We have a very small inverter -- we turn it on when we need a/c power, such as for charging a phone. When I am running the furnace and the pump and the inverter with a charger, the voltage readout on the inverter sometimes drops to 11 volts momentarily, triggering a brief but loud alarm. And a really big load, like trying to charge a laptop, will cause the inverter to turn off altogether.I know the battery is fully charged -- this is a group 31 with 110 amp-hours, at 12.7 volts in a resting state.So that is my question -- if I get a bigger inverter, will it still drop to 11 volts and emit that shriek? Would a bigger inverter charge the laptop?Sorry if this is a naive question, but we have resisted getting a more expensive inverter since we so rarely use it. Thanks in advance for your advice.

I'd guess if your bigger inverter has an alarm setpoint of say, 10.5 V it will be better but if it has the same 11V setpoint, it will function the same. The draw from the battery is what's bringing your voltages down, not the function of the inverter. I'd assume from your statement about the laptop charger causing an alarm that you have a small MSW inverter. By all means, upgrade to a bigger PSW inverter. I recommend the Xantrex Prowatt 1000W inverter. It is silent, durable, and comparatively inexpensive.

You need larger 12 volt wire to the inverter to reduce the voltage drop.

You might just need fatter wires between the inverter and battery. If you plug the inverter into a 12v socket then that leads to long thin wires which is the problem. If it also comes with a set of wires for battery clamps then use those instead of the 12v plug set directly on the battery. Or if you need to do this inside the rig, you can clamp to the battery lugs on the DC panel which also has the converter's wires to it. The wires from the lugs to the battery will be fatter than from the 12v socket (on the Winegard panel, eg) and might make the difference.Getting a bigger inverter won't help with this.

As Westend said, it depends on the set-point for the alarm.And different manufactures use different set-points.If the wires to the inverter (input) are too small, there will be a voltage drop. Usually this is more of an issue with larger inverters that need hose size wires, but it still might be something worth looking at...especially if you are connected to the trailer wiring rather than using a dedicated wire to the battery.When batteries get older (and colder), they have less capacity. Maybe it's time to replace your battery.Winter camping takes lots of battery power. Any chance you can add a second battery?I know we have discussed it before, but a heater that doesn't use a battery sucking fan makes a huge difference. Are you still planning on going to the Canyons later on this month?

I agree with two of the posts above, that #10 wire between the inverter and the battery will work well, and there will be much less voltage drop to the inverter.You seem to rarely need the inverter, so a larger one seems not required. Either way, you probably would need #8 wire for the larger inverter, and the small one will barely have any voltage drop across the really large wire.Also make sure that the return wire is also copper wire to the battery, so that you are not using the steel frame to conduct power back to the battery.Check the battery for loose connections. A loose connection such as the battery ground can cause momentary voltage loss that you described.. . By the way, a larger inverter would also require dual batteries. Dual batteries, and your voltage drop would be much less, so not requiring the replacement inverter. Also a solar panel can allow the battery to be fully charged and be in much better condition before a trip starts. SunElec.com has a 140 watt solar panel for about $229 that has a aluminum frame. It will work great on any RV!GOod luck,Have fun camping!Fred.

Will a bigger inverter avoid the dreaded alarm?

50 Replies

pianotuna
Nomad III
Dec 10, 2015
Hi Almot,

I only found it about two weeks ago. So sorry!

It is a gravity furnace with a combustion chamber and heat exchanger. I'd guess that it is blue flame--but not in the sense of a buddy heater. The best part, other than having a chimney, is having a thermostat.
Almot
Explorer III
Dec 10, 2015
Dammit, Pianotuna - you could've posted this BEFORE I have installed my Wave 6 catalytic heater :)

Ah, what the heck - I see on-grid camps in my future anyway.

It's not cheaper than Wave though. Wave 6 is $270, Wave 8 - $320, this one is $380 @8 BTU. Same size as Wave 6/8, though much heavier. Trailer wall is 1/4" plywood, wouldn't hold much lighter Wave 6, I had to screw a 0.5" plywood sheet onto the wall behind the heater.

I don't understand what type it is - a blue flame or brick, or what?
pianotuna
Nomad III
Dec 10, 2015
Just what a boondocker without consuming 12 volt power who wishes to heat with propane needs. It even has a thermostat. It is available at Amazon for a lower price--but the write up at Home Depot is better. I believe it is lower cost than the unvented (and hence UNSAFE) wave catalytic units.

http://www.homedepot.com/p/Ashley-Hearth-Products-8-000-BTU-LP-Gas-Direct-Vent-Heater-AGDV8L/206165166

Use and care manual:

http://www.homedepot.com/catalog/pdfImages/59/596984a9-53a6-41f3-a93d-85c9bf4945c9.pdf

NinerBikes wrote:
I see a couple of options.

Change usage pattern. Have you considered turning off the HVAC unit with fan, and replacing it with a Olympic Wave 3 Catalytic convertor, runs off of straight propane, no electrical fan running? It is an option.
NinerBikes
Explorer
Dec 10, 2015
I see a couple of options.

Change usage pattern.

Or find a way to eliminate one of the larger electrical power sucking devices when all are running. Have you considered turning off the HVAC unit with fan, and replacing it with a Olympic Wave 3 Catalytic convertor, runs off of straight propane, no electrical fan running? It is an option. You do need to crack a window and a vent when an Oly Cat heater is running, for fresh air /to keep CO at low safe levels.

I figured you were the perfect buyer for my 120W folding solar panel setup... how has it been working for you, with your conservative camping? Winter time and low sun angle makes portable great for catching the most of the sun that you can, sun chasing with the portable panel.
2oldman
Explorer II
Dec 10, 2015
Byrogie wrote:
You: Can I play the violin after my arm heals?
Doc: Certainly
You: Great, because I couldn't before...
Yes! I think I heard both of those on Hee Haw.. decades ago.
Byrogie
Explorer
Dec 09, 2015
2oldman wrote:
mkirsch wrote:
You: "Doc, it hurts when I do this."Doctor: "Well, don't do that!"
Hah! One of my favorite gags.

Opposite:
You: Can I play the violin after my arm heals?
Doc: Certainly
You: Great, because I couldn't before...
Salvo
Explorer
Dec 09, 2015
It's more likely the cables are the problem.

When the water pump is activated, the voltage drops at the inverter because of resistance. We got battery resistance and cable resistance. A good battery may have 12 mohm resistance. Cables can be 25 mohm or worse. In this case, the cable will drop twice as much voltage as the battery.

If you got 2 12V batteries each having 12 mohm, then the combined resistance is 6 mohm. That's a good reason to use 2 batteries. But it won't help much if the cable is too small.

mkirsch wrote:
The interior lights visibly dim when the pump goes into its fast on-off cycle mode so it is definitely drawing down the voltage.

The only cure for that is additional battery capacity. I chose to work around it because it's only a temporary condition that persists for a whopping 5 minutes a day.
mkirsch
Nomad II
Dec 09, 2015
Almot wrote:
mkirsch wrote:
If a certain pattern of usage is causing the alarm, change that pattern of usage.

OP states that it only happens when the furnace AND the water pump AND the inverter are running simultaneously.

Yes, change of pattern of usage is one of available options. Wiring everything right, however, is a must - not an option. His inverter was not wired right.

If he was trying to run a microwave with the inverter, I'd buy that. However he was just charging a cell phone. Negligible load.

The inverter is not what's drawing the batteries down to 11V. It's not even the straw that broke the camel's back.

Most of it is the water pump cycling on and off rapidly during the shower. Believe me, I have a similar problem in my rig:

When someone is using the shower in my camper, the propane alarm starts chirping due to low voltage. The interior lights visibly dim when the pump goes into its fast on-off cycle mode so it is definitely drawing down the voltage.

The only cure for that is additional battery capacity. I chose to work around it because it's only a temporary condition that persists for a whopping 5 minutes a day.
2oldman
Explorer II
Dec 08, 2015
mkirsch wrote:
You: "Doc, it hurts when I do this."Doctor: "Well, don't do that!"
Hah! One of my favorite gags.
Almot
Explorer III
Dec 08, 2015
mkirsch wrote:
If a certain pattern of usage is causing the alarm, change that pattern of usage.

OP states that it only happens when the furnace AND the water pump AND the inverter are running simultaneously.

Yes, change of pattern of usage is one of available options. Wiring everything right, however, is a must - not an option. His inverter was not wired right.