How do you choose the battery isolator size?

[swinada]

I tried to put some of these suggestions into pictures so I can envision them a little easier. The drawings are not very professional, please forgive me.
And please correct me if I did anything wrong.

1. A heavy-duty battery disconnect switch from plus on one bank to plus on the other, operated by a smart operator. No voltage drop or power used anywhere, but if left on can result in both systems becoming discharged.

3. A solenoid from plus to plus powered from the ignition accessory circuits, which connects whenever the bus is in the "run" position. This assumes the alternator is running whenever you leave the key on.

 

[swinada]

8. Two isloators, one for an AC-powered charger, and one for the alternator.

If you tie your alternator output to your charger output to share an isolator, you are braver than I am.

Is that statement still correct if the AC charger has the capability of charging up to 3 banks? Like the Xantrax Truecharge 40
Home
The Xantrex manual states that this charger is for deep cycle batteries, can the regular starter batteries also be charged with this charger?

 

[Redbear]

If you tie your alternator output to your charger output to share an isolator, you are braver than I am.

Is that statement still correct if the AC charger has the capability of charging up to 3 banks? Like the Xantrax Truecharge 40?

I should have been clearer:
If you tie your alternator output to your charger output to share an isolator ISOLATED FROM THE BATTERY, you are braver than I am. The battery absorbs any voltage spikes that could cause damage. They should go through the isolator and be absorbed indirectly, but I don''t tempt fate.

The drawings are correct representations of what I was talking about. Reading the Xantrex install manual, it appears the drawing with two isolators and the one wiht the Xantrex are electrically the same, except that the Xantrex has a 40-amp 3 port isolator hidden inside the housing,

 

[izzydojo]

RedBear Do you suggest using a Cole Hersee 200 Amp Battery Isolator for a Ford F350 Super duty that is constantly pulling behind it a 20 foot enclosed trailer with has 12 - 12 volt lighting on along with a huge light bar above the back of the ramp door and 2 light bars on the top of the truck one overseeing the bed and another for seeing forward ? alternator is the standard 110v

 

[BenMaClem]

Posting here as well since it is the same topic.

We have an alternator with an internal regulator, but we have an isolator with only 3 terminals, no exciter.
Is there a way to excite the alternator from another source? Like the ignition maybe?

 

[Brewerbob]

Good info on the isolator. I need to clarify something as I am confused. When we are discussing a battery isolator, it is a system that charges the starting batteries as well as the house batteries. The isolator keeps the two systems from interfering with each other. In a couple of post, I wonder if the poster is talking about a battery disconnect?

I have a nagging electrical issue in that something is draining my batteries. I have tried to identify the culprit but I have not found it yet. I have been thinking about installing a battery disconnect as a for sure way to easily keep my batteries from draining. I have shopped for one and I do not understand proper sizing and where it is intended to be installed.

Originally , I thought the disconnect should disconnect the battery as close to the battery as possible. The sizing of the disconnect vs. the size of my battery leads are not a match so I am thinking this disconnect is intended to be installed perhaps in the instrument panel. Could someone set me straight?

I'm thinking about this.

https://www.amazon.com/NVX-BIR500-5...=1492610495&sr=1-21&keywords=battery+isolator

A few thoughts on using that that may or may not apply to you. I do not have house batteries (yet). My batteries are very low right now as a result of not driving and not having electric around. Solar 12V charger with controller was ordered this morning.
https://www.amazon.com/gp/product/B01G82P6MK/ref=od_aui_detailpages00?ie=UTF8&psc=1

So, in order to use the isolator I linked, I've got to find switch 12v so that when I turn the key on, I can energize the relay closing the circuit for everything else. I've no idea what the starter draws for current. Haven't been able to find it online with teh starter part number. Using the relay will save me the effort of throwing a manual switch. Since I have to move the E-door lock physically I'm ok with having to manually throw a switch. It's just one more thing to the pre-flight check.

Since I'm still OEM electric all I really need is a kill switch to stop whatever leakage current (if any) from discharging my starting batteries.

Oh wow, there's an entire novel of posts after this.

 

[dan-fox]

I'm thinking about this.

https://www.amazon.com/NVX-BIR500-5...=1492610495&sr=1-21&keywords=battery+isolator

A few thoughts on using that that may or may not apply to you. I do not have house batteries (yet). My batteries are very low right now as a result of not driving and not having electric around. Solar 12V charger with controller was ordered this morning.
https://www.amazon.com/gp/product/B01G82P6MK/ref=od_aui_detailpages00?ie=UTF8&psc=1

So, in order to use the isolator I linked, I've got to find switch 12v so that when I turn the key on, I can energize the relay closing the circuit for everything else. I've no idea what the starter draws for current. Haven't been able to find it online with teh starter part number. Using the relay will save me the effort of throwing a manual switch. Since I have to move the E-door lock physically I'm ok with having to manually throw a switch. It's just one more thing to the pre-flight check.

Since I'm still OEM electric all I really need is a kill switch to stop whatever leakage current (if any) from discharging my starting batteries.

Oh wow, there's an entire novel of posts after this.

https://www.vintageautogarage.com/Battery-Disconnect-Switch-With-Key-p/s1202.htm

 

[Brewerbob]

https://www.vintageautogarage.com/Battery-Disconnect-Switch-With-Key-p/s1202.htm

Saw those but I have 2 batteries in parallel with 925 CCA each. That thing will melt at 1800 amps. I measured the current while starting the bus the other day and it said I had .2 amps. I don't believe the switch is seeing either of those numbers but I've no idea what it is really seeing. 500 amps for 10 seconds "should be" safe but I'd rather KNOW it's safe.

 

[Stu & Filo. T]

Good info on the isolator. I need to clarify something as I am confused. When we are discussing a battery isolator, it is a system that charges the starting batteries as well as the house batteries. The isolator keeps the two systems from interfering with each other. In a couple of post, I wonder if the poster is talking about a battery disconnect?

I have a nagging electrical issue in that something is draining my batteries. I have tried to identify the culprit but I have not found it yet. I have been thinking about installing a battery disconnect as a for sure way to easily keep my batteries from draining. I have shopped for one and I do not understand proper sizing and where it is intended to be installed.

Originally , I thought the disconnect should disconnect the battery as close to the battery as possible. The sizing of the disconnect vs. the size of my battery leads are not a match so I am thinking this disconnect is intended to be installed perhaps in the instrument panel. Could someone set me straight?

I had a Class C up until a few yrs ago & I was draining 2 Optima Blue tops in just a couple days that were for my house circuits, the way it was set up was it had a solenoid that would close once the alternator started producing energy & charge my house batteries,.

Well one day I'm at work discussing this problem with 2 other coworkers & the Old Old times says, " Take that solenoid apart & see if theres a green film inside" & sure enough there was much like the film you see on copper pipes it ran from the terminal side for the house batteries over the insulator & to the solenoid housing. I changed out the solenoid & never had author problem with it.

 

[coolbus-SKO]

Not sure if this helps, but this is how I solved this problem. Below is a link for a relay excited by higher voltage from the alternator running or charging from solar etc. The relay closes when anything is charging either set of batteries and then opens when the charging source goes away. Rated for a constant 140 amps.

With two 900 CCA bus batteries and two deep cycle optima yellowtop house batteries I've never seen over 65 amps crossing from the alternator even when it first closes and my house batteries were down around 11.2 volts because I left something on overnight, so 140 amps goes a long way.

https://www.amazon.com/gp/product/B00400IYTK/ref=oh_aui_detailpage_o04_s01?ie=UTF8&psc=1