[libranof1987]

Originally Posted by ssh1979

OK. Then what're the other options for @smsraja's situation?

I am myself in a slightly similar situation; I don't use my vehicle during the week and at times only on saturday and sunday evening.

But, I make it a point to idle the car for a short while and take a 0.5 trip around the parking lot of my apartment complex every 3rd day.

Not only helps the battery but also keeps all the mechanicals in running condition.

Else, especially in the rainy season and if the parking is uncovered; there'll be water accumulation on the brake liners/discs.

Moral of the story : for whatever short duration, the car should *ideally* be run every now and then (since the 8-9 day no-use period is a regular pattern).

And also how is the idling counter-productive to the vehicle? I can accept that it is bad on the environment and our pockets. Otherwise?

Idling is not counter-productive; idling for 2mins is. You need to let the car run for some time (can't quantify it but know this for a fact) so the battery makes up for the charge used up for cranking the engine and also recharges to full capacity. 2mins idling ain't enough.

[Gansan]

^^Idling can only help the oil to circulate, not charge the battery. The engine will have to cross a particular RPM for the alternator to charge the battery, not otherwise. Idling for 5 minutes/taking a short trip around the block will not help at all. It can actually be counter productive and damage your catalytic converter.

The only way is to use the car at least once a week for about 30 - 40 KM, giving good throttle when the road is traffic free.

[anekho]

Guys, are petrol or diesel cars better suited to being left alone for long periods of time? By long periods I mean ~ 6 months, with NO usage/starting at all.

Cheers!

[dhanushs]

Originally Posted by libranof1987

Idling the car for 2-5 mins would be counter-productive rather than helpful. I don't think idling for 5mins would help the battery recharge or even regain the charge lost in cranking up the engine.

Originally Posted by ssh1979

OK. Then what're the other options for @smsraja's situation?

And also how is the idling counter-productive to the vehicle? I can accept that it is bad on the environment and our pockets. Otherwise?

+1 to librans suggestion. Whats the point in starting the car every now and then, and idling just 5 mins?. 1st 5 mins is where max wear and tear occur (cold engine) and also, the charge used for cranking is not restored with just 5 mins of idle.

In smsraja's situation, either he use the car for atleast an hour a week, or a better solution is to take the battery and charge it full for 50 bucks (or free?), every fortnightly.

Originally Posted by anekho

Guys, are petrol or diesel cars better suited to being left alone for long periods of time? By long periods I mean ~ 6 months, with NO usage/starting at all.

A decade before, it was no doubt - Petrols. but today, apart from the slightly more power required for cranking, pretty much everything is tally. Perhaps experts can advise more technically.

[smrsraja]

Gi Huys,

Finally changed the battery and now i dont have starting problem any more. When i checked with a near by battery shop, the alternator was working and only the battery was not holding the charge. A 2.5 years old Tata green battery. Now switched to Exide champion.

[Simhi]

A very useful thread. I had to park my i10 for 2 months. Followed the tips on this thread and did the following
1. Bought a car cover
2. Disconnected the battery (first negative terminal and then positive terminal)

After 2 months, connected the battery again in reverse order (first positive and then negative ) and the car started in first go without any hitch.

I had one doubt initially whether the front driver door would open without battery. Yes, it does.

Also, one tip from my side. If you need to clean/wash the car cover, better put it back on the car and do the cleaning. it is much easier this way. If you remove the cover and try to clean/wash, it's a pain.

[thoma]

I do not think using a cover will do your car good if you are residing in a high humid area. This is because, closed areas (no ventilation) are the biggest friend of moisture and thus rust, unless the area is fully vacuumed.

Chevrolet was more thoughtful on leaving the car unused rather than using it heavily (pun intended). See, they have provided instructions in the Beat's owner manual for storage over a long period of time. Though, I couldn't understand how the engine compartment can be waxed and how to drain the washer fluid reservoir.

[libranof1987]

Originally Posted by thoma

I do not think using a cover will do your car good if you are residing in a high humid area. This is because, closed areas (no ventilation) are the biggest friend of moisture and thus rust, unless the area is fully vacuumed.

Chevrolet was more thoughtful on leaving the car unused rather than using it heavily (pun intended). See, they have provided instructions in the Beat's owner manual for storage over a long period of time. Though, I couldn't understand how the engine compartment can be waxed and how to drain the washer fluid reservoir.

Attachment 843501
Attachment 843502

A good guide to what one should do; some things (anti-freeze etc.) are typical for western countries though.

Wax for the engine compartment basically means the wax treatment that you get done for the under belly and engine bay. To drain washer fluid, just keep using it till it is empty and don't replenish.

[heysac]

I wanted to have a discussion around the maintenance of batteries for cars that are not driven regularly. I have put up a few questions below and would appreciate if everyone can contribute their learnings/knowledge to make this thread useful!

1) Does it make sense to disconnect the negative terminal (red) if the car is not driven regularly for over 15 days to prevent discharging?

2) Does a certain type of battery (for ex: sealed) perform better in this use case?

3) Do you need to recharge the battery every x # of days ot make sure it doesn't die?

Thanks!

[ilangop]

Originally Posted by heysac

1) Does it make sense to disconnect the negative terminal (red) if the car is not driven regularly for over 15 days to prevent discharging?

2) Does a certain type of battery (for ex: sealed) perform better in this use case?

3) Do you need to recharge the battery every x # of days ot make sure it doesn't die?

1) Makes sense. For ECU driven cars, there is some sleep mode current associated with it for its memory. As well there might be the sound system that needs a direct line to power the clock. Though they consume very small currents, yet enough charge to discharge over longer period.
Lets go with some mathematics. Assume the clock + ECU will need 0.03A (pretty optimistic assumption, can be little more also) of current. For 15 days, the charge you lose will be 0.03*15*24(hours) = 10.8 Ampere-hour. Let us say, yours is a M-800 with a 35Ah battery, you are sure to lose 1/3 of its max charge in a span of 15 days. So this adds sense in disconnecting a battery for long term. Storage of battery at very depleted levels of charge tend to reduce the battery life as well.
2) Probably a sealed battery doesnt let the water vapours escape with temperature. Can help to some extent in retaining the electrolyte levels
3) To healthily start an engine a 12V battery should have at least 12V at the terminals. Buy a cheap 100 Rs multimeter to measure the voltage, and decide if it needs to be charged.
Hope the info helps.

[vina]

Originally Posted by ilangop

1) Makes sense. For ECU driven cars, there is some sleep mode current associated with it for its memory. As well there might be the sound system that needs a direct line to power the clock. Though they consume very small currents, yet enough charge to discharge over longer period.
Lets go with some mathematics. Assume the clock + ECU will need 0.03A

for a well designed ECU board - an automotive boards are almost all well designed as far as electronics design goes (consumer electronics are NOT) - 0.03A, or 30mA of power consumption for the ECU board is way too much.

I'm not sure it burns that much in normal operation, let alone standby.

Also which clock are we talking about here? system clock consume micro-amps (that's a thousand times less than you figures) and the car's display clock takes most o the current for display, not for clock. Display on my Figo goes off as soon as I take the key out of ignition (I would expect the same for other cars).

IMHO battery on its own will lose more energy (all batteries "leak" in standby on their own) than the vehicle's control system electronics put together. If you leave a light on - that's another matter.

Originally Posted by ilangop

3) To healthily start an engine a 12V battery should have at least 12V at the terminals. Buy a cheap 100 Rs multimeter to measure the voltage, and decide if it needs to be charged.
Hope the info helps.

I'm not sure this is true. Again AFAIK a fully charged battery has roughly 12V as terminal voltage when measured with a voltmeter. However the moment you start drawing current the terminal voltage falls anyway - The drop in voltage divided by the o/p current is called internal resistance of the battery.

Also, all batteries lose terminal voltage as they discharge, and lead-acid batteries have a gradual slope (unlike Li-ion, which fall off a cliff eventually and hence need monitoring circuits).

while charging an "almost fully charged" battery will show more than 14V (15V?) as terminal voltage - but that is to be expected isn't it? This is the reason engine must be running at a certain rpm before alternators can generate a voltage high enough to start charging the battery.

[ilangop]

Originally Posted by vina

for a well designed ECU board - an automotive boards are almost all well designed as far as electronics design goes (consumer electronics are NOT) - 0.03A, or 30mA of power consumption for the ECU board is way too much.

IMHO battery on its own will lose more energy (all batteries "leak" in standby on their own) than the vehicle's control system electronics put together. If you leave a light on - that's another matter.

I'm not sure this is true. Again AFAIK a fully charged battery has roughly 12V as terminal voltage when measured with a voltmeter. However the moment you start drawing current the terminal voltage falls anyway - The drop in voltage divided by the o/p current is called internal resistance of the battery.

while charging an "almost fully charged" battery will show more than 14V (15V?) as terminal voltage - but that is to be expected isn't it? This is the reason engine must be running at a certain rpm before alternators can generate a voltage high enough to start charging the battery.

Originally Posted by ilangop

Lets go with some mathematics. Assume the clock + ECU will need 0.03A (pretty optimistic assumption, can be little more also) of current.
3) To healthily start an engine a 12V battery should have at least 12V at the terminals. Buy a cheap 100 Rs multimeter to measure the voltage, and decide if it needs to be charged.
Hope the info helps.

@ Vina, Hope you read that it is an assumption only. And you might be right, it can be lesser as well.

The simple ratio of voltage by instantaneous current drawn, gives the DC resitance of the battery and not the internal resistance (IR). The IR can be measured using impedance measuring instruments or through a cycle test as per standards. The DC resistance is only indicative to size the battery & judge the State of charge (SOC). Internal resistance is a function of state of charge & health and the temperature of the battery.
Hope you might be aware that a normal SLI (Starting, LIghting, & Ignition) battery shall be shuttled between 100% to 75 or 70% SOC only for starting application and without causing any permanent damage to the battery. Thats why I had mentioned 12V. The open circuit voltage (terminal voltage after a long rest period) usually settles at 12.5 V or so (depending on the make) after a long rest after a full charge. By the time OCV dips to 12.0 V, the on load voltage while cranking can even dip till 7V. Which is something not recommendable.

[vina]

Originally Posted by ilangop

@ Vina, Hope you read that it is an assumption only. And you might be right, it can be lesser as well.

The simple ratio of voltage by instantaneous current drawn, gives the DC resitance of the battery and not the internal resistance (IR). The IR can be measured using impedance measuring instruments or through a cycle test as per standards. The DC resistance is only indicative to size the battery & judge the State of charge (SOC). Internal resistance is a function of state of charge & health and the temperature of the battery.
Hope you might be aware that a normal SLI (Starting, LIghting, & Ignition) battery shall be shuttled between 100% to 75 or 70% SOC only for starting application and without causing any permanent damage to the battery. Thats why I had mentioned 12V. The open circuit voltage (terminal voltage after a long rest period) usually settles at 12.5 V or so (depending on the make) after a long rest after a full charge. By the time OCV dips to 12.0 V, the on load voltage while cranking can even dip till 7V. Which is something not recommendable.

Thanks @ilangop

I didn't think it was an assumption, I thought you were making a statement of fact. Sorry about that.

I saw your PM regarding the other thread (and later saw the post also) - will comment on that shortly.

Your post here has quite a bit of hard to get information on batteries, it is not very often when information this deep is available on teamBHP. I have some questions -

1. I always thought DC resistance (as measured by v2-v1 / I2-I1 where v2 and v1 are terminal voltages while drawing I1 and I2 respectively) gives the DC resistance of the battery reliably. I also though this was the internal resistance of the battery - (total impedance would of course include phase shift and hence some detailed modeling involving capacitors also). Can you tell me the difference between DC resistance and internal resistance (as against impedance) for the battery, or give some internet links? Best way is to tell the difference in their measurement methods (as is true for any physical quantity)
2. The information that the battery will go down to only 70% state of charge (and not below) is very significant. Is it possible that in a normal car (with no faults) the SOC can go down from 100% to 70% in the course of a single start?
3. I didn't know the exact OCV - 12.5V sounds fine. Also 0.5V drop in OCV may of course mean SOC will be far from 100% for a reasonably good battery that is not about to die on you - depends on the discharge curves of course. How much does the battery voltage drop when cranking from a 100% SOC?

Here's something relevant that @Aroy sir wrote one a thread I started today http://www.team-bhp.com/forum/techni...l#post2593722:

Originally Posted by Aroy

1.
For Toyota Landcruiser the motor is 2.5kW "NEW" TOYOTA LANDCRUISER STARTER MOTOR HZJ80 HZJ75 90- | eBay
For Ford Fiesta it is 0.8kW "BRAND NEW" STARTER MOTOR FORD FESTIVA 91-97, 1.3LTR, 3 BOLT, | eBay
So it can be assumed that the motor will vary from 0.8kW (Alto?) to 3kW+ for heavier diesels (check in the Denso Catalog in the links given further). So the current drawn will be between 70A and 250A. (That is why we need that thick cable for the starter, and similarly for the Jump Start Cable)
2.
- Small petrols in normal weather : 1 sec
- Small petrols in cold weather : 5-10 sec
- Diesels in warn weather 2-5 sec
- Diesels in cold weather - 10+ sec
- Maximum experienced - 2 min on a cold day

My take on this - for a 1kW motor, the average current will be (roughly) a 100A for may be 10seconds usually.


As you yourself wrote on the other thread - alternator develops enough voltage to start charging even at idling rpm.


Now most alternators generate over 50A of currents even for small hatches - if even 5A of that is used the battery should be charged up within minutes once the rpm is enough to move the vehicle at decent speeds. Of course if cranking took 2 min. on an old dying battery, then one would expect the charging to take far longer - but that is usually not the case.







I wrote about this because somewhere some members had written that driving around at low rpm will not charge up the battery - that assertion doesn't make sense with the above facts.


Any comments?

[ilangop]

@ Vina - Please check your PM as well.

Originally Posted by vina

I have some questions -
1) I always thought DC resistance (as measured by v2-v1 / I2-I1 where v2 and v1 are terminal voltages while drawing I1 and I2 respectively) gives the DC resistance of the battery reliably. I also though this was the internal resistance of the battery - (total impedance would of course include phase shift and hence some detailed modeling involving capacitors also). Can you tell me the difference between DC resistance and internal resistance (as against impedance) for the battery, or give some internet links? Best way is to tell the difference in their measurement methods (as is true for any physical quantity)

2) The information that the battery will go down to only 70% state of charge (and not below) is very significant. Is it possible that in a normal car (with no faults) the SOC can go down from 100% to 70% in the course of a single start?

3) I didn't know the exact OCV - 12.5V sounds fine. Also 0.5V drop in OCV may of course mean SOC will be far from 100% for a reasonably good battery that is not about to die on you - depends on the discharge curves of course. How much does the battery voltage drop when cranking from a 100% SOC?

4) My take on this - for a 1kW motor, the average current will be (roughly) a 100A for may be 10seconds usually.

5) I wrote about this because somewhere some members had written that driving around at low rpm will not charge up the battery - that assertion doesn't make sense with the above facts.

1) & 2) Not in a single crank of course. I wanted to say that at SOC below 70% even if a battery is able to crank, it may not be a healthy practice considering the damage it might cause to it. Again for assumption, let a battery data sheet recommends 10C as the max discharge current (Without damaging the battery) at a particular SOC. For a 50Ah battery, at 100% charge 10C will be 500 Ampere. At 70 % SOC the charge content is 0.7*50 = 35Ah, and the 10C current now is 350A.

3) Not sure on the exact number for the drop in voltage. But some ECUs have 6V as the minimum cutoff.

4) 10 seconds is way too long. Even owners manual might warn the user on cranking the engine this long. The usual recommendation is to give a pause after 2 or 3 sec of cranking and then restart.

5) The battery warning lamp goes off even at idle, right? Which means that the battery is getting charged. The lamp works on the simple principle that lamp glows when there is no current generated from the alternator.

[Sutripta]

Originally Posted by ilangop

1) & 2) Not in a single crank of course. I wanted to say that at SOC below 70% even if a battery is able to crank, it may not be a healthy practice considering the damage it might cause to it. Again for assumption, let a battery data sheet recommends 10C as the max discharge current (Without damaging the battery) at a particular SOC. For a 50Ah battery, at 100% charge 10C will be 500 Ampere. At 70 % SOC the charge content is 0.7*50 = 35Ah, and the 10C current now is 350A.

Hi,
What could be the reason for the pro rata linkage between SoC and starting current available?

Regards
Sutripta