EASIEST SIMPLEST CHEAPEST WAY to have power in van. Using starter battery?

[Jack Mmkay]

HI! I wanted to share an idea with y'all electrical masterminds.

I want to keep my electrical system as low cost and little component and simple as possible : All I want is to charge my laptop, phone and maybe power bank.

Could I theoretically simply have one huge 200 AH AGM battery that I use both to start the car and charge my appliances safely and without damaging any components?

Reason is I don't wanna spend 200€on a dc dc battery charger and another 200+ on a secondary battery and 100+ on fuses, cables and relays I don't have experience with electricity so certainly I'd fck something up.

Thoughts ? Ah and I know this is a solar forum but I wanna keep as low profile / stealth as possible with my wan so solar would be a nope for now ( short roof = visible panels )

Is there a reason I couldn't use a big agm battery as starter battery in my 1998 2.4D VW T4?

Thanks again !

 

[DerpsyDoodler]

They do make dual purpose deep cycle/cranking batteries. The difference between deep cycle and a cranking battery is that deep cycle is rated to handle a depth of discharge to about 50%. If you do that to a cranking battery, it will kill it. Cranking batteries shouldn’t be drained passed 90% (and should be quickly recharged). Regular deep cycle sla batteries aren’t built to put out the cranking amps needed for starting a vehicle, while a starting battery is.

 

[Q-Dog]

Add a deep cycle battery with a battery isolator, just like RVs have been doing for 40 years. Run all of your accessories from the deep cycle battery. The advantage is you don't have to worry that accidentally leaving something on will kill the starter battery. Installation is simple.

There are other brands, but here is an example of one. Victron ARG100201020 Argofet 100 Amp Battery Isolator for two batteries

 

[Supervstech]

HI! I wanted to share an idea with y'all electrical masterminds.

I want to keep my electrical system as low cost and little component and simple as possible : All I want is to charge my laptop, phone and maybe power bank.

Could I theoretically simply have one huge 200 AH AGM battery that I use both to start the car and charge my appliances safely and without damaging any components?

Reason is I don't wanna spend 200€on a dc dc battery charger and another 200+ on a secondary battery and 100+ on fuses, cables and relays I don't have experience with electricity so certainly I'd fck something up.

Thoughts ? Ah and I know this is a solar forum but I wanna keep as low profile / stealth as possible with my wan so solar would be a nope for now ( short roof = visible panels )

Is there a reason I couldn't use a big agm battery as starter battery in my 1998 2.4D VW T4?

Thanks again !

Yes, a large deep cycle battery could be used, at the risk of depleting the starting battery though.
If you choose this path, be sure you have a jump starter box to get the car started once you let it go too far. Also, be aware that depleting deep cycle batteries can damage them rapidly, and starting with them can also damage the cells...
So, while it would work, it isn’t ideal.

 

[Jack Mmkay]

Add a deep cycle battery with a battery isolator, just like RVs have been doing for 40 years. Run all of your accessories from the deep cycle battery. The advantage is you don't have to worry that accidentally leaving something on will kill the starter battery. Installation is simple.

There are other brands, but here is an example of one. Victron ARG100201020 Argofet 100 Amp Battery Isolator for two batteries

I thought about that but ive seen a video that says having a lead acid cranking battery charging an agm isnt healthy for the alternator and the batteries. Would i need both to be agm, or as long as there i use the isolator its fine?

 

[Jack Mmkay]

Yes, a large deep cycle battery could be used, at the risk of depleting the starting battery though.
If you choose this path, be sure you have a jump starter box to get the car started once you let it go too far. Also, be aware that depleting deep cycle batteries can damage them rapidly, and starting with them can also damage the cells...
So, while it would work, it isn’t ideal.

I thought about using a simple usb voltimeter. I think that + me being careful should be enough.

Also, It's okay to use an AGM as a cranking battery? Could there be any issues? ( my van is a 1998 VW T4 2.4D )

Last thing. Is there a specific maximum capacity for the battery i'm allowed to use or can i throw in any 200+ AH agm battery?
Many thanks!

 

[Q-Dog]

I thought about that but ive seen a video that says having a lead acid cranking battery charging an agm isnt healthy for the alternator and the batteries. Would i need both to be agm, or as long as there i use the isolator its fine?

It is called compromise, or a tradeoff. There are smarter ways to do it, but not much simpler or cheaper. Cheapest would use a relay to connect the truck and house batteries when the engine is running, and disconnect when it isn't running. The isolator is a little bit smarter and has no mechanical failure points. The isolator in my RV is over 30 years old.

Don't go too big on the house battery and you shouldn't have a problem. It is not much different from drawing down your giant starter battery every night and having the alternator have to pick it back up. I say, start small and use the system for a while. Figure out the limitations and make improvements in a few years when it is time to replace batteries.

 

[Jack Mmkay]

It is called compromise, or a tradeoff. There are smarter ways to do it, but not much simpler or cheaper. Cheapest would use a relay to connect the truck and house batteries when the engine is running, and disconnect when it isn't running. The isolator is a little bit smarter and has no mechanical failure points. The isolator in my RV is over 30 years old.

Don't go too big on the house battery and you shouldn't have a problem. It is not much different from drawing down your giant starter battery every night and having the alternator have to pick it back up. I say, start small and use the system for a while. Figure out the limitations and make improvements in a few years when it is time to replace batteries.

Thanks! Now I' consider investing in a battery isolator since I plan on owning some kind of home on wheels for the rest of my life. I didn't think of it as an long time investment before.

 

[Supervstech]

The Diesel motor can need significant starting amps occasionally, but should be ok. The alternator will take a pounding if the battery is low charge, and may or will fail if repeatedly used to keep up a huge house battery.
The bosch alternator is PRICY to replace, so source a low cost used one from a parts yard.
They aren't real difficult to change on the I4

 

[Q-Dog]

Mine looks like this, but I have no idea who made it. Note, they have different amp ratings. Get one that can handle the amps of your alternator.

https://www.etrailer.com/Battery-Charger/Deka/DW08771.html

 

[Jack Mmkay]

Thanks for all the anwsers! Question : Is a battery isolator the same a as a VSR ( voltage sensitive relay ) ? Somehow I cant find anything when I type in " Battery isolator " in Spanish amazon ( yeah I live in Spain).

This is what comes up ---> VSR

If it's not the same, I'll look in other sites that aren't amazon. Thanks !

 

[DerpsyDoodler]

Instead of having an ignition lead that tells the isolator when to connect the house battery to the charging system, a VSR senses the voltage and when it sees high enough voltage to believe the system is charging, it makes the connection.

 

[Jack Mmkay]

Instead of having an ignition lead that tells the isolator when to connect the house battery to the charging system, a VSR senses the voltage and when it sees high enough voltage to believe the system is charging, it makes the connection.

I see. Thanks!

 

[Q-Dog]

The older style isolators (the second link I posted) are just a bunch of diodes that prevent voltage from reversing between the 2 batteries. The newer style, like the Victron unit, use FETs. The newer style is a little more efficient, but they both accomplish the same thing.

 

[mikefitz]

This voltage controlled isolator will work well in your system,

Cyrix

Its smarter the one in your link,

You will need fuses and cable to connect up the house battery to the engine battery,
Fuse 2
cable, 16mm2,
cable
terminations, select type to match stud connections at fuses and at battery,
cable termination
Fuse box for chargers , lights and so on,
Fuse box
for the smaller cables to the fuse box,
crimp connectors

Typical diagram, the fuses F1, F2, F3 to be as near the batteries as practical. The Cyrix can also be used as an emergency start mode, ( not shown in the diagram).


Rather than an AGM battery I suggest a sealed Varta LFD75 or LFD90. The charge characteristics are more in keeping with the alternator system in the van and will not overload the alternator. These Varta batteries perform well in modest systems.

Varta battery

Mike

 

[Jack Mmkay]

This voltage controlled isolator will work well in your system,

Cyrix

Its smarter the one in your link,

You will need fuses and cable to connect up the house battery to the engine battery,
Fuse 2
cable, 16mm2,
cable
terminations, select type to match stud connections at fuses and at battery,
cable termination
Fuse box for chargers , lights and so on,
Fuse box
for the smaller cables to the fuse box,
crimp connectors

Typical diagram, the fuses F1, F2, F3 to be as near the batteries as practical. The Cyrix can also be used as an emergency start mode, ( not shown in the diagram).
View attachment 38404

Rather than an AGM battery I suggest a sealed Varta LFD75 or LFD90. The charge characteristics are more in keeping with the alternator system in the van and will not overload the alternator. These Varta batteries perform well in modest systems.

Varta battery

Mike

Thank you so much !! I will certainly refer back to this as I'm doing the installation. You're the man Mike!

I supose since I'll be using the battery isolator It doesn't matter if main cranking battery and the varta house battery are not exactly the same kind of technology ? ( one lead acid and then whatever the varta one is made of ) ???

 

[mikefitz]

one lead acid and then whatever the varta one is made of

The Varta I recommended is lead acid and so will 'play nice' with the starter battery.

Mike