Hi guys can i charge lead acid battery with 12v 5a adapter?

 

Hi guys can i charge lead acid battery with 12v 5a adapter?
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NO you cannot. To charge 12V battery, you need more than 13V power supply. Also you need to limit the charging current, 5A heavy current kills the 7AH battery too fast.

 

Hello,

Read this page about charging:
https://www.batteryuniversity.com/article/bu-403-charging-lead-acid/

Bertus

 

NO you cannot. To charge 12V battery, you need more than 13V power supply. Also you need to limit the charging current, 5A heavy current kills the 7AH battery too fast.

Ok can u give me a simple charging circuit

 

Hello,

Have a look at this post for a charger circuit:
https://forum.allaboutcircuits.com/...-using-15v-1-5amp-source.156877/#post-1356928

Bertus

 

Ok can u give me a simple charging circuit

I've designed circuits for charging SLA batteries. Eventually, I came to realize that a commercial battery maintainer was more trouble free. The benefit is that in addition to charging and maintaining batteries, it can also recover some of them.


I had a 12V/7Ah SLA in a UPS that recently "failed". I put it on the maintainer and it restored the battery enough that the UPS stopped alarming. Still replaced with a new battery because I want the UPS to have its full runtime capacity restored.

 

I am going with the above or just a simple Google of 12 Volt battery maintainer. I also discovered it was cheaper to buy verse build. You also need at least 13.6 volts, as mentioned, to charge a 12 volt SLA battery.

Ron

 

Hi guys can i charge lead acid battery with 12v 5a adapter?

you need a small boost converter to give you 14.7V at 1.4A and reduce to 13.6V for float charge.

 

I use a bench power supply set to 14.5 - 14.8 V.

 

Hi guys can i charge lead acid battery with 12v 5a adapter?

Almost certainly, no, as everyone has mentioned. You need nearly 14V at the supply to properly charge a 12V battery. By the time the unloaded voltage of a battery has fallen to 12V, it's nearly "dead". Said another way, charging a lead acid to just 12V is gets it to a better place than any lower voltage, but it's far from charged.

However, it depends on your adapter. In the old days, before widespread SMPS, a 12V nominal wall wart might output 16VDC or so when unloaded - at low current - and will only be drawn down to 12V when under the stated load. This behavior made it acceptable for charging a lead acid battery. Higher current while bulk charging, low current once charged. Not ideal maybe, but it could get the job done.

A commercial, off-the-shelf battery tender can be very inexpensive. In the realm of make-or-buy decisions, it's a very strong buy.

 

https://aliexpress.ru/item/10050129....productlist.search_results.10.662d7bf1AlHzVW

 

If you already have a >2A, 15-20Vdc souce (such as from an old laptop or bench supply) you could use this LDO charging circuit (LTspice sim below), which performs the three desired lead-acid charging states of: constant-current bulk, constant-voltage absorption, and constant-voltage float charge.
M1 will need to be on a heatsink; size depending upon the supply voltage used.

But as noted, it's likely easier (and probably cheaper) just to buy one of those low-cost chargers available for that.

 

Since we know nothing about that "12 volt 5amp adapter", we have not enough information. I have one 12 volt adapter with a "no-load" output of 15 volts, that drops to 12volts with a 400mA load. Certainly a scheme to limit the current (see post #10), if you would be able to build it.
If the adapter voltage is actually 12.0 volts no load, then you can do some charging and the current will drop rapidly as the battery charges. But you will not get close to a full charge.

 

If all else fails, read what it says on the battery.



When charging, start with something between 14.5 V and 14.9 V, limiting the current to no more than 2.8 A.
When floating it (maintaining it), use something between 13.6 V and 13.8 V.