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How do i charge a LEAD ACID battery.

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jpanhalt

Well-Known Member
Most Helpful Member
Here are three good sources for not too technical information. The DOE also has a lengthy document on lead-acid batteries, but it is quite technical. As you read technical papers, you may may find reference to lead peroxide. That is actually a misnomer. The compound is PbO2. It can be referred to more accurately as lead dioxide or lead(IV) oxide (Pb(IV) oxide).

Battery Chemistry Tutorial and FAQ from PowerStream: Custom battery chargers and power supplies for OEMs

Deep Cycle Battery FAQ

Welcome to Battery University

The last two links discuss most battery types. You can search on lead-acid batteries.

Chargers are quite plentiful, as you know.

John
 

AtomSoft

Well-Known Member
wow lead acid seems really simple to charge.

I just mainly have to monitor voltage levels and keep a steady voltage until it reaches a certain level (voltage) then remove power or stop charge until it drops and when it does just turn charge back on.

This way i can leave it charging for a long time and not have to worry about the discharge issue.

Ok now for the technical part. Ill make a new topic in Micro section...


Thanks guys!!!!
 

k7elp60

Active Member
You can float charge your battery @ 13.5 to 13.8V with the charger connected at room temperature and never overcharge the battery. Powersonic in their technical data book recomends that the charge current be limited to 0.2 times the capacity. For you 7AH battery that would be 1.4 amps.
I have been building chargers for 12 7AH gel-cel batteries for more years than I can remember. If you would like to build one I can post schematics for several different ones. One uses a LM317T, another one uses a PB137 IC that was designed for that purpose. This one requires no adjustment with a DVM.
The LM317T one has an added circuit that senses when the battery is charged and turns on an LED with the battey is charged. This one requires two adjustments, one for charge voltage and one for charge indication.
 

bountyhunter

Well-Known Member
wow lead acid seems really simple to charge.

I just mainly have to monitor voltage levels and keep a steady voltage until it reaches a certain level (voltage) then remove power or stop charge until it drops and when it does just turn charge back on.
Nope, that's not the best way for lead acid. You keep the charger on all the time and just hold the battery voltage at 13 - 13.2V. That prevents sulphation. Letting a lead-acid battery sit with no charging going on can lead to death over time.
 

bountyhunter

Well-Known Member
You can float charge your battery @ 13.5 to 13.8V with the charger connected at room temperature .
I think 13.8V is good for a car battery's charging system where you want to replace lost charge quickly, but it's a bit too high for continuous float charging. Check the manufacturer's spec sheet, they always recommend a lower cell voltage for float charging. I use 13.2V for my motorcycle charger to keep it charged all year round and I get about 8 - 10 years life out of the batteries. Float charging to a higher voltage like 13.8V will boil the water out faster and require more topping off.

Float Charge: The 3rd stage of 3-stage battery charging. After batteries reach full charge, charging voltage is reduced to a lower level (typically 12.8 to 13.2) to reduce gassing and prolong battery life. This is often referred to as a maintenance or trickle charge, since it's main purpose is to keep an already charged battery from discharging.
https://www.solarnavigator.net/battery_charging.htm
 
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k7elp60

Active Member
I think 13.8V is good for a car battery's charging system where you want to replace lost charge quickly, but it's a bit too high for continuous float charging. Check the manufacturer's spec sheet, they always recommend a lower cell voltage for float charging. I use 13.2V for my motorcycle charger to keep it charged all year round and I get about 8 - 10 years life out of the batteries. Float charging to a higher voltage like 13.8V will boil the water out faster and require more topping off.

LEAD ACID BATTERY CHARGING INFORMATION, BATTERY TYPES AND OPERATION - SOLAR NAVIGATOR WORLD ELECTRIC NAVIGATION CHALLENGE, NELSON KRUSCHANDL, BLUEBIRD ELECTRIC LAND SPEED RECORD CARS
I base my remarks on the attached PDF, page 10 to be specific.
 

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audioguru

Well-Known Member
Most Helpful Member
I have a hunch that AdamSoft wants to charge dead lead-acid batteries that are suphated because they have been discharged (due to self-discharge) for years.

It ain't gonna happen. The batteries are ruined.
 

jpanhalt

Well-Known Member
Most Helpful Member
Here are the DOE documents I mentioned earlier. They are lengthy. DOE spends billions a year, so get your money's worth.

In this document, there is a nice table on page 20 (of the document, not pdf page) that tells about float charging.

This document describes some of the dangers of overcharging, including production of poisonous gases from batteries that have been modified with antimony, tin, and/or selenium.

I agree with AG. If you are trying to bring back to life batteries that have sulfated, forget it. Also, if the batteries you are dealing with are "sealed," some of the maintenance procedures, particularly with respect to float charging, are different than for flooded, open lead-acid batteries. The DOE documents discuss both types.

John

John
 

bountyhunter

Well-Known Member
I base my remarks on the attached PDF, page 10 to be specific.
Yeah, there is a divergence of recommendations for float charging. I have had best luck with keeping the voltage at the more conservative end (13.2). Float charging at 13.8V probably won't kill a battery, but it does increase gassing compared to 13.2V and I personally don't think you need to do it.

I suspect they went to a higher recommended voltage so that the chargers don't have to have built-in temp compensation. Lead acid 12V batteries have approximately -20mV/C tempco and the charger should track that. If it doesn't, the battery can be undercharged at cold temps where the battery voltage goes up but the charger doesn't follow. I use temp compensation on my charger so I can set it just a shade over the voltage it takes to keep the battery peak charged and I know it will always be right regardless of temp. Anyway, it's worked well for 25 years.
 
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bountyhunter

Well-Known Member
Here are the DOE documents I mentioned earlier. They are lengthy. DOE spends billions a year, so get your money's worth.

In this document, there is a nice table on page 20 (of the document, not pdf page) that tells about float charging.


If I read page 20 right:

Cell Float Voltage

(2.15-2.17) volts PbSb

A "12V" battery has six cells, so it would come out to 12.9V - 13.0V for float charging. That's probably what I was remembering when I recommended 13 - 13.2V initially.

It is slightly different for a different battery type:

(2.17-2.25) volts PbCa

Which would be 13.0V to 13.5V
 
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AtomSoft

Well-Known Member
heh these are brand new batteries. I own 2 and i had a few customers come into my job at radio shack asking me where to get a charger and why dont we sell them.

So i decided to buy a couple and try to make a charger on my own and see how much it cost compared to commercial chargers then if possible create them and sell them outside/apart my job. Will be sold with no warranty/guarantee and has nothing to do with my job. I will sell it as cheap as possible while trying to make the money back from parts and something for time spent reading and learning this myself.

13v was my main choice. The batteries i have like a IDIOT i threw away the boxes which had a ton of info on them heh

Ill go and make a photo copy of the box at work and show you all along with my idea of how to charge it and my method and schematic and source etc...
 

AtomSoft

Well-Known Member
I think 13.8V is good for a car battery's charging system where you want to replace lost charge quickly, but it's a bit too high for continuous float charging. Check the manufacturer's spec sheet, they always recommend a lower cell voltage for float charging. I use 13.2V for my motorcycle charger to keep it charged all year round and I get about 8 - 10 years life out of the batteries. Float charging to a higher voltage like 13.8V will boil the water out faster and require more topping off.

LEAD ACID BATTERY CHARGING INFORMATION, BATTERY TYPES AND OPERATION - SOLAR NAVIGATOR WORLD ELECTRIC NAVIGATION CHALLENGE, NELSON KRUSCHANDL, BLUEBIRD ELECTRIC LAND SPEED RECORD CARS

NICE!!! thanks for link!
 

AtomSoft

Well-Known Member
on page 12 this is what made a lot of sense to me and gives me ideas :D

The recommended constant float voltage is 2.25-2.30
volts per cell. Maintaining this float voltage will allow
the battery to define its own current level and remain
fully charged without having to disconnect the charger
from the battery. The trickle current for a fully charged
battery floating at the recommended charge voltage will
typically hover around the 0.001C rate (10mA for a
10AH battery, for example.)
The float charger is basically a constant voltage power
supply. As in cycle chargers, however, care must be exercised
not to exceed the initial charge current of 0.20
x C amperes.

The box for batteries show initial current info and stuff so when i get it ill post my hypothesis on this...
 
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Sceadwian

Banned
The stupidest simply method to charge a lead acid cell is the same method a car does. When the engine is running it outputs 13.8VDC. Attach a 13.8VDC regulated supply when not in use and you're all set. You can get more complicated, but it's primarily for more deeply discharged batteries.
 
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audioguru

Well-Known Member
Most Helpful Member
The stupidest simply method to charge a lead acid cell is the same method a car does. When the engine is running it outputs 13.8VDC. Attach a 13.8VDC regulated supply when not in use and you're all set. You can get more complicated, but it's primarily for more deeply discharged batteries.
No.
Most cars charge the battery at about 14.4V. But the voltage is temperature compensated.
 

Sceadwian

Banned
Why 14.4v? Doesn't that cause excessive gassing of the battery?
 

MikeMl

Well-Known Member
Most Helpful Member
The stupidest simply method to charge a lead acid cell is the same method a car does. When the engine is running it outputs 13.8VDC. Attach a 13.8VDC regulated supply when not in use and you're all set. You can get more complicated, but it's primarily for more deeply discharged batteries.

The voltage on modern cars is more like 14.4 to 14.5V. However, they get by with this on the assumption that the car is running less than two hours per day. A flooded-cell, lead-acid automotive starting battery left on a constant-voltage charger set to 14.4V will be junk in a week (due to overcharge). 14.4V is ok for recharging, but you have to lower the voltage to a float voltage of 12.9 to 13.2V after the initial charging current drops below a few hundred mA. A flooded LA battery can be floated indefinitely at 12.9 to 13.2V.

Sealed AGM (VRLA) batteries are to be charged at 14.4 to 14.8V, and floated at 13.5 to 13.8V, adjusted for ambient temperature.
 
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