Onboard 12v charging possibilities

[V73W]

I'm new to carts and feel as though this may be beating a dead horse but I have a question about the viability of charging a 12 volt accessory battery on board without a "separate" charger.

Here's my idea. Run a switched battery isolator (commonly used in my experience with car audio to charge a battery to power accessories without draining your main battery, also most are rated to handle from 12 to 48v), to that connect a 36 to 12v converter to then keep the 12v accessory battery charged. The beauty of the switched battery isolator is you could either place a switch on say the dash to manually connect and disconnect the 12v accessory battery so you are not constantly drawing from your 36v bank. If you weren't worried about manually trying to charge the 12v battery the "ignition" or switched remote could be turned on from a lead attached to the charger port so it only connects the second battery and thus charges it when the cart is plugged into the charger. A manual switch could also be used to give a little juice to the 12v when it has been drained while using accessories i.e. radio, winch, lights, etc.

I know this would not be the cheapest route to go for having a separate 12v batt for accessories and keeping it charged but it would streamline the charging process where if someone didn't know to hook up a separate charger or you just forgot you should never be left with a dead accessory batt, my biggest concern for use is with a winch due to high draw and our hunting area can get pretty muddy so it might get used regularly and I would hate to find out my battery is dead miles from camp.

Like I said this is just a thought, any input would be appreciated, I had just never seen anyone try something quite like this but that could mean there's a good reason lol.

[Mooncarter]

Welcome to BGW. I sort of like the idea. However, I don't know how much the reducer will "charge" the 12v battery.

[pattyandrick]

It takes a more.than 12 volts to charge a battery. Generally 13.5 to 14.5 volts

Sent from my SM-J320V using Tapatalk

[V73W]

That was another question I had cause i have no experience with the voltage regulators, but do they truely regulate down to 12, 12.6, 13, 14.4 volts etc.

Yeah I would need somewhere in the neighborhood of 13.2-14.4 and 13.2 would be on the absolute low end

[BobBoyce]

Originally Posted by Mooncarter

Welcome to BGW. I sort of like the idea. However, I don't know how much the reducer will "charge" the 12v battery.

You are correct, it would not. Reducers, aka DC-DC converters, are designed to deliver 12 VDC to loads. They do not output a high enough voltage to charge a 12V lead/acid accessory battery to even 50% SOC in most cases. The result would be a sulphated (ruined) accessory battery.

You would have to use a Charge Controller, such as one used to charge a 12V battery from higher voltage solar panels. Then the voltage setpoints could be set to match bulk/float/equalize settings for the accessory battery chosen.

Bob

[Mooncarter]

Bob you are the expert here. If we forget about charging the battery wouldn't the reducer still produce a parallel voltage that can still be used albeit from the pack?

Which would also mean there needs to be some sort of switch when charging the 12 volt.

[yurtle]

Seems to me like you'd either want an aux battery OR a reducer. Why both?

[Mooncarter]

Originally Posted by yurtle

Seems to me like you'd either want an aux battery OR a reducer. Why both?

I think what he is saying is if the 12 volt battery is drawn down for whatever reason, and of course you can't run a winch off a voltage reducer, you could perhaps replenish the battery with the reducer and/or get the 12 volts from the pack.

[V73W]

I think Bob may have just gave me a better solution with the charge controller, and heck their cheaper than the reducers. I could possibly even go with a cheaper non switched isolator and control the on/off of the charging through the charge controller. I could at least try it this way pretty cheap, you can find cheap chinese charge controllers all over but it seems all of the heavier duty dc-dc regulators are expensive!

[BobBoyce]

Originally Posted by Mooncarter

Bob you are the expert here. If we forget about charging the battery wouldn't the reducer still produce a parallel voltage that can still be used albeit from the pack?

Which would also mean there needs to be some sort of switch when charging the 12 volt.

The problem is... The voltage out of a reducer couuld never bring a lead/acid battery voltage up to the point where it would be charged. It would become perpetually discharged, load up with lead sulphate, and fail. Whether you switch it or not, it would never get charged enough to prevent failure. You would have to use another chemistry, which raises cost.

Originally Posted by yurtle

Seems to me like you'd either want an aux battery OR a reducer. Why both?

For driving a winch

Originally Posted by Mooncarter

I think what he is saying is if the 12 volt battery is drawn down for whatever reason, and of course you can't run a winch off a voltage reducer, you could perhaps replenish the battery with the reducer and/or get the 12 volts from the pack.

A reducer cannot raise the output voltage high enough to replenish a lead/acid battery. A charge controller is the simplest way.

Originally Posted by V73W

I think Bob may have just gave me a better solution with the charge controller, and heck their cheaper than the reducers. I could possibly even go with a cheaper non switched isolator and control the on/off of the charging through the charge controller. I could at least try it this way pretty cheap, you can find cheap chinese charge controllers all over but it seems all of the heavier duty dc-dc regulators are expensive!

Exactly! I've used those inexpensive charge controllers for small solar power systems.