Inverter / Charger weirdness

Seangie · July 11, 2015, 07:42:26 PM

Hey All,

Here is the setup -
I've got a Sterling ProCombiS 2500w inverter.
I've got a 50amp panel with 2 legs
Main AC and the ProCombi inverter/charger are on the same leg in the panel
I'm currently plugged into a 20 amp circuit using a cheater cord to get power to both sides of my panel (our bedroom outlets charge our phones and that is the only circuit we are using on the 2nd leg)

The issue is that even though my batteries are fully charged, each time the AC kicks on the battery charger ramps up and starts charging the batteries again as if it just got plugged in.

I'm assuming it has something to do with either a bad battery in the bank (currently 4 6v AGM GC batteries) or a ground issue.

Just wondering if anyone has experienced this before.

Thanks!

-Sean

eagle19952 · July 11, 2015, 08:57:20 PM

don't know. but it sounds like your legs are out of balance.specially because you have a "robbed leg"...if I read your post correctly...

my AC is on one leg and inverter on the other.
my inverter is "always in service" in that it feeds all of my low watt services, thru a separate sub panel.
my coach is all electric.
my hot water heater, and my stove top are not run from my inverter.
my refrigerator, and microwave are.
Ac is 220v so it "splits" the incoming 50 amp shore and the inverter "balances" if that makes sense....

clear as mud ?

bevans6 · July 12, 2015, 03:34:46 AM

The simplest explanation is that when your AC starts, the voltage drops low enough while it's motor is starting that the inverter detects a loss of input power and thinks it's been momentarily turned off, so it goes into it's startup mode. I doubt there is anything wrong with the battery bank. I also don't think there is any issue with feeding both sides of the panel from the single AC feed, that won't affect anything. How far are you from the 20 amp outlet, and how far is it from it's main panel? What gauge and length of cord are you plugged in with? Too long a run of 12 gauge will exacerbate a voltage drop issue when the AC motor starts. People tend to ignore the in-building wiring when they are thinking about what might be causing an issue.

Brian

digesterman · July 12, 2015, 05:47:53 AM

It's not trying to charge itself off of the battery bank is it? When wired wrong that can occur.

Seangie · July 12, 2015, 09:38:55 AM

Brian,

I think that's the issue. Its a pretty a pretty long run to the house panel. We are 25 feet to a lamp post where we are plugged in and then probably another 100' to the house and who knows how much wire there is in the house to get to the panel. At least 75'. We have a 25' 10 gauge extension cord but that doesn't matter if all the rest is 12-2 (or even 14awg) going back through to the house.

Don - As far as being "unbalanced" that's just what we have to be. It doesn't have any short term affect on the panel other than one side possibly being "overloaded" but there is a 50amp breaker on the panel that should pop if we pull more than 50 amps on the one leg. Primary reason we are setup like this is that the only 110v item we NEED to be plugged in is the battery charger on leg 1 of the panel. Nice to haves are hot water and AC. All three of those are on Leg 1 so that if we only have a 15/20 amp or 30 amp plug (which is often the case) we can at least run AC, charge batteries and have hot water (we need to pick and choose if we have less than 20 amps). Fridge, fans, all lighting, jacks, water pump, inverter outlets are all 12v (battery). Leg 2 carries the other AC unit, house Edison plugs, washer/dryer, outlet for block heater and outside bay outlet.

Its wired correctly. Been running full time for 2 years no problems. Just noticed this happening and thought I'd ask to be sure. First time I've seen this happen (and the longest run of wire we've ever been on).

Thanks guys.

-Sean

eagle19952 · July 12, 2015, 12:14:36 PM

remember also that the voltage drop on 40-70 feet of 8 ga. is roughly 4%...so... on 12 ga it is likely 6%+... hence contributing further to imbalance. note 3% is "acceptable"
Others may find these useful too.

http://www.southwire.com/support/voltage-drop-calculator.htm

http://www.supercircuits.com/resources/tools/voltage-drop-calculator

I digress, into the mud

digesterman · July 12, 2015, 08:09:39 PM

So I take it that you have been using your "cheater cord" on and off for the past two years without this problem?

bevans6 · July 13, 2015, 05:20:29 AM

All a "cheater plug" does is bridge the one 120vac feed to both buses in the breaker panel. The only thing wrong with that is that any 240vac devices won't work. There is no other issue, and balancing the buses in the breaker panel is not required. The only time balancing is required is when you have a 240vac, two leg feed and you want to keep the neutral current low. Now, is it code compliant? I have absolutely no idea. I do it with my home generator setup. I have my Yamaha 3000 watt generator connected to the generator plug on the house wall with a cord that connects the single 120vac power output to both buses of my generator transfer switch panel. The plug also bonds neutral to ground at the generator, since for some unknown reason small generators don't bond ground and neutral. I never figured that out.

Brian

eagle19952 · July 13, 2015, 05:46:25 AM

If you have 2 legs of 120v from the same source buss, you are correct.
If you have 2 120v cheats each from separate buss sources then you could run 240v loads...

back into the mud.

"The simplest explanation is that when your AC starts, the voltage drops low enough"....

a voltage drop puts a considerable load on a AC. Considerable loads cause all kinds of havoc.
Having a longer wire has a compounded effect....

Seangie · July 13, 2015, 06:38:16 AM

Quote from: eagle19952 on July 13, 2015, 05:46:25 AM
If you have 2 legs of 120v from the same source buss, you are correct.
If you have 2 120v cheats each from separate buss sources then you could run 240v loads...

Don - One thing you have to be careful of when pulling 2 legs of 120v from separate buss sources is making sure they share a ground. If you have a different ground for those two sources the difference in Voltage at each ground could cause your neutral or ground wire to heat up with the voltage naturally trying to balance itself out across the ground.

If either of those sources have GFCI circuitry the GFCI will pop when it senses the voltage on the Ground.

-Sean

eagle19952 · July 13, 2015, 08:56:24 AM

Quote from: Seangie on July 13, 2015, 06:38:16 AM
Don - One thing you have to be careful of when pulling 2 legs of 120v from separate buss sources is making sure they share a ground. If you have a different ground for those two sources the difference in Voltage at each ground could cause your neutral or ground wire to heat up with the voltage naturally trying to balance itself out across the ground.

If either of those sources have GFCI circuitry the GFCI will pop when it senses the voltage on the Ground.

-Sean

noted...