Testing batteries?

[DaveFL]

PO must have changed wiring as AS schematics show chassis battery as primary in the generator start system. Finally figured out mine is on the house batteries.
I was not able to start my generator, whirl and click, so I used the auxiliary button on the dash, immediate start. Must be battery so I check voltage on start and house 12.6 combined on two deep cycle in system, tested at the gen positive post and it showed same. Opened batteries and found one cell with hydrometer was fair rest were top of good reading. Tried charging for few days still same readings, decided by age they needed replacing anyway and it solved problem. I did load test it with an inverter but only used a 75 watt bulb and it kept it lit, and the inverters built in meter showed a good battery.

Anybody know what the cca load requirements the Onan 5500 needs to start?

[daveswenson]

From the FWIW file.

https://www.youtube.com/watch?v=G0odjtntH3I

There's a lot of stuff on the internet about reviving sulfated batteries with Epsom Salts.

[masseyfarm]

This site has some good general information on it Dave.

They also include this information.
Batteries

• top surfaces clean and dry
• acid (electrolyte) level up to plastic liner inside holes
• fully charged specific gravity is 1.245 to 1.300 in each cell
• In a partially discharged battery, specific gravity of each cell does not vary by more than 0.050 from the other cells
• 'at rest' battery voltage is 12.1 to 12.8 Volts
• engine cranks properly for 5 seconds with each battery alone -- battery voltage is above 9.5 Volts and steady, while cranking
• cables are in good condition
• connections clean and sealed from moisture

Wiring & Connections

• contact surfaces of mechanical connections are cleaned and coated with moisture resisting sealant before being put together
• no frayed or cracked insulation (check bilge and engine compartment)
• battery switch connections clean and sealed
• fuses have clean, tight, sealed contacts
• every electrical system is documented in diagrams or schematics and these are in one location on board Alternator, Starter & Winch Motor
• with engine running, batteries fully charged, and a 1 or 2 Amp load on system (a light turned on), voltage to batteries is 13.9 to 14.4 Volts -- voltage remains constant as more loads are turned on, up to the rated output of the alternator
• external connections clean, sealed from moisture, and positive terminals are covered
• alternator drive belt(s) tight and in good shape
• starter solenoid plunger clean and lubricated
• starter and winch motors get 9.0 Volts or more while operating

A-Sea Marine Electrical


I have found in the past that, once a battery shows a significant low electrolyte reading on a cell, you are on track for replacement and might as well bit the bullet and spend the $$$$$$$$$$.

If the reading is not too varied, an equalization will generally restore capacity if the battery has not been neglected for an extended period.

Dave