# Double battery capacity~=double mass?

#### Poor old sod

Joined Jul 25, 2017
142
I have a 40AH deep cycle battery, weighing 18.5kg. 100AH deep cycle battery weighs 40KG.
18.5*2.5=46.25 6.25kg short

Is something seriously wrong?

#### AlbertHall

Joined Jun 4, 2014
11,505
No. The 'error' is pretty small and there will be some economies of scale. Simplistically, two 40Ah batteries will need 4 terminals, one 100Ah battery will need only two. There will also be savings with the case and internal connections and mountings.

#### Poor old sod

Joined Jul 25, 2017
142
No. The 'error' is pretty small and there will be some economies of scale. Simplistically, two 40Ah batteries will need 4 terminals, one 100Ah battery will need only two. There will also be savings with the case and internal connections and mountings.
this is for one only of each battery, just an approx scale up is this error significant. 6kg is a lot of lead plate, and much worse if it's an hybrid..

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#### AlbertHall

Joined Jun 4, 2014
11,505
No.

From Wikipedia:
AAA alkaline cell, 11.5g, 860-1200mAh, average 1030Ah
AA alkaline cell, 23g, 1800-2600mAh, average 2200Ah

AAA has 1030Ah/11.5g = 89.6Ah/g
AA has 2200Ah/23g = 95.7Ah/g