DIY Composite Flatbed Camper Build

[CoyoteThistle]

I do not have a shore power charger and didn't do much research on integrating one. I know there are some by Victron and surely others that are supposedly designed for LiFePO. Victron and others sell complete packages (battery, chargers, etc.) that are plug and play but not at all cheap.

If you go the DIY route like I did, I think that as long as you have a way to disconnect the battery from the charger automatically when the battery reaches "full charge", you'd be fine. Probably would require a charger that has a remote on/off feature (i.e., triggered by a 12v signal as opposed to just a toggle switch).

No battery tending (e.g., trickle charging) needed - in fact it is bad. Most say to just let it sit somewhere less than fully charged - fine for up to a year or more. I have a master solenoid to disconnect all loads when the camper is not in use to keep if from going dead and it just sits there. You have to be careful of parasitic loads though with this approach (over discharge is also very bad for Li). If you have solar and store the camper outside, you can just let the solar keep it from over discharging and not have to disconnect everything.

 

[Lwing]

Thanks for sharing, researching my own build, was thinking of welding up the frame with aluminum angle, then fit panels, then add interior smaller angle. Maybe I missed it, curious about your entry door, and if you plan on exterior camper storage doors?
Thanks
Nice work

 

[Terra Ops]

I do not have a shore power charger and didn't do much research on integrating one. I know there are some by Victron and surely others that are supposedly designed for LiFePO. Victron and others sell complete packages (battery, chargers, etc.) that are plug and play but not at all cheap.

If you go the DIY route like I did, I think that as long as you have a way to disconnect the battery from the charger automatically when the battery reaches "full charge", you'd be fine. Probably would require a charger that has a remote on/off feature (i.e., triggered by a 12v signal as opposed to just a toggle switch).

No battery tending (e.g., trickle charging) needed - in fact it is bad. Most say to just let it sit somewhere less than fully charged - fine for up to a year or more. I have a master solenoid to disconnect all loads when the camper is not in use to keep if from going dead and it just sits there. You have to be careful of parasitic loads though with this approach (over discharge is also very bad for Li). If you have solar and store the camper outside, you can just let the solar keep it from over discharging and not have to disconnect everything.

Thanks, that's good to know. Easier than I thought, just turn it off when not in use

 

[Terra Ops]

Thanks for sharing, researching my own build, was thinking of welding up the frame with aluminum angle, then fit panels, then add interior smaller angle. Maybe I missed it, curious about your entry door, and if you plan on exterior camper storage doors?
Thanks
Nice work

Welding up a frame sounds good and strong. However, it's the bonding of all the panels together, including interior walls/supports that give the box its overall strength. I would think the frame alone would have substantial flexing "depending on size and shape". This is probably a mute point though. It may be tricky fitting the panels inside the frame for a secure bond. I may be completely wrong I would definitely do a dry run first. As for my door, nothing special about it. Ordered it online from Lipert. Thought about making my own, but felt it was a little beyond my DIY level. It is bonded with Sika 252. Since there was no lip on the interior, I fabricated a frame to cover the gap as well as increase strength.
Since I have storage boxes on my flatbed, I don't plan to have exterior storage doors on the camper. I actually hate putting any additional holes in the panels. My goal is to keep it as simple as possible and maintain a tight insulated envelope.

 

[guidolyons]

Nice work! :sombrero:

 

[stomperxj]

I can't believe how I missed this thread. Currently building a foam core trailer myself. Great info and thanks for sharing. Sub'd!

 

[Terra Ops]

Nice work! :sombrero:

Thanks!

 

[Terra Ops]

I can't believe how I missed this thread. Currently building a foam core trailer myself. Great info and thanks for sharing. Sub'd!

Thanks.
Saw the exchange of ideas in "Composite fiberglass/foam panel build question " thread. Good stuff! Glad to see your not deterred in building your own.
I have found that the European market is not the all knowing when it comes to panels. There are companies here in the US that have been doing it for over 50 years.
Guess you can't blame sales reps for trying to discourage home made panels, or can you They just want to make a buck

 

[Terra Ops]

Probably the biggest decision of this build is whether to go lithium or not. Is it possible for a DIY'er with no electrical experience to install a
complicated "to me" lithium system?
I currently have a Blue Sea combiner installed on my truck which pig tails into a camper with lead acid batteries. From what I've read and heard, a drop in lithium
could potentially damage the truck batteries, alternator, and who knows what else. This is due to the higher charge and discharge levels.

At first I was leaning towards this AGM which would allow me to keep using my existing combiner; (Firefly Oasis)
http://www.coastalclimatecontrol.co...C-marine-battery/p/95699247/category=25823701

Then a fellow enthusiast and friend introduced me to REDARC. This tipped my decision from AGM to lithium. REDARC is a battery isolator, solar charge controller, with lithium settings all in one.
This means "I hope" that I can use a drop in lithium battery and not worry about frying my truck. Combine this with a Magnum inverter which also allows custom settings, and I should have a basically plug and play system.
For more info on REDARC; https://redarcelectronics.com/products/dual_input_40a_in-vehicle_dc_battery_charger

Found my inverter here; http://www.imarineusa.com/magnumene...MIgrTQutGi2AIVDLjACh3rxgYJEAEYBCAAEgKcBfD_BwE

 

[Terra Ops]

Lithium, lithium, lithium. Where to go, what to choose?
From a lot of reading and research I had no clue as to which lithium battery to go with. All lithium is imported from China.
So I thought why not buy direct; https://www.alibaba.com/product-det...715.html?spm=a2700.8316092.0.0.46a634cfl05w99
Then a little bird reminded me that this is an investment that could potentially need servicing. Not to mention that I new nothing about the BMS

Here were the candidates;
Smart battery; https://www.lithiumion-batteries.com/
Battle Born; https://battlebornbatteries.com/
Stark; https://starkpower.com/

I decided to go with Stark based on a strong recommendation from a friend and phone calls I had with an owner and reps.
This is what sold me; open communication/support, customer friendly, location, high end quality, patented BMS, built/assembled in USA, and a true desire to see
this technology become more readily available and affordable. There is also a built in blue tooth for monitoring the batteries.
I ended up purchasing two 125 ah which will be paralleled for 250ah total. You can get a 5% discount by entering 5off at checkout. Shipping is free!?
Probably built into the price, but the weight is impressively low that it can't cost that much.

 

[Terra Ops]

Progress has been slow going due to work and waiting for components to arrive. Not to mention the huge learning curve I'll need
to figure the wiring.

Got the pass through trimmed and lip for the rubber boot attachment.





Found the accordion rubber boot here; https://www.amazon.com/Accordion-Bo...coding=UTF8&psc=1&refRID=NSZ03SK827VAHDRKDG6H

 

[rruff]

Thanks for all the info! It's great to see your project come together.

I'm going with LiFePO4 also, but soldering a bunch of little cells together. It's project but will be cheap (if it works!). Ideally I want to start the truck and run other loads off the same battery.

Some things about lithium:
a) Don't charge then at any significant rate if below freezing.
b) Full charge on a 4S pack is 14.4v. Most newer alternators cut voltage to the high 13s so won't get you there without modification.
c) I think vehicle alternators automatically cut output to avoid overheating, so that shouldn't be a worry. Unless I'm wrong about that...
d) All your charging and control equipment needs to be programmable or made for lithium.

Oh, BTW. Why is the 125ah Stark battery 44% more expensive than the 100ah?

 

[CoyoteThistle]

Congrats on pulling the trigger on the lithium batteries! A DC-DC charger is a nice simple way to go.

I hadn't seen the Redarc unit before. Technical details are a little scarce on the website but from what I see, it looks like the lowest "max voltage" setting is 14.6v. This is really too high for lithium (folks will tell you otherwise though!). But, if the unit is actually stopping charging at 14.6v you'll be more or less okay. In order to do this, the unit must be sensing battery voltage and actually stopping charging when the battery gets "full", as opposed to just limiting charging voltage to 14.6v. Constantly trying to push 14.6v in to a full battery (absorption or float charging in lead-acid terminology) will damage it and you'll start to lose capacity. Not clear if the Redarc unit does this or not. What you really want is to disconnect the alternator when the battery reaches about 14.2v and re-connect the alternator when the battery drops below about 13.3v (fully charged LiFePo4 has a resting voltage of about 13.4v).

Again, not sure that how the Redarc unit is working, but you might ask the dealer about these questions. If the unit is not sensing actual battery voltage, stopping charging when full and reconnecting charging when the battery is no longer full, all you really have is an alternator protector (limiting current to 40 amps).

This is all true for the 120v charger as well.

I know Stark claims to have low and high voltage protection built in but it's not clear how they work. In practice, real battery protection requires some high-current solenoids to disconnect charging or loads - last I read Stark claims to do it another way but I've never found details.

Hope that all made sense - I went deep down the "LiFePo4 charging in vehicles" rabbit hole when I designed my system so just trying to pass on some of what I learned!

 

[Terra Ops]

Thanks for all the info! It's great to see your project come together.

I'm going with LiFePO4 also, but soldering a bunch of little cells together. It's project but will be cheap (if it works!). Ideally I want to start the truck and run other loads off the same battery.

Some things about lithium:
a) Don't charge then at any significant rate if below freezing.
b) Full charge on a 4S pack is 14.4v. Most newer alternators cut voltage to the high 13s so won't get you there without modification.
c) I think vehicle alternators automatically cut output to avoid overheating, so that shouldn't be a worry. Unless I'm wrong about that...
d) All your charging and control equipment needs to be programmable or made for lithium.

Oh, BTW. Why is the 125ah Stark battery 44% more expensive than the 100ah?

I'm not sure why its more expensive, I do know that its the same size as the 100ah. My initial goal was 300ah, I hope the 250 will do.

 

[Terra Ops]

Congrats on pulling the trigger on the lithium batteries! A DC-DC charger is a nice simple way to go.

I hadn't seen the Redarc unit before. Technical details are a little scarce on the website but from what I see, it looks like the lowest "max voltage" setting is 14.6v. This is really too high for lithium (folks will tell you otherwise though!). But, if the unit is actually stopping charging at 14.6v you'll be more or less okay. In order to do this, the unit must be sensing battery voltage and actually stopping charging when the battery gets "full", as opposed to just limiting charging voltage to 14.6v. Constantly trying to push 14.6v in to a full battery (absorption or float charging in lead-acid terminology) will damage it and you'll start to lose capacity. Not clear if the Redarc unit does this or not. What you really want is to disconnect the alternator when the battery reaches about 14.2v and re-connect the alternator when the battery drops below about 13.3v (fully charged LiFePo4 has a resting voltage of about 13.4v).

Again, not sure that how the Redarc unit is working, but you might ask the dealer about these questions. If the unit is not sensing actual battery voltage, stopping charging when full and reconnecting charging when the battery is no longer full, all you really have is an alternator protector (limiting current to 40 amps).

This is all true for the 120v charger as well.

I know Stark claims to have low and high voltage protection built in but it's not clear how they work. In practice, real battery protection requires some high-current solenoids to disconnect charging or loads - last I read Stark claims to do it another way but I've never found details.

Hope that all made sense - I went deep down the "LiFePo4 charging in vehicles" rabbit hole when I designed my system so just trying to pass on some of what I learned!

Thanks for the info, I really appreciate it. I have the questions in process, will follow up when I have answers.