Planning the Ideal battery Mix

Circadian: There is a choice of Circadian 80, 160 and 200Wh batteries. Making the right choice for your application impacts the long term reliability of your operation and satisfaction of your staff. Since you ideally want to avoid Swapping Batteries during shift for at least 3 years, we recommend the following based on your cart load. The cart load is the power required by the Monitor, the PC or laptop and any accessories now or planned in the near future. This figure is key and really difficult to assess, best is to err on the high side!

Example - Let’s assume:

Cart Load is 40W and a Nurse Shift is 8 hours = 320Wh requirement per shift.

But the Cart is not in use full time. Assume 60% usage = 192W requirement

But the Circadian battery might decline to near 80% over 3 years.

That’s a factor 1.25 which you should plan for:   192Wh x 1.25 = 240Wh


Thus the requirement is 240Wh Circadian battery power on the Cart and also on the Charger to run the Cart 24-7 for 3 years without the need to Swap batteries during shift.

  • 4 Circadian 80 batteries are not sufficient
  • 4 Circadian 160 batteries: 320Wh on cart: 320Wh on charger are perfect
  • 4 Circadian 200 batteries will do the job, but are overkill.


NB: if you use an inverter (DC:AC:DC)  rather than a DC:DC options you need to assume a minimal additional 25% loss of Battery capacity since power efficiency is lost on both the up and down conversion. Then the 240Wh needs to be multiplied by a factor of 1.33

240 x 1.33 = a 320Wh requirement. Again the Circadian 160 achieves this, but it is a tight margin.

If the load, usage or shift times were to increase extra batteries or the 200Wh Circadian batteries would be required.


ProDurance: the capacity choice is 200, 400, 600 or 800Wh. Similar planning as above is required. Clearly there is no option to Hot swap, but in facilities where plugging in to charge during downtime or over night are acceptable, these phases can be calculated. Some thought needs to be given to the Power supply. The standard GSM 220 and a 500W inbuilt Power supply are options. Each ProDurance module needs 50W when charging. If 3 are used that is 150W, leaving only 70W for the application when using a GSM 220. This is too tight and the 500W alternative should be used.



What do you need to know?


For you

Estimated real Cart Load in Watt



Nurse Shift in hours



Estimate Cart Usage in Percent



Factor in Aging - based on warranty %/years



Factor in Inverter



WATT HOUR requirement on Cart



WATT HOUR requirement on Charger