Charging rate of an lead acid battery.

[jbevuk]

Hi. I have got an 12v .7ah sealed lead acid battery. I was wondering what the recommended and maximum current I can charge it at please?

Thank you for any help.

[xygax]

Manufactures will all say between c5 and c10 so that's between 0.7 and 1.4A

Steve

[helimadness]

Here is a good article. I guess depends on your charger. My lipo charger with do lead acid batteries I think. PB batteries I think it is labeled as??
Fast charging of sealed lead acid batteries.
How to charge sealed lead acid batteries.

My questions is how fast can you Discharge them?

Cheers

[xygax]

Discharge curves are published for lead batteries down as low as 60s by most manufactures faster than that you have to look at the internal resistance and prospective short circuit current typically for a lead battery is ten to fifteen times the capacity so a one hundred Ah battery will give 1-1.5KA into a short circuit
Steve

[helimadness]

Also found this. Page 7 has a fairly good chart. Looks like the higher the discharge rate the less capacity you get out of it. Looks like the higher discharge rates drop the voltage which would kill the efficiency
http://www.battery-usa.com/Catalog/N...Rev0500%29.pdf

[xygax]

Exactly that's because the plate and intercell resistance comes into play typically for a short term discharge you would use an end of discharge voltage of 1.55 - 1.6 VPC where on a longer term discharge you would expect to use 1.7 - 1.85 VPC
the shorter the period the greater the chance of buckling the plates this shortens the life of the battery


Steve

[helimadness]

Cool thanks.
Was just looking as I have a 12v 4.2 amp SLA battery and was wondering if I take it flying I might be able to charge one lipo (6s 2600 mah) why I use my other 4 and get one extra flight a day. Cheaper than buying more lipos. could charge at 1C I think would be the max time It would take to use 4 batteries.
I think its going to be very marginal but. Might need a bigger one. Or another the same and go 24v

Sorry for the thread hijack. Hope its all relevant.

Cheers

[cjcj1949]

The max charge current is usually on the battery. It's important to limit the end of charge voltage to between 14 and 15V. Most lipo chargers will do this ok. Old car chargers are not so good. People used to use constant current charge which is not a good idea. The main problem with field charging is that the volts drop quite low at moderate currents. A 17AH battery is usable for 5A charging. It does need to be a good battery as well and not just an old car battery. Some chargers cut off at 11V and others are programmable down to 10V which helps with higher currents and long leads. You need to recharge the 12V battery as soon as you get home as they sulphate if left uncharged.