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Old 09-20-2018, 10:38 PM   #1
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Default Isolator doesn't isolate?

Maybe someone can point out the flaw in my logic regarding the battery isolator in my 2017 Pleasure Way Lexor.

Not long ago, I noticed that the solenoid in the Eaton/Sure Power 1314-200 unidirectional isolator remained energized after engine shutdown and in consequence the chassis and house batteries remained connected. This condition persisted overnight, and perhaps longer, which doesn't seem right. The batteries should become isolated, right?

I concluded I had a faulty isolator and installed an exact replacement, but the latter behaved exactly the same. So I guess I was wrong.

Delving into the isolator specs revealed that the isolator should energize once the chassis battery voltage reaches 13.2 VDC or higher and de-energize when it falls to 12.8 VDC or lower.

It seems to me that the lithium coach batteries will normally be well above 13 VDC and will therefore always keep the chassis battery at the same voltage, so the voltage can never fall to 12.8 VDC and the batteries can never disconnect from one another.

I must be missing something--surely PW would have problems with hundreds of coaches if the isolator behaves that way in all current (no pun) model coaches.

BTW, I verified all salient connections and established that PW did the wiring correctly.
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Old 09-20-2018, 10:57 PM   #2
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I think you have it diagnosed correctly that it is the lithium batteries holding the separator closed all the time. It is a big waste of power as the coil will use about 1.5 amps continously.


A call to Pleasure-way is probably in order and ask them why it it that way, and what they are going to do about it.


If they bail, installing a low power drain separator with an override switch to turn it on and off if needed could be installed.
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Old 09-21-2018, 09:25 PM   #3
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It's disappointing that PW missed that during the design phase. It would appear to be an overlooked part leftover from lead acid house systems.

A relay or separator that is triggered (latched) only by the ignition would be a never-have-to-think-about-it solution.

I added a separator to my van and added a switch that interrupts the separator's ground wire to turn it on or off it ever desired. A relay triggered by the ignition could be used in place of the manual switch to automate the manual turning on or off. I don't know if the Eaton/Sure Power separators have a ground wire or if interrupting it would turn it it on or off though.

It is for PW to figure out at this point though - hopefully they don't have too many coaches to fix.
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Old 09-22-2018, 12:38 AM   #4
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Thank you Booster, for confirming that I'm not nuts.

Markopolo, great minds think alike. The relay solution popped into my head just a little before you posted your note.

I talked to PW's electrical supervisor and the gist of the conversation was that what I've seen isn't anomalous; it's normal behavior.

I'm likewise disappointed and I intend to write a letter to CEO Dean Rumpel suggesting that they really ought to do something about it. But not before I've implemented my fix, so I can include photos showing how simple it is.

EDIT: The Eaton/Sure Power unit does have a separate ground. The temporary workaround I've been using is manually disconnecting the ground wire upon parking at the end of the day and then reconnecting it prior to reembarking.
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Old 09-22-2018, 04:24 AM   #5
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Whatís wrong with having the house batteries keep the chassis battery charged? Thatís what my AGM system does when I leave it plugged into shore power between trips.
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Old 09-22-2018, 11:25 AM   #6
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Nothing wrong with keeping the chassis battery charged. That's what is done in both my current RV's. It's useful on RV's that are not driven for weeks at a time.

The automatic joining usually only occurs when a charging source is applied to the system. In this example, no charging source is applied yet the separator remains latched.

The issue here is the mismatch of battery chemistries and the voltage disconnect set point at 12.8V on the Sure Power unit. The expensive lithium batteries will continuously discharge into the lead acid chassis battery until the lithium battery is pretty much depleted.

The separator in the the PW RV won't disconnect until below 12.8V.
12.8V is a fully charged or still being charged lead acid battery.
12.8V is a lithium battery that is nearly depleted (maybe 20% SOC).

The setup needlessly deep cycles the lithium battery leading to earlier than expected failure. It also would needlessly stress the alternator as near full alternator output would be accepted by the lithium batteries for an extended period of time because the lithium battery will more often be at a very low SOC.

There's another possible issue with the automatic joining of the lithium and lead acid batteries when plugged into grid power. If PW (note the IF) used one of the single stage "lithium" chargers like the PD9145ALV then that outputs a steady 14.6V ! Too much for the lead acid battery (way too much for a continuous float charge). Lead acid batteries are typically floated at 13.2V.

https://www.progressivedyn.com/wp-co...argers_lit.pdf
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Old 09-22-2018, 12:08 PM   #7
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Quote:
Originally Posted by lmittell View Post
Thank you Booster, for confirming that I'm not nuts.

Markopolo, great minds think alike. The relay solution popped into my head just a little before you posted your note.

I talked to PW's electrical supervisor and the gist of the conversation was that what I've seen isn't anomalous; it's normal behavior.

I'm likewise disappointed and I intend to write a letter to CEO Dean Rumpel suggesting that they really ought to do something about it. But not before I've implemented my fix, so I can include photos showing how simple it is.

EDIT: The Eaton/Sure Power unit does have a separate ground. The temporary workaround I've been using is manually disconnecting the ground wire upon parking at the end of the day and then reconnecting it prior to reembarking.
When I replaced the AGM batteries in my DIY Promaster conversion with LiFePo batteries my isolator behaved the same way you described.

I did a little research and I believe that no one makes a voltage sensing isolator that works correctly with Li batteries. Apparently the isolator technology hasn't caught up with Li yet.

Using a relay that is trigged by the ignition will solve the problem of 'not isolating' but I think it will still have the problem if over charging the Li batteries while you drive.

Some people, including me, believe Li batteries will last longer if not charged to 100 percent.

I installed a Victron BMV 712S battery monitor that uses a shunt to count amps in and out to determine the state of charge (SOC). It has an internal programmable relay function that I have set to open when the SOC reaches 95 percent and close when it drops below 90 percent.

The ground wire on my isolator goes through a relay triggered by the ignition and then through the relay in the BMV 712.

The batteries are only combined when the ignition is on and the SOC is below 95 percent.


Most versions of the Victron BMV 7xx have the relay function, but the 712S has a latching relay that only draws current when switching and is the one they recommend for use with Li batteries.


I agree, this is something PW should have designed for.
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Old 09-22-2018, 12:22 PM   #8
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Quote:
Originally Posted by tgregg View Post
When I replaced the AGM batteries in my DIY Promaster conversion with LiFePo batteries my isolator behaved the same way you described.

I did a little research and I believe that no one makes a voltage sensing isolator that works correctly with Li batteries. Apparently the isolator technology hasn't caught up with Li yet.

Using a relay that is trigged by the ignition will solve the problem of 'not isolating' but I think it will still have the problem if over charging the Li batteries while you drive.

Some people, including me, believe Li batteries will last longer if not charged to 100 percent.

I installed a Victron BMV 712S battery monitor that uses a shunt to count amps in and out to determine the state of charge (SOC). It has an internal programmable relay function that I have set to open when the SOC reaches 95 percent and close when it drops below 90 percent.

The ground wire on my isolator goes through a relay triggered by the ignition and then through the relay in the BMV 712.

The batteries are only combined when the ignition is on and the SOC is below 95 percent.


Most versions of the Victron BMV 7xx have the relay function, but the 712S has a latching relay that only draws current when switching and is the one they recommend for use with Li batteries.


I agree, this is something PW should have designed for.

When I looked at the Victron monitors a couple of years ago while considering a similar control circuit setup, the thing that gave me pause was the very low current rating of the Victron internal relay contacts. I think it was only one amp at the time. Have they increased the capacity of those contacts, or do you have a very low current separator?
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Old 09-22-2018, 12:27 PM   #9
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An older technology diode type isolator might be an easy and low cost fix for some the problems being discussed here. Lose the separator or have it on a manual or ignition controlled switch.

The diode type isolator would be uni-directional and have approx 0.5V drop.

Both of my RV's (all lead acid batteries) have both diode type isolators (uni-directional, chassis to house charging) and bi-directional separators installed (12.8V+ bi-directional joining).
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Old 09-22-2018, 01:45 PM   #10
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Quote:
Originally Posted by booster View Post
When I looked at the Victron monitors a couple of years ago while considering a similar control circuit setup, the thing that gave me pause was the very low current rating of the Victron internal relay contacts. I think it was only one amp at the time. Have they increased the capacity of those contacts, or do you have a very low current separator?
The think the Victron can handle a max of 1 amp.

My description wasn't as clear as it could have been, but the Victron relay and the ignition signal are triggering a small automotive type relay which is actually switching the control lead of a Yandina 600 amp isolator.

I don't think the draw on the automotive relay coil or the isolator remote is more than a few hundred milliamps.
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