24v System, charging 12v auxiliary battery.

[ippielb]

Long story short. Machine is 24v, but the diesel heater i installed is 12v. So i mounted a separate battery to run the 12v diesel heater at night so i don't drain down one of the 24v batteries. Every night i disconnect the master switch on the machine as well. What i want to do is when im running the machine during the day, i want the machine's 24v charging system to charge the auxillary 12v battery to run the diesel heater during the night. I don't want to have to take the battery out every day and swap it out with a second battery.

I know there are things called buck converters, 24v down to 12v, but what i don't know is if having the 24v system grounded to the chassis, if i also ground the 12v battery to the chassis if that would cause issues if i would use a buck converter from the alternator to the auxillary battery.

 

[Simon C]

Never tried but possibly with 2 separate cables going to the auxillary battery with a disconnect switch on each cable and only turned on when engine running might work. Diesel heater would have to be wired directly to the master switches with main battery master switch off during heating. Think it would work
if you are only operator. Otherwise something might cook if one switch left on when not suppose to be.
They sell 24 Volt units but not cheap. We preheated a Large D155 Engine 1 week ago off a 12 volt heater with a battery booster helping a small 12 volt Battery.
It can be done with no mistakes.
Simon C

 

[Tyler d4c]

Could you just hook the added battery to one of the machine batterys in parallel so it will then charge. I've seen people just hook to one battery in a situation like this to use one battery to get 12 volts with out adding one

 

[heymccall]

We use the Vanner 60-10 battery equalizer on our wheel loaders to gain 12v from 24v.

 

[cfherrman]

Look up the specs of the heater, it might be max of 18v or if your lucky 32v

 

[Delmer]

You can hook both grounds up even though they're connected already, it will work fine (unless the directions say otherwise). But most buck converters are not meant for charging, check that they output 14V, 12 won't charge the battery, it will run the heater if you want to do it direct off the 24 without a third battery. A solar charge controller would charge the battery off 24V, not the most efficient, but you'll never know unless your alternator is really marginal.

 

[willie59]

Long story short is not always the best avenue for specific answers. Diesel heater? Would that be a engine block/coolant/oil heater? Or maybe a fuel tank heater? Is this a machine that is remote, not near 110V AC to work a heater? Specific questions require details.

 

[Nige]

The installation of the heater was all covered HERE Willie. You may have to go back a couple of pages to get the full story.

 

[1693TA]

If you are running a third battery and this third battery is in parallel with one of the two that are in series, you can install a battery "isolator" as they use in boats and campers to charge this third battery, but not discharge the other two starting batteries. These are small, solid state, and maintenance free once installed and protected from the elements.

In essence the 24VDC charging system will recharge your 12VDC series interconnected batteries, and the one 12VDC battery will recharge from the same 24VDC alternator. The battery isolator will disallow any discharge of the two series interconnected 12VDC batteries and only draw from the parallel connected 12VDC battery, (in this scenario). When the parallel connected battery reaches the battery isolator cutoff voltage level, it will disallow further discharge by isolating it from the system, (hence the name). This does not have any bearing on your 24VDC, or 12VDC series interconnected batteries at all.

When the engine is started, the alternator will recharge all three batteries again.

Clear as mud I know but a very easy problem to address.

 

[treemuncher]

Why not just get a 24v=>12v converter? That's what I use in my 24v machines when I hook up a 12v radio. Those heaters do not pull a significant load and that would drop out the need for a third battery. The converter will also weigh less than the battery and have less maintenance issues to worry about.

One of my other machines also has a 24v equalizer block that puts out a 12v tap to the radio bank.

 

[Vetech63]

Could you just hook the added battery to one of the machine batterys in parallel so it will then charge. I've seen people just hook to one battery in a situation like this to use one battery to get 12 volts with out adding one

This is the simplest and best thing to do in my opinion. I've done this before with no issues.

 

[1693TA]

This is the simplest and best thing to do in my opinion. I've done this before with no issues.

Unless someone leaves a switch on inadvertently so over a weekend or longer......

 

[Vetech63]

Unless someone leaves a switch on inadvertently so over a weekend or longer......

True dat!

 

[kshansen]

True dat!

There's a saying that might apply here: "If you make something idiot proof someone will come up with a better idiot!"

 

[1693TA]

There's a saying that might apply here: "If you make something idiot proof someone will come up with a better idiot!"

Hey there now, I take resemblance to that!!

 

[ippielb]

The machine has two 4D batteries for the 24v system, the battery i've installed in a smaller group24 deep cycle battery from a camper. So the ratings are quite different. I just installed the 4d batteries brand new and i do not want to pull load overnight constantly from one of two batteries. I want to leave them un touched.

That Vanner equalizer is quite the expensive unit, for now i'm going to try a cheaper alternative.

The heater is 12-22 volt on the fuel pump. If i wanted to change it to run off 24v i would need to replace that, and the glow plug i believe. But as i said before, i want to leave the starter batteries alone and only use the auxiliary battery to power the diesel heater.

Delmer you have a good point, i totally forgot about the buck converters not going to a charging voltage. That wouldn't help me at all charging the auxiliary battery. The solar chargers are a good idea, but from what i've seen they can only handle 23-24v, and the alternator puts out 26-28 volts from what i've seen. Not sure if the solar charger would be able to handle that.

Willie, the diesel heater is a chinese knock off of a webasto bunk heater. It's a hot air heater that i've installed an EGR cooler inline of the exhaust to scavenge the waste heat to heat the coolant as well. The machine works out in the bush during the winter, miles from any source of electricity. And i'll be starting it in temps down to -20C no colder. I just wont work the machine if it's colder, i don't want to break something and have to fix it in the cold.

1693ta, i didn't know about isolators, looking them up i see that most want them to be installed directly from the alternator, and not from the first battery. Would i instead put a cable from the first battery to the "alternator" post on the isolator, and then hook up the auxillary battery to the correct terminal and then nothing to the "starter battery" post?

Treemuncher, i already installed the auxillary battery and really dont want to tie into the starting batteries. I like the idea of having an isolator like 1693ta mentioned.

I want to make the system as simple and easy as possible. I put the controller for the heater inside the cab since it is the least bit weatherproof. So it would be nice to make the charging automatic as well so i can easily just set the timer for the next day and then easily hit my master switch and go home. Not having to worry about any connections, or switches.

 

[terex herder]

By paralleling one of the 12V batteries with another 12V battery, you are essentially paralleling 2 different size batteries. I have always been told this is a no-no, as the larger battery is undercharged and the smaller is overcharged. The pair and the single each have to receive the same number of amps current. Or have I been told wrong?

 

[1693TA]

By paralleling one of the 12V batteries with another 12V battery, you are essentially paralleling 2 different size batteries. I have always been told this is a no-no, as the larger battery is undercharged and the smaller is overcharged. The pair and the single each have to receive the same number of amps current. Or have I been told wrong?

They will both reach the same potential and equalize. Of course the larger battery will have higher capacity as designed, the smaller battery will also charge to it's capacity.

 

[heymccall]

Isolators have a voltage drop, voltage sensing relays don't.

 

[Delmer]

I wouldn't want one of those isolators, they have almost a full volt drop on each side, so the 24V system would never fully charge unless you have a voltage sense and hook it to the 24V battery side of the isolator, and there's no reason to do that, you only need the 12V side isolated from the 24V side, and a solar charge regulator will do that.

Having the 12 4d parallel with the 12v 24 size battery with a load on it will kill the 4d that's it's parallel with and over charge the 4d that's in series with the two parallel batteries. All current to charge the two has to go through the single battery, that's what you want to avoid.