Batteries & chargers
Cleverchimp offers 36-volt nickel metal hydride (NiMH) battery packs and chargers suitable for Stokemonkey. NiMH batteries provide the best balance of high power density, long cycle life, personal and environmental safety, and affordability for electric vehicle applications today. These packs feature rugged ABS enclosures and quality locking connectors, with carrying straps and rubber end caps, and are designed to fit neatly in the inner pockets of the Xtracycle “FreeLoader” carrier slings, but can be lashed or stashed any number of other places. 
The packs consist of 30 “D” or “F” cells (9 or 13Ah), spot-welded in series, with 25A discharge fuses. A thermistor and temperature fuse provide redundant overcharge protection, while the enclosures are ventilated to help keep the packs cool. A single connector port serves both charge and discharge functions. The chargers operate without a fan, for quiet use in the workplace or home.
| 9Ah | 13Ah | Charger | |
|---|---|---|---|
| Physical | 12lbs, 12.5×5″ | 19lbs, 18.5×5″ | 3×4×5″ |
| Cost | $350 | $425 | $50 |
| Pro |
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Silent, cheap, light, redundant “smart” pack protection features including relatively slow charge rate (1.8A) |
| Con |
|
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At 1.8A, takes overnight or a long workshift to charge a 13Ah pack. No fan means it can shut down if used in a hot room. Pro/con does not imply a choice; do not use the packs with other chargers; do not use the chargers with other packs. |
If used with Stokemonkey, I recommend the lighter, smaller 9Ah pack if you plan to ride less than 25 miles in low mode (or 15-20 in high mode) between recharges, or will rely on your own power more for longer rides, at lower speeds. The 13Ah pack is for more demanding applications, where its considerable weight and bulk can be accepted as a necessary evil. Purchasing multiple packs is reasonable; they can be rotated to help assure that one is nearly always charged, while allowing for both (or more) to be brought along for longer trips.
Discharged to about 20% of capacity, these packs should last between 300 and 500 charges before you recycle and replace them. Less deep discharging should result in longer cycle life, so the larger pack will last longer for a given regular duty cycle. Similarly, the larger pack will deliver more of its rated capacity when discharged at a given intensity than the smaller, so the performance difference is somewhat greater than the capacity ratings alone suggest.
Notes
We sell the first pack and charger together. If you want additional packs or chargers after you have at least one of each, that’s OK.
Don’t open the enclosures unless you understand safe electrical handling practices.
NiMH batteries become warm toward the end of their charge cycle, and during rapid discharge. Excessive heat can shorten the life of the cells. Therefore, do not block the ventilation holes. If the pack is very warm, the charger will not begin a charge cycle until the pack cools. Pack performance also diminishes when the cells become very cold. You should not charge NiMH packs before they warm up to at least 50F.
NiMH batteries will self-discharge when unused. To assure full capacity when needed, as well as to keep the packs at desirable temperatures, we recommend leaving packs connected to their chargers indoors when not in use.
NiMH batteries that have not been used for months will not reach full capacity before a few complete charge/discharge cycles. You should ride in low-power mode for the first several charge cycles to condition your pack. We test the packs to assure that they take a full charge before selling them, but do not discharge and repeat. Please keep this in mind when using your packs the first few times.
Warranty
We will repair or replace packs that fail to hold a full charge or reveal defects in materials or workmanship for 6 months. Rechargeable batteries are consumable items whose service life and capacity will vary with operating conditions. If purchased together with Stokemonkey, 1 pack and 1 charger are covered under Stokemonkey’s 6-week money-back guarantee period. The chargers are warranted against defects for 2 years.