Battey Help!

[djbuzz]

Hi all,

I'm new to solar and have purchased the following items to run some items in my office, it was never intended to make money, more of a project!

2 * Used 170w panels (Vmp - 35v, Voc - 44v, IMP - 4.86A, Lsc 5.36A (35v * 4.86A = 170.1W)
1 * 30A charge controller (http://www.bimblesolar.com/offgrid/chargers/solar30) - very cheap!
1 * Cheap ebay 500w inverter
1 * Second hand YUASA SWL2250 (FR) battery (link for data sheet) http://www.yuasaeurope.com/images/up...SWL2250_UK.pdf

It's been set up for around a week and gets to the float voltage pretty quickly, however last night I switched the inverter on and run a pc, tv etc (around 200W) for 30-35 mins before the alarm on the inverter started and shut down, the charge controler displayed the voltage had dropped to 10.1v, as soon as the inverter shut down the voltage "bounced" back to 12.5v.

Am I expecting too much from one battery as I presumed I would get around 3 hours usage @ 200w even including losses.

This is how I calculated the battery capacity 76A * 12V = 912w from full (and new) to dead, I suspect the used battery is more used than was advertised, although could anyone shed any light on what to expect from this battery in the real world? I understand that 912w in the battery does not mean 912w to appliances as the inverter will only be 80% efficiency but 200w for 30-35 mins is still pretty poor.

Would it be worth charging the battery to the Cyclic (or Boost) charge - 14.5v as I've read that that can help with sulfation?

Any assistance or advise would be greatfully recieved.

Thanks,
Barry

[Naptown]

You need to dump the Pwm controller for an mppt you are losing a lot of charge power there however with that battery it may not be a bad thing.
Two things I think are getting you
An old battery Check with hydrometer and perhaps equalize if allowed.
Second thing is peukert's law
Google that one.

[Sunking]

You have three problems.

1. You only have a 75 AH battery, it is used and seen its better days. At 200 watts load even if brand new would only last 1 hour.
2. Way too much panel wattage, although it is not being used because of incorrect charge controller. With 340 watt panel operating at 12 volt battery requires a minimum 240 AH up to 360 AH battery.
3. Your panels are not compatible with a PWM Charge Controller. With those panel you are only getting 60 watts out of them because you you are using a PWM controller. Your panels are Grid Tied Panels, no tbattery panels. That means you must use MPPT Charge Controller.

So here is what you need to do, Get rid of the Charge Controller and Battery. Buy a minimum 30 amp MPPT charge controller and a good deep cycle 12 volt 300 AH battery. Then you can run that 200 watt load up to 8 hours.

[Mike90250]

.. a good deep cycle 12 volt 300 AH battery. Then you can run that 200 watt load up to 8 hours.

Most places, a 12V 300ah battery is pretty hard to find. A common "close enough" would be a couple of 6v, 200ah golf cart batteries wired in series giving you 12V @ 200ah. Not too expensive, but good for a beginner. And you have to get a MPPT controller to keep the battery properly charged.

[Sunking]

Most places, a 12V 300ah battery is pretty hard to find.

Very true Mike but the point is his system is so far out of balance he needs to start over from scratch. Only thing he can reuse is the panels. Everything else is file 13.

[djbuzz]

thanks all

Hi all,

Thanks for all the replies, I need to have a think about what to do moving forward, I "only" spent £385 on everything so far, £150 panels, £40 charge controller, £85.00 inverter, £60.00 for the battery and around £55 on cables.

To upgrade to an MPPT charge controller would cost around £120 for a rubbish one and a 300 amp 12v battery bank is gonna cost around £300.00 would I not be better off purchasing a grid tie inverter (link = http://www.orionairsales.co.uk/maste...Fcad4AodDCgAdw)

Thanks,
Barry

[Sunking]

Hi all,

Thanks for all the replies, I need to have a think about what to do moving forward, I "only" spent £385 on everything so far, £150 panels, £40 charge controller, £85.00 inverter, £60.00 for the battery and around £55 on cables.

To upgrade to an MPPT charge controller would cost around £120 for a rubbish one and a 300 amp 12v battery bank is gonna cost around £300.00 would I not be better off purchasing a grid tie inverter (link = http://www.orionairsales.co.uk/maste...Fcad4AodDCgAdw)

Thanks,
Barry

Well Barry now you have learned what we have known for years. Never take anything off-grid battery unless there is no other alternative. Anything you take off grid is going to cost you some 10 times more for electricity as opposed to buying it from the power company for the rest of your life.

If you want to run say a 200 watt load for 5 hours per day in your area you are looking at a panel wattage of about 500 to 750 watts, a 60 to 80 amp MPPT controller, and a 12 volt 400 AH battery. YOu have only made a down payment at this point of 2 solar panels. You still need another $2000 USD to get more panels, batteries, and charge controller. The really fun and educational part is you get to replace that $1000 USD battery every few years.

[john8750]

If you must spend more money, it would more reasonable to buy the power from the city. All most all my stuff was free from a friend. I run my small shop on it. About 300 watts max, will last more time than I spend there and charge back up fine. 600 watt panel on roof.
The cost for an MPPT CC would be high. I built my own PWM charger, works fine.
BTW, 300 AH 12 volt battery is available. Mine were used for stand by building generators. I think about $250.00 each.

Buy your power from the city unless your stuff is free. And keep the fun in it.