Properly charging a deep cycle battery (1 Viewer)

[woytovich]

How is one SUPPOSED to charge a deep cycle battery when it is in a vehicle in a dual battery set up when the other battery is a starting battery? I am told that the deep cycle would not achieve full charge as quickly as the starting battery thus requiring a longer time with the alternator running to get it to full charge.

This would be a problem if the deep cycle was in a vehicle that normally only did short trips with regular use of that battery for accessories. It would never get fully charged while the starting battery would.

Any insight would be appreciated as I may be going to be going to a dual battery set-up in the spring.

Mark

 

[canman]

After a lot of reading/ research on the subject of dual batteries and how to charge them, I went with an isolator with an external excitation terminal. There are pros and cons to each of the options available, but I wanted something simple, no moving parts, and inexpensive. As I understand the function of an isolator, the current will flow to the battery with the lowest charge (voltage) until the voltage is equal in each of the batteries. In my set-up, I have re-wired things such that the original battery is now only for engine starting, and the aux battery (Odyessy) is for the chassis electrical components and my winch (yet to be installed). I also have two marine switches, one of which is used to combine the batteries if needed, and the other to provide power to my winch when needed.

Link below to SurePower site with a very good explanation of how a battery isolator works.

http://www.surepower.com/pdf/ebr_int.pdf

Link below to my thread of my dual battery install.

https://forum.ih8mud.com/80-series-tech/448921-canmans-dual-battery-inverter-install.html


I also came across this post in a Canadian Tire review of one of their deep cycle batteries:

It is NOT a good idea to parallel different types of batteries, even within the lead acid family. A better solution is to use battery isolator, such as the Motomaster 11-1813, to simultaneuosly charge both batteries.
Things to consider
- The battery isolator drops the charging voltage by about 1 Volt.
- The alternator senses the charging voltage at its output terminal. Therefore, it doesn't detect the voltage drop. This results in the batteries not being fully charged.
- To compensate, some battery isolators come with a built in auxiliary diode to be conneced in series with the sensing lead in the alternator. This diodes causes a voltage drop similar to that of the battery isolator. With that the sensing electronics of the regulator to raise the alternator output voltage by the missing 1Volt.
- The batt isolator build-in diode is a good idea because it is thermally coupled to the isolating diodes which forces them to track thermally together.

 

[lostworldexpedition]

I am by no means an expert, and I have had many problems with our dual battery set up, but I have learned a lot by painful trial and error while on the road.

The batteries are kept isolated while truck is parked, and the alternator charges both while truck is running... In our case the "house" battery runs our fridge, lights, and any aux items. OK typical set up. Problem is, as you stated, the "house" deep cycle battery will not achieve full charge unless you drive for several hours (depending on the load it had). Unless -and probably even if- you are running a high amp you will need to supplement the charge either with a solar panel or a generator.

We chose a solar panel to try to minimize the drawdown of the battery and whenever we have access to a 120v outlet we use a marine "intelligent" battery charger to top off the "house" battery and equalize it.

Note: If you are not camping for more than a couple of days, and not using a fridge ignore what I said since you are probably fine just using the alternator to charge both batteries, just make sure the aux battery gets fully charged when you get home.

I highly recommend at least carrying a battery monitor (I wish we had one) such as the National Luna that Equipt sells (no affiliation to them)

 

[RufusTheDufus]

I run one of these to charge my Lifeline AGM house batteries. Not cheap, but easy to wire and will properly maintain your deep cycle batteries with a 4 stage charging profile. They also have 24v to 12v units for folks with 24v alternators.

 

[woytovich]

I run one of these to charge my Lifeline AGM house batteries. Not cheap, but easy to wire and will properly maintain your deep cycle batteries with a 4 stage charging profile. They also have 24v to 12v units for folks with 24v alternators.

Ok... so this is designed to use a battery (presumably while it is also being charged by an alternator? And also when it is not?) as a source to "properly" charge a deep cycle battery?

I guess that is what you said...

 

[woytovich]

...Not cheap...

$400 is, as you say, not cheap... but if I relied on the batteries for survival I would think this would be a good investment.

 

[RufusTheDufus]

Yes, you hook the input up to your starting battery that is charged by the vehicle's alternator. It will pull current from your alternator as it's available to charge your "house" batteries at their optimum voltage levels. It doesn't just take the voltage the battery puts out. It converts it to the proper voltage for your battery's chemistry (flooded lead acid, AGM, gel, etc.).

 

[RufusTheDufus]

$400 is, as you say, not cheap... but if I relied on the batteries for survival I would think this would be a good investment.

Look around online. I got mine for a little over $300 shipped from a boating supplies discount shop.

 

[woytovich]

Yes, you hook the input up to your starting battery that is charged by the vehicle's alternator. It will pull current from your alternator as it's available to charge your "house" batteries at their optimum voltage levels. It doesn't just take the voltage the battery puts out. It converts it to the proper voltage for your battery's chemistry (flooded lead acid, AGM, gel, etc.).

Does it know to not discharge you starting battery?

Does it only pull power during alternator charging?

How does it know what the battery being charged wants?

 

[RufusTheDufus]

Does it know to not discharge you starting battery?

Does it only pull power during alternator charging?

How does it know what the battery being charged wants?

Yes, there's no drain on the starting battery when the alternator isn't spinning. It will pull up to 40 amps if available, there is also a 130 amp model for people with higher output alternators. When it's charging it will pull the starting battery down to 13.8v, never lower.

There's a two position dip switch that's set at installation to indicate the battery chemistry of the house bank. That's how it knows the charging profile. It maintains a recent history of charging activity.

 

[Lost]

i mdont know if this will help, but i had a d31 optima deep cycle in my fj62. it charged fine. once the alternator died and i drove 3hrs to make it back home before the battery ran out of juice pulling in the driveway

 

[Kevin Rutherford]

Deep Cycles

I once had a deep cycle as the main btty in a blazer, lasted for years w/ no problems.
You should always be concious of doing a lot of short trips in cold weather; are you driving long enough to re-charge what was lost by cranking the engine, which can be quite a bit in real cold when you have to crank it over for a while. Deep cycles will take longer to re-charge.
A good habit (or test) is to shut off the engine at the end of a trip, then turn the key back on to see where your voltage is. If it's dropping below 12 - 13v, let it run, or throw a charger on it.

 

[bugsnbikes]

the beauty of a deep cycle battery is that it can take its initial charge at as many amps as you can feed it.

The average promariner 40amp charger would take a long running time to charge a deep cycle battery with any kind of meaningful amp/hour rating.

Take a look at the promariner digital mobile charge 130. This unit fools your alternator into thinking the batt is low and then tells the alternator to give it the max amps that the alternator can put out---thus greatly reducing your charge time (or running time of the vehicle to do so). On huge 1500amp/hr systems---this can be a great thing if you dont want to eat up lots of gas running your engine to charge the batts.

If you end up bumping up to a Tundra alt./or other high amp alt.--- at 130+amps....the charge time would be greatly reduced. This is nice if you run your house batteries for a few days without running the vehicle then wanting to re-charge.......just takes a lot less run time of the vehicle and alot less gas consumption to charge up.

 

[Bogo]

When engine recharging. If you are only running the engine to recharge a battery bank, stop charging when the battery bank gets up to 90% to 95% recharged. The last 5% to 10% of the charge goes at a much lower recharge rate so you get much less charging per fuel burned. While this doesn't equalize the battery, it isn't to detrimental if an equalizing recharge is done every so often. That equalizing recharge can be done when moving from place to place, or with a solar panel. Equalizing only needs to be done monthly.

 

[woytovich]

Take a look at the promariner digital mobile charge 130

This is exactly what I was thinking there should be... a device that can feed the deep cycle what it needs while protecting the starting battery... and keeping both in good health...

Is there a less expensive unit that does the same thing? Maybe something the maxes out at less than 130? (if that is what makes it expensive)

On the other hand maybe it is not so expensive if you start to add up the components for other dual battery systems (isolators in particular)...

Mark

 

[Bogo]

I've been gathering information on what I need to do to charge an AGM battery bank on my 4Runner. I have to do an alternator repair or replacement soon as the one in the truck has a squealing bearing.

Anyways I've posted a bit on it in this thread: https://forum.ih8mud.com/79-95-toyota-truck-tech/460112-3-0-high-alternator-choices-experiences.html A major goal is to be able to properly recharge and AGM battery bank without exceeding it's maximum charge voltage. That often is around 14.5 volts. Note, many auto voltage regulators will gladly pump out 14.7 volts. It looks like Balmar has the equipment that will fit, but at $800 to $900 it is a bit expensive. Using a GM CS-144 alternator with 6/12 mountings comes in at about $250 to $300 total for all changes needed.

 

[woytovich]

Using a GM CS-144 alternator with 6/12 mountings comes in at about $250 to $300 total for all changes needed.

FWIW for my FJ60 I sourced a 144a alternator at the local auto parts place (and gave them a "core" that I grabbed at a pink-n-pull junk yard from THEIR core bin for $5)

Then I sourced the plug adapter and bracket adapter from WranglerNW... they were VERY helpful. I think That all came in to closer to $200 (Wrangler's alternators would have been more expensive than getting one locally)

 

[Bogo]

I'm expecting I'll be able to pick up all the parts from the guy in Ames. I also included some of the costs for rewiring to 2AWG cables with protective looms and a 200A fuse and fuse holder instead of the 80A fuse. Also in there is the cost of the adjustable regulator for the alternator. I may go with a circuit breaker instead of the fuse.