The Blue View - Latest & Greatest Batteries - Part 4

/

battery bank So, after all that, what’s the best battery for our application? Let’s start by comparing the true cost of each battery type over its life.

To recap our assumptions:

  • Recharge cycles: We will need to recharge 200 times a year – from 50% DOD to 80% DOD
  • Recharge cost: It costs us $3.50/hr to run the engine, and the alternator puts out 110 amps at that speed
  • Battery capacity: We have roughly 800 ah in our house battery bank

Since no engineering analysis is complete without at least one spreadsheet…

Actual Cost of Each Battery Type

Battery Type

Initial Cost

Expected Life in Years

$/Year

$/Year Recharging

$/Year Maintenance

Total $/Year
Flooded

$1,080

6

$180

$1,890

$546

$2,238
Gel

$3,180

6

$530

$770

$168

$1,762
Lifeline

$2,650

7

$379

$840

$462

$1,471
TPPL

$2,300

5

$460

$770

$252

$1,566
SpiralWound

$2,230

4

$558

$770

$336

$1,412
CarbonFoam

$3,400

10

$340

$910

$84

$1,334
Lithium Ion

$9,000

10

$900

$700

$84

$1,600

Some surprising results…

  • Given our kind of usage, the flooded lead acid is actually the most expensive, even though it is the least expensive to buy. Obviously, if we weren’t on the hook as much or had a less expensive method of recharging, the results would be totally different.
  • The Lithium-Ion, even though it costs significantly more initially, falls in the middle of the cost range.

Deciding which one…

Starting with the ones I’m ruling out:

  • Flooded lead acid because of the total cost and all the maintenance that’s required
  • Gels because they can’t be equalized and are the heaviest and most expensive of the remaining candidates
  • Spiral Wound because they can’t be equalized, have the least technical information available, and seem to only be available in smaller battery sizes

Of the remaining candidates, all are viable candidates for our application. Here are a few further thoughts:

  • Carbon foam seems the best candidate, but I am somewhat reluctant because of the limited track record – and anyway, they are on back-order with no information regarding shipping date.
  • Lithium-Ion look quite good, but the upfront cost is painfully high
  • Leaving TPPL and Lifelines… both good quality batteries, and I think I’ll be happy with either.