How to decide with Smartshunt to choose, 300 amp or 500 amp? 37 foot boat with three batteries, one for generator, one for house, one starter for 2 engines.
How much power do you need in your system?
Power / system voltage = current
Less than 300A → 300A shunt
More than 300A → 500A shunt
Thank you, yes that makes sense but perhaps I should have been more specific, how do I determine how much amperage in my system
As I wrote, it depends on how much power you need in your system.
You need to know how much power every device in your system needs.
Total power divided by battery voltage = current (+ 20% as reserve)
Or you calculate it the other way around.
300A x battery voltage = max. power
e.g. 300A x 12V = 3600W
What purpose do you intend for the shunt? I presume it is for monitoring the house battery?
What equipment operates from the house battery? Voltage and capacity of the house battery would also help.
I found that in the UK last week the 300A model was unobtanium and you had to get the 500A anyway. I hadn’t realised the 500A modal has M10 bolts instead of M8, so had to scrabble around for some suitably-massive crimps. Otherwise they seem nearly identical.
For accuracy, I read somewhere that the loads should not exceed 66% of the shunt capacity. ie 300A - 198. Is this true???
In my situation I have the following
Xantrex 2000W Inverter/Charger - 80A
Victron 100/50 MPPT - 50A
Victron 75/15 MPPT - 15A
6 AWG trailer wiring - 55A (guess)
Future DC/DC Charger - 25A - 40A
Total 240A
How does accuracy apply here with a 300A vs 500A
For clarity the inverter is a load, whereas the mppt is supplying power.
Shunt is rated for load or supply to the battery.
Example: if mppt’s is supplying 10a and inverter is drawimg 20a, the shunt will have 10a going through shunt.
Or if mppt’s are supplying zero, then 20a will be passing through shunt.
I do not include the Batt power to the MPPT Controller 100/50 = 50amp
Go with the 500 amp. Its hardly any more money and will allow for expandability in they future. I rarely use the 300. Its for very small systems.
I think it might be rather simple. Do you have an inverter on board? That will be the only thing which draws huge currents. All the other stuff on board, autopilot, navigation lights, freezer, heating, (navigation) lights are within the 5-10A range. So, if you have a huge inverter on board, capable of more than 2400 Watts, then go for the 500A version. Otherwise you can stick to the 300A version. But, it does not make a big difference at all I think, both are more or less equal pieces of equipment.
Edit: you wrote ‘three batteries’. You only can use the shunt for one battery. Most of time that’s the household/service battery. It makes no sense to monitor the starter battery.
I’m sorry, I should have started a new post for my shunt size question.
I kind of highjacked the original post, my apologies.
Thanks to all for contributing to my question when using a 2000W inverter as a main load.