Help Using up "Wasting" Power

inthejungle · September 2013

When I created my system I thought for sure that I was going to get by and have enough power, but not extra power. Well I have been running my system in the rainy season and have more power than I know what to do with. The dry seasons are coming and being located in Liberia, W. Africa I am going to have more power than I need.

Each day I discharge my battery about 20ah out of 350 so about 5-6%, I am trying to give my system a bit of exercise and make sure that it discharges down to about 20% each day or a bit more.

In order to do this I need to add something to the system that can run for a short time that could use up power through out the night or something that could just increase my usage. My system is 12vdc, with no inverter. Currently my big hitters are a Sundanzer freezer and a shurflo 12vdc pump.

My first thoughts would be to add:

1- a refrigerator
2- some sort of water heater for dishes that would run for about 15-20 minutes a day

Does anyone have any other thoughts of things that I could add on to waste current yet would be useful? Or do I keep the system as it is?

Thoughts?

ITJ

niel · September 2013

Re: Help Using up "Wasting" Power

a refrigerator may over tax your system. same with water heater, but at least the dishwasher won't be running as much every day as the refrig. you're in a hot location so maybe try some 12v fans.

vtmaps · September 2013

Re: Help Using up "Wasting" Power

How about just flipping the circuit breaker on the PV input and wait a couple of days until your battery SOC is down to where you want it.

If you waste power so that you can have a daily 20% discharge, your battery will last for ??? cycles. (the actual number depends on your battery) If you do what I suggest, your battery will last longer because you have a 20% discharge cycle every other day and it will take twice as many years to use up the ??? cycles.

--vtMaps

niel · September 2013

Re: Help Using up "Wasting" Power

yea, i thought of shutting it off too, but it is better to find a use for it and i think that is what he was asking.

inthejungle · September 2013

Re: Help Using up "Wasting" Power

Thanks for each of your thoughts- I have on occasion shut down the PV array by flipping the breaker, letting the system charging every other day.

I am just wondering if it is not better to occasionally get the loads to bring down the system to 80% preventing every day shallow discharges and charging

I am also wondering if it is good at times to add something that may take it down quickly, just before you go to bed flip on the load and let it bring it down to 75 or 80% over night from 100%

This would mean the batteries(rolls s-430 two of them in series) would see two kinds of exercise 1- daily discharges and 2- at times a quick discharge and charge to fill up the next day

Maybe the best question to ask is, is it better to get exercise like this or is it better to just preserve cycles and get longer life on the battery?

If exercise is better than what could I add on to make that happen?

Thanks

ITJ

niel · September 2013

Re: Help Using up "Wasting" Power

well i gave you the idea of the fans, but if you want to hunt around for a small refrigerator you can. try to do research on the draws as you don't want one with a heavy draw. i don't think the refrig is a good idea, but if you go for it and it is too much for the system then are you prepared to expand your entire system?. do you have television in your area as a tv for entertainment could draw it down some without killing it to? it's difficult to make suggestions when i don't know what's available to you or what you could consider usable.

being you may be concerned of your draws then i would suggest a battery monitor and a hydrometer, but i can't remember if i made those suggestions to you before or not.

inthejungle · September 2013

Re: Help Using up "Wasting" Power

Thanks so much for your replies,

We do not have TV, we listen to Short Wave Radio and check our e-mail:)

I have a Victron Battery Monitor hooked up and so I have a good idea of what goes in and what goes out. I also have a very good temp compensating hydrometer.

Were we are living there is nothing and so finding things to add is a bit challenging. The best way to do things is by doing them with Auto parts, one of the main reasons I kept my system 12v DC. I needed a security system for my panels, I used a car security system with door jam switches. I needed a radio I went to an old truck and grabbed one.

The refrigerator I thought about adding was a Sundanzer 50l, it is supposed to only use 10-15 AH a day.

Maybe I can help narrow the field a bit- two things that I have been thinking of beyond the refrigerator would be this, but I am having a hard time working out in my head how to do it:

1- We have limited propane access and I have to bring in whatever we are using. I thought if I have a bit of extra power trying to get a small something to help reduce propane use to heat our water for dishes and such, maybe it is just better to make a solar heater?

2- We live at about 90% humidity all day long- this means that our equipment cameras, laptops and such don't like this. If anyone is familiar with the old idea of a dry closet. I used to use old incandescent 220v bulbs on 110v to heat up a small wooden cabinet to dry it out. I looked into doing something like this with 12v but my number show that it would take 5 bulbs for 1 watt. Maybe someone know of a way that I could accomplish this to use up a bit more power?

Thanks for the thoughts?
ITJ

vtmaps · September 2013

Re: Help Using up "Wasting" Power

inthejungle wrote: »

Maybe the best question to ask is, is it better to get exercise like this or is it better to just preserve cycles and get longer life on the battery?

Is your goal to lower your long term costs of supplying your power needs? If so, then "wasting" power to discharge your batteries is not the way to lower your long term costs.

If you need the power, you should certainly draw down the batteries to get the power you need. If you draw them down for "exercise", it shows a need to spend money on batteries sooner.

You are correct that it is not good for batteries to be shallow (10%) discharged on a daily basis. If that is your situation, the cost effective solution is to flip the breaker on the PV input. By the way, some of the european charge controllers do that automatically... they incorporate a battery monitor and will avoid charging a battery that is still at a high SOC from the previous day's charge.

--vtMaps

Photowhit · September 2013

Re: Help Using up "Wasting" Power

inthejungle wrote: »

I looked into doing something like this with 12v but my number show that it would take 5 bulbs for 1 watt. Maybe someone know of a way that I could accomplish this to use up a bit more power?

There are 12 volt regular incandescent lights that have higher wattage, but to find them you'll want to look at a marine supply store, are you near the coast? I would suspect they would stock them, doubt there is much of a camping culture there, but some larger recreational vehicles would use something like this as well, here in the US the dome lights in cars are 10-12watts normally, so that might work with a couple.

niel · September 2013

Re: Help Using up "Wasting" Power

you might be able to use the older backup and brake lights on cars at 12v. don't confuse these with the newer led type bulbs out there now. if memory serves they are about a 2 amp draw each and would amount to about 24w dissipation. (this varies and you can look up the bulbs specifically as the common numbers are 1156 and 1157) if you put a few of those together do you think it would be sufficient to do the drying? in fact using a few of these for lighting at night would help to draw down some of the ah of the battery.

inthejungle · September 2013

Re: Help Using up "Wasting" Power

Thanks for everyone's thoughts- maybe the simplest thing for the short term is to charge the system every other day. Allowing the system to go a bit deeper before charges.

Maybe down the road I can put something else on. I will look into the auto lights, that maybe enough to dry out the box. Thanks for the suggestion

ITJ

BB. · September 2013

Re: Help Using up "Wasting" Power

Would pumping water to a cistern for irrigation/use by other residences be helpful (start your own "water company")?

-Bill

inthejungle · September 2013

Re: Help Using up "Wasting" Power

I don't know about starting my own water company- currently I am relying on rain water stored in large tanks for my water!

VtMaps- Question for you in a previous post you mentioned that some European charge controllers incorporate a battery monitor. I realized today that I may have a piece of a puzzle to allow me to use this and do just what you suggested.

I have a Victron BMV, I am wondering have you heard of Victron's Charge Controllers being able to link with there Battery Monitors and do just what you suggested? They are made in Holland and seem to be well respected.

Any one used a Victron charge controller? Any Good?

ITJ

vtmaps · September 2013

Re: Help Using up "Wasting" Power

inthejungle wrote: »

VtMaps- Question for you in a previous post you mentioned that some European charge controllers incorporate a battery monitor. I realized today that I may have a piece of a puzzle to allow me to use this and do just what you suggested.

I've never seen, let alone used a victron controller, but by internet reputation they are very good. Forum member stephendv has written that SMA and Victron have this feature. --vtMaps

Blackcherry04 · September 2013

Re: Help Using up "Wasting" Power

I'v got one these that I'v had for 25 years with a 12 V compressor that has worked like a champ. You could run it right off the batteries all day and eat up some Solar Production, it would take care of two problems. There are 10-15 different manufacturers that make them.

http://www.thetford.com/HOME/PRODUCTS/NorcoldIncRefrigerators/NRF60/tabid/843/Default.aspx

westbranch · September 2013

Re: Help Using up "Wasting" Power

A 12 v head lamp should use anywhere from 40 to 70 W for your dry closet.
Put it on an electric timer like this http://www.solar-electric.com/fldctico.html so that the light doesn't get too hot, have it run full time over a 24 hr period and then adjust as needed.

btw if you add your system specs to your sig line it would help in making workable suggestion :-)

stephendv · September 2013

Re: Help Using up "Wasting" Power

inthejungle wrote: »

VtMaps- Question for you in a previous post you mentioned that some European charge controllers incorporate a battery monitor. I realized today that I may have a piece of a puzzle to allow me to use this and do just what you suggested.

I have a Victron BMV, I am wondering have you heard of Victron's Charge Controllers being able to link with there Battery Monitors and do just what you suggested? They are made in Holland and seem to be well respected.

I don't _think_ the Victron charge controller can be linked to their battery meters. The manuals are online though, so you could double check whether it's possible or not.

The only charge controller I know of that have a feature to avoid an absorb charge if the battery is already pretty full is the Studer MPPT: http://www.studer-inno.com/?cat=mppt_solar_charge_controller and it doesn't work on SoC, only battery voltage. So there's a setting which says something like skip absorb if battery voltage is above X. (The SMA charge controller + Sunny Island combination also does this but based on actual SoC; but that's an inverter/charger + charge controller so doesn't fit the bill).

Victron inverters are very popular around here and have been sold for a long long time. However, their MPPT charge controllers are fairly new and there were some quality issues with the first batch which I _think_ they've addressed. Be-aware that some of their MPPT models can only work with off-grid panels because of their low-input voltage limitation. This sort of defeats one of the big benefits of choosing an MPPT controller... so be sure to get the right model. Specs and feature wise, there doesn't really seem to be any compelling reason to choose the Victron MPPTs over the likes of midnite or outback.

Help Using up "Wasting" Power

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Help Using up &quot;Wasting&quot; Power

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Help Using up "Wasting" Power