12v battery was dead and now alive?

[vulgaris_magistralis]

That dreaded day is finally here. Left my car on Friday on half a charge and on Sunday morning, the remote wasn't responding and the car won't start. The roadside assistance came and had no idea to fix but since I saw the 12v problem in so many posts, I suggested charging the 12v battery a bit. And viola! the car was back again.

They checked the integrity of the battery with the load test and told me that the battery is dead. I drove to the dealer and they told me that the battery shows no sign of any problem and there might be a software issue with the battery drain. Although I gotta say, if it fails again they told me that they will replace it under warranty. I'm a bit confused; any comments on the questions below would be appreaciated.

1- How come the dead battery just got resurrected? I remember something similar happened to someone in forum (brought dead battery to dealership but no problem found), but couldn't find the post. If that person tells me what happened I'll be glad.

2- I'm glad that the car died in front of my house. If it happened to me on the road somewhere, it would be a whole other story. It made me think of getting portable jumpstarters like this: https://www.amazon.nl/-/en/Starter-Port ... Z4KL8?th=1
Would these things be enough to start the car? Does anybody have any experience?

3- The million dollar question: how the hell did this happen? Since the 12v problem is all over this forum, I'm familiar with the issue. So I was extra careful not leaving the lights on or not hardwiring a dashcam. But it happened nonetheless and I can't understand what was the reason.

[EEEE]

1) There are many ways to test a battery. I suspect the dealer did not do a proper test. It sounds like the mobile mechanic did a reasonable job of testing the battery. A drop test involves putting a big load on the battery and checking it can kick out ~100amps. If it can, the voltage should only 'drop' by so much, and it can be determined that the battery can indeed pump out some power, and cannot be that knackered. The drop test would indicate a knackered battery if the voltage dropped too much. This may be the case if the battery was not fully charged (you do not say how long it was charged for) A simplistic check may just be to test the open circuit voltage, see 12v+ and say 'its fine'. There is no quick way to test the battery definitively. Be sure though, if the voltage went lower than 11v, its passed its best and better off replacing it. Yes it can be charged up, Yes it might show 12v+ (especially if you just drove it), but does it really have the capacity it should? probably not. I'm waiting for my discharge capacity tester to turn up, and see just how much of the 45ah capacity the Panasonic OE battery still has. A trip to the dealer to prove a fault is a pain for the customer, I just bought a new battery (and a bigger one at that)

2) Yes something like that is fine. If the car is only a little bit flat, it should be enough to get it powered up, HV battery connected, and then the 12v charging system will take over and keep the car powered. I have had it 2 times that the jump pack got the car going, and 1 time when the battery was so flat it all turned off as soon as it was removed.

3) The car is badly designed / poorly integrated in this respect. The 45ah battery should be enough if the 12v system is supplemented by the HV backed system, but sometimes for reasons unknown, the 12v system is left to simply run out. This includes showing the infotainment to your mates with the door open, possibly software update pending which keeps the infotainment awake over night, possibly door handles not popping back in keeping the keyless entry system awake. Who knows. Black boxes talking to black boxes, what happens inside them is hard to tease out.

Fitting a BM2 wont help you with a flat battery, it wont really warn you either (bluetooth range too short) but it will at least give you some idea what the car is doing. Hopefully from that the situations where the 12v battery is not being charged/maintained can be avoided.

For example, opening the drivers door, sitting in it, turning it on, getting out, putting the seatbelt on and the drivers door open - this will flatten the battery in about 10 minutes (possibly weakened battery at this point). The car wont turn off, it wont warn you, it wont charge the 12v battery. One by one the warning lights will come up on the dash, headlights will turn off and then the screens will just die and the rear cabin lights will flicker...

Having the car plugged into the mains doesn't necessarily charge the 12v battery either. Say you drive a few miles and the HV is on 95%, plug in to charge, charging is completed probably in under and hour. The 12v charging only takes place for that less than 1 hour period. Doesn't matter if the car is plugged into 24/7 mains for 3 days, it will only charge the 12v for that 1hour. Even then the 'charging' is not very good, just 13.3v flat. No intelligent charging or staged charging. I suspect this is what kills off the 12v battery.

I also suspect that the intelligent charging that does take place when the car is in motion, is too conservative, and this leads to quicker degradation than ideal. Not helped by such a tiny battery in the first place.

[Ebenezer]

My 12v battery died on Saturday 11/11/23. It was fine the day before. I got the AA to come out and test it, they said it was taking about 0.3amps and should be taking 20-30amps of charge. It was the first cold night it autumn when it died but I hadn't been sat in it doing anything to drain the 12vbattery.

The battery was 4 months outside of warranty.

I got AA to supply and fit a new battery and everything seems ticketyboo now.

Does this sound like an issue that should be raised with Honda somehow or is it to be expected?

[vulgaris_magistralis]

1) There are many ways to test a battery. I suspect the dealer did not do a proper test. It sounds like the mobile mechanic did a reasonable job of testing the battery. A drop test involves putting a big load on the battery and checking it can kick out ~100amps. If it can, the voltage should only 'drop' by so much, and it can be determined that the battery can indeed pump out some power, and cannot be that knackered. The drop test would indicate a knackered battery if the voltage dropped too much. This may be the case if the battery was not fully charged (you do not say how long it was charged for) A simplistic check may just be to test the open circuit voltage, see 12v+ and say 'its fine'. There is no quick way to test the battery definitively. Be sure though, if the voltage went lower than 11v, its passed its best and better off replacing it. Yes it can be charged up, Yes it might show 12v+ (especially if you just drove it), but does it really have the capacity it should? probably not. I'm waiting for my discharge capacity tester to turn up, and see just how much of the 45ah capacity the Panasonic OE battery still has. A trip to the dealer to prove a fault is a pain for the customer, I just bought a new battery (and a bigger one at that)

2) Yes something like that is fine. If the car is only a little bit flat, it should be enough to get it powered up, HV battery connected, and then the 12v charging system will take over and keep the car powered. I have had it 2 times that the jump pack got the car going, and 1 time when the battery was so flat it all turned off as soon as it was removed.

3) The car is badly designed / poorly integrated in this respect. The 45ah battery should be enough if the 12v system is supplemented by the HV backed system, but sometimes for reasons unknown, the 12v system is left to simply run out. This includes showing the infotainment to your mates with the door open, possibly software update pending which keeps the infotainment awake over night, possibly door handles not popping back in keeping the keyless entry system awake. Who knows. Black boxes talking to black boxes, what happens inside them is hard to tease out.

Fitting a BM2 wont help you with a flat battery, it wont really warn you either (bluetooth range too short) but it will at least give you some idea what the car is doing. Hopefully from that the situations where the 12v battery is not being charged/maintained can be avoided.

For example, opening the drivers door, sitting in it, turning it on, getting out, putting the seatbelt on and the drivers door open - this will flatten the battery in about 10 minutes (possibly weakened battery at this point). The car wont turn off, it wont warn you, it wont charge the 12v battery. One by one the warning lights will come up on the dash, headlights will turn off and then the screens will just die and the rear cabin lights will flicker...

Having the car plugged into the mains doesn't necessarily charge the 12v battery either. Say you drive a few miles and the HV is on 95%, plug in to charge, charging is completed probably in under and hour. The 12v charging only takes place for that less than 1 hour period. Doesn't matter if the car is plugged into 24/7 mains for 3 days, it will only charge the 12v for that 1hour. Even then the 'charging' is not very good, just 13.3v flat. No intelligent charging or staged charging. I suspect this is what kills off the 12v battery.

I also suspect that the intelligent charging that does take place when the car is in motion, is too conservative, and this leads to quicker degradation than ideal. Not helped by such a tiny battery in the first place.

Thanks a lot for the detailed explanation! Can I ask which battery that you went with?

[EEEE]

I bought a Yuasa 5000 series '005' size battery. It's exactly the same as the OE battery except instead of being 4.5inches deep, its 6 inches deep which is what gives the extra capacity.

If you do fit a larger battery, the original bracket will need replacing with something else, and you will need to remove the battery tray.

Yuasa do sell a '053' sized battery that is a direct OE replacement (I bought one of these as well so that I wasn't stuck with no options if I couldn't get the bigger battery fitted).

So far with my limited BM2 logging on the old battery, the voltage holds higher for longer. Whether this proves the battery is superior or simply that the old one was nackered I wont know until my battery discharge tester turns up.

[logorrhoea]

2- I'm glad that the car died in front of my house. If it happened to me on the road somewhere, it would be a whole other story. It made me think of getting portable jumpstarters like this: https://www.amazon.nl/-/en/Starter-Port ... Z4KL8?th=1
Would these things be enough to start the car? Does anybody have any experience?

I've made it here as I'm another victim of the 12v battery just dying for no reason and not recharging (staying dead) despite me driving the car for 90 minutes.

Anyway, I bought one of those portable jump starter things and it worked great. The one I got was I needed to activate the boost function to give it enough welly to bring the Honda back to life but other than that, no problem. The charge on the battery went down from 100% to 72%, so I reckon it's good for another three jump starts if I really didn't have the opportunity to recharge.

[EEEE]

I doubt the Honda e will charge a completely depleted battery. It is best removed from the vehicle and charged using a dumb analogue charger, until such point that an intelligent/smart digital charger will continue charging.

The Honda does have a current sense on the negative battery terminal, and I suspect this is part of the problem why it will not charge. It will attempt to charge it, see that it is not accepting current, and stupidly assume that it is fully charged (As in an intelligent charger , the bulk charging takes place until the current falls below a low threshold). This is why some intelligent/smart digital chargers will also not charge a very flat battery.

Once its gone flat a few times as mine had done - the effective capacity appears less than half from my testing (Didn't even get 20ah out of the rated 45ah). The Panasonic OEM battery appears to be their most basic in the range. Whilst changing it doesn't fix the problem of whatever causes the drain, it buys you time between failures. Looking at my BM2, the standby voltage after resting is noticeably higher with the new battery.

[5thcivic]

The Honda does have a current sense on the negative battery terminal, and I suspect this is part of the problem why it will not charge. It will attempt to charge it, see that it is not accepting current, and stupidly assume that it is fully charged (As in an intelligent charger , the bulk charging takes place until the current falls below a low threshold). This is why some intelligent/smart digital chargers will also not charge a very flat battery.

I do few miles and regularly smart charge (different chargers) both the E and the Jazz (both have sensors on the negative), both have the permanent connected charge lead directly on the negative terminal.
We have had the debates about you must connect with the sensor in circuit, you must connect to a bolt in case of hyrogen explosion, you must disconnect the battery because the book says so, etc etc, etc, but with smart chargers and sealed batteries I have never had a problem in many many years with 5 Civics and the present 2 cars.
The only time a Civic run down to zero (because in hospital) the smarts would not charge because too low a voltage, I still have an old analogue transformer charger which raised the voltage enough for a smart to take over.
Would the current sensor module affect a smart charger if in circuit? the car is off obviously. I would assume the software would be smart enough to measure the 12V or current on bootup and act accordingly if charging is needed when underway?

[EEEE]

To clarify, the sensor 'method' of controlling the in car charging of the 12v battery may fail to charge the 12v battery if its really flat. 14.6v would be applied, the battery wont accept the charge much, the sensor sees that very little current is flowing into the battery and goes 'oh, this is what happens when its fully charged, ill stop now'. This might explain the constant cycling I saw on the BM2 of the old battery which was on its way out. The new battery seems to charge for the entirety of my 30 minute commutes now, where previously I would see 2 or 3 cycles of charging at 14.6v.

Charging it in car with an external charger, the sensor on the terminal makes no difference to the operation (since you are connecting pre sensor, it can make no difference). I dislike charging vehicle batteries when they are connected, because you do not know at any point if some part of the car will wake up and 'upset' the charging monitoring or cause some other problem (especially with the e liking to wake up and drain the battery, or wake up and monitor and charge the battery).

I'm sure if the car is completely off, it can be charged up fine on the vehicle whilst connected. But I wouldn't like to do it whilst opening/unlocking the car, and certainly not whilst it was HV charging at the same time. Most chargers will have protection, but its just not worth the risk in my mind.

[5thcivic]

Thanks, yes I only connect the charger after the car is double locked with the bonnet on first click for the cable gap, and only then switch on the charger power. Trying it while the HV charger is connected and working would indeed be imbecilic. The red led does not blink with the bonnet open but the car is locked and is shown as locked in the app. After charger power off and disconnect you only need to close the bonnet for indicator flashes and the dash led to blink normally.

Tell the truth I used to update the maps on Civics with the charger connected in accessory mode in the garage for micro bricking safety (when the book said run the engine for 20 minutes to guarantee voltage) with no problems ever. Now I just keep the usb stick for the next trip out and let it do its stuff.