Surges & Inverters?

[BobJones]

Hi folks!

Got a quick question for anyone that may be knowledgeable with inverters. On my '00 Diplomat it has a Trace Engineering inverter. It's a 1500 watt Legend series. It has the RC-9 remote panel which shows basic information on charging (bulk or float and voltage) or how much of the capacity of the inverter is being used when on and the battery charge levels.

It's worked very well over the years. Fast forward to today, and I'm in a park that has the odd power failure. As such, I leave the inverter on 24x7 and essentially use it as a UPS. In this way the odd power failure is seamless and only once did the batteries get down to the level where I had to fire up the genset.

I have noticed that since it's a modified sine wave inverter it has some limitations (such as the TV often needs to be unplugged and plugged back in (reset) when the power failure occurs and it goes on inverter). So that's one strike against it. Another is the fact that it's not going to be as 'clean' power as a more modern sine-wave inverter. That's one I could live with as the inverter (other then that) works well.

However, the other day I believe there was a brief power failure (like 3 seconds or something). The batteries were fully charged and I checked all cells with a hydrometer a few days before and they are all excellent. When this power 'glitch' occurred the RC-9 panel actually made a light chirping noise (I think it was the panel) and when I looked at it, pretty much all the lights were lit up. It was uncharacteristic behavior.

So, the power was off for seconds, the batteries were certainly fully charged and here's where it gets odd. The inverter switched back over to monitoring mode and of course then went to charge the batteries back up. The thing is, according to the panel, it went straight to bulk charging mode. This should not have occurred. The batteries were full, the power outage (if there even was one) was only a second or two long and then resumed. The characteristic behavior would have been for the inverter panel to show that it was back in float mode as only a negligible amount of power was drawn from the batteries.

At that point I went outside and physically looked at the inverter. When bulk charging the fan is on and it's noisy. The fan was not on, the batteries were not warm or gassing, and I personally don't believe they were bulk charging at all. I think it was actually float charging but the display panel was pooched.

I then shut off DC power to the inverter and then unplugged the motorhome. So what I'm trying to do is drain all power from the inverter and panel and 'hard reset' it. After a few minutes I re-connected shore power and the coach batteries and went back inside. The panel shows that it's once again bulk charging. It's not. The batteries are up and the inverter fan is not on.

This causes me to think that the remote panel got pooched during a power sag/surge scenario. This got me thinking about the real cost of the power outages in this park. As we know, when power sags or fails it usually surges when it comes back. This makes me think that the remote panel was affected by a surge, or perhaps the section of the inverter that drives the panel...

Either way, it should not bulk charge for 45 minutes before going back to float charging when the batteries are full. The fact that the inverter fan is not on makes me think the panel is lying and was damaged (when considering the odd lights during the event).

Anyway, long story short. I've been thinking about inverter damage by power surges. Given this inverter is older (or old) and a new Xantrex is effectively double the output, and true sine wave, and more modern...I was thinking along the lines of replacing it and going all in with a new Xantrex, panel and remote genset start. Dimensionally it looks like the large Xantrex is able to fit in more/less a plug 'n play scenario and they make adapters for the existing remote panel line. In short, other then remote genset start, it should be an easy install.

My question would be this. Do you think I'm correct that a surge could have damaged the panel or the inverter? If so, would this old inverter be more or less prone to surge damage? I was thinking along these lines, if I dropped what would probably amount to $2 or $2.5k on a new inverter system, would the park's power surges (if they are present) also take a toll on a brand new inverter system or would they be more able to handle transient power spikes because they are much newer?

Any thoughts would be appreciated. Sorry about the long-winded post - it was an odd occurence and I wanted to explain where I'm coming from and what my thoughts and concerns were. I like the idea of modernizing the inverter system but if my theory about park power resumptions possibly damaging a brand new system then I'd have to re-think it altogether.

One other thing. One night, when there were no apparent power issues, I was in bed and heard a noise from the lower right. I went outside and looked in the inverter bay and low and behold the fan was running! The ambient temperature was around the freezing level and the power had not failed. This was odd behavior, never happened before (as far as I know) and it ran for a few hours before shutting down. The batteries would have been full - so - no reason to think of that the fan should come on at all.

With respect to power issues in the park, there have been 3 minor outages in 2 months. It's a new section of the park and my impression is that they have just been ironing out minor issues as the power feed to the power shed comes right off the pole and since the section is new, all boxes, cablevision, wiring etc is all new. In theory, if anywhere should have clean strong power, it should be this section of the park.

[BFlinn181]

Have you taken any voltage readings when the inverter says it's bulk charging but the batteries are fully charged? Perhaps it goes to bulk charge on a restart and will eventually drop to a float charge level. A short time at a bulk charge rate shouldn't boil the batteries, it would take a good period at that rate before damage would be done. Does the inverter/charger have a temperature probe on the batteries?

I understand your desire for a better inverter/charger, but I'm not convinced your old one is dead.

Must be some campsite to put up with such risky shore power. I have a PI EMS but I still wouldn't risk all my electronics with so many issues.

[twinboat]

Float voltage is around 13.4 volts. When the charging stops and the batteries are discharging, even a little, they quickly fall to 12.6 volts. That's the normal resting volts of most lead acid batteries.

Now the charger comes back on. It doesn't know how low the batteries are, It's not that smart, it only reads battery voltage.

The first thing it does is go into bulk mode. It will stay in bulk mode until the voltage climbs back up to 14.8 from 12.6. That may take a while, but its not delivering many amps, due to the internal resistance of the nearly full batteries.

From there, it changes to absorbsion mode, where it stops the voltage from climbing and holds the voltage as the amps drop off further.

Only then will it drop to float mode again, letting the voltage drop to 13.4 volts.

There may not be anything wrong.

Here is a link explaining it, with some graphs.

http://all-about-lead-acid-batteries...tery-charging/

[BobJones]

Originally Posted by BFlinn181

Have you taken any voltage readings when the inverter says it's bulk charging but the batteries are fully charged? Perhaps it goes to bulk charge on a restart and will eventually drop to a float charge level. A short time at a bulk charge rate shouldn't boil the batteries, it would take a good period at that rate before damage would be done. Does the inverter/charger have a temperature probe on the batteries?

I haven't actually read the voltage on the batteries after power-cycling the invertor when the batteries were already fully charged and it shows the bulk charge indicator. I will see if I can get that done tomorrow. It does show bulk charging on the panel for about 45 minutes before it goes back to float. This behavior (now) seems to be consistent. Thanks for picking up on my concern about boiling the batteries - this was foremost in my mind even though I never mentioned it in the thread (and should have). The system does have a remote temperature probe which we duck taped to the side of a battery in a logical place. I have tried with the remote sensor active and unplugged - it doesn't seem to make much difference either way.

Originally Posted by BFlinn181

I understand your desire for a better inverter/charger, but I'm not convinced your old one is dead.

Exactly. I'm actually very impressed with this inverter (even though it's a tad small and not true sine wave). I read the owners manual and it's really, really good. In fact, it's pretty clear (to me) that the guy that designed the inverter wrote the manual. Ever since, I've been sold on it and we've tried to keep good care of it over the years.

Originally Posted by BFlinn181

Must be some campsite to put up with such risky shore power. I have a PI EMS but I still wouldn't risk all my electronics with so many issues.

I was thinking about it and I'm probably a bit harsh on my views on the power at this site. I'm up in Canada and the ambient right now is -7 and we had snow. Typically at this time of year (winter) it's not uncommon to loose power on a large portion of the grid for various reasons and at least one of the 3 failures I experienced was caused by this, and probably one more to boot. So that would actually make for one actual park failure. The thing is, this park was chosen (in part) by entirely new infrastructure. So the wiring is new, the panels are new, the main power shed is new and the power comes into this section of the park directly off the pole from the electric co. So it should be as good as it gets. I don't have any EMS/power protection (assuming you mean something like a line-active UPS or surge supressor etc).

[BFlinn181]

A Progressive Industries Electrical Management System. (EMS) only connects if the power from the pedestal is within certain parameters. It won't connect if the power is wired wrong, missing a ground, etc. It also has a built-in surge protector and in a loss of power will delay reconnecting too soon after the power loss, which could be critical for air conditioners and other electrical equipment that could be harmed by a brief power interruption. I wouldn't plug in without it.

[SCVJeff]

Twin Boat's post pretty much covers it..
One comment on the midnight cycling tho.. batteries lose charge (voltage) when they get rally cold. It's possibly your charger saw thetnand simply compensated.. as was already posted, a bulk for a few minutes while the charger figures what's up will hurt nothing. It would take a very long time to heat up the batteries to start boiling.

[BobJones]

Originally Posted by twinboat

Float voltage is around 13.4 volts. When the charging stops and the batteries are discharging, even a little, they quickly fall to 12.6 volts. That's the normal resting volts of most lead acid batteries.

Now the charger comes back on. It doesn't know how low the batteries are, It's not that smart, it only reads battery voltage.

The first thing it does is go into bulk mode. It will stay in bulk mode until the voltage climbs back up to 14.8 from 12.6. That may take a while, but its not delivering many amps, due to the internal resistance of the nearly full batteries.

From there, it changes to absorbsion mode, where it stops the voltage from climbing and holds the voltage as the amps drop off further.

Only then will it drop to float mode again, letting the voltage drop to 13.4 volts.

There may not be anything wrong.

Here is a link explaining it, with some graphs.

How Three Stage Battery Charging Works | All About Lead Acid Batteries

^This Many thanks and it makes sense. It may be a case of something went glitchy with the panel (the lights were really odd and acting crazy during the 'event') and since then I've been too worried about it and looking for things that don't yet exist.

Bottom line though, it goes bulk for about 45 minutes when there has been no effective draw from the fully charged batteries. So if that's not an issue (with respect to boiling) "but its not delivering many amps, due to the internal resistance of the nearly full batteries." then it must not be an issue. Thanks folks, I'm going to look into the EMS unit mentioned above but one last quick Q, do you think power surges are an issue worth being concerned about when it comes to inverters? I was hoping that when the power returned, if it surged, the inverter would just dump it straight into the batteries where it can be absorbed but perhaps that's wishful thinking given the surge would be AC and the batts are DC

[BFlinn181]

Inverters don't "just dump it straight into the batteries," the electronics in the inverter are at risk, likewise a TV, microwave, refrigerator, A/C, phone chargers, and any other 120v items could be at risk in a surge.

twinboat explained it much more thoroughly than I was hinting at. Since your thermostatically controlled cooling fan in the inverter/charger didn't come on, while the display might have said 'bulk' I don't think your batteries were being overcharged. Monitor the electrolyte levels in the batteries, I don't think you'll find a great loss of water from these episodes.