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Surface charge/charger #4640120
01/19/18 04:28 PM
01/19/18 04:28 PM
Joined: Jan 2016
Posts: 603
Nebraska
Duffyjr Offline OP
Duffyjr  Offline OP
Joined: Jan 2016
Posts: 603
Nebraska
I understand you need to wait for the surface charge to be eliminated to accurately test a battery with a volt meter but what I was wondering is if it's a good idea to wait to put a charger on it.

I have a CTEK 4.3 so lets use that charger as an example if it matters. No where in the manual does it mention surface charge.

I just put a new battery in my Buick a couple weeks ago and have been playing around with one of those volt meters you plug into a cigarette lighter socket. In the mornings it's down to 12.45ish so I'm guessing they sold me an old battery or I just need to put in on my CTEK.

Pretty sure the alternator is ok. This morning it started charging at 14.70 and by the time I got to work ten minutes later it was at 13.90.


89 GMC Sierra T5 10w30/Wix
08 Lucerne CX NAPA Blend 5w30/Napa Gold
18 Toro Super Recycler T5 10w30
Re: Surface charge/charger [Re: Duffyjr] #4640164
01/19/18 05:08 PM
01/19/18 05:08 PM
Joined: Jan 2016
Posts: 315
Cheshire, England
barryh Offline
barryh  Offline
Joined: Jan 2016
Posts: 315
Cheshire, England
I've only ever thought of surface charge as impacting on an open circuit voltage tests to determine the state of charge of a battery.

I guess you are asking does it impact on an automatic battery charger in terms of the voltage it senses. If it does it has to be a universal thing that charger manufacturers have always taken in to account. If the vehicle has been in use I tend to wait before charging anyway to allow the battery to cool as temperature also impacts on voltage and charging current.


Barry

1979 BMW R45 (Triple QX 5W40)
2009 Mercedes C180K (Shell Helix Ultra 5W40)
Re: Surface charge/charger [Re: Duffyjr] #4640172
01/19/18 05:12 PM
01/19/18 05:12 PM
Joined: Mar 2004
Posts: 20,758
Upstate NY
Donald Offline
Donald  Offline
Joined: Mar 2004
Posts: 20,758
Upstate NY
Originally Posted By: Duffyjr
I understand you need to wait for the surface charge to be eliminated to accurately test a battery with a volt meter but what I was wondering is if it's a good idea to wait to put a charger on it.

I have a CTEK 4.3 so lets use that charger as an example if it matters. No where in the manual does it mention surface charge.

I just put a new battery in my Buick a couple weeks ago and have been playing around with one of those volt meters you plug into a cigarette lighter socket. In the mornings it's down to 12.45ish so I'm guessing they sold me an old battery or I just need to put in on my CTEK.

Pretty sure the alternator is ok. This morning it started charging at 14.70 and by the time I got to work ten minutes later it was at 13.90.


I would first check accuracy of your voltmeter before you take any action.

Know anyone with a Fluke?


2015 Subaru Forester 2.5 engine/CVT
2015 Ford F250 w/Powerstroke
2016 Subaru Crosstrek CVT (wife's)
Re: Surface charge/charger [Re: Duffyjr] #4640204
01/19/18 05:32 PM
01/19/18 05:32 PM
Joined: Dec 2016
Posts: 63
Soonerville
379KITTY Offline
379KITTY  Offline
Joined: Dec 2016
Posts: 63
Soonerville
I discovered a similiar issue awhile back, which also prompted me to get a DVM that plugs into lighter. I had noticed that at times my phone would charge as expected, other times very little. My 2005 I learned controls alternator output via the PCM/ECM (pick your term), as opposed to internally regulated alternators as in recent past. After some in-depth research, I learned the PCM will let alt output/batt volts drop to as low as 12.2 at times before ramping up output. All in the quest for fuel economy. Certain things supposedly prevent this (high blower and high beams, rear defogger), but confirmed with DVM and driving. Another technology not unlike stop/start, although probably not as effective.


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77 Vette
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Re: Surface charge/charger [Re: Duffyjr] #4640205
01/19/18 05:32 PM
01/19/18 05:32 PM
Joined: Mar 2016
Posts: 1,226
CA
CharlieBauer Offline
CharlieBauer  Offline
Joined: Mar 2016
Posts: 1,226
CA
I wondered this too. You could always remove the surface charge to be sure.

But I would think that this is taken care of by the smart charger or does not affect getting it fully charged through the absorption stage. After all, as soon as the battery is charged by the smart charger, won't it begin reading a surface charge anyway? Or is the current too low to create a surface charge?


It ain't what you don't know that gets you into trouble. It's what you know for sure that ain't so.

- mistakenly attributed to Mark Twain
Re: Surface charge/charger [Re: Donald] #4640211
01/19/18 05:34 PM
01/19/18 05:34 PM
Joined: Jan 2016
Posts: 603
Nebraska
Duffyjr Offline OP
Duffyjr  Offline OP
Joined: Jan 2016
Posts: 603
Nebraska
Originally Posted By: Donald
Originally Posted By: Duffyjr
I understand you need to wait for the surface charge to be eliminated to accurately test a battery with a volt meter but what I was wondering is if it's a good idea to wait to put a charger on it.

I have a CTEK 4.3 so lets use that charger as an example if it matters. No where in the manual does it mention surface charge.

I just put a new battery in my Buick a couple weeks ago and have been playing around with one of those volt meters you plug into a cigarette lighter socket. In the mornings it's down to 12.45ish so I'm guessing they sold me an old battery or I just need to put in on my CTEK.

Pretty sure the alternator is ok. This morning it started charging at 14.70 and by the time I got to work ten minutes later it was at 13.90.


I would first check accuracy of your voltmeter before you take any action.

Know anyone with a Fluke?


No Fluke but I have tested it against my Craftsman meter and they were identical.


89 GMC Sierra T5 10w30/Wix
08 Lucerne CX NAPA Blend 5w30/Napa Gold
18 Toro Super Recycler T5 10w30
Re: Surface charge/charger [Re: Duffyjr] #4640333
01/19/18 07:34 PM
01/19/18 07:34 PM
Joined: Jan 2009
Posts: 6,200
New England
gathermewool Offline
gathermewool  Offline
Joined: Jan 2009
Posts: 6,200
New England
Pretty sure the smart chargers compare voltage and voltage CHANGE (dV/dT) for the given charge current, so the surface charge won't matter at all. I get rid of the surface charge for measurement, if I need to (I rarely do), by turning on the headlights for a minute while the engine is off. For hooking up my smart charger, I'll sometimes do so and turn it on soon after stopping the engine after parking. The percentage full indicator may read erroneously high at first, but it tends to charger longer if I haven't charged it in a while (thank you fuel efficiency-oriented charging logic!) and less if it's been driven for on long trips or been charged recently.


'14 Forester XT FA20DIT (Cobb Stage 1)
Edge 0W-40 + FU filter
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Re: Surface charge/charger [Re: Duffyjr] #4640374
01/19/18 08:12 PM
01/19/18 08:12 PM
Joined: Dec 2002
Posts: 42,085
New Jersey
JHZR2 Offline
JHZR2  Offline
Joined: Dec 2002
Posts: 42,085
New Jersey
This does happen sometimes. Not always.

On my MB diesels with no real electronics, often when I turn the engine off, if I connect a charger, it will report 100% and be fooled.

It's simple enough to burn off a surface charge.


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