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solar chargers? VW OBD2 port chargers? OBD2 disconnect/reconnect cycles?

Discussion in 'Gen II Prius Main Forum' started by cwerdna, Mar 13, 2011.

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  1. cwerdna

    cwerdna Senior Member

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    My Prius doesn't get driven that much anymore (sometimes left dormant for a few days at a time) and much of the time, when I do drive it, many of the trips are short (usually <3 miles, one way). So, I've been thinking of a solar charger for the 12 volt (now an Optima Yellow Top).

    Float chargers or battery tenders powered by AC are out of the question for me. I live in an apartment and the car is parked outside. I can't leave it unlocked w/wiring snaking into it nor leave my car powered on for hours at a time to charge up the 12 volt.

    Obviously, since the cigarette lighter plugs aren't hot when power is off, those won't work. I don't care to rewire them so that they are.

    I dropped by my Fry's and saw FRYS.com | Sunforce and FRYS.com | Solar. From some earlier threads, it sounds like I need at least a 5 watt panel. If I were to get one of these, I plan on hooking it up to the 12 volt terminals in the trunk area. No, I don't plan to disconnect the 12 volt from the rest of the car. That's too much of a pain.

    Some folks have mentioned the VW panels w/OBD2 port. I did find a few on Ebay and might try a local VW dealer. :) Only thing is, I use a ScanGauge so I'd have to disconnect it to use the VW panel. That's no big deal but I'm wondering if anyone has specs on the typical # of disconnect and reconnect cycles OBD2 connectors are rated for on cars. I don't want to wear out or damage the connector on my Prius.

    Thoughts? Don't bother?
  2. Flaninacupboard

    Flaninacupboard Senior Member

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    It's a sensible move. How about you get a spoiler from a wrecked prius, and build a panel into that?
  3. wick1ert

    wick1ert Senior Member

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    I don't think I've ever seen this dilemma before WRT the OBD port. I would imagine that there may be a bit of wear after several hundred/thousand uses of the OBD port. Think of it being similar to a household outlet, in terms of how the prongs go in and out.

    If it were me, I would probably just hook up in the trunk ports. You could leave it hooked up 24/7 and not have to worry about unhooking and hooking up different items every time you drive the car.

    Sometimes simple is better.
  4. Patrick Wong

    Patrick Wong DIY Enthusiast

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    My impression is that the Seattle area doesn't have much sunlight, much of the year. I think you should consider getting at least qty 3 of the 5W panels, connecting them in parallel. That will yield 15W or ~1.3A when the panels are in full sunlight. I assume that much of the time the panels will not be in full sunlight, and power output will be significantly degraded. You might be lucky to get useful output 3-4 hours a day.

    Considering that much of the year there isn't much sunlight, and although this will be painful to do, the best solution for you would be to 1) remove the 12V battery, carry it into your apartment, and hook up a 12V battery charger. 2) Once the battery is fully charged, then bring it back out to the car. Don't connect the negative side until you are ready to drive the car. 3) 2x per month, repeat the battery removal and charging process.

    Or, get used to the idea that you will buy a new 12V battery every couple of years or so. That's not the worst thing that might happen to you.
  5. uart

    uart Senior Member

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    Has anyone measured roughly what is the current drain with/without the SKS system enabled?
  6. seilerts

    seilerts Battery Curmudgeon

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    I'd have serious concerns about some cheap POS solar thingy cooking my Optima battery, as well as the lack of insolation in the cold dark Seattle winter. Best practice is to use a charge controller in any case, but that got me thinking...

    I love these little chargers, I have five of them: Dynam Supermate DC6 DC Multi 1-6S LiPo Charger/Discharger/Balancer

    What you could do is get one of these and a portable jump pack. It would be the portable jump pack that gets removed from the car and charged in the apartment, rather than the car battery. Basically, the charger will regulate the current and step-up the voltage from the jump pack to charge the car battery. If the jump pack falls below 10.5V, then the charger will stop, otherwise it will keep going until hitting either a full charge on the car battery or a programmable amp-hour delivered limit. It is very accurate for the amount of charge delivered, down to 0.001 Ah. Max charging amps for PbA is about 3.5A, sound familiar?
  7. uart

    uart Senior Member

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    I think that for most of them the average current is way too low really overcharge or damage the 12V battery. The real problem is with the current so low will they be enough to stop the battery going flat. I think if you size it correctly it could definitely help in extending the safe non-operating period .

    I think it would be interesting to measure the average output (over a day) of that 5W cell and compare it with the measured current drain that the car draws when it's off. There's a bit of leeway here because the self discharge of the 12V battery increases considerably when it's near full charge, which of course takes away from the effective charging current.

    BTW. does anyone know what the typical current drain is for the Prius, with sks and also without sks
  8. MGnut

    MGnut New Member

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    Hi seilerts.
    What is the input voltage needed to drive these, I thought of a simular thing here in the UK, but do these jumper packs give enough voltage to make these operate, I am sure that mine only gives a 12 volt output, so you can also start a car from it.

    Colin EL
  9. Patrick Wong

    Patrick Wong DIY Enthusiast

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    0.02A with the Smart system engaged. Hence, ~0.5Ah current drain per day.
    1 person likes this.
  10. cwerdna

    cwerdna Senior Member

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    Thanks for all the suggestions!


    Hahha.. Yes, it's true. It is rainy and cloudy much of the time in the Seattle area. However, that doesn't mean we don't get no light. It's just not direct sunshine and yes, that means a solar panel won't be emitting max output.

    At Fry's prices, 3 5 watt panels would be $150 + tax. They do have a HUGE 15 watt panel (FRYS.com | Solar) which is $100. I don't think it makes sense to bother w/spending even $100 on panels to preserve my Optima battery.

    As for the removing the battery, charging it up and reconnecting, 2x a month, that's too painful and time consuming for me. :( I aleady changed the OEM battery to the Optima myself so I have a good sense of how long it takes.


    Nah, that's too much trouble for me.


    As for leaving a panel hooked up in the trunk ports, the Sunforce panels have clips and I'd probably want to disconnect them before driving since they might come loose and cause a short, if I'm not careful.


    I'm not too concerned about cooking the Optima battery given the low output of the panels and not getting much direct sunlight. I was thinking of just hooking up my portable jump pack in parallel to the car via the trunk terminals (assuming its clips are small enough) and leaving it there. But then, I'm a bit concerned about outgassing (if any) from the jump pack in an enclosed car. They were never intended to be left attached in use inside a car for days. The normal use case is to only use them outside a car for a few minutes.

    As a precaution now, I've disabled SKS on my car most of the time via the button under the steering column. I think I'm going to consider getting a VW OBD2 panel, a single Sunforce 5 watt panel (or similar) or just be resigned to having to replace my 12 volt more often.
  11. wick1ert

    wick1ert Senior Member

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    Is it possible to wire a bunch of say, regular AA batteries, to create your own sort of 12V charger? Then you could just re-charge them as needed, and if a cell dies, they're pretty easy to find replacements for.
  12. uart

    uart Senior Member

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    Hi cwernda. My suggestion would be to give the single 5W panel a try and measure the current output under various light conditions. It might be enough to at least maintain the battery with sks off. What you want to find out is if it can still charge the battery under diffuse (non direct sun) light conditions. Perhaps try it just sitting atop the luggage blind in the hatch.
  13. uart

    uart Senior Member

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    I'd use the clips while you're testing it out, but if it works out then it would be worth the effort to make proper connectors for the 12V battery terminals and make it a permanent thing. That's really the big advantage of using a solar panel in the first place, simple maintenance free operation.

    Here's a tip. If it does work and you decide to make a permanent connection, include a small diode as part of your connection setup, right at the battery positive terminal. Though the panel already contains such a diode built in to prevent dark discharge, adding one right at the battery terminal gives you confidence that no matter what happens to the wiring past that point it simply cannot short out the battery.
  14. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Each silicon diode added causes 0.7V drop, BTW.
  15. uart

    uart Senior Member

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    Yep but the open circuit voltage of the panel should be around 20 volts so I think it's worth adding a diode at the battery for piece of mind. :)

    BTW. A schottky diode it will only have about half that voltage drop of the Si diode, if the volt drop is too much of a concern.
  16. seilerts

    seilerts Battery Curmudgeon

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    Colin, a jump pack is the same as a regular car battery to first order. When the jump pack is fully charged, it will have about 12.6V at the cables, and will fade to 11V when near depletion. The Supermate will act as a step-up regulator, supplying up to 14.7 forward voltage to the battery being charged, while draining the jump pack down to whatever is programmed as the low voltage cutoff, 10.5V by default. I started a new thread with pics in the technical section.
  17. cwerdna

    cwerdna Senior Member

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    update: will be getting a VW solar panel for free :)

    Update: I called the closest VW dealer to me and they claimed they used to receive the panels w/their incoming new cars when they received cars directly. But, they claimed that don't receive their cars directly from VW anymore so the panels are removed and destroyed (per VW instructions) before they even get to the dealer. IIRC, he claimed they were worth like $3-5.

    I called another dealer today and the parts dept. guy doesn't recall if new VWs still come w/them but he had one w/OBD2 port that he'd give me for free. I'll be heading over there when I have a chance (dealer isn't that close to me).

    I mentioned to him about how I heard about these panels and how I'd seen some on Ebay. He said that they were "lossey goosey" on these at one point. At one point, VW actually wanted them back and other times they didn't. He said that ones I see on Ebay were likely from personnel of other dealers taking them and profiting from them. He finished by mentioning that at one point, they were supposed to included w/the car to buyers, to which I added, that could be another source for Ebay panels.
  18. cwerdna

    cwerdna Senior Member

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    OBD2 Y-cable with ScanGauge and VW solar panel?

    In order to reduce the # disconnect/reconnect cycles on the Prius' OBD2 connector, I'm thinking of getting a splitter like Cable, J1962M to 2-J1962F, Y-Cable, 1ft - OBD2Cables.com. I'd then leave my SG always connected. The VW OBD2 solar panel would either always stay connected or I'd take it off before driving (if it gets in the way).

    I'd rather potentially wear out the connector on a y-cable than the one on my car. I know the SG always gets power, even when the car's off.

    Anyone see a problem with this? It seems like pins 4 and 16 are supposed to be battery ground and positive, respectively.
  19. Jimbo69ny

    Jimbo69ny Active Member

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    Did you ever purchase the VW panel?
    I used to sell cars at a dealership and I have one. I am going to try the same thing you did,
  20. cwerdna

    cwerdna Senior Member

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    I got one for free from a dealer. I also bought the splitter I mentioned to reduce the # of cycles on the car's connector.

    I don't use the VW solar panel much anymore. I've moved and now have much longer drives.
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