Smaller Ah vs Bigger Ah banks

westbranchwestbranch Solar Expert Posts: 5,183 ✭✭✭✭
I am in the process of looking for a replacement for my older 12 V 1055 Ah AGM battery.

I will be upgrading (yes Mike) to at least 24 V or possibly 48 V, choice is partially dependent on the ability to 'place' several arrays, size will be limited due to high wind loads. With the MX 60 limits, array planned to be ~ 1320 W - 1440W

I am reeling the numbers through my head whether to stay with a similar sized bank or possibly go to a smaller bank with ~ 600 AH cells. Vendor has Enersys DDm 48 V banks for sale.

Loads are forecast to be in 6 Kw h when we get the place finished. About a 20% DoD daily so 3 day = +- 60% .
Likely will be boosting with the genny in winter due to minimal winter (max 4) sunlight hours.

I know that Icarus has that rule of thumb about 'Loads will always grow!' and that he lives well with a tiny bank... and C'Coot is in the same situation.

Looking for opinions as to benefits & disadvantages of using a smaller Ah bank.

KID #51B  4s 140W to 24V 900Ah C&D AGM
CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
Cotek ST1500W 24V Inverter,OmniCharge 3024,
2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
West Chilcotin, BC, Canada


  • PhotowhitPhotowhit Solar Expert Posts: 5,998 ✭✭✭✭✭
    Re: Smaller Ah vs Bigger Ah banks

    24V with 600 Amp cells will be slightly larger bank than you 12V Bank.

    Advantages of a smaller bank tend to be cheaper up front costs with a shorter life span, possibly needing to cut back in times of poor exposure. Larger bank, less need to watch your system capacity and often longer battery life.

    Larger battery banks also come with higher liability if mistakes are made, I will normally suggest a small/cheap bank for new systems. Likely you have a good handle on your needs vs capacity through out the year.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former, 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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