Could this be a battery isolator problem, or???

[nicaland]

I recently replaced my stock Magnatek 6332 converter/charger in my 1998 Xplorer 230 XLW with Progressive Dynamic's PD 4635 unit. The conversion was painless and has proven to be a major and needed upgrade; not only do my house batteries charge much more quickly, and the converted 12VDC is now super clean, enabling problem free DC power to all devices including my TV, but I suspect that the life of my batteries will be greatly extended as a result as well.
However, when removing all power sources to the RV in order to install the new converter after unplugging from 120VAC, I then disconnected my house battery and (wisely) double checked for DC voltage before proceeding with the exchange, and found that I still had 11.8 volts showing on the DC side. The start/engine battery was still connected at this point, and thinking that as this RV is equipped with a battery isolator I had not disconnected it. I then checked the voltage of this battery before disconnecting it, and at the battery terminals it showed 12.8 volts, but after disconnection the house voltage dropped to zero and I proceeded with the converter swap. (one volt difference between the terminals of the battery and the house circuit voltage before disconnect).
Before I made this converter swap, the original house charger only charged the house batteries and not the start/engine battery and that is still the case with the new unit. So as before I planned to reinstalled a small (1 amp) smart trickle charger on the start/engine battery, but only after checking that the PD charger was operating correctly by going through bulk (14.4V) and acceptance (13.6V) cycles before hitting a final float stage (13.2V) after approximately 34 hours, and it did so. After confirming that it was indeed operating correctly in this regard, I hooked up the trickle charger to the start/engine battery, and after around three hours I was registering 13.5-13.6V on the house battery circuit, and 12.9 on the start/engine battery (up from 12.6 before charging it). When I disconnected it, the house battery circuit after a couple of hours returned to 13.2V.
So, although the PD 4635 is not charging the start/engine battery, the voltage from it is definitely affecting the house battery circuit and in fact the reverse is true! I'm thinking that the isolator is malfunctioning; however, this RV also has an emergency start feature that with a dash button press a solenoid is activated that connects the house batteries to the start battery if it has been inadvertently discharged (headlights left on, etc.) and I had recently used that feature, so I suppose that could be playing a part in this issue as well.
Any ideas, anyone?

[markopolo]

Sounds like you're on the right track and have a good understanding of what is happening.


These two pdf's have isolator troubleshooting steps and should be helpful:


Battery_Isolator_Trouble.pdf


isolator sp1.pdf

[nicaland]

Thanks Marcopolo! This indeed is very useful information. Based on my initial read of these two documents my first guess is that diode 1 has shorted. I forgot to mention that the alternator is successfully charging the house bank, but I have yet to check the relative voltages of each bank while charging with it. I'm going to disconnect shore power, discharge both banks a bit, and test relative voltages per these instructions at the isolator. I'll report my findings after doing so. BTW, my Xplorer manual, which actually is a wonderfully complete, detailed, and well organized one, states that the converter/charger when in use charges only the house bank. Why is this the case, and is there a way to get around this condition and have it charge the engine battery also? As I had mentioned before, I do hook up a trickle charger for the start/engine battery during storage, but it sure would be nice to have my new charger sned the same charging protocol to it as well.

[markopolo]

A battery isolator is unidirectional. Charge current flows in one direction. A battery separator can be bidirectional.

Some battery separators use more current than others so some research before purchase is beneficial.

This Automatic charge relay -> https://www.bluesea.com/products/761...12_24V_DC_120A - looks to have good specs.

Q: How does an ACR differ from a battery isolator?
A: Battery isolators use one-way electrical check valves called diodes that allow current to flow to, but not from, the battery. ACRs use a relay combined with a circuit that senses when a charging source is being applied to either battery. ACRs are more efficient than battery isolators because they create little heat and consume minimal charging energy.

[nicaland]

Well it certainly looks like a battery separator, or an Automatic Charge Relay, as Blue Sky is calling this one, would be a better solution than an isolator in all respects, unless there are major efficiency differences involved. Are these typically found in more recently designed/built two battery bank applications in lieu of using an isolator?

Another aspect that I'm having a hard time fully comprehending involves the fact that I'm dealing with two charging sources, shore/generator and engine alternator. If I were to replace my isolator with a separator, would both charging sources charge both banks, and would there be a conflict or overcharging condition if both are charging at the same time? I apologize for the newbie questions; this is one of those things where a little bit of knowledge can be a dangerous amount to rely on!

[markopolo]

The Automatic Charge Relay would be better than an isolator in my opinion.

1. Bidirectional charging - when on shore power or generator both the house and chassis batteries get charged. Both batteries also get charged by the alternator.

2. No voltage drop - typically isolator output to the house battery drops by 0.5V. If you have 14V off the alternator that means only 13.5V at the house battery.

One downside would be if you chose a separator with wasteful current draw and you have solar panels on the van. You don't want to waste 1.5A of solar output on the separator. The solution there is to chose something like the Automatic Charge Relay. The current used is 175mA (combined) 15mA (open). 175mA = 0.175A, huge difference compared to 1.5A for example.

[avanti]

Originally Posted by markopolo

The Automatic Charge Relay would be better than an isolator in my opinion.

1. Bidirectional charging - when on shore power or generator both the house and chassis batteries get charged. Both batteries also get charged by the alternator.

2. No voltage drop - typically isolator output to the house battery drops by 0.5V. If you have 14V off the alternator that means only 13.5V at the house battery.

One downside would be if you chose a separator with wasteful current draw and you have solar panels on the van. You don't want to waste 1.5A of solar output on the separator. The solution there is to chose something like the Automatic Charge Relay. The current used is 175mA (combined) 15mA (open). 175mA = 0.175A, huge difference compared to 1.5A for example.

Well, the other choice is simply a "dumb" separator that only closes when the engine is running, combined with a Trik-L-Start to permit the solar to keep the chassis battery charged.

[markopolo]

That's an option for sure. The Trik-L-Start does introduce a 0.2V voltage drop and limits current to 5A. Plus you have the cost of buying two devices. The Blue Sea 7610 appears to be around $78 on Amazon https://www.amazon.com/gp/product/B000OTIPDQ/

[nicaland]

Definitely sounds like an ARC is a win-win for me then, especially since I'm not using any solar panels. The Blue Sea (not Blue Sky) ARC is only $50 or so more than a new Surepower 1602 isolator replacement cost as well. I have used other Blue Sea products in the past on boats and find their stuff very well made and engineered. I don't know if I will run into any wiring difficulties but haven't researched it yet, and suspect that should be readily available info and not to complicated. As I had mentioned before I do have a start assist system on this RV that via a manually operated relay couples the house bank with the engine start battery, which sounds like will be redundant after installing an ARC in lieu of an isolator, and I figure it would be prudent to disconnect this system after installing the ARC.

[nicaland]

Thanks marcopolo for the Amazon link to the ARC. That makes it almost exactly the same price as the replacement isolator!

[nicaland]

There I go again........ACR, not ARC..........

[nicaland]

I ended up buying the Blue Sea Si-Acr model 7610 that you recommended markopolo, after doing a bit more research on this product. Thank you very much for making me aware of this alternative to buying a replacement isolator! I was a bit concerned as to how to install it with my existing various circuit breakers and the emergency start solenoid, so I emailed Blue Sea's service department and incredibly received qualified answers to all of my questions within five minutes! I honestly am amazed at the speed and quality response that I got back from them, and it turned out to be a ridiculously simple install procedure after all, in addition to offering superior operational characteristics, at the same price as an isolator replacement. I will follow up after I get it in place and test it, but am confident that it's the way to go for anyone that is currently using an old fashioned isolator. Less current draw, and it will allow both the house battery bank and the start battery to be charged bu either the alternator or the AC charger.

[peteco]

At booster's recommendation I replaced the isolator with the same BS 7610 and have been very happy with the results. You do need to keep an eye on your battery water when driving a long distance due to the higher charging voltage compared to the isolator. I have to top up the house battery water more frequently. I think booster installed a switch to disable the ACR on long trips.

[avanti]

BlueSea tech support is first rate for sure. I have asked them some detailed technical questions that would make the average vendor's eyes glaze over. They returned with fast and reliable data, including actual numbers. Excellent company.

[Nic7320]

Consider the fact that no diode is perfect. All diodes exhibit some leakage, and that what you may have been measuring with a voltmeter.

The problem is two-fold; digital voltmeters (DVMs) don't require very much current to take a reading, and consequently, they don't provide any significant loading to the circuit being measured (by design). So any leakage across a diode based battery isolator will show up as a voltage on the isolated circuit, but at very little current.

So if you load the circuit, say, by turning on a single light bulb, any leakage current from the isolator should be dragged down by the load, and the voltage reading will go to zero volts. Otherwise -- if it doesn't -- the diode is indeed bad and has unacceptable leakage.

If your isolator is bad, I would recommend a 'smart isolator' that uses a relay, rather than diodes. They have an electronic controller to allow the starting battery to charge first before connecting the house battery. Then the relay closes and your house battery gets as much current as it needs to rise to the same voltage.

[nicaland]

That's interesting, makes sense, and thank you for the reply. However, I ended up replacing my isolator with Blue Sea's SI-ACR charging relay, and have to say that it is in my opinion a massively better alternative to using an isolator. Not only does it eliminate the .5V-.7V drop across the old isolator to the house bank from the alternator, but it also allows the start battery to be charged by my converter/charger that is connected to the house bank. Additionally it was ridiculously easy to hook up, and the cost via Amazon was virtually the same price as a replacement isolator! Prior to it's installation I had replaced the guts of my old Magnatek 6332 converter/charger with Progressive Dynamic's PD 4635, also a direct bolt(screw?)-in replacement which required making quite a few more connections, but was also a simple job. Not only does it charge both batteries much, much more quickly and allows the RV to be hooked up continually to shorepower without worries of cooking them as well, but additionally it puts out a significantly cleaner DC out of the converter section that most all DC powered equipment (TV's. chargers, even voltmeters!) can recognize and safely run on. I can't recommend strongly enough to those of you out there to modernize your (probably older) RV with both of these updates if you haven't already. It's a major and inexpensive win-win in my book for sure!

[booster]

Sounds like it all worked out well for you.


On thing to be aware of is that now you don't have the nearly one volt of drop in your alternator to coach connection, so you do have the chance of overcharging your batteries on long drives, especially if you start out with them full coming off shore power.


I think the Blue Sea ACR you got has what the call "start isolation" which is a terminal on the ACR. It is used to disconnect batteries when starting the engine if there are spikes or other things going on. I think you will find that if you put 12v on that terminal, it will open the ACR connection between the alternator and coach, so you can use it for protecting your batteries if they get full while driving. I didn't use it that way when I had them for a different use, but did have them wired to isolate banks when the charger came on and the did that fine. You may want to consider putting a switch to that terminal so you can shut off the coach charging if you need to.

[nicaland]

Peteco had also mentioned that possibility, and as a result I asked Blue Sea's rep, a Mr. Avery Stiles, what he thought about this. His reply was that in his opinion as long as none of the batteries connected through the relay were bad that should not be an issue, especially in fact, if all of them had been charged together via said relay and started at the same voltage, which with the Progressive Dynamic PD 4635 at float stage is 13.2V.

However, with that said, I will be checking my water levels on both banks more often
both on a trip and in storage, because neither have been kept long term at this level, which what I feel is the optimal voltage for them to be stored at anyway.

Finally, Mr. Stiles also commented that if one is concerned about this, or if it does become an issue, that in order to stop the relay from sending a charge in either direction, to shut it down all that needs to be done is to install a switch (2-3 amp capacity is sufficient) in the ground wire leading from it.

[booster]

Originally Posted by nicaland

Peteco had also mentioned that possibility, and as a result I asked Blue Sea's rep, a Mr. Avery Stiles, what he thought about this. His reply was that in his opinion as long as none of the batteries connected through the relay were bad that should not be an issue, especially in fact, if all of them had been charged together via said relay and started at the same voltage, which with the Progressive Dynamic PD 4635 at float stage is 13.2V.

However, with that said, I will be checking my water levels on both banks more often
both on a trip and in storage, because neither have been kept long term at this level, which what I feel is the optimal voltage for them to be stored at anyway.

Finally, Mr. Stiles also commented that if one is concerned about this, or if it does become an issue, that in order to stop the relay from sending a charge in either direction, to shut it down all that needs to be done is to install a switch (2-3 amp capacity is sufficient) in the ground wire leading from it.

I think he is correct on the ground wire switching doing the same thing in disconnecting the unit. They don't use that for start interrupt because it would take a relay to be automatic, but great for manual operation.


If the batteries are on the PD charger at float, he is absolutely correct that they should be just fine. The issue is only when you are on alternator charging while driving, where the voltage on many vehicles will stay at around 14.1 to 14.5v all day. If the batteries are full from shore charging overnight that could be many hour of overcharging.

[peteco]

Originally Posted by booster

The issue is only when you are on alternator charging while driving, where the voltage on many vehicles will stay at around 14.1 to 14.5v all day. If the batteries are full from shore charging overnight that could be many hour of overcharging.

Do you think the batteries will be damaged if the water level is always maintained above the plates?