Second battery vs alternaor

[ultinator]

Hello good people of the forum,

I am new here, this is my first post - so I aplogise if i have put in the wrong place!!

I was wondering.

If a vehicle has a second battery attached, and that is connected via a split charge relay (so that only when the main battery has reached a fully charged voltage, does it switch to charge only the secondary one - and then charges the primary again if its voltage falls below a certain value)

If the second battery was a deep cycle battery.

If I wanted to whack a hefty amp in there, (not sure exactly how much it would be 1.2 - 2.0 KW, so true rms would be lower)

If that was connected directly to the deep cycle battery, could the deep cycle have any issues with providing enough juice for the systems max Amp requirement?

Also would this do anything to ease the strain on the alternator?

Is it in any way a beneficial to the longevity of the cars electrical components by utilising the second battery..

or is a bigger alternator along with the big three always the preferred starting point?

(becuase having a second battery is easier than changing the other things)

Hope that all makes sense,

Thanks for your time ladies and gents.

Good day

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[Papermaker85 5,000+ posts]

Alt.

 

[ptcruiser07 10+ year member]

i ran 4k watt system with a stock alt and a big *** xs batt in back for a while, it did work but still had bad voltage drops. now i run a 370amp alt with big 3 ofc and one batt under the hood and do just fine. only running 2.4k atm tho.

 

[SounDrive Pro Seller]

A bigger alternator is always better. Stressing the stock alt is never a good idea and will eventually lead to failure.

 

[adulbrich 5,000+ posts]

^This

Is the battery setup you're talking about stock? If so, I bet it's a diesel truck. Otherwise, I have no idea what you're talking about

 

[ultinator]

It's a small diesel van.

I installed a deep cycle battery to power an inverter to give me A.C. electricity when the van was turned off.

The split relay will mean I could drain the deep cycle battery completely without affecting the primary battery for starting the engine.

The benefit of this is that the alternator is only ever charging one battery at a time, and always prioritises the primary battery.

Do diesels + vans normally have bigger alternators to begin with?

 

[Papermaker85 5,000+ posts]

Usually they have larger batteries and depending on the accessories can have larger alternators.

Having a deep cycle is good for long periods of low current consumption. They have a higher esr then then standard battery there for if you have the car off its much more ideal but if you are installing a system I'd recommend a starting battery because it discharges faster and is able to recharge faster as well. Granted you don't completely discharge them they will provide better dynamic performance over deep cycles.

 

[dbjunior 10+ year member]

I wouldn't bother with the split relay setup. Just a battery isolater to separate the batteries when off charging both together will be fine.

 

[germanyt 10+ year member]

I wouldn't bother with the split relay setup. Just a battery isolater to separate the batteries when off charging both together will be fine.

I ran a battery isolator on my very first HO alt dual batt setup. It gave me .4 volts of drop from the main to the aux. Both were AGM so after some reading I ditched the isolator and never had a problem. The only downside to not using one is that if you play long enough with the engine off your car might not start. But that is the case with any stock stereo.

 

[dbjunior 10+ year member]

I ran a battery isolator on my very first HO alt dual batt setup. It gave me .4 volts of drop from the main to the aux. Both were AGM so after some reading I ditched the isolator and never had a problem. The only downside to not using one is that if you play long enough with the engine off your car might not start. But that is the case with any stock stereo.

What size isolator? I'd only use a 500amp rated isolator or larger. I see a lot of 150-200amp rated ones on ebay. If your using a run of 1/0 You want something that can handle at least 50% more current than the wire.

 

[germanyt 10+ year member]

What size isolator? I'd only use a 500amp rated isolator or larger. I see a lot of 150-200amp rated ones on ebay. If your using a run of 1/0 You want something that can handle at least 50% more current than the wire.

I cannot remember. It was like 9 years ago. It would have been one recommended to me on this or another forum.

 

[wew lad 5,000+ posts]

i dont see how an isolator could cause voltage drop... i mean i believe you 100% that it did, but that doesnt mean it should have caused drop unless you maybe used the wrong isolator or some other factor played a role?