Battery voltage loss

[g36]

What is the victron showing in amps used? At any given time and also over the day or 24 period. Fridge only? What about interior lights, anchor light? Group 27 batteries aren't that steller for a house bank. From my memory group 27 has only apx 105 reserve amps, going with the only use 1/2 battery capacity to prolong battery life would be pretty low usesble house bank amps. Also what capacity did you setup on your victron for house battery capacity?

[pepmyster]

I remember setting it up with the total amp hours of all the batteries.

[Viper]

When you test the batteries in that bank, are you disconnecting each one before taking its reading? I'm getting the impression you're not. If you're not, you're not getting a true picture of the condition of each battery, which is important in determining that no one of them is sub par and bringing them all down with it.

[pepmyster]

I did test each one alone in the spring. All passed really well. I even re-did my cables in the back three. Re-thinking this as I write all this down, My mppt controller's charging output is connected to 2 main leads under the aft seat on the fly bridge. This connection is house due to the fact that when I disconnect the house main connection, no more power. BUT, what if that fly bridge connection goes to a battery isolator before getting to the batteries? I see my house bank getting charged with the solar. Maybe I should make the output of the mppt directly to the house bank?

[Midnightsun]

I am thinking more of total battery size is insufficient for your needs. Let me explain. Group 27 batteries are somewhere around 80AH capacity giving you 320ah total, take away 50% for usable and you end up with 160AH. The last 15% or so takes so long to put back in with lead acid its not worth counting when on the hook so take away another 25ah or so which now becomes a rather small usable bank. Not sure how old your batts are but if you have been draining below 50% for a season or so those batteries will end up needing replacement in a couple of years at best. Believe me, been there done that.

One of the main reasons I went with Lithium. We were away from shore power for 7 days and finally plugged in last night at a marina. Bank was still almost full mainly because a short time of generator mornings and evenings for cooking, charging and hot water puts the juice back in at over 100 amps. I have 525W of solar on the roof but this is not enough to sustain my usage. Reason for the marina was the heat expected and we wanted AC to sleep better.

[pepmyster]

Understood, but if the battery says 170ah, x 4 =680. This is going to make me lose my mind! Can't afford to go the lithium route. 340 watts of solar pumping 14 volts at 12 to 14 amps on a good have decent sunny day? Think I'm going to buy a kayak.....

[bud37]

Source of the post Understood, but if the battery says 170ah, x 4 =680

Reserve capacity is a measurement of time not Amp hours.......Ahr's is the battery capacity and measured as Hans has layed out.
Now that said, you have the tools to figure this out already IF you installed the Victron properly and have all your grounds in the right sequence with the shunt.

You should see power/charge in and draws out at all times on the monitor, easily monitor your fridge usage by watching the monitor and shut off all but the fridge and see what the draws are. That would apply to all your loads attached to that battery bank that the shunt/Victron monitor is attached to.

How many of these batteries are on that bank you are using for house?? Just 3 small grp27 could quite easily be the problem here as could be the fridge....lets face it it has been quite hot and humid lately taxing everything to the max....maybe you found the breaking point.

[pepmyster]

There are 4 x 27’s for the house. This is the only screen shot I have of the monitor at this time.

[Midnightsun]

Source of the post Understood, but if the battery says 170ah, x 4 =680. This is going to make me lose my mind! Can't afford to go the lithium route. 340 watts of solar pumping 14 volts at 12 to 14 amps on a good have decent sunny day? Think I'm going to buy a kayak.....

I believe the confusion is the AH vs Reserve in your case. Here is a typical group 27 deep cycle. The reserve is 175 however the AH rating is 80. I seriously doubt you will get 170AH from a group 27.

https://www.napacanada.com/en/p/CNB27RVS

[g36]

Lithium is not the only game in town. You can consider golf cart batteries as an option. I've been using this for going in 16 years in different boats I have had. Take a look at Trojan T105s or equivalent from batteries plus or costco or similar in you area. 6 volt batteries set up in series/parralel and will give you way better results than your current setup. Theyre rating is 215ah. You do need minimum of 2 being as they are 6volt, and then even numbers from then if you need more capacity. No need to change any of chargers solar mppt or anything. These types are made for capacity and reserve storage when used for a house bank. Set this up properly on your victron and you'll have years of useage from them if maintained properly.