There are several ways to wire multiple batteries to achieve the correct battery voltage or capacity for a particular DC installation. Wiring multiple batteries together as one big bank, rather than having individual banks makes them more efficiente and ensures maximum service life. The batteries can be connected in series, in parallel and/or series/parallel, depending of the needs. Wiring batteries together in series will increase the voltage while keeping the amp hour capacity the same. An example will be to connect in series two batteries of 12v each with a 150Ah, giving as a result a 24v system but with the same 150Ah capacity. Wiring the batteries together in parallel has the effect of doublight the capacity, while keeping the same voltage. An example will be to connect in parallel two batteries of 12v each with a 150Ah, giving as a result a 12v system but with a 300Ah capacity. Wiring batteries together in series/parallel will combinate the above systems, achieving both higher voltage and higher capacity.
Battery testing schedule
Batteries must be tested in a regular base. By doing it so, you will be sure that your batteries will keep a good state of health and charge, SBS recommends to perform the following battery testing schedule.
You will find the battery testing schedule and down load it at annexes
Proper cable in an installation is primarily a matter of sizing a cable to match its task.
The table shows you the proper size of the cable according to the length, the current load and the circuit type; Non Critical & Critical.
The Non Critical is based on a 10% voltage loss and the Critical is based on a 3% voltage loss. What this means is that when the circuit is fully loaded, the voltage at the receptor or appliance will be 3% or 10% below that at the battery. For example, if the battery is at 12,6volts, the receptor or appliance will be seeing 12,2 volts (3%loss) or 11,34 volts (10% loss).
Many receptors will run fine with a 10% voltage loss, but other are particularly sensitive to such losses, so they will have to work below 3% volts losses. It is better to use the 3% volt drop, rather than the 10%.
The cable length is total length of the positive and negative wires, so you need to multiplied the length from the battery to the receptor or appliance by 2. The negative cable as as much a part of a circuit as the positive cable, so its must be sized the same.
Opinion Article "Baterías del barco, las grandes olvidadas a bordo"
Click at the image to read the opinion article write by Javier Saenz - MARINE BATTERY SERVICE CEO. Only in Spanish version.