Range Rover- Dual Battery Ideas

Dual Optima with battery monitor

Single Optima with battery monitor

http://www.hellroaring.com/ Battery Isolators and Combiners

 


From: Corbeau <corbeau@crowmountain.net>

I've been thinking about installing an Optima also. Did you need to modify the battery mounting hardware for the smaller size? Also, are there any links showing install details for dual Optima's?

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At 09:21 AM 1/5/2003 -0600, you wrote:

I have a Red top in my RRC that sits on top of a two by four piece of wood, otherwise it would sit too low. This allows me to use the stock hold down bracket. However, I didn't care for the design of the bracket due to its proximity to the pos term. Therefore, the two threaded rods were shortened and the horz bar that goes across the battery now sits in the middle of the battery.

Regarding the dual battery setup, I'm about to embark upon this myself using a Red and a Yellow top. Originally I was thinking of using a continuous duty 250 amp solenoid to isolate the two batteries. However, Painless wiring came up with a clean solution that allows the use of one or both batteries using a three position toggle switch. The cost of this system is $100 at summit racing. The solenoid is the most expensive part of this system. Summit p/n: PRF-40102. I'm sure Larry M. can come up with a cheaper solution using similar solenoid!

My .02 cents

Ali

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To: rro@koan.team.net Subject: Re: [rro] Optima Batteries

Ali- It sounds like your 3position toggle switch idea is a "solenoid" or "relay" operated way of doing the old marine battery trick, 3 position switches to select bat1, bat2, both, or NONE (storage. gee, you'd think they'd call that a 4pos switch). These switches are pretty inexpensive, even at West Marine here in Madison, I want to go this route on my old pontoon boat ( I have a 2amp solar panel charger on the roof to keep the battery charged for the 99% of the time it is just sitting on its mooring. :>) In the marine switches, you usually put the switch near the battery compartment and direct wire the batteries thru the switch. Your new setup here sounds like you get to remote the actual high current switch part in the engine bay, and simply use a low voltage cab mounted switch to control it.

Larry M might know, but are the marine 3ways "make before break" ? And is your new remote solenoid version "make before break"? Depending on how you wire up the two batteries, this might be kinda important. All the memory in the stereo and other stuff would be lost as you switch from bat1 to bat2, etc... On my 92RR, if I disconnect the battery... even for an instant... the damn thing won't idle for a while until it "finds its center", I guess it needs therapy.

So, I definitely wouldn't want to lose bat voltage when switching between batteries. Even if you were to separate the winch and high draw devices onto the deep cycle, and then keep the car SLI (starting/lighting/ignition) on the main/normal SLI battery, you still need to charge the deep cycle.

Obviously there are many ways to accomplish the dual battery approach. Larry M has chosen to simply parallel two identical deep cycles together, which I favor also. Although, in my work truck I added a deep cycle battery to power all the electronic baloney I carry, I have gps, two way radios, walkie-talkie chargers, laptop, 120v inverter, wireless WIFI computer network and directional yagi antennas all running at the same time. I wired this stuff to the deep cycle and left the truck on the main battery. I use a charge splitter to divide the alt output into the two batteries. I also have a switch operated starter type solenoid to TEMPORARILY parallel the batteries if I lose my starter battery. Of course, you need to power that solenoid, and if you power it from the battery that went dead, you can't turn it on! Ha (BTDT). I guess you need to have a switch to switch the solenoid power from one to the other... heh heh.

Anyway, this setup works well for this application, because if I leave the wifi network and the two way on over night, its ok if it kills the aux battery, but I can still start the truck. But as you can see there is more electronics to throw into the mix. Larry's approach is simple, effective, and with the battery monitor is really a well rounded system. If you simply parallel the batteries, you can use a "single" battery bank monitor like Larry and I have. The "dual battery bank" monitor is quite a bit more mula.

If I go to two batteries in my RR it will definitely be the dual deep cycle in parallel... I think this gives you the best of both worlds with simple reliability. I was concerned about cold cold! cold!! weather starting, since the deep cycles are usually less potent starter batteries (lower CCA)... but remember, with TWO of them in there, the CCA (cold cranking amps at 0F) are theoretically doubled. And, for you "drive to the middle of nowhere to have all this off road fun" types, the Ah capacity (related to RC (reserve capacity)) is basically doubled too. So cooking by the Hella Foglamps at night will still be followed by a normal engine start the next morning.

You can always add a solenoid or switch to disconnect the auxiliary battery. This may be handy if you want to use a small solar charger on the aux battery alone, or want to disconnect it for some reason without hassle (like making SURE you don't drain your main battery while cooking :>).

Either way you go I would use the same exact battery in both locations. It is not a good idea to parallel two different capacity batteries together, as the current inrush can be too much for the lesser charged battery to handle when you connect them together, shortening its life or damaging the plates. The Optimas are less susceptible to this according to their website because of their plate design and lower internal resistance, but, still, its not an ideal situation. As I understand it, paralleling two different style and capacity of batteries is bad because they are always trying to equalize to their normal state, thus the larger capacity battery will be "charging" the smaller capacity battery until it's charged, and upon applying an external charge (alt or battery charger box) to the dual setup- the reverse happens, the larger capacity battery will absorb more of the charging current when applied, but then as soon as the external charging current is removed, the batteries will be fighting to equalize again. Basically it's like having a "top off" charger (the bigger battery) in line with the smaller battery, and "topping off" a battery takes a long time, so the larger is "charging" the smaller for a long time. There will be a small current flow between the two for a long time after you shut off the engine or remove the external charger.

If you go the route Larry M did, using dual yellow top deep cycles as opposed to dual starting, or different styles, there is another advantage. If you read the last post Larry sent, he mentioned that in his daily routine, his alternator wasn't fully charging his dual batteries (so he watches his battery monitor and externally charges them when needed). This is important. Starting batteries, even the red top Optima, will suffer reduced life if left in less than a full charge state for a long time. They need to be kept tip top charged all the time to be ready and able to give up their rated CA and life.

But not so for deep cycles, in fact, this is their raison d' etre. They can live in that "less than full" charge state and still act like normal, family-loving, god-fearing little batteries giving you whatever they have left. This "less than full charge state" shouldn't be a problem with a single battery since the alternator is sized to take care of that capacity of battery, but when you double that capacity, the alternator may need more time to fully charge the new "bigger" battery (the dual combo.). So, if you run dual batteries with no battery monitor, you may never know you are not fully charging your batteries (in your shorter daily routines), and without throwing a longterm external charger on them every once in awhile, they may suffer reduced lifetime, and for sure you wouldn't have as much battery capacity as you thought you were giving yourself by doubling the batteries. So by using two deep cycles, you might actually increase the service life of your new battery "system."

This last point is valid even if you run separate batteries with a charge divider like my work truck. I don't have a battery monitor on my work truck (yet, I'd need a dual style), so I never know where I am with my state of charge on my deep cycle (remember, the charge divider just takes the alternator output and gives some charge to each battery) so I plug my deep cycle in every night to a top-off charger , a little 2 amp device mounted between the grille and radiator with a plug, like a block heater, usually used for vehicle that sit for a l o n g time between uses but need to be ready to go ASAP). This little $30 device is a neat little contraption, especially if your RR is a second vehicle and it sits until you are ready to chance driving it :>) . It'll keep your SLI or deep cycle battery in tip top shape without cooking it dry. I have the solar trickle charger on the same battery also, but it only works when there's sun, not overnight in the shop.

I think when you compare the pros and cons of each battery setup, for a combo daily driver/off roader, the dual deep cycles in parallel is a winner. You get way more CCA than a single starter battery for winter, lots of RC and capacity for high draw winching (regardless if the engine is running or not!), it's a simple, less expensive route, the batteries can survive fine in a less than full charge state (until the weekend when you throw a charger on it after a week of commute slogging thru stop and go snow driving with all the electrics on, never giving your alt enough time to charge the big batteries), and yellow is a pretty color.

John.

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To: <rro@koan.team.net> Subject: RE: [rro] Optima Batteries

"It sounds like your 3position toggle switch idea is a "solenoid" or "relay" operated way of doing the old marine battery trick, 3 position switches to select bat1, bat2, both, or NONE (storage. gee, you'd think they'd call that a 4pos switch)..... marine 3ways "make before break" ? "

Most (if not all) marine battery switches are make before break to prevent the alternator from seeing an open circuit (and being damaged) when you switch between batteries.

There are a few types of battery paralleling relay systems out there. One, called the Battmax, senses when the alternator is running and automatically parallels the batteries. It also has a lead so you can momentarily parallel the batteries to start. It's pretty nice setup that we have used on some boats.

"simply parallel two identical deep cycles together, which I favor also...........I also have a switch operated starter type solenoid to TEMPORARILY parallel the batteries if I lose my starter battery. Anyway, this setup works well for this application, because if I leave the wifi network and the two way on over night, its ok if it kills the aux battery, but I can still start the truck.......you need to power that solenoid, and if you power it from the battery that went dead, you can't turn it on!"

As far as having power to energize the relay to parallel the batteries if either is dead, feed the switch from both batteries using diodes.

The problem with the simple parallel setup is draining both batteries. The one thing I typically leave plugged in is my inverter. This unit has a low voltage shut-off. You can buy low voltage shut-offs for other equipment or create a separate system. I know, this won't help you if you leave your headlights on. As far as draining the battery with a winch, even after the winch dies and the battery rests, I still have enough power to start the RR.

"If you read the last post Larry sent, he mentioned that in his daily routine, his alternator wasn't fully charging his dual batteries (so he watches his battery monitor and externally charges them when needed)."

Just want to clarify this. The alternator will not charge even a single battery to full charge during winter months. Because the alternator has no way of sensing the battery temperature, the alternator thinks the battery is fully charged (because of the higher resistance of the battery to accept a charge). So even though the battery is only at 80%, the amperage will drop to 1-3 amps. During warmer months, the alternator will not drop to this low rate until the battery is in the high 90%. When I first installed the monitor the two batteries were charging just fine. But once the colder months approached, it appeared my alternator was failing. Testing showed the alternator to be fine. When the warmer months returned, my alternator started performing better and I never had to top off my batteries. And to define cold, somewhere between 55-60F and no matter how long I drove the RR the battery did not warm up. I have since got the temperature sensing lead for my battery monitor and will be able to track this better.

"I think when you compare the pros and cons of each battery setup, for a combo daily driver/off roader, the dual deep cycles in parallel is a winner........... and yellow is a pretty color."

Go "BLUE" to get those extra studs. They really come in handy and the blue is only a couple of dollars more than a yellow.

The isolator route is also a good one if it meets your needs. For my needs, I wanted to have two deep cycle batteries for winching. If I went the isolator route, I would have also had to deal with installing a parallel switch and going to a dual battery monitor ($$). Definitely can be done, but was going to be complicated and expensive.

Larry 

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