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Unread 10-14-2013, 06:01 PM   #1
Matt1981CJ7
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Dual Battery Isolator or Solenoid?

Hey gentlemen,

I've decided to upgrade to dual batteries.

As usual, I've done quite a bit of research, but I'm still confused over which system is better.

The Hammer advocates constant duty solenoids, but his arguments seem a little dated. I've had another member recommend using the Hellroaring Isolator and remote switch, stating the install is much easier and the newer technology makes it a superior system.

I don't really understand the difference and I was hoping a few of you could explain it in layman's terms.

Thanks

Matt

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Unread 10-14-2013, 07:55 PM   #2
5-90
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I think much depends on your anticipated use.

If you want something that will work with minimal to no intervention, and you'll be wiring accessories to the secondary battery directly, you can use a solid-state isolator (i.e.: Hellroaring - I've gotten the most consistently positive reports from the field on their units,) wire it up, and forget about it.

If you want a flexible system where you have to keep track of what's going on, go with a constant-duty solenoid (what rating depends on a number of factors.) However, a CD solenoid allows you to wire up batteries en banc and use a trigger lead from the vehicle to automate switching, you can wire in an "override OFF" switch (to cut out the secondary battery entirely, in case it goes flat and you need to start without interference - or it goes dead, and you need to just cut the thing out until you replace it,) an "override ON" switch (so you can self-jump, with a good accessory battery,) and you probably have more flexibility in terms of how you can add, configure, and use more than one additional battery.

Thumb rules for multiple batteries:
- Batteries wired directly en banc (constantly connected in parallel) must be of the same type, capacity, and age (as evidenced by the manufacture date code tag on the battery case.)
- Batteries of dissimilar types, capacities, or ages must be "isolated" from each other when not under charge, or you get "duelling battery" syndrome (the stronger battery tries to charge the weaker, the weaker doesn't accept the charge, and both batteries end up flat - with the possibility of being wrecked.)
- Banks of batteries may have different numbers (for instance, one starting battery and three deep cycle auxiliaries,) but the provisions in the previous two points must be observed (the three deep cycles must be the same type/capacity/age, or be isolated from each other. This may be a case of "mixed isolation" - the starting battery is isolated from the deep cycle bank by a solid-state isolator, the deep cycle batteries may be manually isolated from the rest of the bank by switched solenoids. This allows you to cut out a "dead" deep cycle and preserve the capacity of the other two - but the three should still be replaced all at once.)

A "solid-state" isolator is essentially a high-current diode pack/network. A diode is, simply put, a "one-way valve" for electricity, similar to a "check valve" as used in fluid power. Like a check valve, a diode will have limitations on reverse voltage (pressure) and current in either direction (flow,) and the higher those two specifications are, the more they cost.

A constant-duty solenoid is essentially a regular manual valve - it allows full flow in both directions, when the terminals are closed.

N.B.: A "Ford starter solenoid" is not a constant-duty solenoid! I know RVers have been using them for years as "isolators" - they're cheap and readily available. But, they never seem to understand why they have to replace them every six months, when the coils burn out (no matter how patiently I tried to explain it to them, back when I was holding down a parts counter...)
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Unread 10-14-2013, 08:33 PM   #3
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5-90 is spot on in every respect, especially in regards to parallel batteries needing to be similar in every respect.
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Unread 10-14-2013, 11:08 PM   #4
Matt1981CJ7
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S-90,

Thanks for the explanation.

I'm just looking for some extra cranking amps when its cold, and I want to run my winch with the engine off without fear of draining the main battery.

I think a good quality isolator sounds like my best bet.

Thanks again,

Matt
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Unread 10-14-2013, 11:27 PM   #5
5-90
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Quote:
Originally Posted by Matt1981CJ7 View Post
S-90,

Thanks for the explanation.

I'm just looking for some extra cranking amps when its cold, and I want to run my winch with the engine off without fear of draining the main battery.

I think a good quality isolator sounds like my best bet.

Thanks again,

Matt
Easy enough to handle:

For the first point, get the highest CCA battery you can fit.

For the second, throw in an isolator and throw in the biggest deep cycle battery you can find (current capacity is often tied to battery physical size - biggest commonly available is BCI27, second-biggest is BCI24. Both are readily available, but the BCI24 will be more common.)
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Unread 10-14-2013, 11:38 PM   #6
Matt1981CJ7
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Sounds good.

There's not a lot of space, so I'm not sure about the larger deep cycle batteries. I'm already a little bummed that my original fender-mounted scissor jack will have to go away. I spent a fair amount of time refurbishing that thing.

Damn, Q-tec is sure proud of their dual-battery trays. The Wrangler unit sells for $199! Ouch.

Matt
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Unread 10-15-2013, 10:58 AM   #7
jeepster4245
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That jack fits nicely under the passenger seat...
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Unread 10-15-2013, 01:15 PM   #8
Matt1981CJ7
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Have any of you made your own dual battery tray?

If so, I'd love to see some pics, dimensions, bracing, etc.....

I can't see spending $150-200 on something that would be so simple to make.

Thanks,

Matt
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Unread 10-15-2013, 01:25 PM   #9
dhubbs
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Sonething new I have also seen lately is switching to a lithium battery. From what I have read, you can use just one lithium ion battery in place of two on diesel pickups. They also have a reserve function on them to ensure you can start them even if you do drain the battery accidently. They are supposed to recover from a start in about 5 minutes instead of up to twenty with a standard lead acid battery. They only weigh about twenty pounds. The posts are also aluminum I stead of lead, which has a much higher conductivity. The prices I have seen are around $540. Pretty steep, but to replace my two dry cell optima batteries cost me about $400. I am not sure if this is the way to go, but looks interesting.
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Unread 10-15-2013, 01:38 PM   #10
Matt1981CJ7
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Interesting. I wasn't aware they were making Lithium car batteries.

I've read the quality of the Optima batteries has gone downhill, and they no longer are worth the premium price. Any truth to that rumor?

Sears Platinum or Die Hard batteries seem to get the best reviews these days.

Matt
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Unread 10-15-2013, 01:43 PM   #11
dhubbs
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I've read that too after I bought my optimas. I went with them again just because my last two date codes were 15 years old and I haven't had too many other batteries last that long. I've had these for only a year, and just have them hooked up in parallel. I haven't had any issues, but I don't use them very hard, I use my winch maybe a few times a year as all. So I can't really comment on the quality of these yet.
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Unread 10-15-2013, 03:01 PM   #12
Matt1981CJ7
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I hear you. 15 years would probably convince me to stick with Optima, as well. Heck, I'd be happy with half of that.

My winch doesn't get a lot of work, either. But it's that one time, when you really need it, that the backup battery setup should pay for itself.

I just ordered the Hellroaring Isolator/combiner with remote switch, so I guess I'm committed to the mod, now.

Matt
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Unread 10-15-2013, 05:19 PM   #13
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Matt your a smart man though not quite as smart as that guy who recommended it to you in the first place!
That guy must know what he is talking about.
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Unread 10-15-2013, 05:43 PM   #14
Matt1981CJ7
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Ha. Actually the guy is a bit of a wind bag, but even a blind squirrel...

The isolator makes this a pricing little upgrade. I'm hoping it works as advertised.

Matt
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Unread 10-15-2013, 08:55 PM   #15
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Quote:
Originally Posted by Matt1981CJ7 View Post
Interesting. I wasn't aware they were making Lithium car batteries.

I've read the quality of the Optima batteries has gone downhill, and they no longer are worth the premium price. Any truth to that rumor?

Sears Platinum or Die Hard batteries seem to get the best reviews these days.

Matt
Optima's are now made in Mexico
WHY do you feel the need for dual batts?
You do know when one of the batteries have an issue. It will 'pull' the other down also.
I'm run'n a single BIG Interstate battery and a 80 amp alternator. Never have had any issue keep'n my Warn 8274 run'n. Even when I was on my side
Gary
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