Using different size battery banks

toppinish

Before purchasing additional batteries and solar panels, I'm trying to decide upon a method to integrate two different size and age battery banks.

Old battery bank: 3 x RV/Marine batteries ~330 Ah total
New battery bank: 4 x (Rolls, 6 volt) 215 Ah ea. -  856 Ah total

Solar charger: Tristar 45

My current small solar system supplies DC for lighting and other electronics. I'm trying to integrate additional solar panels, batteries and a DC to AC inverter for AC loads.

It was several years ago I remember reading about isolators designed to isolate two different banks while sensing their voltage and maintaining a balanced charge for both banks.  However, I don't know if the charge controller would work as efficiently (over a long period of time) trying to maintain two different sized banks as it's algorithms and programming senses two different size banks are one large battery bank.

I was thinking perhaps a better solution would be to create two separate solar systems, using separate charge controllers, solar panels and battery banks. The larger system connected to an inverter would  supply AC. Both systems could then be  connected to the existing DC  using diodes or isolators with diodes.

What other methods and solutions are used to integrate two different size and type of battery banks?
 

e12do

Unless you are a 6 volt system your AH total is wrong.

Photowhit

Amps are NOT a measure of stored power, but a measure of potential current.

Watts are a measure of power. 330 amps at a presumed 12 volts would be (12 x 330) 3960 watts and 4 - 6volt at 215 amps would be (4x6x215) 5160 watts...

If the marine batteries have any age to them, I would just remove them from the system. Typically they do not have a very long life in deep cycle uses.

toppinish

If you read my comment it shows - "Rolls, 6 volt" deep cycle batteries.
___

I think you're confusing amperes with amp hours.

My comment addresses  combining two different type, size and age battery banks, battery maintenance and not other factors and details such as system wattage.  Essentially problems with charging efficiency and maintenance. One of my four stage AC chargers is able to maintain two battery banks. I haven't yet found a similar method for the Tristar solar charger. I think my only option is to use a second solar charger connected to separate solar array?

Ah (amp hour) is the amount of energy charge in a battery (measurement of stored energy) that allows one ampere of current to flow for one hour. Battery Ah specifications are a potential maximum energy a battery or battery bank is able to store.

An ampere (amp) is a unit of measurement for the rate of electron flow in an electrical conductor.

Yes, the marine batteries will eventually need to be replaced, have at least a few years of use left. Replacing will create a new second battery bank with a different age and potentially another battery type and size.  When connected to a good charger with periodic maintenance marine batteries will last a good while but not nearly as long as a deep cycle which potentially can last 15 to 20 years.  



  

vtmaps

toppinish said:

New battery bank: 4 x (Rolls, 6 volt) 215 Ah ea. -  856 Ah total

Those four batteries can be configured 4 in parallel to make a 6 volt, 860 ah bank.
or
Those four batteries can be configured in series/parallel to make a 12 volt, 430 ah bank.
or
Those four batteries can be configured 4 in series to make a 24 volt, 215 ah bank.

I agree with Photowhit... I wouldn't spend money buying equipment just so you can use the RV/Marine batteries.   If you feel compelled to use them, your plan to buy a second controller and array sounds like the best option. 

Just to point out... two controllers will require two solar arrays.... two controllers cannot share an array.  After the marine/RV batteries die (sooner than you think) you can use their controller and array to help charge your Rolls deep cycle bank.

--vtMaps

zoneblue

Just as a note to newcomers, its good if you can provide more rather than less detail about your system. Otherwise we get into these i think the OP has XYZ, is trying to say ABC  scenarios.  We almost always need more info to answer questions like this. And if you think you might hang around a a bit, go ahead and add a signature to your posts outlining the system specs.  The missing peice of info here is the system voltage, and vt correctly outlines the configuration permutations for those rolls cells.

toppinish

I'm still in the planning stages to modify and upgrade my current system. Details of my existing solar is noted in previous messages. 

Mainly looking for other configurations and equipment people have used to connect two different size battery banks.