House vs starting batteries

[CountingFireflies]

We have 2 large batteries servicing the house, and 2 similar sized ones for starting operating functions.   I'm starting to desire more house storage, as we currently can only last 3 days without a recharge.   

So here are my questions: 
Can I simply add more batteries in parallel with the current houses batteries, and does the charger do ok with more cells?

Can I tie the house to the starting batteries?  And again,  will the alternator service more cells?

[Busted Knuckle]

I'm just gonna say that in theory yes. But to be honest even ourr electrical guru's are gonna want more info before touching on that!

And also when boondocking it is not good to have the house/start batteries connected as you could end up with all of them too low to start ya back up!

  BK 

[thomasinnv]

what kinda bus? 12 or 24 volt system? (the chassis and house systems) how old are your house batteries? You generally don't want to add new batteries with old ones, the old ones will draw down the new ones to their level. General rule of thumb is if you add more batteries they need to be the same type and amp hour rating, and no more than a year old. JMW.

[bevans6]

What BK said...

Knowing what batteries you have, what charger and what alternator will help a lot.  If you have a generator with autostart that is reliable and actually starts every time...

Many things, in fact a lot of boats, don't have separate battery banks.  They use the same  batteries to start and to run everything in the house.  You may be compromising battery design if you use deep cycle batteries for starting, and vice versa.  My own setup bridges the house and start batteries when running for charging and use of the inverter to run the AC unit.  When stopped I un-bridge them so I don't draw down the starts.  I use the same little 5 amp/24 volt charger for both.  It doesn't really do a good job, but it works - just takes a long time.  And I don't have an auto-start generator.  It's nice to remember that you can bridge the starts and house when doing a really cold start, for example.

Bottom line, many do what you are contemplating quite happily.  I have 230 amp/hours at 24 volts of house, in 4 6 volt deep cycle units, and about the same in starts in the form of 2 8D's.  I have the 50DN alternator and the aforementioned 5 amp charger...  My usage takes those constraints into consideration and I have never had any issue with storage or starting...(that was battery related.  Wore out old engine that was hard to start, yes...)

Brian

[gus]

Any reasonably powerful charger will charge a bank of 2-4 batteries, it may just take a bit longer if the batts are large.

What I often do if my house batts (2 GP 29) get a bit low is connect them with the start batts for an hour or so to give them a small boost. Since my engine starts on the first turn and my starts are much larger than the house batts this is never a problem. Others may get different results!

Also, my simple house system does not require a lot of power. No TV, no sound systems and no inverter. We also don't dry camp very much, we are travelers, not campers.