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Posted: Tue Nov 01, 2016 8:25pm

Post Subject: Wiring a battery bank

Hi Tony, I read with interest the recent article on fitting solar panels and was concerned to see that the wires supplying the charge should be attached to opposite ends of the battery bank. Three months ago we had solar panels fitted to a bank of new 3 X 110Ah batteries. I noticed yesterday that the engineer had wired the input from the solar to one end of the bank (i.e. +ve and -ve on the same battery) and the input from the battery charger to the other end along with the +ve output to the 12v system. As it would appear from the article that this will kill the batteries quickly I was going to move one of the solar input wires to the opposite end of the bank, however the engineer has been efficient and cut the wires to just the right length so neither of them will reach. This leaves me with a couple of questions. 1. I'll need to extend the either the +ve or -ve wire on the solar to change the connection so will a terminal block or similar do, will soldering and extension on be preferable or will I have to replace the whole length of wire from the controller? 2. Is it OK to connect the +ve from the solar to the same terminal as the +ve from the battery charger which is also connected to the +ve out to the 12v system? The wiring from the battery charger was also changed at the same time as the solar was fitted so isn't in its original position either. Thanks Regards Trevor Ward NB Secret Hope


Posted: Wed Nov 02, 2016 8:08am

Post Subject: Wiring a battery bank

First of all the batteries will not be killed quickly but they are likely to fail before they would if properly wired. How much sooner depends on things like the loads you put on them etc. so it is not necessary do anything right now but try to rectify the work before next summer. It is fine to connect things as you suggest but if you have an ammeter be aware that the negatives both go to the side of the shunt furthest away from the battery. That is on the same terminal as the main charging and domestic supply cables. The proper thing to do is to run new cables from both the charger and solar controller but as there should be fuses installed in the positive leads close to the battery you can probably solve the issue for one circuit by only renewing the cable between fuse and battery positive. As the new length will not be protected by a fuse please run it in some plastic sleeving or tube. Hose will be OK. Each time you make a connection or add a terminal you will introduce a very small resistance so to do so is not ideal. This is why I say run new cables. Given the choice of some form of terminal block or solder I would use solder BUT, and this is important, soldering needs skill and practice. If you have been trained to slice wires and solder them then that is what I would do on my boat. However I would used adhesive heat shrink over the joint because the soldered portion will be more likely to fail because of vibration so the heat shrink sleeving will strengthen it and transfer much vibration to the cable that is still stranded. In reality you so called engineer should carry out this work or pay for it but I doubt they will. Here is another well respected authority to back up my advice on battery connections - - (all on one line). This is such a fundamental error I would suggest that this person is put on your "do not use again" list.

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