My Solar Install

[Night Sailor]

Ran the furnace some last night, and one side of the electric blanket on 5. I over slept this morning. When I got out of bed at and checked the state of charge, I found my batteries at 91.4%, -35.8AH, and 22.4 Amps going into my batteries (inverter and furnace switched off). These solar panels are doing amazingly well. The charge controller has more power than the batteries can accept. I will be switching the inverter back on and seeing how things go today. The fridge pulls about 28 Amps DC through the inverter. I find myself thinking more and more about a DC powered compressor type fridge. If the cost was not so high I'd do it. That would only require 4.5 Amps and the duty cycle would be 25% this time of year. I could get one day of cooling for what I use in one hour with my present fridge.

[J.R.]

Voltage is not a true test of a battery. The best test is to place an electrical load on the battery and check the results with a meter designed for this test. Another way is to check the condition of the fluids using a special hydrometer which can be found at many big box and auto parts stores.

[Glenn Baglo]

If you buy the hydrometer, pipe insulation ( or maybe a piece of pool noodle ) is a good way to store it when not in use.

[Night Sailor]

Originally Posted by J.R.

Voltage is not a true test of a battery. The best test is to place an electrical load on the battery and check the results with a meter designed for this test. Another way is to check the condition of the fluids using a special hydrometer which can be found at many big box and auto parts stores.

What is fully charged? I don't give a darn about the last 8 AH of capacity. Fully charged for me is 98% or above.

Hydrometers only work with flooded batteries. Pretty much useless these days. I haven't used one in 40 years.

I don't use just voltage, although I monitor it to ensure my charge specs are not violated.

My charge controller is a three stage charger. While I'm sure a full charge is not in fact a full charge, it is accurate within 2% of fully charged. Batteries can take days to reach a full charge, which is irrelevant for my purposes as I use the sun to recharge it will never reach a true full charge unless remove all loads for several days.

I fully charged my batteries when I first got them and that will be it for a while. I don't intend to plug in any time soon.

I use a number of factors to monitor my charging--a battery monitor, which includes temperature status. Battery temperature will show how close it is to fully charged once in float mode. Temperature drops in the final stages of charging. Record keeping helps establish typical parameters which vary by battery.

My solar panels were producing 29.8 Amps here at 2:29pm and only .5 amps are going into the batteries, the balance is going into running my energy hog fridge via the inverter. Now I am losing -0.7Amps as the inverter fan is kicking on and the sun can't meet the extra bit of demand. It is not a perfect system, but a very good one.

[tmaken2157]

i have to say sir, you are the exception, you have a surplus of energy based on the selection of solar panels...well done.

I look forward to starting my solar adventure. I'll mount the panal to the TV to take advantage of the sun while moving to the next spot....I do have a question thou...do you have to worry about. back feeding into your TV during transit?

[Night Sailor]

Originally Posted by tmaken2157

i have to say sir, you are the exception, you have a surplus of energy based on the selection of solar panels...well done.

I look forward to starting my solar adventure. I'll mount the panal to the TV to take advantage of the sun while moving to the next spot....I do have a question thou...do you have to worry about. back feeding into your TV during transit?

Good point Todd.

I suppose I should put a manual switch to isolate the two. The question is where?

I was thinking about a battery isolator, but it seems unnecessary if I use a switch. I have been unplugging it when parked.

A switch seems simplest.

[frankcfx]

A note on connectors:
LOOKING AT THE MC4 connectors the pins appear to be much like the low amperage Molex pins. I am using 25 amp Anderson Power pole connectors.

[Night Sailor]

I use Anderson power poles with my Ham gear. I have piles of them and
honestly I'd gladly get rid most applications. I like Wago DIN Rails or old style ring terminals better.

Anderson Power Poles have problems with 10 gauge wire. The stiffness of the wire can pull the contacts apart raising the resistance and melting the thing into a glob of blackened plastic. They will work but you have to be very careful that the wire does not stress the connector mechanically.

If you want to use those, I'd also recommend using modelers glue to bond the red and black connectors. And you should also slather in some liquid electrical tape in the backside of the connectors.

[frankcfx]

Well hello NS from AF0XX. As an EE you probably remember not to cause pull on a connector. Where did you get the wheel chair drive wheels and control?

[Night Sailor]

Originally Posted by frankcfx

Well hello NS from AF0XX. As an EE you probably remember not to cause pull on a connector. Where did you get the wheel chair drive wheels and control?

Perhaps the two topics got crossed. I was referring to the smaller Anderson Power Poles which are limited to 40 amps. The big heavy duty ones that you see on wreckers or for connecting heavier loads like an electric motor are pretty robust. I don't know what he was using on the chair drive.

[Night Sailor]

I have something interesting to report.

We had several days of overcast, with a deluge in the middle spanning two night and the entire day in between, and closed out with half a day of fog today. For the first time my panels were not able to recover to a full charge the next day, or even the day after. Tomorrow should see me topped off again.

Aside from making sure things were turned off when I was away from the camper, I used my normal loads, and perhaps a bit more as I was stuck inside some of the time and I wanted to exercise the system some. The rain was so loud I did not sleep well. I used my electric blanket every night, as I have since I first got it, first on high (10) to warm up my bed and then dialed back to 3 or 1 overnight--which account for between 20 and 40 AH. I recharged my laptop, watched TV, and ran my other normal loads.

What I take away from this is my panels can recharge my batteries rapidly when I am more deeply discharged, but in this case they can't do the final top off charge because that takes a few hours at lower charging currents and I run out of daylight. I could handle another day or two of very dark overcast conditions or heavy rain and expect a pretty rapid recovery once the sun comes out, and still be above 50% capacity. I estimate I can recover 180AH, or perhaps much more, of discharge if I was discharged to greater than 200AH. So if I don't care about recharging the last 15-20%, which takes longer, I can cycle a bigger daily load if needed without any problems, as long as I fully recharge it periodically.

I have been slack at recording data, so the data is a bit sparse compared to previous weeks.

Being able to simply switch off all DC loads except the refrigerator with one switch, and the Inverter with another is all I really need to do. Knowing the charging currents is nice though as I sometimes throw the surplus electricity into running my refrigerator though the inverter.

The AH capacity of the bank is 400 AH, so when above 100AH, the percentage should have been below 75%, which it was not. It is a very small error, and has to do with the battery monitor synchronization. Taking it up to a full charge using a shore power connection for several days would fix that.

Note that in heavy overcast and rain, I was still pulling 2-3 amps charging current out of 630 watts of panels which represents 6% of the maximum amount for horizontal mounting. This is for three sets of two panels in series. Equivalent to three 210 watt 36 volt panels in parallel. In any event it is an interesting percentage which can be used to estimate charging for panels mounted in a 36 Volt configuration.


Here is what I recorded:
Battery %, Amp Hours used, Charge or (-) Discharge rate, F-furnace, I-inverter, Battery Voltage, Battery temperature (F), Ambient temperature (F-A), C-Cummulative AH's recovered.

Apr 29: cold overcast
0217: 92.6%, -31.1AH,-7.8A. F & I on , 12.54V, 79F , 47F-A1112: 87.2%, -52.2AH, 2A, 12.68V, 75F , 47F-A , (w/F&I off 5A)
Left DC off but inverter on idle
2345: 89,8%, -42.4AH, -5.3A F on, 12.48 V , 70 F , 42.1F-A

Apr 30: rain, dark
1302: 75.3%, -101.2AH, 0.0A,12.34V, 70.5F, 43F-A, everything off 2.1A
1329: 2.9A

May 1: fog, clearing in early afternoon, becoming sunny and clear
0109: -93.2 AH, furn on, -3.2A, -6.8A w/inverter on
1059: 67.4%, -133.4 AH, 7.1A, 12.30V, 74F,
2003: 94%, -22.0 AH, -0.6A, 12.92V, 88F, 63F-A, C111.4AH.

I recovered 111.4 AH today. I am happy with that.