Smart Battery Isolator/combiner

T

tom1

New member
Jan 2, 1999
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I've read a bit on this forum and other places about these, but thought I'd summarize what I've done and learned and see if anyone had any thoughts to
add.

I've seen these things called smart/automatic isolators, combiners, relays, etc, but basically they are a relay with some brains built in. You
connect the relay between your house and chassis batteries and it senses when you are charging and closes the relay to charge both battery systems.
When you are not charging, it senses this and opens the relay. Well, that's what I expected anyway, and it does do this, but with a catch that I will
get to.

I added a solar panel to the coach 6 months ago or so, and I thought a relay like this would be really neat since the solar panel would keep both the
house and chassis batteries charged while in storage. It would also charge both with the engine running or when connected to shore power. Also, a
fringe benefit was not having the voltage drop of the stock diode battery isolator when charging from the engine alternator.

This is the one I bought
http://www.littelfuse.com/products/battery-management/battery-isolators/smart-battery-isolators/48525.aspx

I bought the 85 amp flavor and decided to install it in place of the diode style isolator and keep the stock boost relays as is. I also installed a
indicator on the dash and a momentary switch for this relay (independent of the stock boost switch). I can't think of any use for the momentary
remote switch, but I had a spot for it and put it in anyways. I've had it installed for a few weeks and so far works great and as advertised. When
the voltage of either side is above 13.2 volts, it senses charging and closes the relay. But, when the charging is finished, (i.e. the sun goes down
and/or the engine is turned off) it still stays closed! This is because it's setpoint for not charging is 12.7 volts. Turns out when fully charged
the voltages are a little higher than 12.7 volts, and since there is essentially no draw on the battery in storage (except ironically the draw of this
relays coil), it stays closed. Eventually, a few hours later the voltage goes below 12.7 and the relay will open. So, in my storage scenario, this
will be a daily occurrence. Solar will top off the batteries, sun goes down, smart isolator relay drains batteries a bit, relay opens, repeat
tomorrow. I can't find a published current draw for the relay, but my guess is that it is about an amp. On a 75deg or so day, the relay is hot to
the touch, so probably about 130 F. If it wasn't for the high temps, I might have not given any of this a second thought. Even as a potential fire
hazard, I'm not too concerned. It wasn't until a thought about some critter looking for a warm spot to hang out and maybe munch on some wires while
he's there that I got to thinking that maybe this isn't a good idea.

I did notice some other similar products. A friend of mine uses this one on his SOB

https://www.bluesea.com/products/7601/m-Series__Automatic_Charging_Relay_-_12_24V_DC_65A

It only draws 90 mA when closed so likely doesn't get hot. It's only rated at 65 amps though, but when you consider the 60 amp breaker to the house
batteries, it would probably work. I didn't mention this above, but the alternator is connected directly to the chassis battery in this installation,
and my solar only can make about 5 amps.

Here is another bluesea type. This one has a momentary coil for moving the relay either direction so it doesn't have a continuous electrical load in
either state. Seems like the best solution to me. Costs a bunch though.

https://www.bluesea.com/products/7620/ML-ACR_Automatic_Charging_Relay_-_12V_DC_500A

What do you guys think?

Thanks,

Tom C
77 Kingsley
Huntington Beach, CA

--
Tom

77 Kingsley. Mostly Stock, 455, Quad bag, tachometer, 16"wheels, Macerator.
Southern California, huntington beach
 
Not sure I would want the "hot" for the same reason you are concerned about it. In my first GMC I removed the isolater and installed a Yandina
combiner (that JimK now sells) which is a solidstate device that does basically the same thing as the smart relay does. I do not remember it ever
being hot. It connects both sides whenever there is charging voltage on one side and not the other as I remember it. On my SOB I had a Xantrex Echo
Charge which works the same way the Yandina does. I plan to install a Yandina in the new GMC also. JWID

--
Tom Lins
Elkton, FL
77 GM Rear Twin
 
There is really nothing much wrong with the good old isolator. Easy to
check, durable, no moving parts. Tried and true.
Jim Hupy
Salem, Or.

I've had very good luck with these:
http://shop.pkys.com/Victron-Energy-Cyrix-ct-1224V-120A-
Intelligent-Battery-Combiner_p_6769.html?gclid=EAIaIQobChMI4oG15-_d2AIVwpd-
Ch395QDaEAQYASABEgKjevD_BwE
--
Justin Brady
http://www.thegmcrv.com/
1976 Palm Beach 455

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> There is really nothing much wrong with the good old isolator. Easy to
> check, durable, no moving parts. Tried and true.
> Jim Hupy
> Salem, Or.

I agree. Keeping the chassis battery charged on the existing solar panel is what started this for me.

Tom

--
Tom

77 Kingsley. Mostly Stock, 455, Quad bag, tachometer, 16"wheels, Macerator.
Southern California, huntington beach
 
True, but an isolator does not fulfill the same set of requirements that
the combiner does.

It's the same with the buzz box, which is also quite simple and reliable.
But it is also noisy and will sulfate batteries with its constant voltage.
A newer converter/charger will use a multi-stage charging plan to keep the
batteries charged without sulfation, and to charge them more quickly in the
first place.

And, with that greatly improved converter/charger, it's now reasonable to
want to charge or tend all the batteries if charging any of them. The
isolator charges the house battery when running the engine, and that's all.
With a combiner, that fancy new converter/charger will also tend the engine
battery while the coach is plugged in.

The Yandina combiner will connect the two batteries any time there is over
13.2 volts present on one of the two banks. It will isolate the batteries
when there isn't. It does not use a big diode, and does not get hot. It's
potted in epoxy, so no worry about critters making a home in it. It's quite
easy to install. It remembers its there, unlike Ken Burton's $1 combiner (a
wire with two alligator clips), which is subject to advanced CRS. Finally,
it's no more expensive than an isolator, especially if you wait for the
occasional deal--It's significantly less expensive than the BlueSea.

Rick "a few things have improved in the forty years since the coaches were
new" Denney

> There is really nothing much wrong with the good old isolator. Easy to
> check, durable, no moving parts. Tried and true.
> Jim Hupy
> Salem, Or.
>

>
> I've had very good luck with these:
> http://shop.pkys.com/Victron-Energy-Cyrix-ct-1224V-120A-
> Intelligent-Battery-Combiner_p_6769.html?gclid=
> EAIaIQobChMI4oG15-_d2AIVwpd-
> Ch395QDaEAQYASABEgKjevD_BwE
> --
> Justin Brady
> http://www.thegmcrv.com/
> 1976 Palm Beach 455
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
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> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
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>

--
'73 X-Glacier 230 "Jaws"
Northern Virginia
Offlist email: rick at rickdenney dot com
 
Except that it won't charge the engine batteries from the house batts :)

I like plugging the coach in for the winter (or a month or whatever) with a 30a cord and being finished and knowing when I go to start it the engine
and house will be 100%. Same with solar. If I sit in the sun for a few hours I know both batteries are topped up. It's very convenient, and it
eliminates the need for the boost circuit.

There is nothing wrong with an isolator, but they also don't serve the same purpose.
--
Justin Brady
http://www.thegmcrv.com/
1976 Palm Beach 455
 
I'm with Jason. And it doesn't take a 30 amp circuit unless you're running the A/C units and the water heater. I'm in the process of putting up some
plastic conduit and an outdoor box with a 50 Amp plug. The extension cord out the window looks tacky.

--johnny
--
76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
"I forgive them all, save those who hurt the dogs. They must answer to me in hell" - ol Andy, paraphrased
 
Please be cautious with "Smart Combiners".

As many of you know, I was part of a boat electrics service group for many years. (This is where the coach was most used for 6 years.) While I like
and have installed and replaced combiners as well as isolators, the combiners that are not rated at starting current (~400A for a 455) are easily
damaged if left engaged when cranking. This can happen any time the demand combine capability is used even if the main engine battery is at a capable
state of charge.

When a combiner fails, they often indicate that they are functioning properly, but in actual fact are not. The indicators are that it has engaged and
there is any differential across the two main posts, it is toast. Repair is somewhere between impractical and impossible. Carry the KenB 1$ combiner
in your kit just in case.

Matt
--
Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan
OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Twixt A2 and Detroit
 
I've got a couple 30amp RV receptacle in the shop, but I just plug into a 15A with an adapter and leave the large cord in the coach. That way I don't
trip over the large cord when working in the shop.

The worries about the 0.7V drop across the isolator is a non-issue because the voltage sense line to the alternator is connected to the engine
battery. The alternator will output a slightly higher voltage to make up for this. There is likely more voltage loss across the #10 wire from the
alternator to the isolator than there is across the isolator itself.

I did the combiner across the isolator installation. It makes for a quick and clean installation, and takes some load off the combiner.

Unless it was a high amperage rate combiner, I would not use the Start boost function in them.

The GMC holds the beer fridge for the shop so I need to keep the fridge going too :)
--
Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.
Hubler 1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that
 
> Please be cautious with "Smart Combiners".
>
> As many of you know, I was part of a boat electrics service group for many years. (This is where the coach was most used for 6 years.) While I
> like and have installed and replaced combiners as well as isolators, the combiners that are not rated at starting current (~400A for a 455) are
> easily damaged if left engaged when cranking. This can happen any time the demand combine capability is used even if the main engine battery is at
> a capable state of charge.
>
> When a combiner fails, they often indicate that they are functioning properly, but in actual fact are not. The indicators are that it has engaged
> and there is any differential across the two main posts, it is toast. Repair is somewhere between impractical and impossible. Carry the KenB 1$
> combiner in your kit just in case.
>
> Matt

Interesting. Some units like this one have "start isolation", they say to protect sensitive circuits from voltage sags, but it seems it would protect
against the failure mode you've observed too.

https://www.bluesea.com/products/7610/SI-ACR_Automatic_Charging_Relay_-_12_24V_DC_120A

Tom

--
Tom

77 Kingsley. Mostly Stock, 455, Quad bag, tachometer, 16"wheels, Macerator.
Southern California, huntington beach
 
Matt, the Yandina 160 includes overload, but is rated for 400 amps closing
current. Even if you attempt to start a 455 solely through the combiner, it
will withstand 400 amps for the 2 seconds or so that it takes to go into
overload and shut down. It is overload-protected, and includes an LED
indication to show when it is in overload.

The trigger voltage is specified at 13.1 volts, so I think it will play
better with the PD converters than their 100-amp combiner. When I install
this one, I'll keep an eye on it for that. My first combiner, that I
killed, always stayed combined at the 13.2 sustain voltage. The one I
bought to replace it (I couldn't bear to use the warranty) combines at
13.2, and sometimes won't combine, but I think the problem is with my
converter. That will be a spring project.. But it will combine when the
converter senses high charging current and steps up the voltage to a higher
charging level.

The Yandina combiner is also warranted for life, even against lightning
damage.

And it is current-limited using its lead-in wires. If the engine battery is
capable, starting the 455 will not overload a Yandina combiner even if it
is combined.

Of course, there is nothing to prevent putting a 200-amp fuse or breaker in
line with the combiner, though I suspect the Combiner 160 already has that
internally.

Nothing is perfect and they do sometimes fail. I think KenH has lost one or
two over the years, and I blew one up when in a fit of stupidity I wired a
battery backwards. That stunt took out the alternator, too, though it
didn't fail completely until a couple of days later. The same could be said
for isolators. People say that isolators never fail, but I've been reading
GMCnet for many years and I've certainly heard of many failed isolators,
plus the one I had that failed. These big batteries can supply a lot of
current.

Rick "who likes not having to worry about a failed isolator causing a loss
of field sensing and runaway voltage" Denney

> Please be cautious with "Smart Combiners".
>
> As many of you know, I was part of a boat electrics service group for many
> years. (This is where the coach was most used for 6 years.) While I like
> and have installed and replaced combiners as well as isolators, the
> combiners that are not rated at starting current (~400A for a 455) are
> easily
> damaged if left engaged when cranking. This can happen any time the
> demand combine capability is used even if the main engine battery is at a
> capable
> state of charge.
>
> When a combiner fails, they often indicate that they are functioning
> properly, but in actual fact are not. The indicators are that it has
> engaged and
> there is any differential across the two main posts, it is toast. Repair
> is somewhere between impractical and impossible. Carry the KenB 1$ combiner
> in your kit just in case.
>
>
--
'73 X-Glacier 230 "Jaws"
Northern Virginia
Offlist email: rick at rickdenney dot com
 
> Matt, the Yandina 160 includes overload, but is rated for 400 amps closing current. Even if you attempt to start a 455 solely through the
> combiner, it will withstand 400 amps for the 2 seconds or so that it takes to go into overload and shut down. It is overload-protected, and includes
> an LED indication to show when it is in overload.
>
> The trigger voltage is specified at 13.1 volts, so I think it will play better with the PD converters than their 100-amp combiner. When I install
> this one, I'll keep an eye on it for that. My first combiner, that I killed, always stayed combined at the 13.2 sustain voltage. The one I
> bought to replace it (I couldn't bear to use the warranty) combines at 13.2, and sometimes won't combine, but I think the problem is with my
> converter. That will be a spring project.. But it will combine when the converter senses high charging current and steps up the voltage to a
> higher charging level.
>
> The Yandina combiner is also warranted for life, even against lightning damage.
>
> And it is current-limited using its lead-in wires. If the engine battery is capable, starting the 455 will not overload a Yandina combiner even if
> it is combined.
>
> Of course, there is nothing to prevent putting a 200-amp fuse or breaker in line with the combiner, though I suspect the Combiner 160 already has
> that internally.
>
> Nothing is perfect and they do sometimes fail. I think KenH has lost one or two over the years, and I blew one up when in a fit of stupidity I
> wired a battery backwards. That stunt took out the alternator, too, though it didn't fail completely until a couple of days later. The same could be
> said for isolators. People say that isolators never fail, but I've been reading GMCnet for many years and I've certainly heard of many failed
> isolators, plus the one I had that failed. These big batteries can supply a lot of current.
>
> Rick "who likes not having to worry about a failed isolator causing a loss of field sensing and runaway voltage" Denney

Rick,

I kind of hate to say this, but you are talking about your capability and understanding and sort of thinking this is universal. We all do this until
we have to go out in the world and get our face smashed into the truth. Most people assume (we may get back to that word) that they are in the middle
of that huge bell curve that represents humanity....
Well, I got news for you. Just being a successful GMC owner puts you way out on the right hand end of that curve. Most GMC owners are. If you have
any doubt of this go read the other RV boards. And if that doesn't do it, try FaceBook. I have given up there. I spent way too much time telling
writers to not do what they just read. It didn't always work, so now I know of two coaches lost to bad advice.

It is all a crap-shoot. Every time I think I have made something idiot proof, I get introduced to a better idiot.

My work has largely been little diesels, they are cold blooded and always take a lot of cranking - even the glowplug versions. The peak currents are
also very high. That happens at a 18~20 CR even with a heavy flywheel.

Yes, isolators do fail, but a yellow canary level wrench using the Hazard Fright meter we provided can diagnose the failure with instructions over
VHF. Combiners fail too, but the good diagnostic is above that level.

In the documentation we always provided, there was a complete limp-home procedure with how and what to move where to get things to work so the vessel
could get where repairs could be effected. This is difficult to provide with the wire-lead Yandina, so we had to package a kit (included in the quote
and not optional) with a set of pre-made cables and maybe even the wrenches to install same. This is not usually an issue with a coach. Yes, Yandina
may have a lifetime warranty, but there needs to always be a work-round to get you underway when in a remote location.

Do I dislike combiners? No, but they have more components and more modes of failure than does a diode isolator. I can tell you that I have replaced
many more combiners than I have isolators. Fortunately, the marine applications of the level vessel I work had not reduced to the simple isolation
contactor that is now the common item in the motorhomes I see.

Matt
--
Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan
OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Twixt A2 and Detroit
 
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