Battery charging, quick question

[orbital]

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I was looking to save on not buying another charger, so I made this setup.
Just using one Battery Tender
(Both deep cells were fully charged & up to voltage before I connected this way)

Is this setup OK??
if not, don't laugh ~ I was tryin' to save a couple bucks...:)

thanks~

 

[Bullzeyebill]

What are the black wires connected to? Please present more detail here.

Bill

 

[Shadowww]

They're going to Battery Tender, judging by his post.

To OP: connecting lead-acid batteries in parallel is perfectly fine, don't worry about it :)

 

[orbital]

What are the black wires connected to? Please present more detail here.

Bill

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To the Battery Tender charger (both pos. & neg),, I know its a bit hard to see.

They're going to Battery Tender, judging by his post.

To OP: connecting lead-acid batteries in parallel is perfectly fine, don't worry about it :)

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Thanks :thumbsup:
really couldn't figure out a reason why this wouldn't work,, I kinda winged it.
One question~ Is there a specific connecting/disconnecting sequence I should do??


also, those deep cells are exactly the same units..

 

[gearhead1972]

the setup is fine, but they are going to take an awfully long time to charge especially if they are drained down far.

 

[blgentry]

Just using one Battery Tender
(Both deep cells were fully charged & up to voltage before I connected this way)

Because your batteries are identical *and* fully charged, this setup is probably ok. HOWEVER, I've had a bad experience with charging lead acid batteries of difference sizes in parallel. The series resistance between the batteries can become an issue. The resistance of the cables connecting the batteries together can make one battery charge less than the other, thus way over charging one battery and under charging the other.

Your setup is not typical, as you have two equal length leads going to each positive and negative terminal of each battery. It's probably fine, but to be safe, I'd connect it like Deltran (Battery Tender manufacturer) recommends. Their way "balances" the charge so neither gets over charged. This FAQ answer shows the recommended way.

Brian.

 

[shadowjk]

Different batteries have different float voltage specification too, that'd cause a problem. Once the batteries have sat at the float voltage for awhile, I'd think that the internal resistance and wire resistance becomes less meaningful, as the current approaches zero the voltage drops do too?

 

[Shadowww]

Different batteries have different float voltage specification too, that'd cause a problem.

Judging by pic he has completely same batteries, so that shouldn't be a problem. :)

 

[blgentry]

Different batteries have different float voltage specification too, that'd cause a problem.

As far as I know all 12VDC lead acid batteries work with the same "float" voltage of 13.8V produced by the BatteryTender products.

Once the batteries have sat at the float voltage for awhile, I'd think that the internal resistance and wire resistance becomes less meaningful, as the current approaches zero the voltage drops do too?

You're right about the current dropping to nearly zero. The problem with the series resistance shows up (as far as I know) when the charger is at the "head end", directly connected to one battery, and you have another battery in parallel with wires connecting the two. In that case, the charger can get confused and NEVER get into float mode. Instead it keeps trying to charge both batteries long past when the first one is already fully charged.

I'm no expert on this. I just had a bad experience and learned that my wiring was the problem, and that this balanced configuration is supposed to prevent over or under charging from happening.

Brian.

 

[shadowjk]

Yuasa specifications have a graph which suggest a float voltage of 13.8V reduces battery lifetime by 20%, compared to the 13.65 recommended. CT Leader recommends 13.62V, but doesn't provide any lifetime estimates at other voltages. APC Back-UPS products maintain 13.5Volt float charge for their batteries.

I don't really use the "fast" chargers, because the whole charge algorithm seems weird to me, and missed termination / transition to float have in the past cooked batteries for me.