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Battery charging setup in car trunk

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    Battery charging setup in car trunk

    I kinda feel bad for being a noob and asking for advice on this without posting much but I've found very little info on this topic and would be surprised if it's not something that many have wanted to do. Hopefully this could help others who are looking for a similar setup.

    Have: Two Luna 52V Wolf Packs and two Luna 52V Advanced Chargers which output 300W max as battery approaches full charge.

    Goal: A setup in my trunk that would allow for 2 full charges of both batteries = 4 full charges total. To allow for up to 3 long rides per day with quick trunk charging in between - that way I don't have to find a place to stop and charge them and wait for them there. I go on a lot of weekend road trips and want to be able to keep moving - driving, wandering, doing other things without staying put while they charge.

    On a really tight budget.

    52V x 5A (for fast charge) x 2.5 h for fastest charge (or just 52V x 12.5 A-h) = 650 W-h required per battery x 4 charges = 2600 W-h total required; factor in loss (one source hints at 11%, another hints at ~16% if I remember correctly) = approx. 3000 W-h or 250 A-h with a 12V battery in trunk.

    Another way of looking at this, charger max is 300W x 2.5 h for fast charge = 750 W-h x 4 charges = 3000 W-h, loss will be partially compensated by most of that time charger is not using full 300W.

    So far the lowest-cost setup that I've been able to find is:

    $350 deep cycle RV battery:

    https://www.ebay.com/itm/Trojan-J185...wAAOSwGOxXAs7g

    at 225 A-h = 2700 W-h, this would compromise a little on length for my last ride but probably not a big deal since most days I'd probably only have time for 2 rides as opposed to 3.

    $34 charger for the deep cycle battery:

    https://www.ebay.com/itm/Attwood-Mar...8AAOSwMT5dJJHw

    $120-170 on Ebay for either 1000W or 1500W (TBD) "pure sine power inverter"

    Total: $350 + $34 + $170 = $554. That's out of range, at least for a good while.

    I'm posting this to see if anyone has suggestions for bringing the cost down (by and large, for the battery) and to see if anyone is aware of perhaps some other factor that I'm not considering that would cause this not to work.

    Used big deep cycle batteries are next to impossible to find on Ebay or Craigslist. Used is not a concern because I don't expect to expose it to all that many cycles long-term. There actually is a Trojan 150 A-h available in my area (a big rarity). I'm not opposed to having several of the exact same battery in my setup but against the impracticality of a setup with two different-sized batteries because it just seems klunky. But leaning more towards it because it may be the only way to get enough power at low-enough cost. I would then need 100 more A-h which could be delayed until something comes up on Craigslist. And go with two rides per travel day for now. Does anyone have thoughts or experience regarding such a setup with multiple batteries? Does hooking them up in series effectively make them one big battery?

    Here's the only thread I was able to find that's moderately relevant:
    https://electricbike.com/forum/forum...fied-sine-wave
    It talks about charging while driving. The Best Buy tech (likely not the best source of information) says it would put a lot of wear and tear on my alternator, with the alternator providing that much power for that long and that frequently. This is why I'm looking at a standalone trunk setup, separate from the car alternator. Best Buy tech said that, due to losses in the inverter and such, it would require a HUGE battery similar to an electric car battery (are electric car batteries available for cheap?) but again I don't trust this tech to have enough experience to be accurate.

    #2
    One basic question is, is it really true that running ~500W continuous for a few hours on occasional days will degrade the alternator subtantially long-term? If this is not true, then I may be able to just get an inverter, depending on if and how I'd need to run cables from the car battery or whether enough power can be pushed thru the little cigarette lighter plug (sounds unlikely, you'll probably tell me I'm ignorant because it can't transmit that many amps but just wanted to make sure).

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      #3
      The ming he 5210a is a boost solar charge controller that also works off 12v. You set your charging parameters

      Comment


        #4
        My genasun controller with a 160 watt panel gets me a net range boost of more than 60 miles per day

        Comment


          #5
          Careful when charging, I almost burned my house down while charging my sons Li battery and I wouldn’t be the first. So now I pay great attention to what and where I charge. I’m very close to where a dive boat just caught fire in the middle of the night and sank with 34 people, I have a bad feeling they will find charging Li batteries at fault.

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            #6
            Charge while driving. Charge outside. Have redundant battery protection. Good charger and good bms. Set charge to max charging at 4.1 volts per cell. Keep battery well orotected. Do not exceed 2 amps for 13.5 ah 52 volt battery. Watch out for high temperatures And battery damage.
            my solarpanels provide for 1 amp while driving and 2 amp when parked next to my supercharger. 120 watt on bike. 160 watt on trailer.
            charging in the trunk of a hot car above the gas tank with a lead acid battery off gasing hydrogen gas with nonstandard charging heat producing electronics seems expensive and dangerous.

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