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Thread: Charging Batteries - MK 22NF Gel

  1. #1

    Charging Batteries - MK 22NF Gel

    I'm confused about the proper or best way to charge pc batteries, specifically, the 22NF Gel batteries.

    I've been told contradicting info regarding the best way to charge, and the meaning of "charge cycles" and how that effects battery power, duration (per full charge), and overall battery life -
    * Charge when battery runs down to orange bars (approx. 50-60% discharged) - Freq. charging when still at high capacity, ie. charging only when 10% used, will shorten batt cycles and life (vendor 1).

    * Charge battery REGARDLESS of use; Charge DAILY, so batt is always fully charged (told recently by a vendor 2).
    ** how is this consistent with NOT "topping-off" (see below)

    (MK brochure)
    - Overcharging is not a problem, as charging automatically shuts off.
    - Battery shouldn't be "topped-off" with too frequent charging at high capacity (eg. 10+ %)

    * Charge Daily
    * Charge when at least 50% discharge
    ^ are these referring to ONLY "active users" who freq. deep discharge??
    I'm also curious to know how a NEW battery should be charged, to help increase use/life, IF there is any need at all to charge differently when new.
    * (Vendor 2) Battery should be charged daily, at least the first few days.

    * (MK rep) Battery doesn't need to be charged daily, IF not in active use and there is only 10% or so use. BUT, batt can be charged at 10%, without any problems or effects caused.

    I have read the MK brochures on Battery care and charging, but am still left confused, even after speaking with a rep there.
    - Per rep., it doesn't matter how much the battery is used, that charging will not diminish capacity and lifespan, nor will it effect the number of cycles. Then, rep states that charging at 25% will allow 500 cycles, while charging at 10% allows 1000 cycles. Main issue to watch for is letting it discharge too much before charging - eg. @ 50% or more discharge).

    - "Break-in" period is necessary (15-20 cycles) to fully activate the battery for max performance and longevity. They refer to "deep cycling", active users charging daily, which is a stringent application that might sometimes compromise initial capacity for longer life. Does this mean that "deep cycling" is better or necessary for a return in longer life? But how is this consistent with "charging at low capacity or high discharge SHORTENS overall, capacity, power and longevity"??

  2. #2
    Senior Member CapnGimp's Avatar
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    Battery Lifespan is dependent on one thaang mainly- how deep you discharge.
    I TRY to charge at about 70%, deeper discharging shortens the 'life ' or more aptly the number of recharges you get before 'death'. Get out beans and push'em about until you cipher what that equates to in bars or lights on your indicator. Then let your batteries live long and prosper. Charge at 70-75%.

    MK posted a chart years ago that compared discharge level to recharge cycles. Low discharge rate on top left, High recharge cycles top right. About 500 cycles was the expected lifespan at optimum usage, tapering off really fast after 65-70% discharge. I remember 200 beside of those over 50%...or close. But you get the idea. Maybe we can find another chart...I posted it way back for somebody.

    I realize with one power chair, you OFTEN are out of charge before your day is done. And want to keep using your chair into deep discharge range.... thats a no-no, you will wind up replacing batteries every year. I know
    Unless all your use is indoor/flat/smooth, then you MAY wind up with little discharge at the end of the day. THEN ya wonder ...SHOULD I recharge?
    MY practice is recharge each use, unless you only used it a little bit. Then I'll wait another day.
    The 10% figure is good. If you only take the pet duck billed-platypus to the neighbors to shIte once or twice a day and use the manual all day, then I'd NOT charge it every 24.... if that helps.

    NEW batteries should be used lightly at first. Like they told you, 15-20 cycles, you reach maximum charge capacity. They are noticeably fast at discharging when new.

    Also VERY important...charge it before FIRST use.

    RARELY is a battery 100% charged when new. They aren't shipped to dealers that way. It may take over 8 hours to charge them to 100% when new, if it has a high amp/hour rating.
    You said you have 22NF, those are small, but still will take a few hours to charge-first use. If you use the w/o initial charge, you'll ruRnM PLus-you WILLl note, when retrieving your afore-mentioned duck billed-platypus...that your batts are almost dead and you will have to QUICKLY train him/her to push...annn it pROLlY hain't happ'n.

    Hope IT help, If I can make a 50 amp/hour each battery pair last half a day, I wasn't working it. 85 amp/hr batts will make it a day for me. I had 35 amp/hr batts in a lightweight chair that would make it half a day with medium use.

    I use mine pretty rough though. 'Indoor' use with your lighter chair, you probably get a day's use unless you go long distances. They make smaller size 50's now. I just took a beating for a pair. Took me about a month to really get them 'broke in' and I did a bAAAAd thaang... I used them to pressure wash the driveway all day and twice discharged them to 50%...maaaaybe less...I don't think it hurt the capacity, but I don't recommend it.
    Last edited by CapnGimp; 08-06-2010 at 01:38 AM.

  3. #3
    Senior Member CapnGimp's Avatar
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    Your last questions...DON'T deep discharge, it's never good, stay way above 50%. Sounds like he meant that Those who use their chairs EVERY day, med to deep-discharging them, should REALLY be careful to charge them EVERY night. Batts left in a discharged state, diminish capacity quickly, and it isn't regained in any way.

    I staank I answered ya fully. Hope it helps. Live Long and Prosper ChickO

    LOOKIE whut EYE founT...
    Last edited by CapnGimp; 08-06-2010 at 01:48 AM. Reason: for the sake of editing...

  4. #4

    MK Battery recharge

    I could not have said it better. Anyone who would have read your anology of battery charging recomendations would be fully charged or at least better informed. Impressive

  5. #5
    CapnGimp, this is almost identical to what my DME told me.

    ''Life's tough... it's even tougher if you're stupid!'' -- John Wayne

  6. #6
    Well said Cap'n.

  7. #7
    Thanks Cap'n! I thought (hoped) you'd chime in sooner or later (yay for sooner! )

    Re your reply, I figured as much, but with a vendor installing my new batts earlier this week telling me - charge the new batts overnight for at least 4 days, REGARDLESS of how much or little you use; and his understanding of batt life cycle being more or less a set amount, with freq. charging at low discharge only "wasting" charge cycles, thus limiting longevity/use; while another vendor a few months ago telling me to charge daily, NO MATTER the discharge % - I needed more confirmation (thx to the other replies too!).

    Plus, with the MK FAQ section stating:
    "Don’t “top off” the battery with frequent charging.", I was a bit confused, and maybe still am a bit, with the exact meaning of "topping off"...

    Is to "Top Off" referring to charging when it's at very low discharge, eg. <10% (ie. only using under 10% of battery charge?). And doing that too regularly?

    And, does frequently stopping charge BEFORE charge is full and complete have any negative effect?

    Thanks again for all your feedback folks!

  8. #8
    Last edited by chick; 08-07-2010 at 03:59 PM. Reason: double post. mods, pls delete. THX!

  9. #9
    Senior Member CapnGimp's Avatar
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    I should have placed in bold print :

    You do THIS trick much and your batteries die QUICK!!

    It's the FASTEST way I know to ruin a battery.

    CHARGE 100% before use.

    Topping off refers to charging when batteries are fully charged, THEN you just use it a little, ie. the SHOULD just park it w/o charging. Your batts are at above 90% charged.

    IF ya charged it you would be 'topping off' and this is not good.

    You drive around with a full tank of gas(charged batts) and only go to the neighbors and back. You wouldn't go to the gas station and put 2 pints of gas in 'topping off', it would be a waste of time. This shortens capacity and life(cycles remaining).

  10. #10
    Senior Member Norm's Avatar
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    Jul 2001
    Media, PA
    How often do you change your batteries?
    "Some people say that, the longer you go the better it gets the more you get used to it, I'm actually finding the opposite is true."

    -Christopher Reeve on his Paralysis

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