I want an old prius battery

[peal]

Yep, why not get a generator?

[Dark Orange]

Yep, why not get a generator?

Couldn't be arsed going out and turning it on every time I want to use the phone or send an e-mail.

and this...

What I meant was if you have a battery for emergencies, you might as well have a solar panel and use it regularly as well. With your 12/24V setup you don't need to buy an expensive inverter. Use your 12V instead of 240v everyday to reduce your electricity bill and as long as you have a decent sized battery you will have emergency power as well.

If you take this one step further and have a grid connection as well this is called distributed storage. Electricity generation feed in credits are heading towards zero. In the future utility companies will pay storage credits if you have enough capacity. It's all about making the power available when people need it, rather than total gigawatts generated. As more renewable sources come online this will be more and more important.

That is my line of thinking. In years to come when a major percentage of vehicles on the road are hybrids, second-hand batteries will be more available and rather than recycling half-useful batteries, they can be potentially used for this purpose. I am just playing with the idea, seeing how useful they actually are. If it is viable, I'll start looking into an inverter and feeding it back into the system at peak times.

[GSRman]

I'd be looking at a hybrid solution - small UPS (run some sealed lead acid batteries) to power ADSL etc - shouldn't be hard to run that for 24 hours off battery - and then a genny to charge the laptop - UPS, and consider getting some topup bats for USB powered stuff.

maybe something like this http://www.techbuy.com.au/p/204103/M...et/KN-6327.asp

[rollin7]

lets aproach this another way... what is your budget?

[Dark Orange]

lets aproach this another way... what is your budget?

I am in the middle of buying a 6 bedroom, 6 bathroom house, so budget = a couple of hundred dollars. I probably have all the ancillary hardware stashed away somewhere (24v UPS hardware, DC->DC inverters etc) so if I can buy an old battery pack for under $500 I'd be happy. Doesn't need to be new or reconditioned, just functional. I think there is enough capacity in one of them to do all I need of it.

[BigMuz]

We had a Honda generator like that running NON STOP for four days on less than a single 20l drum of fuel. They are almost silent and awesome.

had my coffee machine and a full sized fridge plus everybodies phone/ laptop/ battery chargers.

[rollin7]

I am in the middle of buying a 6 bedroom, 6 bathroom house, so budget = a couple of hundred dollars. I probably have all the ancillary hardware stashed away somewhere (24v UPS hardware, DC->DC inverters etc) so if I can buy an old battery pack for under $500 I'd be happy. Doesn't need to be new or reconditioned, just functional. I think there is enough capacity in one of them to do all I need of it.

what exactly are you powering, and for how long do you want to power it?
will this setup be portable, or stay in the one place forever?

[Bozz]

Lead acid/AGM/calcium/gel/whatever is not cheaper than LiFePO4. The best lead battery will give you about 300 cycles to 50% depth of discharge (discharging further will cause permanent damage to the battery). LiFePO4 will give you 3000 cycles to 80% DOD and 5000 cycles to 70% DOD. Lithiums give you literally 10 times the life of lead, can be discharged further so they store more energy, and if high current draw is neccessary they sag a lot less (peukert effect) so you can use a lower nominal battery voltage. The intial cost for lead is cheaper but that doesn't add up if the OP wants to use it regularly.

Is that worded correctly? Instead of depth of discharge, did you mean wear level/remaining capacity?

Otherwise, spot on.

[Gats]

Honda eu20i > all ...they are brilliant

unless you're doing this as an exercise in recycling, a generator will be easier and more reliable IMO

[irsa76]

We had a Honda generator like that running NON STOP for four days on less than a single 20l drum of fuel. They are almost silent and awesome.

had my coffee machine and a full sized fridge plus everybodies phone/ laptop/ battery chargers.

This. There is a reason why backup generators are still used for backup power. They are a hell of a lot simpler really then messing around with batteries. Get a big enough one and you wouldn't even notice your not on the grid.

[Rdyno]

Get a big enough one and you wouldn't even notice your not on the grid.

Like this?

[Benonymous]

The other factor with hybrid car batteries is the way that the car manages them. They are closely moitored by the cars systems so that they neither over charge or discharge too deeply. This is how the packs in the Prius last so long. Without this management NiMh, LiFePo4 and other modern chemistries will be permanently damaged. Flooded cells, by contrast, have much better tolerance when it comes to charge and discharge cycles being handled crudely. Gel cells have a little less tolerance but are still relatively hardy.

Dunno, but for your application I can't help thinking a little gen set would be most efficient. Even a stored solar system will have ongoing maintenance/ monitoring issues inasmuch as if you ignore it, it might not be fully functional when you need it. In addition to this, as you say, a run of overcast weather might prevent it recharging enough when it's needed.

With a gen set, you just need to keep the fuel up to it and you're good as gold, plus you're running all your 240V stuff as well as your transformer/step down equipment. Win win.

[Karnage]

We had a Honda generator like that running NON STOP for four days on less than a single 20l drum of fuel. They are almost silent and awesome.

had my coffee machine and a full sized fridge plus everybodies phone/ laptop/ battery chargers.

Must be EFI?

PS Don't try and drag logic into this, we are talking about a setup for maybe 2-3 days every couple of years, needs to be over engineered to the max.

[darwinschops]

We had a Honda generator like that running NON STOP for four days on less than a single 20l drum of fuel. They are almost silent and awesome.

had my coffee machine and a full sized fridge plus everybodies phone/ laptop/ battery chargers.

Honda eu20i > all ...they are brilliant

unless you're doing this as an exercise in recycling, a generator will be easier and more reliable IMO

Is what I was thinking really... The idea of a noisy fume spilling 8h duration generator's not quite the case really. Some of the newer ones I've seen mates run are surprisingly efficient, quiet and only seem about a fuckload% easier than persisting with a clever but difficult solution.

[mondo2000]

Is that worded correctly? Instead of depth of discharge, did you mean wear level/remaining capacity?

Otherwise, spot on.

Yes, I worded that correctly. 100% depth of discharge means the battery is totally flat (and most batteries will suffer some sort of damage if they are totally flattened.)
If you take more than 50% of the energy out of a fully charged lead battery, you are causing permanent damage to it (sulfation) and it's performance and life will be reduced (to much less than 300 cycles). This is why Century brand deep cycle batteries only come with 6 months warranty, whereas their regular car batteries come with 12, 24, or 36 month warranties. They know people will drain their deep cycle batteries dead flat and fuck them in short order.

Lithium cells are better, they can be run 70 or 80% flat without suffering undue damage. In other words you can get more of their rated capacity out. Of course they still don't last forever and performance does gradually decrease. The remaining capacity on the lithium cells that have been flattened 80% 3000 times (or 70% 5000 times), will be approx. 90% of the original or nominal capacity.