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Discussion Starter · #1 ·
So both bikes are sleeping for the winter and the batteries are sitting in the basement. I have a battery tender (the small one) and I've been periodically switching which battery gets the charger. My question is this: Can I wire the batteries in parallel and keep the battery tender tending both of them? I'm sure it would "work" but I wonder if one battery gets lower than the other if the other would then overcharge... or would the fact that they were wired together equalize everything...?

Just a thought. One battery is a year old, the other was new this summer, so they are both in good condition. anybody think this idea sucks and I should just go get another charger (or the big battery tender)? or should I try it? :-D
 

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I don't know the answer to that one, but I have just bought a little solar panel on ebay for £10 ( about US$20) which is supposed to keep the battery topped up.

Ever since I bought it about 4 days ago we have had thick fog :)
 

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I cannot say for sure but my guess would be that it would not work as designed.

The Battery Tender has sensing circuitry to measure the amount of charge in the battery and then adjust the rate of charge to suit
With two ot more batteried connected, I cannot see how this would work correctly.

I doubt that it would hurt anything by doing it, so why not just give it a try and see how it works.
Worst case: go back to switching back and forth.
 

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wouldn't hooking-up multiple batteries increase the power and possibly blow the tender? or would it depend on how they are set up?
aren't 2) 1.5 volt batteries putting out 3v when together?
 

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Two batteries in parallel are still the voltage of one. In series the voltage is double. Howerer I still don't think it would be a good idea. I would buy a second unit. The Yuasa one I got from Can. Tire was only $40.00. You could always email the manufacturer.
Better safe than sorry.
 

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On 2006-12-22 19:55, jaben wrote:
Two batteries in parallel are still the voltage of one. In series the voltage is double.
Thanks-I needed that!

Anyone have a drawing comparing series and parallel?
 

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Nice link Cuppa.
Does page 6 of 10 say it is O.K. to use one charger,
as long as one was to use the W1 wire or connect the charger to the + of one battery and the - of the other battery?
John
 

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On 2006-12-23 19:49, jaben wrote:
Nice link Cuppa.
Does page 6 of 10 say it is O.K. to use one charger,
as long as one was to use the W1 wire or connect the charger to the + of one battery and the - of the other battery?
John

Yes it is ok to use one charger with multiple batteries.

On the page you refer to it says "Note the blue wire designated W1. The
purpose of this wire is to balance the voltage drop evenly across both batteries and each
wire during charging. This is not critical for lower current chargers, but when you start to get into the 10 amp and above range, the voltage differential can be significant


So as far as the original question goes, leaving a pair of fully charged 12 volt batteries , (connected in parallel for 12v) connected to a small 12v battery tender will be fine. Use heavy cable to interconnect the batteries. If they are fully charged the tender will be enough to compensate for the battery normal losses.

Hth

Merry Christmas from downunder.
Cuppa
 

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2 questions:

1: Would attaching the tender directly to the + of the near battery and the - of the far battery be the same as having the w1 wire and the other wire from the battery to the tender?? (don't see why not)

2. Would three or even more batteries be the same. ie minus to minus to minus and plus to plus to plus and the tender attached to the plus of battery one and the minus of battery three??

[ This message was edited by: rickj on 2006-12-24 06:22 ]
 

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When working in a boat yard we used to charge multiple batteries off the same charger. The answers are all here across the prior posts.
1. As stated, the batteries should be of the same size and amp hours. (same make is best, not required)
2. Stage your batteries so you can connect the pos terminal of one battery and the negative of the other to the tender.
Thats it.
The reason we use pos of one and neg of the other is so the tender will sense across both batteries, I know that sound crazy when they are in parrallel but it does matter, it truely forces the tender to feel both batteries. This is how we get over the issue that wombat is correct about. If you connect to one and then pass to the other, and one is a better battery it will float the charger before the other has caught up. Or the other way, a weak battery first may cause the tender not to float and over charge the good one. By going oposite corners you are looking at one battery no matter how many you stack. We would charge and maintain banks of 8-10 batteries this way.
 

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Discussion Starter · #15 ·
I haven't had a chance to reply to this thread and thank everyone for their 2 cents.. so thanks!

I think technically this isn't an ideal situation for the batteries, but they are both pretty new and I'm going to go ahead and hook them both up. I often forget to switch the connections and having them both connected at once will probably be more healthy than forgetting about one for 2 months, which I'm prone to do.

thanks again...
 
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