Battery Type Comparison - riplaboratory/Kanaloa GitHub Wiki

Battery Type Comparison

The purpose of this document is to analyze, at a very high level, the price-to-performance characteristics of nickel metal hydride, and lithium ion rechargeable batteries.

There are generally four different classes of rechargeable battery:

  1. Lead Acid
  2. Lithium Ion Li-Ion
  3. Nickel Cadmium (NiCd)
  4. Nickel Metal Hydride (NiMh)

It is generally well understood that NiMh and Li-Ion batteries provide the best performance in energy density, this document will explore the difference between these two technologies.

Note that significant linear approximations were made in these battery calculations.

Battery Calculations

Lead Acid: WestMarine AGM 105

  • Battery Specifications
    • price: $339.99
    • capacity: 105 Ah or 1260 Wh per battery
    • max discharge: 800 A (cold), 1000 A ("marine")
    • mass: 31.3 kg per battery
    • volume: (0.32861m)(0.17145m)(0.23813m) = 0.013416 m^3 ≈ 13416 mL
  • Calculations:
    • $/Wh = (339.99$)/(1260Wh) = $0.26983 per Wh ≈ $0.27 per Wh (lower is better)
    • mass energy density = (1260Wh)/(31.3kg) = 40.256 Wh per kg ≈ 40 Wh per kg (higher is better)
    • volumetric energy density = (1260Wh)/(0.013416m^3) = 93918 Wh per m^3 ≈ 93 kWh per m^3 (higher is better)

NiMh (AA): AmazonBasics AA High-Capacity Rechargable Batteries (8-Pack)

  • Battery Specifications:
    • price: $18.99 ($2.37 per battery)
    • capacity: 2.4 Ah or 2.88 Wh per battery
    • max discharge: 6 A per battery
    • mass: 31 g per battery
    • volume: (0.05m)2pi*(0.007m)^2 = 15.393E-6 m^3 ≈ 15.4 mL
  • Calculations:
    • $/Wh = (2.37$)/(2.88Wh) = $0.82291 per Wh ≈ $0.82 per Wh (lower is better)
    • mass energy density = (2.88Wh)/(0.031kg) = 92.903 Wh per kg ≈ 93 Wh per kg (higher is better)
    • volumetric energy density = (2.88Wh)/(15.393E-6m^3) = 187100 Wh per m^3 ≈ 190 kWh per m^3 (higher is better)

LiPo: Multistar High Capacity 16000mAh 4S 12C Multi-Rotor Lipo Pack w/XT90

  • Battery Specifications
    • price: $142.74 (on sale for $74.94 on 2018.11.11)
    • capacity: 16 Ah or 236.8 Wh
    • max discharge: 12C or 192 A
    • mass: 1290 g
    • volume: (0.173m)(0.074m)(0.045m) = 576.09E-6 m^3 ≈ 576 mL
  • Calculations:
    • $/Wh = (142.74$)/(236.8Wh) = $0.60279 per Wh ≈ $0.60 per Wh (lower is better)
    • mass energy density = (236.8Wh)/(1.290kg) = 183.57 Wh per kg ≈ 180 Wh per kg (higher is better)
    • volumetric energy density = (236.8Wh)/(576.09E-6m^3) = 411050 Wh per m^3 ≈ 410 kWh per m^3 (higher is better)

Li-Ion: Samsung High Drain INR18650-35E 4 Pcs

  • Battery Specifications
    • price: $26.49 ($6.62 per battery)
    • capacity: 3.5 Ah or 12.95 Wh
    • max discharge: 8A
    • mass: 50 g
    • volume: (0.0651m)pi(0.01848m)^2 = 69.845E-6 m^3 ≈ 69.8 mL
  • Calculations:
    • $/Wh = (26.49$)/(12.95Wh) = $2.0455 per Wh ≈ $2.05 per Wh (lower is better)
    • mass energy density = (12.95Wh)/(0.05kg) = 259 Wh per kg ≈ 260 Wh per kg (higher is better)
    • volumetric energy density = (12.95Wh)/(69.845E-6m^3) = 185410 Wh per m^3 ≈ 185 kWh per m^3 (higher is better)

Compiled Results

Battery Type Price/Capacity [$/Wh] Mass Energy Density [Wh/kg] Volumetric Energy Density [kWh/m^3]
(lower is better) (higher is better) (higher is better)
Lead Acid Example 0.27 40 93
NiMh Example 0.82 93 190
LiPo Example 0.60 180 410
Li-Ion Example 2.05 260 185

Realistic Alternatives

NiMh: AmazonBasics AA High-Capacity Rechargable Batteries (8-Pack)

Using a 10 slot holder like this one, we can hold 10 AA batteries in series, giving us effectively a single battery at (1.2V)(10) = 12V nominal. Putting three of these packs in series will then give us a 36V nominal battery; we will refer to three of these 10x AA holders in series as a single "pack". A single "pack" requires 30 AA batteries, and it can deliver around 6A continuous (because all of the batteries in a single pack are in series, it can only deliver the current of a single AA battery. To achieve the 240A required by our WAMV, this then means that we need at least (240A)/(6A) = 40 "packs" total. This requires (40 ["packs"])(30 [batteries/"pack"]) 1200 batteries in total, and will result in a total capacity of 3456 Wh. At a price of $18.99 for 8 batteries, this will cost $2848.50 for all 1200 of the batteries that we will need for a single pack. Factoring in the additional cost for 40 holders ($199), this brings us up to $3047.5

Li-Ion: 18-Volt ONE+ (https://www.homedepot.com/p/Ryobi-18-Volt-ONE-Lithium-Ion-4-0-Ah-LITHIUM-High-Capacity-Battery-2-Pack-P122/204321540)

Some stuff will need to be macgyvered here, but for $99.99, you get two 18V, 4Ah batteries (this is 72 Wh per battery). Wiring two of these in series will deliver 36V, which is ideal for our use case. Given that a 2.0Ah model of this battery exists, this 4.0 Ah model at the same voltage must contain at least a single parallel pair of 18650 batteries, meaning that conservatively, 16A can be pulled out of a single battery. To reach our target current draw of 240A, this will require 240/16 = 15 seies battery pairs, and will have a total capacity of 15272=2160 Wh for $1500. At a $/Wh of ($1485)/(2160)=0.6875, this is signficantly cheaper than buying 18650 cells separately, gives all of the benefits of Li-Ion power with the safety features built into each battery pack, and can be sourced locally.