Originally Posted by Calliedo02
1. Does the Battery Tender draw some current from the battery it is charging if it loses its 110 v. power source, thereby eventually draining it ?
2. Assuming both 6 volt batteries are good, what issues, if any, are associated with charging them with one Battery Tender when they are connected in series?
Here is "Battery Tender's answer's to your question's Chuck:
What happens if the AC power is removed from the Battery Tender Plus battery charger while it is connected to a fully charged battery?
If the battery is fully charged, then the Battery Tender Plus battery charger’s green light will be on. Once the AC power is removed from the Battery Tender Plus battery charger, the green light will go out and the charger not have any effect on the battery
. The Battery Tender Plus battery charger is protected from reverse current, so it will not discharge the battery
. Of course, like we said earlier when discussing nominal voltage mismatches between a battery and a charger, the battery will not be recharged either.
When AC power is restored to the Battery Tender Plus battery charger, it will restart its charge cycle. The sequence of events should go something like this. The red light will come on for a few minutes. Then the green light will start flashing while the red light stays on. The next thing that happens is what may confuse some people who use the Battery Tender Plus battery charger. Remember, the battery was fully charged, so you may ask, “Why doesn’t the green light just come right back on?”
The reason that the green light doesn’t come on immediately is that when the charger first comes on, the battery is sitting there, fully charged, at a voltage of about 12.9 volts. The charger immediately tries to bring the battery voltage up to about 14.5 volts. This takes a finite amount of time, although it should only be a few minutes if the battery is fully charged. Then, when the battery reaches 14.5 volts, the charger will hold it there until one of two things happen. Either the battery charge current will drop to less than 0.1 amp (from an initial value of 1.25 amps) or, if the current does not drop below 0.1 amp, then the charger will hold the battery voltage at 14.5 volts for 6 to 8 hours.
There are a couple of reasons why the battery current may not drop below 0.1 amp. First, on a larger battery, like an automotive SLI battery, the internal losses of the battery may consume more than 0.1 amp. Second, if the vehicle or the system that the battery is connected to has appliances that consume electricity, then that consumption of electricity, coupled with the battery internal losses may very likely exceed the 0.1 amp limit. This second cause is very common and its result is that the Battery Tender Plus battery charger’s timer circuits will be fully engaged. So it will take 6 to 8 hours for the green light to come on. Fortunately, the Battery Tender Plus has the ability to continue to supply its full current even after it has switched over to the lower, float, maintenance charge voltage of 13.2 volts. When the charger turns the green light back on, it also drops its output voltage to this float, maintenance charge level of 13.2 volts.
Note: It only takes a momentary AC power outage to cause the Battery Tender Plus battery charger to reset.
Can the Battery Tender Plus battery charger be used to charge more than 1 battery simultaneously if the batteries are connected in series?
Yes, but series connections have more restrictions than parallel connections. A series connection means that positive post of one battery is electrically connected to the negative post of the next battery, and the positive post of that battery is connected to the negative of the next battery and when all the connections are made, the positive post of the last battery and the negative post of the first battery becomes the connection point for the entire battery pack. The voltage of a series connected battery pack is sum of the voltage of each battery in that pack. So if two 6 volt batteries are connected in series, then the voltage of the battery pack is 12 volts.
There are more restrictions on charging battery packs connected in series than there are for parallel connected battery packs. The nominal battery voltages (i.e. 12V, 8V, 6V, 4V, 2V) must be the same on each battery, and the batteries must be the same lead acid type (flooded, AGM, or Gel Cell). Also the batteries must be close to the same size in terms of amp hour capacity, and they must be close to the same level of discharge. It is also a good idea that the batteries be approximately the same age and that they be in relatively the same general condition.
If all 4 of these conditions are met, and if the total voltage of the pack is 12 volts (or 8 volts, or 6 volts depending upon the BT Plus model), then yes, the Battery Tender® Plus battery charger can be used to charge more than 1 battery simultaneously when those batteries are connected in series. This will not work if the total battery voltage is greater than the voltage of the Battery Tender® Plus (12V, 8V, or 6V).