and run within operating characteristics, if something goes wrong they can be quite dangerous.  It is your responsibility to fully understand and make sure the system is safely programmed and installed if you choose to take on an install like this.  

Furthermore, this build is not endorsed or supported by any manufacturers of the compenents used in this build, and they may not provide support on an install like this if you run into trouble.

I also am not able to provide individual support on these builds. You might be able to find community support over in the Second-Life Batteries Facebook Group.

Here is a list of parts and components

The following is an update to the way I originally installed my battery.  This is not necessarily the best install option, but it is cost-effective.  This install does not utilize a full-time BMS but if you are interested in using one Batrium is coming out with a new watchmon 5 (or watchmon plus) and should be a great solution for integrating Tesla packs with a full supervisory BMS solution at a cost-effective price.  You can learn more about the Batrium BMS here.

​The main component changes in my system involve the exterior voltage and temperature monitoring to control battery shutdown.  The Victron BMV 712 was not available when I built my system, but is a far superior product to the BMV 702.  This device has the capability to control an external relay on temperature, high voltage and low voltage.  It can do even more, but these three features simplify the install if we use it to control the battery disconnect.   The below schematic shows how I recommend using this as the primary disconnecting means for battery charging.      

  The intent of operation of this install is to have the Inverter and charge controllers be programmed to not overcharge the battery.  I usually program the absorb and float to 24.00V and 23.98V or 24.5V and 24.48V respectively.  I use the 24 V setting for general usage, but in the dead of winter I push it a little to 24.5 to get a bit more power out of it for cloudy days and long nights .  These settings will appropriately charge the battery, but in the case that something went wrong with the chargers or the settings got changed we need a backup to prevent overcharging the battery (one of the most dangerous conditions)  That is where the BP220 input disconnect is used with the relays from the BMV712 to take the battery offline.   I program the BMV712 high voltage relay setting to 24.8V

The battery temperature should also be managed externally and can be done with a heating pad and a controller or I have seen some have success using these tank heating pads.       

These devices should keep the battery warm, but in the case that the battery is too cold it should not be charged and thus the relay in the BMV again can be set to switch on temp.  I set the low temp switch to 42 degrees (because at that temp something is wrong with my system) but you can use whatever you feel is safe for your setup.  The BMV712 has a temperature sensing option that is connected off the shunt and sends temp info back to the head unit.  

The only trouble with using the BMV712 relay to disable charging is that you actually need two relays for this system as the inverter charge can be disabled using one of the inputs.   ( you need to program the inverter to use an input as a charge disable, for victron this is done with a external BMS assistant).  To get two inputs from the one relay output on the BMV712 we use a DPST relay and hold the coil closed.  This is a fail safe configuration that will open and shut down charging in a failed state.  

Of course when commissioning a system like this be sure to test the system by setting temps and voltages too low and letting the BMV disconnect the system to make sure everything is working properly.  

​The rest of the system is pretty similar to how I have it drawn out in the previous posts.  You can connect the AC side from the inverter however you want but if you are connecting to a 50A 240V split phase RV a new product that might assist your install is the AM solar smart ATS.  This allows you to use a hybrid inverter automatically on a 50A system.  The only drawback to this is if you have a built in dual leg single phase generator as it will half the power output from the gen.   I have talked with them about this and they may fix it in future versions.  

List of Components

For those looking for a list of components, here it is:  

Again this is not complete and you can swap components for your system, but this is what I have used.  

 

Component Description
Model
Source
Inverter
Victron Multiplus 24/3000/70
Solar Charger option 1 ​
Victron Energy MPPT 100/50 SmartSolar*
*This charger will limit the system to 1400W
Solar Charger option 2
Victron Energy MPPT 250/100 SmartSolar*
*This charger will be good for solar up to 2800W
Battery Monitor
Victron BMV 712 ​
Temp Sensor
BMV702/712 Temperature Sensor
Under/over-voltage disconnect (2)
Victron BP220
Main Battery Disconnect
Blue Sea 6006 Mini Disconnect ​
Bus Bars (2)
Blue Sea Systems BusBars (100A-250A)
I recommend the use of busbars, they help keep installations clean and distribute power well
24V-12V Converter
Victron Energy Orion 24/12-40 DC-DC
*If needed can get the 70A version that has lugs and is adjustable voltage
Battery Meter / Balancer
Tenergy 5-1*
*This is not used as a “BMS” just to periodically check and balance the batteries, You need to adapt XH connectors to the battery cells to use this device. Do not leave this plugged in as it will unbalance the battery.
Battery Terminal Fuse holder (2)
Blue Sea 5191*
*These are optional but provide extra protection for the batteries during installation and handling from a short
Battery Terminal Fuses (3)
Blue Sea 5189*
*These are installed at battery on lugs. If battery is shorted this will protect battery internal fuses from destroying battery
Main Fuse
Class T 200A
Main Fuse class T holder
Class T fuse holder ​
Solar Fuse and holder
60A ANL holder and Fuse ​
Inline Fuse for relay
2A inline fuse of any type
DPST Relay 24V*
DPDT or DPST relay @24V coil (down to 18V)
*This is just a relay that turns one signal into two… we cannot put the two devices in series due to how their circuits work.
60A inline Breaker for Solar ​
DC – 60A 24V breaker
1/0 Cable ​
However much you think you need ​
just a suggestion. Make sure its true 1/0AWG, not international wire standard
6AWG cable ​
Combiner – charge controller- busbar wire
1/0 Lugs ​
you need a minimum of 16
Battery Heater Pad
Water Tank Heating Pad ​
I have heard of people having good luck using these tank heaters.
Solar Combiner Box
(recommendation)
Click the image to go to the KIT page with links to products

As in the previous posts this system does not utilize a full BMS but rather relys on periodic testing of the battery to check balance with a tenergy 5-1 cell meter.  To use one of these with a tesla pack you need to either buy a pack that has standard JST-XH connectors adapted to it already or you will need to adapt it yourself. 

Dave posted a comment on my prevous post about having to adapt his battery to work with the tenergy 5-1.  Below is his recommendation and it sounds about right. ​

 If you received your Tesla Battery with the BMS Board still attached, I recommend you immediately remove it. My BMS Board was “electrically” warm when I received my Tesla Module.
The Tesla BMS wires on the Module are numbered 0 to 6, with 0 and even numbers on the top and the odd numbers on the bottom. the 0 wire is attached to the negative terminal of the battery and 1 – 6 address the different cells. Electrically, each BMS wire is additive, i.e.: between 0 and 1 is 3.5v and between 0 and 2 is 7v and 0 – 3 is 10.5v, etc. (your voltages will vary). The Tesla BMS uses two JST XH connectors, one is a 5 pin connector and the other is a 7 pin connector. I purchased a set of JST XH extension cables from Amazon, the set consisted of 2 cables each with 3, 4, 5, 6, and 7 wires. I took a 7 wire connector and a 5 wire connector and removed the male ends from each connector, I then inserted the pins from the two female connectors in a 0 – 6 sequence into the male connector. The two female connectors were attached to the two BMS leads from the Tesla Battery Module, the key to sequencing the female connectors is that Tesla used every other pin on these two connectors. So, what you wind up with is: Male pins 0 – 6 as follows: (# 1 pin top) then (# 1 pin bottom) then (# 3 pin top) then (# 3 pin bottom) then (# 5 pin top) then (# 5 pin bottom) then (# 7 pin top). The male 7- pin connector then fits right into the Tenergy BMS.

-Dave

You can also purchase these packs already modified from Jason Hughes at 057 tech.  Jason is also working on a simple BMS solution that will balance the packs and possibly have an alarm output.  It is not available yet but conceptual drawings are out and it looks great!  Keep an eye out for it at ​https://057tech.com/

​If you are considering using Tesla packs in a mobile application I hope this helps you out and gives you an idea of one way to do it.  If you want to learn more about this and other systems be sure to join us on our Second Life EV Facebook Group!  

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Mortons on the Move

We are Tom & Caitlin Morton. We gave up the stationary life for one where we are constantly on the move. We live in a fifth wheel RV and travel with our two pups, Mocha and Bella. We enjoy hiking, biking, boondocking, videography, and upgrading our RV to suit our off-grid mobile lifestyle. Our goal is to share educational, entertaining, and inspiring content with our readers and viewers.

View Comments

    • I got huge issue if someone could help ? My 4 module s tesla stay at 23.8 wont go any higher on my controller is set to 24.4 and float 24.2. When i turn on the inventer it shutoff 🤷🏽‍♂️

      • You don't give us much to go on. What type of inverter, charger, solar, solar charge controller, what device is charging the batteries and from what source. All that would be a big help in suggesting solutions.

      • Nolo... It is possible you don't have enough charging power @24 volts to charge the 4 Tesla Modules. I would disconnect three of the modules and try charging only a single Module, then add one Module at a time and test my results. It is also possible that one Module is not able to properly charge so you might have to test the system with a different "Single" Module to eliminate that issue as a possibility.
        PS: next time you post a "New" issue like this one please post it at the end of the postings so we can more easily find it to respond, with this forum format it is not easy to find postings so we can all respond.

      • Well i addes balancer to all of them . Battery came unbalance from ebay seller 😕 . Thank god my gut never fail i would have mess up all 4 packs

  • The Victron BMV 712 easily networks with the Victron smart solar charge controllers and are combined in one bluetooth app :)

  • When Tom speaks of "inverter charge", he's referring to a Victron inverter with a built in 120VAC charger, not a stand alone inverter.

    • Thank you for clarifying, Yes that is referencing an inverter charger, specifically the Victron 24V multiplus I used.

  • Awesome update! You have a typo, I believe: "I usually program the absorb and float to 24.5V and 23.98V or 24.5V and 24.48V respectively." That should be: "I usually program the absorb and float to 24V and 23.98V or 24.5V and 24.48V respectively."

      • Tom,
        I am using the same 24/3000 inverter and I have read you lower the float charge by 0.02 volts from the bulk charge. Did you adjust or reconfigure the bulk/boost charge time under the charge profile software? Do you set your MPPT charge profile to match the inverter profile? Can you send me a screen shot of your charge profile from the Victron software?

  • Out of curiosity, why did you move to the BP220 after the solar charge controller from the BP65?

    • I read the fine print: "The solar disconnect BP unit is oversized for future alternator charger" :)

  • Does anybody know what the safe charging characteristics for a 48V system would be? Do I just double the 24V system safe charging higher up in the comments, or are they different? I need to set up a 48V system running an 8000W hybrid inverter/charger from victron. I am going to be using all Victron products as they all have the manual setting functionality. I already have 4 of the tesla batteries.
    Thanks for any help.

  • What do you put in the BMV-712 in terms of capacity? The Tesla battery has about 530 AH of capacity when charged to 25.2V. If only charging to 24, do you have it show 100% or 90% charged?
    Thanks

    • Correction. 233 Ah Capacity at 25.2V
      I set the BMV-712 to 24.9 for fully charged. In my Multiplus I have the inverter shut off at 19.6v and I have the BP-220 shut of at 19.6v
      Any ideas for improvements?
      Linc

  • I have my BP-220 and Multiplus set to shut off loads at 19.6. During testing I get a Multiplus low battery alarm and system shutdown at 20.6V I can't figure out how to get it to use that last one volt!!! Any ideas?

  • Both your videos and schematics have proven invaluable to my venture into adding solar to my trailer. Though I haven't started the install most of the equipment has been taken from your design. It is a most elegant design and thanks for making us aware of 057 Technologies, they were most helpful.

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