Charging Fullriver AGMs - Absorption (UO or constant Voltage) Phase

Submitted: Wednesday, Mar 03, 2010 at 16:44
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I'm setting up my new Durst 45 Amp charger for charging my AGM batteries. I recall that when looking at Fullriver specs in the past, there was a recommended time limit for the UO or constant voltage phase. The charger lets me select either 4 or 8 hours. The charger will move to the U (float) phase when the charge current has reduced to 10% of max or when the UO pre-set time has elapsed, whichever is reached first.

I'm buggered if I can find this UO recommended time in any of the Fullriver specs I have or can find. I've set at 4 hours at the moment, but my memory (which is often wrong these days) seems to suggest the right answer might be 8 hours.

Other than this issue, the charger set up has gone well. I've permanently mounted it in the canopy, hard wired to the batteries. Whenever I connect 240 Volts, the two Engels automatically switch to 240 and the charger starts pumping to the batteries.

The second charging output has an Anderson plug attached, so I can connect to any other battery for charging (either the boat or helping someone else).

Any of you battery experts out there able to help with the UO time issue?
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Reply By: Dennis Ellery - Wednesday, Mar 03, 2010 at 17:04

Wednesday, Mar 03, 2010 at 17:04
If your Fullriver AGM is about 100ah (their specs limit initial charge to less than 20 amps) and it is substantially discharged, then you could damage it with a 45 amp charger.
AnswerID: 407119

Follow Up By: Maîneÿ . . .- Wednesday, Mar 03, 2010 at 17:11

Wednesday, Mar 03, 2010 at 17:11
Yes, as Dennis has said the battery charger could be doing damage to your battery, as AGM's (generally) should be charged at ~10% of their capacity number. Eg, 100ah battery @ 10 Amps

Maîneÿ . . .
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FollowupID: 676943

Follow Up By: Member - Norm C (QLD) - Wednesday, Mar 03, 2010 at 19:09

Wednesday, Mar 03, 2010 at 19:09
Thanks for that Dennis and Mainey, but that is not the question I asked.

By the way, the Fullriver specs state 25 to max 35% of the rated 20 hr rate, not 20% or 10%. And just to reassure you some more, the 45 Amp capacity is used on 210 AH of batteries in a bank (120 + 90), so about 21%, well within the specs. When I charge a lower capacity, 120AH for boat for example, I switch to half power (22.5 Amp), so 18.5% of rated capacity, again well within the specs.

I'm using a charger at close to the Fullriver recommendations as it is often run from a generator (when not enough solar), so I want to charge as quickly as possible to get the genny off.

Norm C
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FollowupID: 676973

Follow Up By: Battery Value Pty Ltd - Wednesday, Mar 03, 2010 at 19:46

Wednesday, Mar 03, 2010 at 19:46
So what is the right time selection for the UO stage?

I recommend to follow this procedure:

Discharge your battery to about 50%.
Wait for the ambient temperature to come down to around 25 degrees.
Select the 8 hour UO time limit.
Select 14.7V for AGM.
Have the charger's temperature sensor mounted on the battery surface.
Disconnect any loads from the battery.
Aim for a C/5 or C/4 charging rate which is the full power mode on your 45A charger, for your 210Ah combo.
Connect a voltmeter across the battery terminals.
Connect charger to the batteries and turn on the charger.
Jot down the first time stamp, when the meter reading has reached 13.8V, which can take an hour or so.
Listen/watch the fan/yellow LED to turn off/change colour to green, which can be another hour or so.
Jot down this second time stamp.
Subtract your first time stamp from the second one, and add one hour.
If the result is less than four hours, select 4 hours for the UO timer.
If the result is more than four hours, select 8 hours for the UO timer.

Note if you regularly discharge your batteries to more than 50% to 60%, I recommend to select the 8 hr limit, regardless of the test result above.

A little caution:
because you've got a high rated charger, which lets you recharge your battery in the shortest possible time at the maximum recommended C/4.5 rate, it is definitely advisable to use the battery temperature sensor.
If for whatever reason you don't have this sensor, I recommend to reduce the boost charge setting from 14.7V to 14.4V during summer.
Be aware that the float voltages will be out as well without the T/S connected. Unfortunately these can't be tweaked.

Hope this helps.

Best regards, Peter
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FollowupID: 676983

Follow Up By: Member - Norm C (QLD) - Wednesday, Mar 03, 2010 at 20:16

Wednesday, Mar 03, 2010 at 20:16
Wow, Peter I was hoping for a simple either / or answer. But I understand what you are saying.

In my vehicle, one battery (the 90 AH) is in the engine bay, the other (120 AH) is in the canopy with the charger. If I connect the charger within a few hours of driving, the batteries will be at different temps - I do this pretty regularly when we have access to 240 Volt. As a result, I've chosen to set the charger at 14.4 Volts as a 'safety' mechanism for the moment.

Doing what you suggest will have to wait a while till we are camped up in one place for a few days or more. At Uluru at the moment and will be doing West and East MacDonnell Ranges for next couple of weeks.

Thanks
Norm C
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FollowupID: 676994

Follow Up By: Battery Value Pty Ltd - Wednesday, Mar 03, 2010 at 20:52

Wednesday, Mar 03, 2010 at 20:52
No worries Norm,

sometimes things can get a bit more complicated than they should ;)

A quick and easy one for you:

Because a battery at a higher temperature will always delay the boost/float switchover, and you'd probably have a fridge connected which delays this even more, do this:
When it comes to recharging, turn on your gennie/45A charger and watch the voltage on the battery go up to 13.8V.
From then on, check the time it takes for the green charger LED to come on.
If it's 4 hours (with the switch set to 4 hours), then you've obviously run into the time limit.
This means the absorption stage hasn't finished, thus select 8 hours.
If the green LED comes on before the 4 hour mark, leave the dip switches in the 4 hour position.
If the green LED won't come on after 5 or 6 hours, check temperatures of both batteries and if warmer than 37 degrees, stop charging and keep the 4 hour selection @ 14.4V.
You can't fully charge a warm battery without a T/S...
Caution, according to the manual, make sure neither dip switches 1 and 2 are on at the same time, nor 3 and 4.

Fascinating typing this to you, while knowing this bloke is at the center of it all!

Best regards, Peter
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FollowupID: 676998

Follow Up By: Member - Norm C (QLD) - Wednesday, Mar 03, 2010 at 21:05

Wednesday, Mar 03, 2010 at 21:05
Thanks for that Peter. I'll do that next time I need to run the genny. With good weather that might be a while as I have a fair bit of solar - though this hot weather sucks the power via the fridges.

You might recall, you helped me select the Durst charger.

Norm C
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Follow Up By: Dennis Ellery - Wednesday, Mar 03, 2010 at 21:07

Wednesday, Mar 03, 2010 at 21:07
Norm I am only quoting their website specs.
Obviously you have more detailed information
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Follow Up By: Battery Value Pty Ltd - Wednesday, Mar 03, 2010 at 21:17

Wednesday, Mar 03, 2010 at 21:17
Yep, I remember Norm.....

And I'm really getting to know their smaller 25A charger siblings quite a bit ;)

Best, Peter
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FollowupID: 677009

Follow Up By: Member - Norm C (QLD) - Wednesday, Mar 03, 2010 at 21:49

Wednesday, Mar 03, 2010 at 21:49
Dennis, try this link:
Fullriver DC battery manual

Click on the manual download at the bottom of the page. Heaps of info in it, but the answer to your question is in the graph on page 9.

This is for DC batteries. The same info is available in another document for HGLs (I use both). But for this question there is not much (if any) difference.

Norm C


















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Follow Up By: Dennis Ellery - Thursday, Mar 04, 2010 at 00:48

Thursday, Mar 04, 2010 at 00:48
Conflicting information
I have a Fullriver DCG100-12
The specs on the side of the Battery say its a Gel.
Max charge current 20amp
The Accc says that it is AGM
What is it, AGM or Gel?

I have listed this under a new thread hoping that the distributor or some other informed person will shed some light on the matter.

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FollowupID: 677054

Follow Up By: Maîneÿ . . .- Thursday, Mar 04, 2010 at 09:08

Thursday, Mar 04, 2010 at 09:08
Dennis,
I believe you will fine it's an "AGM" battery (design)
filled with "gel" (contents)

It's an "AGM gel" battery as opposed to the more common AGM liquid battery

Maîneÿ . . .
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FollowupID: 677071

Follow Up By: Battery Value Pty Ltd - Thursday, Mar 04, 2010 at 10:00

Thursday, Mar 04, 2010 at 10:00
Dennis,

I don't know much about F/R marketing stunts, but if you want to find out if your battery is AGM or gel, read on:

From your published excerpt in the other thread:

....contained only 0.55% silicon dioxide....

This is the stuff the glass matting and the gel consists of.
Applying the percentage above to a 100Ah AGM battery which weighs around 30kg, the glass matting inside this battery would weigh 165 grams. This sounds about right if you take into account the highly porous nature of the SiO2 microfibres.
The matting is only a couple of mm in thickness, and is only as large in area as the plates.
The plates and separators are surrounded by space, only filled with gas.

Because the same stuff in a gel comes in a denser and less porous form, it's heavier than the AGM separator material.
What's more, this gelled form of silicon dioxide is pumped into the battery container under vacuum filling every void in it.

That's why a VRLA gel battery will always be heavier than a VRLA AGM battery at the same cpacity rating.

If you're in doubt about the type of VRLA of yours, put the battery on a scale.
For a 100Ah capacity, the AGM will weigh around 30 kg, a gel at the same capacity will weigh at least 5 kg more.

Hope this helps a bit.

Best regards, Peter
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FollowupID: 677076

Follow Up By: Member - Mike DID - Thursday, Mar 04, 2010 at 14:03

Thursday, Mar 04, 2010 at 14:03
"Yes, as Dennis has said the battery charger could be doing damage to your battery, as AGM's (generally) should be charged at ~10% of their capacity number. Eg, 100ah battery @ 10 Amps "
- Norm, Mainey has shown many times that he's unable to understand manufacturers data sheets.

Every AGM Battery Data Sheet I've read recommends a maxmium charging current of 0.20 to 0.25C - i.e. 20 to 25 amps for a 100 amphour battery.

But don't panic too much about exceeding this recommendation occasionally - batteries only draw a high current if they've been heavily discharged.

Here is an extract from the Lifeline Technical Manual - "Due to the Low Impedance design, Lifeline batteries can tolerate inrush current levels as high as 5C (500 amps for 100 amphour battery)".
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FollowupID: 677112

Follow Up By: Member - Mike DID - Thursday, Mar 04, 2010 at 14:06

Thursday, Mar 04, 2010 at 14:06
"I believe you will fine it's an "AGM" battery (design) filled with "gel" contents)

It's an "AGM gel" battery as opposed to the more common AGM liquid battery "

- It's not even Friday Funny Day today !!!!!!
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FollowupID: 677113

Follow Up By: Dennis Ellery - Thursday, Mar 04, 2010 at 14:17

Thursday, Mar 04, 2010 at 14:17
To Battery Value.
Peter, that’s not a satisfactory way to determine the construction of a battery.
To Mike
I agree and have a looked at a couple of Data sheets for Fullriver AGM's and those I look at showed a limit of 20% where as the higher quality batteries can tolerate massive inrush currents.
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FollowupID: 677114

Follow Up By: Battery Value Pty Ltd - Thursday, Mar 04, 2010 at 15:37

Thursday, Mar 04, 2010 at 15:37
@ Mike and Dennis,

I'm not impressed by what's in their manual for Conc - L/line.

For starters, their maximum boost charge voltage is specified 14.3V versus other manufacturers' 14.7V.

This translates to longer overall charging times because the lower voltage during the absorption stage causes less charging current to flow during this stage.
In contrast to this, elsewhere in the manual they state their battery can be fully recharged within 2 hours. Something's not adding up.

Obviously in an attempt to backup this lofty 2 hour charging claim, they pull another one out of their hat:

It's this hilarious claim about the 5C inrush charge current 'level'.

Take their 100Ah battery's typical internal resistance of 12 milliOhms and multiply by 500A.
The resulting voltage is 6V.
Now add to this the OCV, resulting in a terminal voltage of about 18 to 19V.

Hellooooo!....the max charging voltage allowed is only 14.3V....so this kind of current isn't gonna happen.
Just another case of wishful thinking which only exists in the brains of their marketing gurus.

Hope this explains why you have to take some claims with a grain of salt.

Best regards, Peter
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FollowupID: 677134

Follow Up By: Dennis Ellery - Thursday, Mar 04, 2010 at 16:17

Thursday, Mar 04, 2010 at 16:17
Peter,
Concorde have a proven track record.
Aero companies, armies, medical organisations etc use them.
These organisations have large engineering organisations to evaluate products.

Who's claims are we going take with a grain of salt - yours or thiers?
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FollowupID: 677143

Follow Up By: Battery Value Pty Ltd - Thursday, Mar 04, 2010 at 16:39

Thursday, Mar 04, 2010 at 16:39
Dennis,

that's an interesting observation of yours.

But it disappoints in that it lacks the extraordinary explanation necessary for an extraordinary claim :(

Best regards, Peter
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FollowupID: 677148

Follow Up By: Member - Mike DID - Thursday, Mar 04, 2010 at 16:50

Thursday, Mar 04, 2010 at 16:50
"It's this hilarious claim about the 5C inrush charge current 'level'.
Take their 100Ah battery's typical internal resistance of 12 milliOhms and multiply by 500A. The resulting voltage is 6V. Now add to this the OCV, resulting in a terminal voltage of about 18 to 19V.
Hellooooo!....the max charging voltage allowed is only 14.3V....so this kind of current isn't gonna happen. "

They make it quite clear that 14.3 volts is the NORMAL voltage that results in 25 amps NORMAL charge current and that 500 amps as an exceptional charge current will not destroy the battery - obviously you need a higher voltage to force in this EXCEPTIONAL charge current.
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FollowupID: 677149

Follow Up By: Battery Value Pty Ltd - Thursday, Mar 04, 2010 at 18:35

Thursday, Mar 04, 2010 at 18:35
Mike,

if you really still think you can charge this 100Ah AGM with 500 amps at a terminal voltage of 18 to 19V then look at it from this angle:

At an internal resistance of 12 milliOhms and a current of 500 amps, there will be localized heating near the plates surfaces and other areas of low conductivity, and we're not looking at peanuts.

More specifically we're looking at 3,000 Watts of heat generating power in this case.

If you take into account that the gassing rate rises exponentially with temperature (Arrhenius equation), and on top of this comes the heat from the oxygen cycle together with the 3,000W heat pump, the battery will enter thermal runaway before you know it.
Then there will be fast electrolysis which forms significant amounts of hydrogen and oxygen gas as the temperature rises....not good.

Even if you manage to avoid an explosion by hitting the red button on the wall, your precious (because starved) electrolyte level would have dropped significantly during this exercise.
What's more, the enormous rate of hydrogen generation would have torn open the smoothly packed negative plate surface to some extent, knocking loose some active material.

Don't even think of forcing 500 amps of charging current through any 100Ah VRLA AGM battery, in the hope that you can fast charge it that way.

Best regards, Peter
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FollowupID: 677167

Follow Up By: Dennis Ellery - Thursday, Mar 04, 2010 at 20:35

Thursday, Mar 04, 2010 at 20:35
Peter these calculations you keep producing bear no relation to reality.
The resistance in a Concorde battery is so low that there is virtually no heat generated in them and they specify higher charge limits. Obviously this doesn’t apply to those like Fullriver as their data sheets specify limits of charge current to 20% C. This is all pretty well documented stuff.
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FollowupID: 677184

Follow Up By: Member - Mike DID - Thursday, Mar 04, 2010 at 21:03

Thursday, Mar 04, 2010 at 21:03
" if you really still think you can charge this 100Ah AGM with 500 amps at a terminal voltage of 18 to 19V"

For goodness sake, learn the meaning of "inrush current" before you totally destroy your credibility. Ohms law is useless you know how to apply it.
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FollowupID: 677190

Follow Up By: Battery Value Pty Ltd - Thursday, Mar 04, 2010 at 21:06

Thursday, Mar 04, 2010 at 21:06
Dennis,

so how low is it then?

Let me tell you: a Conc L/line 100Ah has 12 milliOhms, twice as much as a similar AGM from the competition.

Why's that?
A bit of insider knowledge for you: In the beginning of their AGM ventures they had such a high fault rate in their AGM production lines due to micro shorting within the glass matting, caused by carelessness of their workers.
To counter this problem they put additional plastic wrappers around the positive plates at the expense of increasing the internal resistance of the battery.

Because internal resistance is undesirable in any voltage source, they had to make their marketing dept work overtime to spread the exact opposite of the truth.

BTW, just in case you wonder what my calculations are based on:
power equals current squared times resistance, works out at 3,000Watts.
Not even Conc can get around this little obstacle.

The 12 milliOhms is not a figure I pull out of my hat willy nilly, it's derived from their published Peukert data and discharge curves for their L/line product.

So, I'm sorry to say that they can't bend the rules of nature even though they try everything to make you believe the opposite.

Best regards, Peter
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FollowupID: 677194

Follow Up By: Battery Value Pty Ltd - Thursday, Mar 04, 2010 at 21:29

Thursday, Mar 04, 2010 at 21:29
Mike,

the term inrush current is a misnomer for battery charging purposes.

It's been borrowed from electrical/electronics components and circuits, and the time constants involved are generally in the sub second region.

It's certainly futile to use a 500A current pulse of short duration to cut the recharing time down to 2 hours.

For this to be achieved, both the bulk and absorption currents would have to be increased.

But exactly this cannot be done without increasing the boost voltage beyond the specified level which in this case is 14.3V.

In many cases, the competitions boost voltage is specified at 14.7V which allows for faster recharging times.

So why exactly do you think this product is so superior?

Best regards, Peter
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FollowupID: 677201

Follow Up By: Member - Mike DID - Thursday, Mar 04, 2010 at 21:33

Thursday, Mar 04, 2010 at 21:33
Did anyone know Mainey had a twin brother ?
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Follow Up By: Member - Norm C (QLD) - Friday, Mar 05, 2010 at 22:12

Friday, Mar 05, 2010 at 22:12
Just to be clear, this follow up is to Mike R's follow up No 13, extract quoted here:

"Yes, as Dennis has said the battery charger could be doing damage to your battery, as AGM's (generally) should be charged at ~10% of their capacity number. Eg, 100ah battery @ 10 Amps "
- Norm, Mainey has shown many times that he's unable to understand manufacturers data sheets.

Every AGM Battery Data Sheet I've read recommends a maximum charging current of 0.20 to 0.25C - i.e. 20 to 25 amps for a 100 amphour battery.

But don't panic too much about exceeding this recommendation occasionally - batteries only draw a high current if they've been heavily discharged."


The link I posted at follow up No 9 is (to me) pretty clear, in that I = .25 of 20 hr rate to a max of .35. But Mike, even if I accept your more generic .20 to .25, I fall within that range anyway. On full power on bank of 210 AH, I max will be about 21%. On half power on 120 AH, I max will be about 22.5%. I just have to make sure I select half power if the 120 AH is the only battery on charge. Am I at least close to right?

I max only applies until battery voltage gets up to 13.8 Volts. So far, this has only ever been a few minutes, as all my batteries are also on solar and I've been doing a fair bit of driving. 4 hours today around the Mereenie Loop from Kings Canyon to Hermannsburg - only to find the Palm Gorge road and the Hermannsburg historical precinct closed. So did another hour or so to Alice. At least I got the batteries charged.

Norm C
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FollowupID: 677376

Follow Up By: Member - Mike DID - Friday, Mar 05, 2010 at 22:43

Friday, Mar 05, 2010 at 22:43
"The link I posted at follow up No 9 is (to me) pretty clear, in that I = .25 of 20 hr rate to a max of .35. But Mike, even if I accept your more generic .20 to .25, I fall within that range anyway. On full power on bank of 210 AH, I max will be about 21%. On half power on 120 AH, I max will be about 22.5%. I just have to make sure I select half power if the 120 AH is the only battery on charge. Am I at least close to right? "

Yes, your charging currents are well within the range recommended by manufacturers for a long battery life.
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FollowupID: 677384

Follow Up By: Maîneÿ . . .- Friday, Mar 05, 2010 at 22:51

Friday, Mar 05, 2010 at 22:51
Mike,

what brand of solar panel did you buy ??

Maîneÿ . . .
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FollowupID: 677388

Reply By: Peter_n_Margaret - Wednesday, Mar 03, 2010 at 19:45

Wednesday, Mar 03, 2010 at 19:45
What is the constant voltage output of the charger?

Cheers,
Peter.
AnswerID: 407147

Follow Up By: Member - Norm C (QLD) - Wednesday, Mar 03, 2010 at 19:58

Wednesday, Mar 03, 2010 at 19:58
Hi Peter, it is adjustable to either 14.4 or 14.8 Volts.

Norm C
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FollowupID: 676987

Reply By: R&J Batteries - Tuesday, Mar 09, 2010 at 09:49

Tuesday, Mar 09, 2010 at 09:49
What model Durst charger is it exactly?

45A is on the high side of charge limitation for ANY battery around 100Ah. I would set the timeout to 4 hours to prevent overheating the battery just in case it gets accidentally deeply discharged.

The Absorb stage should be set to 14.5V and Float to 13.7V.

Regards, Dave
AnswerID: 408010

Follow Up By: Member - Norm C (QLD) - Tuesday, Mar 09, 2010 at 14:46

Tuesday, Mar 09, 2010 at 14:46
It is a BCS 1245B. I bought it as it has a half power mode (simple push button). When charging less than 200 AH or so, I will operate on half power. At full power it will quickly charge a battery bank.

One of the batteries I will be charging is from you Dave. A Fullriver 120 AH DC that I picked up in Tassie - we exchanged emails about it at the time. When that battery is charged alone, it will be on half power.

Absorption is currently set on 14.4 Volts and I measure it as 14.4. Float is notionally 13.8, but I measure it at 13.72.

Norm C
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FollowupID: 677959

Follow Up By: R&J Batteries - Tuesday, Mar 09, 2010 at 16:18

Tuesday, Mar 09, 2010 at 16:18
Manufacturing tolerances are around 5% normally so that will be fine.

Dave
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FollowupID: 677976

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