Generator Starting Issue

[JLR]

I need some advice on a new (2007) Kohler 20KW starting issue. Very odd situation. I was unable to start my 12.5 KW Onan without using a battery parallel switch which parallels my Onan battery and my Kohler battery. So, I replaced the Onan battery last week and now the Onan starts just fine. But, I was also unable to start the Kohler without using the parallel switch so I bought a new battery for the Kohler and installed it on Sunday. Well, despite the new battery, the Kohler will not start (only clicks like low voltage) unless I use the parallel switch. I guess there is a chance that the new battery that was put in for the Kohler just needs to be charged before it will start the Kohler on its own. When I check the boat next weekend, I will try and start the Kohler after leaving its new battery on charge for the week. If it is still too weak to start the Kohler unless the battery parallel switch is used, I have a problem either with the Kohler starter drawing too much amperage, or the wires loose at the starter or at the parallel switch or something like that. Any thoughts on what I should check next weekend? The Kohler has never before needed two 12V batteries to start it. The unit is just about new with less than 100 hours on it. By the way, this symptom first appeared after trying to recommission the generator after winter layup. Thanks.
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[Sonny]

start with the simple stuff - clean all the connections with a terminal cleaner and sandpaper and when reinstalling, make sure they are good n tight. the vast majority of electrical issues are solved by cleaning and/or tightening connections.

[JLR]

I know everything is fine on the battery end because I just installed a new battery. That leaves the starter (which has not been touched since decommisioning) and the parallel switch which has. Not to get too bogged down but could a loose wire on the parallel switch interrupt a clean connection to the battery? Thanks.

[Pascal]

i dont' see how the paralel switch could interfere with the starting circuit. what kind of switch / set up? is it a manual swtich or a solenoid? in any case all it's doing is connecting the batteries together, it shoudlnt' interfere.

try swapping the batteries, this way you will know if the new battery is good. never forget that new stands for Never Ever Worked. woudln't be the first time a new battery has a bad cell.

also check the votlage before cranking and during cranking to see what kind of drop you have.

[Boatsb]

Send us a quick wiring diagram. If the wire on the switch is the main feed it may not be getting good contact from the battery side and needs the other battery.

It should be wired directly from the battery to the starter and the parallel switch should not be in that circut. It should be parallel (hence the name)

[JLR]

I will check it out this weekend and advise. The actual parallel switch is mechanical. It is a red and green rotary switch selector and has a position of on (meaning parallel) and off meaning one battery only. That's it.

[Sonny]

while cranking, check voltage at the battery, and again while cranking at the starter. if there's a significant difference then you know there's an issue with connections somewhere or just a plain old bad wire. remember, the wire going into the terminal counts as a connection too and could be a source of resistance because moisture can hang out in there promote corrosion, but let's hope it's just a DOA battery.

[Genesis]

That rotary switch may be bad. It DOES happen.

Get out the meter as noted and look at voltages while cranking at the starter terminal and battery. If ok at the battery and low at the starter terminal start tracing backwards until you find the place where the voltage drops - good odds its at that rotary switch.

[JLR]

Thanks Karl. Checked it all yesterday. All connections tight but did not put the meter on it. The Kohler will start on one battery but only after she is warmed up. When cold, at 50 degrees, she will not start unless paralleled. Is there any magic to the size of the group 24 needed to start the 20 KW Kohler. She has always started fine on what appears to be just a standard cheap group 24.

[Genesis]

Naw; that's not that big of an engine; most gensets should start on a motorcycle battery.

You've got a high-resistance connection somewhere and since paralleling always works my money is on somewhere before the parallel switch (between the battery and that switch.) Time to get out the voltmeter.