2 SLA Batts, Switched for 12v and 24v Usage

BillNole

Joined Oct 15, 2020
2
Here is my scenario...

I run two pieces of equipment off of 12v Deep Cycle SLA batteries, one requiring 12v and the other requiring 24V. I only use one of the machines at any given time, switching back and forth between the two, one after the other. I'm currently using three batteries (one for the 12v and the other two connected in series for the 24v machine...) Carrying just two massive SLA batteries is a strecth, but with three it's really more than works out well. Switching either machine to the other voltage isn't an option, to accomplish the tasks they are assigned. I'd rather work with two batteries, if at all possible.

Other than swapping battery cables back and forth, I'd like to come up with a simple manual switch to be able to throw to alternate between 12v and 24v output for the two separate machines. I'm not looking to go crazy with the electronics and am hoping to use a cutoff type setup, that's 12v/24v, or even better 0v/12v/24v. (The latter isn't necessary as each of my machines has a cutoff attached as a backup.)

My main intent is to simplify things so I don't have to carry the third battery. I won't attempt swapping cable between each as it will be an all day/all weekend situation and fatique will inevitable get the best of me and I'll accidently cross something up... BZZZZSSSHHHTTT-BANG *$&#@#)$*@!!!

Anyone have any idea?

Delta prime

Joined Nov 15, 2019
501

crutschow

Joined Mar 14, 2008
25,423
Would you want the two two batteries connected in parallel for 12V to double the 12V capacity?

Dodgydave

Joined Jun 22, 2012
9,457
Switches are ok but will be limited to the current rating of the loads, if you need high current you can use auto relays.

RIKRIK

Joined Oct 11, 2019
107
Id say go down the switch route as you can make sure each battery is being discharged equally. I would probaby use 2 dtdp switches. i did have a go with one but the diode idea, im not 100% :/

BillNole

Joined Oct 15, 2020
2
Some good suggestions, thanks!
I was thinking a manual battery disconnect switch, due to the loads being carried. One machine draws 12v / 150A for less than a second, up to two seconds, repeating these on/off cycles for 6 - 15 seconds. The other draws 24V / 30-40A ongoing for a continuous 30 seconds at a time. Both are re-set and run once every two minutes, one after the other, between 150 and 300 times a day for two days over a weekend...
Hence, the desire not to swap cables over and over. I'll probably just talk myself into carrying three batteries, but I've been hoping to find a way to avoid it.
BTW, the two deep cycle batteries I'm using have more than enough capacity to run these through a full weekend, but I recharge them each evening to avoid an oops and having to scramble to find a couple car batteries to "borrow" in a pinch.

Dodgydave

Joined Jun 22, 2012
9,457
That's a job for a contactor or relay..

RIKRIK

Joined Oct 11, 2019
107
That's a job for a contactor or relay..
I think your right. Would the knife switch work in combination with a relay or contactor. You turn everyting off with a normal on off switch connected to a relay on ground. Then move the knife switch into 12 or 24v mode. Then you turn the relay on.

Okay the knife switch is made for AC. but it might work aslong as you move it into position with the power off Thoughts anyone....???