Durastart deep cycle?

fratermus

Solar Addict
Joined
Mar 19, 2021
Messages
263
Batteries with cranking amp specs or "start" in the name are rarely real deep cycle batteries. :) Manufacturers of real deep cycles will put the 20-hour Ah rating front-and-center, and reputable manufacturers will also publish duty cycle ratings for differing depths of discharge. 1000+ cycles to 50% DoD is common.

Will the Durastart meet your needs? Hard to tell since we don't know your needs are or how you would charge them. If they will be discharged lightly (20% DoD?) or just floated when you aren't around they might be fine.
 

RCinFLA

Photon Sorcerer
Joined
Jun 21, 2020
Messages
1,148
Class 27 marine dual use are usually rated 105 AH at 5 amp discharge rate, but do not attempt to pull that much as it will damage battery.

Maximum continuous load is 25 amps, which will yield about 65 AH and be dead in about 2.6 hours.
Maximum continuous charge rate is 15-20 amps. At below 85% state of charge you can push 25 amps charging.
 
Last edited:

Neumie

New Member
Joined
Apr 5, 2020
Messages
16
Batteries with cranking amp specs or "start" in the name are rarely real deep cycle batteries. :) Manufacturers of real deep cycles will put the 20-hour Ah rating front-and-center, and reputable manufacturers will also publish duty cycle ratings for differing depths of discharge. 1000+ cycles to 50% DoD is common.

Will the Durastart meet your needs? Hard to tell since we don't know your needs are or how you would charge them. If they will be discharged lightly (20% DoD?) or just floated when you aren't around they might be fine.
Thank you for weighing in. Use is intermittent and includes led lighting, radio and possibly a small fridge (0.8A) in warm months.

Other equipment:
Giandel 2kw pure sine wave inverter
Victron Bluesolar MPPT 100/30
2-345w Q-cell Q Plus oriented SE (not optimally)
 

Neumie

New Member
Joined
Apr 5, 2020
Messages
16
Class 27 marine dual use are usually rated 105 AH at 5 amp discharge rate, but do not attempt to pull that much as it will damage battery.

Maximum continuous load is 25 amps, which will yield about 65 AH and be dead in about 2.6 hours.
Maximum continuous charge rate is 15-20 amps. At below 85% state of charge you can push 25 amps charging.
Thanks. Plan to run in series to the 24v inverter. Oversized the inverter in case I wanted to run a power tool for a few minutes (rarely) and to not regret having too small in future.
 

Neumie

New Member
Joined
Apr 5, 2020
Messages
16
This is a nice kit. I think by getting starting batteries you'd greatly compromise your setup - especially with a fridge with a constant draw.
Costco has deep cycle batteries. 6V golf cart batteries (2 in series to make 12v) works too.
Yes, probably right that I shouldn’t go cheap now! Just looking to wrap things up this fall. Looking at AGM to minimize leaks.
 

RCinFLA

Photon Sorcerer
Joined
Jun 21, 2020
Messages
1,148
Thanks. Plan to run in series to the 24v inverter. Oversized the inverter in case I wanted to run a power tool for a few minutes (rarely) and to not regret having too small in future.
Just be careful of inverter no load idle current consumption.
 

Substrate

Solar Addict
Joined
Apr 28, 2021
Messages
675
Location
SoCal
The rule of thumb when there is no ah-capacity listed is to multiply the RC rating by 0.6

Thus, with an RC of 170, the AH rating based on 20 hours would be *approximately* 102ah.

The reason it is approximate is that batteries without an ah rating is an SLI or Starter-Lights-Ignition type, and not designed for long slow draws.

But with this formula, you can ballpark it if that battery is your only option.
 

Neumie

New Member
Joined
Apr 5, 2020
Messages
16
The rule of thumb when there is no ah-capacity listed is to multiply the RC rating by 0.6

Thus, with an RC of 170, the AH rating based on 20 hours would be *approximately* 102ah.

The reason it is approximate is that batteries without an ah rating is an SLI or Starter-Lights-Ignition type, and not designed for long slow draws.

But with this formula, you can ballpark it if that battery is your only option.
Thanks for pointing that out, it seems that the Durastart battery may have good capacity for the price but not be longest lasting or best choice.
 

Substrate

Solar Addict
Joined
Apr 28, 2021
Messages
675
Location
SoCal
Well, still usable, but with a cross-application caveat:

Treat them like an SLI, or starter-light-ignition battery and you may get about 4 years of life out them. Here's how:

Don't discharge more than 10% capacity each cycle. Sure, a deeper discharge won't immediately kill them, but for regular use, no more than 10 - maybe 15 percent. Basically all you are doing is emulating a long vehicle ignition start.

So, assuming a slow low-current draw application, with a 102ah capacity (napkin-calculating the RC * 0.6), then you should only draw at most about 10.2ah each cycle before it gets recharged.

AND, you don't want to "short cycle" these either. That is, it isn't wise to draw LESS than about 5% C on each discharge cycle. For 102ah, that would be 102 * .05 = 5.1ah. Short-cycling less than about 5% C on discharge, sets up some funky lead surface over time since not enough of it is discharged in an overall smooth surface manner with puny discharges.

Heh, so there you go - your application should draw at least 5.1ah, but no more than 10.2 - 15ah each cycle. A little bit limiting, but those are the the ways to get some reasonable life out of SLI batts if your cross-application is ok with that.

The good point about this is that is is much easier to recharge back that missing 10% max discharge with solar.

The bad point is that you are hefting around a lot of dead-lead: like 50ah you don't want to use unless you want to kill a starter batt in a year or less.

I ran a kitchen light off an inverter in just this manner for 4 years to prove what others taught to me. (More to disprove it, but they were right!) Sure enough, the starter batt gave up the ghost capacity wise even with my loving lab-like recharging care.
 

Neumie

New Member
Joined
Apr 5, 2020
Messages
16
Well, still usable, but with a cross-application caveat:

Treat them like an SLI, or starter-light-ignition battery and you may get about 4 years of life out them. Here's how:

Don't discharge more than 10% capacity each cycle. Sure, a deeper discharge won't immediately kill them, but for regular use, no more than 10 - maybe 15 percent. Basically all you are doing is emulating a long vehicle ignition start.

So, assuming a slow low-current draw application, with a 102ah capacity (napkin-calculating the RC * 0.6), then you should only draw at most about 10.2ah each cycle before it gets recharged.

AND, you don't want to "short cycle" these either. That is, it isn't wise to draw LESS than about 5% C on each discharge cycle. For 102ah, that would be 102 * .05 = 5.1ah. Short-cycling less than about 5% C on discharge, sets up some funky lead surface over time since not enough of it is discharged in an overall smooth surface manner with puny discharges.

Heh, so there you go - your application should draw at least 5.1ah, but no more than 10.2 - 15ah each cycle. A little bit limiting, but those are the the ways to get some reasonable life out of SLI batts if your cross-application is ok with that.

The good point about this is that is is much easier to recharge back that missing 10% max discharge with solar.

The bad point is that you are hefting around a lot of dead-lead: like 50ah you don't want to use unless you want to kill a starter batt in a year or less.

I ran a kitchen light off an inverter in just this manner for 4 years to prove what others taught to me. (More to disprove it, but they were right!) Sure enough, the starter batt gave up the ghost capacity wise even with my loving lab-like recharging care.
Thank you for the info! I passed on these. Not sure what I should go with so I’m searching some of the lead acid battery threads for info.

Honestly lights and a radio are 90% use and probably 12-15 times a year.

I decided to go solar because $45/mo for electric access fee is what is driving solar on this project.
 

Hedges

I See Electromagnetic Fields!
Joined
Mar 28, 2020
Messages
9,134
At about 5x the price, here are AGM batteries intended for the purpose.
Last page of technical manual has claimed cycle life vs. DoD.

There are other brands at lower cost, fewer cycles.

FLA golf-cart types will cost less. Premium FLA can give longer life.
Dual-use starting batteries might be OK as a buffer for direct-PV loads during the day, if drain at night (including inverter no-load) is negligible.
I went with these AGM for zero maintenance because I don't expect many cycles in a grid-backup application.
Availability may be limited in the present situation - one forum member bought Rolls Surette FLA rather than SunXtender AGM for this reason.


 

Neumie

New Member
Joined
Apr 5, 2020
Messages
16
At about 5x the price, here are AGM batteries intended for the purpose.
Last page of technical manual has claimed cycle life vs. DoD.

There are other brands at lower cost, fewer cycles.

FLA golf-cart types will cost less. Premium FLA can give longer life.
Dual-use starting batteries might be OK as a buffer for direct-PV loads during the day, if drain at night (including inverter no-load) is negligible.
I went with these AGM for zero maintenance because I don't expect many cycles in a grid-backup application.
Availability may be limited in the present situation - one forum member bought Rolls Surette FLA rather than SunXtender AGM for this reason.


[QUOTE="Hedges, post: 348131, memb...ue"]http://sunxtender.com/12_volt.php[/QUOTE]

Thanks will check these out
 

Hedges

I See Electromagnetic Fields!
Joined
Mar 28, 2020
Messages
9,134
Probably cheaper per kWh than $150 local for two dual-purpose batteries, considering cycle life.

But I didn't expect that much either. Just the batteries comes to $650, Maybe closer retailer or cheaper shipping available.
I've found truck shipping to be all over the map, like $350, $800, $8000 from different companies for one shipment of a pallet.

My last SunXtender purchase was 8x 6V 405Ah (20 kWh) for $5000 delivered. That would suggest 1/8 that much or $625 for the ones I suggested (a popular size and light enough for common carrier) but times have changed, even price w/o delivery is more.

Here's Harbor Freight, 35 Ah AGM for $75 each. Lower price, shorter cycle life. Maybe four of them to make 24V/70 Ah would work? Plan to cycle no deeper than 50% DoD, 35 Ah drawn overnight.

 

Neumie

New Member
Joined
Apr 5, 2020
Messages
16
Probably cheaper per kWh than $150 local for two dual-purpose batteries, considering cycle life.

But I didn't expect that much either. Just the batteries comes to $650, Maybe closer retailer or cheaper shipping available.
I've found truck shipping to be all over the map, like $350, $800, $8000 from different companies for one shipment of a pallet.

My last SunXtender purchase was 8x 6V 405Ah (20 kWh) for $5000 delivered. That would suggest 1/8 that much or $625 for the ones I suggested (a popular size and light enough for common carrier) but times have changed, even price w/o delivery is more.

Here's Harbor Freight, 35 Ah AGM for $75 each. Lower price, shorter cycle life. Maybe four of them to make 24V/70 Ah would work? Plan to cycle no deeper than 50% DoD, 35 Ah drawn overnight.

Thanks for the info and your time!
I ran the #s regarding a mini fridge and am not sure it’s worth the effort. The cabin is just 1/4 mile down the road from my house so using a cooler is really not an issue.

I expect I can just power off the inverter when not in use (no fridge) to avoid no load idle current.
 

Hedges

I See Electromagnetic Fields!
Joined
Mar 28, 2020
Messages
9,134
I suggest trying to use electricity while the sun is shining, avoiding loads at night. Maybe a 12V or 24V LED lamp?
PV panels, especially used, are cheaper than batteries.
A fridge, or a freezer with ice, should coast through the night. H2O as it melts will hold 32 degrees F, or brine solution can be mixed to hold a colder temperature so frozen foods stay frozen.
H2O and NaCl are cheaper than Pb or Li

My system isn't cost-effective, I only put it in because I could. Nice to run the house during occasional power failures. Daytime, PV runs A/C and everything else directly. My batteries barely last the night, would do better if I shut off the old refrigerators, etc.
 

Neumie

New Member
Joined
Apr 5, 2020
Messages
16
I suggest trying to use electricity while the sun is shining, avoiding loads at night. Maybe a 12V or 24V LED lamp?
PV panels, especially used, are cheaper than batteries.
A fridge, or a freezer with ice, should coast through the night. H2O as it melts will hold 32 degrees F, or brine solution can be mixed to hold a colder temperature so frozen foods stay frozen.
H2O and NaCl are cheaper than Pb or Li

My system isn't cost-effective, I only put it in because I could. Nice to run the house during occasional power failures. Daytime, PV runs A/C and everything else directly. My batteries barely last the night, would do better if I shut off the old refrigerators, etc.
Don’t disagree with that for most use cases (like my house with grid tied PV, no battery) but lighting is my primary use. I likely just over paneled and over inverted (not sure that’s a word) for my needs.
 

12VoltInstalls

Photon Sorcerer
Joined
Jan 18, 2021
Messages
1,980
Location
Vermont
Fwiw I use cheap grp27 deep cycle ‘Maxx’ walmartha batteries. I run a Giandel 1200W 24/7 on five of these ~$65 batteries, 1 or 2 runs of a 5-cup 600W coffeemaker. Going towards 3 years now. I expect another three.
 
Top