Charging batteries

Submitted: Saturday, Jul 27, 2013 at 11:02
ThreadID: 103426 Views:1315 Replies:2 FollowUps:6
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Hi all,when charging batteries wired in parallel in camper is it better to connect charger to one battery or over both,same question with powering appliances draw from one or across both,cheers
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Reply By: pop2jocem - Saturday, Jul 27, 2013 at 11:11

Saturday, Jul 27, 2013 at 11:11
To my understanding ideally connect to the positive of one and the negative of the other. As most parallel battery setups have both batteries sited close together and the cables joining them are short and are of sufficient diameter in practical terms the advantage is minimal.

Cheers
Pop
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Follow Up By: Member - Frank P (NSW) - Saturday, Jul 27, 2013 at 17:02

Saturday, Jul 27, 2013 at 17:02
X 2, Pop.

Here's an interesting read for anyone who wants more info.
FrankP

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Follow Up By: Dennis Ellery - Saturday, Jul 27, 2013 at 18:03

Saturday, Jul 27, 2013 at 18:03
Starter batteries in parallel should be wired this way also – the difference in this case is substantial and the if not done, the first battery works a lot harder.
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Follow Up By: Stu & "Bob" - Saturday, Jul 27, 2013 at 22:18

Saturday, Jul 27, 2013 at 22:18
I was of the understanding that if one was to connect the positive of one battery to the negative of the other, then they would be in series, and, if 12 volt batteries, then would be 24 volts.

Ok if they are 6 volt batteries.......
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Follow Up By: DiscoTourer - Sunday, Jul 28, 2013 at 01:34

Sunday, Jul 28, 2013 at 01:34
Stu & "Bob",

What you state is correct if you are joining two batteries together......but you may have misunderstood the thread.

The batteries are already in parallel, and the OP and others are talking about the best way to charge these. By placing the positive charging lead to the postive terminal on one battery, and the negative charging lead to the negative terminal on the other, still keeps the two batteries in parallel, and just treating them as one bigger battery for charging purposes....and 12 volt.

Brett.....
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Follow Up By: olcoolone - Sunday, Jul 28, 2013 at 09:14

Sunday, Jul 28, 2013 at 09:14
In theory (negative from on battery and positive from the other) this is a good idea but in real life situations in automotive it makes bugger all difference as long as appropriate cabling has been used. In OEM applications where dual batteries are used some vehicles have it and others don't..... it is more of a convenience thing for cabling.

One downfall of this is if one battery has a bad cell; the other battery will not charge correctly.



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Reply By: Sand Man (SA) - Saturday, Jul 27, 2013 at 13:24

Saturday, Jul 27, 2013 at 13:24
Rarely do you get the opportunity, let alone the need to charge multiple batteries in this way.

Consider your average dual battery installation in a vehicle.
The alternator is connected to the primary battery and the auxiliary battery is connected to the primary battery terminals, + to +, - to -.
Therefore all charging is applied to the primary battery and usually an isolator manages the charging connection to the auxiliary, once the primary battery has reached a minimum voltage level.

Similarly, in a camper with multiple batteries, the batteries are connected in parallel and it doesn't matter if a charger, (whatever it may be) is connected to one battery, the other in the circuit will benefit the same, as any charging current will be applied equally to both batteries. It is always good practice to ensure an intelligent isolator is included in the circuit with any auxiliary batteries to protect to primary (starting) battery from accidental discharge.

In my setup, the auxiliary battery in the rear tub of the vehicle is charged by the alternator, managed by an isolator between the two batteries.
When the camper is connected up, the two batteries in it receives their charging current via connection to the auxiliary battery. To all intents and purposes, I then have three auxiliary batteries connected in parallel, which all receive input from the alternator equally.

To ensure an adequate charging voltage and current, the two batteries in the camper are managed by a dc-dc charger in the circuit, to ensure any voltage drop in the long cable run is eliminated.
This dc-dc charger also includes a solar terminal input, to apply a charging source when the vehicle is not connected. This dc-dc
The camper also includes a separate "built-in" AC charger, which is automatically applied when the camper is connected to a 240AC supply.
This charger is also connected to the left side battery and only the two linking cables connect the right side battery to the "battery bank".
Generally, I don't set up camp in caravan parks, so I rarely connect 240v to the camper, except on occasions at home to maintain a "maintenance" charge to the camper batteries.

When two (or more) batteries are connected in parallel, the main thing to consider, is that a fault in one battery (eg dropped cell) will drag the other battery down. This is why is is often mentioned that both batteries be of similar age and construction to limit such a situation from occurring.

Bill


I'm diagonally parked in a parallel Universe!

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Follow Up By: Corrugate75 - Sunday, Jul 28, 2013 at 07:42

Sunday, Jul 28, 2013 at 07:42
G'day Bill,

Just on your comment "Rarely do you get the opportunity, let alone the need to charge multiple batteries in this way."

While I acknowledge this is rare for most urbanites, most tractors, trucks, and other larger engined farm machines that require more CCA than one battery can produce, have two (or more) batteries wired in parallel.

When charging with a smart charger I always connect to the positive of one battery and the negative of the other.

Cheers
Corrugate
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