best chargers - help with 12V SLA scooter batteries

[psb]

Hi folks -

perhaps one of you electrical wizards can enlighten me, or point me in the direction of info.

I have a generic electric scooter, similar to the Motorino.
I have just installed 4 x 12V @ 21 Ah sealed lead-acid batteries.

I'd like to find the best way to charge and maintain these batteries to extend their lifespan. I have studied up on best practices (i.e. charge after every use, etc.) and I must confess my comprehension of battery charging is limited. The generic charger that came with the scooter is a simple on-off: red light means charging, green means charged. I don't know if it's a cycle-charger or what. The charger connects to the bike via a three-prong connector. I have looked at the "Genius Charger" as an alternative but would have to wire directly to the batteries, which currently are housed inside plastic carrying cases.

This is my charger specs:

Rated output 48V - - - 2.6 A
Input 110V ~ 3.0 A / 50 - 60 Hz
Compatible battery set: 48V 17/20 AH

These are the battery charging specs:

Charge Methods: Constant Voltage Charge 77°F (25°C)

Cycle use 2.30-2.35VPC
Maximum charging current 6.8A
Temperature compensation -30mV/°C
Standby use 2.23-2.27VPC
Temperature compensation -20mV

IS my charger suitable?
How many hours should it require for full charge?
Would the batteries require 5 or more 'conditioning' charges to reach full capacity?

What specific charger would you recommend for my set-up, as best for long battery life?

I have seen the wiki page - http://www.endless-sphere.com/w/index.php/Charging_Lead_Acid_batteries - if there are other resources here on the forum, please point...

Thanks very much for your thoughts,
dan

 

[mettleramiel]

Well first off, let me just tell you that you will not get much life out of those batteries. My personal experience and the countless customers I have seen use SLA in scooters and powerchairs leave me with the pessimistic view that no matter how you charge them, with regular use you may get a year. Two years with some luck.

The charger you have is likely a smart charger as most scooters, even the cheap Chinese ones have some sort of smart charging no matter how rudimentary.

I don't know much about the "genius charger" but there's no reason you would have to connect directly to the battery. As long as it is 48v as well, you can just put an end on it to match the charger port on your scooter. Or you could just stick a new harness out of the battery box to match up with whatever your charger has.

The "conditioning" charges you refer to may be needed, it really depends on how long the batteries have sat on the shelf in the store for.

From completely dead the charger would take 6-8 hours to charge. I will say this, though. In my experience, the most important thing you can do to maximize the life of your batteries is to keep them on the charger at all times when not in use.

 

[psb]

Hi, thanks for the reply. Yes, I may run a new line out from the battery, good idea. I don't trust the existing charger is doing its job. The guy who sold it to me said to put it on a timer "just in case" it's not accurate, to prevent overcharging. So it's possible the charger may be contributing to battery death. Two years, OK, that's acceptable for the price if it can happen, but one year would be disappointing for the price. Would you say there is a wide variation in battery quality that would justify a higher price? In my case, I ordered online to save fifty percent of the cost.

As for 'conditioning", I'm confused - the charger may not show 'fully charged' until a few charge cycles are completed? They were sold to me as 'fully charged, with new stock shelf life' - tested last week with a voltage reading average of 13.5v written on the label. It's been 12-14 hours charging already.

 

[Laserman]

Has the charger gone green as they said the charger is a smart ie shuts down after reaching full charge and dropping to a trickle charge when completed the high charge, most chargers drop from full volt / current to about half or less of the current needed to charge the battery pack

 

[mettleramiel]

Hi, thanks for the reply. Yes, I may run a new line out from the battery, good idea. I don't trust the existing charger is doing its job. The guy who sold it to me said to put it on a timer "just in case" it's not accurate, to prevent overcharging. So it's possible the charger may be contributing to battery death. Two years, OK, that's acceptable for the price if it can happen, but one year would be disappointing for the price. Would you say there is a wide variation in battery quality that would justify a higher price? In my case, I ordered online to save fifty percent of the cost.

As for 'conditioning", I'm confused - the charger may not show 'fully charged' until a few charge cycles are completed? They were sold to me as 'fully charged, with new stock shelf life' - tested last week with a voltage reading average of 13.5v written on the label. It's been 12-14 hours charging already.

Overcharging can be seen pretty easily as the cells would be bloated. They also would only last a few months being consistently overcharged.

The only difference in quality I have seen is that they were made better 15+ years ago. Today they are all pretty crumby, but mostly the same.

Battery gauges are sometimes little liars. The batteries should be fully charged after 6 or 8 hours. Anything more than that will do nothing more. You can leave them on for 10 hours or 10 years and it would be no difference. The problem is that the charger is looking for a voltage of somewhere around 14 volts to say that it is fully charged. The battery may only be at 13.95 volts which really, is just fine. The only way to know if the battery is fully charged would be to do a proper load test on it or record how many amps are actually going into the battery every half hour or so while on the charger.

 

[psb]

Thanks.

Well, a test ride yesterday shows that the batteries are not taking a full charge after 15 hours charging. I only rode a few minutes before power rapidly decreased and became sluggish. So, what you say about the charging showing 'full' may be true - they may never read as full, but these are brand new batteries...

These are the options I see: (1) batteries faulty (2) charger faulty (3) charger does not match battery specs, so will either not charge fully, or not SHOW as fully charged (4) batteries acting as normal, need a break-in period and will gradually improve.

According to this article, SLA batteries need 20-50 cycles of exercise before reaching capacity:

http://batteryuniversity.com/learn/article/how_to_restore_and_prolong_lead_acid_batteries

Does this mean that not acheiving full range on initial charging is normal? I don't want to risk damaging the batteries by over-charging.

 

[Laserman]

If you can get access to the charge port with a volt meter while charging check the voltage being supplied and if possible with a clamp on amp meter on one input ie the - or + but not both and see what kind of charge current you are. Getting

 

[psb]

Thanks for this idea, LAserman!

 

[Matt Gruber]

need to check each battery while it is charging. if they vary more than 1/4 volt, they are out of balance, and the low need a 12v charger to bring them up. look for 14.3 - 14.5 fully charged, each. final float of 13.7-14.0