Adding over-discharge protection to a LiFePO4 battery upgrade

[stateofidleness]

Hi all! New member and first time posting. Apologies in advance if I selected wrong forum.

I have a 2011 Zoom 18ft camper that had a lead acid battery die on me this week. I went down the LifePo4 upgrade rabbit hole, and ended up purchasing a sizeable Eco-Worthy 280Ah LifePo4, and the upgrade lithium-supported converter for the camper (a WFCO WF-8955 I believe).

In researching, I saw a lot of recommendations from people that added their own over-discharge disconnect "unit" since the battery's BMS's cut it off a little too low (like 10v). I then came across all the Victron products that supposedly do this, but in all my reading, got confused if that would work since I need a "two way" charging/load for my camper (not one-way like the Victron says).

So I guess I'm just a little stuck now on what missing component(s) I need to accomplish this, and then, how to actually wire it all up. Most of this will be mounted on the tongue like before (except for the upgraded converter obviously).

Appreciate any wisdom/guidance you can offer! Thanks in advance.
-Steve

 

[Mark_K5LXP]

What actual problem were you hoping to solve with this disconnect?

Mark B.
Albuquerque, NM

 

[stateofidleness]

What actual problem were you hoping to solve with this disconnect?

Mark B.
Albuquerque, NM

Hey Mark - I had read a few people stating the built-in BMS of the battery I purchased had an "over-discharge" cutoff that was "too low", so a dedicated device like the Victron thing would allow me to set that cutoff a bit higher at like 12% or higher.

Because I'm a novice to this stuff (and reading stuff like that makes me paranoid), is this something I should really be concerned with or am I overthinking it?

My camper stays at a remote property of mine and stays connected to commercial AC power 100% of the time. I only recently learned that my fridge and AC still run on battery even though I'm connected to AC (to give you an idea of how green I am with all this ). I'm not sure what killed the old lead-acid battery, maybe a prolonged power outage or something. I usually only visit the property on the weekends, sometimes every other weekend. Fridge stays on and operational full time.

I mainly wanted that "insurance" that if there was a power outage at the property or something and the fridge started to over-drain the battery before I have a chance to get out to the property, that "something" could just disconnect the loads for me if it reached too low of a charge.

 

[Mark_K5LXP]

my fridge and AC still run on battery

I'd believe the fridge but not AC. Not immediately known is if the fridge is absorption or compressor. That makes a couple orders of magnitude difference in how much power is drawn.

What you're proposing here is a corner condition - IF the power goes out AND it can't be addressed AND the battery BMS is funky THEN, -? All of these events ends up in an unknown so determining what problem you're solving is one question to answer. It will not solve the fridge issue - it gets hot whether the BMS or a protection device shuts it off.

First observation is that if shore power is lost, the battery picks up the load until it is drained. How long that is depends on the load. It's a basic exercise to calculate what that will be. Will it be enough to ride through the interruption? If so, then check the box. If not, the battery is only delaying the inevitable. I would add that not all power interruptions are due to lost mains. There are a number of fault, protection and equipment failures that can trip or happen. The forums here are full of these tales of woe.

I wouldn't be so quick to second guess the OEM BMS. Unless you have something more credible than internet opinion that it's an issue to address I would leave it be. Going in another layer, if the battery model or design is questionable then applying external hardware to mitigate it adds cost and complexity, and reduces value and reliability. A 'better' battery without the issue might be cheaper, would be simpler and hence more reliable. Extending the integrity notion, if this part of the BMS is jacked, what else about that battery is too?

Going up a layer, I question the notion of storing an RV with a refrigerator full of food. You're exposing the entire RV to possible spikes and surges by leaving it plugged in. Yes, this happens any time it's plugged in but plugged in when stored the risk is 'more'. This on top of the prescient risk of the fridge shutting off and ending up with a box of biohazard to deal with.

My opinion is install the battery and converter, and run it a while. After observing everything operating under a range of conditions you may discover that there's no problem to solve, or discover a different issue.

Mark B.
Albuquerque, NM

 

[bigbAZ]

If you should decide you want to change it, or just look at the current settings, download the Overkill app and go into your BMS (which is a JBD) where you can change the low voltage cutoff setting. You can also download the XiaoXiang app but the reviews are pretty bad. I'm happy with Overkill, you can see a lot of info about your battery and helpful with cell balancing which will allow you to maximize your stored capacity.

Google Search

 

[stateofidleness]

I'd believe the fridge but not AC. Not immediately known is if the fridge is absorption or compressor. That makes a couple orders of magnitude difference in how much power is drawn.

What you're proposing here is a corner condition - IF the power goes out AND it can't be addressed AND the battery BMS is funky THEN, -? All of these events ends up in an unknown so determining what problem you're solving is one question to answer. It will not solve the fridge issue - it gets hot whether the BMS or a protection device shuts it off.

First observation is that if shore power is lost, the battery picks up the load until it is drained. How long that is depends on the load. It's a basic exercise to calculate what that will be. Will it be enough to ride through the interruption? If so, then check the box. If not, the battery is only delaying the inevitable. I would add that not all power interruptions are due to lost mains. There are a number of fault, protection and equipment failures that can trip or happen. The forums here are full of these tales of woe.

I wouldn't be so quick to second guess the OEM BMS. Unless you have something more credible than internet opinion that it's an issue to address I would leave it be. Going in another layer, if the battery model or design is questionable then applying external hardware to mitigate it adds cost and complexity, and reduces value and reliability. A 'better' battery without the issue might be cheaper, would be simpler and hence more reliable. Extending the integrity notion, if this part of the BMS is jacked, what else about that battery is too?

Going up a layer, I question the notion of storing an RV with a refrigerator full of food. You're exposing the entire RV to possible spikes and surges by leaving it plugged in. Yes, this happens any time it's plugged in but plugged in when stored the risk is 'more'. This on top of the prescient risk of the fridge shutting off and ending up with a box of biohazard to deal with.

My opinion is install the battery and converter, and run it a while. After observing everything operating under a range of conditions you may discover that there's no problem to solve, or discover a different issue.

Mark B.
Albuquerque, NM

That's a logical approach. I should probably also add that I never leave (rarely store actually) food in the fridge, it's primarily for drinks so I have something cold when I visit, and don't have to lug around an ice chest. It takes too long to get cold, so I just leave it on and running between visits so it's "always ready" for a visit. It's a Norcold brand, but I forget the model.

On the AC, when the battery died, I just noticed it wasn't getting cold. Was blowing like normal, just not cold. Identical to the fridge (powers on, but not cold (and showed low DC status)). So I just assumed it was related to the battery problem.

 

[stateofidleness]

If you should decide you want to change it, or just look at the current settings, download the Overkill app and go into your BMS (which is a JBD) where you can change the low voltage cutoff setting. You can also download the XiaoXiang app but the reviews are pretty bad. I'm happy with Overkill, you can see a lot of info about your battery and helpful with cell balancing which will allow you to maximize your stored capacity.

Google Search

whoa that's awesome! first I've read/heard about the "jbd" thing. that's great info. I just saw these Eco-Worthy batteries got good reviews. If that app approach works, that's a HUGE time/money/complexity saver. thanks for that.

 

[CharlesinGA]

Is this a Dutchman Zoom trailer? Is the A/C controlled by a wall thermostat or does it have a thermostat on the air distribution itself?

Some Dometic A/C units that had wall thermostats controlling both the A/C and the furnace require 12v DC.

If you replaced the power converter with a WFCO unit, just go ahead and throw it out and put in something that will last a while. Sorry, but they are junk. I highly recommend the Progressive Dynamics 4600 series. They come in a metal housing for the Parallax panels, however the instructions tell you when replacing a WFCO in a WFCO panel, just remove it from the housing and install it in the place of the WFCO, it comes with the necessary pieces to do that.

Building lightweight, self-contained travel trailers, Dutchmen Manufacturing introduced the Zoom line in 2007. Trailers ranging from 14 to 26 feet created for towing by crossover utility vehicles, minivans and some passenger cars, Zoom trailers were standard equipped for enjoyable weekend camping. Production of the Zoom brand ended after the 2010 model year.

 

[stateofidleness]

Hey Charles, yep that’s mine! The Dutchmen.

The AC has different fan speeds and a “Colder” dial on it. I do have a wall mount thermostat, but honestly not sure what it controls. Never used it (because I thought it only did the furnace which I haven’t needed so far).