Sunday, May 15, 2011

From Lead to Lithium - trading simplicity for performance

I've decided to trade simplicity for performance. The lead-acid pack with battery management circuitry was very easy to maintain. Just plug in & charge. Lots of warning if the pack was being overdrawn and there was no need for temperature monitoring. They were durable batteries but they just don't give me the range I want. So, I ordered a set of higher-performance batteries plus a battery management system from Elite Power.

16 GBS-LFMP60AH LiFeMnPO4 - (4 banks, 60AH each)
1 BMS-16S battery manage system (no display)
1 EMC48-15 charger
With shipping, it all came to $2083.88 As a bonus, they did throw in a slightly damaged display. It's missing a couple LCD lines but it still has some use to it.

Even still, the whole system is quite a chunk of change! However, it will be worth it if it finally allows me to be able to use the BugE as a commuter vehicle. Over time, I hope to save enough gasoline to justify the cost of the pack. If gasoline prices stay where they are, that should not be too hard to do.

As a performance comparison, my real-world test range on a slightly damaged 2- year old lead pack was 12 miles with varying speeds & hills. Comfortable around-town range seems to be 10 miles one way. So, from the anecdotal evidence of lithium performance, I'm expecting an improvement in range due to...

1) not being damaged, unlike my present lead-acid pack
2) being somewhat lighter than the lead-acid pack
3) being able to use more of the capacity without damaging the pack
4) having more charge/discharge cycles before performance deteriorates

So, it's not beyond imagination to think I might be able to make the commute distance of 20 miles depending on how much energy I loose to wind resistance and hills. In order to do it, I'll need a re-charge at work for the return journey.

My journey will consist of roads that have rather easy slopes and allow me to drive at low speeds most of the time. All roads I've picked typically have good visibility and people are used to looking for roadway hazards such as deer or slow moving farm equipment. I have no doubt I could complete the journey at 20mph but be out of energy if entirely done at 50mph. So, the task is to find an acceptable mix of faster and slower speeds to allow the journey to happen in a reasonable amount of time.

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