Dead (mobility) battery test?

[MeldrewsMate]

Wasn't sure in which category to post this enquiry, but here goes.

I've just bought a mobility scooter for my dad. He has just had to give up his driving licence, and can't walk back home from the chippy fast enough to avoid cold chips.
I half expected to have to buy a pair of new batteries (each 12v, 30Ah deep discharge), but after topping up with de-ionised water I still tried to charge them on my smarty-pants motorcycle charger. After about 24 hours on charge the first battery was gassing-off furiously on one cell, taking 4A of current, and measured about 10vdc open circuit. The second battery was charging at 2A, not gassing, but only about 7.5 v open circuit (both readings immediately after disconnecting the charger).

Are they goosed beyond recovery? I expect so, and intend to connect them up for a trial run tomorrow - obviously after dark so the neighbours don't see me!

As for new batts, what are the brands that seem to perform best in this traction application, for both range (REAL capacity) and longevity.

MM

 

[sircerebus666]

Looks like it , from memory anything less than 10.5v is a knackered battery.

I take it your charger is a smart one capable of reviving dead batteries? If so then the batteries are goosed and need replacing

If you were able to recharge them chances are that they wouldn't last long when put under load anyway leaving your poor dad's chips getting even colder cause he has to push the scooter home

 

[magicmushroom666]

Yuasa brand batteries are high quality and we use them all the time in industrial applications. Reliable and always meet their spec.

 

[Burnerman]

All of the battery cells should gas the same - it's a sure indication of a knacker if they don't.
One more vote for Yuasa - the best by a mile.
John

 

[Peter.N.]

Got one duff cell - at least. I would concur on Yuasa.

Peter

 

[ericmark]

I had the same, two 12 volt batteries, one cell went down, resulted in 11 cells being over charged, so both batteries US, went to Tayna batteries in Abergele but it was not their own battery but imported.

In the main mobility scooter batteries are AGM or VRLA two names for same thing, and sealed, using a "Smart" charger I have had a battery come up after 2 weeks charging as if some one has flicked a switch, but since one cell gassing likely that battery is US and really need to be used as pairs. With my scooter can only charge and use as pairs.

Seems odd that you can top up, in the main you can't, so seems likely some one has fitted some cheap car batteries, at £44 to £105 each not cheap, but for a car battery around £30 so it would seem fitted with a car battery not a scooter battery.

AGM batteries need a special charger, you can get them from time to time at Lidi for £14, (12 volt) but in the main £35 plus, and for a 24 volt charger even more. So may be you don't want AGM? But discharge curve on a AGM is so you can do 4 MPH for whole 25 mile range, or if road model then 8 MPH. And the AGM battery is cheap when compared with £300 for an ebike battery.

 

[Peter.N.]

I just bought two 12v 82 ah deep cycle batteries from Tayna for not much over £100 as back up batteries for my ham radio equipment. The previous ones I bought second hand about 10-15 years ago and they have only just failed. I charge them at a continuous 13.2 volts as that is the theoretical fully charged voltage, doesn't charge them very quickly but it doesn't need to, they don't very often get used, but stops them from drying out.

Peter

 

[ericmark]

As you say 13.2 volt is the normal float charge voltage, but my smart charger alternates 12.8 to 14.4, when the voltage drops to 12.8 the charge rate jumps to next stage, and at 14.4 drops again to lower stage, mainly 0.1 amp and 0.8 amp.

However the old FT290R was happy 10 to 16 volt, but the IC290 was very voltage dependent with full output of 30 watt needing 13.8 volt.

I have always been interested in lead acid batteries, since the collage home work, "Why does a battery voltage reduce?" and to be frank, still not sure why. The chemical reaction of a fully charge lead acid is not different to a nearly flat, so why does it not like the Daniell cell maintain the same voltage?

The home work set in the 70's so no internet, all I had was collage library, which had books explaining the reason for volt drop with Leclanché cell and I assumed in my home work, that the lead acid was similar.

It seems likely all the lecturer wants was "Because it is discharged" but I got 9½ marks and everyone else 2 marks, so I was not popular. However I tried over the years (trained as an auto electrician) many methods to revitalise batteries, however it was only a few years ago that I had an energy monitor so I could see how the battery charged.

Started with 2 x 7Ah stair lift batteries, so flat would not charge, the smart charge just did not what to know, so connected in parallel with a good battery. Nothing for 10 days, then as if some one had flicked a switch, started to charge and ended up as if nothing had ever been wrong with them.

This was repeated 3 times, seems it was nothing to do with chemicals put in the battery, it was simply time, just as time hardened the sulphur so it also softened it, however a faulty battery is still a faulty battery, so if one cell short circuited the current can be quite high once the other cells accept charge.

So the 7 Ah battery and a very low rate battery charger is what is needed, and being able to monitor progress.

But two batteries in series has always been a problem. Grove cranes were the first I found the problem with, the Delco alternator had a three phase transformer built in, and gave both 12 and 24 volt output, it was 12 volt run but 24 volt start, and the batteries would become uneven, so every service needed to swap the two batteries around.

The same problem with one old and one new, but swapping them around does not help, be it a Landrover with 2 x 6 volt batteries or a mobility scooter with two 12 volt, the new one ends up over charged and the old one under charged.

So when one battery fails what do you do?

In the main we renew both, and use the old one to match up with some other old battery, OK with an auto electrician with a fleet of Landrovers with 6 volt batteries, not so easy with a single mobility scooter.

Wonder if you have any ideas, 73 Eric VP8BKM, VR2ZEP, GW7MGW.

 

[Peter.N.]

I don't use a smart charger mine are good old fashioned mains transformer types. With one of those if the battery is OK it will start charging at a fairly high current immediately you connect the battery, the current should then gradually drop until the battery is fully charged.

If you get little or no charge then the battery has a high internal resistance and is probably no good, you can try leaving it connected for a day or so and its just possible it will start charging.

Conversely if the battery continues to show a good charge but does it continually over several days you will probably find its getting warm and gassing on one or more cells that is also a fail.

If they have been left in a discharged condition for any length of time that usually kills them.

The 13.2 volts is only for batteries that are not used for most of the time like my standby pair but that doesn't bring them up to full charge, just keeps them healthy. For batteries that are being used, especially with a relatively high drain as your traction batteries they need about 14.5 volts.

Peter

 

[ericmark]

If you get little or no charge then the battery has a high internal resistance and is probably no good, you can try leaving it connected for a day or so and its just possible it will start charging.

Five years ago I would have agreed with you. However I found out it can take two weeks, but before the "Smart" charger the old type could do all sorts when left unattended.

Conversely if the battery continues to show a good charge but does it continually over several days you will probably find its getting warm and gassing on one or more cells that is also a fail.

This is the problem, you need to limit the charge rate, not just voltage.

The 13.2 volts is only for batteries that are not used for most of the time like my standby pair but that doesn't bring them up to full charge, just keeps them healthy. For batteries that are being used, especially with a relatively high drain as your traction batteries they need about 14.5 volts.

This again is a problem, how does one charge without over charging, so the constant current charger comes into its own, so my battery charger has two limits 12.8 and 14.4 volt. At 14.4 it drops charge rate, and 12.8 it ups the charge rate, so it alternates between the two. So it ends up with a square wave, this seems to work very well with the VRLA or AGM battery.

I don't use a smart charger mine are good old fashioned mains transformer types. With one of those if the battery is OK it will start charging at a fairly high current immediately you connect the battery, the current should then gradually drop until the battery is fully charged.

This was all well and good with a flooded battery, I have a number of chargers that work like that, but mobility scooters, stair lifts, intruder alarms, Jump start packs, and cars with stop/start technology all seem to use AGM or VRLA batteries, so the old battery charger has been retired, as no longer fit for purpose. OK discharge battery and I want to use the car, they still have a place, but in the main we have been forced to use the likes of the Ctek battery charger.
Go to Halfords web pages, and most of the battery charges state "Not suitable for AGM battery".

The problem I have is since auto 6/12 volt, if the battery is under 7.6 volt I can't use the smart chargers I have, the Ctek charger will go lower, but has no 6 volt option. So the only way I can charge with a smart charger is to put the battery in parallel with a good battery, using a good 7 Ah with poor 75 Ah no real problem, but the reverse, a good 75 Ah with poor 7 Ah one is praying the 7 Ah is only sulphated and not faulty, and if it is this is the result, and inside the casing for the mobility scooter one is unaware what has happened. In this case two mobility scooter batteries being charged as 24 volt, with one cell short circuited so only 22 volt, so the 5 amp charger, yes only 5 amp, over charged the good battery.

In real terms it did not matter, so could not really renew as a single battery when 15 years old, had to renew as a pair, but I could have found a use for the 35 Ah AGM battery had it survived. I still have my FT290R, although today tend to use a cheap pofung duel band radio.

Sorry @MeldrewsMate it is your thread, but clearly myself and @Peter.N. share a hobby, and as Radio hams many of our radios are 12 volt powered. I was trained as an auto electrician, so the lead acid battery was a big part of my trade, but 1980 I started a sidewards move, and now consider myself as an electrical engineer, however with nearly 70 turns to the coil, retired, but the stop/start technology has turned what we knew about lead acid on its head, and we have been forced to revise our thoughts on charging.

 

[Harry Bloomfield]

I half expected to have to buy a pair of new batteries (each 12v, 30Ah deep discharge), but after topping up with de-ionised water I still tried to charge them on my smarty-pants motorcycle charger. After about 24 hours on charge the first battery was gassing-off furiously on one cell, taking 4A of current, and measured about 10vdc open circuit. The second battery was charging at 2A, not gassing, but only about 7.5 v open circuit (both readings immediately after disconnecting the charger).

Topping up? They must be very old batteries almost all modern ones are sealed, especially mobility scooter ones. Both read as if beyond redemption, Yuasa is the recognised deep discharge battery now.

 

[Peter.N.]

Allow me to introduce myself. Was a TV engineer for 50 years starting in '54, retired in 04, now coming up 82 (have had both jabs) One of my first jobs in the shop was charging accumulators, much less technical that it is now!

Didn't get my licence until the '80s' via CB like most of the G4's. was very active initially but slowed somewhat later, still here though and active mainly on 2m, high up here so get quite good coverage.

I will bow to your superior knowledge on battery charging - why do they have to keep changing everything. I have a big garage charger with a 'start' setting but only use that on the cars, but I do have a smaller one which is well regulated in that it gives quite a hefty charge initially but drops to near enough zero when fully charged.

I had a wind turbine for some years until the batteries gave out, my fault really, the alternator packed up and I left it for some time and the batteries eventually went flat and wouldn't charge. I now use the tower to support one end of my HF antenna.

Peter G0HET

 

[MeldrewsMate]

I've tried to follow this thread, no really I have, but I have concluded that the old batts are dead - long live the new batts! Fitted and working I faced the ignominy of driving a 4mph (max) mobility scooter 5 miles in driving snow and pelting rain (I'm tough, but don't let that cloud your judgement) to prove the scooter's range. 5 miles is plenty, enough for the weekly supermarket shop AND those Friday night chips with curry sauce, my street cred only saved by the use of a shopping face covering.

So the problem is solved; two new Yuasa AGM 36Ah batts and the old rocker is rocking again...ride hard, die fast (or coughing, if the new strain gets him).
Much obliged for all your contributions.

Case closed....er, that's case, not cask.

MM

 

[Harry Bloomfield]

I've tried to follow this thread, no really I have, but I have concluded that the old batts are dead - long live the new batts! Fitted and working I faced the ignominy of driving a 4mph (max) mobility scooter 5 miles in driving snow and pelting rain (I'm tough, but don't let that cloud your judgement) to prove the scooter's range.

Impressed with the stamina - Yours, as much as the scooter.

I have one here and used it on occasion, it's tad faster than either walking or waiting for the bus when I collect f&C's. It was my partners, before she passed away - I kept it because they cost a lot, but fetch almost nothing used. I accidentality left it turned on once for weeks and flattened the batteries, but managed to maybe recover them - they hold a charge and charger only runs for minutes before showing fully charged, plus it runs around the garden fine. I am though worried about taking it out, in case the batteries let it down more than a few yards from home - Its too heavy to push on my own and I would not fancy just leaving it, whilst I nipped home for the car to collect it. It will come to bits with a bit of effort, to go in the boot.

My plans are to either ask if I can leave it safe in someone's drive, whilst I nip home for the car, or phone SWMBO (who cannot drive), to bring a short rope and between us we could tow it home if not too far.

 

[MeldrewsMate]

I am though worried about taking it out, in case the batteries let it down more than a few yards from home - Its too heavy to push on my own and I would not fancy just leaving it, whilst I nipped home for the car to collect it.

Come on Harry, be serious.
Forwards 1/4 mile, home 1/4 mile.
Repeat.
The farthest you'll be stranded is 1/4 mile.
Most, if not all, have a disconnection lever that lets you push it easily.
Modify your route if hilly.

My route was several times around the block...snot rocket science.