What size battery?

[hargreavesn]

I have a Viva 700 yacht with a Propex gas heater, LED cabin lights, incandescent nav lights and water pump. The engine is a Tohatsu 9.8Hp 2stroke with electric start. There is also a 20W solar panel and no shore power. The current battery is 75Ah leisure battery which will only start the heater if the engine is running. What capacity, type of battery (leisure or starting, etc) would be best to fit so that the heater can be run without having to run the engine all the time the heater is required?

 

[VicS]

I have a Viva 700 yacht with a Propex gas heater, LED cabin lights, incandescent nav lights and water pump. The engine is a Tohatsu 9.8Hp 2stroke with electric start. There is also a 20W solar panel and no shore power. The current battery is 75Ah leisure battery which will only start the heater if the engine is running. What capacity, type of battery (leisure or starting, etc) would be best to fit so that the heater can be run without having to run the engine all the time the heater is required?

A belated welcome !

You dont say exactly what model heater you have but I am surprised that a 75Ah leisure battery will not start and run it unaided.

Leisure batteries are similar to engine start batteries and are usually capable of breifly supplying a current high enough to start an engine. A cold cranking amps figure is quoted for many of them. A leisure battery is more capable of supplying a small current ( ie a few amps for accessories like your heater or your nav lights) for longish periods than an engine starter battery so for you is a sensible choice.

Check the specs, and the installation and operating instructions for your heater. They may recommend an minimum size of battery. I'd expect them to state the starting current as well as the running current. They may recommend a wiring size.

You should check that your battery is charged and is being properly recharged by your solar panel and outboard
Outboard engine electrical outputs are usually pretty pathetic unless the engine is running at a good speed and for fairly long periods though.
You solar panel may not be giving you as much power as you think. The tech specs should give you some idea of a typical Ah output per day .. but that may be a summertime figure.

Check that the wiring is adequately sized, both for charging circuits and supply circuits to carry the expected currents without excessive volts drop.
Check all connections of course, not forgetting the negative ones.

Make an estimate of your power consumption in Ah per 24 hours and be sure your charging arrangements will supply that plus a bit extra.
Also be sure that your power consumption will not use more than half of the battery capacity before it is recharged.

Properly installed, wired and charged I'd expect your 75 Ah battery to be more than adequate but check all the specs and do the arithmetic.


Any way perhaps this has bumped your post back up to the top of the pile where others can see it.

I think you may have fallen foul of the system under which the first few posts made by newbies do not appear until they have been approved by admin..... the result is that by the time they do appear they are so far down the pile that nobody sees them.

 

[Lodesman77]

I have a propex, and it is reluctant to start if the voltage is too low. I checked this with propex and they claimed it should work down to 10.5V but that is at the unit, and mine wouldn't start with 11.7V at the battery. I checked all the connections and upgraded the wiring to mine and that improved things significantly.

At this time of year my 36W solar panel won't put much charge into the battery and your outboard probably won't be great either, so if in doubt take it home and give it a full charge. Probably best to check over a few days that it holds it, could also be the battery is on the way out...

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