Should my batteries and solar have a load ?

[OldManMirage]

I have 230 amps of battery power using 2 Duracell flooded golf cart batteries in series with 200 watts of solar panels running through a Renogy Duo controller. The boat is in her slip in Jacksonville Florida so good sunshine most days this time of year, batteries staying well charged. The only thing running is a Hella Turbo fan I leave going.

Should I have more of a load ? I have a 12 volt portable refrigerator I could set up that would give the batteries something to do.

I guess I'm concerned that they will simply sit there and "cook" even with the controller managing things. The batteries are new, I just finished getting them set up. I will of course keep up with checking battery water level.

Or am I just over thinking this ?

[Paul Elliott]

You don't want to cook your batteries, but as long as your controller is set up appropriately this shouldn't happen. Batteries do have a limited cycle-life so adding an unnecesary load isn't going to help.

My boat has a quite large AGM bank. I occasionally go sailing where I spend perhaps a month cycling through deep discharge/charge cycles, but it's gone years at a time being only lightly used, but most of the time it's sitting in the slip with the solar panels keeping the bank charged. The batteries are over 20 years old, and the bank still has about 75% of its original capacity (I do a load test every year or two).

[StuM]

First: I presume you mean you have a battery bank storing 230 AMP HOURS of energy.(Not amps and not power!!!)


Secondly: Your controller will maintain your batteries at float, trickling a bit of energy as required to counteract self-discharge. No harm, no cooking!



Adding loads to the bank will have no advantage. All that will be happening is that during the day the fan will be driven directly by the power from the solar (not from the batteries) and at night the fan will partially discharge the batteries, which the solar will top back up each day. So you are actually accumulating charge/discharge cycles on your battery( even if only slightly).



Adding more loads would just increase the overnight discharge and daily charge regime, with a probable (but slight) decrease in battery life.

[Uncle Bob]

Originally Posted by StuM

First: I presume you mean you have a battery bank storing 230 AMP HOURS of energy.(Not amps and not power!!!)


Secondly: Your controller will maintain your batteries at float, trickling a bit of energy as required to counteract self-discharge. No harm, no cooking!



Adding loads to the bank will have non advantage. All that will be happeining is that during the say the fan will be driven directly by the power from the solar (not from the batteries) and at night the fan will partially discharge the batteries, which the solar will top back up each day. So you are actually accumulating charge/discharge cycles on your battery( even if only slightly).



Adding more loads would jusr increase the overnight discharge and daily charge regime, with a probable (but slight) decrease in battery life.

Hey Stu, have you tried the spell checker, works a treat.

[StuM]

Originally Posted by Uncle Bob

Hey Stu, have you tried the spell checker, works a treat.

Thanks, I've edited the typos

[Shanachie]

Originally Posted by StuM

First

Adding loads to the bank will have no advantage. All that will be happening is that during the day the fan will be driven directly by the power from the solar (not from the batteries) and at night the fan will partially discharge the batteries, which the solar will top back up each day. So you are actually accumulating charge/discharge cycles on your battery( even if only slightly).
.

The amp hours police guy strikes again. Really, do you spend all of your time scrolling CF for people who neglect to add "hours" when they refer to amps in a battery?



Get a life, man. People understand what the OP was saying.


Anyhow, I want to correct something you said. The solar controller would feed power directly to the boat only if the load function is used.


Manufacturers recommend against that because, if a cloud passes by and the load is larger than the input, it could blow the fuse or worse. Electrical stuff is powered by the batteries, which are replenished by the panels.

[Paul Elliott]

Originally Posted by Shanachie

The amp hours police guy strikes again.[...]


Anyhow, I want to correct something you said. The solar controller would feed power directly to the boat only if the load function is used.


Manufacturers recommend against that because, if a cloud passes by and the load is larger than the input, it could blow the fuse or worse. Electrical stuff is powered by the batteries, which are replenished by the panels.

In this case the misuse of "A" as opposed to the correct "Ah" didn't cause any difficulty, but I hope you will admit that this mistake can often cause great confusion.

But I agree, when a load is connected to a battery, and a solar panel (or other source) is charging the battery, then this does not "power cycle" the battery. If the load consumes less than the charging source is providing, then the battery is still being charged. The charging current doesn't go into the battery and then back out to the load.

[StuM]

Originally Posted by Shanachie

The amp hours police guy strikes again. Really, do you spend all of your time scrolling CF for people who neglect to add "hours" when they refer to amps in a battery?

No, but I do correct the error every time I see it. Did you read and learn anything from the post I linked to after all of your egregious errors in the previous thread.

If not, here's the link again. http://www.cruisersforum.com/forums/...ml#post1933764

[StuM]

Originally Posted by Shanachie

Anyhow, I want to correct something you said. The solar controller would feed power directly to the boat only if the load function is used.

Manufacturers recommend against that because, if a cloud passes by and the load is larger than the input, it could blow the fuse or worse. Electrical stuff is powered by the batteries, which are replenished by the panels.

Again with the incorrect information. In this case, two major errors of fact.


1. "electrical stuff is powered by the batteries" - it's a misconception that energy passes "through" a battery bank when you have a power source and a load connected to it.Both power source and load are connected to the same pair of +ve and -ve battery terminals. In effect there is a direct connection between the two.

If the power source is providing sufficient power to supply the load there is no current flow out of the batteries. If the load is greater than the input then the batteries will supply the additional power that the laods need.

If the input is greater than the load, then the excess power will go into the batteries to charge then if they need it.



2.It has nothing to do with the "load function" and you misunderstand what a "load" port does.
Your solar controller monitors your battery voltage. Any loads connected to the Load connectors will be disconnected if the battery voltage drops too low.Nothing to do with the power input levels.


It’s not what you don’t know that kills you, it’s what you know for sure that ain’t true. - Mark Twain

[Stu Jackson]

Stu, please keep up your good work. Naysayers who don't know or care about the proper use of units also seem to misunderstand the way the rest of the system works, too. Careless...in many ways.

[goboatingnow]

What happens very much on what your battery charger is set to

In some cases the charger will not start a charge cycle until a certain amount of power is drained out of the batteries. Hence the load is supplied initially from the battery , in some cases the charger will act as a “ power supply “ and simply maintain a constant fixed voltage typically just above battery float point

If you model the resistances involved some charger current may flow into the battery and sometimes it may ( for all intents and purposes ) flow to the load.

[noelex 77]

You do not need to add a load, but if the batteries are sitting for long periods with little or no load it is sensible to reduce the battery set points.

The ideal battery charging algorithm is different for cyclic use and for storage.

Reducing the bulk/absorption by around 0.2v and the float voltage by 0.3v is a reasonable start. It is also important to reduce the absorption time. Most solar controllers will start a new bulk/absorption cycle each solar day and keep the batteries at this voltage for a couple of hours. This is appropriate if the battery has been partially discharged overnight, but will overcharge a battery that has no load and is sitting at 100% SOC. Reduce the absorption time down to just a few minutes.

[OldManMirage]

Thanks for the replies. I kinda thought I was over-thinking it a bit.

I will look into adjusting my settings to reduce the float voltage for now, that seems like a fine idea. It's set to 14.6V at the moment, that's the factory setting for flooded batts.

I do wonder if it's ok to say "batts" though. Does everyone know what I mean or do I need to add "eries" so I don't start another thread drift ? ?

[StuM]

Originally Posted by OldManMirage

I will look into adjusting my settings to reduce the float voltage for now, that seems like a fine idea. It's set to 14.6V at the moment, that's the factory setting for flooded batts.

Whoa! 14.6 is far too high for float with flooded lead acid batteries. It should be more like 13.5 ( ±0.1-0.2°C depending on ambient temperature). For long term minimal use, I'd drop it to more like 13.2


Are you sure that's not the absorption voltage?

[thomm225]

You can probably look up the proper Float Voltage for your batteries.

I have mine at 13.5 or 13.6 volts in season (one controller reads .1 volt off from the other) when I'm using the boat and 13.2 in Winter.

Or I unplug the solar completely for a week or two at a time and monitor the Voltage which usually stays at around 12.6 volts. This in Winter.

I have two Golf Cart batteries also of 220 AH

14.6 volts sounds like your batteries Absorption Voltage level. One of my PWM Controller will take the charge to 14.6 volts when I first hook it up so it has a sort of Absorption phase then drop it back down to 13.6 volts after a bit.

Soon I'll mount my Victron 75/15 MPPT (Bluetooth) Controller which I believe is defaulted at 13.6 volts Float and 14.4 volts Absorption.

When I'm not sailing I just use one panel to keep the batteries charged which is my old 65 watt panel through an old PWM controller. (it's at 13.5 volts)