alternator charging voltage, what should it be?

SFHLibertyCRD · **Posted:** Tue Dec 23, 2014 5:57 pm

When driving, the CRD usually reads about 14.2-14.4 volts (without too many accessories on, radio and maybe iphone charging). I'm assuming alternator is working properly and this is good enough to keep my battery charged up? My VW TDI is usually around 14.4-14.5. I just purchased a new Odyssey battery and want to make sure I can get the full life out of that expensive battery. The CRD sees lots of short trips, so I'll also throw it on the trickle charger occasionally to keep it topped up.

jws84_02 · **Posted:** Tue Dec 23, 2014 6:20 pm

Yep your right on. Mine is always 14.2-14.3

thermorex · **Posted:** Tue Dec 23, 2014 8:05 pm

Yes, that's what mine shows, it will try to keep 14.2-14.4 until there are too many consumers. There are battery maintainers that you can permanently install in the jeep and plug it in. About 20-30 minute of engine running should charge the battery back up without issues.

SFHLibertyCRD · **Posted:** Tue Dec 23, 2014 9:16 pm

Thanks guys.

SFHLibertyCRD · **Posted:** Tue Jan 06, 2015 3:40 pm

So, a follow-up: The old battery (a cheap one from previous owner) lasted 4 years and died trying to start the jeep yesterday; I consider that pretty good for the low quality of the battery after a few discharge/charge cycles. So I got the new Odyssey battery in last night. This morning, on the commute to work, my voltage was reading 14.1-14.2, rarely more than that (I am not sure if what I reported last time was accurate, but I thought it was higher with the old battery, which I don't believe should make a difference?). When I put lots of load on it with radio, wipers, high beams, etc. all on at once. It drops to about 13.8-13.9. This was driving around town with lots of stop and go, so almost no highway.

What I've read basically says as long as it stays above 13 with lots of draw on it, you are good. Is that correct? I want to make sure this new battery stays in good health since it was $$$. Are my voltage readings within spec?

Also, I only have a 6 amp charger, this model: http://www.batterychargers.com/ProductD ... 4026804ACP. However, reading on the Odyssey site, they seem to recommend no less than a 25amp charger for my size battery. Is there harm in using a 6amp charger, or will it just be slower to charge a discharged battery?

gmctd · **Posted:** Tue Jan 06, 2015 4:02 pm

Overnite in extreme cod, you may need a trickle-charge - the 6amp will trickle-charge your battery

The 25amp will fully charge your battery, not necessary for trickle-charge

tjkj2002 · **Posted:** Tue Jan 06, 2015 6:19 pm

SFHLibertyCRD wrote:

So, a follow-up: The old battery (a cheap one from previous owner) lasted 4 years and died trying to start the jeep yesterday; I consider that pretty good for the low quality of the battery after a few discharge/charge cycles. So I got the new Odyssey battery in last night. This morning, on the commute to work, my voltage was reading 14.1-14.2, rarely more than that (I am not sure if what I reported last time was accurate, but I thought it was higher with the old battery, which I don't believe should make a difference?). When I put lots of load on it with radio, wipers, high beams, etc. all on at once. It drops to about 13.8-13.9. This was driving around town with lots of stop and go, so almost no highway.

What I've read basically says as long as it stays above 13 with lots of draw on it, you are good. Is that correct? I want to make sure this new battery stays in good health since it was $$$. Are my voltage readings within spec?

Also, I only have a 6 amp charger, this model: http://www.batterychargers.com/ProductD ... 4026804ACP. However, reading on the Odyssey site, they seem to recommend no less than a 25amp charger for my size battery. Is there harm in using a 6amp charger, or will it just be slower to charge a discharged battery?

Your alternator(or any alternator) doesn't even charge the battery at 25amps.

On AGM batteries that high amp charge only will get it to about 90%-95% charged and a lower amp setting is needed to fully charge.

dkenny · **Posted:** Tue Jan 06, 2015 6:45 pm

normal would around 14.0. or less
at 14.2-14.5 the water will boil out of the battery..
13.8v would be ideal..
13.3 - 13.6 even better if the battery was fully changed..say like drive for 20hrs non stop..

-dkenny

SFHLibertyCRD · **Posted:** Tue Jan 06, 2015 6:46 pm

tjkj2002 wrote:

SFHLibertyCRD wrote:

So, a follow-up: The old battery (a cheap one from previous owner) lasted 4 years and died trying to start the jeep yesterday; I consider that pretty good for the low quality of the battery after a few discharge/charge cycles. So I got the new Odyssey battery in last night. This morning, on the commute to work, my voltage was reading 14.1-14.2, rarely more than that (I am not sure if what I reported last time was accurate, but I thought it was higher with the old battery, which I don't believe should make a difference?). When I put lots of load on it with radio, wipers, high beams, etc. all on at once. It drops to about 13.8-13.9. This was driving around town with lots of stop and go, so almost no highway.

What I've read basically says as long as it stays above 13 with lots of draw on it, you are good. Is that correct? I want to make sure this new battery stays in good health since it was $$$. Are my voltage readings within spec?

Also, I only have a 6 amp charger, this model: http://www.batterychargers.com/ProductD ... 4026804ACP. However, reading on the Odyssey site, they seem to recommend no less than a 25amp charger for my size battery. Is there harm in using a 6amp charger, or will it just be slower to charge a discharged battery?

Your alternator(or any alternator) doesn't even charge the battery at 25amps.

On AGM batteries that high amp charge only will get it to about 90%-95% charged and a lower amp setting is needed to fully charge.

I think you are right about that, but in addition Odyssey has a special algorithm I think specifically for charging a discharged battery. They don't seem to support charging outside of these specs. They have a list of "approved" chargers recommended for different models of their batteries (http://www.odysseybattery.com/documents ... pr2014.pdf). Basically, for my PC1500 battery they recommend only a few 25a or greater chargers that charge at 25amp and 14.7v for the initial phase, and then it drops to a trickle 13.6v as it nears full (technical stuff here: http://www.odysseybattery.com/documents ... 2_1214.pdf). I don't fully understand all of that, but what I have read around is that they basically don't want you to trickle charge to "maintain" these batteries unless they have a full charge first as that could ruin them.

EDIT: Here's a link where an Odyssey rep discusses this a little: http://www.i-bmw.com/showthread.php?t=37652

SFHLibertyCRD · **Posted:** Tue Jan 06, 2015 6:49 pm

dkenny wrote:

normal would around 14.0. or less
at 14.2-14.5 the water will boil out of the battery..
13.8v would be ideal..
13.3 - 13.6 even better if the battery was fully changed..say like drive for 20hrs non stop..

-dkenny

Are you sure about this? My VW TDI runs at around 14.5-14.6 and as you saw above, other users CRDs are in the 14.2-14.4 range.

tjkj2002 · **Posted:** Tue Jan 06, 2015 7:00 pm

dkenny wrote:

normal would around 14.0. or less
at 14.2-14.5 the water will boil out of the battery..
13.8v would be ideal..
13.3 - 13.6 even better if the battery was fully changed..say like drive for 20hrs non stop..

-dkenny

Normal cold should be above 14.5v,operating temps can drop to 13.8v but you still want above 14v.13.2 volts is the bare minimum to even actually charge a lead acid battery,AGM batteries like 14.8v+.

Oh and no water in a AGM battery and no 14.5v will not boil the water out of a lead acid battery.

tjkj2002 · **Posted:** Tue Jan 06, 2015 7:04 pm

SFHLibertyCRD wrote:

I think you are right about that, but in addition Odyssey has a special algorithm I think specifically for charging a discharged battery. They don't seem to support charging outside of these specs. They have a list of "approved" chargers recommended for different models of their batteries (http://www.odysseybattery.com/documents ... pr2014.pdf). Basically, for my PC1500 battery they recommend only a few 25a or greater chargers that charge at 25amp and 14.7v for the initial phase, and then it drops to a trickle 13.6v as it nears full (technical stuff here: http://www.odysseybattery.com/documents ... 2_1214.pdf). I don't fully understand all of that, but what I have read around is that they basically don't want you to trickle charge to "maintain" these batteries unless they have a full charge first as that could ruin them.

EDIT: Here's a link where an Odyssey rep discusses this a little: http://www.i-bmw.com/showthread.php?t=37652

As long as the charger is rated to charge AGM batteries it will be fine.I have 3 Odyssey batteries and bought there specific charger and it sucks badly at actually charging the battery. Reviving it from a full discharge it works great but otherwise worthless.

Switched to a BatteryMinder charger(2a,4a,and 8a charges) and it does a thousand times better job,sure may take longer but you don't want to heat the battery up to much while charging it.My 9 year old PC1500DT wouldn't hold a charge over night even after countless charges back to back with the "required" charger and 3 days on the BatteryMinder 12248 it held 12.8v for 9 months untouched when before it would drop from 12.8(rest voltage measured) to 11.8 in less then 10 hours.

SFHLibertyCRD · **Posted:** Tue Jan 06, 2015 7:08 pm

tjkj2002 wrote:

SFHLibertyCRD wrote:

I think you are right about that, but in addition Odyssey has a special algorithm I think specifically for charging a discharged battery. They don't seem to support charging outside of these specs. They have a list of "approved" chargers recommended for different models of their batteries (http://www.odysseybattery.com/documents ... pr2014.pdf). Basically, for my PC1500 battery they recommend only a few 25a or greater chargers that charge at 25amp and 14.7v for the initial phase, and then it drops to a trickle 13.6v as it nears full (technical stuff here: http://www.odysseybattery.com/documents ... 2_1214.pdf). I don't fully understand all of that, but what I have read around is that they basically don't want you to trickle charge to "maintain" these batteries unless they have a full charge first as that could ruin them.

EDIT: Here's a link where an Odyssey rep discusses this a little: http://www.i-bmw.com/showthread.php?t=37652

As long as the charger is rated to charge AGM batteries it will be fine.I have 3 Odyssey batteries and bought there specific charger and it sucks badly at actually charging the battery. Reviving it from a full discharge it works great but otherwise worthless.

Switched to a BatteryMinder charger(2a,4a,and 8a charges) and it does a thousand times better job,sure may take longer but you don't want to heat the battery up to much while charging it.My 9 year old PC1500DT wouldn't hold a charge over night even after countless charges back to back with the "required" charger and 3 days on the BatteryMinder 12248 it held 12.8v for 9 months untouched when before it would drop from 12.8(rest voltage measured) to 11.8 in less then 10 hours.

Sounds good, my 2/4/6a chargers sounds similar and is made by Schumacher (same company that makes the Odyssey brand chargers). Which setting do you usually put it on to get the battery charged up if it gets below 12?

tjkj2002 · **Posted:** Tue Jan 06, 2015 7:21 pm

SFHLibertyCRD wrote:

Sounds good, my 2/4/6a chargers sounds similar and is made by Schumacher (same company that makes the Odyssey brand chargers). Which setting do you usually put it on to get the battery charged up if it gets below 12?

I just set it on 8a and let it do it's thing.My charger also has a battery temp sensor,does desulfating also(freq modulated not voltage modulated which is bad for batteries).

jws84_02 · **Posted:** Tue Jan 06, 2015 9:04 pm

dkenny wrote:

normal would around 14.0. or less
at 14.2-14.5 the water will boil out of the battery..
13.8v would be ideal..
13.3 - 13.6 even better if the battery was fully changed..say like drive for 20hrs non stop..

-dkenny

Sorry, but everyone of these comments are incorrect

dkenny · **Posted:** Tue Jan 06, 2015 10:33 pm

care to post why?

AGM - Absorb glass mat--still lead acid..but with much less acid than flooded cell lead acid.
yes they use different voltages..but 13.8 -14.0..much more isn't good..

sorry..
but I have lots of batteries and solar cell charging experince..
lead acid is 13.3-13.8..its chemistry..
if the charger is running an equalization charge( not done in jeeps) the voltage will be higher that 13.8-14.1..think 15-16V..

-dkenny

dkenny · **Posted:** Tue Jan 06, 2015 11:03 pm

14.5 will boil the water out of a lead/acid battery..

14.0 will do the same..

been there..done that..
more that you care to count..
13.8 it almost too much for a lead acid battey.

13.3-13.6 it optimal. deal with it..
yes
I destroyed several batteries from too much voltage..

ok..
don't believe me..
you hook up a power supply that outputs 14.1V at 4 amp thru a light bulb..limits the current to 4ish amps..
m me in a 2 months..if the battery is still any good..and has fluid it still...oh a sealed type...good luck..

more fun use one that puts out 14.8V ..pm me in a month..the smell is you battery burning..it'll stink

sorry been there done that..
keep the voltages down 13.3.-13.6...
in the jeep under 14.0

use a good voltmeter..not the one in the dash..

-dkenny

jws84_02 · **Posted:** Wed Jan 07, 2015 8:14 am

I just feel in my experiences to have different results than you.

3 of my agm's I have now charge up to 15.5 and discharge down to 9.7-9.9. And those will be 5 years old this summer.

thermorex · **Posted:** Wed Jan 07, 2015 12:26 pm

dkenny wrote:

14.5 will boil the water out of a lead/acid battery..

14.0 will do the same..

been there..done that..
more that you care to count..
13.8 it almost too much for a lead acid battey.

13.3-13.6 it optimal. deal with it..
yes
I destroyed several batteries from too much voltage..

ok..
don't believe me..
you hook up a power supply that outputs 14.1V at 4 amp thru a light bulb..limits the current to 4ish amps..
m me in a 2 months..if the battery is still any good..and has fluid it still...oh a sealed type...good luck..

more fun use one that puts out 14.8V ..pm me in a month..the smell is you battery burning..it'll stink

sorry been there done that..
keep the voltages down 13.3.-13.6...
in the jeep under 14.0

use a good voltmeter..not the one in the dash..

-dkenny

Every good alternator that I measured charges at 14+ v. That can't be that all are bad and on my vehicles, I don't have charging/battery issues at all and I'm at 14.2-14.5v. From all I know, tj is correct. From the point of view of charging the battery with an external charger, it's different, maybe because you don't have any consumers?

SFHLibertyCRD · **Posted:** Wed Jan 07, 2015 2:06 pm

A quick, and maybe basic, follow-up question:

Will the voltage reading vary depending on the charge state of the battery? Will my obd scanner show lower the voltage rate when the battery is full or near full because the generator is charging at a lower voltage like a "smart" battery charger does? I know it certainly goes down if there is a draw, but I read that the PCM has a controller for the charging system/voltage in the 2005. Does that explain why I'm getting a lower running voltage reading from my brand new battery than from my nearly dead one? From the manual:

The amount of DC current produced by the generator is controlled by the EVR (field control) circuitry contained within the PCM. This circuitry is connected
in series with the second rotor field terminal and ground. A battery temperature sensor, located in the battery tray housing, is used to sense battery temperature. This temperature data, along with data from monitored line voltage, is used by the PCM to vary the battery charging rate. This is done by cycling the ground path to control the strength of the rotor magnetic field. The PCM then compensates and regulates generator current output accordingly.

alternator charging voltage, what should it be?

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