12 volt battery charging regimen

Discussion in 'Prime Plug-in Charging' started by Heimhenge, Jan 19, 2021.

  1. Heimhenge

    Heimhenge Junior Member

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    We have a 2018 Prime and use an Evr-Green 320 level 2 EV 32 amp 7.7 kW charging station on a dedicated circuit in our carport. Been working like a charm since we installed it and bought the car (same year).

    Last week the 12 volt battery died. Wouldn't take a recharge. Had to have it towed for a battery replacement and electrical system check. Tech told us we didn't drive the car enough to keep the 12 volt battery topped off.

    We're retired, so the car gets driven maybe 1-2 times a week, short commutes mostly, almost always on electric only given the typical commute distances. Otherwise follow the recommended service schedule.

    QUESTION: That 12 volt battery should last 5-6 years under normal use according to the dealer. Maybe we're not driving it enough to keep it charged? Does the gasoline engine need to kick in to charge the 12 volt battery, or should it be getting charged when we plug in to charge the traction battery?
     
  2. Salamander_King

    Salamander_King Senior Member

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    No, the engine does not need to come on to charge the 12v battery, the car just needs to be in READY mode. When you plug-in to charge the traction battery, the 12v battery gets just a trickle charge to maintain only during the active traction charging but this is not enough to bring the 12v battery back to a fully charged level especially if you are not charging every night for the full duration. If you are driving less than ~50 miles or ~1hour/week, you risk draining the 12v battery charge. The best and easiest solution is to purchase a smart battery charger/maintainer and connect it to the 12v battery occasionally. I found a once a month was sufficient to keep it charged above 12.4v resting.

    This thread discusses some options.
    ONE GOOD WAY TO KEEP 12V BATTERY CHARGED UP | PriusChat

    This is the longer version of the thread discussing the 12v battery maintenance on PP.
    12v Battery Is Discharging, Re-Charge Now ! | PriusChat
     
    #2 Salamander_King, Jan 19, 2021
    Last edited: Jan 19, 2021
    jerrymildred and Mendel Leisk like this.
  3. Heimhenge

    Heimhenge Junior Member

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    Thanks SK. I followed both links and read those threads. Lotsa good tips. Was surprised that nobody mentioned Toyota's recommendations (which I don't yet know) beyond what's in the manual. I'm sure there's many Prii being driven less with the quarantines so they've no doubt been asked the question. I'll play around with that Ready Mode suggestion, but intend to call the dealer and see what they say. Will add their response to those threads.
     
  4. Mendel Leisk

    Mendel Leisk Sunday driver DIY’r

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    Unless we’re driving daily (which almost never happens) I connect my smart charger on the first idle day, and it stays thus till the next drive. I do have the convenience of secure garage and have wired a quick-connect.

    In our 2010’s Owners Manual at least, it recommends to disconnect battery before charging. I’ve found that completely unnecessary and counterproductive, discourages convenient charging. There is also a recommendation for max amperage, worth noting I think.
     
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  5. Salamander_King

    Salamander_King Senior Member

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    Did you have a new 12v battery installed at a dealer? Did you have to pay for it? I have read some people who had a similar problem as you had successfully claimed warranty coverage and got a free battery replacement. If you had to pay for it, you may ask your dealer nicely for refunds or reimbursement as long as your car was still within 36mo/36Kmile.
     
    #5 Salamander_King, Jan 19, 2021
    Last edited: Jan 19, 2021
  6. Heimhenge

    Heimhenge Junior Member

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    New battery was installed by a local mechanic who got the replacement from the dealer, so that's cool. Waiting for a response from the dealer now regarding what went wrong and what remedies may exist.
     
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