Single battery dual battery set-up

[chimpboy]

Does anyone use a dual-battery controller with a single battery? ie, one big battery, a cut-out at about 12.1 volts, and accessories on the other side of the cut-out?

Just wondering if anyone sees merit in this, not so much for hardcore use but to make sure that a few accessories you are inclined to keep running with the engine off, like radio or CB or whatever, can't take your battery beyond a sort of minimal cranking power level.

Any thoughts?

[drivesafe]

Hi chimpboy, thats actually a common set up.

Quite a few people use that for running fridges and inverters and as you posted, CBs.

Our smallest dual battery controller works well in this sort of set up because of the low power requirements of the controller ( 120ma ) compered to other devices ( which usually draw between 500 to 900ma ) means the controllers themselves don’t use up all your power just to power the controller.

We have had that much calling for this type of device that we are in the process of developing a new unit that will only draw about 60ma.

[Goatse.AJ]

Sounds good. I'm interested

[chimpboy]

Hi chimpboy, thats actually a common set up.

Quite a few people use that for running fridges and inverters and as you posted, CBs.

Our smallest dual battery controller works well in this sort of set up because of the low power requirements of the controller ( 120ma ) compered to other devices ( which usually draw between 500 to 900ma ) means the controllers themselves don’t use up all your power just to power the controller.

We have had that much calling for this type of device that we are in the process of developing a new unit that will only draw about 60ma.

I thought yours might do it actually, and was hoping you'd chime in.

I was going to pull my Matson dual battery controller out of my Maverick before I sold it, but it sold very quickly. I think I was a bit cheap. But anyway... now I am setting up the new vehicle so I am just mulling over how to set it up. It has a bit less free space than the Maverick did and I am not sure I really want a big fat second battery in it. I am wondering about just having a very good primary battery and some protection as described.

I hadn't heard of people doing it but I guess it is pretty obvious really.

[festy]

Yes, I've set up a VSR as a low voltage cutout.
Using the Oatley dual battery kit, the instructions tell you how to set it up and even comes with the alternate value components to change the cut in/out voltages to suit this application.
http://secure.oatleyelectronics.com//pr ... 9566c56369

If you're short of space but still want some capacity for accessories, you could probably stuff one or more 19Ah SLA alarm batteries in somewhere and use them in parallel as an aux battery.
I've got 2 lots of 6 that I use for extra capacity, an additional 200Ah never goes astray

[stuee]

I'm building this feature in to my own dual battery controller. I'm basing it around a microcontroller and it also has functions to control thermo fans and give me some basic engine parameters such as temp, voltage, oil pressure etc.

Basically the micro will control a solenoid controlling connecting my two batteries which acts as a normal voltage sensing dual battery controller, it also has control over a relay (or solenoid depending on required draw) which separates the accessories running off the second battery. When it senses the second battery is at a low voltage it will cut off the relay connecting the accessories preventing the battery completely discharging and damaging itself. I'm also going to run a small 12v battery recharged by the accessory outlet of the second battery which will act as the power supply for the micro so that it doesn't run down either of the main batteries. And when everything is flat I will have mechanical override switches and jumper leads to get me going again

Why am I doing this?? Because it gives me a semi cool excuse to keep playing with microcontrollers now that uni has finished (because I only get to play with industrial control systems at work)

[Spimon_NH]

Had a little trouble digesting the notes with the Oatley Dual Battery Kit.

From what I understand, with this kit the alternator recharges the primary battery. When the voltage in the primary battery reaches around 13.5v it switches and recharges the secondary battery and continues until it also reaches 13.5v. Correct, yah?

What happens with discharing the batteries once the engine is switched off? Does this system isoltate the primary battery at all, or does it discharge both batteries equally?

What I want to do is connect all my auxilery accessories (camping lights, radio, UHF, compressor, etc..) to a secondary battery. When camping I want to be able to run this battery down without flattening my starting battery. Will this kit help me out, or would I need to physically isolate the primary battery with an isolator switch?

[festy]

Whenever the voltage of the primary battery is > 13.5v then the aux battery is joined. When the primary battery voltage frops to 12.6v, the aux battery is isolated.
Considering 12.6v is about the 'at rest' voltage of a fully charged battery, the aux battery is isolated pretty soon after you stop your engine. this kit will do what you want it to.

These voltage thresholds can be customised - if you want to keep the two batteries joined until the voltage drops to say 12.3v then you just set it up for that.

[Spimon_NH]

Thanks Festy
Sounds exactly what I'm after - and in a student's budget too!

[festy]

just so you're aware - it comes in kit form (what do you expect for $25) so I hope you can solder

[Spimon_NH]

I think I'll be fine

[drivesafe]

Hi again chimpboy, want to be a Guinea pig for my new unit?

If so, work out what your total current draw is ever likely to be and let me know.

I’ll take it from there.

Cheers.