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Old 18-02-2020, 02:50   #1
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About to change my house bank, please help!

I am no physics expert, I enjoy learning on the job and I feel I learnt a lot over the past weeks about batteries, charging schemes and types of use etc thanks to the many contributions on these topics on CF. I am about to change batteries and am facing some questions that I hope I can get advice on. Here is the context.

My service batteries (2xFLA) have started to loose strength down to a point where I had to choose between AP and fridge to keep voltage above 12v in day-long (over 10hrs) passages last summer. They are 7-8y old. During one winter (2y ago) I inadvertently left the boat (on the dry) with the shore power cable connected to the boat (but not to the grid) and service batteries went down to 3v, something that hit them a bit (reduced amps) but did not kill them though. I had so far no real clue of the need to ensure they were as close as full prior to leaving the boat for a week of 2 throughout the sailing season. Topping them up was my only routine I must confess.

I did quite a bit of reading on CF and elsewhere in order to assess the best way forward.

Boat is 37ft, central cockpit hence not much place for solar on deck, aft being covered by packed dinghy and access to platform and seats in the aft corners, the best place to sit when it gets sunny and not too bumpy. An arch would be the solution but since I’m only coastal sailing at the moment I consider this too much for now. Outside of the pushpit on each side could be a 2nd best. But for now all I need is to secure a day of passage with sometimes anchoring overnight (with possibility to run the engine if needed) with consumption of max. 120Ah (and up to 180Ah at anchor).

Current bank is composed of 2x 140Ah FLA batteries for service and 1x 70Ah maintenance-free lead acid for engine. Condition of the latter looks great with 13.1v 2 months after haul-out. Service bank is currently around 12.6v but rapidly goes to 12.4v under load and lower when running the Ebenspächer heater or else. Service also supplies bow thruster (580A) and windlass (Lofrans, 800 or 1000w? not sure).

Last WE I went to the boat again and tested the charger with the various options for battery types. The model is a smart charger Hitec from Tecsup 12v/25A yet is 20y old. To my half-surprise, boost voltage was lower than the specs in the manual for each of the options. This convinced me to not only buy a new set of batteries but also a new charger. The type would be Victron 12v/50A smart charger (smart as in smartphone, it allows connecting with Bluetooth, a cool feature to better understand what is going on), it will work well with the newly acquired BM (BMV712) that will measure SoC and consumption. Its shunt is rated 500A.

After much reading and also given the room available in the battery box, I am considering to put 4x T-105 that will provide 450Ah. This larger bank will avoid going too deep on DoD. However I was wondering about the following points:

- is T105 ok to operate the windlass and the bow thruster? Engine is always running when using any of them, yet not sure if they would be too hard on the batteries?

- does the shunt power (500A) allow for the peak consumption from either bow thruster (580A is quoted, which I suspect would grill the shunt) or windlass, whatever the highest - or should I separate these from the shunt that will be coupled to the service bank?

- the charger comes in 2 versions: with 2 or 3 separate outputs. If the answer to the first point is that windlass/bow propeller should not draw from the T105 , then either I opt for the 3-output model and place or try and find another type of battery. If from the secont point, then 3-output mode with a separate start battery would be the solution?

- would installing solar in the future influence any of these elements?

I very much appreciate any input on these!
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Old 18-02-2020, 04:52   #2
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Re: About to change my house bank, please help!

What are the make/model of windlass and bow thruster? What is the distance of wire run from batter bank to each?

I assume you have been operating both from your existing bank? If so, there is nothing specific about a T105 which would prevent it from providing similar performance in that application.
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Old 18-02-2020, 05:14   #3
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Re: About to change my house bank, please help!

The T-105 is an excellent choice and will be fine.
You can exceed the capacity of a shunt by a wide margin for short times, I do not know the time time limit or by how much, but believe 580 on a 500 amps shunt will be fine.

If the batteries will fit I think you will be fine.

Gord answered the short duration surge in this thread
https://www.cruisersforum.com/forums...-200734-2.html
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Old 18-02-2020, 14:56   #4
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Re: About to change my house bank, please help!

Quote:
Originally Posted by belizesailor View Post
What are the make/model of windlass and bow thruster? What is the distance of wire run from batter bank to each?

I assume you have been operating both from your existing bank? If so, there is nothing specific about a T105 which would prevent it from providing similar performance in that application.


Thanks. The bow thruster is from Vetus, the 80kgf type and the windlass is from Lofrans. I am not sure of the model, looking up current model it is similar to the X series so I suspect 1000w or perhaps 1500w max. Both original equipment, boat was built in 2000. Najad at the time was known for oversizing their equipments.

Battery bank is located under the aft cabin berth behind the engine room, so cables are approx 10m long, pretty thick.

Indeed these were operated from the existing bank without a problem, I could not find details on max draw from the T-105 technical sheet.

I am more concerned about the shunt size, I sent a mail after your and a64’s replies to Victron to confirm the tolerance.

On my last question, I would guess future solar panels do not require separate bank hence a 2-output model would fit the need, engine and service as I have now?

Many thanks for your quick replies, much appreciated!
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Old 18-02-2020, 16:50   #5
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Re: About to change my house bank, please help!

Wow, thats a long run for 1500W, but its been working. I would take this opportunity to rerun the numbers on that circuit, confirm its properly fused where it should be, properly supported, and in good shape...a big cable short is a serious fire risk.

Solar uses its own separate controller which outputs directly to bank to be charged (normally house) and is completely independent of the battery charger so number of outputs on charger doesnt matter.
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Old 19-02-2020, 05:34   #6
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Re: About to change my house bank, please help!

Quote:
Originally Posted by a64pilot View Post
The T-105 is an excellent choice and will be fine.
You can exceed the capacity of a shunt by a wide margin for short times, I do not know the time time limit or by how much, but believe 580 on a 500 amps shunt will be fine.

If the batteries will fit I think you will be fine.

Gord answered the short duration surge in this thread
https://www.cruisersforum.com/forums...-200734-2.html


Many thanks a64. Just got the reply from Victron now, they must have a lawyer as commercial manager as he recommended to go for the 1000A 50mv shunt in my particular situation this is in contrast to what Gord mentioned in your link. His conservative (or commercial!) view makes me go for it, it is the quality of the shunt that made me discard the China-made shunt that I got earlier through a relative.
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Old 19-02-2020, 05:46   #7
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Re: About to change my house bank, please help!

For the OP, if your old system of 2-140ah fla batteries were working and new system of 4-T105s will work just fine (i have been using that for years)
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Old 19-02-2020, 14:07   #8
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Re: About to change my house bank, please help!

We changed a year ago to T-105s in two banks of four each. No problems.
Two suggestions
1) order the batteries with the taller battery posts. The standard posts are too short and will not accomodate cabling for temp sensors etc or even your main cable on top of the interconnect cables between the batteries. Didn't cost anymore but were special order as the standard battery posts are normaly all my dealer stocked.
2) Order the hydro system they sell to water the batteries. Takes no time to water so much more likely to get done. They don't claim it as a feature but with the hydro caps and system installed I think it eliminates acid spill on any reasonable angle of heal.
Tom
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Old 19-02-2020, 15:10   #9
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Re: About to change my house bank, please help!

Quote:
Originally Posted by tml View Post
We changed a year ago to T-105s in two banks of four each. No problems.
Two suggestions
1) order the batteries with the taller battery posts. The standard posts are too short and will not accomodate cabling for temp sensors etc or even your main cable on top of the interconnect cables between the batteries. Didn't cost anymore but were special order as the standard battery posts are normaly all my dealer stocked.
2) Order the hydro system they sell to water the batteries. Takes no time to water so much more likely to get done. They don't claim it as a feature but with the hydro caps and system installed I think it eliminates acid spill on any reasonable angle of heal.
Tom
Quebramar,

These ^^ are excellent suggestions from TML.

We have 8 T-105 batteries in our 12V DC house bank. [Since mid 2014, full time cruising. Still going strong...] They handle everything you describe very well.

The Trojan Hydrolink watering system is very worthwhile. Their 'Clampless' tubing version best suited our needs.

Our charging sources include a Balmar 614 regulated 110A alternator, 125A 12V DC shore power/generator charger, 460W of solar panels, and a wind generator.

We try to equalize the bank [per Trojan specs: 16.2V DC - temperature compensated @ 4 hours max] every 3-4 weeks since that bank is in a PSOC condition much of the time.

If you are interested, there are photos and additional details and reference links about our battery replacement on this page. [We just swapped out batteries and left everything else the same as done by the PO of the boat since it was very adequate, if not somewhat untidy...]

Best wishes with your project.

Cheers! Bill
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Old 19-02-2020, 15:26   #10
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Re: About to change my house bank, please help!

If you can switch to 2 x 6v batteries instead of 4 x12v you will likely get about twice the service life. Also would be good at the next upgrade to switch the engine batteries to an FLA. Mixing sealed and flooded means you will undercharge one or over harge the other. Final point is if it is possible to have a batt forward to run the windlass it will work better as you will be loosing volts on the cable however big it is.
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Old 20-02-2020, 08:16   #11
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Re: About to change my house bank, please help!

John Mardall,here- retired from Vetus but still answering service questions. Our most common installation for an electric bow thruster and windlass is a dedicated AGM battery, located as close as possible to the user devices, with a single power switch (relay or manual) with a fused connection to each device. For the BOW80, which is quite an old model but still very good with proper maintenance, a battery capacity of at least 140 AH is recommended. That battery will also be adequate for the windlass loads. Please feel free to contact me direct at jmardall@comcast.net for more information or discussion. If you don't have it, I can probably find the original owner's manual for the BOW8012 thruster.
All the best
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Old 25-02-2020, 10:49   #12
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Re: About to change my house bank, please help!

Thanks much for all your input! Great advice and I see more clearly the way to go.
Special thanks to you John, sent you a separate mail to your address.
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