i have a mikuni diesel heater and i am thinking of installing a 3rd battery to service the heater as we are concerned that like a fridge it is heavy on power.

we do not want to run the engine in a quiet spot on a cold september evening.

at the moment i have a 102AMH domestic battery but do not want to exhaust it by running the heater for two long.

Can anyone with experience of heating give me any advice.

thanks

charles clements

charles clements

Spartacus 285

---

I have a Mikuni heater on my 325. It has needed new glow plugs with increasing frequency and the expert advice has been to have it serviced (major decoke).

As far as I can ascertain, the big power draw is when the heater starts (when the glow plug is in use). After that, the power is needed only for the fuel pump and the air fan.

I suspect that the glow plug is in use for every start up if the thermostat is set low enough to require this.

Why not try running your engine for the heater start up, then relying on battery power?

Your question implies you have two batteries. So long as you have a reserve engine-starting battery, you can experiment as above. I'm assuming your arrangement charges both batteries once the engine is running.

Hope this works out.

Mike Lockwood

Lucky Devil

Parker 325/32

---

hi mike

thanks for your reply.

i am installing a 3rd battery [Optima Red Top ] just for the engine which will be isolated. I will now have 2 102aHR domestic batteries [ original batteries] so i will not be so concerned. but i will use my engine initially as you suggest.

regards

charles

charles clements

Spartacus 285

---

Hi Charles,

Where are you putting your dedicated engine battery?

I had considered doing the same, and had in mind the galley locker--alongside the engine and hence near the centre of the boat, so hopefully not affecting trim.

In passing I have Optima Blue batteries (X2) and found that they did not fully charge unless hooked up to shore power. However I read somewhere that the engine alternator needs to have a rated output of at least a third of the battery capacity. The standard Yanmar 1GM alternator is 30A, so that may be the reason why my batteries never seemed to charge properly.

The alternator on my new engine is 70A so I am hopeful this issue will resolve itself.

275/30 "Cascada"

---

We have a third battery on Bright Eyes(275) , it is an Automobile battery only for engine starting. It is located in the cockpit locker outboard of the two existing batteries. It is handy there as all the wiring is already in that vicinity. I note the comments on alternators with interest as we have been there and done that !

The energy to power the alternator is not free, a 70amp alternator will require about 2.5 hp allowing for inefficiencies etc. this is a lot to take out of a small engine and can completely mess up the low speed performance. The 30 amp alternator fitted to the 1GM10 should charge the betteries if they are in good condition, but will obviously take longer,however you will retain all the flexibility of the engine while it is charging and lifting the keel won't result in near stall conditions. If you find your batteries are not fully charging, its time to go hunting around with a meter, what is the voltage on the batteries when they are being charged ? Is there any current leakage when the system is idle etc. Old batteries do not hold charge so it is quite possible that the little alternator on the 1GM10 might not be able to keep up with the internal leakage of two 110 amp hour batteries in the worst case.

Jan

275/8

hi john

it may be different on the 285 but here the two original batteries lie on the starboard side in a plastic box under the saloon seat [ there is a locker under port side seat.

Just to starboard of these batteries is an empty space accessible by cutting out a window in the extended plastic cover. I made a battery box, glassed it in and lowered a Red Top Optima battery in .It just fits but only by drilling a depression in the under surface of covering ply sheet[ where the terminals protrude up ] which cushion rests on. An electrician carried out all the connections. I now have an isolated engine battery and two domestic batteries. In case of emergency there is a switch that enables domestic bank to be used for engine.

I have 60amp alternator/2YM15 Yanmar with adverc charging system which til now has charged the batteries well. Hope it will deal with the extra battery. time will tell.

regards

charles

charles clements

Spartacus 285

---