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Auto batteries make terrible UPS cells. They're designed to survive very shallow cycling at very high currents, whereas the cells in your UPS will be very deep

by hapless 17y ago

Auto batteries make terrible UPS cells. They're designed to survive very shallow cycling at very high currents, whereas the cells in your UPS will be very deeply cycled at very low currents. I don't know about the marine batteries he's using. I expect they're still designed for high current output, which is a needless cost. You will probably be better-served to find a local supplier that specializes in battery supply, not an auto parts warehouse or a costco. Big lead-acids can be pretty cheap, if you don't buy them from UPS vendors. Secondly, don't use a consumer piece of trash as your "scrap" unit. Large, commercial-grade UPSes are cheap as dirt on eBay, because their batteries are invariably shot. Just persuade the seller not to mail you the batteries and shipping becomes reasonable.

tricky 17y ago
Wow. You admit you don't know anything about marine batteries and then you go on about how horrible of an idea this is? Do some research before you pull the trigger there, tiger. Marine batteries work well in this application. I've been using them for years.
- hapless 17y ago
  I just noticed the "Costco" label on his batteries, and that raised my suspicion. For me, specialized suppliers have been cheaper for this purpose. The important bit in my comment is unfortunately in the second part: Don't use consumer trash when you can get the really good equipment for cheap.
KC8ZKF 17y ago
Marine batteries are deep-cycle batteries, and are good batteries for this use.
wglb 17y ago
Er, deep discharge marine batteries are exactly the thing to use. They are designed to withstand repeated deep discharge, hence their name. Their current output, measured on an instantaneous basis, which is how "starting current" is measured, is often less than an auto battery. Auto batteries purpose is to work very hard for about 12 seconds.
jws 17y ago
There is a trio of people claiming marine batteries are good for this use. It would be unfair to reply to just one. Marine batteries are fine for this use. A typical marine battery might be good for 350 cycles. That should be more than enough for a UPS. (It isn't clear from the battery literature what they consider a "complete cycle", it seems like a high number for a full discharge, but even if overstated it is still plenty for a UPS). Marine batteries do have a higher cost per stored energy compared to deep cycle batteries. I don't know if that is from the higher available discharge rate or having the word "marine" in front of them. Renewable energy folks shun marine batteries because the real deep cycle batteries are good for 3000+ cycles, but you just don't need that for a UPS.
Kadin 17y ago
Most "marine" batteries are sort of a hybrid starting and deep-cycle battery. I think they're essentially a starting battery with thicker plates. They're built that way because, on a boat, you need a lot of current to start the engines but you also use the batteries as your sole 'housekeeping' power source from time to time (particularly on sailboats when the engine isn't running). Real deep-cycle batteries would be better, but they're more expensive. Something like this http://www.usbattery.com/usb_solar_p1.html http://www.usbattery.com/usb_solar_p1.html would probably be optimal; it's designed for use in alternative energy systems where you charge during the day from solar cells and then discharge during the night. Very heavy plates. A cheaper alternative, which I've seen some people use in UPS systems, are wheelchair or golf cart batteries. Both of them are true deep-cycle designs, made for sustained loads.

by hapless 17y ago

tricky 17y ago

Wow. You admit you don't know anything about marine batteries and then you go on about how horrible of an idea this is? Do some research before you pull the trigger there, tiger. Marine batteries work well in this application. I've been using them for years.

hapless 17y ago
I just noticed the "Costco" label on his batteries, and that raised my suspicion. For me, specialized suppliers have been cheaper for this purpose. The important bit in my comment is unfortunately in the second part: Don't use consumer trash when you can get the really good equipment for cheap.

KC8ZKF 17y ago

Marine batteries are deep-cycle batteries, and are good batteries for this use.

wglb 17y ago

Er, deep discharge marine batteries are exactly the thing to use. They are designed to withstand repeated deep discharge, hence their name. Their current output, measured on an instantaneous basis, which is how "starting current" is measured, is often less than an auto battery. Auto batteries purpose is to work very hard for about 12 seconds.

jws 17y ago

There is a trio of people claiming marine batteries are good for this use. It would be unfair to reply to just one. Marine batteries are fine for this use. A typical marine battery might be good for 350 cycles. That should be more than enough for a UPS. (It isn't clear from the battery literature what they consider a "complete cycle", it seems like a high number for a full discharge, but even if overstated it is still plenty for a UPS). Marine batteries do have a higher cost per stored energy compared to deep cycle batteries. I don't know if that is from the higher available discharge rate or having the word "marine" in front of them. Renewable energy folks shun marine batteries because the real deep cycle batteries are good for 3000+ cycles, but you just don't need that for a UPS.

Kadin 17y ago

Most "marine" batteries are sort of a hybrid starting and deep-cycle battery. I think they're essentially a starting battery with thicker plates. They're built that way because, on a boat, you need a lot of current to start the engines but you also use the batteries as your sole 'housekeeping' power source from time to time (particularly on sailboats when the engine isn't running). Real deep-cycle batteries would be better, but they're more expensive. Something like this http://www.usbattery.com/usb_solar_p1.html http://www.usbattery.com/usb_solar_p1.html would probably be optimal; it's designed for use in alternative energy systems where you charge during the day from solar cells and then discharge during the night. Very heavy plates. A cheaper alternative, which I've seen some people use in UPS systems, are wheelchair or golf cart batteries. Both of them are true deep-cycle designs, made for sustained loads.