LR4 - Disconnect BMS to enable full charge of Battery

derekvieira

New member
Hello All,

First post… Given the LR4 horrendous charge profile related to the battery management system https://expeditionportal.com/forum/...ile-measured-with-iid-really-this-bad.163106/

I am considering disconnecting the BMS sensor on the negative battery terminal while camping when I need full battery capacity to run a fridge.

Its my understanding from extensive searching but but little objective data that the battery will be charged to full capacity as the BMS is not able to do its thing and only charge battery to about 80% when it chooses.

Has anyone played this game with BMS. It’s true there are a couple of warning signs on the dash as soon as this sensor is disconnected. I am mainly concerned about causing any other issue with this practice. I don’t have a scan tool to know exactly what is going on when disconnecting the sensor.

Hope this work around is the ticket otherwise not sure how to run a fridge on main battery. I have 95 hrs of capacity but with only being charged to around 80% and mostly not charging when driving or idling, I end up getting the low battery warning on the dash in the morning. Thanks All!
 

Ke2427

New member
Following this for any insight........hoping for someone who,can help, ive not experienced this but havent explored this on my LR4
 

llamalander

Well-known member
Not an LR4 owner, but a gremlin hunter in my own right.
Time & tools and a methodology might get you some insight.
The Gap tool seems pretty indispensable if you want data from your truck, or you want to see what is lighting up your dash.
Understanding the limitations of the battery will also keep you from killing it in your quest for power.
95 amp hours is likely not the useable capacity if you want to use the battery more than once.
The deeper you cycle, the fewer times you will be able to do so. Sticking to 50% capacity seems to be a good balance between power and longevity for lead-acid batteries.
If you want to play with the sensor, do it in your driveway & not in the woods. Low voltage from a drained batter will probably upset the truck in a multitude of ways.
It's also worth considering why they put in the BMS in the first place. For Lithium, the need to balance the cells and limit low temp. charging is essential, regular batteries do these fine by themselves.
It is a safe assumption that the BMS is not a stand alone addition there to annoy, but part of the larger system with the potential to derail any number of other electrical components if it's data goes missing.
In a complex system, like an LR, it is often worth planning on getting what you want by adding something entirely new (and simple and reliable at that) to do what you need instead of altering or disabling what is already there.
Suggestions in the linked thread for DC-DC chargers or solar inputs can do what you need, and so can a second battery system that bypasses the BMS.
Weigh the cost of repair or troubleshooting against that of new, camping specific components and your budget will not look that small.
Depending on your trips, you might even consider a fridge battery you charge at home and never connect to the truck if you are just out for a weekend (or longer with a lithium).
Moving in that direction, the packaged systems like Jackery or Goal Zero might do what you need and charge independent of the BMS limited starting battery.
All this is to say just disabling sensors is not likely to get you what you went without a fair number of unintended consequences.
 

Rufflyer

New member
The BMS is built into the LR. You can't remove it without making the car unhappy. I have owned LR3's and 4's and they are different. I will never own an LR4 again.
Not sure of what year LR4 you have, but if it has a start stop feature, there is no room for an aux battery so you options may be to use a portable power source for your camping needs.
I would recommend a large portable power source such as a Jackery, Bluetti, Renogy or another solar powered battery. I have played with the Jackery 240. I ran my SnoMaster Classic 60L for 8 hours and took the battery to 18%. I had it at the beach last weekend. I ran the fridge for 1 hour drive, hooked up the 60 watt solar panel, and 4 hours later when we were ready to leave, the battery was at 99%.
 

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