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Old 10-06-2021, 04:21 PM   #1
91cavgt
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Default Tiny cargo trailer to camper/sleeper conversion

This is something Iíve been wanting to do for a couple of years but I just never had the time to devote to a project like this. Well, be careful what you wish for because you might just get it!

Now that Iím medically retired from work, I needed something to keep my mind and body busy for a couple of hours a day. Low and behold, a small cargo trailer happened to fall in my lap for a price that I couldnít pass up! So let me introduce you guys to this project!




The trailer is an older retired Uhaul trailer that is 5íX8í with an interior height of 52Ē. Yes, it is tiny! But Iím only 5í6Ē and Mrs 91CavGT is only an inch taller than me so we donít need anything huge. Since it is a former Uhaul cargo trailer, it is overbuilt! It has a single axle with 6 lug 15Ē rims riding on 205/75/15 tires. With the size of the axle and the 6 lug hubs, Iím thinking this has a 3,500 pound axle. It has a small drivers side door in front of the axle and barn doors in the back. The frame is steel with strong fenders that you can stand on and an aluminum box for the sides and top. The floor appears to be 3/4Ē pressure treated plywood and looks to have been replaced a couple of years ago.



So what are we going to use this trailer for?


Primarily, we have been using it and will continue to use it to pick up supplies from hardware stores, move items while keeping things dry, and to take it camping. I have to preface the last word, camping, with this. My wife does not camp, she glamps. We do have a 5th wheel RV that we can take camping, but it is a 40í RV and there are some places we just canít take it. We have tent camped for a few years and my wife still likes to do that, but she wants a better area to cook, a comfortable place to sit down or lay down in the shade, and I want to ensure we have a dry place to sleep in case a storm comes through. I also want the ability to be able to take this boondocking or hunting without needing a generator.



So here is the intro video to this trailer:


Project cargo camping trailer part 1 - YouTube

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Project cargo camping trailer part 1 - YouTube

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BTW, towing this behind my wifeís VW Atlas SUV is quit nice! With it empty and keeping the speed at about 65 mph and locking the car in 6th gear(it is an 8 speed auto), the car got 23 and 25 mpg from 2 different fill ups! Since then Iíve used this trailer to help us move. Over a period of 300 miles, half of those miles were with the trailer loaded, the VW Atlas averaged 20 mpg with about 80% highway and 20% city driving! The Atlas has a turbocharged 2.0L 4 cylinder and an 8 speed automatic.
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Old 10-06-2021, 04:34 PM   #2
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So what are my plans for the interior?


First thing is to insulate it! Nothing huge, just 1/2” foam board insulation. Cedar planks will be installed on top of the foam board insulation so it’s only going to have an R factor of about 4, but with how small it is, that should be enough to hold the heat in come the winter and to keep some of the heat out in the summer.


I want an AM/FM/Bluetooth radio along with a pair of car speakers. There will be lights, an exhaust fan(but different than anything that is out there), USB outlets, a 12v power outlet, a water tank, a water pump, a lithium battery bank(home built), a big solar panel that covers the entire roof, an MPPT solar charge controller, a sink, a single burner stove(with the ability to swap it out for a dual burner Coleman stove), a twin(ish) size bed that can convert into a padded bench, and a decent size power inverter.


My goal is to have the bed where it can fold up out of the way, the water tank be removable, the kitchenette be able to fold out of the way, and possibly the battery bank be removable as well so we can still use this as a cargo trailer.


As of right now, there are no plans for an air conditioner(although one could potentially be added in the future) and the toilet will be a 5 gallon bucket with a toilet seat on top(only for boondocking).
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Old 10-06-2021, 07:18 PM   #3
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On this video I go over some progress. Got the weather stripping replaced on the back doors, except for the bottom. Later I will be putting weather stripping at the bottom of the doors to help keep out creepy crawlys.

I found a solar panel that fits the roof PERFECTLY!!! It is about 4’ wide and 7’ long and less than 1/4” thick. It is also flexible with no glass on it so no worries about hail damaging it. Found this panel on eBay as a NOS model. It is a VERY high voltage but low amperage model. It puts out a little over 74 volts and a hair over 3 amps. This makes it around a 230 watt model. After going through the MPPT charge controller, it will end up putting around 15 amps of current into the battery.


The battery, this is a part that’s taking a while. I’m building a lithium battery bank. It is made of 76 lithium pouch cells that are rated at 8 amp/hr each at a nominal voltage of 3.6 volts each. There will be 19 of these cells wired in parallel to make a “brick”. There will be 4 bricks that will then be wired in series to build the battery. It will end up being a 152 amp/hr battery that will have a maximum voltage set to 14.8-14.9 volts and a minimum voltage of 10.0 volts. If the battery is discharged down to 10 volts, then charged to 14.8-14.9 volts, that is 1 cycle. These cells are rated for 2,000 cycles! If I don’t let the battery run all the way down then these cells can go for at least 4,000 cycles! To control the battery bank, there is a 200 amp Daly BMS(battery management system). This BMS will prevent the battery voltage from going too low or too high. The MPPT charge controller also has a temp sensor that will be set to stop charging if the battery bank temperature drops below freezing. Charging a frozen lithium battery can destroy it.

Even though these cells are rated for being able to supply a LOT of current(200 amps per cell continuous and 400 amps for a 3 second burst), the entire battery will be fused with a 150 amp fuse to help prevent a meltdown!


The last thing that I got done on this update was to install the foam board insulation in the ceiling. Between the solar panel being on the roof and the foam board insulation, interior temps have dropped tremendously! I’m confident once the insulation on the walls goes up and the cedar planks get installed, it is going to stay pretty comfortable inside.


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Old 10-06-2021, 07:28 PM   #4
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Interesting project. I've been thinking along similar lines. And need something narrow to get in and out of my back yard.


For some reason, I was think-n you were around 6'-6'.2" tall! Bet I could fit in that trailer too. As I've lost another inch in the last two years, according to my rheumatologist. I'm down to 5'-5". I was 5'-8" twenty years ago. Lost a total of 2 over the last 7 years. Furthermore, I'll prob make the incredible shrinking man look big when I'm done.
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Old 10-07-2021, 07:44 AM   #5
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Interesting project!

Check out this trailer build: Adventure Trailer Build Thread

This one is smaller than yours, but packs all the stuff you mention wanting in yours. Hope it gives you some good ideas.

Good luck with the build!
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Old 10-07-2021, 01:34 PM   #6
91cavgt
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Quote:
Originally Posted by kmack View Post
Interesting project!

Check out this trailer build: Adventure Trailer Build Thread

This one is smaller than yours, but packs all the stuff you mention wanting in yours. Hope it gives you some good ideas.

Good luck with the build!

Wow!!! Yeah mine is not going to be anything like that. Iím not as talented nor am I much of a carpenter. No, scratch that. Iím not a carpenter at all!!!


One of the things that I want is for it to look 100% like a normal cargo trailer from the outside. This way if I need to stop for the night somewhere, nothing on the outside will scream ďSOMEONE IS SLEEPING IN THEREĒ. Except for the solar panel, that is the only exterior part that you can see.
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Old 10-07-2021, 04:14 PM   #7
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Got some more work done.


The solar panel wires are now ran inside the trailer. But before I ran them to where they need to go, I realized the rest of the wires had to be ran too. So I got the wires ran inside 3/4” PVC pipe for the fan, for the speakers, for the water pump, for the kitchen light as well as the ceiling lights.




Had to stop working as I could tell I was getting tired. My words kept getting mixed up in the video.



So next I’ll be working on securing the PVC pipes so they won’t move around at all, gotta rivet the sheet metal back in place, finish running the wires to their end destination, and then seal things up with expanding foam. After that I’ll need to clean up the expanding foam and probably start putting the battery together.

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Old 10-08-2021, 03:47 PM   #8
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Short update today. I’m exhausted!


Got the ceiling sprayed with expanding foam to help insulate the roof more. Also got the wires ran to where they need to go along with ran inside PVC pipe to keep them protected.

The biggest thing I got done today is the battery is built, mostly! I still need to build the end plates and finish installing the insulation inside the battery, but the battery is assembled, the BMS is hooked up, and got an internal fuse hooked up to protect the battery. The sides and bottom of the battery box are assembled with brad nails, but the top of the battery box is screwed down. This way, if I need to get inside the battery to replace a blown fuse or to work on the wiring then I can do that.


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Old 10-09-2021, 08:02 PM   #9
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So yesterday evening I had gotten the voltage of the battery down to 14.9 volts. But I want to setup and test the MPPT charge controller after I get the battery finished. So I put a 12 volt fan on the battery pack yesterday and turned it on. 24 hours later and the voltage has only dropped down to 14.6 volts!! It’s not going down quick enough. So I added a second 12 volt fan along with two fluorescent 12v work lights. I’ll check back in tomorrow evening to see what the voltage has dropped down to. I’m hoping it’s down to 13 volts.
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Old 10-10-2021, 08:21 AM   #10
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Can you tell me more about your battery and type? Looks large.
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Old 10-10-2021, 01:39 PM   #11
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Quote:
Originally Posted by Texas Grown View Post
Can you tell me more about your battery and type? Looks large.
Sure. These are lithium pouch cells. Here is some information on each individual cell;


Specs:

Max Charge Rate 120A
Recommend Continuous Discharge Rate 200A
Pulse Discharge Rate(3 seconds) 400A
Fully Charged voltage 4.2V
Discharge cut off voltage 2.5V
Working Charge Temp 0~50įC
Working Discharge Temp Ė20įC~50įC
Storage Temperature Ė20įC~50įC

Each cell weighs about 2/3 of a pound.


There are a total of 76 of these cells that make up the entire battery. There are 4 of these bricks that make up the battery. Each brick consists of 19 of these cells, all wired in parallel via all thread, nuts, and washers. The 4 bricks of cells are then wired in series to then build the 12 volt battery.


So each cell is capable of delivering 200 amps of current constantly with a 3 second peak of 400 amps. So each brick of 19 cells is capable of 3,800 amps of current continuous and 7,600 amps surge! But that is only at the brick voltage of 2.5-4.2 volts. The entire battery has 4 of these bricks. So, the entire battery is capable of 15,200 amps constant and 30,400 amps surge!! However, the hardware connecting the cells is not capable of handling that kind of amperage. Iím sure the all thread would melt!!

However, Iíve got the battery internally fused with a 150 amp fuse. To connect the bricks together I have 4 gauge wire along with dual 8 gauge wire. For the cargo trailer, the most amps that could potentially be pulled is going to be around 130 amps. That would be the 1,000 watt Dewalt power inverter running along with lights, the fan, the radio, the water pump, and whatever else could be running at the same time.


Ohh, I almost forgot. These cells are also rated at 2,000 cycles. This means if the cells were charged fully to 4.2 volts per cell, then discharged to 2.5 volts per cell, that is one cycle. So if the cells were cycled once per day, they would be about 80% capacity at the end of 5 1/2 years!!! So at the end of that time, instead of the battery being at 152 amp/hr capacity that it is at now, it would be at 121 amp/hr.

However, if you donít fully charge the cells and if you donít fully discharge the cells then you GREATLY increase their lifespan. In my case, the Dewalt inverter shuts off if the voltage is over 15 volts. So, I canít charge the cells up beyond 3.75 volts. The low voltage alarm on the inverter goes off when the input voltage dips down to 11 volts which is 2.75 volts per cell. So if I keep the battery voltage between 11 to 15 volts, the battery should have a lifespan of around 4,000-5,000 cycles!! That is over a 10 year lifespan being used every day.


So how much did this cost?

I bought these cells used. They came out of a test mule all electric bus that had a couple of cycles before they removed them. They were purchased at $4 each for a total cost preshipping of $304! The BMS(battery management system) was purchased new a few years ago for around $65. Now, you canít find BMS modules for less than $100 that have specs similar to mine(charge and discharge ratings of 100-150 amps). So all total, the battery cells, the BMS, the all thread, nuts, washers, wood, and wire is about $400-$425.
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Old 10-10-2021, 04:32 PM   #12
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Thanks for the info . I thought those might be Liths. But needed confirmation. I can barley keep up with what your talking about. But have a basic understanding . I just started taking an interest in Lithium batteries not to long ago. And have been doing a lot of reading on systems. Got a BattleBorn with built in blanket in my boat now, for trolling motor. And added a Vectron Bluetooth 500a shunt to it to monitor it with. Had to engineer a case for the shunt to make it waterproof. Got it all mounted on/in a battery box with external poles for hooking up the power cables so that if I need to disconnect it, I can take it out as a unit, kinda like what you did. But smaller scale.


I like your idea about power supply for the trailer.
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Old 10-10-2021, 06:31 PM   #13
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Battle Born batteries are pretty much the cream of the crop right now! They are some amazing batteries!


I thought about getting a shunt setup for the cargo trailer but for right now, I’m gonna pass. It won’t be used often enough for me to have to monitor the battery level that closely.


I too am relatively new to lithium batteries. When the lockdowns started last year I had to stay at home(was a school bus driver) but still got paid. So I bought a bunch of used 18650 batteries and started experimenting. I’ve learned a lot but still have a lot to go.



One thing that completely confused me this afternoon is I just got back from testing the battery voltage. So last night at this time, the battery was at 14.6 volts. So I turned on 2 fans along with two 12 volt work lights. The battery voltage right now is 14.5 volts!!!! Maybe the battery had a surface charge of 14.9 volts and then settled to 14.6 volts once that surface charge was used up? I’m not sure.


So I left the fans and lights on. Tomorrow at this same time we will see where the battery is at.
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Old 10-11-2021, 01:27 PM   #14
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brain is smoking form trying to decipher the batteries geragan, but, a cool build
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Old 10-11-2021, 02:14 PM   #15
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Very cool build.......even more interesting is your battery setup. We have camp house that is setup on partial solar since getting shore power to it isn't an option. We have been looking at upgrading batteries and I think this just might be the solution
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Old 10-11-2021, 02:25 PM   #16
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Quote:
Originally Posted by 91cavgt View Post
Battle Born batteries are pretty much the cream of the crop right now! They are some amazing batteries!


I thought about getting a shunt setup for the cargo trailer but for right now, Iím gonna pass. It wonít be used often enough for me to have to monitor the battery level that closely.


I too am relatively new to lithium batteries. When the lockdowns started last year I had to stay at home(was a school bus driver) but still got paid. So I bought a bunch of used 18650 batteries and started experimenting. Iíve learned a lot but still have a lot to go.



One thing that completely confused me this afternoon is I just got back from testing the battery voltage. So last night at this time, the battery was at 14.6 volts. So I turned on 2 fans along with two 12 volt work lights. The battery voltage right now is 14.5 volts!!!! Maybe the battery had a surface charge of 14.9 volts and then settled to 14.6 volts once that surface charge was used up? Iím not sure.


So I left the fans and lights on. Tomorrow at this same time we will see where the battery is at.

Does your BMS not have a shunt with it?


Sent from my iPhone using Tapatalk Pro
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Old 10-11-2021, 07:13 PM   #17
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Does your BMS not have a shunt with it?


Sent from my iPhone using Tapatalk Pro


No, the BMS does not have a shunt. This BMS I bought about a year and a half ago when building your own lithium battery was starting to really take off. At that time, it was rare to have a BMS that had a built in shunt, or even Bluetooth capability the way a lot of them have now. One big problem now with BMSs is due to the chip shortages, they have gone up in price and gone down in availability.

The BMS that I have is VERY basic. It shuts off power if the voltage of any of the bricks drops below 2.5 volts and it shuts off the battery if the voltage of any of the bricks gets above 4.2 volts. It also will balance the bricks any time the battery is charging. But, it has no low temp cut off(the MPPT charge controller does have it though) and there is no way to really monitor what the BMS is doing without a multimeter. Thatís why it was so cheap.
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Old 10-11-2021, 07:18 PM   #18
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Quote:
Originally Posted by Mbbriggs05 View Post
Very cool build.......even more interesting is your battery setup. We have camp house that is setup on partial solar since getting shore power to it isn't an option. We have been looking at upgrading batteries and I think this just might be the solution
If you want to buy pre-built lithium batteries, expect to pay $800-$1,000 for a 100 amp/hr battery from a quality manufacturer like Battle Born. You can find pre-built batteries cheaper from manufacturers like SOK, but they donít come with as long of a warranty as the Battle Born batteries have. Otherwise, the cheapest ones you can find right now cost around $350-$400 for 100 amp/hr with no really any kind of warranty or customer support.


There are places that you can buy battery kits from and assemble the batteries yourself in much the same way that I have. Typically you can get some pretty good quality components inside the battery for around $250-$500, but they do not come with an enclosure to put them in. A place I use for this is batteryhookup.com
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Old 10-11-2021, 07:25 PM   #19
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I have a 6 x12 that I insulated and use as a deer camp . 2 cots fit side by side and there's room for my ac and a couple of totes.. I used a marine battery for power. I run 2 led lights outs side and 2 inside.. I haven't had to charge the battery and my son and I have spent 4 or 5 nights in it so far this season.. I really want to buy one of the cargo toy haulers that's fully furnished. I can't bring myself to buy a rv.. seems like way too much up keep.

Sounds like your build is a lot more interesting than what I threw together.. I bet it's gonna turn out great..

Last edited by jds247; 10-11-2021 at 07:30 PM.
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Old 10-11-2021, 09:01 PM   #20
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Thanks! I appreciate the compliments and questions.


One quick thing I feel that I need to say. My apologies if sometimes what I’m saying in the videos or what I’m typing doesn’t make any sense, or it sounds like I’m talking about something else. I’ve got Parkinson’s and the more tired I am, the more the connections in my head get mixed up.

So if something I try to explain or describe doesn’t get the job done then just ask again and I can explain it better the next morning.
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Old 10-12-2021, 07:50 AM   #21
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All this talk about batteries...
If you go back to that thread I posted up earlier, the guy just added a post (on Sunday) about buying a set of 40 Ah Valence RT Series batteries (with built-in BMS) that are used in crash carts at hospitals. Something about them having to be replaced periodically no matter what condition they are in.

The specific post is HERE.

Might be a different option for some when looking for batteries for this type of use. Btw, those batteries have a pretty small footprint: 7.5"H x 7.5"D x 5"W.
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Old 10-12-2021, 08:35 AM   #22
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Quote:
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All this talk about batteries...
If you go back to that thread I posted up earlier, the guy just added a post (on Sunday) about buying a set of 40 Ah Valence RT Series batteries (with built-in BMS) that are used in crash carts at hospitals. Something about them having to be replaced periodically no matter what condition they are in.

The specific post is HERE.

Might be a different option for some when looking for batteries for this type of use. Btw, those batteries have a pretty small footprint: 7.5"H x 7.5"D x 5"W.

Valence are some good batteries too, but as you stated, are typically used in the medical industry. So new ones can be VERY pricey, but you can find used ones for a good deal. Here are some that I found here in TexasÖÖ.

https://sanantonio.craigslist.org/fo...386848649.html
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Old 10-12-2021, 09:35 AM   #23
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$480/ea...Wow! That's pretty steep!
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Old 10-12-2021, 11:10 AM   #24
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$480/ea...Wow! That's pretty steep!

The ad claims they are 138 amp/hr. If that is true then thatís a really great price. If they were 40 amp/hr then I agree that it is pretty steep.
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Old 10-13-2021, 10:03 AM   #25
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Does your BMS not have a shunt with it?


Sent from my iPhone using Tapatalk Pro


Iíve been thinking more and more about this. As stated earlier, Iím still learning about lithium batteries and I just got reminded that the voltage reading is not a good indicator of the battery level in a lithium battery.


The voltage on the battery had dropped down to 13.9 volts with the lights and fans running. The next day I checked and there was no voltage coming out of the battery! The BMS did its job and shut the battery off to prevent it from being drained too low. So I connected up a little 12 volt power supply and immediately it woke up the BMS. The battery voltage showed 11.9 volts.

So, just like a lithium powered cordless drill, the voltage of the battery stays high for a MUCH longer time than what a wet cell or AGM battery shows, then it quickly drops as you get closer to using the full capacity of the battery. With a cordless drill, you have full power and your drill doesnít even slow down until right before the battery dies. Then with almost no warning it shuts off. This battery is performing in the exact same way. So itís next to impossible to determine the battery level via battery voltage.


Because of this, and it was something that I needed to experience myself to be reminded, I ordered a battery monitor with a shunt to better keep track of the battery level.
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Old 10-13-2021, 07:14 PM   #26
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That is exactly why I added a shunt to mine. So I could tell when the battery was getting low and not leave me stranded without a troller.


There are some cheaper ones out there that tell basic battery data. Some have a hardface monitor that you can cycle through about 4 different forms of battery data info.
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