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Old 05-02-2014, 18:49   #1
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Acceptable variance in new batteries

I bought some new Trojan T105's and found that one of them shows a slightly lower state of charge than the others. Is this likely to affect the performance of the whole bank?

While still in the garage, I charged them in 12V pairs and then let them rest, but one was 0.04V lower than the others. So I charged that again with the next lowest one, letting the pair float for a day. As soon as they were disconnected, the suspect one still showed a slightly lower voltage, and now a week later it's back to 0.04V lower again. Temperature is around 25 degrees C.

The actual reading is 6.33V, although I am aware cheap multimeters may not be accurate. The SG reads 1.280-1.285 compared to around 1.300 for the others. Both these readings seem fine according to Trojan's User Guide, and the variance is well under their 0.3V guideline for equalizing.

But their table also shows this one battery is 5% less charged than the others. Won't this tend to drag the others down to its level when they are connected together?

They were all fresh from the distributor, and stamped with the same dates. I don't yet have the equipment to equalize (to be installed in 2-3 months), otherwise I would do so, but should I have to for new batteries anyway?

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Old 05-02-2014, 19:00   #2
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Re: Acceptable variance in new batteries

What are the hydrometer measurements a ross all the new batteries?
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Old 05-02-2014, 19:16   #3
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Re: Acceptable variance in new batteries

SG in others is average 1.300. One cell is 1.305, lowest is 1.295.

In the suspect battery, 1.280 - 1.285.
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Old 05-02-2014, 19:24   #4
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Re: Acceptable variance in new batteries

From my experience the bad ass will pull the rest down.

No way to get it to equal charge with the rest?

b.
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Old 05-02-2014, 19:26   #5
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Re: Acceptable variance in new batteries

Your choice: call Trojan now or wait until you can equalize. I'd call now myself. Please let me know your resolution: I'm looking at Trojans when I replace mine based on HandyBob's blog, http://handybobsolar.wordpress.com.
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Old 06-02-2014, 07:06   #6
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Re: Acceptable variance in new batteries

Quote:
Originally Posted by Wanderlust View Post
I bought some new Trojan T105's and found that one of them shows a slightly lower state of charge than the others. Is this likely to affect the performance of the whole bank?

While still in the garage, I charged them in 12V pairs and then let them rest, but one was 0.04V lower than the others. So I charged that again with the next lowest one, letting the pair float for a day. As soon as they were disconnected, the suspect one still showed a slightly lower voltage, and now a week later it's back to 0.04V lower again. Temperature is around 25 degrees C.

The actual reading is 6.33V, although I am aware cheap multimeters may not be accurate. The SG reads 1.280-1.285 compared to around 1.300 for the others. Both these readings seem fine according to Trojan's User Guide, and the variance is well under their 0.3V guideline for equalizing.

But their table also shows this one battery is 5% less charged than the others. Won't this tend to drag the others down to its level when they are connected together?

They were all fresh from the distributor, and stamped with the same dates. I don't yet have the equipment to equalize (to be installed in 2-3 months), otherwise I would do so, but should I have to for new batteries anyway?

Opinions?
Hello,

Maybe the best way to connect them (not suggesting you haven't) as in this link, very informative.

SmartGauge Electronics - Interconnecting multiple batteries to form one larger bank
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Old 07-02-2014, 00:34   #7
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Re: Acceptable variance in new batteries

Thanks Angelssson, there is some good info in that link.

I knew to avoid the lazy battery syndrome, but was not aware how much difference it would make. A pity the professional who had been working on the boat for the previous owner did not read it. It had 5 x 12V batteries, and power was being taken from 4 separate points in the circuit.

The heaviest usage was shared by #1 and #2 (left in the photo), so battery #5 was well downstream from them.

Click image for larger version

Name:	Battery connections.jpg
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ID:	75449

My new system is not yet installed, but I plan to follow the Trojan guide which is essentially Method 2 in your link, modified for pairs of 6V batteries. There are so many cables in the area I need to keep it as simple as possible.
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Old 07-02-2014, 07:43   #8
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Re: Acceptable variance in new batteries

Quote:
Originally Posted by Wanderlust View Post
Thanks Angelssson, there is some good info in that link.

I knew to avoid the lazy battery syndrome, but was not aware how much difference it would make. A pity the professional who had been working on the boat for the previous owner did not read it. It had 5 x 12V batteries, and power was being taken from 4 separate points in the circuit.

The heaviest usage was shared by #1 and #2 (left in the photo), so battery #5 was well downstream from them.

Attachment 75449

My new system is not yet installed, but I plan to follow the Trojan guide which is essentially Method 2 in your link, modified for pairs of 6V batteries. There are so many cables in the area I need to keep it as simple as possible.
I had no idea about the alternatives, previous to finding that information, it is invaluable with a multi-battery set up, and simple to add if required.

Also like this article about the lead acid comparisons:
Sterling Power Products: What is the best battery to use for an auxiliary charging system?

Good luck
Mike
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