battery question(s)

[NS30C Loon]

Ahoy! We removed our black water system and are installing an OGO composting toilet. The unit requires 12v power for a fan and an agitator. OGO recommends a deep cell battery (whatever that is!). Can I mount a small lead acid battery in a box in the head (ie below deck)? Or must it be vented outside? Inline fuse required? Other battery options? I worry about Li battery fire hazards.
Thank you!

[AlvyLad]

AFAIK composting toilets are designed to be used in camper-vans, whereas batteries range from connected 60AH to 100AH, and if separate 100-200AH. I'm certain connected to you boat system, they wouldn't make a dent on usage and power consumption (depending on amount of people are using)- rather minimal.
If you are adamant on separate system, it would need be connected to charge up occasionally from main power source, but having 60AH+ is feasible system to have to.
Most comon, cheap, "deep charge" batteries are Type 096 and if you was to get one at 100AH-120AH, you'd be safe for a very long time.
I'd get cheap battery monitor and charge it up, whenever it would drop to 12.2V, whilst in good condition they are meant to be about 13.4-14.4V state, charge is normally 15V- 30A-100A rate. (you'd have to have separate charge cables to it (Alternator-Battery), that are gianorourmous by any means in order to maintain them reasonably efficient) the further distance they are in between- the greater the loss of power, so anything over 6ft, you'll have unacceptable loss in power, generating heat in the cables... perhaps an "evil" you'll have to put up with. Longest I've seen (cheapest) charger connecting cables are portable "car crocodile set" of 10ft at about £30, it'll be double, if you try to find just the correct size copper cable alone (20ft- ~£60+), that makes the cost of decent battery Type 096 about 100AH- ~£80 irrelevant, if you place it any further distance away. Feed for the toilet-whatever wattage consumption/rating is recommended, but cheap and rather thin wire, need be checked-calculated in accordance to the peak load/consumption of the toilet

[NS30C Loon]

Thank you for the response. Embarrassingly, I do not understand most of what you wrote. Is there any way to restate simply? I clearly know absolutely nothing about electricity (12v or other).
Thank you

[AlvyLad]

https://www.ebay.co.uk/itm/131966471254
https://www.ebay.co.uk/itm/405154616000 cable needed (acceptable to charge normal car battery) see, the (cheapest option) thickness and length.

https://www.ebay.co.uk/itm/116456699325
https://www.ebay.co.uk/itm/277003812641
"Deep cycle"- is bit of con-word for supposedly more discharge capable, without degrading type.... not really different to none other car batteries, "thicker, more isolated from each other plates" means, they are slower to charge, less efficient.
beware of their weight!

Basically depending where your heads are, where, your engine (alternator) is, so the battery ideally need be placed closest possible to, not aft of the boat in order to avoid very expensive installation.

If none of it made sense to you so far, I'm doubtful you'll be able to install any of it yourself, let alone design it, for someone else to do the installation.
I'd recommend having a chat to mechanics at the nearest marina or even a car mechanic on how/what is it are you trying to achieve, simple connection to your existing power system apart.

[TomSR]

The fan on our composting head draws very little current, about 50 mA.
Mine uses a 100Ah LiFePO4 battery which is charged by a 50W solar panel.

Yes, you'll need to provide over-current protection for the fan wiring. In my case a small fuse block uses a 1A fuse for that circuit. My sailboat has no engine, so my electrical needs are small, this simple installation serves very well.

[NS30C Loon]

Since our boat has a 12-volt system, should we patch the toilet fan into the existing system? Or use a separate standalone battery? Thank you.

[Mike OReilly]

To answer your question properly requires that you tell us how big is your existing battery bank(s) is. But the likely answer is: yes, you can (and should) wire your new OGO head to the house battery bank.

I've been a long-time composting head user. Mine is a Nature's Head, which also uses a small venting fan. It draws so little power, it doesn't even register on my inline amp meter. I don't know what the OGO draws for the churner, but it can't be much.

A separate battery for the head would make your boat wiring needlessly complicated, in part because you then have to wire it to be recharged.

[NS30C Loon]

While we would love to connect the head to our current 12v system, we are on a mooring (so no shore power) and no solar charging. Probably just start with a LiFePO4 battery

[Mike OReilly]

I'm a bit confused... Do you have any batteries on board right now? I assume yes, but maybe not? If yes, how are you charging them? Engine alternator? Generator?

It really makes no sense to have a separate battery to run your new head. Wiring the OGO should be a very simple electrical job. Installing LiFePO4 batteries is a good idea, if you're redoing the house bank. But you have to match charging with use.

[pcmm]

Originally Posted by NS30C Loon

Since our boat has a 12-volt system, should we patch the toilet fan into the existing system? Or use a separate standalone battery? Thank you.

Yes, just connect it to your regular 12v system. Nothing special about the OGO power needs. I have 2 installed on my boat. The power draw is so minimal that the whole unit uses on average only 1-1.5Ah per day!

[NS30C Loon]

Mr. O'Reilly, thank you for the response You think YOU ARE confused...

As a disclaimer, and I will say this (over and over again!) I am not an electrical engineer, nor am I an electrician. My experience with electrical has been to plug in appliances and turn on light switches.

That said, the boat is new to us and I am still trying to learn the systems. There ARE batteries on board. We have one dedicated starting battery into house batteries. All are lead acid. On our previous sailboat, we recharged the batteries by running the engine. Our power demand was then and is now low.

I would like to add a dedicated battery for the OGO since the fan runs continuously and we are on a mooring with no charging capacity (ie solar).

[pcmm]

Originally Posted by NS30C Loon

Mr. O'Reilly, thank you for the response You think YOU ARE confused...

As a disclaimer, and I will say this (over and over again!) I am not an electrical engineer, nor am I an electrician. My experience with electrical has been to plug in appliances and turn on light switches.

That said, the boat is new to us and I am still trying to learn the systems. There ARE batteries on board. We have one dedicated starting battery into house batteries. All are lead acid. On our previous sailboat, we recharged the batteries by running the engine. Our power demand was then and is now low.

I would like to add a dedicated battery for the OGO since the fan runs continuously and we are on a mooring with no charging capacity (ie solar).

Better choice would be to add some solar to your system. A dedicated battery will require a charger even if its just a Dc-DC charger that leverages the existing bank. Adding some solar is only slightly more expensive that sourcing an additional battery and its DC-DC charger and is far more useful to you on the whole.

The OGO will only use a couple of Ah per day. your existing house bank should be able to handle that for a couple of weeks if its the only load running while you are away.

Best thing you can do is hire a professional based on your own professed complete lack of knowledge of anything electrical. At the very least find a boat neighbour that is knowledgeable and learn from them.

Mike was only trying to get the details from you (that you didn't provide and were important to answering the question) don't lash out at those trying to help you.

[Mike OReilly]

I get ya . When I first started with cruising boats I knew even less about electric systems than you. I made some incredibly amusing, and expensive, mistakes in those early years. I guess that's why I'm trying to help.

I strongly suggest you pick up a book on boat DC electricity. Something like Don Casey's Sailboat Electrics Simplified

https://www.nauticalmind.com/66635/s...cs-simplified/

You don't have to become an electrician, but you will do yourself a world good if you gain a basic understanding of your boat's DC system.

With regard to your OGO, as everyone has said, the power demands are minimal. It's very unlikely that you need to expand your battery capacity. But if you do, it's much better to expand your existing house bank, than to add in a third battery bank (Starter, House, OGO). The main reason has to do with recharging. All batteries have to be recharged at some point. If you add another battery bank, then you also need to wire this new battery to the alternator in some way, which makes this a lot more complicated. Either that or add a simple solar charger directly to the OGO battery, which again makes it more complicated.

(I see PCMM beat me to it ).

The simplest solution is to run your OGO wires to the existing house bank. Most boats will have a main positive (+) and negative (-) bus bar. Run the OGO positive (likely red) wire to the positive bus. Run the negative (likely black or yellow) to the negative bus. You should fuse the positive wire near the bus bar. I bet your OGO came with a nice inline fuse. If not, it's easy to install one.

There are many other ways to do this job. You could run it directly to a circuit box. You could run it through an on/off switch. But none of it is rocket science. Once you have a grasp of the basics, you'll see how logical DC electricity is.

[Adventure35]

No power needed if you use worms in the head.

[wgerstmyer]

The need for a fan for “composting” (actually “dedicating”) toilet is really rare. Have had several and eventually just didn’t install the vent pipe and fan at all. I get free, large bags of coffee chaff from the local bean roaster and sprinkle that on any poop. Perfect all by itself.
Or, go with air tight containers in your toilet like the Joolca Gotta Go unit. Lots cheaper and better features than the dedicating marine toilets.
These days I simply have a $50 pee diverter, pee portion piped to separate jug and I set the diverter on a 5-gallon or similar bucket for bagged poop collection. The pee container is fairly airtight but the bucket isn’t and there is no smell (other than an initial nice coffee smell) and no challenging routing of a vent tube.