Thread: DIY Composite Flatbed Camper Build

  1. #121
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    Quote Originally Posted by CoyoteThistle View Post
    The response from Stark is entirely consistent with their position that they are selling a "drop in" lithium battery and since the DC-DC converter is doing more or less what an alternator does (only better), it makes sense that they see it as compatible.

    What is missing from this response is a statement saying that their BMS disconnects the battery from charging at somewhere between 14.0 and 14.6 volts and re-connects charging at ~13.3 volts (below the resting voltage of a fully charged battery). Unless you are stopping charging once the battery is full, you are slowly damaging it. "Float" charging should never be done with lithium (disturbing to see the CTO endorse it). Keeping it at 14.5v whenever you are charging is damaging the battery. Their 15.2v cutoff (3.8v per cell) is appropriate for protecting the battery from immediate damage (if for instance a voltage regulator somewhere in your system fails).

    All that being said, you've got good batteries there. I would just spend the extra couple hundred bucks adding in a proper control to turn the charging on and off unless you can get Stark to say their BMS is doing that at the approximate voltages referenced above.

    Sorry, feel kinda like your thread is getting hi-jacked here on a tangent - I'll go back to silently enjoying this cool build
    No need to be sorry, this is good info. Hopefully we can get a plug and play design that DIY'ers can use.

  2. #122
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    Quote Originally Posted by CoyoteThistle View Post
    The response from Stark is entirely consistent with their position that they are selling a "drop in" lithium battery and since the DC-DC converter is doing more or less what an alternator does (only better), it makes sense that they see it as compatible.

    What is missing from this response is a statement saying that their BMS disconnects the battery from charging at somewhere between 14.0 and 14.6 volts and re-connects charging at ~13.3 volts (below the resting voltage of a fully charged battery). Unless you are stopping charging once the battery is full, you are slowly damaging it. "Float" charging should never be done with lithium (disturbing to see the CTO endorse it). Keeping it at 14.5v whenever you are charging is damaging the battery. Their 15.2v cutoff (3.8v per cell) is appropriate for protecting the battery from immediate damage (if for instance a voltage regulator somewhere in your system fails).

    All that being said, you've got good batteries there. I would just spend the extra couple hundred bucks adding in a proper control to turn the charging on and off unless you can get Stark to say their BMS is doing that at the approximate voltages referenced above.

    Sorry, feel kinda like your thread is getting hi-jacked here on a tangent - I'll go back to silently enjoying this cool build

    I posed this observation to Stark's CTO once again. Here is his response;
    .
    The reader is correct that keeping a charge voltage on lithium cells does stress the cell and deteriorate them. Other lithium chemistries used in laptops and cell are more prone to this. LiFePo4 does have a deterioration effect but not as great as other lithium chemistries. In a perfect control environment we recommend to charge to 14.6V then hold a float at 13.8V . Our BMS does not disconnect and reconnect the charger.



    In your case, if the DCDC charge to and holds at 14.5/6V that can work. The deterioration will not be that great. Also, I’m assuming the DCDC will not be on 24 hrs every day.

    .

    I think the last sentence is key to what is being said.
    Last edited by Terra Ops; 01-10-2018 at 06:12 PM.

  3. #123
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    Washougal, Washington
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    Could you post some more details about your pass through? I'm working on figuring that out in my cab now. Was yours factory rear captains chairs?

  4. #124
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    Quote Originally Posted by lostih View Post
    Could you post some more details about your pass through? I'm working on figuring that out in my cab now. Was yours factory rear captains chairs?
    IMG_20170518_115214905_HDR.jpg

    IMG_20170518_115418103.jpg

    IMG_20170518_115340269.jpg

    IMG_20170518_115244641.jpg

    IMG_20170518_115233170.jpg

    Pass through was installed/created by Rob Rowe at Phoenix Custom Campers.
    The rear captain seats I did myself. The rear bench comes as a 60/40 split. I kept the 40 and purchased another 40 assembly through
    the dealership. Not that hard to do. From my experience, Ram may be the only truck in which you can do this. Cost was less than $1000.00.
    Several years ago when purchasing our Tiger, I think Ford was charging 6K for two rear captains.

    If I were to do this myself, ... first you need a frame to install into the rear wall that will accommodate the boot or whatever method your using. Remove the glass and save as template for aluminum replacement. Cut rear wall to fit frame. Fill in remaining space with aluminum sheet. I would think you could use the Sikaflex 252 to bond and make water tight. Just my thoughts, proceed at own risk
    Last edited by Terra Ops; 01-12-2018 at 04:54 PM.

  5. #125
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    Nice build!
    Do you have any idea of the final build weight and center of gravity of the camper?
    Also do you intend to have any roof rack or other attachment to the shell and what determined the use of Titan jacks?

  6. #126
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    Jun 2011
    Location
    Ventura, CA
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    Quote Originally Posted by Terra Ops View Post
    I posed this observation to Stark's CTO once again. Here is his response;
    .
    The reader is correct that keeping a charge voltage on lithium cells does stress the cell and deteriorate them. Other lithium chemistries used in laptops and cell are more prone to this. LiFePo4 does have a deterioration effect but not as great as other lithium chemistries. In a perfect control environment we recommend to charge to 14.6V then hold a float at 13.8V . Our BMS does not disconnect and reconnect the charger.



    In your case, if the DCDC charge to and holds at 14.5/6V that can work. The deterioration will not be that great. Also, Iím assuming the DCDC will not be on 24 hrs every day.

    .

    I think the last sentence is key to what is being said.
    Thanks for posting this! I think it is the most straightforward answer I have seen from a "drop in" lithium battery seller on how their system is working.

    Yes, I agree that the last point is key too and something I hadn't been considering. Assuming your daily use is close to your 250ah bank capacity, with a 40amp charge rate you won't be in the "overcharge" zone very often even if you're driving all day.

    Stark's answer though is important for other folks out there who are dropping these batteries in to systems designed for lead acid. The way their BMS is working, it is not protecting the battery from typical float charging profiles from shore power converters, solar or whatever folks might be tempted to leave on 24/7 to keep the batteries "topped up". Doing so would definitely damage these batteries.

    btw, that pass-through is super cool!
    2010 Nissan Frontier 4X4, 2014 Yamaha WR250R, 1980 Honda XL250S, 1981 Honda XL500S
    Camper Builds:
    The Original Pro-Rig and Pro-Rig v2.0

  7. #127
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    Washougal, Washington
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    Slick! Thanks for posting!

  8. #128
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    Quote Originally Posted by WYCamper View Post
    Nice build!
    Do you have any idea of the final build weight and center of gravity of the camper?
    Also do you intend to have any roof rack or other attachment to the shell and what determined the use of Titan jacks?
    I'm guesstimating the final weight around 1500lbs. No clue on the center of gravity; all heavy components are deliberately as far forward
    as possible for this reason.
    I'll have solar on the roof but no plan for roof rack as of now. I've had racks in the past that I just don't use. I have contemplated a type of roof top
    tent for additional sleeping.
    Jack selection is due to familiarity. I'm currently using them on my other camper and I like the electric lift. What other type of jack might be used?
    Last edited by Terra Ops; 01-13-2018 at 01:34 PM.

  9. #129
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    Quote Originally Posted by CoyoteThistle View Post
    Thanks for posting this! I think it is the most straightforward answer I have seen from a "drop in" lithium battery seller on how their system is working.

    Yes, I agree that the last point is key too and something I hadn't been considering. Assuming your daily use is close to your 250ah bank capacity, with a 40amp charge rate you won't be in the "overcharge" zone very often even if you're driving all day.

    Stark's answer though is important for other folks out there who are dropping these batteries in to systems designed for lead acid. The way their BMS is working, it is not protecting the battery from typical float charging profiles from shore power converters, solar or whatever folks might be tempted to leave on 24/7 to keep the batteries "topped up". Doing so would definitely damage these batteries.

    btw, that pass-through is super cool!
    I've been very impressed with Stark so far. It will be interesting once the batteries arrive and everything comes together. I think Diplostrat makes an interesting point about voltage and current; REDARC is a well established company with a very good track record. Using two of their chargers, I can confirm that they work as advertised with Lead Acid. Lithium is a whole new world but I suspect that what they are doing will work. Within limits, voltage and amperage are reciprocals - so keeping the voltage high while killing the amps has the same effect as dropping the voltage. Just depends if they have done it properly. Also depends on what is sold in the Australian market.

    Worth noting that feeding a lithium battery 14.Xv is not a problem as long as you stop, or cut the amps, when the battery, not the charger, hits just over 14v. These are the voltages for most commercial available "plug and play" "12v" LiFePO4 batteries.


    Looking back at post #106, REDARC seems to be giving the battery what it needs. This setup should give me the space and weight savings that I'm looking for. Guess we'll see how it comes together

  10. #130
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    Quote Originally Posted by lostih View Post
    Slick! Thanks for posting!
    Thanks, your welcome!

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