Wheel Chair Batteries

Wondering if anyone has experience and/or recommendations for care of electric wheel chair batteries.
I know its not exactly a "solar" question, but its about battery care which is related.
A friend of mine is a c7 neck break partial quadriplegic and is dependent on an electric wheel chair, and thus the batteries.
I think the batteries are sealed lead acid or AGM. She was given advice that the batteries had a "memory effect"' like a NiCd and so should drive them to the bottom before recharging. I think this advice is incorrect. I have encouraged her to top them off every night. Thoughts/advice?
Also, the charger is a wheelchair specific device. It seems to support bulk and float charging. Do these batteries need to be equalized once in a while?
I know its not exactly a "solar" question, but its about battery care which is related.
A friend of mine is a c7 neck break partial quadriplegic and is dependent on an electric wheel chair, and thus the batteries.
I think the batteries are sealed lead acid or AGM. She was given advice that the batteries had a "memory effect"' like a NiCd and so should drive them to the bottom before recharging. I think this advice is incorrect. I have encouraged her to top them off every night. Thoughts/advice?
Also, the charger is a wheelchair specific device. It seems to support bulk and float charging. Do these batteries need to be equalized once in a while?
Comments
it is really hard to advise let alone comment on this because we aren't sure what type of battery she really has as they could be agm, gel, nicd, nimh, etc. nicd batteries are the ones people complain about for memory. as to eq charging them, don't bother. if you wish, you could rearrange the batteries and that could even things out too without excessive charging that eq brings even on batteries that normally don't get eq charges as some nicd and nimh batteries end batteries stress somewhat.
ps sorry to hear of her disability.
Seriously Dabbler, more information is needed before proper advice can be given. I'm sure there is advice to be given, which could have a great impact on the lives of those batteries, but we have to first know what we're dealing with.
Perhaps the provider of the wheelchair can supply the battery type etc, or is there a name and number on the batteries?
Proper maintenance is a serious concern.
Regards
Wayne
Thanks, you're both right. More detail needed. I know better, sorry for the brain fart!
The chair is an Invacare Ranger X, and uses these batteries:
http://www.apexbattery.com/invacare-action-ranger-x--ranger-ii-wheelchair-battery-wheelchair-batteries-invacare-wheelchair-batt.html
That says the batteries are valve regulated sealed lead acid gel chemistry, 60 amp hour X 2 batteries. Isn't it true that they should be kept topped off, and not run to the ground before charging?
Also, a second set of batteries (but older) exhibits significantly less battery capacity. I have sometimes "revived" normal lead acid batteries with an eq or two I but I don't know if you do that to SLA gels.
Thanks for any recommendations you may have.
You are so right!!!! To run these batteries flat is nothing short of murdering them. They should never (if possible) be discharged below 50% and preferably not more than 20%, leaving 80% still in the batteries. They should also be recharged after every days use.
`Lead-Acid batteries do NOT have a memory, and the rumor that they should be fully discharged to avoid this "memory" is totally false and will lead to early battery failure.`
You will find EXCELLENT information here:
http://www.solar-electric.com/deep_cycle_batteries/deep_cycle_battery_faq.htm#Cycles%20vs%20Life
Also:
http://www.trojanbattery.com/BatteryMaintenance/Discharging.aspx
Hopefully the batteries haven`t already been damaged too badly.
Cheers and all the best.
Wayne
Basically, the NiCAD "memory effect" was a very specialized issue dealing with satilites which went through hundreds of charging/discharging cycles that were exactly the same (same amount of current draw, exactly the same sun/dark cycle time)... This caused the place where the discharge "event surface" to stop at exactly the same place in the cell each time. And this causes the NiCAD structure to form larger than normal crystals right at that interface. The large crystals (as I understand) probably have less surface area than the numerous small crystals that form when charged and discharged through the various crystal "boundaries"--which caused voltage depression because these large crystal areas could not support the expected discharge current when the cycle went "deeper than normal".
NiCADs and NiMH do take deep cycling very well... But any battery chemistry can be destroyed when either Over Charged (causes overheating and possible venting of water/electrolyte) or deep discharging where a series string of unmatched cell capacities actually "reverse charge" one or more cells (reverse cell polarity). VLA/Sealed/AGM/NiCAD/NiMH all can be damaged this way.
Lead Acid batteries further don't like being stored at less than 75% of capacity for more than a day--the Sulfates (normal discharge chemistry) harden and will not return when the battery is recharged. Most Lead Acid batteries cycle life will dramatically fall if cycled below 50%--and especially if not immediately recharged.
Some AGM batteries (all?), because of their construction, are not supposed to experience sulfate hardening and can be cycled to 20% state of charge.
VLA and other sealed batteries are very sensitive to over charging (vent electrolyte when overheated/charged). Gell Cells are not very rugged batteries at all and should be avoided--if possible.
Most batteries are OK when stored at 100% state of charge--and many can be trickle charged with a low current / lower than charging voltage (see battery manuals).
Other batteries, such as Lithium Ion, don't like being stored at 100% charge as they will have a short lifetime.
Here is another Battery FAQ with descriptions of various battery chemistries and how best to store them.
By the way, I have figured out a neat way to "trickle charge" batteries in storage using their own cheap wall wart chargers that come with various rechargeable appliances (or used to trickle charge car/tractor batteries when in storage)... This chargers almost always will overcharge the batteries (and cause damage) if left plugged in for more than 1/2 a day--let alone leaving them plugged in 24x7 for 9 months--then you need the tool/light because your power went out in the storm... What I have done is to put a regular lamp timer set for 1 hour per day (or whatever you have measured/estimated is the correct cycle time) to power the wall wart... Reduces the average charge current to 1/24th of the wall wart capability, which keeps the battery charged--but not overcharged/overheated.
-Bill
Bill,
Once again you impress me with the depth of your knowledge and your research!
So,, all these years I have been putting the dying drill battery in the drill with a rubber band on the trigger has really been killing them rather than prolonging their life? Huh! I guess I will have to change decades of practice.
I noticed on my latest NiCd battery drill, the manual call for NEVER completely discharging of the battery. Now it makes some sense. I'll try it for a while to see if I get better battery life.
Next question (off topic of course!) is should I keep my NiMh computer battery plugged in and fully charge all the time, or should I leave it unplugged until I have dropped the soc a bit?
Icarus
PS I know that the NiMh batteries in the Prius are never "fully" charged, and they are never allowed to discharge more than ~50%
Icarus,
From my 2 cents... The earlier link:
So... If the tool/appliance has a small drain, disconnect the batteries for long term storage. If the battery device has no leakage current--leave pack in.
Don't keep on charger. Only recharge before use, or, if needed to be kept charged for an emergency--use my trick of a lamp timer set to turn "on" only and hour or so per day--will keep battery pack charged without (to much) chance of overcharging.
If you need NiMH batteries that should retain their charge between use (for months or longer), take a look at the AA and AAA Sanyo Eneloop batteries (and other "hybrid" / "pre-charged" NiMH batteries). They are supposed to keep 85% of their charge after one year of storage.
-Bill
Bill,
Once again for the helpful information.
What is not addressed there is; should a NiMh lap top be plugged in while 24/7 and while in use if you can, or are you better letting it draw down a while and then charge it? I surmise the latter.
Icarus
Awesome info Bill!
Thanks a lot. Really appreciate it.
Wayne
I leave my laptop, with battery, plugged in 24/7... It only charges for a few minutes randomly (usually only if I have unplugged it to move to another room and/or ran on battery for a bit rather than moving the cord).
My laptop should run more than 2 hours on a charge--but now it seems to die in 45 minutes or so... But it is probably 6+ years old and the battery is also my UPS--so I take it as price of having a 100% UPS'ed computer as corrupted data/disk is probably worse than buying a battery every 5 years (and in reality--probably a new laptop every 5-8 years).
I don't think that a UPS battery (probably gel cell) will last more than a year or so in one of the $100 UPS's (probably going unplug my desktop UPS--battery will only last a minute or so--and seems to burn more power than I would want while the computer is turned off 95% of the time).
-Bill
Ref: http://www.apexbattery.com/invacare-action-ranger-x--ranger-ii-wheelchair-battery-wheelchair-batteries-invacare-wheelchair-batt.html
Link to battery manufacturer's "maintenance instructions": http://www.universalpowergroup.com/Downloads/safety.pdf
Link to useful technical guide for VRLA (AGM and gel) batteries: http://www.mkbattery.com/images/VRLA_TechManual.pdf
HTH,
Jim / crewzer
Thanks to all of you for the great info, comments and suggetsions!!!!