Changing my battery bank from parallel to series

[roykirk]

I hope I don't sound like too much of a dunce with this question, but I'm hoping I might find some answers here. Here's my problem: I've got 70 watts worth of 12 volt panels hooked up to an inexpensive controller that keeps two 12 volt batteries (connected in parallel) charged. The batteries have thus far been used to run a couple backyard things like landscaping lights and a large scale garden railroad. The supply line from the battery that these various loads connect to is 10 gauge solid copper over about 30 - 40 feet (depending on where the particular load connects).

Okay, so up until now this system has worked really well for my needs. Recently, however, I've tried to add on a couple of items that are particularly voltage sensitive and they've refused to run due to voltage drop on the far end on the supply line. Rather than try to run a larger conductor supply line, I've thought about just changing my batteries to series so I've got 24 volts. I thought I'd throw in a dimmer to make sure I can dial back the voltage so things don't get damaged, but at the same time I'd be able to use higher voltage to overcome resistance and to help accommodate the additional loads I'd like to add. Where I get confused is what this means for my 12 volt solar panels. Can they continue to charge two 12 v batteries connected in series, or would doing so mean I'd have to go out and buy new 24 volt panels?

[Sunking]

Simple it is not going to work.

[roykirk]

Well, that was simple. I guess I'm stuck with not adding more items or trying to put in an even bigger conductor that likely isn't going to save a ton on the resistance. Oh well, at least I know what I'm dealing with. Thanks for the advice.

[inetdog]

Well, that was simple. I guess I'm stuck with not adding more items or trying to put in an even bigger conductor that likely isn't going to save a ton on the resistance. Oh well, at least I know what I'm dealing with. Thanks for the advice.

If the non-sensitve items draw (a lot) more power than the sensitive items, instead of making all of the conductors bigger and maybe still getting too large a voltage drop, look at what would happen if you just ran medium size wires from the sensitive item(s) directly back to the battery. That way they voltage drop from the higher current of the other equipment would not affect them.
1. Make sure that the voltage at the battery itself does not drop too low.
2. Find out how much current each sensitive device pulls so that you can figure out the right size for dedicated wires.

[Sunking]

I never said it could not be made to work. My answer was in reference to using a 12 volt battery panel to charge a 24 volt battery.

Well here is the deal, if the one-way distance is 40 feet, 10 AWG wire running maximum safe current of 30 amps would induce a voltage drop of about 3 volts.

Do you have any idea of how much current you are pulling?

First thing that strikes me as odd is you have a 70 watt panel which can only support a very small 12 volt battery of about 50 AH and that size battery can only handle about 7 to 8 amps.

[roykirk]

I never said it could not be made to work. My answer was in reference to using a 12 volt battery panel to charge a 24 volt battery.

Well here is the deal, if the one-way distance is 40 feet, 10 AWG wire running maximum safe current of 30 amps would induce a voltage drop of about 3 volts.

Do you have any idea of how much current you are pulling?

First thing that strikes me as odd is you have a 70 watt panel which can only support a very small 12 volt battery of about 50 AH and that size battery can only handle about 7 to 8 amps.

Sunking - No, unfortunately I do not know how much current I'm pulling. My 70 watt panel actually charges two parallel 50 AH 12 volt batteries. It works pretty well for my purposes, although there are times where it can take a couple of days to charge them up completely. I'm not a heavy user and thus it's been just right as a hobby system for me until recently. I've been thinking and also realized I could connect them in series to get the higher voltage and then throw in a heavy duty switch to disconnect them from each other and charge each battery individually when needed. Sounds like a real hassle, so I'll probably just look at doing direct runs from each load to the batteries.