Topic: SLAs and soldering... heat issues.

[F.O.Bean]

its just saying, when your batts are disconnected from the charger, ie: standby, they should show a voltage NO lower than 13.5 volts, and when charging, they should NOT show a voltage no lower than 14 volts

tahts a pretty high standby voltage IMO, especially considering its a 12v

i think mines like 10.5 or something

[Lil Kim Jong-Il]

And there is info about voltage regulation for standby use and cyclic use

Standby: 13.5-13.8V
Cyclic: 14.0-15.0V

What can I make of those voltage quantities?

Bean, that "standby" voltage is not the voltage on the battery terminals when it is disconnected from the charger.  It is the voltage that the charger puts across the terminals when it is not in the charging state but is maintaining the battery. 

Smart chargers typically have two modes: charging and standby.  The higher voltage drives charge into the battery and the lower voltage (standby) just maintains the battery in the charged condition. The shelf voltage (disconnected from charger and load) is usually higher than 12V when fully charged and then when loaded it works it's way down. 

Those voltage ranges are standard for a 12V SLA battery charging and maintenance.

If you can't find the sheet for your battery, go to Yusa or Powersonic and look at the specifications for their 12V SLA batteries.  The discharge curves will be similar and you can use the numbers safely for your test.

[aberg]

Thanks teabag, and +T to you and bean... and anyone else I can see that gave me a good hand here... I'm going to pick up a new SLA and using a circuit propsed in a different thread, attempt to revive my old one.. if it doesn't work, well... I've got a new SLA anyways... I'll be a little smarter about charging and discharging now. hehe. Thanks guys!

[jk labs]

Ok, I think I get what you're saying... unfortunately, I don't have a multimeter right now to see if my charger is even supplying a voltage to the dead SLA.. I will pick that up and then chances are it's the type of charger in question, which doesn't supply voltage to a dead battery. What you're saying to do then is to use the new SLA as a charger itself and then put a light bulb in series to act as a sort of current regulator/fuse type of thing... why would the charger need to be connected to the good SLA though?

"What you're saying to do then is to use the new SLA as a charger itself and then put a light bulb in series to act as a sort of current regulator/fuse type of thing"

YES. And the bulb is a visual "current is flowing" indicator. Very useful when working with batteries.

The charger is there to make sure the battery delivering charge is not at risk of being abused.

Jon

[jk labs]

If I remember right most chargers have indicators for faults and automatically won't send a charge if there's a short.  A dead battery may seem like a short to the charger so....it won't charge.  The extra load kinda tricks the charger into continuing outputting voltage in hope that your battery will eventually accept the voltage/charge.

... snip

My advice.....your battery is junk.  Even if you can revive it it won't have the capicity or reliabilty you want.  Find your local electrical supply house and buy a new one....usually less than $20.

But the battery was new if memory serves. Even the crappiest of SLA chemistries should survive ten deep discharges. If one assumes a linear loss of capacity that translates into 10% loss in capacity per complete
discharge (which I think is about right for flooded car batteries).

Jon

[aberg]

Yeah, my plan was to try your method of reviving it tonight... how long should I keep it attached to the charging circuit? Until the voltage across the terminals is higher than the cut-off voltage, which I'm assuming to be about 8.10V, on par with power sonic SLAs...? Does that sould right? Then once it's above that voltage, it should be able to accept charge from the charger as per normal?

[F.O.Bean]

id like to do this too to save a 12v 7 amp battery i have

so exactly ghow does one run parallel w/ the good sla

would/could you just hook up an xlr in one to an xlr in the other

[aberg]

Excellent!!! I got a new SLA, and a multimeter and a 12v bulb.. and rigged up that propsed charging circuit... before doing so, I checked the voltage on the dead SLA and it was under 6 volts... well below the 8.1v final voltage listed for SLAs by powersonic so right away that's obviously the problem.. anyways, I rigged up the circuit and it took about 20 mins or so before it would accept a charge with the charger and now it's charging fine... it's up at like 11.9v... the only weird thing that happens is that when I take it off the charger, and then check the voltage, it slowly decreases.. like it drops by 0.1v every couple of seconds... is this normal?

[leegeddy]

Excellent!!! I got a new SLA, and a multimeter and a 12v bulb.. and rigged up that propsed charging circuit... before doing so, I checked the voltage on the dead SLA and it was under 6 volts... well below the 8.1v final voltage listed for SLAs by powersonic so right away that's obviously the problem.. anyways, I rigged up the circuit and it took about 20 mins or so before it would accept a charge with the charger and now it's charging fine... it's up at like 11.9v... the only weird thing that happens is that when I take it off the charger, and then check the voltage, it slowly decreases.. like it drops by 0.1v every couple of seconds... is this normal?

you should charge your SLA overnight and see what the voltage is. it should be over 12v since many 12v-rated chargers output over 14v.

marc

[aberg]

yeah, that's what I'm doing now... we'll see what happens in the morning.

[jk labs]

Excellent!!! I got a new SLA, and a multimeter and a 12v bulb.. and rigged up that propsed charging circuit... before doing so, I checked the voltage on the dead SLA and it was under 6 volts... well below the 8.1v final voltage listed for SLAs by powersonic so right away that's obviously the problem.. anyways, I rigged up the circuit and it took about 20 mins or so before it would accept a charge with the charger and now it's charging fine... it's up at like 11.9v... the only weird thing that happens is that when I take it off the charger, and then check the voltage, it slowly decreases.. like it drops by 0.1v every couple of seconds... is this normal?

Such a drop in the measured battery voltage is to be expected. Your are literally stuffing huge amounts of charge into the battery every second and the battery accumulates this charge by sending charged ions into the aquatic solution. It's a diffusive process and it just takes time.

I.e. if you remove the charger, the voltage will drop as a function of time. 

You see this at the end of the charge cycle also where ballpark numbers for this drop is 0.8 Volts on float charge and about 2 Volts when terminating cyclic charge (assuming the fully charged SLA has a no-load voltage of 12.80 Volts). A less than full battery will drop more.

Regards
Jon

[aberg]

Ok, that makes sense.. thanks! I think they're both working fine now... got the dead one workin' like a charm now.. it's still maintained the same capacity as the brand new one so we're definitely in business. Thanks!

[dklein]

Nice save JK! +t