Battery Separator (Isolator) vs. Solenoid?

[VanForNow]

I have bought a 2004 truck camper. It is equipped with a "battery separator/isolator" to charge the camper's house battery using the engine battery.

How does this differ from a solenoid, and which is preferred in terms of cost, efficiency, etc.?

 

[SternWake]

If it has a large finned heatsink it is a diode based isolator and drops voltage about 0.5 volts across it, dissipating that alternator energy as heat, slowing house and perhaps engine battery charging, and making it dang near impossible for the alternator to fully charge the battery no matter how long one drives.

Some isolators do some hinky things to attempt to negate the voltage drop, mostly by tricking the voltage regulator into seeking a higher voltage which vastly complicates the wiring, and still wastes electrons.

If it has a large finned heatsink it is wasting power, plain and simple.

There is much less voltage drop over a simple continuous duty dumb solenoid.  Properly wired, it is much more effective at charging a depleted house battery.

There are a zillion secondary battery protection devices out there. The diode based ones will protect engine battery from depleting from house loads, but really impair recharging when underway.  Whether this is an issue or not is specific to the person who own the rig and their usage, and the presence or not of other charging sources.

I use manual switches(1/2/both/Off), when I have 2 batteries, but right now only have one hard working AGM battery for both house and engine, and my switches are all turned to battery 2 as there is no battery 1.

I can do this because I have a AH counting battery monitor and know how much I am draining it each night.  Not arecommended strategy for those unfamilair with how much they use/need/ replenish.

 

[VanForNow]

Thank you, SternWake, for your reply. You are a treasure house of information on electrical issues.

Would an islolator be okay if, like my current house battery, it is a Group 24 AGM?

The former owner of the truck camper seemed pleased with the way the isolator recharged the house battery while using the Group 24 AGM, which is about a year old, as I recall.

 

[SternWake]

Without testing and actual data, and knowing how the battery was used, whether a former owner was pleased or unpleased means just about nothing.

Deeply cycled AGM batteries tend to require high amp recharges to remain happiest, and lower voltages limit the voltage delta between source( alternator) and receptacle9 battery) and slow the potential charge rate as well as increasing the time it takes to get to as high a state of charge as possible whenever the alternator is spinning.

I place AGM'S into two categories, those that have no upper limit on initial charging amps( lifeline, northstar and Odyssey) and all the others which say to limit amps to 30 amps per 100Ah of capacity, with the former being significantly more expensive and more wanting of these higher currents. The lesser AGMS mostly do not have the super low self discharge, or the ability to hold higher voltages during discharge, or the ability to just shrug off huge currents that a fast spinning well wired alternator can deliver to a depleted battery.

Generally I Dismiss optima/ spiral cell AGMS in house duty, as their design reduces capacity by ~25% compared to a rectangular AGM, which is the opposite of what one wants in a house battery. Optima's charging specs make little to negative sense last I looked. They are simply well marketed junk resting on their former good reputation from when they were made in the USA. There is however no shortage of loyal vocal optima fans, but most of their reports are from the made in the USA days, long since past.

Without performing an accurate 20 hour capacity test, one simply has little idea how well or not a battery is performing or how much capacity remains, so any claims by someone who does not have tools or interest to see how much voltage the battery can maintain for the load it is under at the depletion level the batter is at, at that time, mean nothing. To such people, ot works or it does not. if it works it is 'just like new" or still going strong. But reality is, is that most simply don't know.

Which of course does not stop the owner from claiming it works just fine, or just like new, but they have nothing to back that up, and ego and validation of their purchase are large reasons for claims which could be absurd.

It is certainly easier to just work a battery until it fails. Ignorance is bliss.

Getting the maximum battery lifespan, cycles per dollar spent ratio can also be taken to ridiculous lengths.

The happy medium is up to the end user. I generally will post what is ideal for a battery. Ideal need not be met, but neither should one just say half assing it will be just fine for you, because it is for me and we can then communicate with our heads firmly beneath the sand. Just fine for you? just fine for me. until failure.

Best thing one can do for a regularly deeply cycled battery is make sure it gets as close to fully charged every time there is a charging source present and applied. The diode based isolators simply restrict the potential for that to occur when driving. if other charging sources are available and employed to get the battery as close to a true 100%, It might not make any difference that the diode based isolator was slowing recharging when driving.

If it is one of the 30% limited AGMS, the reduced voltage delta with a big diode might actually have kept the alternator from exceeding the 30% charge rate and causing the AGM to vent, which is not instant death, but cumulatively damaging.

So, if you get to plug in every so often, do so. If you have solar, make sure it can get the battery to 14.4v to 14.8v and hold it there for a few hours. when the battery can no longer meet your need overnight, and an extended time plugged in recharging does not remedy the situation, then time for a new battery.

At that point, if the time to battery failure was unacceptable, then recharging needs improvement, if acceptable, carry on.

 

[VanForNow]

Thanks again, SternWake.

You mentioned two basic types of AGM batteries. The group 24 battery in my camper is from Cabela's, the "Advanced Angler's Pro Series." Reserve capacity 120, marine cranking amps 709, cold cranking amps 545.

Would these specs help to determine if it is one the inferior AGMs or one of the good ones, especially in relation to being hooked up to an isolator dating from 2004?

I do not presently have solar power but would like to install it in the future. I am thinking of solar panels of 200-250 watts, more if recommended.

 

[highdesertranger]

I always recommend a solenoid over an isolator. I find the solenoid to be more reliable, cheaper and you get a better charge. just make sure you get a quality solenoid. cranking amps has no place in a deep cycle battery rating. if you are looking at a battery that list cranking amps it is not a deep cycle battery, at best it's a hybrid. highdesertranger

 

[SternWake]

I am not sure who makes that battery for cabela's

The fact that it has a low CCA rating indicates thicker plates, and thicker plates are usually indicative of a battery designed for deep cycling where high CCA rating indicates thinner more numerous plates and less ability to tolerate deep cycles.

Odyssey and Northstar AGM's tout their thin plate pure lead technology and are exceptions to this generalization. They have very High CCA ratings and also claim a good cycle life.

I think the Cabela's battery might be a Full river battery, which I have in the past seen documentation saying they were 30% limited, but am not able to find that again to link it.

Look at the case shape, rather than the color., and of course the handles are very similar, The caps on the batteries can easily change even among the same manufacturer, but I think this is the most likely suspect.

http://www.fullriver.com/products/admin/upfile/DC70-12.pdf

At 70 amp hours this battery is not a high capacity battery and only( when new) had 35AH to deliver before dropping below 50% charged.

Full River AGMS are made in China, but they are a Rolls Surrette subsidiary, and Rolls Surrette is undisputed top DOG in the Flooded deep cycle lead acid battery world. Full river batteries are reported to give good service in such usage.

If it is indeed a relabelled Full River that spec sheet says 14 amp maximum current which is even lower than 30% for a 70AH battery which is surprising to me as i would expect an ~ 22 amp recommended maximum allowable initial current.



The Isolator limiting voltage and thus current into this depleted battery could be a good thing to prevent gassing, but it is not a good thing for getting it from the 80% to 100% charged range, as the absorption voltage recommended is still 14.8v, and even if your vehicle's voltage regulator was trying to hold 14.8v( it wont), only 14.3 would make it through the isolator, and that is not counting the voltage drop on the wiring between alternator isolator and cabela's battery.

Most vehicles voltage regulator's will only allow low to mid 14's held for a short while and then drop to the mid to high 13's, Which is fine for when the task it to power behicle loads and keep a slightly depleted starting battery charged, but it is very poor when there is a depleted deep cycle battery tagged onto the end of the alternator charging circuit.

Basically alternator charging is never ideal or anything close, unless one can trick their voltage regulator in deciding to seek and hold higher voltages for longer. Not easy, but not impossible. There are a few other options to make up for this lacking attribute but that is a different thread.

If you are interested in a basic tool so you can see what is really going on, a Clamp on Ammeter is a fully functional digital multimeter which one should have anyway, and has the advantage of reading current flowing through a single conductor, meaning you can see how many amps are flowing to any device/appliance, or to the battery, as long as it is clamped over only one wire, not both in the circuit.

https://www.amazon.com/Uni-T-UT210E..._UL160_SR160,160_&refRID=17NS2HT4J7CBCEWYAAKF

That is the least expensive AC and DC model I have seen, no personal experience with that brand/model. the link is an example that i had bookmarked just for this purpose. I have an older Sears Craftsman model.

It is hard to have too much solar. The usual 1 watt to 1Ah of capacity is much too little in my opinion and even 2 to 1 is too little for an AGM which is cycled to the 50% range daily, in my opinion. I have 200 watts feeding 90Ah capacity and would love 50 to 100 more watts.

When this battery can no longer meet your capacity needs, I would recommend a higher capacity battery.

Lifeline are pretty much top Dog deep cycle AGM.

the Lifeline GPL-31t is 105AH
The lifeline GPL-31XT is 125AH
The lifeline GPL-30HT is 150AH.

These Lifeline AGM batteries recommend a minimum 20% charge current when deeply cycled( no maximum amperage) and a 14.4v absorption voltage. If alternator recharging is to be a primary source of this higher amp recharging necessity, i would then recommend dumping the diode isolator, using a Nice Cole Hersee 200 amp continuous duty solenoid and 4 awg or thicker copper cabling, and as much solar as you are willing to fit on your roof.

But wait until the Cabelas battery no longer meets your needs. If it can do so easily, and your overnight consumption does not increase, then upgrading is unnecessary and you can just get a group 27 cabelas or something similar or even another 24 if space is limited.

 

[Optimistic Paranoid]

I always recommend a solenoid over an isolator.  I find the solenoid to be more reliable,  cheaper and you get a better charge.  just make sure you get a quality solenoid.  cranking amps has no place in a deep cycle battery rating.  if you are looking at a battery that list cranking amps it is not a deep cycle battery,  at best it's a hybrid.  highdesertranger

hdr, your statement is completely true if you are talking about Flooded Lead Acid batteries.  However, it appears that AGM batteries are different.  Lifeline is generally considered the best AGM's made, and even their L16T 6 volt deep cycle battery lists cold cranking amps.  1350, actually.

 

[highdesertranger]

you know what Optimistic you are right. I am stuck in a flooded battery world. highdesertranger

 

[SternWake]

Yeah the listing of CCA ratings are no longer defining whether a battery is a hybrid or starting or deep cycle.

Even Trojan is now listing CCA figures on their purely deep cycle batteries. Do note however that any group 27 or group 31(scs225) battery is still a hybrid and rated at half the number of cycles as the larger T-1275 or t-105 GC-2(6v), and they clearly say deep cycle, but are a hybrid.

Marketing wins again.

There is much more cross over in the AGM world. Where as the T-1275 is on of the very few 12v actual Deep cycle flooded batteries, with AGM, since they have inherently lower resistance, they can use thicker plates and still have the same or higher CCA figures of a hybrid or dedicated thin plate starting battery.

One can easily use a deep cycle battery to start an engine. Usually they need to be larger to have the same CCA figures as a dedicated starting battery.

Flooded Marine hybrid batteries are not true deep cycle, but with AGM, they can be.

I have a group 27 Northstar AGM TPPL( thin plate pure lead). It has a 930CCA rating and a 90AH capacity rating, and now is closing in on 500 deep cycles, and I find it to be a truly impressive battery, so far, but I can also recharge it properly and do so often. its ability to crank my engine quickly is downright impressive, especially when it was spanking new. It has lost some of that scary fast ability, but by no means is it slow. It has no issues cranking my engine at 65AH from full, and it has no issues accepting 90 amps from my alternator afterwards either.

i am expecting at least 800 Deep cycles from it ultimately, and hope for 1000 and it seems like it will reach that expectation, at least at this point. Time will tell.

 

[speedhighway46]

There is a third choice of how to keep your house batteries charged in addition to the solenoid or diode-based battery isolator. It is the FET Battery Isolator.

This device uses a field effect transistor to manage the power between battery banks. The advantage of this unit is there is no voltage drop between the input and output like on diode based isolator; and it completely automatic, managing up to three isolated outputs.

I have used an FET battery isolator for the past six years on my Peterbilt Motorhome with excellent results.

They are sold by Jamestown Distributing; just Google their website for complete details. They are made in Sweden or one of the Scandinavian countries and imported by Jamestown. High quality, top notch stuff.

 

[Optimistic Paranoid]

There is a third choice of how to keep your house batteries charged in addition to the solenoid or diode-based battery isolator. It is the FET Battery Isolator.

This device uses a field effect transistor to manage the power between battery banks. The advantage of this unit is there is no voltage drop between the input and output like on diode based isolator; and it completely automatic, managing up to three isolated outputs.

I have used an FET battery isolator for the past six years on my Peterbilt Motorhome with excellent results.

They are sold by Jamestown Distributing; just Google their website for complete details. They are made in Sweden or one of the Scandinavian countries and imported by Jamestown. High quality, top notch stuff.

http://www.jamestowndistributors.com/userportal/show_product.do?pid=63356

There are other, similar products out there, such as:

http://hellroaring.com/

And Blue Sea has some advanced products, too.

Problem is, they all seem to be a lot more money than a good solenoid.  I'm simply not sure they are worth it.

 

[highdesertranger]

that's what I was wondering. what is the advantage of those over a solenoid? seeing how they cost 2-3 times more. highdesertranger

 

[speedhighway46]

Good question. If you want the low-cost option then this is not a good choice. But I like the convenience that I know all three of my banks are being maintained to the same repeatable level all the time; and the fact that it requires no monitoring from me to make sure it's working properly.

 

[Reducto]

I started with a solenoid but after a year it stopped switching on reliably and after 2 years stopped working completely.

I wound up replacing it with a Wirthco isolator and it's been trouble free for 3 years and about 60k miles. It's not a diode type (which I would never recommend) so no voltage drop. It has logic to prioritize charging the starter battery even if the engine isn't running but the house battery is being charged by solar or something else. I have not used the jump start feature yet but that seems handy to have. A solenoid can do these things as well but you'd have to set up a switch and do it manually.

It was like $55, which I considered reasonable for a key component that should last for many years.

 

[SternWake]

Solenoids are a mechanical part and yes they do wear out.

Getting as higher rated one with silver alloy contacts makes them more durable.

Solenoids can be had on Amazon for 9$, and the quality is absolute junk.

This is a case of where shopping by price could prove to be a very poor value.

The Solenoid trigger wires also need to routed and terminated competently.  This does not mean wrapping stranded wires under a nut and tightening.

A voltmeter on dashboard, or 2 of them, One on engine battery, one on House will not only show the driver if the solenoid is not working properly, it will show the driver how long it takes a well depleted battery's voltage to rise to max voltages allowed by vehicles voltage regulator, and will also show when the engine battery is getting weak as the voltage during engine cranking will get lower and lower as the battery ages and loses capacity.

There are a thousand different products for a secondary battery system.  Classifying any one of them as better or worse in any given application is unwise.  For battery charging, the older diode based ones are unwise, but 'just fine' if more effective battery chargingis not a concern compared to making sure the engine battery is charged enough to start vehicle.

Some automatic products will combine the batteries whenever either battery is receiving charging voltages.  If one has solar, then such a product will be sending solar charge current to engine battery instead of all of this current to house battery.  This is undesirable unless one has much more solar than they need and actually cycle their engine battery.

Some of these Automatic solenoids also will consume 0.5 to 1 amps to hold batteries in parallel, wasting that amount of recharging current just to hold the batteries in parallel as well as sending some current to hold the engine batery at 14.x volts.

In this day and age it is expected that everything be automatic but there can be some serious consequences for having complete faith in some product to do what the marketers say it can do.

Marketers like to pretend their products can not only defy physics, but also wipe your heiny for you as well, while giving your fun parts a tickle.

 

[Reducto]

2 days after posting how great my Wirthco isolator was my battery voltage went WAY down even though I had been doing a lot of driving. It turns out my stock 125 amp alternator puts out enough current to trigger the over-current protection circuits on the isolator. I was fine as long as I didn't drain the battery much, but as soon as it got low enough that it pulled max current it stopped receiving charge. Those are the times it's most important for me to get power from the engine so that thing had to go.

I probably didn't need to spend $150 on the Blue Sea 500 amp auto thingie but I had a strong desire to not have to mess with this again. So far so good! It has a switch so I can leave it on-auto-off depending on my needs which would include jump starting.

I'm not sure what automatic solenoid out there is pulling 1 amp! I trust Blue Sea to publish accurate numbers and they say 40 mA to run the circuitry. The solenoid is bi-stable so it only requires power for 20 ms while switching.