Please would you tell me how to get my new high quality battery fully charged? - JeepForum.com
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post #1 of 123 Old 05-10-2021, 06:57 AM Thread Starter
Delta0
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Please would you tell me how to get my new high quality battery fully charged?

We don't use the car very often.
I keep the battery charged with a Ctek MXS 5.0 charger while itís parked.

We went out last week with a new, fully charged, good quality battery.
Ambient temperature in the mid 50s.

The battery is an Exide EA770. http://www.exide.info/spec/ea770.html

The voltage at the socket in the car was a happy 14.4 at first.
At about a mile it dropped below a sad 14v.

A drop of 0.4v might not sound much but it makes a monster difference to the charge rate.

Even worse, it dropped to low 13s by the end of the outbound trip, about 4 miles.
13.4v ainít enough grunt to pull the skin off a rice pudden.

The only extras we had using electricity were the heater on low, an occasional seat adjustment, we opened the roof a short way once, and closed it once.

Battery voltage the next morning was below 12.6.
Battery voltage 24hrs after I disconnect the Ctek is above 12.8.

Please would you tell me how to get the alternator to charge the battery properly?

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post #2 of 123 Old 05-10-2021, 07:26 AM
smokeyyank
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So the WJ doesn't hold a constant 14v. It fluctuates based on several factors. Is it running odd or are you just concerned the voltage is fluctuating?
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post #3 of 123 Old 05-10-2021, 07:39 AM
snowbuggy
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My WJ's with remote door locks will drain the battery in a few weeks. My only WJ without remote door locks doesn't drain the battery at all.
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post #4 of 123 Old 05-10-2021, 08:19 AM
WJ60
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Check all connections at the battery and alternator for corrosion, looseness, etc. Take it to an auto parts store who can test the alternator.
Keep in mind as the battery reaches full charge the charging voltage from the alternator will drop.
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post #5 of 123 Old 05-10-2021, 08:56 AM
2oldjeeps
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The voltage at the socket in the car was a happy 14.4 at first.


if it does that each start,you alt is ok...

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post #6 of 123 Old 05-10-2021, 09:39 AM
HarryH3
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Automotive charging systems are temperature compensated. As the weather gets warmer, the charging voltage will drop. WJ's have a temp sensor under the battery for this. It's in the center of the battery tray. 13.8 volts is what you'll typically see during cold weather, but this can drop into the 13-13.2 volt range in hot weather. A 12 volt lead-acid battery is considered fully charged at ~12.6 volts (~2.1 volts per cell. There are six cells).

I hope that the volt meter you are using at the socket is not very accurate, as 14.4 volts is high enough to boil off electrolyte unless the temp is really cold. As long as you're staying above 13 volts (with a known-good meter) then your batter is not being discharged as you drive.

On some vehicles you may see the voltage drop lower at idle, if you have a lot of accessories running at the time. My '94 Suburban only has a 105 amp alternator, but that rating is at 1,500+ engine RPM. (Alternators all have output curves that drop off dramatically as RPM drops). The Sub also has dual HVAC systems. If I have both of those fans on high, plus the headlights, wipers, radio, and the two 100 watt driving lights on, then the voltage drops off quite a bit at idle. Enough that the lights all dim slightly. It's not a problem in normal driving, but I wouldn't leave it idling for a long time like that. The system recovers as soon as I'm on the throttle again.
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post #7 of 123 Old 05-10-2021, 09:40 AM Thread Starter
Delta0
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Quote:
Originally Posted by smokeyyank View Post
So the WJ doesn't hold a constant 14v. It fluctuates based on several factors. Is it running odd or are you just concerned the voltage is fluctuating?
Thanks SmokeyYank.

My car runs nicely.

I'm concerned because I come back after a run with a battery that is nowhere near well charged.

I understand about regulators dropping voltage when the battery is well charged.
In this case the alternator is dropping voltage before the battery is well charged.
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post #8 of 123 Old 05-10-2021, 09:41 AM Thread Starter
Delta0
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Quote:
Originally Posted by snowbuggy View Post
My WJ's with remote door locks will drain the battery in a few weeks. My only WJ without remote door locks doesn't drain the battery at all.
Thanks SnowBuggy.
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post #9 of 123 Old 05-10-2021, 09:43 AM Thread Starter
Delta0
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Quote:
Originally Posted by WJ60 View Post
Check all connections at the battery and alternator for corrosion, looseness, etc. Take it to an auto parts store who can test the alternator.
Keep in mind as the battery reaches full charge the charging voltage from the alternator will drop.
Thanks WJ60.

My charging voltage is dropping before the battery gets well charged.
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post #10 of 123 Old 05-10-2021, 09:45 AM Thread Starter
Delta0
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Thanks, TwoOldJeeps.

Yeah, my alternator seems Ok.
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post #11 of 123 Old 05-10-2021, 09:48 AM
three_jeeps
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Quote:
Originally Posted by Delta0 View Post
We don't use the car very often.
I keep the battery charged with a Ctek MXS 5.0 charger while itís parked.

We went out last week with a new, fully charged, good quality battery.
Ambient temperature in the mid 50s.

The battery is an Exide EA770. http://www.exide.info/spec/ea770.html

The voltage at the socket in the car was a happy 14.4 at first.
At about a mile it dropped below a sad 14v.

A drop of 0.4v might not sound much but it makes a monster difference to the charge rate.

Even worse, it dropped to low 13s by the end of the outbound trip, about 4 miles.
13.4v ainít enough grunt to pull the skin off a rice pudden.

The only extras we had using electricity were the heater on low, an occasional seat adjustment, we opened the roof a short way once, and closed it once.

Battery voltage the next morning was below 12.6.
Battery voltage 24hrs after I disconnect the Ctek is above 12.8.

Please would you tell me how to get the alternator to charge the battery properly?
I believe your comment about 0.4 volts drop is incorrect. Batteries charge by a constant current. Electronic VR will vary the charge current wrt terminal voltage. While a voltage differential is needed the 0.4 volts is meaningless.

IIRC, the target/stable voltage at the battery when car is running is approximately 13.8 vdc.
It is normal for the voltage to start higher then drift down a bit.
If you are concerned about battery going dead when parked, you need to do a draw down test. Explained nicely in the Jeep FSM. IIRC, the at-rest current after all the devices have powered down after key removed is 30-50 mA (my jeep was always at 60 ma). It will take about 2 mins for all the devices to reach their at rest current draw.
At that rate of discharge, the battery would not be able to start the jeep after approximately 2.5-3 weeks.
In my experience, the two most common sources of excessive current draw are the radio and the amp under the rear seat.
Good luck
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post #12 of 123 Old 05-10-2021, 09:54 AM Thread Starter
Delta0
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Quote:
Originally Posted by HarryH3 View Post
. . . .

I hope that the volt meter you are using at the socket is not very accurate, as 14.4 volts is high enough to boil off electrolyte unless the temp is really cold. As long as you're staying above 13 volts (with a known-good meter) then your batter is not being discharged as you drive.

. . .
Thanks HarryH3,

The problem is my battery is being discharged as I drive.
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post #13 of 123 Old 05-10-2021, 10:02 AM Thread Starter
Delta0
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Quote:
Originally Posted by three_jeeps View Post
I believe your comment about 0.4 volts drop is incorrect. Batteries charge by a constant current. Electronic VR will vary the charge current wrt terminal voltage. While a voltage differential is needed the 0.4 volts is meaningless.

IIRC, the target/stable voltage at the battery when car is running is approximately 13.8 vdc.
It is normal for the voltage to start higher then drift down a bit.
If you are concerned about battery going dead when parked, you need to do a draw down test. Explained nicely in the Jeep FSM. IIRC, the at-rest current after all the devices have powered down after key removed is 30-50 mA (my jeep was always at 60 ma). It will take about 2 mins for all the devices to reach their at rest current draw.
At that rate of discharge, the battery would not be able to start the jeep after approximately 2.5-3 weeks.
In my experience, the two most common sources of excessive current draw are the radio and the amp under the rear seat.
Good luck
Thanks three_jeeps
Current draw showed a normal range draw.

Thanks, Mike

PS, you wrote "I believe your comment about 0.4 volts drop is incorrect."

I can send you the argument on which I base my comment if you wish.
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post #14 of 123 Old 05-10-2021, 11:18 AM
HarryH3
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Quote:
Originally Posted by Delta0 View Post
Thanks HarryH3,

The problem is my battery is being discharged as I drive.
No, the problem is either a) your home charger is overcharging your battery, b) your voltmeter is not accurate, or c) the voltage is dropping as you drive because the PCM sees that the battery is already overcharged (because of a) and thus letting the battery voltage return to normal.

13.2 volts as you're driving is just fine. That will keep the battery properly charged.
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post #15 of 123 Old 05-10-2021, 11:25 AM
HampshireWJ
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Intersetingly (or not) , I recently bought a new battery to replace one that is probably at least 10 years old, and there are two points in your original posting that made me think. Not using the vehicle very much and that your outward journey was only four miles. I have had it in my head for years that it takes at least 8 miles to restore the battery power from actually starting the vehicle. I mention the new battery as there is an addition to the paperwork warning of sulphation taking place as a vehicle stands, prevalent due to covid and vehicles standing - they say that to combat this, the battery should be recharged when an open circuit voltage of 12.5 volts is reached, and that the solution is regular compensation charging with a modern battery charger. So I am thinking rather than leave the CTEK on the battery all the time, let it have more of a charge at regular intervals?
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