Please consider registering
guest

sp_LogInOut Log In sp_Registration Register

Register | Lost password?
Advanced Search

— Forum Scope —




— Match —





— Forum Options —





Minimum search word length is 3 characters - maximum search word length is 84 characters

sp_Feed Topic RSS sp_TopicIcon
Two Problems, I think, Battery life and cooling or lack of
September 14, 2009
7:50 am
Avatar
Steve Pooler
Admin
Forum Posts: 1127
Member Since:
November 12, 2008
sp_UserOfflineSmall Offline

Speakrdude said:

From the inverter, with the batteries fully charged. 13.19VDC, 1:40PM, Cabin temp 77 degrees, air temp (at the discharge vent) 66 degrees.

1:50, 11.94Vdc, all temps same.

2:02, 11.74 Vdc, all temps same.

2:12, 11.52 Vdc, all temps same.

2:24, 11.11 Vdc, all temps same.

2:36, 10.58Vdc, System shut down……..

Inverter outside temp, extremely warm.


Looking at your chart here this morning…Sorry was kinda busy Sunday eve…

Given the limited info I can only go by voltages (no amp reading) and the published amp draw spec.

You are showing a 9.48% voltage drop (1.25 volts) Immediately from standby fully charged, to the unit running…This is way to much drop and is the first indication of too small of wire….Not carrying the load effectively.

Next reading difference 12 min later is 1.68%

Next 10 min is……………………………….1.87%

Next 10 min………………………………….3.56%

Next 12 min………………………………….4.77%

This all points to a wire or connection problem…But also points to high amperage draw over what the specs indicate…I would guess that at startup the voltage at the batteries is much higher than the 11.94 volts you are seeing at the inverter…..And that it would not be 11.94 at the inverter if you had larger wire…It would be much closer to what the batteries reading is at that time….

Do the wires get hot ?

If you do end up staying with this setup…My thought is to increase wire size to #2 cable (both neg & pos) and up battery capacity from 140 to 450 AH. 

#2 wire will have Half the resistance as the #4 being used…Thus supply the inverter a much higher start voltage under the same load…

It's going to take that 3500 btu unit a long time to cool that cabin to a temp that satisfies the t-stat and cycles the unit off…And in a 100 degree day as you mention…The heat leaking into that cabin for sure may be more than the 3500 btu the unit is capable taking out…Thus no cabin temp drop….Maybe even an increase in temp when the cabin is closed up.

It may be well into the night before it cycles, or even begins to cool off…

Not having seen the cabin or boat…I can only guess at all this as well, but my experience and what you are saying is telling me it's all so…

Let me know how things go with the distributor…If you need advise on a unit, I'd love to help, but will need more info…Maybe some pictures of space/s ?

Steve~

September 13, 2009
8:07 pm
Avatar
Steve Pooler
Admin
Forum Posts: 1127
Member Since:
November 12, 2008
sp_UserOfflineSmall Offline

I would say they may not be happy and charge a restocking fee...Especially if you told them what you wanted...

Did they offer any assistance in what you might need for the application ?

Steve~

September 13, 2009
6:38 pm
Speakrdude
Guest
Guests

I will have to check with the distributor (AER) and see if they would up trade me.

September 13, 2009
6:32 pm
Avatar
Steve Pooler
Admin
Forum Posts: 1127
Member Since:
November 12, 2008
sp_UserOfflineSmall Offline

Speakrdude said:

yes, The system was running. The beginning voltage was 13.19vdc. I only took readings at the battery post at the inverter. These are 2 Master Volt AGM type 70ah batteries wired in paralell. (spelling?)


I remember what batteries you are using…and I know what the literature says about run time…

The key is the amp draw and what you have available like I explained in my first reply…

Since you said shortening the run increased your run time I'm concerned about amp draw…We don't know that so we have to go with what we do know.

And I also realize you are not happy for the money you spent…Likely for good reason if you were led to believe the product would do the job you presented…

To be truthful…Unless that cabin is like a 20-22 footer's V-berth…3500 BTU is not going to be enough on it's best day….I don't remember a Bayliner 2750 cabin being that small…They are more like full headroom cabin's with a stand up head & dinette ???

Yes…We are now talking about temps but I would also like to try to find out if there is a problem with the unit, the installation, operation, or expectation…

I agree that you would be much better off with a larger unit & genny…Can you take this one back ?

It may save a lot of aggravation & expense…But I'm happy to work thu making this install as good as it can be with you if not…

Steve~

September 13, 2009
6:09 pm
Speakrdude
Guest
Guests

yes, The system was running. The beginning voltage was 13.19vdc. I only took readings at the battery post at the inverter. These are 2 Master Volt AGM type 70ah batteries wired in paralell. (spelling?)

September 13, 2009
6:06 pm
Avatar
Steve Pooler
Admin
Forum Posts: 1127
Member Since:
November 12, 2008
sp_UserOfflineSmall Offline

For now let's just talk voltage...We'll get to the temp in a bit...

11.94 vdc...Was that with the system running, and what was the voltage at the battery ?

I'd like to know how much voltage drop we have between the battery & the inverter...

Also would like to know the start voltage both at the battery, and the inverter before running...

I need to know how far your charger/charging system is charging up those batteries...

Steve~

September 13, 2009
5:49 pm
Speakrdude
Guest
Guests

The above readings are with #4 gauge battery cable shorten to 10' (20 'total round trip)

September 13, 2009
5:47 pm
Speakrdude
Guest
Guests

From the inverter, with the batteries fully charged. 13.19VDC, 1:40PM, Cabin temp 77 degrees, air temp (at the discharge vent) 66 degrees.

1:50, 11.94Vdc, all temps same.

2:02, 11.74 Vdc, all temps same.

2:12, 11.52 Vdc, all temps same.

2:24, 11.11 Vdc, all temps same.

2:36, 10.58Vdc, System shut down........

Inverter outside temp, extremely warm.

September 13, 2009
5:40 pm
Avatar
Steve Pooler
Admin
Forum Posts: 1127
Member Since:
November 12, 2008
sp_UserOfflineSmall Offline

So what are the readings, and where were they taken from ?

Steve~

September 13, 2009
5:32 pm
Speakrdude
Guest
Guests

No, But I have been looking for an excuse to buy an amp meter. I do, however, have readings from every 10 min's of DC voltage, cooing temps at the discharge and in the cabin. The cabin, to me, is small. The boat is a 1984 Bayliner Ciera Sunbridge 2750.

I can only imagine how bad it would be in the middle of the summer at 100 degrees if the unit will only cool 10 degrees. For the price of these little things, I would have been better off to buy a larger unit and a Honda Genny.

September 13, 2009
11:22 am
Avatar
Steve Pooler
Admin
Forum Posts: 1127
Member Since:
November 12, 2008
sp_UserOfflineSmall Offline

Also...Do you have a way to measure the DC amperage draw while running ?

Steve~

September 12, 2009
7:18 pm
Avatar
Steve Pooler
Admin
Forum Posts: 1127
Member Since:
November 12, 2008
sp_UserOfflineSmall Offline

Hi Jim~

I think I need to start out by honestly admitting that you now have more experience with that unit than I do   Surprised

I have only seen one on a bench (cute little thing) but have never heard or seen one run…much less hooked one up…

I'm not even sure my distributor stocks them…They won't stock anything that they don't sell 2 a year of…

I will offer that if it were me checking it out…I would first check voltage when running…Both at the inverter module & at the batteries…This can answer a lot of questions about the wire & run…

Low voltage equals High amperage, and thus less run time…

I wanted to get back to you as soon as I read your post, but again I'm at a loss for info of amp draws etc. to answer your other questions…

I can look into all that, and even call the factory for a refresher if you like, but that call can't be made on the weekend…

In the mean time….

How big is the cabin ?

What is AH rating of those batteries…70 AH each ?…That's 140 AH (at best)

The way I see it:

At 30 amps draw (I checked the specs) I would only expect 2.6 hours of run to 50% battery discharge with those batteries…

A voltage drop (in the wire) will decrease this time because the unit will draw more amperage at the lower voltage.

To get a full 8 hours sleep at 30 amp draw you would use 240 Amp Hours…

Meaning that to keep from running batteries below 50% charge (usual battery manufacturers recommendation) you would need a battery capacity of 480 Amp Hours….This is if the A/C ran full time and did not cycle on the thermostat.

(4 Golf Cart Batteries would total somewhere around 450 AH when compaired to needing 6-7 of the ones you have)

That unit is only 3500 BTU (smaller than the smallest window shaker)…If the cabin is any more than a little cuddy cabin…It may never cycle until late into the night if at all…

Pulling the cabin down to temp is going to take the most out of the batteries…How much is left after that is relative to how much was taken out of the batteries during cabin pull down…30a X the hours it took to cycle.

This may be why I never thought much of selling the unit, but it might be OK if you had a large enough battery charger, and first cooled the cabin on shore power or with the engines running to the point that it would cycle the unit…Then maintaining the cabin temp would then take much less…

Steve~

September 12, 2009
6:23 pm
Speakrdude
Guest
Guests

I recently purchased a new cruisair Cuddy DC System for one of my project boats. The Distributor told me to use 2 Mastervolt 70ah AGM batteries and they should last 4~6 hours on a charge. I installed the system (with 4 gauge, 25' away in the engine compartment) and the system will only run for 36 minutes before the batteries are exhausted. As an experiment today, I relocated the batteries to within 10' (20' total) of the unt and tested. Increased he time approx 50 minutes.

In another instance, The air temp from the blower has a max cool of 66 degrees. The temp at the intake is only 76 degrees. Not a very big difference. I can imagine how it will be when it's 99 degrees outside.

Where shall we begin?  

Jim