Series battery charging

[wombweller]

Hi

Can I safely trickle charge two 12v batteries (both same) while in series with each other (giving 24v) while the batteries are connected to the load. ?

Also could I leave these on trickle charge permanently again while connected to the load?

Don't want to blow anything

Any diagram to show the charge connections with the example I'm asking ?

Cheers

 

[3lectrokid]

wouldnt one battery slowly charge quicker than the other. i have not much knowledge on the subject

 

[MikeMl]

Is the load 12V or 24V? The only way to properly charge two 12V batteries that have different loads is with two independent 12Vbattery chargers. If the load is 24V (no power taken from the tap between batteries), then a single 24V charger will work.

 

[wombweller]

Is the load 12V or 24V? The only way to properly charge two 12V batteries that have different loads is with two independent 12Vbattery chargers. If the load is 24V (no power taken from the tap between batteries), then a single 24V charger will work.

Hi Mike

The two 12v batteries connected in series have one load of 24v.

So do I connect a 12v charger or a 24v charger, can I leave this trickle charging permanently with the load connected,?

Regards

 

[MikeMl]

You will need a 24V charger unless there are periods when you can turn the load off, during which you use a double-pole relay to switch the batteries from series to parallel, and then charge with a 12V charger only during the non-usage period. No trickle charging that way. If the non-usage period is too short, then the batteries may not recover their charge during the non-usage period.

I would just buy/build a 24V two-state charger like one of these.

 

[MrAl]

Hi,


I always tell people to charge their batteries separately whenever possible,
and if it doesnt look possible then look for another way to do it before you
resort to series charging. This is true with many types of batteries really.

 

[wombweller]

Hi,


I always tell people to charge their batteries separately whenever possible,
and if it doesnt look possible then look for another way to do it before you
resort to series charging. This is true with many types of batteries really.

Hi
Do I charge via the terminals of one battery or one from each?.

Cheers

 

[MrAl]

Hi,


Usually when you charge them separately you ground the two negative
terminals (one from each battery) and also connect the two battery chargers
negative terminals to ground (all negatives connect together), then connect
the positive terminal of one battery charger to the positive terminal of
one battery, and connect the positive terminal of the other battery charger
to the positive terminal of the other battery. Thus each battery has it's
own charger. Note that the two chargers MUST be made specifically for the
type of battery you are working with, and MUST be the correct voltage too,
and also must put out a certain minimum current level.
You can also connect two chargers to two batteries as separate circuits
so that the negatives of the two chargers do not connect together. In this
case each charger connects to one battery.

When you charge in series you connect the negative terminal of the first battery
to the positive terminal of the second battery, then connect the charger
positive terminal to the first battery positive terminal and the charger negative
terminal to the negative terminal of the second battery. Note the charger
has to be made for the type of battery you are using, and the charger also
has to be made for twice the voltage of one battery, and must put out a
certain minimum current level.

A third option is to connect two isolated chargers to two batteries while
they are still connected in series. In this case the chargers have to be
isolated (separate circuits) or a charger built specifically for this reason.
Again one charger connects to one battery, and the other charger connects
to the other battery. One charger's negative ends up being connected to
the other charger's positive, but as long as the chargers are isolated it's
ok to do that.
One way to achieve this would be to buy two chargers (that are isolated
from the line voltage) and connect them to the batteries as if they were
simply each charging their own battery (which they are anyway). The
only difference is we dont disconnect the batteries from the load in this
scenario.

If you also want trickle charging then the chargers have to be able to
put out enough current to power the load as they are charging the
batteries. Switching the load off might be the best idea here unless
it has to run 24/7 in which case sometimes the chargers will be
powering the load.

 

[RCinFLA]

As long as the batteries are same type and age there is no problem using a 26.8 vdc float charge.

The charger should be a three stage charger or a light float charger. Remember that when a load takes significant current the battery voltage will drop below charger float charge voltage. The charger must be okay with this (has current limiter) so it does not overload the charger.