2 Different Capacity Battery Banks Connected to 1 Inverter

[Carl]

Was wondering how to go about connecting up 2 battery banks of different Ahr capacity to a single Inverter.

 

Bank 1: Eight Flooded Lead Acid, US 240 Ahr, 6 Volt batteries connected in series to make up 48 Volts.

 

Bank 2: Eight Sealed Optima 55 Ahr, 12 Volt batteries connected 4 in series and 2 strings in parallel to make up 48 Volts.

 

Any suggestions would be appreciated.

[Haggers]

Hi, bank 1 not sufficient?

[Carl]

Bank 1 has been around the golf course about 600 times, so not in great condition, but still has a bit of life left over.

 

Bank 2 is 5 years old, but has been on float charge for most of that time, and seems to be in a great condition.

[Wetkit]

Hi Carl,

 

Mixing the diffrent battery types and sizes is not really recomended, due to the diffrent voltages required to charge them correctly.

You either going to over charge the sealed gel battries, or under charge the lead acid units.

 

If it was me, I would service the lead acid units. Even at 50% they still 120Ah. The gel battries is 110AH at 100%.

Make sure you charge each bank correctly and then discharge them using the same load.

See what the volt drop is in 1 hour and from there you should be able to work out which bank have the most life remaining.

[Carl]

Thanks Wetkit, will do a full charge / discharge cycle on each battery bank and see what the capacity is.

 

Am running my system for maximum solar consumption and only topping up the batteries from Utility in the evening for about 2 hours. This is working ok except on those overcast days when the battery does not recharge from solar and then we have load shedding. Have had to do some serious explaining.

 

Am using the old US battery at the moment but was thinking of an automatic switchover to the Optima battery bank when the US batteries are flat and no Utility power is available.

[Haggers]

Carl you could install a switch over between the battery banks?