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The most important aspect of a power wheelchair is its power - that is, the electricity that powers the wheelchair via rechargeable, deep-cycle batteries. It used to be that most power wheelchairs came standard with a very traditional charging source: An off-board, 8A battery charger, commonly made by Lester Electronics. However, in the late 1990s, other battery charger technologies entered the mobility market, including "on-board" and "switch-mode" chargers, resulting in the multiple charger options that we find in today's mobility market, prompting consumers to ask, "Which charger is right for me?"

Of course, there is no universally correct answer, especially since some power wheelchair models are limited in the type and size of chargers that they accept. However, many higher-end power wheelchairs offer and accept more than one charger option, which can be matched to the consumer's lifestyle.

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Off-Board
Off-board chargers are the most traditional choice for consumers. As stationary, automatic chargers, off-boards can be left plugged into a wall outlet, in a fixed spot, where the wheelchair is simply plugged in as needed for charging via a far-reaching charger cord. With 5A and 8A start-up rates based on long-used transformer technology, off-boards are powerful, and prove remarkably reliable, lasting 8 to 10 years in many circumstances.

It's important to note that off-board chargers are heavy - around 10 lbs. - and dimensionally large, approximately 10"x10"x10" cubes, making them very impractical for travel.

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On-Board
An on-board charger, as the name suggests, is mounted internally on the power wheelchair, integrated into the electrical system. To charge, one merely runs a supplied cord from the wheelchair to the wall outlet, which starts the system. Naturally, on-board chargers are most convenient toward traveling, where the charger is always with the wheelchair.

Despite their convenience, on-board chargers aren't without drawbacks. Firstly, on-board chargers are typically lower amperage than off-board chargers, as they must be compact to fit within a power wheelchair, resulting in 2.5A to 5A chargers that can take longer to charge 55Ah to 80Ah batteries. Secondly, because an on-board charger requires mounting room, the wheelchair, itself, may be a bit larger than otherwise needed, especially rehab wheelchairs in which large motors, batteries, and electronics already consume so much space. Lastly, when issues arise with on-board chargers, they can be difficult to service and replace since they are integrated within the wheelchair.

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Compact Off-Board/Travel
Compact off-board chargers are truly next-generation chargers in the power wheelchair industry. Compact chargers use "solid-state," "switch-mode" technology, which proves dramatically more efficient than traditional transformer-based chargers, resulting in a compact 5A charger that can rival - and exceed in some areas - a traditional size 8A off-board charger. Specifically, compact solid-state chargers regulate 115V input at a rate of 100,000 pulses per second, compared to the rate of only 60 per second with traditional off-board chargers. As a result, switch-mode chargers typically have an efficiency rate of 90%, compared to an average of only 50% for most traditional, tapered chargers, allowing a powerful, fast charger in a very compact package. Compact chargers are typically available in two sizes, one measuring approximately 12"x8"x3, designed for relatively stationary use, and the "travel" versions, measuring 7"x4"x2", easily fitting in a backpack or luggage.

The one downside of the "travel" version of solid-state chargers is that one must be careful not to drop them, as they can be easily damaged.

Charger Amperage (Size)
Chargers are available in start-up amperage rates (commonly noted as the charger's "size") that range from 2.5A to 8A (though, there have been products at the extremes of .5A and 12A). A general rule is that the charger's start-up amperage rate should equate to approximately 10% of the wheelchair's battery's capacity:

 30Ah-40Ah U1 batteries correspond to a 3A charger
 50Ah-60Ah 22NF batteries correspond to a 5A charger
 70Ah-80Ah batteries correspond to an 8A charger

If a charger's output is too low in relation to the battery size, as in using a 3A charger to charge 80Ah batteries, it will take dramatically longer to charge than by using the correct size 8Ah charger. Conversely, too large of charger for the wheelchair's battery size may damage the wheelchair's electrical system if it's not designed for higher amperage charging. The exception to the 10% rule is the 5A and 6A solid-state, compact chargers, which perform exceptionally well all the way up to 80Ah batteries.

Using a Different Charger
Consumers often wonder if they can use a different charger than the one that came with the power wheelchair, one purchased online, for example? It's a question that takes some investigating to find the right answer in each situation. While almost all off-board chargers use the same connector, called an XLR, to plug into the wheelchair's charging port, there's not an industry standard among the positive and negative pins that must mate up between the charger's cord and the wheelchair's charging port. In this way, if the pin pattern does not match, the charger can be immediately destroyed when plugged in. It is true that a skilled electrician can determine the pin locations with instruments or diagrams; however, this isn't feasible for most consumers. For these reasons, it's advisable to only use a charger with compatibility confirmed by the wheelchair provider and charger manufacturer.

Charger Troubleshooting
Charger isn't powering on:
1. Confirm that the charger's cord is properly plugged in, both to the wall outlet and the charger (if applicable).
2. Ensure that the charger's power switch is turned on (if applicable).
3. Confirm that the wall outlet has power, that a connected light switch wasn't turned off or a breaker tripped.
4. Check the charger's accessible fuse, if applicable.
5. If the charger still does not operate, contact provider for service.

Charger takes an unusually long time to charge batteries, or batteries don't maintain charge when charging is complete:
1. Contact provider to service the power wheelchair's batteries.

Fortunately, power wheelchair manufacturers typically optimize battery chargers to each wheelchair's battery capacity. Still, there are situations where a consumer has the option to select among several choices of chargers, or wishes to purchase a different style of charger than came standard. In these situations, know what type of charger is wished, which amperage rating is needed, and, most importantly, whether the charger's plug configuration is compatible with the power wheelchair's charging port. If one takes these considerations into account, along with consulting with the wheelchair provider, one should be on the way toward optimal battery charging and range.

Published 11/07, Copyright 2007, WheelchairJunkie.com