I am replacing my house bank, 4 6-volt golf cart batteries (wired in series->parralel)
And to be honest, I've never heard of "commission charging" until I read this excellent post by mainsail: https://www.sailnet.com/forums/3764386-post4.html
According to him: "For batteries that are to be wired series or series>parallel I wire them in parallel then charge to 7.4V and about 0.5% or less of tail current base on the 20 hour capacity."
But I'm wondering how I can do this with my current equipment (I've got a 30 amp Pro Charge Ultra onboard). How can I commission charge these batteries and ensure that they are balanced?
You can just do what they do in the UPS world and that is ensure the batteries resting open circuit voltages (24+ hours at 75-80F) are comparable to within 50mV then float them, with no ship loads, at 13.6V for about 3-5 days or more. This voltage ensures one battery is not over charged while the others play SOC catch up. Because we are using float voltages the duration is considerably longer to ensure better balanced batteries. I also hit them briefly with a EQ level voltage because even though my wholesaler/distributor has "fresh" batteries I have no way to really track how fresh
In my shop I simply short cut the long float process by simply wiring the 6V batteries in parallel and charging them to 100% SOC, while in parallel. I start by taking them to 7.1V (14.2V equivalent) and 0.00A then bump voltage to 7.4V. The end current is usually as low as 0.1A - 0.2A @ 14.8V for L-16s, GC2's etc....
Sadly far to many marine techs ignore proper commissioning of series batteries, slap them in fresh from the store, and the customer eventually pays the price. I see far too many series-wired batteries ruined by out of balance situations. Sulfation I can accept as it is just a fact of life but we don't have to tolerate out of balance batteries. Assembling the bank with properly balanced batteries helps a great deal.
Keep in mind that just because you start with balanced series batteries it does not mean they will stay that way indefinitely. Manufacturing variances, varying Coulombic efficiencies etc. can still lead to series batteries becoming out of balance. While this has been well known in industry for many years the marine market is always slow to catch on. A number of companies are now offering series-battery-balancers as well as battery monitors that offer mid point voltage monitoring. Course you can periodically check your series batteries with a volt meter too to ensure they are in balance to below 0.05V. Periodic long floats & regular EQ's will also help keep all the blocks and cells in better balance.
Here is one battery manufacturers explanation of battery balancing.
"The service life of an expensive battery bank can be substantially shortened due to state of charge unbalance:
when new cells or batteries are connected in series, they should all have the same initial state of charge. Small differences will be ironed out during absorption or equalize charging, but large differences will result in damage due to excessive gassing (caused by overcharging) of the batteries with the higher initial state of charge and sulphation (caused by undercharging) of the batteries with the lower initial state of charge."
This is from another battery manufacturer:
"Whether installing flooded, maintenance-free AGM or GEL models, battery banks should be placed on an initial balance charge using manufacturer-recommended charging parameters prior to cycling. This ensures each battery is fully charged and will cycle in balance with the rest of the bank."