Charging AGM with Lead Acid.

[123rover50]

I have two batteries in the camper.
A lead acid for starting and a AGM or gel deep cycle for house.
Normally the latter is on charge via solar but not much sun lately.
Now they are connected via a rotary switch as Bat 1 is start, Bat2 is AGM and" both."
Is it OK to use" both" to charge the AGM and the LA together or should I switch to Pos 2 after starting and charge the AGM on its own via the alternator?

[harro]

Flooded lead acid for starting and AGM (which is still a lead acid battery) is a very common setup and there is no issue that I know of with charging both together via the alternator.

I wouldn't be bypassing the start battery you may get a nasty surprise when you go to start the vehicle again.


Paul.

[weeds]

The first defer I brought had an idiot switch fitted......I asked the previous owner why he called it the idiot switch, he said you feel like an idiot when you forget to change back to both before you drive all day.

No issues if you selected both for either stationary or driving

I’d have mine on both while driving than isolate the start overnight or when I pulled up, solar was also fitted.

[drivesafe]

Hi 123rover50, when charging from your alternator, there is no special requirements, just connect all the batteries, regardless of type, in parallel and your alternator will charge them without any issues arising.


BUT!


When charging with a battery charger, you can still charge all the batteries at the same time, as long as you set the MAXIMUM charge voltage no higher than the battery with the lowest MAXIMUM tolerable voltage.


In your case, the Wet Cell, this is the battery you have referred to as your “lead Acid” battery, can tolerate voltages as high as 15.5v FOR SHORT PERIODS, but is happy at 14.7v


Your AGM, if it is no more than about 5 years old, will also tolerate 14.7v as a continuous charge voltage, but must NOT be charged with any voltage above 14.7v


So set your charger to make sure it never operates above 14.7v and all will e fine.

[DeanoH]

Your typical Gel battery has a recommended charging voltage of around 14.3 to 14.5 volts. Your typical AGM battery has a recommended charging voltage of around 14.4 to 14.8 volts. The Gel battery isn't as tolerant of higher voltage as the AGM so it's important to know which you have. I wouldn't be charging a gel battery at 14.8 volts.

General charging information for AGM and GEL batteries | Discover Battery (https://discoverbattery.com/EN/battery-101/general-charging-information-for-agm-and-gel-batteries/)

I wouldn't be concerned about coupling a flooded cell and AGM battery together.

Deano :)

[123rover50]

Thanks all for your prompt replies.
Thats everything I need to know.
Much obliged.