# My Project

#### CrazyArsedMonkey

Joined Feb 13, 2007
6
I have been challenged to design a circuit (This isn't academic btw) which is made up of 2x12v batteries. I have to power some 24v light tubes, start a 24v Diesel heater + power a 12v fridge and a 12v water pump. Can i actually do this with only 2 batteries? I know that 2x12v cells in series will give me 24v as long as they are the same current rating. could i then tap off a 12v supply from one batt or share the load between them somehow? Sharing the load is obviously the best option. Can anyone help me? I need to learn but cant find where!

Cheers guys, CAM

P.S. Did you know that the human body sheds, on average 19Kg's of dead skin cells, 'orrible or what?!

#### Papabravo

Joined Feb 24, 2006
15,562
As long as none of the items individually or together exceeds the current capacity of the batteries. How will you know if they do? Read the nameplates on the devices and watch for a drop in voltage when they are all on together.

#### CrazyArsedMonkey

Joined Feb 13, 2007
6
As long as none of the items individually or together exceeds the current capacity of the batteries. How will you know if they do? Read the nameplates on the devices and watch for a drop in voltage when they are all on together.
My problem is one of physical connectivity rather than power. I will buy batteries that will give enough Ah for the kit. I am just unsure if i can take a feed off one battery that is connected in series with another battery without circulating currents and other nasty stuff i am probably not even aware of!

Joined Nov 1, 2006
133
Hi CAM, You didn't specify, is this a 12 volt, negative-ground mobile application with a 12 volt charging system and do the refrigerator and water pump go in an RV or will it be used where there's AC power? I have some ideas on how to do this and charge the second [or both] batteries but I don't want to write a discertation and discover afterward that I based it on a wrong assumption.

#### CrazyArsedMonkey

Joined Feb 13, 2007
6
Sorry Dave i should have explained the application properly. This system is for a bus renovation project. The bus is being used by a charity to give kids a place to go to chill out and get in out of the cold. The utilities i mentioned earlier must run seperate to the starter battery hence the 2 12v leisure batteries. The bus will be static for around 3 hours between charges when it will then be driven to a garage and charged up from the mains (240v 50Hz here on the island ). I believe that 2x 57Ah batteries will be enough juice for this. I would love advice on how to wire the series/parallel circuits to prevent 1 battery flattening and screwing the system up and also how to wire the charger up. Thanks

Joined Nov 1, 2006
133
It sounds like charging the batteries won't be an issue for you; that simplifies things. As for connecting the batteries, simply wire them together in series, the way you mentioned. To keep the current demand somewhat balanced between them, supply the refrigerator from one battery & the water pump from the other. Connect your 24 V lights & heaters across both batterues.

Although some might take exception, I wouldn't ground either of these batteries since neither will be charged from the bus's charging circuit. Grounding could complicate things, particularly for anyone unfamiliar with the wiring.

Another question: it sounds like you're using an RV fridge; can it also be run on propane? If so, you could reduce battery drain a lot by using gas for the fridge & one battery to only supply 12 V for the refrigerator controls. Just a thought.

#### CrazyArsedMonkey

Joined Feb 13, 2007
6
For charging is it ok to simply put the charger across both batteries? I assume they would both charge simultaneusly?

Joined Nov 1, 2006
133
To charge the batteries by connecting a charger across both of them you'll need a 24VDC charger instead of a 12 V unit. Although it appears you've done so here, both batteries need to be the same size, otherwise the smaller battery will over charge & the larger one will be under charged. Another option is to simply use 2-12 V chargers, one for each battery.

#### CrazyArsedMonkey

Joined Feb 13, 2007
6
Hello again! Thankyou very much for your help so far guys One final question; How do i draw circuit diagrams that i can import to MS Powerpoint or paint or something? I drew a bunch of diagrams on Circuit Shop but the files produced cant be read by anything else, DOH . Thanks again ppl's.

Joined Nov 1, 2006
133
I've run into this same situation with AutoCAD when trying to send a drawing to non-CAD users. The only way I found to do it was to print it and scan it, then Windows automatically saves it in "My Pictures" where it can be copied, attached to e-mail, etc., or otherwise accessed.

#### n9352527

Joined Oct 14, 2005
1,198
Print screen, then paste to an image drawing program then save as a jpg.

#### JoeJester

Joined Apr 26, 2005
4,390
alt-print screen will save only the active window.

Of course you can select all, then copy ... then paste.

I guess it depends on what you want to do. For these forums, I prefer to print to a pdf, in alot of the cases.

#### pebe

Joined Oct 11, 2004
626
There is a freebee called 'FastStone Capture'. You can use it to capture all or any part of a screen and save it in a variety of formats.

#### Dave

Joined Nov 17, 2003
6,970
If you are looking for advanced screen capture software, you could look at WinSnap. The latest version is shareware, but there is also a freeware version available.

Dave