Connecting 2nd battery in rig.

Submitted: Sunday, Mar 09, 2014 at 00:06
ThreadID: 106616 Views:1564 Replies:2 FollowUps:0
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I am about to connect a second battery in my caravan. The original battery has been tested and has come up within 5% of a new battery in performance and the new battery is identical (except brand) to the old one so i believe that the exercise is worthwhile. Having searched the threads i cannot find the advice need. Do i need to put an inline fuse between the batteries? I have been told from "yes, essential" to "no, for what purpose". Now i am confused!!! If i put in a fuse and it blows the cable would still be live as it is still connected to the other battery. What's your opinion fellow travellers?
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Reply By: Sand Man (SA) - Sunday, Mar 09, 2014 at 09:11

Sunday, Mar 09, 2014 at 09:11
The additional battery will be connected in parallel to the first caravan battery, +ve to +ve and -ve to -ve. There is no need to protect the positive patch lead between the two batteries. Usually the span is short and unlikely to require extra protection from a short circuit.

The positive lead from the vehicle battery should already have a fuse or breaker at the vehicle battery end and an additional fuse at the caravan end, just before connection to the first battery in the "bank" will provide adequate protection from possible short circuits. Any devices connected to the caravan battery bank should ideally be protected individually.

A higher rated fuse can be installed as the "master" fuse on the positive battery bank circuit with lower rated fuses for individual circuits.


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AnswerID: 527947

Reply By: The Bantam - Sunday, Mar 09, 2014 at 10:57

Sunday, Mar 09, 2014 at 10:57
IF you are intending to connect these two batteries in paralell to increase the Amp Hour capacity in the van....that is what you intend?

there is no need and pretty well no point putting a fuse in the link between them.

You need to be very aware, that no matter what you may think, these two batteries are not a pair and they WILL have differences that WILL result in the charging and discharging unevenly....and if you do not supervise and maintain them properly one of them will very likley meet an early death.....and just may take the other with it.

you need to keep an eye on these batteries.
regularly check the individual battery voltages and if they are screw top, the electrolite levels.

It would also be wise to make some arrangement to charge and discharge the batteries independently from time to time

My personal view is that you should connect them using an A-B-Both battery switch.

The only time it is considered reliable and a good idea to connect two batteries permanently together in paralell is if they are the same age, same brand and same capacity...preferably the same batch....identical batteries.

Even then it is considered wise to seperate them from time to time and charge them seperately.

AnswerID: 527959

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