Replacing house batteries

Peter_n_Margaret · Senior Member

RE: Replacing house batteries

Are We Lost · Guru

Peter_n_Margaret wrote:
Bicyclecamper wrote:
Agm's 50%.
That is an urban myth. Widely believed, but simply not true.
Cheers,
Peter

I thought it related to the specific battery design and manufacturer, and that a quality brand would support higher discharge levels than cheaper ones.

But this Victron leaflet suggests you almost triple the life of an AGM by only discharging to 70% instead of 50%. Far worse than I would have expected.

Vicron battery information

Personally I consider 50% a reasonable guideline. It's a compromise, and the more the discharge level the less life. But most manufacturers suggest that if you discharge down to 30% you are substantially affecting the life. Doing so occasionally I don't see a problem, but it would be better to plan for less discharge or accept earlier replacement.

-- Edited by Are We Lost on Sunday 28th of January 2024 04:45:17 PM

Cuppa · Guru

Are We Lost wrote:
Peter_n_Margaret wrote:
Bicyclecamper wrote:
Agm's 50%.
That is an urban myth. Widely believed, but simply not true.
Cheers,
Peter
I thought it related to the specific battery design and manufacturer, and that a quality brand would support higher discharge levels than cheaper ones.
But this Victron leaflet suggests you almost triple the life of an AGM by only discharging to 70% instead of 50%. Far worse than I would have expected.
Vicron battery information
Personally I consider 50% a reasonable guideline. It's a compromise, and the more the discharge level the less life. But most manufacturers suggest that if you discharge down to 30% you are substantially affecting the life. Doing so occasionally I don't see a problem, but it would be better to plan for less discharge or accept earlier replacement.

-- Edited by Are We Lost on Sunday 28th of January 2024 04:45:17 PM

My AGM batteries are never discharged below 70% & the previous ones lasted for 10 years, much of that time in regular use.

However that is not the whole story. What Peter_n_ Margaret alludes to is different. Consider the lifespan of a battery to be a certain amount of power supplied. If treated well & used heavily or if used lightly it will provide much the same amount of power over it's lifetime. Of course the one used heavily will not last as long, but it will provide a very similar amount of output provided that each battery is recharged on a good charger regularly & not allowed to stand uncharged & that when used the battery is discharged within the manufacturers specifications.

The reason I get 10 years from mine is because I chose to have a higher capacity , which means my needs are met without discharging below 70%. The price I pay for that is in extra weight. If I used just one, instead of three of the same batteries I would expect to get around 3 & a bit years out of each, meaning that over 10 years the three batteries whether individually or together would have had much the same lifespan. I do what I do because it suits me not to have to change batteries as frequently. If my travel style was all shorter trips I might reconsider.

Peter_n_Margaret · Senior Member

What Cuppa said.
The misleading part of this is to express battery life in years or in cycles. If you measure battery life in Ahr you get a much more useful answer as to its capability.
A battery discharged to 50% only delivers half the energy of the battery discharged to 100%, so you need twice as many for the same energy usage.
You can then choose to use those same Ahs over a shorter time or over a longer time by buying and carrying a small number of batteries or a larger number of batteries, but the number of Ahs delivered by each battery during its whole life will not change much.
Cheers,
Peter

Whenarewethere · Guru

Agree.

Look up the data sheet on battery. If you multiply the discharge percentage by the cycles, you get about the same number of total life AH.

Even then the battery is not going to fall off a cliff. You may not be able to jumpstart, but at least you can run the fridge for some time.

Blues Man · Guru

Thank you everyone for your input on House batteries .Apart from the few who had digressed ,which happens on nearly every topic on this forum

i have learned a lot and appriceate the input.

Cupie · Guru

Blues Man wrote:
Thank you everyone for your input on House batteries .Apart from the few who had digressed ,which happens on nearly every topic on this forum
i have learned a lot and appriceate the input.

You're right. There is a lot of good info on batteries provided.

Let me apologise for my digression. I do tend to do it a bit these days. I'll try to do better in future.