Nothing but lithium for shedding

leon.davibe

Expert Member
Joined
Feb 3, 2009
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If needing a battery for backup power

Buy a lithium or stay without power really

to have a lead acid bank that lasts 3 years you have to buy 4x the lithium rating, ie you have to buy 4x100ah batteries for every 100ah lithium, and then you will most likely still throw them away after a few years

If you skimp and just buy the rule of thumb double lithium size and you use that capacity every cycle

Get ready for regular battery buying

Now yes i get there are pricey deep cycles that promise more cycles

The problem is still cycles promised on deep cycle and lithium aren't created equal

And as you get closer and closer to lithium cost it just gets harder and harder to justify buying lead acid batteries

ie lead acid cycles means you will get x cycles and be left with a doorstop

While lithium the cycles promised means after that you will have 80% of capacity still usable

ie your 5KWH battery will now be a 4KWH battery


not even taken peukert losses into account on lead acid ,seems load below 500w you should be fine to get what you planned for

If more the bank of lead acids has to get bigger
 

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i read a article from a manufacturer a while ago ,they say 800 amp of batteries for every 1 kw of inverter .for lead acid deep cycle antimony batteries .but also something else they touched on was that a lot of inverters overcharge deep cycle batteries shortening the life drastically .they recommended 280 ah batteries as a minimum per battery .
 
i read a article from a manufacturer a while ago ,they say 800 amp of batteries for every 1 kw of inverter .for lead acid deep cycle antimony batteries .but also something else they touched on was that a lot of inverters overcharge deep cycle batteries shortening the life drastically .
That would be an awful lot of batteries!
 
i read a article from a manufacturer a while ago ,they say 800 amp of batteries for every 1 kw of inverter .for lead acid deep cycle antimony batteries .but also something else they touched on was that a lot of inverters overcharge deep cycle batteries shortening the life drastically .they recommended 280 ah batteries as a minimum per battery .
Yea kinda hard to overcharge if it takes ages to charge full

It makes sense if it is a 24v system as peukert to get 100% capacity you have to draw c/20

So 800/20=40a

So 24*40=960w

Edit : but that is if you want to draw 1kw
So if you only ever peak at 500w =400ah

Or 250w= 200ah
 
Yea kinda hard to overcharge if it takes ages to charge full

It makes sense if it is a 24v system as peukert to get 100% capacity you have to draw c/20

So 800/20=40a

So 24*40=960w

Edit : but that is if you want to draw 1kw
So if you only ever peak at 500w =400ah

Or 250w= 200ah
when you do the maths its not an incredible amount of battery power ,i think people underspec lead batts by plenty .,way too few amps ,and expect miracles from them .
 
Get what you can afford until you can afford to get something better.
Yea i did a phased approach
Naturally not intending the next phase

phase
1 PC ups + whatever 7ah batteries i had *6

2:same ups 4 lifep04 cells

3 bought 4 more cells +1440wmecer

4 bought 2nd hand synerji 5000w and 7 more cells
 
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Knew about peukert but never actually made the effort to google and see the actual specs , if you need to spec it correctly you can't pull that amount of loads

Especially 5kw inverters

If you have to only do 0.05c to get full capacity that would mean
80 batteries to do 5000w naturally you would accept the loss on short peaks and just aim to get perfect peukert on base load at least

Ie i would need 400ah capacity ie 16 lead acid batteries

That is why the old solar batteries was these massive acid bowls
 
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