Connection wire has resistance. The gauge of wire and the connection resistance determine connectivity resistance, and therefore voltage drop in between batteries, and also between batteries and any external power source. (when charging currents are actually present)
You can just hook everything up and trust to luck. However, the farthest battery will not achieve the same potential of the nearest battery if any charging currents are involved.
Further, unless the electrolyte in each battery had the exact same acidity, and the plate surface area in each battery is identical. The weakener batteries will be overcharged by the stronger batteries that will never reach their peak power potential. This is bad for both batteries.
Further, there are hundreds, if not thousands of battery charger, tender, and trickle type designs out there, even within brand specific offerings.
Stating a brand as a reference to charge/maintain a battery is like saying the best way to get to work is by using a Honda. (Leaving the question open as to whether it was a car, Cub, or Blackbird.)
The point is:
You have to examine and monitor the output of any charger you select (or know it's published output specs., in order to predict what kind of job it will do under the intended conditions.
>>>Another strong warning about battery maintainers for those using them year round, is to have one that adapts to the ambient temperature.<<<
Batteries use chemical action to convert electrical energy. The temperature of these chemicals affects their activity level. A cold battery will have a lower voltage level than a warm battery, even if both are fully charged! In fact, the batteries' capacity is changed with temperature.
If your charger/maintainer does not compensate for the varying voltage levels of the battery/per temperature, then under what conditions does the charger design expect the battery to be in, hot or cold or "average"? Such Battery chargers may overcharge a cold battery, and undercharge a hot battery.
Is your battery charger/tender optimized for cold winter months, or summer heat? If it doesn't compensate for temp, then YOU have to monitor the electrolyte specific gravity, to know if the battery is at peak charge and if you should disconnect the power source.
Here's a chart using 80F for the norm, and includes voltage:
PERCENTAGE OF CHARGE / SPECIFIC GRAVITY CORRECTED TO 80ºF / OPEN-CIRCUIT VOLTAGE 12 VOLT
100/ 1.277 / 12.73
90 / 1.258 / 12.62
80 / 1.238 / 12.50
70 / 1.217 / 12.37
60 / 1.195 / 12.24
50 / 1.172 / 12.10
40 / 1.148 / 11.96
30 / 1.124 / 11.81
20 / 1.098 / 11.66
10 / 1.073 / 11.51
(State of charge as related to specific gravity and open-circuit voltage)
Correcting the readings to 80ºF
• Add .028/cell for every 10º above 80ºF.
• Subtract .028/cell for every 10º below 80ºF.
Doing the math. If your charger is optimized for 80F, it thinks a fully charged battery is 12.73 V and should maintain it at that voltage.
If the real temp is 30F, then the specific gravity (fully charged) would be .125 lower or an SG of 1.102, which is about 11.7V.
If your charger has not been "taught" about temperature effects in batteries, it will try to bring that low voltage up 12.7V and over-charge the battery. Then, depending on the strength or aggressiveness of the charger to bring that voltage up, it do damage to the battery, by making it lose electrolyte level, and cause the plates to shed metal flakes that collect on the bottom of the battery, shortening it's life.
Simple, eh?
Cheers,
