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Author Topic: Battery advice  (Read 7106 times)
profp
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« on: May 24, 2011, 08:33:43 AM »

Our PV system has grown organically, and we're fine with that - we never expected it to work anything like as well as it has, and it was originally only intended to provide lighting at night when the generator was off. In reality, PV is meeting 80-90% of our total electrical demand, way beyond expectation, which is all well and good - but the 'suck it and see' Exxon leisure batteries and motley crew of ancient forklift cells are struggling to cope with the gradual increase in load over time as we've added more 'essential' kit, and we're also unable to store significant surplus that is generated during the day. We're now averaging around 1.8kWh per 24 hours metered AC consumption post inverter. So we're now looking at investing in 'proper' batteries. Budget is not bottomless, and logistics are complicated so there is a significant benefit in  choosing cells that one person (or two max) can life safely single handed and if they are supplied dry, that helps with both weight and handling considerations. We run a 24V system, max rated draw 100A (I reckon average draw is around 5A), charged by 480Wp solar in super-sunny location. In an ideal world, I wouldn't spend more than 1,500 but I'm hoping for my investment to last me 5-10 years with care, and I'd rather do the right thing than economise.

My current thoughts are Rolls 4000 or 5000 series - the 4000 series seems to be cheaper, and offer comparable C20 capacities, but the 5000 series offer better C100 capacities over the 4000 for similar C20 ratings. Looks like my budget would be stretched by 5000 series. S-600 450Ah x 4 might be a good choice, and my overnight discharge would be a shade more than 10% of C20. Trojan L16H 420Ah  is also an option. Or I could go down the forklift route again, but this could be a major headache logistically, as most new packs seem to use welded straps and I would have to break into individual cells for transport - costs are more difficult to find on-line.

So any advice on Rolls 4000 vs 5000 or Rolls vs Trojan. Looks like Navitron doesn't supply these kind of batteries (any more? I think they may have done in the past?), so any PMs for suppliers would be appreciated.
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stephendv
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« Reply #1 on: May 24, 2011, 09:35:58 AM »

When I priced up new batteries sometime last year, the forklifts were the best value for money.  I got mine from sunlight.gr and they shipped straight from the factory in Greece, the total cost including transport to Spain was about 30% less than similarly sized Rolls 5000 from a local reseller.  Yes, the logistics were a person and I had to ask a local company if they would accept the delivery on my behalf because they would only deliver to industrial estates with forklift facilities to unload the truck.  Then I had to spend another few euros hiring a local transport guy with truck + crane to lift them into place.  they were still financially worthwhile though.  You may have better luck ordering through a distributor who could deliver them onsite.
Even 1000kg of battery was moveable with a manual pallet trolley to get them into their final resting place.
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profp
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« Reply #2 on: May 24, 2011, 09:43:43 AM »

I live on a small island, only accessible by boats <20ft, onto the beach... Everything has to be manhandled by hand, and lifted into/out of the relatively high sided boat.  Pallet trolleys, cranes etc. are not an option, sadly. If I can find a supplier who can deliver individual, dry forklift cells that would be workable tho.
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« Reply #3 on: May 24, 2011, 11:18:24 AM »

I live on a small island, only accessible by boats <20ft, onto the beach... Everything has to be manhandled by hand, and lifted into/out of the relatively high sided boat.  Pallet trolleys, cranes etc. are not an option, sadly. If I can find a supplier who can deliver individual, dry forklift cells that would be workable tho.

Been there, got the book, the video and T shirt Prof  Grin Go for the Rolls every time, much easier to handle, far less likely to fall over in a boat and a much stronger casing if they do  Grin

As for which particular Rolls, that's between you and your wallet  Grin

I live on an island now that actually has a ferry but for four years was in a similar position to yourself where everything revolved around the weather and how high the tide was  Roll Eyes

Good luck, Paul
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'Off grid' since 1985,  Proven 2.5kW, Proven 6kW direct heating, SI6.OH, 800ah Rolls, 4.75kW PV ,4xTS45, Lister HR2 12kW, , Powerspout pelton, Stream Engine turgo, 60 x Navitron toobs and a 1500lt store. Outback VFX3048 and 950ah forklifts for backup,
Eleanor
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« Reply #4 on: May 24, 2011, 12:37:24 PM »

I agree with Paul and would go for Rolls if money was no object. Our comedy forklift bank was around 2400 for 1050Ah at C5 so around 1300Ah at C20. If we ever get a replacement bank we'll have an aeration system so we shouldn't need to overcharge to mix the electrolyte. I'm not sure our Victron charger is right for the bank either as the cells are supposed to be charged at a constant current until they reach 2.67V to be fully charged and we're considering buying a forklift charger.
« Last Edit: May 24, 2011, 01:49:31 PM by Eleanor » Logged

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billi
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« Reply #5 on: May 24, 2011, 02:46:15 PM »

Hi

I got my second hand forklift battery 1600 ah @ 24 volt   shipped from Germany  to South West of Ireland for 1500 Euro  in total  and the cells are connected with screw type connectors

So far i am very happy ( But it was a risk )

Eleanor you can change the charging setpoints in your Victron  if you use VE-Configure and your computer  , i can sent you the computer adaptor  , if you like .
Perhaps i find the temp sensors as well that i have got ....

Anyhow you can download the VE configure software and play around even with no connection to your system and find out if the adjustments  could be helpful
Billi
« Last Edit: May 24, 2011, 09:22:40 PM by billi » Logged

1.6 kw and 2.4 kw   PV array  , Outback MX 60 and FM80 charge controller  ,24 volt 1600 AH Battery ,6 Kw Victron inverter charger, 1.1 kw high head hydro turbine as a back up generator , 5 kw woodburner, 36 solar tubes with 360 l water tank, 1.6 kw  windturbine
profp
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« Reply #6 on: May 25, 2011, 07:42:51 AM »

Thanks all - that was really helpful. Off to sharpen ninja negotiating tactics now!
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Eleanor
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« Reply #7 on: May 25, 2011, 05:04:40 PM »

Hi Billi, thanks we have the adaptor and have changed various settings on the Victron. The PzS chargers seem to have a different charging profile to the settings in the the Victron and have another stage after absorption where the voltage rises to 2.65V. I think this is only for equalisation so maybe the Victron is alright with an aeration system and equalisation only when necessary. I think I need to read DIN 41773-1 and DIN 41774 to fully understand. There is some information here (Download No 11 for you and 11e for me) :
 
http://www.zvei.org/fachverbaende/batterien/publikationen
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stephendv
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« Reply #8 on: May 25, 2011, 05:38:00 PM »

Hi Eleanor,

The PzS charges don't use the bulk-aborb-float charging cycle at all.  AFAIK, they charge according to taper (Wa or WoWa) characteristics which are designed to charge a huge battery from 20% SoC to 100% SoC in 10 hours or less.  I don't think this is necessary for PzS batteries used in off-grid environments and the usual IUoU charging characteristic used by every inverter/charger on the market is just fine.  As far as I can make out the difference in chargers is because of a difference in the usage pattern, not some inherent difference in the battery chemistry.

Looks like an evil pirate has hacked my server and uploaded a copy of the Battery Technology Handbook to: www.casanogaldelasbrujas.com/Battery_technology_handbook.zip  which describes everything you ever wanted to know about lead acid batteries... will take me a few hours to contact the server administrator and have it removed...
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« Reply #9 on: May 26, 2011, 09:30:17 AM »

Stephendv

 exhappy:Bless the pirates, I have been looking for a copy of that book for years, I found an old copy in the library 20 + years ago but after having it on loan 4 times in a row they wouldn't let me have it again, someone else was after it. Never seen it since.

Again many thanks to the public mind pirates Tongue

A little light reading me thinks.


Best Regards

Fred
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Eleanor
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« Reply #10 on: May 30, 2011, 10:51:42 PM »

Stephen, thanks for posting the book. Unfortunately I missed it and I've been looking for a big book on batteries. Probably for the best as the more I read about them the less I seem to know  facepalm.

In the link I posted above there seems to be an IUIa profile which has a flat bit in the middle before gradually rising up to 2.65V. This end of charge voltage of 2.65V seems to crop up everywhere with PzS cells and I'm guessing that the main reason is to reduce the need for equalisation and as you say all these profiles seem to have been devised to optimise charging times. The constant current charger seems to be the one our supplier, manufacturer and various others are suggesting should be used. A number of times the phrase "the cells need to reach a voltage of 2.65V to be fully charged" has been used but I'm not really sure what it means in practice. I feel that the Victron is fine and with aeration most of the problems the charger profiles are trying to solve would go away. However, we need to increase our charging capacity so it may make sense to buy a charger that is recommended for the batteries and use it weekly (I've no idea how much they cost faint) to avoid any debate on how the cells were charged  fight


* IUIa.jpg (28.7 KB, 650x358 - viewed 1490 times.)
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billi
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« Reply #11 on: May 30, 2011, 11:24:26 PM »

any news on more PV    stir



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1.6 kw and 2.4 kw   PV array  , Outback MX 60 and FM80 charge controller  ,24 volt 1600 AH Battery ,6 Kw Victron inverter charger, 1.1 kw high head hydro turbine as a back up generator , 5 kw woodburner, 36 solar tubes with 360 l water tank, 1.6 kw  windturbine
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« Reply #12 on: May 31, 2011, 12:42:59 AM »

Billi, PV is imminent  Shocked I think our set up will be similar to yours with 2.4kW and the Outback - just need to go back over all the discussions we had before about dumploads. Mindy is away for corrective action but when she returns we'll have about 4kW of combined generating capacity. I haven't got it totally clear as to how it will work but for a large part of the year I imagine we'll have more electricity than we need and the batteries will be fully charged just using the PV  Cool
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billi
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« Reply #13 on: May 31, 2011, 01:09:30 AM »

i really do appreciate  the move , when i had some spare cash to get more PV two years back ,

In our house , that move decreased the argument " Do we have enough electricity for another washing-machine, or do we have to run the diesel ?"  considerably


So basically we  only argue  around Christmas  nowadays  Grin  and i guess thats normal family live  facepalm

Hope next Christmas will be windy , or rainy or sunny  hysteria


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1.6 kw and 2.4 kw   PV array  , Outback MX 60 and FM80 charge controller  ,24 volt 1600 AH Battery ,6 Kw Victron inverter charger, 1.1 kw high head hydro turbine as a back up generator , 5 kw woodburner, 36 solar tubes with 360 l water tank, 1.6 kw  windturbine
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« Reply #14 on: May 31, 2011, 07:33:46 AM »

That's an interesting charge curve, never seen that ending charge before.  Couldn't you achieve the same thing by tweaking the Victron's EQ charge settings?  E.g. program its normal charge profile for a slightly higher absorb voltage (2.45V ?) and then program it to EQ every week at 2.65V for a short period of time. 
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