Split Charging, can I use Sealed Lead Acid batteries?

**fitzy75** · 11-25-2008, 08:09 PM

Hi

Hope this is the right forum to post in

After suffering a couple of flat battery situations on my car, I have been looking into better ways to power my equipment.

I'll start by describing my current situation: I do computer repairs and sometimes end up fixing customers laptops while in my car. I currently ran a 150watt inverter to power a 15 inch lcd monitor, the laptop and anything else such as a mains powered external hard drive. The inverter copes with it fine but the car battery does limit it quite a lot.

I sometimes run the inverter from a 12 volt sealed lead acid battery which is connected independent from the car. The battery is 12v 14Ah and it provides me with about 2.5 hours run time. The problem with this is that I currently have to take the battery into the house and charge it up on a normal battery charger each time which is inconvenient.

I have just acquired a large number of 12v 7Ah batteries and I was thinking of connecting them up parallel to each other and then implement a split charging system on my car so that they will charge up when the engine is running, so I am looking for some more information about weather this would be possible or not.

Is it a good idea to have sealed lead acid batteries charging from a standard car alternator circuit or would I need some sort of charge controller/circuit to stop them getting overcharged/wrecked too quickly?

Any ideas or suggestions would be welcome

Thanks,
Rob.

**mayhembdm666** · 01-18-2009, 12:16 AM

I dont normally bump and have not yet ever bumped a post... but
BUMP
I would also like to know if someone has a already made circuit design. I do know that if you just run it in parallel from the car alternator.. The car battery will destroy the 7ah battery and when charging it will always charge the lesser battery.

I was myself wondering about a simple detector circuit that uses a cheap kit which will read the voltage and throw a switch when it drops below say 12v and turn of when at say 12.5

This can be done with a simple led indicator kit, But just have not had time to get around to it yet.

**insaneramman** · 01-19-2009, 09:27 PM

I too have been thinking of a small tank battery for my truckpc. I saw a trailer brake battery set-up that caught my eye. It uses a small battery to assist the electric brakes on a trailer, comes with its own little charging box so it wouldn't be affected by your alt. or drain your main battery. This is much cheaper than an isolater and a seperate battery.

**julaikos** · 01-22-2009, 03:39 PM

a Schottky_diode between the car battery and the 12v7Ah battery will do just fine to recharge "the little one"
you cand find one in the atx power supply (an example to220) connected in series with the battery