Originally Posted by LinekinBayCD
Another great article by Main Sail.
I too have a Link 10. I would probably have more confidence in it if I followed the instructions and periodically re-synced it when I knew the battery banks are fully charged. Problem is I believe that batteries need to "settle" for a period in order to get an accurate read on their charged state. Usually, after a long motor, when I feel confident that the batteries are fully charged you start putting on the juice, radio lights, water pump, etc.
The SmartGuage seems to be a much simpler option. It looks like the SmartGuage can also operate a relay. I would like to be able to run my Espar heater without the concern of running down the house bank. I'm thinking it might be fairly easy to swap out the Link 10 for the SmartGuage given that it appears that Link has more lines run to the batteries and shunts than appears to be needed for the SmartGuage. Maybe some reconfiguration and elimination of unneeded wires.
I'm smart enough to know there is a lot I don't know but not smart enough to know what I don't know.
No need to get rid of the Link. Keep it and use it for monitoring current, charging or loads. Ignore the % charged and Ah screens and use the Smart Gauge for that...
For an Ah counter to be accurate for SOC is much harder than most folks are willing to work for...
At a bare minimum they need to know:
Bank capacity = ACTUAL not THEORETICAL (CWA)
Battery Temp = Or a known "ballpark"
Charge Efficiency = Can't even begin to be accurate without this. (CWA)
Peukert = If this is wrong there is no way it can even get close. (CWA)
*CWA= Changes With Age
On most boats auto-synch should simply be disabled and "known full re-sets used.
To properly use an Ah counter the bank should ideally be 20 hour capacity tested once per year. This can be done two ways:
Method #1 (at a battery temp of 75F - 80F):
Apply a load of C/20 to a FULLY CHARGED battery and start a stop watch. C/20 is the 20 hour Ah rating divided by 20. So a 125Ah battery would get a load of 6.25A for 20 hours before hitting 10.5V.
Connect a DVM to the battery terminals.
Adjust the load/current as voltage falls to maintain the C/20 rate as precisely as possible.
Monitor battery & load until terminal voltage hits 10.5V then hit the stop watch and record the hours & minutes.
Determine what % of the 20 hours it was able to deliver the 20 hour rate.
Replace the stop watch with an Ah counter such as the Victron BMV-600 and count the actual Ah's delivered before hitting 10.5V. What percentage of the rated Ah capacity did you get? Use this as your new Ah capacity and you will be much closer in accuracy. You can also use the Victron to drive a relay and cut the "load" at 10.5V.
*In both methods the "load" needs to remain as constant as possible and requires human intervention to keep it steady as the voltage decays.
*After any discharge capacity test you must immediately recharge the battery bank!
Or just use a Smart Gauge and let it do its thing...
The best readings for a Smart Gauge are in the am when there is no charging and the bank has been discharging all night.. You really don't need to know SOC more than once ever 24 hours....