Onan Generator Cranking Amps

So here is the information CA Traveler was looking for.

I used a Snap-on analyzer specifically designed to measure amperage while a starter is operating.

As shown in the picture below, my generator (Onan 10 KW QuietDeisel) has a dedicated battery that is only used to start the generator.

• The 12V+ lead is 4/0 wire 72" long. The ground wire is 48" connected to the frame.
• At the start of the test, the battery was fully charged @ 12.7 Volts.
• Outside temperature was 15 C.
• During the prestart step the generator drew 6.0 Amps, with very little voltage drop off.
• When the starter cranked, the amps peaked at 207 Amps, then settled at 197 Amps until the generator fired.
• The battery supply voltage (at the terminals) dropped from 12.6 Volts to 10.8 Volts.
• Immediately after starting, the battery recovered to 12.3 Volts.

As you may have guessed, I am a proponent of using a dedicated battery for the generator. As per a previous post, I found that even when I cleaned all my terminals from the house batteries to the generator, the generator just did not start reliably. After installing the dedicated battery, I have never had a problem. IMO...

1. Due to the high current draw, 30 - 40 feet of 4/0 cable just has too much voltage loss.
2. The house batteries are deep cycle batteries. Therefore, they are not designed to supply the 200 Amps necessary without pulling down the battery voltage significantly.
3. When you really need to start the generator (i.e. In the morning when you house batteries are at 50% - 12.0V --or-- during cold weather) that is also the time when you have the lowest voltage available and cannot handle further voltage drop as the starter cranks.