Home |
Search |
Today's Posts |
#3
|
|||
|
|||
It's another question on batteries & wiring circuits
"Larry" wrote
There is not a reliable way to charge the batteries together without using a battery isolator. Batteries ALWAYS charge at different rates and an isolator will allow for this. Bunk. Multibank battery systems were on boats for decades prior to the marketing of "combiners", "isolators" and other solutions to the "forgot to switch from Both to House after engine shutdown problem." Paralleled banks of differing charge states will charge just fine when hooked up to an alternator. The banks will automatically charge at different rates until all banks are fully charged, without additional devices. Consider the 2 bank worst case scenario, a fully charged bank at 12.7v resting voltage and a dead flat bank @ 10.5v. When the alternator kicks in the system voltage jumps to 12.5v or so depending on bank capacity and alternator output. The charged bank is essentially at system voltage already and accepts little to no current, while the discharged bank sees a 2v differential and accepts all the current the alternator can deliver. The charged bank will not accept charge until the voltage of the discharged bank rises to the resting voltage of the charged bank, then, as the system voltage further rises, both batteries charge until the system voltage is around 14.4v. The charged bank accepts about 2% of its capacity because it's already charged (its highest charge rate during this engine run, so it's not even warm), and the discharged bank slowly accepts less charge until its charge rate is 2% of capacity. Both batteries are (nearly) fully charged. Some caveats here. The banks must be electrically similar, mixing GelGell batteries with regular flooded lead acid batteries is a no-no, for example. If the banks differ in capacity, the alternator must be no larger than 30% (GelCell, etc. 50% or even higher) of the smaller bank's capacity, to prevent damage from too high of a charge rate as the smaller bank sucks up the current. And, the cabling system must be properly sized, so all banks see the same voltage; a windlass battery in the bow with too small wiring will show system voltage when no charging devices are on line, but a half volt or more drop when the alternator's pumping 70 amps through it to the discharged battery. |
Thread Tools | Search this Thread |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Forum | |||
Buying Boat Batteries - Check My Thinking | General | |||
Wiring Confusion... Help! | General | |||
Cheap AGM Batteries in Charlotte NC | General | |||
Batteries and baby bottles | General | |||
New owner - Question about AC power | General |