Dual AGM Battery system

[Doug1]

I'm using Dual AGM batteries to have extra reserve electrical power but hooked them up in parallel temporarily until I could get a solid plan to make the best use of them. I've already had one instance where the Alt was not getting a good signal to charge the batteries and so I drove for a long time on just battery power. I don't have idiot lights so the volt gauge alone didn't show any issues.

I want to be able to run my AV, etc. at shows without killing my starting battery. I'd also like the ability to switch to the second battery in case my starting battery was low and would not start the car.



I think only a DC-DC isolator will take the AGM batteries up to 100%. Will they allow switching like I mention above or do I need to add a manual isolator switch as well?

[Doug1]

Anyone have any experience with this?

[Larry Callahan]

No experience but I plan on doing something like this. Check out this site for info. Some even will disconnect when the voltage drops to some low number that will start the engine.

https://www.waytekwire.com/products/...ery-Isolators/

- - - Updated - - -

or

https://www.waytekwire.com/products?...e%20disconnect

[TheJDMan]

I know that motorhomes and RVs use a system that will isolate the starter battery from the the coach batteries so you can always start the vehicle.

[Doug1]

I know that motorhomes and RVs use a system that will isolate the starter battery from the the coach batteries so you can always start the vehicle.

Here are a couple of short videos from a RV place that sells these type systems. In the DC-DC charger, it can charge an AGM to 100% because you tell the system it is an AGM. The one thing I am not sure about is the starting battery.

Does a standard alternator charge an AGM to 100% or not? Since most AGM batteries require a 4 stage charge to get to 100%, how can it get there with a standard alternator?

Smart Battery Isolator
https://www.youtube.com/watch?v=9jjh3Y4xIL8

BCDC charger

https://www.youtube.com/watch?v=0V2AfxKXHvg

Battery Management System
https://www.youtube.com/watch?v=Qgg9unSaXYk

[TheJDMan]

Does a standard alternator charge an AGM to 100% or not? Since most AGM batteries require a 4 stage charge to get to 100%, how can it get there with a standard alternator?

I suspect not 100%. The reason I say that is because every time I drive the car it charges and starts just fine but I always put a maintainer on the battery when it is back in the garage and it always shows the battery a bit low on the screen. I have no idea if this is a problem or not an issue. I also have a pair of Odyssey AGM batteries in my Silverado Duramax now for about 5 years with no charging or starting issues.

[Doug1]

I'm thinking the alternator would need a microprocessor to fully charge an AGM. In newer cars, it most likely has the capability but a stand alone alternator most likely doesn't get it there. To keep them topped off it looks like you need to hook up a smart charger / maintainer. Sort of a bummer that you constantly charge it to 80% and run from there, as the video seems to imply. That has to shorten the life of the battery.

[anguilla1980]

This is for sure the case with my Odyssey battery in my car.

[Doug1]

This looks like the proper solution but it is EXPENSIVE.

https://www.sterling-power-usa.com/s...rycharger.aspx

[TheJDMan]

That is an interesting regulator. I wonder how much difference it would actually make. I mean I'm running Odyssey AGM batteries in two of my tractors the car and the pickup and none of them have had any starting issues over the past five years.

[Doug1]

That is what I am trying to figure out. I have two Odyssey batteries in the TA and want to use them more wisely than I have. I actually had to get a jump start last week because I drove it for a while and it wasn't charging, without me knowing it. The only way I found it wasn't charging was when it didn't start. It turned out the wire to activate the alternator had worked slightly loose. These are two pretty big batteries so starting should never be an issue if I get this set up correctly.

I ordered this earlier this week after the jump start and it should arrive today but now I am not sure if it is the best thing to use, since it doesn't do the 4 step charge.

https://www.amazon.com/Blue-Sea-Syst...8J62TMW1YKVRKP


There is this for less money since it is not marine grade..
https://www.sterling-power-usa.com/p...regulator.aspx

Also needs an isolator added like this...
https://www.sterling-power-usa.com/P...solator-7.aspx


Then there are things like the advanced charging regulator which does the 4 step charge itself but isn't set up for dual batteries that I can see.
http://www.balmar.net/?product=regulator-mc-614-h

Lot's of info to work through.

[Warthog5]

I have experience with this in the marine industry. It's designed for a boat....but is applicable to what your trying to do.
I do marine wiring......I've installed 40 of these now. It's clean and simple to use.

http://www.marinco.com/en/716-sq-140a-dvsr


You turn the House switch ON.....Turn the Start switch ON......Leave the Yellow /Combine switch in OFF.....Think of that switch as a built in jumper cables and only turn it ON if start battery fails to start it.

The relay is closed until it senses a major rush of current....as when starting your motor.....The alt then brings the start battery back to a set voltage and the relay closes...then charging both batteries.....Now lets say your at a show....you have the stereo playing.....or some kind of dancing lights.....You pull those loads off the house battery.......The relay is still closed and batteries are paralled together......So time marches on and you draw the house down...The relay will open.....Saving the start battery so you can start the car.

[Doug1]

That does look like a cool device to replace an isolator, though the amperage limit might be a bit low. I'
m not certain of that yet. The other thing it doesn't address is the multi-stage charging that AGM batteries should be receiving. I'll get it figured out eventually! lol Thanks for the information!

[Warthog5]

The other thing it doesn't address is the multi-stage charging that AGM batteries should be receiving.

That is not a concern. It's charging from your alt..... Now if you were using a battery charger....then yes.

[Warthog5]

I was on my other computer when I 1st jumped in here....This is a write up that I have to explain better.

BEP Cluster Switch.

You start your day by turning the Start switch and the House switch to ON.
At the end of the day you turn them both OFF.

It doesn't get any simpler than that. You don't have to remember to turn from Batt 1 when going out and switch to Batt 2 on the way back in. Just something else that you have to remember.

OK so what goes on with it is done all automatically thru the VSR [Voltage Sensitive Relay]

The Relay is in a closed position. As soon as you hit the key to crank the motor the relay opens, due to sensing a large surge of current.

Ok the motor is cranked and running now. The relay is still open. The Alt is charging the Start battery until it reaches a set voltage and charge.

Then the relay closes and is back charging Both the Start & House Battery.

Now another feature that happened when you hit the key is your electronics were ON and wired from the House battery. This will stop any spiking of the Electronics. They don't like to be spiked!

OK...Now your out sitting on the beach. The motor is OFF, but you have the Radio playing for hours. The Relay senses the drop and opens the relay again. The radio is still playing, but the relay just disconnected the Start battery out of the circuit so that it stays at Full charge to start the motor.

When you get ready to leave the beach and crank the motor the alt will charge the Start battery first and when it's back up, the relay will close and charge the House battery.

There is one more switch on the Cluster. It is the Combine switch. Think of that as Jumper Cables without having to dig them out and hook them up. This switch would normally be in the OFF position, until you need a boost on the start battery. Then turn it to ON. After the motor is running turn it back OFF.

Everything is all Automatic. No thinking about it. Your batteries will have a much better charge in them.

[Warthog5]

[Doug1]

That is not a concern. It's charging from your alt..... Now if you were using a battery charger....then yes.

This is where there seems to be a lot of confusion. (At least for me. lol ) I keep finding documentation that states a standard alternator such as mine does NOT do multi-stage charging so essentially it is only getting the AGM batteries partially charged (80-85%), which is not ideal for the batteries. It specifically can't do multi-stage charging to get an AGM battery up to 100% without the use of an advanced regulator or a full on Alternator to Battery charging system like the one below. The cars we are building generally don't have an advanced regulator that I have seen. I have a 200 Amp alternator but its an old style regulator and not a smart regulator.

So I think we might not have the optimal setup in place but it works well enough we don't really notice over the short term. Long term is another story. But then again, do I buy an expense $600+ alternator to battery charging system or just buy another set of batteries in a few years when these fail?

Check this link out.....
https://www.sterling-power-usa.com/l...%20charger.pdf

This link is to the Sterling Advanced Regulator Owner's manual.
https://www.sterling-power-usa.com/l...structions.pdf
You have to take the alternator apart and wire into the brushes. Seems like a lot of effort that can be skipped by using the Alternator to battery charger.

Here a link to Sterling Power USA Alternator-to-Battery Chargers
https://www.sterling-power-usa.com/s...rycharger.aspx

Here are the instructions for the Alternator to Battery charger that I am looking at. So far it seems to fit the bill and would handle my 200 Amp alternator charging two batteries.
https://cdn.shopify.com/s/files/1/06...B12210.pdf?477

This Alternator to Battery Charging System is designed to be put between an Alternator and AGM batteries. Though I'm not sure how it can be switched to use the house battery as the starting battery without a switch. I think a combination of the two is probably the ultimate solution. Maybe this along with the isolator switch as well?

The Sterling Power Alternator-to-Battery Charger is a marine grade, high performance, four step, alternator powered battery charger. By monitoring and then controlling the voltage level of the alternator connected to the input side, the alt-to-bat is able to provide a charge rate that recovers your batteries up to five times faster than a standard alternator.
Has the ability to mix on board battery types.
Can charge GEL, AGM, FLA, Calcium and LiP04 Batteries.
Always ensures start battery is properly charged, but also prevents the starting battery from being overcharged and damaged.
Our 4 Step Battery Charging Profile extends the life of your batteries by ensuring a full charge & conditioning, as well as entering a float mode when charging is complete to protect against overcharging your batteries.
Installs in place of a standard alternator to battery isolator.
Available in 12 volt / 130 amp, 210 amp and 400 amp output models.

[Warthog5]

Doug......Your confusing yourself.

That alt.....is the charging system.

Now if you want to charge a dead or Low battery, then yes.....You want a multi stage charger as a battery charger.


Looking at the links you posted.....I've never seen or used anything like that...

I run AGM's in my John Deere garden tractor, My whole house generator, My '07 Mustang GT/CS and my '15 F150.....Never needed or wanted a system like that Sterling.

[Doug1]

Doug......Your confusing yourself.

That alt.....is the charging system.

Now if you want to charge a dead or Low battery, then yes.....You want a multi stage charger as a battery charger.


Looking at the links you posted.....I've never seen or used anything like that...

I run AGM's in my John Deere garden tractor, My whole house generator, My '07 Mustang GT/CS and my '15 F150.....Never needed or wanted a system like that Sterling.

I confuse myself often. Lol. Your newer cars have an advanced regulator built into them. The system I listed does two batteries on different banks.

So an old style alternator can charge an AGM battery but it is not capable of the multi stage charging required to get the AGMs fully charged. An advanced regulator, such as the one on your new cars, can do multi stage charging.

[MonzaRacer]

"SIGH" In a car the alternator RUNS the car and refills the battery and unless your battery is drawn down way low you do NOT need any off the wall alternator or anything.
As for battery isolator the ones at local part store/farm store work just fine. Allowing the accessory battery to charge and be part of system as the alternator charges.
When car is OFF it isolates the battery that is designated for starting so it does not discharge if your radio or lights stay on. NOW if you really run system battery down some require you to jump dead battery off the charged starting battery but I would just add in a simple underhood crank circuit with push button. IF necessary.
I run a blue top in my Caprice with zero issues and standard 10SI GM alternator.
I have ran blue tops in two different cars with zero issues in charging.
Basically an isolator lets one battery power everything except the start circuit.
Proper grounds, and a proper turn on circuit for the alternator.
OH and I always like upgrading the charge wire to 8ga with crimped and soldered terminals.
https://www.zoro.com/e-z-red-hammer-...lHIaApHb8P8HAQ

One of these, my Power Probe soldering iron/torch and some shrink and seal shrink tubing. Also welders cable can be had from NAPA and tractor supply most times by the foot. Fine stranded 2/0 cable make starters sing even when batteries are lower than normal.