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I replaced the battery on my car on Sunday. I bought a Bosch S4002 battery (12V, 52Ah, 470A) on offer from Costco for £55 incl. VAT and fitted it myself.

You need a 10mm spanner for the two battery terminals and a 12mm spanner for the bolt that holds the clamp that keeps the battery in place. I was pleasantly surprised when the whole black plastic cover came off with the +ve battery clamp as I did think I would need a 13mm spanner to get that off. It reset the recuperation values on the drive modes and reset my range calculations but other than that it went just fine.

I also fitted the BM2 battery monitor and I did have to use a pair of pliers to squish the terminals together so it fitted under the clamp that holds the -ve terminal bolt down. Initially I put it on the big gap in between the bolt sections but then the battery terminal wouldn’t clamp up tight. Other than that (and the fact that I locked the new battery in the boot when I disconnected the old one) it was a doddle.
 

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Storage capacity for modern BEV 12v battery needs to be surprisingly high because ordinary lead acid doesnt like cyclic service at significant depth of discharge and because battery is drained by connected services, keyless entry, accidental lights on incidents.
Interestingly the FIAMM guff on their site refers to the battery as being High Cyclic so maybe it is simply that the demands of the ancillary equipment can be met by a smaller battery which is designed to deal with regular cycles in the way older technology batteries did not but as Nicam says I read it that the battery has only 12 ah capacity at 170volts which surprises me. These type of batteries seem to have started life as start stop batteries in the early Mercedes start stop systems but which were superseded in later cars by some sort of condenser system which in the 2015 w205 C class had a short life (many were replaced around 2yrs old mine incl) but had been perfected by the time I had a w213 e class which at 3yrs old when I changed it had not had a replacement. Wonder if Mercedes’ are experimenting with a diff approach to others, but given that these batteries are responsible for all the emergency systems should the HVBattery be disconnected in an accident it is surprising they are so apparently small.
Nothing like the same technology at all but 6 AA batteries have lasted in the chicken co-op door for 5mths and were still at 80% working perfectly much to my surprise i expected them to need replacing far more frequently.
 

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2019 Hyundai Kona Premium SE 64 kWh
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Discussion Starter · #23 ·
Find a decent Hyundai dealer, get it replaced under guarantee- that smells like a lot of BS to me!
For reference, my Tesla 12V needed replacing, it is unique to Tesla, would have charged £180 for a ranger to visit me and do it at my place of choosing. Our Hyundai dealer is usually great with our Ioniq too.
I did check the warranty and the 12 volt battery from Hyundai is only covered for 2 years. In my case the battery was already 3 years old, so not covered. This is why I didn't want the same battery, as I'm planning on keeping the car long term.

I have found a local independent garage who is happy to replace the 12 volt battery for £115, even after I told him it was a fully electric car. Warranty is still slightly better at 3 years, instead of 2 years from Hyundai.
 

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Interestingly the FIAMM guff on their site refers to the battery as being High Cyclic so maybe it is simply that the demands of the ancillary equipment can be met by a smaller battery which is designed to deal with regular cycles in the way older technology batteries did not but as Nicam says I read it that the battery has only 12 ah capacity at 170volts which surprises me. These type of batteries seem to have started life as start stop batteries in the early Mercedes start stop systems but which were superseded in later cars by some sort of condenser system which in the 2015 w205 C class had a short life (many were replaced around 2yrs old mine incl) but had been perfected by the time I had a w213 e class which at 3yrs old when I changed it had not had a replacement. Wonder if Mercedes’ are experimenting with a diff approach to others, but given that these batteries are responsible for all the emergency systems should the HVBattery be disconnected in an accident it is surprising they are so apparently small.
Nothing like the same technology at all but 6 AA batteries have lasted in the chicken co-op door for 5mths and were still at 80% working perfectly much to my surprise i expected them to need replacing far more frequently.
You are still stating 170 Volts which would seem to be a mistake!!!!!!
 

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Interestingly the FIAMM guff on their site refers to the battery as being High Cyclic so maybe it is simply that the demands of the ancillary equipment can be met by a smaller battery which is designed to deal with regular cycles in the way older technology batteries did not but as Nicam says I read it that the battery has only 12 ah capacity at 170volts which surprises me. These type of batteries seem to have started life as start stop batteries in the early Mercedes start stop systems but which were superseded in later cars by some sort of condenser system which in the 2015 w205 C class had a short life (many were replaced around 2yrs old mine incl) but had been perfected by the time I had a w213 e class which at 3yrs old when I changed it had not had a replacement. Wonder if Mercedes’ are experimenting with a diff approach to others, but given that these batteries are responsible for all the emergency systems should the HVBattery be disconnected in an accident it is surprising they are so apparently small.
Nothing like the same technology at all but 6 AA batteries have lasted in the chicken co-op door for 5mths and were still at 80% working perfectly much to my surprise i expected them to need replacing far more frequently.
Not 170 Volts, that would fry the conventional 12V stuff like the radio, lights, fan motor etc! As an EV does not need to crank a lump of an engine it does not need a high Cold Cranking rating which the standard battery fitted has. It does however need to maintain 12V to power the relays to start the car. So that FIAMM battery you mention sounds suitable and indeed Tesla are moving to a Lithium 12V battery with similar characteristics. The advantage being that the voltage can drop without killing the battery. You might not start the car but at least the battery is undamaged. Drop the voltage too low on a conventional lead acid battery and you cause it irreparable damage, which is what has been happening to cars on this forum.

A deep cycle battery would be more suitable than the standard issue battery fitted and a Lithium even better but as the car is not a Mercedes the cost accountants have had their say. After all, when the battery fails after 2 years the warranty has expired. Your problem not theirs and then they have the cheek to try and sell you a replacement at an inflated price.
My £80 replacement is performing just fine,
 

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After all, when the battery fails after 2 years the warranty has expired. Your problem not theirs and then they have the cheek to try and sell you a replacement at an inflated price.
My £80 replacement is performing just fine,
Well, they can't replace oil, oil filter, timing belt, cam belt etc, but they can replace a 12 volt battery out of warranty and charge you a pretty penny for it. :)
 

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Mercedes EQC 400 4matic
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You are still stating 170 Volts which would seem to be a mistake!!!!!!
My bad yes you are right according to other half it would be 170A. Am still shocked at it only being 12ah such that I tried to check out the batterie on board my car but it is buried too deep to see clearly but it looks similar to the picture on the Mercedes’ site. Interestingly Norauto ( equivilant to a Halfords type of place here) sell a 70ah Exide as a replacement also AGM as do the RAC but thses do not seem actually to be the same spec replacement but for once the direct Mercedes’ replacement is the cheapest option a first ever I think🤔😉
 

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2019 Hyundai Kona Premium SE 64 kWh
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Discussion Starter · #30 ·
Got my 12 volt battery replaced last Saturday and I have used the car for 55 mile commute. Didn't lose any settings and everything works as expected. The independent garage also confirmed this was their first Kona EV 12 volt battery replacement and they didn't do anything special.

So I can confirm the reasons given below by the other places I tried are at best, misinformed.

  1. The 12 volt battery is encoded to the car and replacing it would not work without Hyundai special tooling etc.
  2. Replacing the 12 volt battery would require isolating / disconnecting the main traction battery.
 

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Kona EV, 64kW Premium Nav 2019
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Considering replacing ours: has failed 3 times now (boot left open all day whilst gardening at relatives...boot accidentally left open on other two occasions....might have to check on the boot adjustment!)

We have a USB booster which worked a treat each time to restart.

I'm currently (pun intended 🤪) trying the Tanya Batteries recommendation to revitalise it.
Now on step 4 (have used this with older kids Fiesta in the distant past):

1. Connect flat battery to any other battery with jump leads
2. Leave for 10 mins and then connect charger to flat battery at same time:
Motor vehicle Hood Automotive tire Bumper Automotive exterior


3. Turn on charger and charge like this for 1 hour.
4. Then take off jump leads and charge battery normally with charger for minimum of 12 hours.
This will then bring the battery up to 12.73v (100% Capacity)

If that fails, then we will get a new battery.
I can see an Exide Premium 012 Car Battery (53Ah) - comes with a 5 Year Guarantee - for under £90. Could add under £20 to get it fitted too (how lazy do I feel?!)

Any other recommendations?
 

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Considering replacing ours: has failed 3 times now (boot left open all day whilst gardening at relatives...boot accidentally left open on other two occasions....might have to check on the boot adjustment!)

We have a USB booster which worked a treat each time to restart.

I'm currently (pun intended 🤪) trying the Tanya Batteries recommendation to revitalise it.
Now on step 4 (have used this with older kids Fiesta in the distant past):
A
1. Connect flat battery to any other battery with jump leads
2. Leave for 10 mins and then connect charger to flat battery at same time:
View attachment 164766

3. Turn on charger and charge like this for 1 hour.
4. Then take off jump leads and charge battery normally with charger for minimum of 12 hours.
This will then bring the battery up to 12.73v (100% Capacity)

If that fails, then we will get a new battery.
I can see an Exide Premium 012 Car Battery (53Ah) - comes with a 5 Year Guarantee - for under £90. Could add under £20 to get it fitted too (how lazy do I feel?!)

Any other recommendations?
Why does leaving the boot open drain the 12v battery?
 

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Kona EV, 64kW Premium Nav 2019
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The car is "awake" with any of the doors open and the 12v is taking the strain without the help of the traction battery.
^
Wot he said!
(well, that was my understanding...)

If anyone has recommendations on batteries beyond my comments above, I'd be interested.....not 100% certain our original 3-yr old one will cut it much longer, but still hoping!
 

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Thanks not sure that seems a good design ie a door open the battery is draining but maybe it is a standard one. With my car I have to engage the system with the start button and there are at least 2 stages, the first you open the car the screens wake up, you press the start button the warning lights all display and there are a few clunks and whirrs as the car does some more waking up, then press again and the warning lights extinguish and the car is ready to go, exactly the same system as the ICE Mercedes.
What systems does the 12v battery need to run in an EV it would not need to run in an ICE? The Mercedes’ battery is small too, the battery size they use for the stop start systems in earlier models, indicating it does not do a lot which it does not as it does not need to crank a heavy combustion engine.
I will say though that the alarm and monitoring system on the e class ICE I had was using up power and the battery needed a top up during our confinement here when the max distance I could travel was a 4k round trip so the car was started up and little recharge and then standing for ages. Mercedes said if you intended to leave the car over 6 weeks the 12v would need to be wired up to a trickle charger. The manual states with the EQC that the 12v should only be charged by a qualified workshop despite it having all the standard connections as on the e class (Mercedes’ provide a positive and negative connection point).
 

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Kona EV, 64kW Premium Nav 2019
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Thanks not sure that seems a good design ie a door open the battery is draining but maybe it is a standard one.
Yup....I do have memories of doing a car boot with my daughter many years ago (regular ICE motor) - again, didn't think to close doors, and the farmer had to jump start us and a few others who had drained their batteries somewhat 🤷‍♂️

In better news, the Kona appears to be fine now....maybe I need to investigate battery monitors for the 12V one....
 

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Has anyone replaced the 12V lead acid battery with a lithium ion one? Of all the solutions to the problem (battery monitoring, regular extended charging to desulphate the battery) this would seem the best.

TIA

Bill
 

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Has anyone replaced the 12V lead acid battery with a lithium ion one? Of all the solutions to the problem (battery monitoring, regular extended charging to desulphate the battery) this would seem the best.
These certainly exist, but you'll need one with a BMS in that emulates a 12V, as the charging voltages&rates differ a lot between pure Li-ions & Lead-acids. USA prices are around $400, that sort of region, so not a cheap way to go!
Far cheaper to carry a Li-ion booster pack & accept the faff of cabling it up on the very few occasions it might be needed (I've had 2 vampire attacks on my Ioniq in 2 years).
 

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Kona EV, 64kW Premium Nav 2019
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Yup....I do have memories of doing a car boot with my daughter many years ago (regular ICE motor) - again, didn't think to close doors, and the farmer had to jump start us and a few others who had drained their batteries somewhat 🤷‍♂️

In better news, the Kona appears to be fine now....maybe I need to investigate battery monitors for the 12V one....
Well, I spoke too soon there. Kona continued to play up, charger was unable to revitalise the battery, so I ordered a new Yuasa one at the weekend - 54Ah HSB012 with 5 year guarantee (£69 delivered).
Arrived today, easy peasy installed within 5 minutes 👍
Hopefully the issues are behind us. Anyone want a flat battery? 🤣
 

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The car is "awake" with any of the doors open and the 12v is taking the strain without the help of the traction battery.
And the car's software is too stupidly designed to implement a simple timeout, or enable topping up from the HV battery when the car isn't in "on" mode.

There is a secondary issue that the car takes a substantial current (many amps) for several minutes before going fully to sleep. This is an issue as just a few door-opening events ( e.g. loading/unloading) spread out over the period of tens of minutes means the car is pulling a very large proportion of the 12V battery's capacity, and a slightly weak/aging battery will just keel over.
The usual reason for systems doing this is to make wake-up faster, however I couldn't find anything that didn't wake up almost immediately on connection of the 12V battery, so the car leaving things on like this seems to be completely pointless and just lazy design.
 
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