Battery amp Question

[budbon]

I've installed two 6V batteries on my 2250RK. They are rated 75 amp at 120 min. I am installing an Aili battery monitor. Would these batteries be considered 150 amp for 60 min.? I don't recall seeing the 120 min. designation before. Any help appreciated.

[jkwilson]

Something is wrong with your description of the specs. Do you mean 75 Amp-hours, 120 minute reserve capacity?

[Scott'n'Wendy]

Usually it's something like how many minutes with a 25 amp draw.

[budbon]

The label says "75 Amp Rating 120 Minutes"

[jkwilson]

The label says "75 Amp Rating 120 Minutes"

The only context that would make sense would be as an expression of AH at high draw. That would be 150AH assuming that’s what the statement means.

Amp-hours add with parallel connection but in a series connection they stay the same, so your two battery system is 150AH.

[budbon]

That was my thinking, but I wanted to confirm.

[huntindog]

Remember you can only use 50% of that

[jkwilson]

Remember you can only use 50% of that

I worked with batteries and chargers as an engineer for nearly 11 years and can assure you that the 50% number is a myth propagated by battery dealers and others who misunderstand the system design rule of thumb for economical long-term battery cost.

It makes sense to buy batteries that will have an average depth of discharge above 50% in your application to optimize charge time, weight and battery life, but once you have them there is nothing special about the 50% point.

[D2Reid]

I worked with batteries and chargers as an engineer for nearly 11 years and can assure you that the 50% number is a myth propagated by battery dealers and others who misunderstand the system design rule of thumb for economical long-term battery cost.

It makes sense to buy batteries that will have an average depth of discharge above 50% in your application to optimize charge time, weight and battery life, but once you have them there is nothing special about the 50% point.

Thank you John for your informed information. It's always a plus when educated and experienced engineers post on the forum. Now that I have buttered you up I would like to ask your opinion of my battery setup and if you think there is a better solution. We only boondock one or two days at a time and only in moderate temps where A/C and heater is not needed. Then we run the generator 2 hours in the morning and two hours in the evening. No inverter. Attached is the batteries data sheet. Only battery maintenance I do is check distilled water level twice a year and keep the post's clean. I have two of these. They are also subjected to single digit temps in the winter.

[Malco1]

Thank you John for your informed information. It's always a plus when educated and experienced engineers post on the forum. Now that I have buttered you up I would like to ask your opinion of my battery setup and if you think there is a better solution. We only boondock one or two days at a time and only in moderate temps where A/C and heater is not needed. Then we run the generator 2 hours in the morning and two hours in the evening. No inverter. Attached is the batteries data sheet. Only battery maintenance I do is check distilled water level twice a year and keep the post's clean. I have two of these. They are also subjected to single digit temps in the winter.

I have 2 6v golf cart batteries. With the crap converter that came with my 2020 303RLS, I check the batteries monthly. They always need water. Twice a year is not often enough unless you are not charging the batteries for extended periods of time.