SLA charging questions

[roadstar]

Hi,

I’ve just bought 3 yuasa rec14-12 lead acid batteries as a stop gap measure until I can get li-ion.

My SLA charger when charging has a red led which goes green when the battery is fully charged (so the charger reads). I’ve been told I should leave the charger running for 8 hours even if the battery light goes green after its been on for a couple of hours (which is normally the case after a 5 mile ride). I just wondered if this was true?

My chargers a cheap 1.5 amp 36 volt charger.

The other question is how low can I allow the voltage to go during a ride without battery damage?

I rode for about 5 miles and checked the voltage and it had dropped from 39.5 volts down to 38 volts – the battery had not lost any of the indicator lights on the throttle.

Thanks in advance

 

[amberwolf]

Usually 12V per battery is a good stopping point for longer lifespan, and running them down to 10V can shorten lifespan a lot.

For your particular batteries, you should check the manufacturer spec sheet for charging rates, discharging rates, and voltages/etc., to be sure of the right numbers. Yuasa should have that on their website.

 

[e-beach]

Hi,

I’ve just bought 3 yuasa rec14-12 lead acid batteries as a stop gap measure until I can get li-ion.

Did that my self when I built my first e-bike

My SLA charger when charging has a red led which goes green when the battery is fully charged (so the charger reads). I’ve been told I should leave the charger running for 8 hours even if the battery light goes green after its been on for a couple of hours (which is normally the case after a 5 mile ride). I just wondered if this was true?

How often do you ride? If you ride only once a week, charge them and then disconnect them from everything. Then put a charge to them just before you go riding. If you ride every day like I do then I would just leave the lead acid batteries attached to your charger all the time. For a full charge lead acid batteries need to have a float charge which comes at the end of the charge so that they are as fully charged as possible. Unlike lithium batteries they do not need a balancing period so leaving them on the charger for 8 hours is not really necessary. You really have an option. Either leave your lead batteries on the charger until the charger light goes green then disconnect them from the circuit, or leave them on with the float charge going until you use them again.

Just don't store your lead batteries at a low state of charge. They won't last long if you do that. So keep them topped off when not in use.

It is recommended to charge lead batteries as soon as possible after you are finished with your ride.

The other question is how low can I allow the voltage to go during a ride without battery damage?
I rode for about 5 miles and checked the voltage and it had dropped from 39.5 volts down to 38 volts – the battery had not lost any of the indicator lights on the throttle.

You can ride lead acid batteries until your controller cuts out without worrying about your lead batteries. They are robust that way. Just be sure that you are close to home when you run out of juice or you will be working to pedal a heavy bike home.

Edit: Yuasa Battery Basics

 

[dogman dan]

With lead, it should not harm them to leave it on the charger awhile after done. Like if you put it on the charger at dinner, it takes 5 hours to charge, you don't have to jump out of bed to unplug it.

But once it's green, I don't think there is any real benefit to letting stay on the charger longer. It's full, and does not need a lot of time to balance like lithium does.

 

[roadstar]

Thanks for the advice everyone

 

[999zip999]

I unplug batteries from system when not in use. Batteries should be charged once a month always. Sla losses charge when sitting. I wouldn't drain to cutoff. How many miles do you get when drain to 36 volts ? You batteries would be lower under load you are checking voltage after load.

 

[DrkAngel]

At a 1C discharge rate, chart shows 11V as maximum, reasonable, discharge under throttle.
Other maximum discharge under various discharge rates can be derived.

105Ah 12V deep cycle battery

Common knowledge rates 10.5V as empty! Don't go there!
Stay above 11.5V static voltage and recharge immediately after use.

Quality of charger determines use.
If quality unknown-questionable
Charging after light turns green is not necessary and might be inadvisable
At room temperature, SLA charge voltage should not exceed ~14. 2V
Float voltage between 13.5V - 13.8V
Check full charged voltage a reasonable time after charge terminated ...
"Full" charge is reasonably near 13.2.

See Lead Acid Woes

 

[999zip999]

If batteries are hot let cool down before charging. Sla don't like hot. Yes they do get warm. So charging keeps them cool. 4 sla's together make more heat when charging higher charge rate more heat.

 

[DrkAngel]

Found a very informative Manual from a battery Manufacturer.
SLA Battery Technical Manual