Cons of a Solenoid Dual Battery Isolator

[danos]

Hi

I am looking at a putting a dual battery system in my 98 3LD Hilux. Before you ask, yes i have read the 000's of posts about this topic that seem to cover just about everything on battery systems.

I want to know what at the bad points to using a simple, cheap solenoid isolator for charging two batteries.

From the info I have read they seem to be:
1. Power spikes - Dont have a engine computer so ok there
2. Flat aux battery bringing down starting battery - Is this really a problem? I could put a manual overide switch to prevent this?

Also, i'm not sure how well they charge each battery or am I aware of other bad points.

Any help would be appreciated.

[Ruffy]

Mate i've had several designs of the cheapy solenoid and haven't had a drama. You just have to be mindful of the system.
I had an XH falcon i used to camp with a fair bit. I simply had a switch on the dash to turn on the solenoid.
In my 60 i had a solenoid that was on whenever the ignition was on.
The only down side is what you mentioned, because they're both linked if one goes flat or your alternator drops it's guts then you lose both batteries.
As i said, be mindful of those things.
A red arc or similar isolator is good if you can afford it.
Red arc's are 195 bucks. I now have one in my GQ and it's good not to have to worry about it.
Oh i have a simple solenoid set up in my rodeo as well. Works fine.

If you plan on running a fridge or similar where the Aux battery may get quite discharged then you'll need a decent drive to charge both batteries as your start battery will discharge into the flatter Aux battery when you turn the solenoid on.
Hope this helps
Cheers Dan

[danos]

Yeh thanks.

I'm heading into town on Sat to hopefully pick up an engel. I've been eyeing off a traxide but just wanted to rule out the cheaper alternative.

Hmm the point about having to go for a long drive is a good one. Instead of charging yoru starter, it'll have to charge the started plus the aux, which i'm assuming will take almost twice as long.

Redarcs go for $100 on ebay at the moment (~ $ traxide) but I dont want to debate about which is better as its been done to death in other threads.

[drivesafe]

Hmm the point about having to go for a long drive is a good one. Instead of charging yoru starter, it'll have to charge the started plus the aux, which i'm assuming will take almost twice as long.

Hi danos, unless you have a very small alternator, it actually won’t take any longer to charge two batteries as it will to charge one.

Most alternators are capable of charging three batteries at the same time and still be able to provide power for everything else that needs power.

Cheers.

[trains]

I use this type of system on my 95 lux as the solenoid was already there.
Originally it was wired up so that when the ign was on, it would join the two batts together.
I just put an on off switch on the wire to the solenoid, so now when the ign is on, I can choose to have either both batts together, or seperate.

I choose to start with them disconected from each other, that way, if my starter batt is failing, I know, and can use the switch to bring in the other to start it. and then replace the batt as soon as practical.
If there both together, one will support the other till they both die, and your stuck with 2 dead batts.

But you probably already knew that.

I also like the fact that you can open up the basic solenoid, and clean the contacts, where as most others are definately not field servicable.

Trains

[danos]

Exactly trains. I think it will work ok.

http://www.lcool.org/technical/90_serie ... ttery.html

Instead of a DPDT switch ill use a SPDT (simple on off)

What type of solenoid should i be looking for? Cole Hersey 80A continuous duty rings a bell.

Will get it form Supercheap Auto this weekend.

[White61]

Energise the solenoid from your ignition so the batteries are only connected with the key on. Then run the solenoids earth wire to the windings in the starter motor (switched side of the starter solenoid). This will earth through the starter motor windings until you start cranking. You will start off only 1 battery. Add a switch to give you a chassis earth when your main battery is dead.

[Mytqik]

The solenoid is fine as long as you buy a good quality one, with silver contacts. I have had 1 weld itself shut and another corode itself to pieces (no beachwork either).

I then changed to one a 150A Bisolator: http://www.sidewinder.com.au/page154.html

These are just fantastic. They isolate the batteries when the ign is off, so no flat aux battery when parked, you can join the batteries together to jump start off the aux (if needed), and you can completely isolate the AUX so only the main is receiving charge from the ALT for a faster charge. They also do a few other things.

They also have no moving parts and no voltage drop.

I have no idea why these aren't more popular. So easy to fit.

(I am in no way affiliated with sidewinder, I am just an extremely happy customer)

[drivesafe]

They also have no voltage drop.

I’m not sure where you get your info from Mytqik, but these devices most certainly have a voltage drop when under load, at the very time when a battery is low and the highest possible voltage is required, this devices will apply a voltage drop that will result in a much longer charging time being need to charge the battery as compered to using a common good old fashioned garden variety solenoid, like those being discussed above, which I might add are not only heaps cheaper but will do a better job.

I have no idea why these aren't more popular.

The above reason is why more people DON'T use them

Cheers

[me3@neuralfibre.com]

Most isolators are just a solenoid (relay) in a pretty box. It's the controller smarts they claim add the bucks.

Personally Redarc and Traxide (different bahaviour) are the ones I like.

Paul

[danos]

Can you use a relay to do the switching or is a solenoid the choice because it can handle the heavier loads (amperage?)?

[drivesafe]

Hi danos, it all depends on what you are planning to switch.

Contrary to most beliefs, a 40 amp relay will do as an isolator for most dual battery systems.

If your considering using the isolator to jump start then you must take into account the much higher currents and you them have to use at least a solenoid that has a momentary current rate of around 200 amps ( this is always much higher than the constant current rate ).

Cheers.

[Mytqik]

They also have no voltage drop.

I’m not sure where you get your info from Mytqik, but these devices most certainly have a voltage drop when under load,

Drivesafe did you even read the link I posted???

Unless you count 0.0012V a voltage drop to worry about. I am sure you would suffer more of a voltage drop across dirty battery terminals than that.

These are made from MOSFETS not diodes like the old school isolators. As I said before the MOSFETS have no moving parts, so nothing to wear out/weld shut, and can handle 600A for 20sec to jump start.

I have no idea why these aren't more popular.

The above reason is why more people DON'T use them

Cheers

Horses for courses. I have had no dramas with mine, it was as cheap as the Redarc and had more features.

[drivesafe]

Mytqik, the voltage drop you are using to show how supposedly good these devices are, is while the unit has next to no load on it, ALL mosfets will have some form of voltage drop once a load is applied and in this case by the time the load gets to about 15 amps the voltage drop would be approaching .2 volts at beast and 15 amps is no more than about half the current any decent battery would draw if it needed a good charge.

I’ve already seen a lot more info on this device, info that has been conveniently omitted from all the hype.

One more point, mosfets have been used for years before this thing came along and anybody with any real experience with automotive electronics knows only full well that they do not work well in standard battery isolators.

The individual pushing this prehistoric technology has a habit of promoting devices and ideas that leave much to be desired and in a number of cases are down and out right dangerous, so while your peddling his wares for him, consider the harm you might be bring to others.

Cheers.

[toecutter]

G'day all, this is my first post.
Using a solenoid is the same system that I have used on my Defender, Jeep and now on my GU Patrol.
All I have done is connect it to my ignition so that it kicks in when the ignition is on...simple.
I have had Auto electricians look at it and they have said that there is nothing wrong with this set up.
IMHO the "smart solenoids" on the market are somewhat a rip off. As soon as you put it into a store like AJB or TRM or whatever, you can add an extra $50-$100.

Incidentally, when I first got a dual battery setup on my Defender, in '99, by one of the 4x4 accesory stores, they only used a solenoid and charged me somewhere around $600 for the privledge, it was then that I decided that if it was that simple, I would do it again on my other two cars later on.

[danos]

Steering this thread in a slightly different direction...I want to run some cable to the rear of the car for the fridge and an additional cigarette plug (maybe spottie or camp light).

Any tips on doing this ie. cable size, including a fuse etc?

I have read to use at least 13mm cable (to minimise voltage drop) and run an earth back to the engine bay but I am unsure on the fuse and how many amps it should be?

The cig lighter plugs I want to use are these
http://cgi.ebay.com.au/DC-power-dual-ci ... dZViewItem

If running two plugs off the same cable should i use a bigger or smaller fuse? or run separate cables? or heavier cable?

The fuse can be installed anywhere along the positive cable?

Thanks

[drivesafe]

I want to run some cable to the rear of the car for the fridge and an additional cigarette plug (maybe spottie or camp light).

Any tips on doing this ie. cable size, including a fuse etc?

If running two plugs off the same cable should i use a bigger or smaller fuse? or run separate cables? or heavier cable?

The fuse can be installed anywhere along the positive cable?

Thanks

Just so happens danos, I now have a kit that has everything in it you want but whether you get it from me or not, here’s how to do it.

Cheers.

[danos]

Thanks very much. I had a look on the site (http://www.traxide.com.au/DBS.html) but the link doesn't work, yet.

As for the cable size running to the rear of the car, what do you think of the comments made in this ?http://www.springers.com.au/news/defaul ... icle&ID=20

[drivesafe]

Hi again danos, sorry about the lack of info but I did warn you we have only just put that kit together, if you were going to put an auxiliary battery in the rear then yes you need to go to heavier cable and again the diagram below is an other one of our kits that will give you an idea of how to wire up a battery in the rear of your veicle and this one does have all the info on my site.

Here's the link to it

http://www.traxide.com.au/SC80PCWK_Info.html

[danos]

Cheers mate! I realised it was a new product so was willing to wait but thanks anyway its really appreciated.

Heading into Darwin soon to pick up the parts.

[danos]

The solenoid has two smaller terminals. One connects to earth and the other goes to the....?

...accesories wire in the ignition?

If i find the acc wire that the cd player runs off can I tap into that and install a switch to isolate solenoid completely?

Thanks

[Bluey]

the 2 small terminals are to switch the solenoid on and off, same as a normal relay. wire one to earth and the other to 12 volts. this 12v can be direct from battery (if you do this then might as well remove solenoid), from the acc, from a switch on dash, from a piece of electronics that senses the voltage and engages solenoid at a preset voltage etc etc


cheers

[danos]

Thanks.

I ended up wiring it via a switch to one of the ignition wires. I wasnt sure what wire it shoudl go to but it works so i'm happy.

[lexi]

I switched a big solenoid from a smaller relay fed from battery charge light. You are cranking with main battery till light goes out then two batterys get connected.........and disconnected when engine off.

Alex

[Bluey]

in my dual batter sertup i have 2 cranking batteries, ac delco's, connected by a solenoid with a voltage sensor. not redarc brand, but similar in operation

batteries less than 9 months old and was having issues of main battery going flat. i mean less than 6v flat. after stuffing around heaps (checking connections, removing $250 car alarm that i installed etc0 the battery went back to the shop for second time, they charged it up and then checked its charge for 2 weeks. nothing wrong with. so i put it back in and connect to solenoid.

couple of days later when wiring up my turbo timer i notice the metal can of the solenoid is real hot. after 2 secs would burn. this is with solenoid off. checked the solenoid and it seams ok, but when you measure volts on each side and switch it on there is no change. batteries should equalize, volts change slightly etc

so looks like a dead solenoid. was at least $150 of ebay. getting a 200A continuous rated, silver contacts solenoid of auto lecky tomorrow, price around $80. next week will buy voltage switch kit from jaycar to turn it on and off $30. will let you know how it goes


ps sorry realised my post is huge.
cheers

[sidewinder]

Here is another option for wiring the batteries in the camper or rear of the vehicle.

[drivesafe]

Now Derek, just out of curiosity, why would anybody in their right mind, want to pay a motza to fit a device that would cause their auxiliary batteries to take longer to charge than the simple and MUCH cheaper set ups that are being discussed in this thread.

That makes sense!

[sidewinder]

BiSolators do not have a voltage drop problem like solenoids that are a few months / years old. Brand new solenoids work well yes but deteriorate with age. Perhaps you are confusing this product with a diode.

There is no decreased charge rate. Each battery is charged as if it was the only battery connected to the alternator. (Depends on your wiring configuration.)

There are up to 5 ways to wire the system. You can even fit 2 BiSolators to charge 4 batteries independently if you wish.

More information on BiSolators from another supplier is available here: http://www.hellroaring.com/4wheel.php

[me3@neuralfibre.com]

Now Derek, just out of curiosity, why would anybody in their right mind, want to pay a motza to fit a device that would cause their auxiliary batteries to take longer to charge than the simple and MUCH cheaper set ups that are being discussed in this thread.

That makes sense!

Without diving into the whole debate, when I did a heap of research into it (and I've never met drivesafe) his system was one of the best designs I saw. The only things better was over $1000. In terms of bang for buck, his solution made me redesign my plans for under my bonnet, as I could do more, for less $$. The Traxide systems makes that huge lump of lead called a main battery useful.

Paul

[me3@neuralfibre.com]

BiSolators do not have a voltage drop problem like solenoids that are a few months / years old. Brand new solenoids work well yes but deteriorate with age. Perhaps you are confusing this product with a diode.

There is no decreased charge rate. Each battery is charged as if it was the only battery connected to the alternator. (Depends on your wiring configuration.)

There are up to 5 ways to wire the system. You can even fit 2 BiSolators to charge 4 batteries independently if you wish.

More information on BiSolators from another supplier is available here: http://www.hellroaring.com/4wheel.php

What's inside the Bisolator? I'm assuming it's a big MOSFET? Is information on resistance available? (preferably plotted against temperature). My first impression that I'm dubious is the big heatsink. It's easy to tell if something is losing power (voltage drop) - it's radiated as heat. Most solenoids don't get hot enough to need a heatsink, meaning pretty low resistance. Don't get me wrong, I would prefer a solid state solution, but most seem to have too high an internal resistance. 0.6v for a silicon diode (fixed). 0.2v for a germanium, but no high current option. MOSFET should have very low, but would vary somewhat with current. A voltage drop will reduce the voltage seen at the battery, which will reduce charge current, which will increase charge time. If anyone looks at the charge rate graphs, 0.6v is a huge change in charge time and current acceptance. This doesn't really matter if your alternator can only deliver 40A anyway, as probably only 20 is available to charge the batts. For mine with a factory 120A alternator, and over 80 available for battyer charging, this could change my effective charge time from 1 hour to 3 or more.

When I dug (and I dug lots), really the only ideal solution is one that put temperature sensors on the batteries, and directly controls the alternator exitation and output. Anything less is nothing more than a fancy switch, one way or another. Parallel charging has NO perceptible negative impacts, and I have the industry docs to prove that. The problem is determining state of charge and optimising charge rate. That requires an interactive alternator and temperature monitoring of the batteries. Ideally it also would prefer individual cell charging as opposed to a bank of 6 in series to make up a 12v battery. Luckily the self balancing effect of lead acid cells copes with this pretty well, unlike LiIon. My cruiser alternator is temperature compensated (I think) BUT it's the alternator temperature they adjust for, not the battery temp. Bit of a "guess" as opposed to an ideal solution, I'm sure everyone can see the flaws inherent.

Finally, all battery specs I could find would not specify any rate of charge information above 50deg C as this was thermal runaway area, regardless of construction type (Flooded Start, Flooded Deep, AGM, Gel). I know batteries under the bonnet get over this temperature, so the whole charge debate in pretty dubious anyway. It pretty well relies on the fact that although the charging is less than ideal, lead acid batteries are tolerant of abuse and take a while to die, die slowly, and aren't easy to monitor for "health".

It's just a switch after all.

Paul