Bigfoot Lithium upgrade - Fiberglass RV


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Old 11-06-2019, 02:23 AM   #1
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Name: Jon
Trailer: Bigfoot
California
Posts: 98
Bigfoot Lithium upgrade

Hi,
I posted a while ago that I had planned to upgrade my battery in my Bigfoot 21RB. A few people suggested I buy regular AGM. I thought long and hard about it. I appreciate everyone's comments, and considered what people said about the AGM. But, after a few camping trips and many instances where I had to recharge the battery even after just sitting in the driveway, I ended up buying 2 Battle Born 100Ah Lithium batteries and the upgrade the Progressive Dynamics PD4045 standard converter to the PD4045 lithium. I also got a Victron BMV-12 battery monitoring system.

At first I was going to put the new batteries on the tongue since there was plenty of room there behind my propane tanks, and use the existing battery wires. But, Battle born strongly suggested putting them inside the RV if at all possible. The Bigfoot has some storage space under the dinette seats so that's where I plan to put them. Picture 1 shows this area. I plan to put the batteries in the right front compartment, run the wire behind the panel and connect to the battery side of the relay which is under the front left compartment. I would have put the batteries on the left but that would get in the way of access to the water heater valve.

Currently, the positive battery wiring is 8 AWG and comes through the floor along with the positive lead wire from the electric brake and the the wires from the 7 pin connector, then the positive battery lead goes to a battery isolation relay. Picture 2 shows how the wires come through the floor. Picture 3 shows the relay. Currently, the negative lead of the battery is connected to the chassis ground. The PD4045 has a ground lead that goes through the floor and is tied to the chassis as well. (Picture 4)

I plan to connect the 2 batteries in parallel using 1/0 AWG wire and the negative shunt for the battery monitor using 1/0 AWG as well. I was thinking about just running 2 AWG, or maybe 1 AWG wire across from the most positive post on the battery to the isolation relay on the same spot where the battery is currently connected. All of the existing wires are 8 AWG so I don't see a need to run 1/0 everywhere (not to mention how hard it will be to run wires that big.) But, I'm open to suggestions. I would also have to run the negative lead from the inside battery area to the other side where the other negative leads go through the floor (Unless I end up drilling through the floor near the batteries, and running the cable to the chassis there.) I am not adding an inverter yet or any other additional load, so the current draw shouldn't be more. According to Battle Born there should be no need to upgrade the existing wiring to the trailer since I am using the same rated converter.

Eventually when I mount my solar panels I will run the wires from the panel through the floor to the battery. For now, the existing 8AWG battery wires will still terminate outside the trailer on the tongue inside the fiberglass cowling so I was hoping to just connect my portable solar charger outside to that. I realize there may be some power losses but at this point I don't want to run a heavier wire through the floor just yet. Or, should I make it a point to drill holes in the floor for the portable solar panel to connect to the battery now, and run the negative lead straight to the chassis instead of all the way to the other side of the RV then through the floor. I'm leary of drilling any holes since I'm not really very good at that sort of thing.

Will this work? Is there any reason why I can't just connect the battery set directly to the positive of the relay where the old battery is?
Any other suggestions? Does anyone know anyone in the SF Bay area that you would trust to drill into the floor for the cable runs? Everyone I called either was gone for the season, or booked up until next year.
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Old 11-06-2019, 01:38 PM   #2
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Name: Stephen
Trailer: Casita
Tennessee
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Thumbs up Sound Idea

Your desire to improve all trailer operations by providing adequate power is very prescient. Most owners don't consider power limitations until they experience failures.

I think placing the batteries inside is a VERY good idea for security reasons. Right now, the average bubba is pretty ignorant. But as familiarity with lithium systems grows, more thieves will become aware of what they are worth. Having them exposed outside is an invitation to theft. 😲

Also, be aware you are going to be limited with conventional lithium batteries. They can easily be damaged by exposure to cold temperatures. If this is concerning to you then a rethink of your operating temperature requirement and reconfigure is appropriate. ⚠
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Old 11-06-2019, 04:22 PM   #3
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Name: Carl
Trailer: LiL Hauley
Syracuse, NY
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Converting to lithium is a large initial investment but is definitely worth it.
Air Doug has a well documented conversion in his lil snoozy. On our 80 day 15,716 mile trip to Alaska this summer we never plugged into shore power or used a generator. All power came from 2 100 watt solar panels and the vehicle while driving. We have 1 100 Ah battle born battery. Our largest load is the Truckfridge refrigerator.



Regarding the cable size. 1 awg might be a bit of overkill. You should do a electrical load analysis. Just add up all the loads that can be on at the same time and base your wire size on that number. Larger than required wire adds cost but reduces line loss. Its a compromise.



Regarding your solar system components. If you just have 200-300 watts of solar, I would utilize the existing wiring to your external box. I would mount your controller as close to the batteries as possible.


I don't know the function of the relay you mention, so it is difficult for me to comment, however, you are just replacing one battery for another so I don't know why it wouldn't work. One consideration is the rating of the relay vs the short circuit capability of the battery. I recommend you install fuses on the battery terminals.


Blue Sea Systems 5191 Fuse Block Terminal 30-300 AMP
Blue Sea Systems 5183 100A Fuse Terminal




Mounting the battery inside the trailer is the way to go. The BB battery has under and over temperature protection. But will not charge below freezing. Placing the battery inside, where you will be, will help to keep it above freezing. You need to keep temperature in mind during storage if you plan on maintaining charge. I put my battery in the basement when is is cold and just let it self discharge.


I also recommend installing a shutoff switch if your trailer doesn't have one, to prevent discharging when not in use.



The lithium batteries have a different voltage than lead acid batteries, so iIf you want to charge the batteries while driving, you will need a DC-DC isolation power supply. I used a 9 amp Victron model orion 12/12-9 from here

https://www.thepowerstore.com/victro...c-dc-converter



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Old 11-06-2019, 06:35 PM   #4
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Name: Jon
Trailer: Bigfoot
California
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Quote:
Originally Posted by CarlD View Post
Converting to lithium is a large initial investment but is definitely worth it.
Air Doug has a well documented conversion in his lil snoozy. On our 80 day 15,716 mile trip to Alaska this summer we never plugged into shore power or used a generator. All power came from 2 100 watt solar panels and the vehicle while driving. We have 1 100 Ah battle born battery. Our largest load is the Truckfridge refrigerator.

Regarding the cable size. 1 awg might be a bit of overkill. You should do a electrical load analysis. Just add up all the loads that can be on at the same time and base your wire size on that number. Larger than required wire adds cost but reduces line loss. Its a compromise.

Regarding your solar system components. If you just have 200-300 watts of solar, I would utilize the existing wiring to your external box. I would mount your controller as close to the batteries as possible.

I don't know the function of the relay you mention, so it is difficult for me to comment, however, you are just replacing one battery for another so I don't know why it wouldn't work. One consideration is the rating of the relay vs the short circuit capability of the battery. I recommend you install fuses on the battery terminals.


Blue Sea Systems 5191 Fuse Block Terminal 30-300 AMP
Blue Sea Systems 5183 100A Fuse Terminal

Mounting the battery inside the trailer is the way to go. The BB battery has under and over temperature protection. But will not charge below freezing. Placing the battery inside, where you will be, will help to keep it above freezing. You need to keep temperature in mind during storage if you plan on maintaining charge. I put my battery in the basement when is is cold and just let it self discharge.

I also recommend installing a shutoff switch if your trailer doesn't have one, to prevent discharging when not in use.

The lithium batteries have a different voltage than lead acid batteries, so iIf you want to charge the batteries while driving, you will need a DC-DC isolation power supply. I used a 9 amp Victron model orion 12/12-9 from here

https://www.thepowerstore.com/victro...c-dc-converter

Thank you for the reply. I found Air Doug's threads aand the Alaska posts so I will read those over carefully.

I plan to do a load analysis shortly (once I get the battery monitor installed)

Right now I have a ZAMP 180W portable solar panel. I am going to see how it does with the new batteries and see what I want to install on the roof of the trailer. I'm looking at the new Zamp obsidian solar panels. Waiting for some more reviews to come out before jumping in.

The relay I mentioned is for the shutoff switch / battery disconnect. One side goes to the battery, the other side of the relay goes to the power converter.


I will check out the dc to dc converter. But why wouldn't the power converter already do that? The wiring from the 9 pin connector to the truck is already connected through the power converter. I'll have to see what the voltage output is once I get the power converter upgrade installed.

Fuses are always a good idea, thanks!

For the negative lead, would you recommend drilling through the floor and running directly to the frame? IF so, do you (or anyone) know what the covers around the holes in picture 1 are called? Are these some kind of protector that goes through the hole? or just 2 cover plates? One of the 2 green wires that goes to the frame connects to a ground / negative bus (Picture 2). Could I just connect the battery to that since it goes right to the frame, or should I run a separate wire from my negative battery terminal through a new hole then bolt to the frame?

Thanks,
Jon
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Old 11-11-2019, 10:55 AM   #5
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Name: T
Trailer: Bigfoot
Arizona
Posts: 14
PD4045 upgrade to charge lithium battery

Jon,

I have no new ideas to answer your questions mainly because my floor configuration is different than your unit. Having said that I did not change from a standard PD4045 to the PD4045L. Instead I used the PD boost pendant that plugs right into the front of the PD4045 circuit. This allows me to manually use boost mode when charging the lithium battery on shore power. The reason I did this was to provide low cost backwards compatibility to AGM if ever needed.

Bought this from Progressive.
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Old 11-11-2019, 11:30 AM   #6
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Name: Carl
Trailer: LiL Hauley
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Jon,


I don't know the details of the power converter you have, so I can't help with that issue.



Regarding the wiring, the only thing I would connect to the frame is a safety ground. The frame is steel and not a great conductor and it also corrodes. Run all your current carrying conductors, which includes the battery negative wires to the battery.
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Old 11-16-2019, 11:14 PM   #7
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Name: Bill
Trailer: Eriba
Washington
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Cuppla things:
1. Get a Victron Orion TR battery-to-battery charger. It will properly isolate your tow vehicle from the trailer, and properly charge the LiPO battery bank. And you can watch it all happen with the Bluetooth app.
2. You don't need 1/0 wire. 6 or 8awg will likely do all that you need. Remember that if all else fails, you want the wire to melt before the trailer does!
3. Why do you think you need 200Ah of batteries? I'd bet that 100Ah is quite conservative if you're only running LED lights, water pump, and a fridge... Try one before you buy a second. Them babies are pricey!
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Old 11-17-2019, 12:56 AM   #8
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Trailer: Black Series HQ19 on order
Smith Valley, Nevada
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Jon,

I don't see why you would need a wire larger than the green wire shown, from the negative buss to the frame. That is, if it will only be carrying the running lights and the brake current. That looks like a #8 from here. You can bond it to the brake negative at the frame grounding lug and make sure the seven pin has a good ground, or negative from the tow vehicle to the ground buss. I'm assuming the voltage from the Tow Vehicle will be compatible with the trailer voltage. If not, the brakes might have to have a separate ground to the tow to complete the braking circuit, but then the lights would be a probelm too, and you might have to isolate the entire trailer frame. Will the two voltages be compatible?

In order to tie in your portable solar panel, and get additional charging from the Tow, you could run a set of wires up to the tongue and install an Anderson plug. This would provide a port for solar charging and for charging from the tow. It would also require that the charge controller be at the panels, instead of at the batteries.

It sounds like two 100 amp/hour batteries would be better than one, with your truck fridge. I had a 12 volt fridge on my boat and it averaged about a 3 amp load. This would be about 74 amp/hours per day. On a day with no solar, and only one battery you'd be out of power. Two, would at least keep you going for two days. Will you have propane? And if so, why not a propane fridge? I got very tired of always keepng the batteries up to satisfy the fridge.
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Old 11-17-2019, 09:43 AM   #9
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Raspy: I see your calculation for the fridge as 3 amps x 24 hours. But most assume (conservatively) that the fridge will only run 50% of the time. My experience is that my 3 amp fridge used about 25Ah/day in practice. A lot because it doesnít draw the whole 3amp maximum as it runs. But I do live in the Northwest so maybe Iím biased.
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Old 11-18-2019, 12:03 PM   #10
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Quote:
Originally Posted by billnieman View Post
Raspy: I see your calculation for the fridge as 3 amps x 24 hours. But most assume (conservatively) that the fridge will only run 50% of the time. My experience is that my 3 amp fridge used about 25Ah/day in practice. A lot because it doesnít draw the whole 3amp maximum as it runs. But I do live in the Northwest so maybe Iím biased.
My 3 amps average was an average. And that was the low end average when everything inside was already cool and the weatehr was cool. It ran anywhere from 30% to much higher, or around 75% if it was cooling food down. On hot days, it ran a lot.

As I recall it drew about 5-6 amps when actually running.

The problem with that kind of load is that you always have to keep up with the power it needs. You always have to keep your batteries charged up while they are under a constant load. That can become inconvenient off-grid or in cloudy weather, or if requiring a generator.

My system was on my boat, and therefore, I could not have a propane fridge. The small compressor fridge, with an air cooled condenser became a problem, so I built a holding plate system instead. It was still compressor driven, but only ran for about 20 minutes every 6 hours. It had a power draw of 20 amps when running. So it took about 28 amp/hours per day. The average use was less and I could run it when I wanted to. For instance, if the engine was running, I could turn it on and get a "free" cycle, and at the dock, it ran on shore power, so the only time it needed batteries for it, was at anchor.

It was an interesting system that was not hermetic. It had a small belt driven compressor and a 12 volt motor. It sent it's waste heat to a submerged heat exchanger/condenser in the fuel tank, instead of how it's done with RV fridges and their air cooled condensers, which definitely run much hotter.

The main point is that compressor fridges require a constant power supply, even if they don't draw very much each cycle, and even if they only run a third of the time. That eventually adds up and must be put back into the batteries regardless of the weather. And, at least with lead acid batteries, there is a lot of losses during the re-charging process, so you can add another 25% to your power requirements, if you add the re-charging losses.

For me at least, the propane fridge is the way to go. It can be left unattended for a month or more, is silent, and has almost no affect on the batteries.
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Old 11-18-2019, 01:09 PM   #11
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Thanks for the context Raspy! My experience is on a boat too. Yeah, no propane reefers for me.
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Old 11-18-2019, 02:17 PM   #12
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no propane reefers for me.
Bill, do you mean no propane fridges on a boat, or no propane fridges anywhere?
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Old 11-18-2019, 08:09 PM   #13
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Sorry for any confusion. I actually mean both for me. No permanently running propane on a boat is the standard. Plus keeping the unit vertical is an issue. And my campers are European-built Eriba Puck & Pan models, both with under-counter fridges. Electrolux makes RV fridges that work without the standard venting that we in the US know. But these are not imported so I have had to replace both with electric models.
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Old 11-22-2019, 05:14 PM   #14
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Just to reiterate what others have said, I think you will need a DC/DC converter unless I misunderstand how your PD converter works. My Progressive Dynamics converter takes only 120V as input, not ~12V from the tow vehicle. The DC/DC converter connects to the battery via a separate circuit from the converter and is necessary to boost tow vehicle charging voltage enough to fully charge the Li battery. Make sure you get the isolating version.

I also strongly recommend a main shutoff switch. I have now run down the Battle Born battery twice by accident and that would not have happened if I had actually used the shutoff switch.

Another option that I added is a 3 amp Li battery charger. They are really cheap and I use it when I have plenty of time to charge (like shore power) in order to be gentler on the battery.

I also agree with the recommendation to keep the batteries inside the trailer so they can be kept warm enough to charge in sub-freezing weather.

I finally finished my wiring diagram and will try to add it to my conversion post soon.
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