How to check the condition of a battery?

Hello Guys,

I have bought a simple E-bike moped for my mum when my dad passed away, in the hope it would be easier to handle than a car.
http://titanzero.se/titan-zero-r2-1000w-25-45-km-h/

However, after two years of use, my mum complained that the power is decreasing in the battery.

The moped has not been used for several months now and this last weekend I disassembled the battery pack, 6 batteries 12 V, Five of them gave approx 10V before I put them back and tried to charge them. But one battery gave 0V.

I started to charge and the battery charger stopped charge after just 1 hour. Normal charging use to take 8 hours.
After that, I only measured approx 64V all batteries together. It should be 72V.

However is it possible to disassemble the battery pack again and try to charge each battery with a normal car battery charger to see the condition of each one of the batteries? Or do you guys recommend some other way? Perhaps a normal car battery charger will "break" this kind of battery?

My suspicion is that at least one of the batteries is so bad so it must be replaced. If I'm lucky perhaps five of them are still good to use. But I need to find out in some way.

What do you think guys?
Best regards
Fredrik

it's likely that all of them need to be replaced at the same time.

you didn't say what kind they are, but if they're 12v bricks they're probably lead-acid, probably sla or vrla, and those don't usually last more than a few months to a year anyway, especially if they are not always kept charged when not actually in use (or if left on a charger that overcharges them / keeps pushing current into them when full). anytime lead-acid batteries are left sitting, they tend to self-discharge and die. the damage done to them by leaving them even partly discharged for any length of time is usually permanent.

one way to test them is to charge them individually with an sla or vrla charger like the one that came with the scooter, but at the "12v" (really more like 13.6-14.4v, whatever it says on the side of the batteries). a car battery charger is designed for a different kind of lead-acid battery, and may be able to damage this kind--it's also probably not adjustable current, and you don't want to use too much current to charge these--no more than it says on the side of them. (whatever it says on your charger works, too). so while you could use a car charger, it may make them worse.

then hook them up so the scooter can run on them, if it will, and hook up a voltmeter on dc volts to the first one, and start riding while watching the meter. if it's voltage sags (drops) very much (say, 2-3v), it's probably toast. move the voltmeter to the next one, and test that the same way.

a more comprehensive test requires a wattmeter, and a load you can test each one separately with that's comparable to the load the scooter places on them (probably 20-40a).

but realistically, they're probably all bad enough to need replacement, and even if some of them are still usable, the system will perform better, for longer, if they're all replaced with a matched set of new ones.

you can also replace them all with a lithium pack, whcih for the same size and weight will have a lot more range, and probably won't cost that much more, especially when comparing to the lifespan and range you'll get out of it, since instead of a year or two, you should get five or ten years out of it, as long as it's good quality to start with (not a "random chinese site" pack).

Hello Amberwolf,
Thanks a lot for that information! That helped me a lot. You are right, the batteries are lead-acid. The best photo I got is this:
https://drive.google.com/open?id=1DXP9JGmt9xRoEBLZ3VxWtgAoCeuoueZR
They really look like the size of a brick.

I will look into what a sla and vrla charger is, never heard of that before. I was a bit afraid that a car charger could damage the batteries even more. So thank you for pointing that out.

I now think that the best idea is to replace them all with lithium batteries. Do you got any idea of a good site that sells batteries of good quality? (The reseller of the scooter sell batteries from China he told me, so perhaps I should check out the options)

Best regards
Fredrik

the one potential advantage of getting them from the seller of the scooter is they will *probably* fit inside it where the others went. (but there's no guarantee of that; many sellers have no idea what they sell and have random stuff that doesnt' work together).

but it's also likely they're not very good batteries (possibly better than the sla); most of the common chinese ebike/scooter batteries are low quality cells (so they don't output power as well as beter cells, and don't last as long), not matched cells (so they don't stay balanced very well).

but they're a lot cheaper than higher end prebuilt packs. depending on the capacity you want, and the volume you have available (and it's shape), it could be from a few hundred dollars to well over a thousand for a good prebuilt pack. em3ev is the only place i've had direct experience with their products that custom makes batteries i'd trust, though the one i have is several years old now it still works; hasn't had any problems. ther'es others that people have had good luck with if you look thru the "where do i buy a battery" type of threads around the forum.



a compromise is building your own, using used large-ev cells, like those out of a scrapped nissan leaf (available tested used from several online scrappers, for instance), or like the eig cells zero motorcycles used in their bikes several years ago (the same kind i've been using on my ebikes for several years) (jimbob01 in the uk is selling some if you're located over there, if not the shipping cost is probably too high to be worth it). the eig cells just bolt together with busbars or similar, and leaf cell modules can also be bolted together that way. ther'es others but not as easy to use.

you can also build one from 18650 or similar small cells but that's a complicated process requiring investment in tools and hardware and significant time learning about options and methods to decide how you're going to do it, and what you're going to build....

sla and vrla are just two of varieties of lead acid, that use a gel instead of a liquid inside, so they are sealed and can't be refilled as it evaporates. fla are car type batteries, and use a liquid that can be refilled when it evaporates.

FWIW, she did real good getting two years from lead. So replacing them with similar lead will work fine for her.

Look at the code on the side of the battery, and try to source the same type. EV type lead weighs more, and costs more, so beware of a bargain cell that looks the same, but is too light and cheap. They won't last.

how to check condition of battery?
run discharge test, of course you need equipment namely battery analizer or do it with light bulbs as a load.
you should be able to calculate Ah or Wh on discharge.

Hello,
First, thanks for all comments and help!

I finally bought a CTEK-charger. Just one of my six batteries passed the tests provided by the charger. However, even though it passed I can see that the voltage drops pretty quick after a couple of days.
So I guess all of these batteries are best sent to the garbage recycle center.
Best regards
Fredrik

Hello again,
What do you think guys? I guess these old batteries can not be saved? Since my new once was pretty expensive I just would make sure there is no salvation or use for the old once.
They do not accept any charge more then 9V and they drops down to 3V in a couple of days.
Some do not accept charge at all.
Best regards
Fredrik
There seems be no way change the acid, it is probably gel inside.

Here is a photo:

yes scrap

pay more for true deep cycling batteries

Even then they need precise care to get to a couple hundred cycles

Thanks for your help.
Best regards
Fredrik

You can find automotive-grade lithium batteries from scrap or used electric cars yes you know it's based on Sweet Summer very easy to put together some are more difficult. But lead is an old technology that works but wears out quickly. Basically lead is dead.