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UPS battery upgrade

Any fundamental reasons why I can't use the guts of my Tripplite 800 UPS with a larger external battery?

JazzMan

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Reply to
JazzMan
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If the charging circuit is current limited, with voltage level used to switch from charging to maintenance, wouldn't the net result be that it takes longer to charge a larger battery? Also, I assume that the charging cycle generates less heat than the discharge mode, so presumably the additional time charging wouldn't present any problems. Would that be a good assumption?

As far as discharge, I guess the inverter heating is a function of load vs time, with the system designed to withstand its maximum output with the stock battery. I can retrofit a cooling fan quite easily.

The reason I'm considering this is because I already have a battery, it's about the size of a car battery but it came out of a whole office UPS system and is designed for UPS duty, and the battery just kicked the bucket in one of my Tripplites. I can't afford to buy a new proper size battery, but can kitbash something together that's ugly but functional.

JazzMan

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**********************************************************
Please reply to jsavage"at"airmail.net. 
Curse those darned bulk e-mailers!
**********************************************************
"Rats and roaches live by competition under the laws of
supply and demand. It is the privilege of human beings to
live under the laws of justice and mercy." - Wendell Berry
**********************************************************
Reply to
JazzMan

Because the power supply on the powergrid side may not handle the load to charge that much. A dirt hack would be to have relays to switch batteries in and out. So that powersupply never is overloaded.

Reply to
pbdelete

check the owners manual.

some UPSs can't handle running their charging circuit for a long enough time to charge a large external battery - the charger overheats and dies which ruins the UPS. Other UPSs can, typically the big expensive ones.

Bye. Jasen

Reply to
Jasen Betts

No. lead acid batteries are typically charged with constant voltage chargers, so the charger will see a larger load. _if_ there is current limiting in there that part will be working harder and it will get hotter...

the charging circuit uses separate parts from the discharging circuit. it depends how finely they cut the margins when they designed it...

it may be fine,or putting bigger heatsinks in the charger section may be all it takes.

Bye. Jasen

Reply to
Jasen Betts

that

P, the power dissipated as heat in the limiting part, is equal to the current, I, times the voltage across the limiting part. The equation is P=VI

V is the voltage across the limiter, equal to Vin, the constant voltage source, minus the battery voltage, which is the voltage specified to meet the requirements of the UPS, and therefore the same for the larger battery as for the original battery. I is the limited current, and is the same for both batteries. So P=VI will result in the same number for either battery. The limiting part won't work harder and won't get hotter - but it will take longer to charge the larger battery, as the OP presumed.

Ed

Reply to
ehsjr

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