Got electrical questions? I have answers!

[ird13]

Finally I found someone who may be able to help!

I just set up my solar array. I have two 245W panels connected to a Renogy 40CC MPPT charge controller, connected to two batteries in parallel. One battery has 122AH, the second has 100AH, and this is a 12v system. With one battery in the bank, the PV system worked great. After adding the second battery, the charge controller now says the batteries are full and has shut off power. Using a volt meter, both batteries read an output of 14.6 volts, however using a float hydrometer they only read one half to three quarters full. Why is this occurring?

[jjbirdy]

Hi all,

We have been using a 12v battery to power our water pump and the the control panel for our refrigerator. We have not had time to install an electrical panel or circuit breakers so they have been directly connected to the battery below the bus. Now we have two 6 volt golf cart batteries in hopes that it will discharge slower. In looking at diagrams on wiring in series, the two batteries are wired - to + with the remaining - and + going to ground and the main electrical panel respectively.

My questions are:

Can I still connect my water pump and the control panel directly to one of the batteries? Perhaps one item to each battery?

If the two golf batteries are connected to each other, would connecting the water pump (for example) to only one battery ensure that it is receiving 12 volts?

Since we have no electrical panel, do I need to do something with the remaining positive battery post?

Please forgive my lack of knowledge about how batteries work- learning as I go.

Thanks for any input!

[cullengw]

Originally Posted by jjbirdy

Hi all,

Now we have two 6 volt golf cart batteries in hopes that it will discharge slower.

I'll need an explanation on why discharging slower would matter for fridge. Also how long can you run a fully stocked fridge for on a 6V battery. (just your average fridge.)

[leadsled01]

No you cannot wire each load to one battery, this will only be 6 volts. You must connect all 12 volt stuff to the remaining + and - terminals . Those same + and - terminals are used for charging and any 12 volt load you choose. I suggest you at least use an inline fuse for the water pump and the fridge. _

Originally Posted by jjbirdy

Hi all,

We have been using a 12v battery to power our water pump and the the control panel for our refrigerator. We have not had time to install an electrical panel or circuit breakers so they have been directly connected to the battery below the bus. Now we have two 6 volt golf cart batteries in hopes that it will discharge slower. In looking at diagrams on wiring in series, the two batteries are wired - to + with the remaining - and + going to ground and the main electrical panel respectively.

My questions are:

Can I still connect my water pump and the control panel directly to one of the batteries? Perhaps one item to each battery?

If the two golf batteries are connected to each other, would connecting the water pump (for example) to only one battery ensure that it is receiving 12 volts?

Since we have no electrical panel, do I need to do something with the remaining positive battery post?

Please forgive my lack of knowledge about how batteries work- learning as I go.

Thanks for any input!

[leadsled01]

I have never seen a 6 volt fridge. By series wiring two 6 volt batteries, you now have 12 volts and usually more amp hours of discharge time. Think of it as 2 batteries are better than one.

Originally Posted by cullengw

I'll need an explanation on why discharging slower would matter for fridge. Also how long can you run a fully stocked fridge for on a 6V battery. (just your average fridge.)

[bubb, the real one]

Originally Posted by ird13

Finally I found someone who may be able to help!

I just set up my solar array. I have two 245W panels connected to a Renogy 40CC MPPT charge controller, connected to two batteries in parallel. One battery has 122AH, the second has 100AH, and this is a 12v system. With one battery in the bank, the PV system worked great. After adding the second battery, the charge controller now says the batteries are full and has shut off power. Using a volt meter, both batteries read an output of 14.6 volts, however using a float hydrometer they only read one half to three quarters full. Why is this occurring?

IRD


ird13,
the specific gravity test should work,
I would charge the up one day, then at night disconnect the batteries and let them sit disconnected all night, then check their voltage and the specific gravity,
12.6 or 12.7 is a full battery, less means it is getting old, below 12.4 or definately 12.3 and you may want a new battery, best to have identical batteries at least for the long term it is,

check the specific gravity also on each cell and keep notes,

I realize you may have plans for more batteries but you have panel charging capacity that is oversize for your batteries, depending upon how much power you use ever day you may want to disconnect one panel so you dont overcharge the batteries with too many amps,

[NguyenBus]

Is 5000w to much for my bus? Refrigerator microwave acc and toaster oven

[bubb, the real one]

5000w inverter or solar panels?
5000w inverter is probably too big, a 2000w inverter will probably work, as long as you only microwave when the fridge is not running.

2000w of solar panels is about the most anyone could fit on a large bus, it would cover the entire roof

[charles_m]

I did the maths and could have done up t 2400watts on my 27 foot roof. Didnt need it, but i was curious.

I see a lot of questions here that would be answered by just improving an understanding of electricity--the relationship of power, volt, and current, and best practices. Im too scared of ruined wires (best case) and fires from unfused lines direct to batteries. Im worried that posters in here dont understand things like how to properly size wire based on load, etc.

The amount of energy stored in my batteries would be enough to burn my bus down and kill me a few times over. Ive done tons of research, and use both fuses and breakers to protect every wire run. Im not gonna tear out a pretty wall to replace a melted wire.

Im not tryna be a jerk, but buy a book or find some answers and best practices before you start messin around. Things can get dangerous really fast. If your working knowledge of electricity isnt sufficient to know how to wire a battery in series or hook 12v appliances up safely with fuses, you shouldnt be living on or allowing others to live on your bus for safety's sake.

Again, not tryna be a jerk, people make a living as electricians for a reason. Ive seen stock Buses catch fire from shoddy electrical repairs and they speed at which the burn is shocking. No pun intended

[beyns]

I second that. You wouldn't go to an amateur dentist; don't sleep in a metal box wired by an amateur electrician.

[ird13]

Originally Posted by bubb, the real one

IRD


ird13,
the specific gravity test should work,
I would charge the up one day, then at night disconnect the batteries and let them sit disconnected all night, then check their voltage and the specific gravity,
12.6 or 12.7 is a full battery, less means it is getting old, below 12.4 or definately 12.3 and you may want a new battery, best to have identical batteries at least for the long term it is,

check the specific gravity also on each cell and keep notes,

I realize you may have plans for more batteries but you have panel charging capacity that is oversize for your batteries, depending upon how much power you use ever day you may want to disconnect one panel so you dont overcharge the batteries with too many amps,

Thank you for your help. We gave one of the batteries away and discovered a dead cell on the other remaining battery. Since then we have bought an 8D Marine Battery with 210AH as well as the meter for our charge controller. However we are STILL having issues The charge controller meter says at the peak of sunlight we are putting 20amps into the battery, but our battery had never read more than 3/4 full except when we bought it (it came fully charged). We have had NOTHING plugged into the inverter and still cannot get our battery past 3/4 using a float hydrometer. We have actually had so much trouble that we are making a craigslist ad to have someone knowledgable come look at it.

Any other suggestions before we pay someone for this? lol

[bubb, the real one]

is the specific gravity test saying the batteries are low or is it the charge controller meter that says 3/4 full.
what is the specific gravity reading?
when it is charging and the batteries are bubbling what is the voltage reading at the battery post, is it 14.8v?
if the specific gravity is good, and if it is putting 14.8v when charging and if the batteries are ~12.7v resting then the batteries are full,
the meter may need to be reprogrammed according to the manual, if I understand what you are saying,

[family wagon]

An inverter turned on, even with nothing plugged into its output, may still consume power (the amount varies). It might even have some drain when it's "off." You could disconnect the inverter input (and any other 12 volt loads, including any on the charge controller's load terminals?) in order to confidently say that there's zero load on the battery.

What about the instruments...? Might the hydrometer be bad? If you charge the battery in some other way, such as your own mains charger or have it charged at an auto parts place, then does the hydrometer indicate full charge? (You mention that "[the new battery] came fully charged" but it isn't clear whether that was tested with this hydrometer or another way.) Maybe use it to test other batteries that one would expect to find charged, such as in a few cars.

Back in #101 it was mentioned that the PV system worked great with one battery, and has trouble ever since the second battery was added. How can we verify that the charge controller was not damaged around the time the second battery was installed? Do you have a reliable DVM to measure the charger controller's output voltage and current to validate that its own measurement is accurate?

It might be to the point where it's worth at least asking the manufacturer about shipping the controller to them to be tested -- whether that's a service they would provide and at what cost.

[thecrabshomestead]

HEy Plasma,
WE are about to start wiring our bus next week, at least stubbing it out so we can finish the interior and all. And I am trying to figure out how many v/A/W whatever I need for everything. I am looking for either a solar fridge, or a electric/gas fridge made for small spaces so hopefully the energy usage wont be ridiculous. The only things that will be on the power is obviously LED lights, vent fans (12v I think), the water pump, the stove/oven is gas, and chargers for cell phones and laptops. I found electric outlets that have two plugs and 2 USB slots which is perfect for phones and tablets...I want ot make sure I have enough volts/watts no matter what, like if i decide to add a lcd tv later or something...What would the best option be for me if money isn't a factor. How many panels/batteries too...

[family wagon]

If money isn't a factor... then install conduit all over so you have the flexibility to add wires as appropriate later!

The outlets with built-in USB chargers are neat. But consider whether you'll always have the 120 volts on when you want to charge something.. in my case, I'll be running USB-charged things direct from the house batteries rather than from a 120 volt supply. If the house battery bank is 12 volt then it's easy to wire in a socket (or several) for a normal car charger. Power supplies called "dc-dc converters" can be used from any house battery voltage down to 5 volts at as many amps as you want if you want a more built-in feeling or have many USB things to charge simultaneously.

So long as the wiring goes to the places where power is needed, and it's adequately sized (in terms of wire gauge) then you can worry about the watts/amps/amp-hours for the battery bank and inverter later when the loads are better known. The biggest problem might be allocating the right amount of physical space now for a battery bank of unknown capacity.

[M1031A1]

Originally Posted by charles_m

I've seen stock Buses catch fire from shoddy electrical repairs and they speed at which the burn is shocking. No pun intended

Pun well received! I was almost re-volted.........

[charles_m]

If money was no object--I'd do it the way I did it. Of course, you can always splurge for a nicer set of batteries that are Lithium or some such, and a pure sine wave inverter, but I didn't have the buxx.

1200 Watts of panels into 8 Trojan T105's via a rooftop combiner box and Midnite classic 150 charge controller at 24v. My inverter is a 2400 watt tripplite that can also charge the bank from shore power, and provide 3600watts for up to an hour. DC load center with 175amp breaker on the disconnect and 0000 gauge wiring from the batteries to the load center.

I used 12/3 guage, stranded copper wire inside my bus for all the runs. Plastic outlet boxes, no places for the grounds or wires to touch the frame of the bus.

[jazty]

Originally Posted by family wagon

The outlets with built-in USB chargers are neat. But consider whether you'll always have the 120 volts on when you want to charge something.. in my case, I'll be running USB-charged things direct from the house batteries rather than from a 120 volt supply. If the house battery bank is 12 volt then it's easy to wire in a socket (or several) for a normal car charger.

I've been having good luck with these:


They can be found all over eBay and Amazon. I didn't like the blue LED on the front, though, so I disconnected it. It was always on when power was applied. As mentioned above, going this route will provide you with USB power all the time, instead of only when the inverter is turned on. Additionally, it seems silly to go from 12vdc->120vac->5vdc to power USB devices.

[family wagon]

Thanks for showing that, jazty. I hadn't seen those before! Was it difficult to crack open and re-close after "fixing" the blue LED? Did you happen to check the quiescent (no-load/idle) power consumption..?

[Scooternj]

Originally Posted by family wagon

Thanks for showing that, jazty. I hadn't seen those before! Was it difficult to crack open and re-close after "fixing" the blue LED? Did you happen to check the quiescent (no-load/idle) power consumption..?

I have something similar in my car, sitting in the power point. The draw on it is so minor, that my car fires right up even with after sitting with it in (and on) for weeks at a time.