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New battery bank size, charging mods... AGM or Carbon Foam

Feb 6, 1998
11,234
Canadian Sailcraft 36T Casco Bay, ME
Thanks to everyone for all the great advice. New system is up and running and we love it. 3 x Firefly G31 with a Rolls GR24 Reserve in the settee. Linked with an ACR. Balmar Sg200 monitor and Victron MPPT solar charge controller with smart link battery temp feedback. Perfect for us as we don't have shore power. After a lot of though decided to stay with the original 1-2-both switch for ease of wiring, using only the #1 position. 2 is available if needed. both is marked inop. Its great!
Please be very careful or you can ruin your Firefly's, if you continue taking them to 14.71V as shown in image 3.. I am guessing the 22C, in image #2, is the battery temp?

If this is so, it does not warrant compensating the battery voltage to 14.71V. Be sure your controllers/chargers/regulators have the correct mV per degree C compensation slope programed into them. It should be 4mV per cell, per degree C change, or 24mV, per 12V battery, per degree C change. 14.4V is the maximum voltage for absorption @ 25C/77F.

Also while the interconnects are neat and tidy a small arc in the jumpers relieves the strain on the terminals, especially when they are not restrained. They also like a bit of air space between them, unless you are always in cooler waters, but they do heat up if charging them correctly.
 
May 6, 2019
23
Catalina 310 0063 Nepean Sailing Club, Ottawa
Please be very careful or you can ruin your Firefly's, if you continue taking them to 14.71V as shown in image 3.. I am guessing the 22C, in image #2, is the battery temp?

If this is so, it does not warrant compensating the battery voltage to 14.71V. Be sure your controllers/chargers/regulators have the correct mV per degree C compensation slope programed into them. It should be 4mV per cell, per degree C change, or 24mV, per 12V battery, per degree C change. 14.4V is the maximum voltage for absorption @ 25C/77F.

Also while the interconnects are neat and tidy a small arc in the jumpers relieves the strain on the terminals, especially when they are not restrained. They also like a bit of air space between them, unless you are always in cooler waters, but they do heat up if charging them correctly.
Thanks for the insight. I’m not sure why the Balmar would show 14.71 and the victron would show a different voltage. The Balmar is set to the default carbon foam setting and the victron controller was set with the charge profile from the battery manufacturer 14.4v for absorption. All I can think of is that this picture was taken right after I got the app working. Maybe a setting changed. I have had difficulty updating the Balmar firmware because both the shunt and the display are on the same network and the software won’t allow Updates when they are both powered. Point taken about the arc and spacing. I didn’t do the installation. The batteries will be secured for the final version. Thanks!
 
May 6, 2019
23
Catalina 310 0063 Nepean Sailing Club, Ottawa
I was back at the boat today and confirmed with the meter that the voltage on the solar controller is accurate and the batteries are good. For some reason the Balmar gauge is displaying almost 1.5 V high. I’ve sent the info off to Balmar and they are looking in to it. When I measure the voltage across the shunt it agrees with the solar controller as well. Hmmm
 
Last edited:
May 6, 2019
23
Catalina 310 0063 Nepean Sailing Club, Ottawa
Just an update. Balmar Rep advises it is a known issue that will be resolved with a firmware fix for the shunt in a couple of weeks. Excellent customer service.