AFN Engine: Lima 18V?

hello,
I measured the voltage of my battery today, and it was 15V. When the engine is running, it's 18V. Isn't that too high? Could the regulator be faulty?

Best regards,

hello,
I measured the voltage of my battery today, and it was 15V. When the engine is running, it's 18V. Isn't that too high? Could the regulator be faulty?

best regards

Hello.
What a question!
Either the LM (likely referring to a lithium-ion module) is 'scrap' or the battery has an extremely 'high resistance'; in either case, the motor wouldn't start!
Make sure to check the LM battery connection (both positive and negative!).
Try to avoid driving as much as possible!!! Or, if you must drive, make sure to turn on the rear window defroster as a baseline load for the energy management system!
Best regards,
Günther.

I already had that problem. I tried to start it, but nothing happened except for the warning lights. I fiddled with the light switch, and then it started. How can I track down the cause of the problem, or what should I measure?

Best regards,

I already had that problem. I tried to start it, but nothing worked except for the warning lights. I fiddled with the light switch, and then it started. How can I find the cause of the problem, or what should I measure?

best regards

Hello,
If it starts, drive to a Bosch service center with the rear window defroster turned on.
Due to a lack of experience, it could otherwise become 'expensive' for you.
Best regards,
Günther.

He who measures, measures manure!

Seriously: If you're already measuring 15V with the engine off, I highly doubt the accuracy of the meter's reading. Do you have a second meter to perform a comparison measurement, or the possibility of using the existing (faulty?) meter to measure a known low voltage?

Regards,
Guste.

He who measures, measures rubbish!

Seriously: If you're already measuring 15V with the engine off, I highly doubt the accuracy of the meter's reading. Do you have a second meter to perform a comparison measurement, or the possibility of using the existing (faulty?) meter to measure a known low voltage?

Regards,
Guste.

Hello,
Basically, you're right, but a 'defective' lithium-ion battery can still 'charge' to 15 volts or more!
Best regards,
Günther.

Hi,

@ Günther:

In my opinion, it is not possible to charge a car battery significantly above 14V because the electrochemical cell does not have a higher open-circuit voltage.
However, if the battery continues to charge even after the charging current has decreased or the battery voltage has reached a certain limit (unfortunately, I don't know exactly how the charging regulator determines whether the battery is "full" or not), then electrolysis of the water inside the battery occurs.
Then it reaches H2, and potentially the battery could explode if the pressure cannot be released.


Best regards, Georg.

Unfortunately, I don't know exactly how the charge controller determines whether the battery is 'full' or not.

Hi! Nothing is being decided there. The LIMA is nothing more than a constant voltage source, similar to a stabilized power supply.

It is calibrated to the charging voltage of common lead-acid batteries, which Varta, for example, specifies as a maximum of 14.4V. Usually, it is slightly lower than that (to prevent excessive gassing when the battery is fully charged).

A good lead-acid battery charger typically limits the maximum charging current (by transitioning smoothly from a constant voltage to a constant current source). An alternator, however, doesn't 'know' whether a rear window heater, a discharged battery, or other consumers are connected. Therefore, a completely discharged lead-acid battery connected to an alternator can receive a significant charging current (theoretically up to 35A). Starter batteries, in particular, should not be discharged by more than 1/3 in any operating condition, and they may not handle such high currents well.

Furthermore, an ideal charger switches to trickle charging once the charging cutoff voltage is reached, so that the battery does not unnecessarily gas. At that point, the voltage drops to just above the resting voltage (12.5~13V). The alternator does not do this either, but car batteries seem to tolerate the constant charging cutoff voltage quite well.

So, a high-end Lima (alternator) would have a separate on-board network and a microcontroller-controlled battery charging output. However, that probably isn't cost-effective, as it also involves more wiring.

Okay, and one more thing: In today's electric vehicles, the motor controller should already provide sufficient base load to prevent the voltage from spiking to astronomical levels in case of a fault or when the battery is depleted. A fully charged battery also draws less than 1A of charging current, so the rear window heater as a 'base load' is excessive.

Regards,
Holger.

@quert1: Is it possible that the measuring device is calibrated in 'Vinch' by chance? (American model?) Or does your battery have 8 cells? (Turkmenistan 16V on-board network, only for export).

Hi Qwert, it wasn't meant to be rude . Try leaving the headlights on for a few minutes with the engine running and then measure the voltage. Lead-acid batteries quickly drop to 12~13V without a charging current (and even more so with a load) and then stabilize at that level. A discharge voltage of 15V is not possible, not even with a faulty battery! (In that case, the battery wouldn't be faulty, but rather 'hyperactive').

Regards,
Holger.

SeatArosa1.7SDI wrote:

A discharge voltage of 15V doesn't exist, not even with a broken battery! (in that case, it wouldn't be broken, but rather "hyperactive")

Sure.
"And a rounded-up 3-volt difference between the voltage with the engine running and the voltage with the engine off (see above: 18V vs. 15V) is still acceptable after a cold start in arctic conditions, because temperature-compensated alternator regulators can sometimes actually deliver a real 15V in such situations."

So, this whole thing should be measured with a more precise measuring device, and the result should be posted with one decimal place (!). Hopefully, everything will be okay...

Sehe ich genauso, entweder lag das Messgerät mal einem Yps als Gimmick bei, oder der Batterie ist über Nacht eine 7. ZShe has grown up.

We've already had lead-acid batteries explode at the company, and that's even happened at voltages lower than 15V. They were about the size of a soccer ball...

Hi,

Car batteries are vented, which is why they don't explode (except during a gas test with a lighter). However, they can still be damaged by overcharging.
Multimeters that don't belong to the high-end class often display inaccurate readings when the battery is low. So, it might be worth trying a new battery.
3. Regarding the charging process: A better charging method would be IU charging, which involves constant current followed by constant voltage. The main problem in a car is that it takes too long to fully charge the battery. Maintaining a constant voltage for an extended period isn't too detrimental to a lead-acid battery, as long as the voltage isn't too high, and measures are taken to compensate for water loss. However, constant current charging is not suitable for a system where the battery acts as a buffer, as the voltage could become very high, and there's no way to determine where the current is flowing.

Under extreme abuse conditions (24V 10A on an NC cell), the battery voltage can sometimes reach double its nominal voltage, but only for a few seconds. After that, it will either return to its normal voltage or have no voltage at all.

Greetings.
dieter

@Dieter:

1.)

"Maintenance-free long-life batteries, as defined by EN 50272, are no longer considered 'open' in the traditional sense."

According to information from a WOB employee, VW uses two types of maintenance-free batteries with reduced water consumption:

a) The enclosed type.
"A sealed battery, by definition, is a battery that has caps, even if those caps are hidden, possibly under a sticker. The LL batteries in our two vehicles from 2002 and 2003 are designed this way. The caps are hidden under a black sticker; at first glance, it may appear that they don't have caps. This type of battery is typically used as a starter battery in the engine compartment."

b) The sealed type.
These batteries no longer have any internal seals, only a venting mechanism. They are often used as a secondary battery for installation in the trunk, as seen in models like the Phaeton or Touareg.

The sealed type can explode just like the closed type, due to a faulty battery or severe overcharging. Both designs have venting openings. In our case of explosion, it was a sealed battery with a manufacturing defect.


2.) I don't understand this at all. What does the accuracy of a voltage measurement have to do with the battery's state of charge?
Common multimeters have an input resistance of several megaohms, so what difference would the charge state make? Practically no current flows during the measurement.


Football battery.

Roger wrote:

2.) I don't understand this at all. What does the accuracy of a voltage measurement have to do with the state of charge of the battery?

That refers to the 9V battery in the multimeter. If that battery fails, I can quickly get 300V at home from the wall outlet. The 9V is probably used as a reference voltage, and if it drops, the displayed voltage increases.

Hi Roger,

Let's not argue about the different types of batteries; I'm assuming we're talking about standard lead-acid batteries, which are typically open. However, maintenance-free batteries at least have pressure relief valves. I recently had to forcefully remove some swollen gel batteries from a UPS, but you wouldn't normally find something like that in a car, would you?

Regarding the battery: that was a misunderstanding. I meant the battery INSIDE the measuring device.

Greetings.
dieter


Oops: someone was faster .

I can confirm that.
I have several multimeters here. The most expensive one, my METEX, shows too high a voltage reading when its own battery is getting weak.