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  • #16
    thanks for the links.

    I have viewed those before but didn't really find concrete answers. They say things like use your manufacturers charger and charge after every use, then they say don't top off. So if I zip in and out of a store real quick then come back home, do I charge or don't charge. They say the ideal discharge is @ 50% but I have no way of knowing that. My chairs charge indicator will normally say on full charge. Then when it starts going down, it will be in the Red within a 1/2 mile.

    Well, I'm sure it will all be fine. Just don't want to screw up $400 worth of batteries. That would hurt.

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    • #17
      My guess is are you in a Pride branded chair?

      Bad news NF22 are already a big downgrade in performance in the 1st place...most are getting less then 10 miles tops on them when working perfect. After 6 months that starts breaking down.

      So if you buy a cheap brand battery you're shooting yourself in the foot.

      MK is a leader in mobility batteries but some are having issues with them also.

      Do you have insurance and or medicaid or medicare? They are covered...

      One bad thing about buying online is you have no idea how long they have been sitting there not charged.

      Most DME can get fresh built batteries with a guarantee to them.

      Prices are $420 a pair on up...

      http://www.1800wheelchair.com/produc...caAvNIEALw_wcB

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      • #18
        Forget the chair's charge estimate lights, they are truly rarely correct, except when it reads red. Then the "voltage" has dropped below 12 VDC. To understand lead acid batteries you require a thorough knowledge of the chemistry of them. Your questions while good, show you very much like myself, do not have that thorough working knowledge. Try reading all the information available on the BatteryUniversity.com web site. If you go to that site, you will realize that we cannot easily answer your questions in a few short sentences. There is a lot to this subject. Once you have read the information on pb/lead acid batteries and you think you understand it all, read it all again you WILL find there is always more to get out of it. There is a lot of battery information on the WheelChairdriver.com web site as well.

        Batteries must be matched in "VOLTAGE" before you can charge them the first time. If one battery is slightly higher than the other, the charger will not see the lower battery's difference and it will charge to the higher battery's voltage tenths of a volt are huge. Those mismatched battery's will live very short lives. They never get close to being fully maximized. You cannot use the chair's wiring harness to hook batteries in parallel. (12 Vdc and 12 Vdc parallel still equals 12 Vdc) nor can they be hooked up to the chair, without some sophisticated customized wiring harness. Just use some common jumpers to connect positive (+) to positive (+) and negative (-) to negative(-) after 12 hours connect the battery's to your chair's harness and charge them normally, without the jumpers.

        There are some battery chargers that can tell you how many amp hours were replaced during the charge cycle. They are $$$$ but if you do the math they may well be worth the $$$ to you.

        I get 4 to 6 years with plain old pb batteries! But I don't travel far now, and I charge them intermittently (partially) whenever I am near my charger. I buy/ pay for my own chairs el-cheapo's off craigslist when I see them cheap enough and close enough. I buy my own batteries, not Medicare or Insurance, so you can appreciate my economy. MK batteries are the best in deep cycle and the glass mat are excellent for sports use power chairs, they charge quicker, and that battery system has the ability to produce their power more quickly for use.

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        • #19
          Figured I would add on to the end of this thread instead of starting a brand new one… I just received new MK24 batteries in my chair, and am unclear how often to charge them. I have been charging every night, their website seems to state to charge every night, but the DME tech said that was not good to do.

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          • #20
            Originally posted by landrover View Post
            Figured I would add on to the end of this thread instead of starting a brand new one? I just received new MK24 batteries in my chair, and am unclear how often to charge them. I have been charging every night, their website seems to state to charge every night, but the DME tech said that was not good to do.
            I had this discussion with a Permobil representative at the Abilities Expo in San Mateo last week. She said when deciding when to charge your wheelchair batteries take several things into consideration. Generally speaking under "normal" use conditions, it is a good idea to charge the batteries every night. However, if you didn't go much distance in the chair, say, just round your house, there may not be a need to charge the batteries if the next day is going to be a similar light use day. But, if you know that you will have a heavy use day, even though the indicator lights don't show the need for a charge, it is a good idea to charge them up anyway.

            The picture below is the controller I use on my Permobil M300. The red, yellow and green lights across the top indicate battery charge. If you have had a light use day today, plan to have another light use day tomorrow, and the last two green lights have changed color and indicate that you don't have a full charge, it will probably be okay not to charge the chair after use today. But, if those lights indicate you don't have a full charge and you will have a heavier use day tomorrow, it is a good idea to charge those batteries today after use. Lastly, it is a good idea to charge the batteries after any heavy use day.
            Attached Files

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            • #21
              Thanks. However my battery gauge rarely moves, but when it does it drops quite quickly.

              Comment


              • #22
                Originally posted by Bob Sullivan View Post
                Forget the chair's charge estimate lights, they are truly rarely correct, except when it reads red. Then the "voltage" has dropped below 12 VDC.
                I suspect most "fuel gauges" display some variation of the (instantaneous!) battery voltage. If the gauge truly reflected the state of the battery, then it wouldn't fall when you start to move (apply load) and then rise when you stop (remove the load). It's disappointing that an application where the "controller" can SEE the battery AT ALL TIMES and can see what it is ASKING of the battery (at all times) isn't smart enough to come up with a better appraisal of the battery's state.

                Batteries must be matched in "VOLTAGE" before you can charge them the first time.
                Actually, they must have the same "state of charge". Voltage is just a crude approximation to this.

                Charging batteries in parallel (without isolation diodes) is never a Good Thing as you're effectively shorting the batteries together -- the higher voltage will RAPIDLY drain into the lower.

                [voltage -- aka "potential" -- can be thought of as the height of water in a bucket (a battery). The water is the charge. Water wants to flow downhill. The rate at which the water flows is the current (amperage). The diameter of the pipe through which it flows is the resistance/impedance. I.e., a thin pipe has a higher resistance than a fat one so thin causes lower rates of flow. Connecting batteries directly together is one helluva wide pipe!! ]

                Batteries in most chairs are wired in series -- so, the voltages are "stacked" (12+12=24).

                If one battery has a problem (lower state of charge, shorted cell, etc.) then the charger is trying to charge the pack to ~24V but one battery is not taking up its fair share of the charge. Both batteries suffer.

                (Remember, in series, everything that comes into one battery also goes through the other battery before it "exits out the bottom")

                There are some battery chargers that can tell you how many amp hours were replaced during the charge cycle. They are $$$$ but if you do the math they may well be worth the $$$ to you.
                The CHAIR should be doing this! Shameful for vendors to be living in the 60's in terms of battery management! The device and the user should work, together, to optimize this ("Let me know when I really SHOULD charge you and I agree to let you know what my likely usage will be so you can better inform me of charging requirements" Instead of one approach fits all users/uses.

                Comment


                • #23
                  A bit off topic, but does heat effect battery life/performance. It seems on days when I sit next to a floor space heater, that night my battery seems to take longer to charge. Am I causing harm to my battery by doing so?

                  Comment


                  • #24
                    Originally posted by landrover View Post
                    A bit off topic, but does heat effect battery life/performance. It seems on days when I sit next to a floor space heater, that night my battery seems to take longer to charge. Am I causing harm to my battery by doing so?
                    Heat kills batteries. Well, heat "accelerates the aging of batteries" is probably a less biased way of saying it. Every ~15-18F degree rise in temperature HALVES the life of a battery. I.e., an hour at 90F is like two hours at 75F.

                    Remember, batteries are "chemical reactors". Heat changes reaction rates. High school chemistry: STP -- Standard Temperature and Pressure.

                    Charging usually generates heat in the battery so the temperature that the battery "feels" is higher than the temperature YOU feel sitting next to it (ambient).

                    Sealed batteries also build up pressure while charging (yet another Bad Thing).

                    The issue with batteries is always one of matching (user) convenience to battery performance/longevity. If you want to be kind to the battery (i.e., get the most USABLE life from it), you charge it gently, don't deeply discharge, keep it cool (and dry -- humidity also plays a role), etc. But, this is usually counter to how the user WANTS the battery to perform. You want it to be recharged QUICKLY, tolerate your squeezing every last coulomb (bit of charge) from it, store it out in the carport when not in use, etc.

                    For example, a battery's nominal discharge rate is referred to as "C". Ideally, you size the battery (the size of the bucket and the "exit pipe") so that it fits your application's needs. If you want 20A from the battery, then you want a battery that is designed to deliver (at least) 20A "comfortably" (without stressing its internal design). The length of time you can operate at that rate of discharge is indicated in the battery's specifications (and this degrades, over time and "charge cycles"). Obviously, you want this to be at least as long as you are likely to need the battery to provide power between charge cycles (!).

                    But, the flip side of this is that the battery wants to be charged at some SMALL FRACTION of this nominal discharge rate. Typically, C/10. So, if you're expecting to be drawing 20A from the battery during use, you are also expecting to be limiting your charge current to 2A! Said another way, in an ideal battery (where what you take out can exactly be replaced by what you put back in), for every hour of use that you expect, you need 10 hours of charge time (!!).

                    Do the math. Use a battery for 2 hours and spend the next 20 hours recharging it. Given that you won't be 100% efficient at restoring the charge taken from the battery, you can easily see how 2 hours of use can become 22 hours of recharge.

                    OTOH, if you OVERSIZE the battery -- so that it can deliver 40A -- then that 20A load doesn't tax the battery as much. And, if you can charge it at 4A (i.e., 40 / 10), then the 2 hours of use can be replenished in ~10 hours, instead of ~20. (But, now you're hauling around more weight, a more expensive battery, a larger "battery compartment", etc.)

                    [Of course, if you can deliberately slow down your charger to deliver only 2A, then your battery will be happier -- assuming you can tolerate the time that it will take to recharge: "Sure! I'm not planning on going anywhere, tomorrow!" A smart appliance would watch to see how much "energy" it is using and know how aggressively it would have to recharge -- IF IT KNEW THE USER'S FUTURE NEEDS! Imagine if your chair "remembered" that Wednesday is your "busy day" -- lots of use -- but Thursday is a "slow day": "Let's take our sweet time recharging, Wednesday night, as we've got very little need tomorrow!"]

                    You just have to come to an accommodation between your "desires" and your "finances" -- trade one for the other as you see fit.
                    Last edited by automation; 11-04-2018, 04:47 PM.

                    Comment


                    • #25
                      Landrover...1st week try and charge 12 hours you need 15 charges for the batteries to be broken in and always charge every day even if not using.

                      After the 1st week you can charge for 8 hour a night and be good.

                      Did you get the larger 24s or still using the 32's?


                      Once a month they and get on 15 hour charge.

                      Also we use a small electric throw blanket that plugs in keeps me much warmer and heats faster then sitting by a heater.
                      Last edited by RollinPositive; 11-04-2018, 10:51 PM.

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                      • #26
                        I received MK 24s.

                        A electric blanket would not work for me. I'd be stuck plugged in somewhere.

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                        • #27
                          Originally posted by landrover View Post

                          A electric blanket would not work for me. I'd be stuck plugged in somewhere.
                          Not to mention, you can get a nasty burn from electric blankets, throws, and mattress covers when they are resting on an area where you can't feel the heat.

                          Comment


                          • #28
                            Originally posted by gjnl View Post
                            I had this discussion with a Permobil representative at the Abilities Expo in San Mateo last week. She said when deciding when to charge your wheelchair batteries take several things into consideration. Generally speaking under "normal" use conditions, it is a good idea to charge the batteries every night. However, if you didn't go much distance in the chair, say, just round your house, there may not be a need to charge the batteries if the next day is going to be a similar light use day. But, if you know that you will have a heavy use day, even though the indicator lights don't show the need for a charge, it is a good idea to charge them up anyway.

                            The picture below is the controller I use on my Permobil M300. The red, yellow and green lights across the top indicate battery charge. If you have had a light use day today, plan to have another light use day tomorrow, and the last two green lights have changed color and indicate that you don't have a full charge, it will probably be okay not to charge the chair after use today. But, if those lights indicate you don't have a full charge and you will have a heavier use day tomorrow, it is a good idea to charge those batteries today after use. Lastly, it is a good idea to charge the batteries after any heavy use day.
                            The Permobil rep you talked to has no idea what she is talking about!!

                            Per MK:

                            -----Original Message-----
                            From: Belinda Perez [mailto:bperez@mkbattery.com]
                            Sent: Monday, November 05, 2018 2:13 PM
                            To: RollPositive
                            Subject: Batteries and charging

                            Hello RollPositive:

                            That is correct you should charge your batteries daily after use. I recommend charging at least 8 hours if possible and maybe 10 once a week.

                            Let me know if you need further assistance.


                            Belinda Perez
                            Customer Service Representative
                            MK Battery
                            714 922-2025 (Direct line)
                            800 372-9253 (Customer Service)
                            714 937-0818 ( Fax )



                            Go paperless, visit our MK E-Store and register on-line
                            "placing an order just became easier!"
                            www.mkbattery.com

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                            • #29
                              Originally posted by gjnl View Post
                              Not to mention, you can get a nasty burn from electric blankets, throws, and mattress covers when they are resting on an area where you can't feel the heat.
                              Why would you use an electric blanket if you have issues with not being able to feel sensations that would harm you?

                              Give the possible user some acknowledgement of having common sense.

                              Think about if the same could happen sitting in front of a heater and being to close...

                              Comment


                              • #30
                                Originally posted by landrover View Post
                                I received MK 24s.
                                With 24s your battery lights should not drop that fast...the 1st light should drop off after about 5-7 miles the 2nd light should drop off after 8-10 that last one after that 10-11 mile range.

                                Also with Permobil after rolling around say for 5 miles and one green goes out after you stop it should come back and relight.

                                I would say with not to much steep hills etc you should get 15 miles on a charge use your odometer vs the lights for a more true picture of miles per charge.


                                Top speed, rider weight, jack rabbit starts and stops, grass all play a part in lowering the over all charge.

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