House battery in a Hyundai

[Zizzer_Zazzer_Zuz]

I am reduced to cold weather tent camping but I MUST maintain a small 30ah battery for medical device CPAP and for charging my phone and laptop.

I'm having trouble getting the battery full and I want to be able to charge more regularly and completely.

I have a panel and CC but I have not been able to mount the panel for charging while driving. I am also contemplating running wires from the starter to the house for charging while I drive. Stage 1 would be a 10amp inline fuse and a quick disconnect so I don't drain the starter. Eventually I would be interested is installing a solinoid.

Any thoughts or suggestions?

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[gargoyle]

Why the starter?
Alternator.

 

[Zizzer_Zazzer_Zuz]

For now I need a stop gap. My thought was to run from starter battery to in-line fuse to quick disconnect then to a quick disconnect already installed in the battery box. My hope was to charge the house battery while driving and disconnecting when I stop.

The charge controler is installed in the battery box. My plan is to roof mount my small panel to help with the charging when parked etc.

As phase 1 of this little project what are the draw backs, problems, or warnings to consider?

Phase 2 involves the alternator, a solinoid, and more permanent wiring.

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[John61CT]

Charging from the vehicle:

Anywhere on the circuit between alt, Starter batt and starter is a good point to tap in

Since that battery is so small it won't be pulling many amps, so off an accessory circuit you already have should be fine.

Even the ciggie port as temporary, just check it doesn't get too hot when the batt is depleted. And don't try to put more than ~6A through it, this is only OK because that batt is so small.

Manually disconnect when you're not driving, so you're not flattening the Starter batt.

It will take 5-8 hours of driving each day to get your batt 100% Full. The first couple hours may get it to 80-85%.

Don't idle the engine to charge the batt.

 

[John61CT]

How many watts is your panel?

What model controller?

 

[John61CT]

How are you judging how empty or full the batt is (SoC) ?

Have you got a mains battery charger? What model?

 

[Zizzer_Zazzer_Zuz]

My tools and hardware are 400 miles out of the way. I have the basics to run the wires and make the connections.

The battery died last night and would no longer run my CPAP. The CC this morning read something like 10v. This is a SLA so no SG testing even an option.

I'm considering a run to auto zone to see if they can charge it and then I should be able to maintain it.



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[Zizzer_Zazzer_Zuz]

60 watt panel.
Cheap PWM controler.

Now I'm a little concerned about where to tap in.

Once my phone is charged up some I'll try to take some pictures.

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[John61CT]

You have damaged the battery drawing it that low.

With your next hopefully bigger one, ideally designed for deep cycling, try to keep it above 50% full if you want it to last.

 

[John61CT]

You need to put a Watts Up or other AH meter on the CPAP and other loads to see how many AH per day you need to replace charging.

 

[frater secessus]

Starter = 'starter battery'.

OP: I don't think it would be much tougher to run a solenoid than the fuse.

 

[MrAlvinDude]

What to be aware of:

When you first connect the two batteries,  the empty battery might draw more than 10 Amp for a short time. A short time could be measured in seconds or minutes at the most (because your house battery is only a small battery).  

One way to possibly avoid the in-rush current, when first connecting the two batteries, could be to use long wires. The wire might then act as a current limiter.  It is however a balancing act, as the wires should not be too thin, or they will overheat.


The better ways is to use thick wires between the two batteries, and use big fuses.  You will quickly learn how big the fuse needs to be  


The high current in-rush will be less frequent, the more frequent you charge both batteries. So you might be able to use lower amp fuses on a daily basis, and only need the high amp fuses if your house battery is very low. 



As you are connecting two power sources, then you ought to place a fuse close to each battery.  When both batteries are charged, and you disconnect them, then they each are still a potential high current power source, so they both should have a fuse placed close to their positive terminal.



Last time I had to make a solution where I needed to connect two batteries, I bought two sets of jumper cables, and used the claws as a primitive connect/disconnect switch. 

Once I got home, I cut and trimmed as needed, and added the fuses close to each battery.  For weeks I still used the jumper cable claws, as a switch to connect the two batteries, until I could get a decent relay (at the right price - I had to wait for the about 30 day shipping time).

 

[John61CT]

Don't worry about a "surge" other than if you feel the connector getting hot.

Anderson plug would be best, plug in after engine started.

10A low-voltage-DC rated circuit breaker with a bit of delay if you want to be belt & suspenders careful while using a ciggie plug.