Charge auxiliary battery without isolator?

[YorzTrewli]

Hello!  I'm new here.

I'm planning on getting a 40aH AGM wheelchair battery to use as an auxiliary battery in my car/home.  

Do I need to install a battery isolator?  Or can I simply hook up some cables directly to my car battery and clamp them onto the auxillary battery after my car is running?

I have a CTEK battery charger that is my main charging source and I only drive short distances, maybe 10-15 minutes a day (4-cyl Honda).

I'd rather save up the money for a Renology suitcase than spend it on an isolator if I don't need it.

 

[ccbreder]

If the battery is 12 volt, yes.

 

[LeeRevell]

Will 20AH a day be enough for your needs?  Renogy gets very good reviews here.

 

[akrvbob]

First, no matter what don't buy an isolator, it's too expensive and doesn't even work all that well. A far better choices is a continuous duty solenoid for about $30 or a cheap battery on-off switch from Walmart for $15.

It sounds like you are going to use jumper cables to charge the battery while the car is sitting idling, did I get that right?

It would work but you will get very little charge while it is idling.

I know someone who did that, except she ran the jumper cables through the passenger window to the battery sitting in the passenger floor area so it was connected while she drove. That will also work, but it leaves you open to a lot of risk. If one of the cable ends comes off and touches any other metal you are going to get sparks flying and damage done!

By far the cheapest and easiest way is a 4 gauge cable from the positive post of the starting battery to a on-off switch, from the switch to the house and another cable directly between the negative posts of both batteries.

You will have to remember to turn the switch on while driving and off while the engine is off. That will work just fine.

It will still be a good supplement to the suitcase solar after you get it. The two work together very well!
Bob

 

[highdesertranger]

this is my second response like this. x2 on what bob said. good advice there. highdesertranger

 

[YorzTrewli]

Thanks a lot Bob, and everyone else.  Gonna take your suggestion with the on/off switch and some 4 gauge.  I plan on using this as a supplemental charge whenever I happen to be driving somewhere.  
Gonna run the wire through the firewall to the passenger side; no wires through the windows for me   .

20aH is enough for me as I only need it to run a stand alone fan-tastic, which draws 1.2 amps on low, during the hot hours of the night.  

The Renology suitcase (and an additional battery) will come eventually, but for now I plan on keeping it in a box and stealth charging it where ever I may happen to be.

Aloha!

 

[YorzTrewli]

Oops, one more question!  Should I fuse the wires?

 

[YorzTrewli]

Ok, plot twist. The AGM battery I was planning on getting was not up to par voltage. I decided to go with a 32aH gel battery instead.

I've heard gel's need a more regulated voltage during charging. Is charging through my car battery still viable?

 

[highdesertranger]

I have no experience with gel cells. hopefully someone who does will post up. highdesertranger

 

[Oberneldon]

It is my understanding that the 3 different lead acid batteries (AGM, Wet Cell, and Gel Cell) have slightly different charging parameters. Although AGM seem to play well off of Vehicle charging systems.

My house batteries are gel cells totaling 14 ah and I charge as I drive off a chemistry specific charger plugged into a 400 watt pure sine wave inverter connected to the vehicle battery.

I can charge at 2,4,8 amps depending on my length of drive time. I never felt comfortable charging off the vehicle 12 v circuit direct.

I have used a vehicle 12 volt charger to bring a gel cell back to life on a short duration then switched to the gel cell charger.

This has worked in helping older batteries get back to a 12.9 float voltage.

Brent

 

[LeeRevell]

RENOGY.

 

[Oberneldon]

Solar is a good solution but not solution for all situations. When I travel I live out of a Prius and a solar system takes up too much space. I have a good house battery system for $300 that lasts me all night long until running my engel compressor fridge. There is more than one way to accomplish charging house batteries.

 

[YorzTrewli]

That is an interesting setup Oberneldon, and I would definitely pursue it if I were traveling.

However, I only spend on average 30 minutes per day driving so I'm not sure that its worth the investment.

Solar is looking like my best solution, and I think I may be able to scratch up enough for the Renology suitcase soon.