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12v battery dead.

36K views 106 replies 21 participants last post by  Keith Alexander 
#1 ·
This morning on approaching the car the wing mirrors failed to open and pressing the button on either the door or key fob had no effect.
Car had been on charge overnight (rolec) and was fully charged.
Called out green flag who tested the battery first off and it was failing to register a reading. (first EV the guy had ever been out to).
Connected jump pack , unplugged charger cable and car started as normal.
Had a small drive , switched off and on again with no problems.
This evening its dead again so I'm guessing a new 12v battery is required.
Car is 30 months old with 55000 miles and a 30kw.
Any particular type of battery I should go for? Current battery is 45 ah and 450 (I think) cca.
Should I opt for more ah and pay little or no regard to cranking amps as it doesn't crank?
Any suggestions for which type/ brand of battery to purchase tomorrow greatly appreciated.
Many thanks
Tony
 
#42 ·
How do they justify £200+?
Nah just a common or garden lead acid replacement. Don't even start me on dealer prices. Just had an MOT where they advised that tyre tread was between 3.2 and 4.0 mm and kindly offered to replace tyres at around £90 per corner for Nexens. When I declined their kind offer they offered to do all 4 for £320. Yes I can get them cheaper but more importantly I've probably got another year's worth of wear to get through first.

Do we think a gel equivalent is worth the extra and if so any recommendations? My wife likes the car so will probably keep for another year or two (most likely until I'm ready to replace my MG ZS and she'll inherit that ;) )
 
#44 ·
Gels can last longer but technically they require a slightly different charging regime so you may well find it doesn't do as well as you'd like in practice, unless the car systems are setup for it (or can be coded for it). In particular they aren't very temperature stable and they are very sensitive to overcharging (they require lower charge voltages than other types of lead acid). For £50-60 batteries are consumable and very recyclable, so I might be inclined to just stick with standard. If kept charged it will last for a decade or more.
 
#47 ·
Some bad news. The YUASA replacement battery has failed after just a couple of months. I have barely used the car due to covid and the fact that a safety recall had been issued on the electronic parking brake and there was about a month before the dealer could fit it in. I daresay we had not under taken more than 20 journeys and covered 100 miles in this period. I twice had 12v problems and needed to stick the battery on charge in this period. Couldn't identify that anything had been left on that might drain the battery.

Got the main dealer to check that the car was charging the 12v when in for the recall. They confirmed the car was fine, diagnosed the battery, found it faulty and in need of replacement.

Have spoken to battery supplier who maintain that it would not be covered under advertised 4 year warranty as they believe it had been damaged by external factors, such as overcharging, undercharging, deep cycling, wear and tear.

Where do I do from here? Small claims court? Suck it up (write off the replacement battery and purchased one at much higher price from main dealer)?
 
#49 ·
Well I have run an EV for 4 years and currently run the Soul and an MG (plus an ICE). I've never regularly charged the 12V and this is the first time I've had any problems. Ordinarily I just charge the traction battery, use the car, service as required and as soon as the 12V battery starts playing up (generally after at least 3 years) simply replace it. Maybe I've been lucky?
 
#51 ·
This morning on approaching the car the wing mirrors failed to open and pressing the button on either the door or key fob had no effect.
Car had been on charge overnight (rolec) and was fully charged.
Called out green flag who tested the battery first off and it was failing to register a reading. (first EV the guy had ever been out to).
Connected jump pack , unplugged charger cable and car started as normal.
Had a small drive , switched off and on again with no problems.
This evening its dead again so I'm guessing a new 12v battery is required.
Car is 30 months old with 55000 miles and a 30kw.
Any particular type of battery I should go for? Current battery is 45 ah and 450 (I think) cca.
Should I opt for more ah and pay little or no regard to cranking amps as it doesn't crank?
Any suggestions for which type/ brand of battery to purchase tomorrow greatly appreciated.
Many thanks
Tony
Hi Tony, just changed OEM battery to Exide EL600 Enhanced Flooded Battery. Its 60Ahr instead of the original 45 and it can stand a much lower depth of discharge and still recover, about 3 times the cyclic life. It's only a wee bit more expensive. The car had a lot of "off" battery drain so is pretty hard on its 12v storage. You may need to trim a tiny corner out of the battery tray to accommodate the additional length.

I have a separate post on this forum.
 
#52 ·
As I posted higher up, I replaced my original battery with the Yuasa and so far so good. The car is used nearly every day, and the traction battery is charged every 5-6 days (20/30 to 70/80% - 5hr 20 min @16A rate).

Having removed the "failing" original battery, I put it on a reconditioning (gassing) charge and have been monitoring it on the shelf. It holds 98% charge and the SOH is 68%. The battery tester recommends a new battery at below 60%. I have a theory that the tester gives a false (pessimistic) reading when it is installed in the car, due to the battery monitoring electronics, so your Yuasa may still have some life in it if they did not disconnect it before testing (that is what most garages do).
 
#54 ·
Had this problem yesterday after not using the car for any long runs. We have a 2018 Kia Soul EV, but have only been using it recently for "click & collect" shopping runs, in the evening, to a supermarket a couple of miles away.
Therefore, the car has not needed to be charged up for a at least a month, as it has stayed between 60 & 50%.
I put 12v battery on charge yesterday and all seems OK now, but does anyone know if the 12v battery also gets topped up when charging the traction battery or is it only when the car is on a run?
If it gets topped up when charging the main battery, I could put it on charge once a week for 10-20 mins to replace any charge used.
 
#55 ·
I am not sure at what stage in the charging process the aux. battery is charged - I have seen it said that it happens during the last part of the charge, in which case a partial charge (because you do not want to go above 80% if you are only doing short runs) may not help. Using a trickle charger would be fine, or you can just leave the car in the "ready-to-drive" state for a short interval every few days. In that condition, the dc-dc converter is charging the aux. Note: This does not happen in the ACC state (amber lamp).
 
#61 ·
Thought this might be of interest in being able to see SOC of 12v Battery
View attachment 140414

Car Charger LED Cell Phone Cigarette Lighter USB: Amazon.co.uk: Electronics
I've got one similar to that. When the car is first turned on I can see it change from about 12 volt and quickly increase up to about 14.2 volts when the DC-DC converter is running. Trickle charging the flat 12 volt battery for a few hours and doing a longer run yesterday, appears to have cured the problem.
During lockdown, if I don't need to do a longer run, I will in future take the 12 volt battery out and trickle charge it at least once a week, for a few hours, to prevent it happening again.
 
#64 ·
If by Utility Mode you mean switching on without pressing the brake pedal, that will not charge the aux (At least not in the 2018 and prior models).. The dc-dc converter is only operational when the car is in ready-to-drive mode, i.e the brake pedal is pressed when switching on.
 
#66 ·
#71 ·
For starters a reminder to the Newbies this thread relates to the original Soul so some of the following is that model specific.

We are currently getting around 10-14 days (depends on the temperature) out of the weedy little 12V battery before the systems relatively high parasitic loads have discharged it to the point the car won't unlock properly or boot up into drive mode, i.e. all the symptoms described previously.

Before I continue it is worth mentioning a few things:

SOC = State of Charge
DOD = Depth of Discharge.
OBC = on board charger (HV circuit)
DC-DC converter = pseudo alternator (12v circuit)

Lead acid batteries take many hours to fully charge especially if the bulk voltage is too low and in my car the output from the DC-DC converter at 14.3V is low 14.6v or even at these temperatures, 15V would be better.

FYI
The higher voltage increases the amount of time that a high level of current can be absorbed before the batteries internal voltage equals that of the charger and which point current flow rapidly drops A decent multi stage battery will raise the SOC to around 80% at this stage but feed the battery a lower voltage and it will be less often around 60-70% Soc before the current tails off.

I suspect the DC-DC converter is simply an Alternator emulator rather than a true multistage charger which is a shame.

Lead acid batteries have reduced capacity as they get colder:
Lead acid batteries when new are rated at 100% capacity at 25C.
At 0C they are typically only good for 80% at -20C around 50-60%
Emphasis on the above is when new!

All batteries degrade slowly over time through use, this can be reduced by being permanently on float charge when not in use and by taking as little as poss. out when being used.
Lead acid batteries last for years if only discharged by 5-10% between full recharge cycles, hence why your average car battery lasts ages, cranking an engine takes very little out of it.

Put any battery through a prolonged DOD and leave it like that for a few days, (which is typical of what is happening in this situation) and permanent damage due to sulphation begins to occur.
A sulphated battery never regains 100% capacity. It is a vicious circle the more deeply and more often a lead acid battery is heavily discharged the shorter its overall life will be.

Due to the constant gradual loss of capacity over time the constant discharge from the parasitic loads means each time there will be a proportionally slightly greater DOD hence it can appear to have gone flat sooner the next time, maybe by only a few hours a time but slowly that becomes such a pita it has to be replaced. Our battery may be approaching that point now.

We know that in the accessory mode the 12v DC-DC converter does not operate.
I thought I would therefore just double check that when the OBC is connected to the EVSE charger and charging that the 12v battery is also being charged by the 12v DC-DC converter

The good news is yes it does, the bad news is potentially that charge window will not for long enough.

Yesterday I connected one of my BM2 monitors (I do electrical installs on camper vans and use lots of these) to the Soul
I had the timer set for 00:30 to charge the car to 80%.

That can be seen on the blip in the graph, as the 12v battery drops slightly, but because the car was already at 80% obviously nothing charging wise happened.
This morning I jumped in around 09:30 and to force a charge I set it to charge the traction battery to 100% starting at 11:00AM.

You can see that whilst charging the traction battery it also started charging the 12v battery until I stopped the charge at 12:45.

During lockdown with significantly reduced lack of use this has amplified the problem:
Depending on the state of the traction battery it is pretty obvious a top up charge of the traction battery to 80% or 100% or whatever may not be long enough to charge the 12v battery.
an hour or two will give it a boost but that is not good enough if the battery still needs another few hours to get to 100%

I have couple of charging options.
I have a Solar panel on the garage connected to a 12V Mppt controller and I have a Ctek MXS 5.0 that I use for maintaining various spare batteries.
The Soul will be added to that cycle, probably weekly.

I am also going to investigate fitting a 12v socket alongside the mains charging connectors so I can easily connect it.

HTH.

140753
 
#73 ·
Proper regular daily use isn't really a problem, although short journeys may not be sufficient to fully charge the battery the daily boost is enough to keep it alive i.e above the critical voltage where everything goes berserk.

We hardly ever use the accessory mode, I have never seen the point because you quickly get a warning if using it for any length of time so when I am in the car parked or otherwise it is fully on and ready to go hence the 12v battery is also charging.

The problem occurs due to extended periods of zero use, the battery is progressively still being drained by all the electronics which although most have a deep sleep mode still draw some power.
 
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