12v grounding/wiring question

[eeyore357]

I am planning on adding a third battery only for 12v accessories. I've looked at some other threads and couldn't find a definitive answer. Do you have to keep the -12v grounds (battery and accessories) isolated from the chassis due to the -24v?

 

[cranetruck]

No, ground all DC supplies to the same point, unless there is a reason to keep a battery "floating" like in serial connections to provide higher voltages.

 

[Mayor Joe]

I was thinking of doing the same thing - how do you plan to keep the third battery charged?

 

[eeyore357]

"ground all DC supplies to the same point"? Eventually I will add a 12v alternator but for the time being I'll be using a 3.5amp solar panel and a battery charger (when it runs out, it runs out). I'm just going to be using it for a cell phone charger and stereo.

 

[zout]

You have an option of installing a battery equilizer as well - will charge 24v & 12v at the same time. Vanner makes on but I cannot rememebr the 100 amp one I am running at this time.

 

[m-35tom]

for the price of another battery and the hassle of keeping it charged, just get a vanner equalizer.

 

[59apache]

http://www.steelsoldiers.com/showthread.php?56451-2nd-alternator-12V&highlight=
http://www.steelsoldiers.com/showthread.php?59763-Battery-Box-repair-mod-for-third-battery&highlight=

http://www.steelsoldiers.com/member.php?8583-tm-america

the most important question is (after the total load) how much capacity do you need. It makes no sense to install an alternator for a cellphone charger.
If you want to run a cooler or little fridge or something else without the engine all the time running, you want the saftey and capacity of a 3rd battery.
Every fire truck or emergency vehicle that i know has a independant battery for the electrical consumers to keep the starter battery full.​

IF you need a 3rd battery, use an alternator for charging, TM_america sells a good mount.

 

[eeyore357]

A short while after I got the truck I had one battery go bad. So instead of giving them the good battery I just kept it and got 2 new batteries. I just like the idea of having my starting batteries separate since I have an extra. I'm sure at some point I'll forget to turn something off and don't wanna be stuck.

 

[59apache]

looks very similar to my setup. And my reason was the same

use a second alternator and a battery protector like this one http://votronic.de/en/catalog.php?P..._3_8&mode=product&id=88&catid=7&cattype=group

and everything is nice

 

[swbradley1]

http://www.amazon.com/Pyle-PSWNV720...id=1385545588&sr=8-1&keywords=pyle+24v+to+12v

Put it across both batteries and add a fuse on the positive side AT the battery. Done. Simple and inexpensive.

 

[59apache]

with 12,8V output you can't charge a battery properly. And you have to disconnect the converter while the engine isn't running, otherwise it drains your 24V batterys.

If charging was that simple, the whole dual voltage alternators are useless.

 

[59apache]

there are special battery to battery chargers on the market. (google for b2b charger). They are expensive. And you have an additional load on hte original system.

 

[wheelspinner]

That item is not for "charging" a third battery, it is for eliminating the need for a third battery. When 12v loads are low, it is completely unnecessary to have a stand alone charging/storage system.

 

[swbradley1]

Wheelspinner is correct. My solution is to not add another mechanical item to break or maintain and further clutter the engine compartment. Let's add more expensive cabling for an extra battery, another belt and alternator.

I have yet to see one member post they needed enough power to run a 17,000lb 12vdc winch or similar device. Well, maybe a HAM operator might want some power but almost every poster wants to charge his/her cell phone or run a GPS.

 

[docpadds]

I went second alternator on mine, and an RV panel, and a Solargizer..... my 12s and 24s get charged about all the time the truck is running or parked (with shoreline plugged in )

 

[zout]

Just a question as from the OP he just wanted to run some 12v stuff. Why not just tuck a deep AGM deep cycle small battery away and get a solar charger specifically just for that.

If you use a normal 12v battery they are not designed for a constant draw - they are for cranking amperages.
Deep cycle batteries as well have to be charged at a less amp rate and slower.

You could tap off off this and have hours of power at a minimal cost.

 

[Mayor Joe]

m-35tom - THANK YOU THANK YOU THANK YOU - I went to the Vanner website and found not only the equalizers, but flashers and it turns out the local distributor is a vendor I use for starter and generator rebuilds! Who knew? Anyway, he's sending over some info / recommendations, and I'm sure I'll be installing these in my M35, M37 and M43.

Really appreciate the advice and hope this helps others!!

Joe W.