KyleR wrote:QR_BBPOST ... I discovered when going through the systems. These batteries had a label that said "Remove this label when installed to monitor electrolyte level" (or something like that). The label had never been removed (i.e. no way to check level with label on) and the batteries had been installed in 2020. So again they were definitely neglected. Thankfully when I checked the level everything looked good - with no plates uncovered. ...
It's quite possible if there was absolutely no electrolyte lost in 3 years that those batteries might have never (or rarely) been fully recharged. This is very bad for lead-acid batteries. If you constantly only recharge to 90 or 95% you lose a lot of capacity over time. This is very different than, say, Lithium batteries which really LIKE not to be 100% charged.
Swing by a Harbor Freight and buy one of their digital volt meters. They're cheap ($12?) but they work just fine. Buy two and leave one at the house and one on the boat.
And those battery voltage charts are just general. The actual voltage depends a bit on the chemistry, as there's additives to the plates that can swing it up or down by a bit. And the charts really only apply to new or fresh batteries, not over their whole useful life. The voltages will gradually decrease a bit as the battery ages.
bud37 wrote:QR_BBPOST .... One fridge at 8 amp draw running for 15 minutes twice an hour would pull 16 amps for the 1/2 hour....8 amps for the hour....therefore 8ah......divide 105ah by 8ah = 13 hours of use. ...
Might want to double-check that math. If a fridge has an 8 Amp draw, then it would use 8AH for every hour it's running. If it's only running 50% of the time, then that would be about 4AH for every hour that passes. By that math, a bank capable of 105AH should be able to run that fridge 26 hrs. (just the fridge).
km1125 wrote:QR_BBPOST Might want to double-check that math. If a fridge has an 8 Amp draw, then it would use 8AH for every hour it's running. If it's only running 50% of the time, then that would be about 4AH for every hour that passes. By that math, a bank capable of 105AH should be able to run that fridge 26 hrs. (just the fridge).
Yup you are right, I don't know why I multiplied that by 2 first.......just not thinking straight I guess. Good catch....
It's quite possible if there was absolutely no electrolyte lost in 3 years that those batteries might have never (or rarely) been fully recharged. This is very bad for lead-acid batteries. If you constantly only recharge to 90 or 95% you lose a lot of capacity over time
When we bought the boat they had these deep cycle batteries connected to the main engines as start batteries - and the 1000CCA starting batteries connected in parallel to the house loads. So my thoughts are that these batteries probably never saw less than 95% since they were only used for cranking. Not sure if that is considered good or bad for deep cycle batteries. I swapped them when I realized the discrepancy.
Buy two and leave one at the house and one on the boat.
I do have two hand-held digital multimeter that I have been using for taking voltages when I'm troubleshooting - which are what I have been using during this process. However for day-to-day quick checks I just use the Carver installed analog gauge on the DC panel. Plus - our boat is our house!! We sold everything and moved aboard back in October! And in spite of all the craziness we LOVE IT!!
Thanks again for all the comments and feedback - and good catch on the math!
.it appears according to Deka those batteries are 105ah each ....so in parallel they will have 210ah. Considering that, 50% would be 105ah left........that will allow you to pull that much from them.
One fridge at 8 amp draw running for 15 minutes twice an hour would pull 8 amps for the 1/2 hour....4 amps for the hour....therefore 4ah......divide 105ah by 4ah = 26 hours of use
Thank you for taking the time to research the amp-hour ratings for those batteries! Something I've been meaning to do but never did - so I really appreciate effort!
I think my next purchase will be a clamp-on DC ammeter and start doing what has been suggested - going around load by load and seeing what's actually being drawn by each component/load. Probably not something I'll get to this week - but definitely on my short list! I've gotta keep that refrigerator running and cold!
Something to consider looking into and installing would be a battery monitor system.....something like a Victron BMV 700 series with a shunt....the shunt is important as it will allow you to track all your loads on the bank it is attached to, plus track battery temp and state of charge ( how the charger is performing ).
Victron is one , there are others, that is the one I have installed on a few boats and was quite pleased with it once wired correctly.
Or an easier installation like I did is a Victron smart shunt. No gauge to install, only the shunt, all info is sent to the app on your phone. In other words, your phone becomes the gauge. https://www.victronenergy.com/battery-m ... tery-shunt
Cheers, Hans
2007 Carver 41 CMY
Twin Volvo D6-370's
Montreal, Canada Midnight Sun I Photos
I swapped them when I realized the discrepancy. 
We sold everything and moved aboard back in October! And in spite of all the craziness we LOVE IT!! 
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