Auxbattery charging

[crzr]

Hi,
I am getting ready to wire the aux battery in my slide-in camper to the truck charging system for charging when on the go. Plan on using a continuous duty solenoid to protect the primary battery, which is standard automotive issue. The aux battery is deep cycle. Recently I heard that batteries of different types should not share the same charging system as this will keep one of them from getting fully charged. Should I scrap my plan?
thanks!

 

[Doctor W]

That is correct!MUST be same size and type for best purposes.

E.g. a 120AH serviceable (able to open top, type) in the truck and same in camper....OK in truck but problematic in camper, e.g. too small a capacity???? and gives off dangerous gases in camper

Best solution is to use (say)100 or 120 AH AGM type in truck and another one or two same sized AGM in camper.......this should give plenty of reserve power for truck and camper, depending on personal requirements.

There are some new and rather pricy units that can get around the disimilarity but at a high price and some inefficiency while they do it.

 

[dwh]

Recently I heard that batteries of different types should not share the same charging system as this will keep one of them from getting fully charged.

Not correct.

Different size/type/age batteries should never be rigged as a *permanent battery bank*.

For charging from a normal vehicle charging system, it doesn't matter. All that matters is that both batteries specify roughly the same charge voltage. Since 99.9% of all flooded and agm, cranking and deep cycle specify roughly the same charging voltage, it's perfectly acceptable to tie them together *while charging*.

In other words, your cranking battery probably specs 14.4v max charge, and your deep cycle probably specs the same (unless it's a GEL...never mix gels with anything but another gel). Since your truck's alternator/voltage regulator probably holds the system voltage to somewhere between 13.5v and 14.2v, it will...eventually...with enough driving time...get both of those batteries almost up to 90%-95% full.

It won't take long for both batteries to reach a surface charge of whatever the voltage regulator is set at - say 14.2v. Once they both get there, the regulator will hold the "bus voltage" at that voltage (more or less), and each battery will slowly trickle absorb however much it can until it's more or less full. The cranking battery won't need much and won't take long, but the deep cycle might take quite a while (10 hours or more) to finally get done absorbing.

Just make sure that they are not tied together UNLESS they are being charged and you have no issues.

 

[crzr]

Right. No gel cells involved.

The solenoid should keep them separate except when the truck ignition is on, when they will be charging.

Thanks for the detailed reply.